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Xylenes (o-, m-, p-isomers) Ethylbenzene

OSHA Method 1002 | August 1999

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These procedures were designed and tested for internal use by OSHA personnel. Mention of any company name or commercial product does not constitute endorsement by OSHA.

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Method number: 1002
Target concentration:
  Xylenes: 100 ppm (435 mg/m3)
  Ethylbenzene: 17 ppm (73 mg/m3)
 
OSHA PEL:
  Xylenes: 100 ppm (435 mg/m3) (TWA)
  Ethylbenzene: 100 ppm (435 mg/m3) (TWA)
ACGIH TLV:
  Xylene: 100 ppm (TWA)
150 ppm (STEL/C)
  Ethylbenzene: 100 ppm (TWA)
125 ppm (STEL/C)
Procedure:Active samples are collected by drawing workplace air through coconut shell charcoal sampling tubes with personal sampling pumps. Diffusive samples are collected by exposing SKC 575-002 Passive Samplers to workplace air. Samples are extracted with carbon disulfide and analyzed by GC using a flame ionization detector.
Recommended sampling time and sampling rate:
Charcoal tubes: 240 min at 50 mL/min
SKC 575-002 Passive Samplers: 240 min
Reliable quantitation limit
(RQL) and Standard error
of estimate (SEE):
 

xylenes

ethylbenzene

RQL

SEE

RQL

SEE

(ppb)

(µg/m3)

(%)

(ppb)

(µg/m3)

(%)

charcoal tubes
SKC 575-002 Passive Samplers

20.6
194.1

89.3
842.7

5.5 
9.3*

8.3
72.8

35.9
316.0

5.4 
9.4*

*For samples when sampling site pressure and temperature are known. See Section 4.4.2 for applicable SEEs when either or both of these values are unknown.
Special requirement: Sampling site temperature and barometric pressure (station pressure) must be reported when diffusive samplers (such as SKC 575-002) are used to sample workplace air.
Status of method: Evaluated method. This method has been subjected to the established evaluation procedures of the Methods Development Team.
August 1999

Warren Hendricks

Methods Development Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Sandy UT 84070

  1. General Discussion
    1. Background
      1. History

        Xylenes is a collective term for a mixture of m-, o-, and p- isomers of xylene. These isomers differ only in placement of two methyl groups on a benzene ring. Technical and commercial grades of xylenes often contain substantial amounts of ethylbenzene (10-50%), and perhaps minor amounts of other solvents as well. Mixtures of xylenes and ethylbenzene are occasionally termed mixed xylenes.1, 2

        Most occupational exposure to xylenes also results in exposure to ethylbenzene because technical and commercial grades of xylenes are often used by industry. Therefore, test atmospheres used in this work were prepared with a commercial source of xylenes to simulate workplace environment. This source of xylenes contained 43% m-xylene, 20% o-xylene, 19% p-xylene, and 15% ethylbenzene. Xylenes target concentration in test atmospheres were approximately 100 ppm for the sum of the three isomers. These xylenes air concentrations resulted in approximately 17 ppm ethylbenzene because of its level in the commercial xylenes. Xylenes and ethylbenzene can be present in the workplace in any combination and level, and this method should be satisfactory to monitor exposures to xylenes, individual xylene isomers, and ethylbenzene. The method recommends charcoal tubes for active sampling, and SKC 575-002 Passive Samplers for diffusive sampling. Samples are extracted with carbon disulfide, and are analyzed by GC using a flame ionization detector.

        Determination of xylenes is well documented in the literature3, 4, and one may question why this work was necessary. SLTC has begun to develop sampling and analytical methods which permit the use of diffusive, as well as, active sampling. One criterion for selection of chemicals for this evaluation program is the number of sample requests. Analysis of xylenes is one of the most requested solvent determinations performed at SLTC.

      2. Toxic effects (This section is for information only and should not be taken as the basis of OSHA policy.)

        Xylenes

        There is no appreciable difference in the toxicological effects of the individual xylene isomers and those of mixed isomers. Xylenes are eye, skin, and mucous membrane irritants. They can cause narcosis at high levels. Xylenes can cause liver and kidney damage. There is little (if any) evidence for the carcinogenicity of xylenes in experimental animals. The ACGIH TLV-TWA was set at 100 ppm, and the STEL at 150 ppm, for mixed xylene isomers and for individual isomers. It was anticipated that irritant effects would be minimal, and that neither narcosis nor chronic injury would result from exposures at these levels.5

        Ethylbenzene

        Ethylbenzene is a skin and mucous membrane irritant. It has acute and possibly chronic central nervous system effects that include vertigo, unconsciousness, tremors, and changes in respiration. Animal experiments suggest that ethylbenzene causes damage to the liver, kidneys, and testes. It was the opinion of the ACGIH TLV Committee that no systemic effects would be expected at concentrations which produce skin and eye irritation. The ACGIH TLV-TWA was set at 100 ppm and the STEL at 125 ppm to prevent such irritation.6 ACGIH published in the 1998 TLVs and BEIs booklet7 a "Notice of Intended Changes" to add the A3 notation to ethylbenzene. A3 is defined as "Confirmed Animal Carcinogen with Unknown Relevance to Humans".

      3. Workplace exposure

        The main source of mixed xylenes since World War II has been reformed petroleum fractions. Earlier, xylenes were produced from coal. Coal may again become an important source as the large coal reserves in the United States are developed for petrochemical uses.8 U.S. production of xylenes in 1995 was 9.4 billion pounds, and that for ethylbenzene was 13.7 billion pounds.9

        Most mixed xylenes are used to blend gasoline. Mixed xylenes are also used in the paint and coatings industry. m-Xylene is used to produce isophthalic acid, which is used in polyesters; o-xylene is used to produce phthalic anhyride, which is used in plasticizers; p-xylene is used to produce terephthalic acid and dimethyl terephtalate, both of which are used to produce polyesters. o-Xylene and p-xylene are used in vitamin and pharmaceutical synthesis, and to produce insecticides. Ethylbenzene is used to produce styrene.10, 11

      4. Physical properties (12 unless otherwise noted)

        xylenes

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        CAS number13

        1330-20-714

        108-38-3

        95-47-6

        106-42-3

        100-41-4

        IMIS number15

        2590

        1080

        molecular weight16

        106.17

        106.17

        106.17

        106.17

        106.17

        boiling point (°C)

        137-145

        138.8

        144

        138.5

        136.19

        melting point (°C)

        -47.4

        -25

        13.2

        -95.0117

        density (°C)

        about 0.86

        0.868 (15)

        0.880 (20/4)

        0.861 (20)

        0.867 (20)

        molecular formula

        C8H10

        C8H10

        C8H10

        C8H10

        C8H10

        flash point (°F)

        81-115

        85

        115

        81

        59

        vapor pressure
            (kPa, (°C))18, 19

        1.1 (25)

        0.9 (25)

        1.2 (25)

        0.9 (20)

        Xylenes (dimethylbenzene, xylol) are soluble in alcohol and ether, but insoluble in water. Each of the mixed xylenes is a clear, colorless liquid at room temperature, however, p-xylene forms crystals at a relatively high temperature. The xylene isomers: m-xylene (1,3-dimethylbenzene), o-xylene (1,2-dimethylbenzene), and p-xylene (1,4-dimethylbenzene) are soluble in alcohol and ether; but they are insoluble in water. Ethylbenzene (phenylethane) is soluble in alcohol, benzene, carbon tetrachloride, and ether; it is but almost insoluble in water.20

        Structural formulas:

        Structural formula of m-xylne

        Structural formula of m-xylne

        Structural formula of o-xylne

        Structural formula of o-xylne

        Structural formula of p-xylne

        Structural formula of p-xylne

        Structural formula of ethyl benzene

        Structural formula of ethyl benzene

        This method was evaluated according to OSHA SLTC "Evaluation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis21. The Guidelines define analytical parameters and specify required laboratory tests, statistical calculations and acceptance criteria. The analyte concentrations throughout this method are based on the recommended sampling and analytical parameters. Air concentrations in ppm and ppb are referenced to 25 °C and 101.3 kPa (760 mmHg).

    2. Limit defining parameters
      1. Detection limit of the analytical procedure

        Table 1.2.1
        DLAP (pg per sample)

        xylenes

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        14.5

        2.1

        8.4

        14.0

        5.7

        The detection limits of the analytical procedure (DLAP) are shown in Table 1.2.1. These are the amounts of analyte that will give detector responses significantly different from the response of a reagent blank. (Section 4.1)



      2. Detection limit of the overall procedure

        Table 1.2.2.1
        DLOP for Charcoal Tubes

        analyte

        ng

        ppb

        µg/m3

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        322
        159
        239
        100
        129

        6.2
        3.0
        4.6
        1.9
        2.5

        26.8
        13.2
        19.9
        8.3
        10.8

        Charcoal tubes

        The detection limits of the overall procedure (DLOP) are shown in Table 1.2.2.1. These are the amounts of analyte spiked on the samplers that will give detector responses significantly different from the response of a sampler blank. (Section 4.2)

         

         

         

        SKC 575-002 Passive Samplers

        Table 1.2.2.2
        DLOP for SKC 575-002
        Passive Samplers

        analyte

        ng

        ppb

        µg/m3

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        847
        448
        325
        437
        315

        58.2
        31.1
        21.9
        30.1
        21.9

        252.8
        134.9
        95.0
        130.8
        94.9

        The detection limits of the overall procedure (DLOP) are shown in Table 1.2.2.2. These are the amounts of analyte spiked on the samplers that will give detector responses significantly different from the response of a sampler blank. (Section 4.2)









      3. Reliable quantitation limit

        Table 1.2.3.1
        RQL for Charcoal Tubes

        analyte

        ng

        ppb

        µg/m3

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        1072
        531
        795
        334
        431

        20.6
        10.2
        15.3
        6.4
        8.3

        89.3
        44.2
        66.2
        27.8
        35.9

        Charcoal tubes

        The reliable quantitation limits (RQL) are shown in Table 1.2.3.1. These are the amounts of analyte that will give detector responses that are considered the lower limits for precise quantitative measurements. (Section 4.2)

         

         

         

        SKC 575-002 Passive Samplers

        Table 1.2.3.2
        RQL for SKC 575-002 Passive Samplers

        analyte

        ng

        ppb

        µg/m3

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        2823
        1495
        1084
        1456
        1049

        194.1
        103.7
        73.0
        100.4
        72.8



        842.7
        450.3
        317.0
        435.9
        316.0

        The reliable quantitation limits (RQL) are shown in Table 1.2.3.2. These are the amounts of analyte that will give detector responses that are considered the lower limits for precise quantitative measurements. (Section 4.2)










      4. Instrument calibration

        Table 1.2.4
        Coefficients of Determination (r2)
        and Nondetermination (k2)

        analyte

        charcoal tubesSKC 575-002
        Pass Samplers

        r2

        k2

        r2

        k2

        m-xylene

        0.9994

        6×10-4

        0.9998

        2×10-4

        o-xylene

        0.9995

        5×10-4

        0.9998

        2×10-4

        p-xylene

        0.9994

        6×10-4

        0.9998

        2×10-4

        ethylbenzene

        0.9994

        6×10-4

        0.9998

        2×10-4

        The coefficients of determination (r2) and of nondetermination (k2) for the calibration curves are shown in Table 1.2.4. The calibrated range was 0.5 to 2 times the OSHA PEL. (Section 4.3)












      5. Precision (overall procedure)

        Table 1.2.5.1
        Precision of the Overall Procedure for Charcoal Tubes

        analyte

        precision (±%)

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        10.8
        10.7
        11.0
        11.1
        10.6

        Charcoal tubes

        The precision of the overall procedure at the 95% confidence interval for the ambient temperature 16-day storage test (at the target concentration) are shown in Table 1.2.5.1. Each precision includes an additional 5% for sampling pump variability. (Section 4.4)

        SKC 575-002 Passive Samplers

        The precision of the overall procedure at the 95% confidence interval for the ambient temperature 16-day storage tests (at the target concentration) are given in Table 1.2.5.2. They each include an additional 8.7% for sampling rate variability. There are different values given, depending on whether both, either, or neither temperature or atmospheric pressure are known at the sampling site. If the sampling-site temperature (T) is unknown, it is assumed to be 22.2 ± 15 °C (72 ± 27 °F) and a variability of ±7.7% is included. If the atmospheric pressure (P) is unknown, it is estimated from sampling-site elevation and a variability of ±3% is included. (Section 4.4)

        Table 1.2.5.2
        Precision of the Overall Procedure for SKC 575-002 Passive Samplers (±%)

        condition

        xylenes

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        both T and P known
        only T known
        only P known
        neither T nor P known

        18.2
        19.1
        23.7
        24.4

        18.3
        19.2
        23.7
        24.4

        18.1
        19.0
        23.6
        24.3

        18.3
        19.2
        23.7
        24.4

        18.4
        19.3
        23.8
        24.5

      6. Recovery

        Table 1.2.6
        Recovery (%)

        analyte

        charcoal
        tubes

        SKC 575-002
        Passive Samlers

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        99.1
        99.6
        98.5
        98.5
        100.2

        97.7
        98.2
        96.6
        97.8
        99.5

        The recoveries from samples used in 16-day ambient temperature storage tests remained above those shown in Table 1.2.6. (Section 4.5)

      7. Reproducibility

        Twelve samples (six active and six diffusive) collected from test atmospheres were submitted for analysis by SLTC. The samples were analyzed according to instructions presented in a draft copy of this method after 16 and 22 days of storage at ambient temperature for the active and diffusive samplers, respectively. No individual result deviated from its theoretical value by more than the precision reported in Section 1.2.5. (Section 4.6)

  2. Sampling procedure

    All safety practices that apply to the work area being sampled should be followed. The sampling equipment should be attached to the worker in such a manner that it will not interfere with work performance or safety.

    1. Apparatus
      1. Charcoal tubes

        Samples are collected with a personal sampling pump calibrated, with the sampler attached, to within ±5% at 50 mL/min.

        Samples are collected with 7-cm × 4-mm i.d. × 6-mm o.d. flame sealed glass sampling tubes containing two sections of coconut shell charcoal. The front section contains 100 mg and the back section contains 50 mg of charcoal. The sections are held in place and separated with glass wool and polyurethane plugs. Commercially prepared sampling tubes were purchased from SKC for this evaluation (SKC Catalog no. 226-01, Lot 2000).

      2. SKC 575-002 Passive Samplers

        Samples are collected with SKC 575-002 Passive Samplers. These samplers contain 500 mg of Anasorb 747. Lot numbers 347, 764, and 872 were used in this evaluation.

        A thermometer and a barometer are needed to determine sampling site temperature and pressure.

    2. Reagents

      None required.

    3. Technique
      1. Charcoal tubes

        Immediately before sampling, break off both ends of the flame sealed sampling tube to provide openings approximately half the internal diameter of the tube. Wear eye protection when breaking tubes. Use sampling tube holders to shield the employee from the sharp, jagged ends of the sampling tubes. All sampling tubes should be from the same lot.

        Use the smaller charcoal section of the sampling tube as a back-up and position it nearest the sampling pump. Attach the sampling tube to the sampling pump so that the tube is in an approximately vertical position with the inlet down during sampling. Position the sampling tube so that it does not impede work performance or safety.

        Draw air to be sampled directly into the tube inlet. Sampled air is not to pass through any hose or tubing before entering the sampling tube.

        Remove the sampler and seal the tube with plastic end caps after sampling for the appropriate time. Seal each sample end-to-end with an OSHA-21 form as soon as possible.

        Submit at least one blank sample with each set of samples. Handle the blank sampler in the same manner as the other samples, except draw no air through it.

        Record sample air volume in liters for each sample, and record any potential interference.

        Submit the samples to the laboratory for analysis as soon as possible after sampling. Store the samples at reduced temperature if delay is unavoidable. Ship any bulk samples separate from air samples.

      2. SKC 575-002 Passive Samplers (In general, follow the manufacturer's instructions)

        Remove the sampler from the clear package just before sampling. CAUTION - The monitor begins to sample as soon as it is removed from this package. Retain the O-ring, press-on cover, cover retainer, port plugs, and PTFE tube for later use.

        Record the start time on the sampler label, or on the Form OSHA-91A.

        Attach the sampler near the worker's breathing zone with the perforations in the sampler facing out. Assure that the area directly in front of the sampler is unobstructed throughout the sampling period.

        Remove the sampler from the worker immediately at the end of the sampling period. Attach the cover with the O-ring in place onto the sampler using the cover retainer. Inspect the O-ring to be sure it is forming a good seal around the entire circumference of the sampler. Record the stop time on the sampler label, or on the Form OSHA-91A.

        Prepare a blank sample by removing it from its clear package, and then immediately attaching a cover with the O-ring in place onto it.

        Seal each sample with an OSHA-21 form.

        Verify that sampling times are properly recorded on Form OSHA-91A for each sample. Identify blank samples on this form.

        Record sampling site temperature and atmospheric pressure (station pressure) on Form OSHA-91A.

        List any chemicals that could be considered potential interferences, especially solvents, that are in use in the sampling area.

        Submit the samples to the laboratory for analysis as soon as possible. Store the samples in a refrigerator if delay is unavoidable. Include the port plugs and PTFE tubes which will be used in the laboratory analysis.

        Ship any bulk samples separate from air samples.

    4. Sampler capacity
      1. Charcoal tubes

        The sampling capacity of SKC Lot 2000 charcoal tubes was tested by sampling from a dynamically generated test atmosphere of mixed xylenes (1027 mg/m3 or 237 ppm). Samples were collected at 50 mL/min and the relative humidity was about 78% at 21 °C. No breakthrough from the front to the back section was observed, even after sampling for ten hours. The 5% breakthrough sampling time was determined to be in excess of 600 min. (Section 4.7.1)

      2. SKC 575-002 Passive Samplers

        The sampling rate and capacity of SKC 575-002 Passive Samplers were determined by sampling from dynamically generated test atmospheres of mixed xylenes (1027 mg/m3 or 237 ppm, at 78% relative humidity and 21 °C) for increasing time intervals. Sampling rates of 13.82 mL/min for m-xylene, 14.24 mL/min for o-xylene, 13.94 mL/min for p-xylene, and 13.83 mL/min for ethylbenzene at 760 mmHg and 25 °C were obtained from these tests. Sampler capacity was never exceeded, even after sampling for ten hours. (Section 4.7.2)

    5. Extraction efficiency

      It is the responsibility of the analytical laboratory to occasionally determine or confirm extraction efficiency because the adsorbent material, reagents, or technique may be different from those presented in this method.

      1. Charcoal tubes

        Mean extraction efficiencies (EE) of the analytes from SKC Lot 2000 charcoal are presented in Table 2.5.1. The range studied was from the RQL to 2 times the 100 ppm OSHA PEL for each xylene isomer, and for ethylbenzene. The extraction efficiency was not affected by the presence of water. (Section 4.8.1)

        Table 2.5.1
        Extraction Efficiency from Charcoal (%)

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        96.3

        93.8

        96.1

        97.2

      2. SKC 575-002 Passive Samplers

        Mean extraction efficiencies (EE) of the analytes from SKC Anasorb 747 (the adsorbent in SKC 575-002 Passive Samplers) are presented in Table 2.5.2. The range studied was from the RQL to 2 times the 100 ppm OSHA PEL for each xylene isomer, and for ethylbenzene. The extraction efficiency was not affected by the presence of water. (Section 4.8.2)

        Table 2.5.2
        Extraction Efficiency form Anasorb 747 (%)

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        96.1

        89.4

        95.3

        99.1

    6. Recommended sampling time and sampling rate
      1. Charcoal tubes

        Sample for up to 4 hours at 50 mL/min when using SKC 226-01 charcoal tubes to collect long-term samples. Sample for more than 5 min at 50 mL/min to collect short-term samples.

      2. SKC 575-002 Passive Samplers

        Table 2.6.2
        Sampling Rates for SKC 575-002 Passive
        Samplers (mL/min) at 760 mmHg and 25 °C

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        13.82

        14.24

        13.94

        13.83

        Sample for up to 4 hours when using SKC 575-002 Passive Samplers to collect long-term samples. Sample for more than 5 min to collect short-term samples.

      3. The air concentration equivalent to the reliable quantitation limit becomes larger when short-term samples are collected. For example, the reliable quantitation limit for xylenes is 733 ppb (3180 µg/m3) when 0.25 L of air is sampled using charcoal tubes.
    7. Sampling interferences (Section 4.9)
      1. Charcoal tubes

        Retention

        The ability of the sampler to retain the analytes following collection was tested. The retention efficiency of all analytes for all samples was above 100.8% when three charcoal tubes containing 3 mg of mixed xylenes were used to sample 9 L of contaminant-free air having a relative humidity of 80% at 20 °C.

        Low relative humidity

        The ability of the sampler to collect and retain the analytes at low relative humidity was tested. The collection efficiency of all analytes for all samples was above 99.2% when three charcoal tubes were used to sample 12 L of air containing two times the target concentration of mixed xylenes and having a relative humidity of 5% at 20 °C.

        Low concentration

        The ability of the sampler to collect and retain the analytes at low concentration was tested. The collection efficiency of all analytes for all samples was above 94.6% when three charcoal tubes were used to sample 12 L of air containing 0.1 times the target concentration of mixed xylenes and having a relative humidity of 80% at 22 °C.

        Interference

        The ability of the sampler to collect and retain the analytes in the presence of potential sampling interferences was tested. The collection efficiency of all analytes for all samples was above 101.2% when three charcoal tubes were used to sample 12 L of air containing one times the target concentration of mixed xylenes, 365 mg/m3 toluene, 372 mg/m3 butyl acetate, and a relative humidity of 81% at 21 °C.

      2. SKC 575-002 Passive Samplers

        Reverse diffusion

        The sampling method was tested for reverse diffusion. The retention efficiency of all analytes for all samples was above 99.6% when three SKC 575-002 Passive Samplers containing 0.9 mg of mixed xylenes were used to sample contaminant-free air having a relative humidity of 80% at 20 °C for three hours.

        Low relative humidity

        The sampling method was tested to determine if the sampling rates remained constant at low relative humidity. The sampling rate of all analytes for all samples was above 97.8% of the sampling rate reported in Section 2.6.2 when three SKC 575-002 Passive Samplers were used to sample air containing two times the target concentration of mixed xylenes and having a relative humidity of 5% at 20 °C for four hours. Low humidity did not affect the sampling rates.

        Low concentration

        The sampling method was tested to determine if the sampling rates remained constant at low concentration. The sampling rate of all analytes for all samples was above 95.0% of the sampling rate reported in Section 2.6.2 when three SKC 575-002 Passive Samplers were used to sample air containing 0.1 times the target concentration of mixed xylenes and having a relative humidity of 80% at 22 °C for four hours.

        Interference

        The sampling method was tested to determine if the sampling rates remained constant in the presence of sampling interferences. The sampling rate for all analytes for all samples was above 94.3% of the sampling rate reported in Section 2.6.2 when three SKC 575-002 Passive Samplers were used to sample air containing one times the target concentration of mixed xylenes, 365 mg/m3 toluene, 372 mg/m3 butyl acetate, and a relative humidity of 81% at 21 °C for four hours.

  3. Analytical procedure

    Adhere to the rules set down in your Chemical Hygiene Plan (which is mandated by the OSHA Laboratory Standard). Avoid skin contact and inhalation of all chemicals.

    1. Apparatus
      1. A GC equipped with a flame ionization (FID) detector. A Hewlett-Packard Model 5890 Series II GC equipped with a ChemStation, an automatic sample injector, and an FID were used in this evaluation.
      2. A GC column capable of separating mixed xylenes from the extraction solvent, internal standards, and potential interferences. A J&W Scientific 60-m × 0.32-mm i.d. DB-Wax (0.5 µm df) capillary column was used in this evaluation.
      3. An electronic integrator or other suitable means of measuring GC detector response. A Waters Millennium Chromatography Manager system was used in this evaluation.
      4. Two and four-milliliter glass vials with PTFE-lined septum caps.
      5. One and two-milliliter volumetric pipets.
      6. A SKC Desorption Shaker with rack (226D-03K) was used to extract SKC 575-002 Passive Samplers in this evaluation.
    2. Reagents
      1. Xylenes, Isomers plus ethylbenzene, 98.5+%, A.C.S. reagent, Aldrich Chemical Co., Lot TR 02505LR, was used in this evaluation.
      2. m-xylene, 99+%, anhydrous, Aldrich Chemical Co., Lot 00249MQ, was used in this evaluation.
      3. o-Xylene, 98%, Spectrophotometric Grade, Aldrich Chemical Co., Lot 07946PN, was used in this evaluation.
      4. p-Xylene, 99+%, anhydrous, Aldrich Chemical Co., Lot TQ 25949MQ, was used in this evaluation.
      5. Ethylbenzene, 99.8%, anhydrous, Aldrich Chemical Co., Lot DR 03249JQ, was used in this evaluation.
      6. Carbon disulfide (CS2), 99.9+%, low benzene content, Aldrich Chemical Co., Lot 07546PN, was used in this evaluation.
      7. 1-Phenylhexane (hexylbenzene), 97%, Aldrich Chemical Co., Lot 03006PZ, was used as an internal standard for SKC 575-002 Passive Samplers in this evaluation.
      8. p-Cymene, 99%, Aldrich Chemical Co., Lot 11703TR, was used as an internal standard for charcoal tube samples in this evaluation.
      9. The extraction solvent used for this evaluation consisted of 1 µL of the appropriate internal standard per milliter of CS2. CAUTION: extraction efficiency of the internal standard from the sampling medium has an effect on sample results. This effect is especially significant for SKC 575-002 Passive Samplers. Do not substitute internal standards unless extraction efficiencies are confirmed. Both internal standards can be present in the same extraction solvent if the appropriate internal standard is used to calibrate the GC, and to calculate sample results.
      10. GC grade nitrogen, air, and hydrogen were used in this evaluation.
    3. Standard preparation
      1. Prepare stock mixed standards by weighing 1-mL aliquots of all four analytes into the same container. For example: a neat mixed standard was prepared that contained 212.7 mg/mL of m-xylene, 212.6 mg/mL of o-xylene, 213.4 mg/mL of p-xylene, and 215.3 mg/mL of ethylbenzene.
      2. Prepare working range standards for the analysis of charcoal tubes by injecting microliter quantities of the stock mixed standard into 1-mL aliquots of extraction solvent (containing 1 µL p-cymene internal standard per milliter of CS2). For example, a working range standard was prepared by injecting 6.0 µL of the stock mixed standard into extraction solvent. This standard contained 1276 µg/mL of m-xylene, 1276 µg/mL of o-xylene, 1280 µg/mL of p-xylene, and 1292 µg/mL of ethylbenzene.
      3. Prepare working range standards for the analysis of SKC 575-002 Passive Samplers by first diluting the stock mixed standard (Section 3.4.1) 1 to 4 with CS2, and then injecting microliter quantities of the diluted stock mixed standard into 2-mL aliquots of extraction solvent (containing 1 µL 1-phenylhexane internal standard per milliter of CS2). For example, a working range standard was prepared by injecting 6.0 µL of the diluted stock mixed standard into extraction solvent. This standard contained 319.0 µg/mL of m-xylene, 318.9 µg/mL of o-xylene, 320.1 µg/mL of p-xylene, and 323.0 µg/mL of ethylbenzene.
      4. Prepare a sufficient number of standards so that sample results will likely be bracketed with standards. If sample results are outside the range of prepared standards, prepare and analyze additional standards, or dilute high samples with extraction solvent and then reanalyze the diluted samples.
    4. Sample preparation
      1. Charcoal tubes

        Remove the plastic end caps from the sampling tube and carefully transfer each section of the adsorbent into separate 2-mL glass vials. Check to be certain that no charcoal is trapped in the glass-wool plug. Discard the end caps, glass tube, glass wool plug, and foam plugs.

        Add 1.0 mL of extraction solvent to each vial and immediately seal each vial with a PTFE-lined septum cap.

        Shake the vials vigorously several times during the one-hour extraction time.

      2. SKC 575-002 Passive Samplers

        Cut off the ends of the two protruding tubes of each sampler with a razor blade or a sharp knife.

        Secure the sampler by clipping it to a rail of the detachable SKC Desorption Shaker rack. Carefully and slowly add 2.0 mL of extraction solvent through the protruding tube nearest the outside edge of the sampler using a volumetric pipet. The tip of the pipet should fit just inside the sampler tube. Immediately seal the sampler tubes with the plugs supplied by the manufacturer.

        Replace the rack onto the SKC Desorption Shaker and shake the samples for one hour.

        Do not allow the extracted sample to remain in the sampler. Transfer the extracted sample into 2-mL glass vials by removing the plugs from the protruding tubes, inserting the tapered end of the PTFE tube supplied by the manufacture into the protruding tube nearest the outside edge of the sampler, and carefully pouring the solution into a 2-mL glass vial. Immediately seal the vials with PTFE-lined septum caps.

    5. Analysis
      1. GC conditions
        zone temperatures:   column 40 °C, hold 1 min, program at 4 °C/min to 140 °C, and hold as necessary to clear column
        injector220 °C
        detector220 °C
        gas flows:hydrogen (carrier)4.4 mL/min (115 kPa head pressure)
        nitrogen (makeup)  38 mL/min
        hydrogen (FID)35 mL/min
        air (FID)455 mL/min
        signal range:3
        injection volume:1 µL (20:1 split)
        column:60 m × fused silica 0.32-mm i.d. DB Wax 0.5-µm df
        Figure 3.5.1 Chromatogram of a sample desorbed from charcoal. Concentration is approximately the 100-ppm PEL for each analyte. Key: (1) CS2, (2) ethylbenzene, (3) p-xylene, (4) m-xylene, (5) o-xylene, (6) p-cymene, (7) 1-phenylhexane.

        Figure 3.5.1 Chromatogram of a sample desorbed from charcoal. Concentration is approximately the 100-ppm PEL for each analyte. Key: (1) CS2, (2) ethylbenzene, (3) p-xylene, (4) m-xylene, (5) o-xylene, (6) p-cymene, (7) 1-phenylhexane.

      2. Measure peak areas with an electronic integrator or other suitable means.
      3. An internal standard (ISTD) method is used to calibrate the instrument in terms of micrograms of analyte per sample. Prepare a calibration curve by analyzing standards, and constructing calibration curves by plotting ISTD-corrected detector response versus mass of analyte. Bracket sample results with standards.
        Figure 3.5.3.1 Calibration curve for m-xylene standards used to analyze charcoal tubes constrcted from the data in Table 4.3.1.

        Figure 3.5.3.1 Calibration curve for m-xylene standards used to analyze charcoal tubes constrcted from the data in Table 4.3.1.

        Figure 3.5.3.2 Calibration curve for m-xylene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.5.

        Figure 3.5.3.2 Calibration curve for m-xylene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.5.

        Figure 3.5.3.3 Calibration curve for o-xylene standards used to analyze charcoal tubes constructed from the data in Table 4.3.2.

        Figure 3.5.3.3 Calibration curve for o-xylene standards used to analyze charcoal tubes constructed from the data in Table 4.3.2.

        Figure 3.5.3.4 Calibration curve for o-xylene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.6.

        Figure 3.5.3.4 Calibration curve for o-xylene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.6.

        Figure 3.5.3.5 Calibration curve for p-xylene standards used to analyze charcoal tubes constructed from the data in Table 4.3.3.

        Figure 3.5.3.5 Calibration curve for p-xylene standards used to analyze charcoal tubes constructed from the data in Table 4.3.3.

        Figure 3.5.3.6 Calibration curve for p-xylene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.7.

        Figure 3.5.3.6 Calibration curve for p-xylene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.7.

        Figure 3.5.3.7 Calibration curve for ethylbenzene standards used to analyze charcoal tubes constructed from the data in Table 4.3.4.

        Figure 3.5.3.7 Calibration curve for ethylbenzene standards used to analyze charcoal tubes constructed from the data in Table 4.3.4.

        Figure 3.5.3.8 Calibration curve for ethylbenzene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.8.

        Figure 3.5.3.8 Calibration curve for ethylbenzene standards used to analyze SKC 575-002 Passive Samplers constructed from the data in Table 4.3.8.

    6. Interferences (analytical)
      1. Any chemical that produces an FID response and has a similar retention time as any of the analytes or internal standard is a potential interference. Any reported potential interferences should be considered before samples are extracted. Generally, chromatographic conditions can be altered to separate an interference from an analyte or an internal standard.
      2. The identity or purity of an analyte peak can be confirmed with additional analytical data. (Section 4.10)
    7. Calculations
      1. Charcoal tubes

        Obtain separate amounts of each analyte (m-xylene, o-xylene, p-xylene, ethylbenzene) per sample from the appropriate calibration curve in terms of micrograms per sample. These amounts are uncorrected for extraction efficiency. Be certain that the correct internal standard was used to calculate results (See Section 3.2.9). The back section of the sampling tube is analyzed primarily to determine the extent of sampler saturation. If any analyte is found on the back section, it is added to the amount found on the front section. This amount is then corrected by subtracting the total amount (if any) found on the blank. The air concentrations are then calculated using the following formulas. Calculate xylenes exposure by summing the individual xylene isomer results.

        mg/m3   =

        micrograms of analyte per sample


        liters of air sampled × extraction efficiency

         

        ppm   =  

        24.46 × mg/m3


        106.17

        Where   24.46 is the molar volume at 25 °C and 101.3 kPa (760 mmHg)
        106.17 is the molecular weight of m-xylene, o-xylene, p-xylene, and ethylbenzene
      2. SKC 575-002 Passive Samplers

        Obtain separate amounts of each analyte (m-xylene, o-xylene, p-xylene, ethylbenzene) per sample from the appropriate calibration curve in terms of micrograms per sample. These amounts are uncorrected for extraction efficiency. Be certain that the correct internal standard was used to calculate results. This amount is then corrected by subtracting the amount (if any) found on the blank.

        Table 3.7.2
        Sampling Rates for SKC 573-002 Passive
        Samplers (mL/min) at 760 mmHg and 25 °C

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        13.82

        14.24

        13.94

        13.83

        Sampling time, sampling site temperature (°C), and sampling site pressure (mmHg) is information given by the person submitting the samples. Sampling rates at 760 mmHg and 25 °C (SRNTP) are given in Table 3.7.2. These sampling rates must be converted to their equivalent (SRamb) at sampling site temperature (T) and sampling site pressure (P) by the following formula:

        SR
        amb

        =

        ( SRNTP)

        [

        T+273


        298

        ]

        1.5

        [

        760


        P

        ]

        Assume sampling site temperature is 22.2 °C if it is not given. If sampling site pressure is not given, it can be calculated by the following formula:

        P = ( 3.887 × 10-7 ) E2 - ( 2.7467 × 10-2 ) E + 760

        Where

        P is the approximate sampling site barometric pressure. E is the sampling site elevation.

        E can be estimated from airports near the sampling site location using a web site such as AirNav.com

        Liters of air sampled is calculated by multiplying the appropriate SRamb by sampling time and dividing that result by 1000.

        Air concentrations are then calculated using the following formulas. Calculate xylenes exposure by summing the individual xylene isomer results.

        mg/m3 =

        micrograms of analyte per sample


        liters of air sampled × extraction efficiency

         

        ppm =

        24.46 × mg/m3


        106.17

        Where   24.46 is the molar volume at 25 °C and 101.3 kPa (760 mmHg)
        106.17 is the molecular weight of m-xylene, o-xylene, p-xylene, and ethylbenzene
  4. Backup Data

    General background information about determination of detection limits and precision of the overall procedure is found in OSHA SLTC "Evaluation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis"22. The Guidelines define analytical parameters and specify required laboratory tests, statistical calculations and acceptance criteria.

    1. Detection limit of the analytical procedure (DLAP)

      The DLAP is measured as the mass of analyte introduced into the chromatographic column. Ten standards were prepared in equal descending increments of analyte, such that the highest standard produced a peak approximately 10 times the response of a reagent blank. These standards, and a reagent blank, were analyzed using the recommended analytical parameters (1-µL injection with a 20:1 split), and the data obtained were used to determine the required parameters (A and SEEDL) for the calculation of the DLAP. Xylenes DLOP was calculated by summing masses and areas for individual xylene isomers. The extraction solvent contained a contaminant that eluted at the same time as p-xylene. The amount of this contaminant was small, but sufficient to cause a higher DLAP for p-xylene than for the other analytes.

      Table 4.1
      Detection Limit of the
      Analytical Procedure

      analyte

      DLAP (pg)

      xylenes
      m-xylene
      o-xylene
      p-xylene
      ethylbenzene

      14.5 
      2.1
      8.4
      14.0 
      5.7

      Table 4.1.1
      DLAP for Xylenes

      concn
      (ng/mL)

      mass on
      column (pg)

      area counts
      (µV-s)

      0
      512
      1026
      1538
      2052
      2564
      3076
      3590
      4102
      4616
      5128

      0
      25.6
      51.3
      76.9
      102.6
      128.2
      153.8
      179.5
      205.1
      230.8
      256.4

      150
      196
      284
      369
      395
      482
      566
      636
      697
      769
      853

      Figure 4.1.1 Plot of data used to determine DLAP for xylenes.

      Figure 4.1.1 Plot of data used to determine DLAP for xylenes.

      Table 4.1.2
      DLAP for m-Xylene

      concn
      (ng/mL)

      mass on
      column (pg)

      area counts
      (µV-s)

      0
      170
      342
      512
      684
      854
      1024
      1196
      1366
      1538
      1708

      0
      8.5
      17.1
      25.6
      34.2
      42.7
      51.2
      59.8
      68.3
      76.9
      85.4

      8
      32
      52
      80
      102
      123
      145
      168
      196
      215
      240

      Figure 4.1.2 Plot of data used to determine DLAP for m-xylene.

      Figure 4.1.2 Plot of data used to determine DLAP for m-xylene.

      Table 4.1.3
      DLAP for o-Xylene

      concn
      (ng/mL)

      mass on
      column (pg)

      area counts
      (µV-s)

      0
      172
      342
      514
      684
      856
      1028
      1198
      1370
      1540
      1712

      0
      8.6
      17.1
      25.7
      34.2
      42.8
      51.4
      59.9
      68.5
      77.0
      85.6

      0
      21
      37
      81
      85
      120
      143
      171
      174
      231
      235

      Figure 4.1.3 Plot of data used to determine DLAP for o-xylene.

      Figure 4.1.3 Plot of data used to determine DLAP for o-xylene.

      Table 4.1.4
      DLAP for p-Xylene

      concn
      (ng/mL)

      mass on
      column (pg)

      area counts
      (µV-s)

      0
      170
      342
      512
      684
      854
      1024
      1196
      1366
      1538
      1708

      0
      8.5
      17.1
      25.6
      34.2
      42.7
      51.2
      59.8
      68.3
      76.9
      85.4

      142
      143
      195
      208
      208
      239
      278
      297
      327
      323
      368

      Figure 4.1.4 Plot of data used to determine DLAP for p-xylene.

      Figure 4.1.4 Plot of data used to determine DLAP for p-xylene.

      Table 4.1.5
      DLAP for Ethylbenzene

      concn
      (ng/mL)

      mass on
      column (pg)

      area counts
      (µV-s)

      0
      174
      346
      520
      692
      866
      1040
      1212
      1386
      1558
      1732

      0
      8.7
      17.3
      26.0
      34.6
      43.3
      52.0
      60.6
      69.3
      77.9
      86.6

      0
      26
      38
      66
      92
      120
      146
      165
      177
      206
      233

      Figure 4.1.5 Plot of data used to determine DLAP for ethylbenzene.

      Figure 4.1.5 Plot of data used to determine DLAP for ethylbenzene.

    2. Detection limit of the overall procedure (DLOP) and reliable quantitation limit (RQL)

      The DLOP is measured as mass per sample and expressed as equivalent air concentrations, based on the recommended sampling parameters. Ten 100-mg portions of SKC Lot 2000 charcoal, and ten 500-mg portions of SKC Anasorb 747, (representing SKC 575-002 Passive Samplers) were spiked with equal descending increments of analyte, such that the highest sampler loading would produce a peak approximately 10 times the response for a sample blank. These spiked samples, and sample blanks were analyzed with the recommended analytical parameters, and the data obtained used to calculate the required parameters (A and SEEDL) for the calculation of DLOP and RQL. Xylenes DLOP and RQL were calculated by summing masses and areas for individual xylene isomers. Sample air volume and extraction efficiency for xylenes is the mean of those for individual xylene isomers. Table 4.2 is a summary of DLOP results and is presented for quick reference.

      Table 4.2
      Detection Limit of the Overall Procedure Summary

      analyte

      charcoal
      tubes

      SKC 575-002
      Passive Samplers

      ng

      µg/m3

      ppb

      ng

      µg/m3

      ppb

      xylenes
      m-xylene
      o-xylene
      p-xylene
      ethylbenzene

      322
      159
      239
      100
      129

      26.8
      13.2
      19.9
        8.3
      10.8

      6.2
      3.0
      4.6
      1.9
      2.5

      847
      448
      325
      437
      315

      252.8
      134.9
      95.0
      130.8
      94.9

      58.2
      31.1
      21.9
      30.1
      21.9

      Table 4.2.1
      DLOP and RQL
      for Xylenes from Charcoal Tubes

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      513
      1025
      1538
      2051
      2563
      3076
      3590
      4101
      4614
      5128

      139
      238
      272
      357
      423
      485
      524
      624
      691
      763
      835

      Figure 4.2.1 Plot of data used to determine DLOP and RQL for xylenes.

      Figure 4.2.1 Plot of data used to determine DLOP and RQL for xylenes.

      Table 4.2.2
      DLOP and RQL for Xylenes
      from SKC 575-002 Passive Samplers

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      1025
      2051
      3076
      4101
      5128
      6152
      7179
      8204
      9228
      10255

      136
      247
      278
      334
      452
      497
      588
      615
      696
      769
      844

      Figure 4.2.2 Plot of data used to determine DLOP and RQL for xylenes.

      Figure 4.2.2 Plot of data used to determine DLOP and RQL for xylenes.

      Table 4.2.3
      DLOP and RQL
      for m-Xylene from Charcoal Tubes

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      171
      341
      512
      683
      853
      1024
      1195
      1365
      1536
      1707

      0
      39
      54
      74
      109
      116
      134
      168
      200
      215
      239

      Figure 4.2.3 Plot of data used to determine DLOP and RQL for m-xylene.

      Figure 4.2.3 Plot of data used to determine DLOP and RQL for m-xylene.

      Table 4.2.4
      DLOP and RQL for m-Xylene
      from SKC 575-002 Passive Samplers

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      341
      683
      1024
      1365
      1707
      2048
      2390
      2731
      3072
      3414

      0
      46
      56
      61
      110
      116
      158
      175
      194
      226
      237

      Figure 4.2.4 Plot of data used to determine DLOP and RQL for m-xylene.

      Figure 4.2.4 Plot of data used to determine DLOP and RQL for m-xylene.

      Table 4.2.5
      DLOP and RQL
      for o-Xylene from Charcoal Tubes

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      171
      343
      514
      685
      857
      1028
      1200
      1371
      1542
      1714

      0
      31
      39
      70
      85
      121
      115
      161
      168
      210
      239

      Figure 4.2.5 Plot of data used to determine DLOP and RQL for o-xylene.

      Figure 4.2.5 Plot of data used to determine DLOP and RQL for o-xylene.

      Table 4.2.6
      DLOP and RQL for o-Xylene from
      SKC 575-002 Passive Samplers

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      343
      685
      1028
      1371
      1714
      2056
      2399
      2742
      3084
      3427

      0
      29
      35
      69
      96
      112
      126
      147
      164
      190
      223

      Figure 4.2.6 Plot of data used to determine DLOP and RQL for o-xylene.

      Figure 4.2.6 Plot of data used to determine DLOP and RQL for o-xylene.

      Table 4.2.7
      DLOP and RQL
      for p-Xylene from Charcoal Tubes

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      171
      341
      512
      683
      853
      1024
      1195
      1365
      1536
      1707

      139
      168
      179
      213
      229
      248
      275
      295
      323
      338
      357

      Figure 4.2.7 Plot of data used to determine DLOP and RQL for p-xylene.

      Figure 4.2.7 Plot of data used to determine DLOP and RQL for p-xylene.

      Table 4.2.8
      DLOP and RQL for p-Xylene from
      SKC 575-002 Passive Samplers

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      341
      683
      1024
      1365
      1707
      2048
      2390
      2731
      3072
      3414

      136
      172
      187
      204
      246
      269
      304
      293
      338
      353
      384

      Figure 4.2.8 Plot of data used to determine DLOP and RQL for p-xylene.

      Figure 4.2.8 Plot of data used to determine DLOP and RQL for p-xylene.

      Table 4.2.9
      DLOP and RQL
      for Ethylbenzene from Charcoal Tubes

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      173
      346
      519
      692
      865
      1038
      1211
      1384
      1558
      1731

      0
      35
      44
      76
      88
      118
      136
      153
      182
      198
      231

      Figure 4.2.9 Plot of data used to determine DLOP and RQL for ethylbenzene.

      Figure 4.2.9 Plot of data used to determine DLOP and RQL for ethylbenzene.

      Table 4.2.10
      DLOP and RQL for Ethylbenzene from
      SKC 575-002 Passive Samplers

      mass per sample
      (ng)

      area counts
      (µV-s)

      0
      346
      692
      1038
      1384
      1731
      2077
      2423
      2769
      3115
      3461

      0
      25
      52
      71
      90
      111
      143
      153
      186
      212
      251

      Figure 4.2.10 Plot of data used to determine DLOP and RQL for ethylbenzene.

      Figure 4.2.10 Plot of data used to determine DLOP and RQL for ethylbenzene.

      The RQL is considered the lower limit for precise quantitative measurements. It is determined from the regression line parameters obtained for calculation of DLOP, providing the extraction efficiency (EE) is 100 ± 25% at the RQL.

      Table 4.2.11
      Reliable Quantitation Limits


      analyte

      charcoal
      tubes

      SKC 575-002
      Passive Samplers

      ng

      µg/m3

      ppb

      EE(%)

      ng

      µg/m3

      ppb

      EE(%)

      xylenes
      m-xylenes
      o-xylenes
      p-xylenes
      ethylbenzene

      1072
      531
      795
      334
      431

      89.3
      44.2
      66.2
      27.8
      35.9

      20.6
      10.2
      15.3
      6.4
      8.3

      98.4
      98.9
      95.6
      99.9
      99.4

      2823
      1495
      1084
      1456
      1049

      842.7
      450.3
      317.0
      435.9
      316.0

      194.1
      103.7
      73.0
      100.4
      72.8

      93.6
      96.4
      84.9
      95.6
      97.6

      Figure 4.2.11 Chromatogram of a sample containing masses of analytes approximating the RQLs extracted from a charcoal tube. Key: (1) ethylbenzene, (2) p-xylene, (3) m-xylene, (4) o-xylene.

      Figure 4.2.11 Chromatogram of a sample containing masses of analytes approximating the RQLs extracted from a charcoal tube. Key: (1) ethylbenzene, (2) p-xylene, (3) m-xylene, (4) o-xylene.

      Figure 4.2.12 Chromatogram of a sample containing masses of analytes approximating the RQLs extracted from a SKC 575-002 Passive Sampler. Key: (1) ethylbenzene, (2) p-xylene, (3) m-xylene, (4) o-xylene.

      Figure 4.2.12 Chromatogram of a sample containing masses of analytes approximating the RQLs extracted from a SKC 575-002 Passive Sampler. Key: (1) ethylbenzene, (2) p-xylene, (3) m-xylene, (4) o-xylene.

    3. Instrument calibration

      Table 4.3
      Coefficient of Determination (r2)
      and of Nondetermination (k2)

      analyte

      charcoal
      tubes

      SKC 575-002
      Pass Sampers

      r2

      k2

      r2

      k2

      m-xylene

      0.9994

      6 × 10-4

      0.9998

      2 × 10-4

      o-xylene

      0.9995

      5 × 10-4

      0.9998

      2 × 10-4

      p-xylene

      0.9994

      6 × 10-4

      0.9998

      2 × 10-4

      ethylbenzene

      0.9994

      6 × 10-4

      0.9998

      2 × 10-4

      The instrument was calibrated for xylene isomers and ethylbenzene over a range of from 0.5 to 2 times the 100 ppm PEL for each analyte. Calibration was performed at concentrations appropriate for both active and diffusive samplers. Calibration curves were constructed from the tabulated data and are shown in Section 3.5.3. Coefficients of determination (r2) and of nondetermination (k2) are shown in Table 4.3.

       

       

       

       

       

      Table 4.3.1
      Instrument Response to
      m-Xylene for Charcoal Tubes

      × OSHA PEL
      (µg/sample)

      0.5×
      2568

      0.75×
      3852


      5136

      1.5×
      7704


      10272

      area (µV-s)

      164794
      164754
      164983
      164992
      165047
      165182

      269791
      269445
      269434
      269351
      269191
      268965

      375905
      375908
      376753
      376901
      375901
      375624

      593689
      592710
      593187
      592430
      591644
      593035

      783759
      784944
      786776
      784541
      784130
      783251

      Table 4.3.2
      Instrument Response to
      o-Xylene for Charcoal Tube

      × OSHA PEL
      (µg/sample)

      0.5×
      2590

      0.75×
      3884


      5179

      1.5×
      7769


      10358

      area (µV-s)

      167753
      167760
      167934
      167902
      167961
      168094

      274897
      274708
      274660
      274497
      274406
      274212

      383480
      383480
      384309
      384433
      383472
      383231

      606183
      605143
      605576
      605029
      604460
      605477

      801612
      802500
      804231
      802144
      801744
      800999

      Table 4.3.3
      Instrument Response to
      p-Xylene for Charcoal Tubes

      × OSHA PEL
      (µg/sample)

      0.5×
      2559

      0.75×
      3839


      5118

      1.5×
      7678


      10237

      area (µV-s)

      164552
      164539
      164734
      164768
      164807
      164923

      268846
      268538
      268527
      268449
      268265
      268051

      374277
      374271
      375116
      375271
      374253
      374021

      590454
      589602
      590062
      589284
      588468
      589848

      779090
      780366
      782170
      779941
      779572
      778654

      Table 4.3.4
      Instrument Response to
      Ethylbenzene for Charcoal Tubes

      × OSHA PEL
      (µg/sample)

      0.5×
      2608

      0.75×
      3912


      5216

      1.5×
      7824


      10432

      area (µV-s)

      164275
      164292
      164473
      164518
      164581
      164665

      269560
      269199
      269224
      269089
      268885
      268679

      375888
      375846
      376676
      376857
      375780
      375508

      593883
      593063
      593502
      592685
      591749
      593173

      783759
      785278
      787146
      784787
      784405
      783391

      Table 4.3.5
      Instrument Response to m-Xylene
      for SKC 575-002 Passive Samplers

      × OSHA PEL
      (µg/sample)

      0.5×
      749

      0.75×
      1177


      1455

      1.5×
      2140


      2889

      area (µV-s)

      29838
      29955
      29857
      29887
      29836
      29842

      47626
      47689
      47832
      47847
      47796
      47774

      58960
      59183
      59046
      59397
      59004
      59284

      86200
      86119
      86097
      85956
      85933
      85854

      117788
      117903
      117765
      118128
      117561
      117760

      Table 4.3.6
      Instrument Response to o-Xylene
      for SKC 575-002 Passive Samplers

      × OSHA PEL
      (µg/sample)

      0.5×
      755

      0.75×
      1187


      1467

      1.5×
      2158


      2913

      area (µV-s)

      30464
      30579
      30508
      30521
      30486
      30483

      48643
      48697
      48848
      48880
      48780
      48795

      60209
      60434
      60309
      60692
      60248
      60531

      88024
      87973
      87915
      87801
      87757
      87695

      120324
      120516
      120317
      120670
      120081
      120298

      Table 4.3.7
      Instrument Response to p-Xylene
      for SKC 575-002 Passive Samplers

      × OSHA PEL
      (µg/sample)

      0.5×
      746

      0.75×
      1173


      1450

      1.5×
      2133


      2879

      area (µV-s)

      29754
      29867
      29774
      29817
      29771
      29772

      47433
      47507
      47680
      47672
      47625
      47597

      58707
      58961
      58809
      59157
      58765
      59041

      85808
      85716
      85692
      85590
      85545
      85468

      117229
      117319
      117199
      117578
      116981
      117192

      Table 4.3.8
      Instrument Response to Ethylbenzene
      for SKC 575-002 Passive Samplers

      × OSHA PEL
      (µg/sample)

      0.5×
      761

      0.75×
      1195


      1478

      1.5×
      2173


      2934

      area (µV-s)

      29797
      29920
      29824
      29882
      29834
      29816

      47592
      47668
      47822
      47826
      47764
      47738

      58904
      59197
      59043
      59390
      58958
      59261

      86193
      86089
      86057
      85970
      85917
      85830

      117774
      117857
      117737
      118148
      117530
      117767

    4. Precision (overall procedure)
      1. Charcoal tubes

        Table 4.4.1
        SEEs and Precisions of the
        Overall Procedure for Charcoal Tubes

        analyte

        SEE(%)

        precision(±%)

        xylenes
        m-xylene
        o-xylene
        p-xylene
        ethylbenzene

        5.50
        5.45
        5.59
        5.67
        5.41

        10.8
        10.7
        11.0
        11.1
        10.6

        The precision at the 95% confidence level is obtained by multiplying the SEE by 1.96 (the z-statistic from the standard normal distribution at the 95% confidence level). In Section 4.5, 95% confidence intervals are drawn about their respective regression lines in the storage graph figures. The precisions of the overall procedure were obtained from the ambient temperature storage tests and are shown in Table 4.4.1.

      2. SKC 575-002 Passive Samplers

        The precision at the 95% confidence level is obtained by multiplying the SEE by 1.96 (the z-statistic from the standard normal distribution at the 95% confidence level). In Section 4.5, 95% confidence intervals are drawn about their respective regression lines in the storage graph figures. Each precision includes an additional 8.7% for sampling rate variability. There are different values given, depending on whether both, either, or neither temperature or atmospheric pressure are known at the sampling site. If the sampling-site temperature (T) is unknown, it is assumed to be 22.2 ± 15 °C (72 ± 27 °F) and a variability of ±7.7% is included. If the atmospheric pressure (P) is unknown, it is estimated from sampling-site elevation and a variability of ±3% is included. The precisions of the overall procedure are shown in Table 4.4.2.

        Table 4.4.2
        SEEs and Precisions of the Overall Procedure for SKC 575-002 Passive Samplers

        condition

        xylenes

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        SEE
        (%)

        precision
        (±%)

        SEE
        (%)

        precision
        (±%)

        SEE
        (%)

        precision
        (±%)

        SEE
        (%)

        precision
        (±%)

        SEE
        (%)

        precision
        (±%)

        both T and P known
        only T known
        only P known
        neither T nor P known

        9.29
        9.76
        12.07
        12.43

        18.2
        19.1
        23.7
        24.4

        9.32
        9.79
        12.09
        12.46

        18.3
        19.2
        23.7
        24.4

        9.24
        9.71
        12.03
        12.40

        18.1
        19.0
        23.6
        24.3

        9.33
        9.80
        12.10
        12.46

        18.3
        19.2
        23.7
        24.4

        9.39
        9.86
        12.14
        12.51
         

        18.4
        19.3
        23.8
        24.5

    5. Storage tests
      1. Charcoal tubes

        Storage stability samples were prepared by sampling (at 50 mL/min for four hours) dynamically generated test atmospheres of mixed xylenes with SKC 226-01 sampling tubes. These samples were collected simultaneously along with diffusive samples. The concentrations of the test atmospheres were 207 mg/m3 (48 ppm) for m-xylene, 96 mg/m3 (22 ppm) for o-xylene, 90 mg/m3 (21 ppm) for p-xylene, and 73 mg/m3 (17 ppm) for ethylbenzene at 83% relative humidity and 20 °C. Xylenes concentration was the sum of the individual isomers and was 393 mg/m3 (91 ppm). These air concentrations were approximately one times the target concentration for xylenes and were in the same proportions as were the analytes in the mixed xylenes used to generate the test atmospheres. Xylenes results were calculated from summed individual isomers results. Sample results are corrected for extraction efficiency.

        Table 4.5.1.1
        Storage Tests for Xylenes

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        97.0
        101.1
        102.2
        96.5
        101.6
        99.8

        98.9
        102.5
        97.4
        97.9
        96.7
        97.0

        96.8
        100.3
        103.1
        99.2
        97.9
        101.1

        97.0
        103.1
        96.3
        100.4
        101.3
        101.7

        98.9
        101.3
        100.2
        98.2
        99.4
        93.8

        96.8
        100.3
        100.8
        98.8
        100.2
        102.0

        Table 4.5.1.2
        Storage Tests for m-Xylene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        97.3
        101.4
        102.5
        97.0
        101.9
        100.6

        99.1
        102.8
        97.8
        98.3
        97.2
        98.7

        97.2
        100.6
        103.3
        99.5
        99.8
        101.9

        97.3
        103.3
        97.6
        100.7
        101.6
        102.0

        99.1
        101.6
        100.7
        98.7
        99.7
        93.7

        97.2
        100.6
        101.2
        99.2
        100.5
        102.3

        Table 4.5.1.3
        Storage Tests for o-Xylene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        96.1
        100.7
        101.5
        95.2
        101.0
        99.5

        98.4
        101.8
        96.3
        97.0
        95.6
        95.8

        95.9
        99.5
        102.6
        98.4
        98.5
        100.6

        96.1
        102.5
        95.6
        99.6
        100.6
        101.1

        98.4
        100.7
        99.2
        96.9
        98.8
        94.4

        95.9
        99.6
        100.0
        97.7
        99.5
        101.4

        Table 4.5.1.4
        Storage Tests for p-Xylene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        97.0
        101.1
        102.1
        96.6
        101.6
        99.6

        98.8
        102.5
        97.5
        98.0
        96.8
        97.0

        96.8
        100.3
        103.0
        99.2
        93.1
        101.1

        97.0
        103.0
        96.4
        100.4
        101.3
        101.7

        98.8
        101.3
        100.3
        98.3
        99.4
        93.5

        96.8
        100.3
        100.9
        98.9
        100.2
        101.9

        Table 4.5.1.5
        Storage Tests for Ethylbenzene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        98.2
        102.1
        103.1
        98.2
        102.5
        100.0

        99.7
        103.6
        99.0
        99.3
        98.6
        97.5

        98.3
        101.6
        103.9
        100.3
        100.8
        101.4

        98.2
        104.0
        97.5
        101.6
        102.3
        102.6

        99.7
        102.3
        101.9
        100.1
        100.6
        93.5

        98.3
        101.3
        102.2
        100.3
        101.2
        103.0

        Figure 4.5.1.1 Ambient storage test for xylenes collected on charcoal tubes.

        Figure 4.5.1.1 Ambient storage test for xylenes collected on charcoal tubes.

        Figure 4.5.1.2 Regrigerated storage test for xylenes collected on charcoal tubes.

        Figure 4.5.1.2 Regrigerated storage test for xylenes collected on charcoal tubes.

        Figure 4.5.1.3 Ambient storage test for m-xylene collected on charcoal tubes.

        Figure 4.5.1.3 Ambient storage test for m-xylene collected on charcoal tubes.

        Figure 4.5.1.4 Regrigerated storage test for m-xylene collected on charcoal tubes.

        Figure 4.5.1.4 Regrigerated storage test for m-xylene collected on charcoal tubes.

        Figure 4.5.1.5 Ambient storage test for o-xylene collected on charcoal tubes.

        Figure 4.5.1.5 Ambient storage test for o-xylene collected on charcoal tubes.

        Figure 4.5.1.6 Regrigerated storage test for o-xylene collected on charcoal tubes.

        Figure 4.5.1.6 Regrigerated storage test for o-xylene collected on charcoal tubes.

        Figure 4.5.1.7 Ambient storage test for p-xylene collected on charcoal tubes.

        Figure 4.5.1.7 Ambient storage test for p-xylene collected on charcoal tubes.

        Figure 4.5.1.8 Regrigerated storage test for p-xylene collected on charcoal tubes.

        Figure 4.5.1.8 Regrigerated storage test for p-xylene collected on charcoal tubes.

        Figure 4.5.1.9 Ambient storage test for ethylbenzene collected on charcoal tubes.

        Figure 4.5.1.9 Ambient storage test for ethylbenzene collected on charcoal tubes.

        Figure 4.5.1.10 Regrigerated storage test for ethylbenzene collected on charcoal tubes.

        Figure 4.5.1.10 Regrigerated storage test for ethylbenzene collected on charcoal tubes.

      2. SKC 575-002 Passive Samplers

        Storage stability samples were prepared by sampling dynamically generated test atmospheres of mixed xylenes with SKC 575-002 Passive Samplers. The face velocity of the test atmosphere was about 0.4m/s past the diffusive samplers. The samplers were orientated parallel to the flow direction. These samples were collected for four hours simultaneously along with active samples under conditions described in Section 4.5.1. Xylenes results were calculated from summed isomers results. Sample results are corrected for extraction efficiency.

        Table 4.5.2.1
        Storage Tests for Xylenes

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        96.6
        101.0
        104.6
        101.1
        98.0
        97.4

        97.3
        101.6
        93.5
        102.8
        92.9
        98.9

        97.1
        102.5
        99.7
        97.2
        99.7
        94.4

        96.6
        101.2
        100.9
        100.5
        100.6
        102.4

        97.3
        102.5
        100.0
        99.5
        99.4
        100.9

        97.1
        101.4
        98.6
        100.7
        100.5
        97.9

        Table 4.5.2.2
        Storage Tests for m-Xylene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        96.8
        101.5
        105.1
        101.6
        98.4
        97.9

        97.5
        102.2
        93.9
        103.3
        93.3
        99.4

        97.4
        103.1
        100.2
        97.6
        100.1
        94.9

        96.8
        101.8
        101.3
        100.9
        101.1
        102.9

        97.5
        103.1
        100.4
        100.0
        99.9
        101.4

        97.4
        101.9
        99.0
        101.1
        101.0
        98.4

        Table 4.5.2.3
        Storage Tests for o-Xylene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        96.2
        99.7
        103.4
        99.9
        96.9
        96.2

        96.8
        100.4
        92.4
        101.5
        92.1
        97.7

        96.6
        101.1
        98.6
        96.1
        99.0
        93.1

        96.2
        99.7
        99.9
        99.4
        99.3
        101.1

        96.8
        101.1
        98.8
        98.4
        98.2
        99.6

        96.6
        100.4
        97.3
        99.6
        99.3
        96.7

        Table 4.5.2.4
        Storage Tests for p-Xylene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        96.6
        101.2
        104.8
        101.3
        98.1
        97.5

        97.2
        101.8
        93.6
        103.1
        92.9
        99.1

        97.0
        102.8
        99.9
        97.3
        99.6
        94.5

        99.6
        101.5
        101.0
        100.6
        100.7
        102.5

        97.2
        102.8
        100.2
        99.7
        99.5
        101.0

        97.0
        101.5
        98.7
        100.8
        100.7
        98.0

        Table 4.5.2.5
        Storage Tests for Ethylbenzene

        time
        (days)

        ambient storage
        recovery (%)

        refrigerated storage
        recovery (%)

        0
        3
        7
        10
        14
        16

        97.4
        103.0
        106.5
        103.0
        99.6
        99.1

        98.1
        103.6
        95.2
        104.7
        94.3
        100.8

        98.0
        104.4
        101.5
        98.8
        101.0
        96.1

        97.4
        103.2
        102.6
        102.2
        102.7
        104.4

        98.1
        104.4
        101.7
        101.3
        101.2
        102.9

        98.0
        103.5
        100.4
        102.4
        102.4
        99.7

        Figure 4.5.2.1 Ambient storage test for xylenes collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.1 Ambient storage test for xylenes collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.2 Regrigerated storage test for xylenes collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.2 Regrigerated storage test for xylenes collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.3 Ambient storage test for m-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.3 Ambient storage test for m-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.4 Regrigerated storage test for m-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.4 Regrigerated storage test for m-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.5 Ambient storage test for o-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.5 Ambient storage test for o-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.6 Regrigerated storage test for o-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.6 Regrigerated storage test for o-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.7 Ambient storage test for p-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.7 Ambient storage test for p-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.8 Regrigerated storage test for p-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.8 Regrigerated storage test for p-xylene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.9 Ambient storage test for ethylbenzene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.9 Ambient storage test for ethylbenzene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.10 Regrigerated storage test for ethylbenzene collected on SKC 575-002 Passive Samplers.

        Figure 4.5.2.10 Regrigerated storage test for ethylbenzene collected on SKC 575-002 Passive Samplers.

    6. Reproducibility

      Twelve samples (six charcoal tubes and six SKC 575-002 Passive Samplers) were collected from controlled test atmospheres similar to that used to collect storage stability samples. The samples were submitted to SLTC for analysis. The charcoal tube samples were analyzed after 16 days of storage at ambient temperature, and the SKC 575-002 Passive Samplers after 22 days of storage at ambient temperature. Sample results were corrected for extraction efficiency. No sample result had a deviation greater than the precision of the overall procedure reported in Section 4.4. Xylenes results were calculated by summing results for individual isomers.

      Table 4.6.1
      Reproducibility Data for Xylene Isomers on Charcoal Tubes

      m-xylene

      o-xylene

      p-xylene

      theo

      reported

      recovery

      deviation

      theo

      reported

      recovery

      deviation

      theo

      reported

      recovery

      deviation

      µg/samp

      µg/samp

      (%)

      (%)

      µg/samp

      µg/samp

      (%)

      (%)

      µg/samp

      µg/samp

      (%)

      (%)

      2555
      2595
      2623
      2557
      2564
      2623

      2552
      2593
      2427
      2580
      2593
      2610

      99.9
      99.9
      92.5
      100.9
      101.1
      95.5

      -0.1
      -0.1
      -7.5
      0.9
      1.1
      -0.5

      1189
      1207
      1221
      1190
      1193
      1221

      1245
      1266
      1158
      1262
      1263
      1275

      104.7
      104.9
      94.8
      106.1
      105.9
      104.4

      4.7
      4.9
      -5.2
      6.1
      5.9
      4.4

      1112
      1129
      1142
      1129
      1116
      1142

      1140
      1158
      1082
      1152
      1159
      1166

      102.5
      102.6
      94.7
      102.0
      103.9
      102.1

      2.5
      2.6
      -5.3
      2.0
      3.9
      2.1

      Table 4.6.2
      Reproducibility Data for Xylenes and Ethylbenzene on Charcoal Tubes

      xylenes

      |
      |
      |

      ethylbenzene

      theo
      µg/samp

      reported
      µg/samp

      recovery
      (%)

      deviation
      (%)

      theo
      µg/samp

      reported
      µg/samp

      recovery
      (%)

      deviation
      (%)

      4856
      4931
      4986
      4876
      4873
      4986

      4937
      5017
      4667
      4994
      5014
      5051

      101.7
      101.7
      93.6
      102.4
      102.9
      101.3

      1.7
      1.7
      -6.4 
      2.4
      2.9
      1.3

      |
      |
      |
      |
      |
      |

      904.8
      918.9
      929.0
      905.6
      911.8
      929.0

      929.4
      944.2
      895.4
      939.1
      945.6
      944.3

      102.7
      102.8
      96.4
      103.7
      103.7
      101.6

      2.7
      2.8
      -3.6 
      3.7
      3.7
      1.6

      Table 4.6.3
      Reproducibility Data for Xylene Isomers on SKC 575-002
      Passive Samplers

      m-xylene

      o-xylene

      p-xylene

      theo

      reported

      recovery

      deviation

      theo

      reported

      recovery

      deviation

      theo

      reported

      recovery

      deviation

      µg/samp

      µg/samp

      (%)

      (%)

      µg/samp

      µg/samp

      (%)

      (%)

      µg/samp

      µg/samp

      (%)

      (%)

      847.6
      847.6
      847.6
      847.6
      847.6
      847.6

      859.1
      823.9
      811.5
      806.0
      805.5
      803.3

      101.4
      97.2
      95.7
      95.1
      95.0
      94.8

      1.4
      -2.8
      -4.3
      -4.9
      -5.0
      -5.2

      401.3
      401.3
      401.3
      401.3
      401.3
      401.3

      430.8
      417.1
      408.8
      399.0
      406.3
      398.9

      107.4
      103.9
      101.9
      99.4
      101.2
      99.4

      7.4
      3.9
      1.9
      -0.6
      1.2
      -0.6

      372.8
      372.8
      372.8
      372.8
      372.8
      372.8

      404.9
      389.1
      383.0
      381.0
      380.2
      380.4

      108.6
      104.4
      102.7
      102.2
      102.0
      102.0

      8.6
      4.4
      2.7
      2.2
      2.0
      2.0

      Table 4.6.4
      Reproducibility Data for Xylenes and Ethylbenzene on SKC 575-002 Passive Samplers

      xylenes

      |
      |
      |

      ethylbenzene

      theo
      µg/samp

      reported
      µg/samp

      recovery
      (%)

      deviation
      (%)

      theo
      µg/samp

      reported
      µg/samp

      recovery
      (%)

      deviation
      (%)

      1622
      1622
      1622
      1622
      1622
      1622

      1695
      1630
      1603
      1586
      1592
      1583

      104.5
      100.5
      98.8
      97.8
      98.2
      97.6

      4.5
      0.5
      -1.2
      -2.2
      -1.8
      -2.4

      |
      |
      |
      |
      |
      |

      302.3
      302.3
      302.3
      302.3
      302.3
      302.3

      312.2
      298.3
      293.9
      295.0
      291.7
      293.7

      103.3
      98.7
      97.2
      97.6
      96.5
      97.2

      3.3
      -1.3
      -2.8
      -2.4
      -3.5
      -2.8

    7. Sampler capacity
      1. Charcoal tubes

        The sampling capacity of charcoal tubes was tested by sampling dynamically generated test atmospheres of mixed xylenes with SKC 226-01 (Lot 2000) sampling tubes. These samples were collected simultaneously along with diffusive samples. The sampling times were 5, 10, 15, and 30 min; and 1, 2, 3, 4, 6, 8, and 10 hours. Three active and three diffusive samples were collected for each time period. The mean concentrations of the test atmospheres were 456 mg/m3 (105 ppm) for m-xylene, 212 mg/m3 (49 ppm) for o-xylene, 198 mg/m3 (46 ppm) for p-xylene, and 161 mg/m3 (37 ppm) for ethylbenzene at 78% relative humidity and 21 °C. These air concentrations were approximately two times the target concentration for xylenes and were in the same proportions as were the analytes in the mixed xylenes used to generate the test atmospheres. No breakthrough from the front to the back section of the sampling tubes for any of the analytes was observed even when samples were collected for ten hours at 50 mL/min. Sampler capacity was never exceeded. Nearly 31 mg of mixed xylenes had been collected after ten hours. The recommended sampling time was set at four hours and the recommended sampling rate at 50 mL/min. These tests also showed that samples can be collected for as short a time as 5 min at 50 mL/min and still provide excellent results.

      2. SKC 575-002 Passive Samplers

        The sampling rate and sampler capacity of SKC 575-002 Passive Samplers were determined with samples collected at the increasing time intervals from the controlled test atmospheres described in Section 4.7.1. The face velocity of the test atmosphere was approximately 0.4 m/s, and the samplers were orientated parallel to the flow direction. Three samples were collected at each time interval. Sampler capacity has been defined to be exceeded when the "apparent" sampling rate decreases rapidly. The sampling rate only appears to decrease because the sampler can collect no additional analyte at the point when capacity is exceeded. Sampling rates are presented in mL/min at 760 mmHg and 25 °C.

        Table 4.7.2
        Determination of Sampling Rate and Recommended Sampling Time

        time

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        (h)

        mL/min

        RSD

        mL/min

        RSD

        mL/min

        RSD

        mL/min

        RSD

        0.083

        13.75

        2.2

        14.25

        3.8

        13.99

        2.8

        13.85

        2.3

        0.167

        13.53

        1.4

        13.97

        1.3

        13.71

        1.8

        13.68

        1.5

        0.25

        13.91

        0.9

        14.38

        0.9

        14.01

        0.9

        13.96

        0.8

        0.5

        13.94

        1.6

        14.39

        2.4

        14.07

        1.7

        13.93

        1.2

        1

        13.81

        2.1

        14.17

        2.4

        13.94

        2.2

        13.86

        2.2

        2

        13.55

        1.7

        13.79

        1.8

        13.59

        1.7

        13.50

        2.0

        3

        14.01

        1.4

        14.27

        1.4

        14.04

        1.4

        13.96

        1.5

        4

        13.60

        0.6

        14.93

        0.9

        13.67

        0.7

        13.59

        0.6

        6

        14.20

        5.0

        14.40

        5.0

        14.48

        5.0

        14.19

        5.0

        8

        13.60

        0.2

        13.70

        0.1

        13.70

        0.2

        13.59

        0.2

        10

        14.11

        2.6

        14.35

        2.5

        14.16

        2.7

        14.06

        2.6

         

        mean

        13.82

        14.24

        13.94

        13.83

        RSD

        1.7

        2.4

        1.9

        1.6

        The preliminary sampling rate was determined by averaging the values for the 0.5, 1, and 2 hour samples. Horizontal lines were constructed 10% above and 10% below the preliminary sampling rate. All the sampling rates were included in the calculated mean sampling rates because all were between the two horizontal lines.

        Figure 4.7.2.1 Sampler capacity data for m-xylene.

        Figure 4.7.2.1 Sampler capacity data for m-xylene.

        Figure 4.7.2.2 Sampler capacity data for o-xylene.

        Figure 4.7.2.2 Sampler capacity data for o-xylene.

        Figure 4.7.2.3 Sampler capacity data for p-xylene.

        Figure 4.7.2.3 Sampler capacity data for p-xylene.

        Figure 4.7.2.4 Sampler capacity data for ethylbenzene.

        Figure 4.7.2.4 Sampler capacity data for ethylbenzene.

    8. Extraction efficiency and stability of extracted samples

      Each laboratory must determine and confirm extraction efficiency periodically. Other solvents can be used in conjunction with this method provided the new solvent is tested. The new solvent should be tested as described below and the extraction efficiency must be greater than 75%.

      A summary of the extraction efficiency results over the range of RQL to 2 times the target concentration is presented in Table 4.8 for quick reference.

      Table 4.8
      Extraction Efficiency (%) Summary

      analyte

      charcoal
      tubes

      SKC 575-002
      Passive Samplers

      m-xylene

      96.3

      96.1

      o-xylene

      93.8

      89.4

      p-xylene

      96.1

      95.3

      ethylbenzene

      97.2

      99.1

      1. Charcoal tubes

        The extraction efficiencies (EEs) of the analytes were determined by liquid-spiking 100-mg portions of SKC Lot 2000 charcoal with the analytes at levels from the RQL to 2 times the OSHA PEL for each analyte. These samples were stored overnight at ambient temperature, and then extracted with 1mL of CS2 (containing 1 µL of p-cymene per mL of CS2) for 1 hour. The samples were vigorously shaken periodically over the extraction time. The EEs of the analytes at the target concentration were also determined from "wet" charcoal to confirm that EE remained constant. Wet charcoal was prepared by collecting samples from a humid (about 80% RH and 22 °C) atmosphere at 50 mL/min for 4 hours. Only the front section of these samples was used to prepare wet EE samples. The stability of extracted samples was investigated by reanalyzing the 1 × PEL samples a day after the original analysis. Three vials were immediately resealed with new septa caps and three vials retained their punctured septa following the original analysis.

        Table 4.8.1.1
        Extraction Efficiency of m-Xylene from SKC Lot 2000 Charcoal

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        0.548

        107.1

        104.6

        97.9

        92.7

        95.4

        95.7

        98.9

        0.05

        256

        96.9

        96.1

        95.3

        94.7

        94.6

        95.8

        95.6

        0.1

        512

        96.5

        99.7

        96.3

        94.0

        96.7

        94.0

        96.2

        0.2

        1024

        96.5

        95.2

        94.6

        96.5

        95.6

        94.4

        95.5

        0.5

        2560

        97.7

        96.0

        94.6

        93.9

        95.0

        95.3

        95.4

        1.0

        5136

        97.0

        96.5

        96.5

        97.6

        98.1

        97.9

        97.3

        2.0

        10486

        93.7

        95.6

        94.3

        97.6

        94.5

        95.5

        95.2

        wet (1.0)

        5136

        98.0

        96.4

        97.7

        97.4

        96.6

        97.9

        97.3

        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 96.3%.

        Table 4.8.1.2
        Extraction Efficiency of o-Xylene from SKC Lot 2000 Charcoal

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        0.785

        99.6

        96.9

        100.8

        88.4

        92.8

        95.0

        95.6

        0.05

        257

        93.8

        93.0

        92.4

        91.6

        91.6

        92.7

        92.5

        0.1

        514

        93.5

        96.7

        93.3

        91.2

        93.7

        91.2

        93.3

        0.2

        1028

        93.6

        92.3

        91.8

        93.6

        92.6

        91.4

        92.6

        0.5

        2570

        94.9

        93.2

        92.0

        91.3

        92.4

        92.7

        92.8

        1.0

        5179

        94.6

        94.0

        94.0

        95.1

        95.4

        95.4

        94.8

        2.0

        10575

        93.2

        94.6

        93.9

        98.5

        93.9

        94.5

        94.8

        wet (1.0)

        5179

        95.2

        93.8

        95.1

        94.8

        93.9

        95.1

        94.7


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 93.8%.

        Table 4.8.1.4
        Extraction Efficiency of Ethylbenzene from SKC Lot 2000 Charcoal

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        0.788

        102.1

        96.9

        100.7

        103.3

        105.6

        90.8

        99.9

        0.05

        256

        96.5

        95.7

        95.0

        94.3

        94.2

        95.3

        95.2

        0.1

        512

        96.1

        99.3

        95.9

        93.7

        96.3

        93.3

        95.8

        0.2

        1024

        96.2

        94.8

        94.2

        96.1

        95.1

        94.0

        95.1

        0.5

        2560

        97.3

        95.6

        94.2

        93.6

        94.6

        94.9

        95.0

        1.0

        5118

        96.6

        96.0

        96.0

        97.2

        97.7

        97.5

        96.8

        2.0

        10450

        93.2

        95.2

        93.8

        96.9

        94.1

        95.1

        94.7

        wet (1.0)

        5118

        97.5

        95.9

        97.3

        96.9

        96.2

        97.5

        96.9


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 96.1%.

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        0.43

        96.9

        97.1

        96.2

        100.7

        109.1

        96.6

        99.4

        0.05

        260

        98.3

        97.4

        96.6

        95.9

        95.9

        97.1

        96.9

        0.1

        519

        97.8

        101.2

        97.6

        95.4

        98.0

        95.2

        97.5

        0.2

        1038

        97.9

        96.5

        95.8

        97.9

        96.8

        95.8

        96.8

        0.5

        2596

        99.0

        97.3

        95.8

        95.1

        96.2

        96.5

        96.7

        1.0

        5216

        98.2

        97.7

        99.0

        98.8

        99.3

        99.1

        98.7

        2.0

        10650

        93.0

        95.7

        93.7

        95.3

        94.2

        95.6

        94.6

        wet (1.0)

        5216

        99.3

        97.7

        99.0

        98.6

        97.9

        99.3

        98.6


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 97.2%.

        Table 4.8.1.5
        Stability of m-Xylene Extracted from SKC Lot 2000 Charcoal

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        97.0

        97.4

        0.4

        97.6

        96.1

        -1.5

        96.5

        97.1

        0.6

        98.1

        96.7

        -1.4

        96.5

        98.2

        1.7

        97.9

        95.9

        -2.0

        >mean

        mean

        96.7

        97.6

        0.9

        97.9

        96.2

        -1.6

        Table 4.8.1.6
        Stability of o-Xylene Extracted from SKC Lot 2000 Charcoal

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        94.6

        95.1

        0.5

        95.1

        93.6

        -1.5

        94.0

        94.6

        0.6

        95.4

        94.1

        -1.3

        94.0

        95.8

        1.8

        95.4

        93.2

        -2.2

        mean

        mean

        94.2

        95.2

        1.0

        95.3

        93.6

        -1.7

        Table 4.8.1.7
        Stability of p-Xylene Extracted from SKC Lot 2000 Charcoal

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        96.6

        97.0

        0.4

        97.2

        95.6

        -1.6

        96.0

        96.7

        0.7

        97.7

        96.2

        -1.5

        96.0

        97.8

        1.8

        97.5

        95.3

        -2.2

        mean

        mean

        96.2

        97.2

        1.0

        97.5

        95.7

        -1.8

        Table 4.8.1.8
        Stability of Ethylbenzene Extracted from SKC Lot 2000 Charcoal

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        98.2

        98.6

        0.4

        98.8

        97.2

        -1.6

        97.7

        98.2

        0.5

        99.3

        97.8

        -1.5

        99.0

        99.4

        0.4

        99.1

        97.0

        -2.1

        mean

        mean

        98.3

        98.7

        0.4

        99.1

        97.3

        -1.7

      2. SKC 575-002 Passive Samplers

        The extraction efficiencies (EE) of the analytes were determined by liquid-spiking 500-mg portions of SKC Anasorb 747 (the sorbent in SKC 575-002 Passive Samplers) with the analytes at levels from the RQL to 2 times the OSHA PEL for each analyte. These samples were stored overnight at ambient temperature, and then extracted with 2 mL of CS2 (containing 1 µL of 1-phenylhexane per mL of CS2) for 1 hour. The samples were vigorously shaken periodically over the extraction time. The EEs of the analytes at the target concentration were also determined from "wet" samplers to confirm that EE remained constant. Wet SKC 575-002 Passive Samplers were prepared by sampling from a humid (about 80% RH and 22 °C) atmosphere for 4 hours. These samples were extracted with 2 mL of CS2 (containing 1 µL of 1-phenylhexane per mL of CS2) for 1 hour on a SKC 226D-03K Desorption Shaker. The stability of extracted samples was investigated by reanalyzing the 1 × PEL samples a day after the original analysis. Three vials were immediately resealed with new septa caps and three vials retained their punctured septa following the original analysis.

        Table 4.8.2.1
        Extraction Efficiency of m-Xylene from SKC Anasorb 747

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        1.422

        93.0

        90.1

        99.0

        89.9

        105.4

        100.9

        96.4

        0.05

        73

        98.6

        97.7

        97.6

        97.2

        98.2

        97.6

        97.8

        0.1

        145

        95.9

        95.9

        93.7

        95.0

        95.8

        95.3

        95.3

        0.2

        290

        93.2

        93.6

        94.2

        94.1

        94.9

        95.6

        94.3

        0.5

        725

        94.1

        95.1

        95.6

        96.3

        94.7

        97.1

        95.5

        1.0

        1451

        97.2

        96.1

        101.1

        95.8

        96.0

        97.0

        97.2

        2.0

        2902

        99.3

        95.3

        96.0

        95.8

        96.4

        95.8

        96.4

        wet (1.0)

        1498

        96.6

        96.7

        93.8

        98.0

        96.7

        95.3

        96.2


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 96.1%.

        Table 4.8.2.2
        Extraction Efficiency of o-Xylene from SKC Anasorb 747

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        1.075

        83.9

        76.4

        86.3

        87.8

        86.6

        88.1

        84.9

        0.05

        73

        92.3

        90.9

        91.0

        90.4

        91.8

        91.5

        91.3

        0.1

        146

        89.8

        89.6

        87.5

        89.0

        89.9

        89.3

        89.2

        0.2

        292

        87.7

        88.0

        88.4

        88.4

        89.0

        89.8

        88.6

        0.5

        728

        88.4

        89.2

        89.8

        90.4

        88.8

        91.2

        89.6

        1.0

        1456

        91.5

        90.5

        95.3

        90.1

        90.4

        91.3

        91.5

        2.0

        2913

        93.7

        88.7

        90.7

        90.5

        90.9

        90.4

        90.8

        wet (1.0)

        1511

        91.0

        90.8

        88.3

        92.2

        91.1

        89.9

        90.6


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 89.4%.

        Table 4.8.2.3
        Extraction Efficiency of p-Xylene from SKC Anasorb 747

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        1.542

        98.2

        95.7

        92.2

        90.9

        97.3

        99.3

        95.6

        0.05

        73

        97.6

        97.2

        96.9

        96.0

        97.4

        96.7

        97.0

        0.1

        145

        95.0

        94.8

        93.0

        94.3

        95.1

        94.7

        94.5

        0.2

        290

        92.4

        92.9

        93.4

        93.3

        94.2

        94.7

        93.5

        0.5

        725

        93.3

        94.3

        94.8

        95.4

        93.9

        96.2

        94.7

        1.0

        1451

        96.3

        95.2

        100.2

        94.9

        95.1

        96.1

        96.3

        2.0

        2902

        99.7

        94.5

        95.2

        95.0

        95.6

        94.9

        95.8

        wet (1.0)

        1493

        95.7

        95.7

        92.9

        97.0

        95.8

        94.4

        95.3


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 95.3%.

        Table 4.8.2.4
        Extraction Efficiency of Ethylbenzene from SKC Anasorb 747

        level

        sample number

        × OSHA PEL

        µg per sample

        1

        2

        3

        4

        5

        6

        mean

        RQL

        1.058

        99.7

        105.0

        93.7

        88.5

        95.2

        103.4

        97.6

        0.05

        74

        102.2

        101.2

        101.1

        100.2

        101.2

        100.8

        101.1

        0.1

        147

        99.1

        99.1

        97.3

        98.6

        99.3

        98.6

        98.7

        0.2

        294

        96.3

        96.8

        97.5

        97.2

        98.4

        98.8

        97.5

        0.5

        736

        97.3

        98.4

        98.9

        99.5

        98.3

        100.5

        98.8

        1.0

        1471

        100.5

        99.3

        104.4

        99.0

        99.1

        100.3

        100.4

        2.0

        2942

        102.6

        98.3

        99.1

        98.8

        99.6

        98.9

        99.6

        wet (1.0)

        1521

        99.8

        100.1

        97.0

        101.3

        100.0

        98.4

        99.4


        The mean EE at concentrations from the RQL to 2 times the PEL (excepting the wet EE) is 99.1%.

        Table 4.8.2.5
        Stability of m-Xylene Extracted from SKC Anasorb 747

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        97.2

        97.8

        0.6

        95.8

        94.2

        -1.6

        96.1

        95.4

        -0.7

        96.0

        94.0

        -2.0

        101.1

        100.0

        -1.1

        97.0

        95.7

        -1.3

        mean

        mean

        98.1

        97.7

        -0.4

        96.3

        94.6

        -1.6

        Table 4.8.2.6
        Stability of o-Xylene Extracted from SKC Anasorb 747

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        91.5

        91.9

        0.4

        90.1

        88.8

        -1.3

        90.5

        89.7

        -0.8

        90.4

        88.7

        -1.7

        95.3

        94.2

        -1.1

        91.3

        90.2

        -1.1

        mean

        mean

        92.4

        91.9

        -0.5

        90.6

        89.2

        -1.4

        Table 4.8.2.7
        Stability of p-Xylene Extracted from SKC Anasorb 747

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        96.3

        96.9

        0.6

        94.9

        93.5

        -1.4

        95.2

        94.6

        -0.6

        95.1

        93.3

        -1.8

        100.2

        99.3

        -0.9

        96.1

        94.9

        -1.2

        mean

        mean

        97.2

        96.9

        -0.3

        95.4

        93.9

        -1.5

        Table 4.8.2.8
        Stability of Ethylbenzene Extracted from SKC Anasorb 747

        punctured septa replaced

        punctured septa retained

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        initial EE
        (%)

        EE after one day
        (%)

        difference
        (%)

        100.5

        101.0

        0.5

        99.0

        97.3

        -1.7

        99.3

        98.7

        -0.6

        99.1

        97.1

        -2.0

        104.4

        103.4

        -1.0

        100.3

        98.8

        -1.5

        mean

        mean

        101.4

        101.0

        -0.4

        99.5

        97.7

        -1.7

    9. Interferences (sampling)
      1. Charcoal tubes

        Retention

        The ability of charcoal tubes to retain mixed xylenes after collection was tested by sampling a test atmosphere containing 454 mg/m3, 211 mg/m3, 198 mg/m3, and 161 mg/m3 m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively (at 80% RH and 20 °C) with six samplers for one hour at 50 mL/min. Three samples were analyzed immediately and three were used to sample contaminant-free humid air for an additional three hours, and then analyzed. All the samples in the second set retained at least 101.0, 101.2, 100.8, 101.0% of the means of the first set for m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively.

        Table 4.9.1
        Retention of Mixed Xylenes on Charcoal Tubes

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        (mg/m3)

        (% mean)

        (mg/m3)

        (% mean)

        (mg/m3)

        (% mean)

        (mg/m3)

        (% mean)

        1st set
        1
        2
        3
        mean
        2nd set
        1
        2
        3

        443.9
        428.5
        447.4
        439.9
         
        444.3
        453.4
        449.5

        101.0
        103.1
        102.2

        203.9
        194.6
        206.1
        201.5
         
        203.9
        208.3
        207.2

        101.2
        103.4
        102.8

        192.6
        185.7
        194.1
        190.8
         
        192.4
        196.7
        195.0

        100.8
        103.1
        102.2

        158.6
        154.8
        159.5
        157.6
         
        159.2
        161.9
        159.5

        101.0
        102.7
        101.2

        Low relative humidity

        The ability of charcoal tubes to collect mixed xylenes at low humidity was tested by sampling a test atmosphere containing 468 mg/m3, 218 mg/m3, 204 mg/m3, 166 mg/m3 m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively (at 5% RH and 20 °C) with three samplers for four hours at 50 mL/min. The samples were analyzed immediately. The sample results (when compared to theoretical concentrations) were 102.0, 100.4, and 99.8% for m-xylene; 101.4, 100.4, and 99.2% for o-xylene; 101.6, 100.1, and 99.6% for p-xylene; and 102.5, 100.8, and 100.4% for ethylbenzene.

        Low concentration

        The ability of charcoal tubes to collect mixed xylenes at low concentrations was tested by sampling a test atmosphere containing 22 mg/m3, 10 mg/m3, 10 mg/m3, 8 mg/m3 m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively (at 80% RH and 22 °C) with three samplers for four hours at 50 mL/min. The samples were analyzed immediately. The sample results (when compared to theoretical concentrations) were 95.2, 97.6, and 102.2 for m-xylene; 94.6, 96.1, and 101.2% for o-xylene; 95.0, 97.2, and 101.8% for p-xylene; and 96.1, 98.6, and 102.5% for ethylbenzene.

        Interference

        The ability of charcoal tubes to collect mixed xylenes in the presence of sampling interferences was tested by sampling a test atmosphere containing 230 mg/m3, 107 mg/m3, 100 mg/m3, 82 mg/m3, 365 mg/m3, 372 mg/m3 m-xylene, o-xylene, p-xylene, ethylbenzene, toluene, and butyl acetate respectively (at 81% RH and 21 °C) with three samplers for four hours at 50 mL/min. The samples were analyzed immediately. The sample results (when compared to theoretical concentrations) were 103.3, 102.9, and 101.8 for m-xylene; 102.8, 102.5, and 101.2% for o-xylene; 103.2, 102.6, and 101.6% for p-xylene; and 104.1, 103.4, and 102.6% for ethylbenzene.

      2. SKC 575-002 Passive Samplers

        Reverse diffusion

        The ability of SKC 575-002 Passive Samplers to retain mixed xylenes after collection was tested by sampling a test atmosphere containing 454 mg/m3, 211 mg/m3, 198 mg/m3, and 161 mg/m3 m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively (at 80% RH and 20 °C) with six samplers for one hour. Three samples were analyzed immediately and three were used to sample contaminant-free humid air for an additional three hours, and then analyzed. Sampling rates from Section 4.7 were converted to their equivalents under experimental temperature and pressure and used to calculate results in Table 4.9.2. All the samples in the second set retained at least 100.2, 99.6, 99.8, and 100.0% of the means of the first set for m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively.

        Table 4.9.2
        Retention of Mixed Xylenes on SKC 575-002 Passive Samplers

        m-xylene

        o-xylene

        p-xylene

        ethylbenzene

        (mg/m3)

        (% mean)

        (mg/m3)

        (% mean)

        (mg/m3)

        (% mean)

        (mg/m3)

        (% mean)

        1st set
        1
        2
        3
        mean
        2nd set
        1
        2
        3

        450.6
        449.4
        419.5
        439.8
         
        440.7
        449.0
        449.4

        100.2
        102.1
        102.2

        206.9
        208.0
        191.9
        202.3
         
        201.4
        206.0
        205.9

        99.6
        101.8
        101.8

        195.7
        197.0
        182.0
        191.6
         
        191.2
        195.0
        195.3

        99.8
        101.8
        101.9

        161.2
        162.8
        149.9
        158.0
         
        157.9
        160.8
        161.4

        100.0
        101.8
        102.2

        Low relative humidity

        The ability of SKC 575-002 Passive Samplers to collect mixed xylenes at low humidity was tested by sampling a test atmosphere containing 468 mg/m3, 218 mg/m3, 204 mg/m3, 166 mg/m3 m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively (at 5% RH and 20 °C) with three samplers for four hours. The samples were analyzed immediately. Sampling rates (760 mmHg and 25 °C) were 13.92, 13.63, and 13.94 mL/min for m-xylene; 14.23, 13.93, and 14.24 mL/min for o-xylene; 14.05, 13.77, and 14.08 mL/min for p-xylene; and 14.01, 13.73, and 14.02 mL/min for ethylbenzene.

        Low concentration

        The ability of SKC 575-002 Passive Samplers to collect mixed xylenes at low concentrations was tested by sampling a test atmosphere containing 22 mg/m3, 10 mg/m3, 10 mg/m3, 8 mg/m3 m-xylene, o-xylene, p-xylene, and ethylbenzene, respectively (at 80% RH and 22 °C) with three samplers for four hours. The samples were analyzed immediately. Sampling rates (760 mmHg and 25 °C) were 13.44, 13.68, and 13.16 mL/min for m-xylene; 13.90, 14.28, and 13.53 mL/min for o-xylene; 13.32, 13.69, and 13.36 mL/min for p-xylene; and 13.71, 13.76, and 13.37 mL/min for ethylbenzene.

        Interference

        The ability of SKC 575-002 Passive Samplers to collect mixed xylenes in the presence of sampling interferences was tested by sampling a test atmosphere containing 230 mg/m3, 107 mg/m3, 100 mg/m3, 82 mg/m3, 365 mg/m3, 372 mg/m3 m-xylene, o-xylene, p-xylene, ethylbenzene, toluene, and butyl acetate respectively (at 81% RH and 21 °C) with three samplers for four hours. The samples were analyzed immediately. Sampling rates (760 mmHg and 25 °C) were 13.73, 13.12, and13.77 mL/min for m-xylene; 14.06, 13.43, and 14.08 mL/min for o-xylene; 13.86, 13.25, and 13.90 mL/min for p-xylene; and 13.80, 13.18, and 13.86 mL/min for ethylbenzene.

    10. Qualitative analysis

      The identity of suspected mixed xylenes can be confirmed by GC/mass spectrometry. Mass spectra for the analytes are presented below.

      Figure 4.10.1 Mass spectrum for m-xylene.

      Figure 4.10.1 Mass spectrum for m-xylene.

      Figure 4.10.2 Mass spectrum for o-xylene.

      Figure 4.10.2 Mass spectrum for o-xylene.

      Figure 4.10.3 Mass spectrum for p-xylene.

      Figure 4.10.3 Mass spectrum for p-xylene.

      Figure 4.10.4 Mass spectrum for ethylbenzene.

      Figure 4.10.4 Mass spectrum for ethylbenzene.

  • 1. Kirk-Othmer Encyclopedia of Chemical Technology; 3rd ed.; Grayson, M Ed.; John Wiley & Sons: New York, 1984, Vol. 24; pp. 709-744.
  • 2. Documentation of the Threshold Limits Values and Biological and Indices, 6th ed., American Conference of Governmental Industrial Hygienists, Inc: Cincinnati, OH, 1991, Vol. III, pp. 187-193.
  • 3. OSHA Analytical Methods Manual; Vol. 1; U.S. Department of Labor, Occupational Safety and Health Administration; Directorate for Technical Support, OSHA Salt Lake Technical Center: Salt Lake City, UT, 1990; Method 7: Organic Vapors; American Conference of Governmental Hygienists (ACGIH): Cincinnati, OH; Publication No. 4542.
  • 4. NIOSH Manual of Analytical Methods, 4th ed.; U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health: Cincinnati, OH, 1996, Method 1501: Hydrocarbons, Aromatic; (NIOSH) Cincinnati, OH; Publication No. 94-113.
  • 5. Documentation of the Threshold Limits Values and Biological and Indices, 6th ed., American Conference of Governmental Industrial Hygienists, Inc: Cincinnati, OH, 1991, Vol. III, pp. 1732-1740.
  • 6. Documentation of the Threshold Limits Values and Biological and Indices, 6th ed., American Conference of Governmental Industrial Hygienists, Inc: Cincinnati, OH, 1991, Vol. I, pp. 581-584.
  • 7. 1998 TLVs and BEIs, Threshold Limit Values for Chemical Substances and Physical Agents, ISBN: 1-882417-23-2; American Conference of Governmental Industrial Hygienists, (ACGIH): Cincinnati, OH, 1998.
  • 8. Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; Grayson, M Ed.; John Wiley & Sons: New York, 1984, Vol. 24; pp. 709-744.
  • 9. ACS Publications; Production growth sputtered in most sectors (accessed March 1999).
  • 10. Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; Grayson, M Ed.; John Wiley & Sons: New York, 1984, Vol. 24; pp. 709-744.
  • 11. The Condensed Chemical Dictionary, 8th ed.; Revised by Hawley, G., Ed., Van Nostrand Reinhold: New York, 1971, p. 358, 942, 943.
  • 12. The Condensed Chemical Dictionary, 8th ed.; Revised by Hawley, G., Ed., Van Nostrand Reinhold: New York, 1971, p. 358, 942, 943.
  • 13. Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; Grayson, M Ed.; John Wiley & Sons: New York, 1984, Vol. 24; pp. 709-744.
  • 14. OSHA Computerized Information System Database, Chemical Sampling Information, Salt Lake Technical Center, Occupational Safety and Health Administration, Salt Lake City, UT March 1999.
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  • 21. Burright, D.; Chan, Y.; Eide, M.; Elskamp, C.; Hendricks, W.; Rose, M. "Evaluation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis", OSHA Salt Lake Technical Center, U.S. Department of Labor: Salt Lake City, UT, 1999 (in-revision).
  • 22. Burright, D.; Chan, Y.; Eide, M.; Elskamp, C.; Hendricks, W.; Rose, M. "Evaluation Guidelines for Air Sampling Methods Utilizing Chromatographic Analysis", OSHA Salt Lake Technical Center, U.S. Department of Labor: Salt Lake City, UT, 1999 (in-revision).
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