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Xylenes (o-, m-, p-isomers) Ethylbenzene, 1002

Related Information: Chemical Sampling - Xylene , Ethyl Benzene
 
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 1999Warren Hendricks
  
Methods Development Team
Industrial Hygiene Chemistry Division
OSHA Salt Lake Technical Center
Sandy UT 84070


1. General Discussion
1.1 Background
1.1.1 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.

1.1.2 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".

1.1.3 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

1.1.4 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

m-xylene
Structural formula of o-xylne

o-xylene
Structural formula of p-xylne

p-xylene
Structural formula of ethyl benzene

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).

1.2 Limit defining parameters
1.2.1 Detection limit of the analytical procedure

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)
Table 1.2.1
DLAP (pg per sample)

xylenesm-xyleneo-xylenep-xyleneethylbenzene

14.52.18.414.05.7



1.2.2 Detection limit of the overall procedure

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)
Table 1.2.2.1
DLOP for Charcoal Tubes

analytengppbµg/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



SKC 575-002 Passive Samplers

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)
Table 1.2.2.2
DLOP for SKC 575-002
Passive Samplers

analytengppbµg/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



1.2.3 Reliable quantitation limit

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)
Table 1.2.3.1
RQL for Charcoal Tubes

analytengppbµg/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



SKC 575-002 Passive Samplers

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)
Table 1.2.3.2
RQL for SKC 575-002 Passive Samplers

analyteng ppbµg/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



1.2.4 Instrument calibration

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

analytecharcoal tubesSKC 575-002
Pass Samplers
r2k2r2k2

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



1.2.5 Precision (overall procedure)

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)
Table 1.2.5.1
Precision of the Overall Procedure for Charcoal Tubes

analyteprecision (±%)

xylenes
m-xylene
o-xylene
p-xylene
ethylbenzene
10.8
10.7
11.0
11.1
10.6



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



1.2.6 Recovery

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

analytecharcoal
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



1.2.7 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.
2.1 Apparatus
2.1.1 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).

2.1.2 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.
2.2 Reagents

None required.

2.3 Technique
2.3.1 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.

2.3.2 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.
2.4 Sampler capacity
2.4.1 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)

2.4.2 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)
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.
2.5.1 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-xyleneo-xylenep-xyleneethylbenzene

96.393.896.197.2



2.5.2 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-xyleneo-xylenep-xyleneethylbenzene

96.189.495.399.1

2.6 Recommended sampling time and sampling rate
2.6.1 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.

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

m-xyleneo-xylenep-xyleneethylbenzene

13.8214.2413.9413.83



2.6.3 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.
2.7 Sampling interferences (Section 4.9)
2.7.1 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.

2.7.2 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.
3.1 Apparatus
3.1.1 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.

3.1.2 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.

3.1.3 An electronic integrator or other suitable means of measuring GC detector response. A Waters Millennium Chromatography Manager system was used in this evaluation.

3.1.4 Two and four-milliliter glass vials with PTFE-lined septum caps.

3.1.5 One and two-milliliter volumetric pipets.

3.1.6 A SKC Desorption Shaker with rack (226D-03K) was used to extract SKC 575-002 Passive Samplers in this evaluation.
3.2 Reagents
3.2.1 Xylenes, Isomers plus ethylbenzene, 98.5+%, A.C.S. reagent, Aldrich Chemical Co., Lot TR 02505LR, was used in this evaluation.

3.2.2 m-xylene, 99+%, anhydrous, Aldrich Chemical Co., Lot 00249MQ, was used in this evaluation.

3.2.3 o-Xylene, 98%, Spectrophotometric Grade, Aldrich Chemical Co., Lot 07946PN, was used in this evaluation.

3.2.4 p-Xylene, 99+%, anhydrous, Aldrich Chemical Co., Lot TQ 25949MQ, was used in this evaluation.

3.2.5 Ethylbenzene, 99.8%, anhydrous, Aldrich Chemical Co., Lot DR 03249JQ, was used in this evaluation.

3.2.6 Carbon disulfide (CS2), 99.9+%, low benzene content, Aldrich Chemical Co., Lot 07546PN, was used in this evaluation.

3.2.7 1-Phenylhexane (hexylbenzene), 97%, Aldrich Chemical Co., Lot 03006PZ, was used as an internal standard for SKC 575-002 Passive Samplers in this evaluation.

3.2.8 p-Cymene, 99%, Aldrich Chemical Co., Lot 11703TR, was used as an internal standard for charcoal tube samples in this evaluation.

3.2.9 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.

3.2.10 GC grade nitrogen, air, and hydrogen were used in this evaluation.
3.3 Standard preparation
3.3.1 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.

3.3.2 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.

3.3.3 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.

3.3.4 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.
3.4 Sample preparation
3.4.1 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.

3.4.2 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.
3.5 Analysis
3.5.1 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


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  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.  




3.5.2 Measure peak areas with an electronic integrator or other suitable means.

3.5.3 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.

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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.
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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.
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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.
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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.
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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.
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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.
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Figure 3.5.3.7 Calibration curve for ethylbenzene standards used to analyze charcoal tubes constructed from the data in Table 4.3.4.
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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.
3.6 Interferences (analytical)
3.6.1 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.

3.6.2 The identity or purity of an analyte peak can be confirmed with additional analytical data. (Section 4.10)
3.7 Calculations
3.7.1 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


3.7.2 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-xyleneo-xylenep-xyleneethylbenzene

13.8214.2413.9413.83


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:


=
(
)
 
[
T+273
298
]
1.5  
[
760
P
]
SR amb
SRNTP
 
 


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.
4.1 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
analyteDLAP (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

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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

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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

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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

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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

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

4.2 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
analytecharcoal
tubes
SKC 575-002
Passive Samplers
ngµg/m3ppbngµg/m3ppb

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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
charcoal
tubes
SKC 575-002
Passive Samplers
analytengµg/m3ppbEE(%)ngµg/m3ppbEE(%)

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



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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.
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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.

4.3 Instrument calibration

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

analyte charcoal
tubes
SKC 575-002
Pass Sampers
r2 k2r2 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



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 Tubes
× 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



4.4 Precision (overall procedure)
4.4.1 Charcoal tubes
 
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.
Table 4.4.1
SEEs and Precisions of the
Overall Procedure for Charcoal Tubes

analyteSEE(%)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



4.4.2 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

4.5 Storage tests
4.5.1 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



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Figure 4.5.1.1 Ambient storage test for xylenes collected on charcoal tubes.
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Figure 4.5.1.2 Regrigerated storage test for xylenes collected on charcoal tubes.
 
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Figure 4.5.1.3 Ambient storage test for m-xylene collected on charcoal tubes.
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Figure 4.5.1.4 Regrigerated storage test for m-xylene collected on charcoal tubes.
 
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Figure 4.5.1.5 Ambient storage test for o-xylene collected on charcoal tubes.
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Figure 4.5.1.6 Regrigerated storage test for o-xylene collected on charcoal tubes.
 
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Figure 4.5.1.7 Ambient storage test for p-xylene collected on charcoal tubes.
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Figure 4.5.1.8 Regrigerated storage test for p-xylene collected on charcoal tubes.
 
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Figure 4.5.1.9 Ambient storage test for ethylbenzene collected on charcoal tubes.
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Figure 4.5.1.10 Regrigerated storage test for ethylbenzene collected on charcoal tubes.


4.5.2 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



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Figure 4.5.2.1 Ambient storage test for xylenes collected on SKC 575-002 Passive Samplers.
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Figure 4.5.2.2 Regrigerated storage test for xylenes collected on SKC 575-002 Passive Samplers.
 
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Figure 4.5.2.3 Ambient storage test for m-xylene collected on SKC 575-002 Passive Samplers.
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Figure 4.5.2.4 Regrigerated storage test for m-xylene collected on SKC 575-002 Passive Samplers.
 
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Figure 4.5.2.5 Ambient storage test for o-xylene collected on SKC 575-002 Passive Samplers.
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Figure 4.5.2.6 Regrigerated storage test for o-xylene collected on SKC 575-002 Passive Samplers.
 
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Figure 4.5.2.7 Ambient storage test for p-xylene collected on SKC 575-002 Passive Samplers.
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Figure 4.5.2.8 Regrigerated storage test for p-xylene collected on SKC 575-002 Passive Samplers.
 
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Figure 4.5.2.9 Ambient storage test for ethylbenzene collected on SKC 575-002 Passive Samplers.
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Figure 4.5.2.10 Regrigerated storage test for ethylbenzene collected on SKC 575-002 Passive Samplers.
4.6 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
g/samp
g/samp
(%)
(%)
g/samp
g/samp
(%)
(%)
g/samp
g/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
g/samp
g/samp
(%)
(%)
g/samp
g/samp
(%)
(%)
g/samp
g/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



4.7 Sampler capacity
4.7.1 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.

4.7.2 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/minRSDmL/minRSDmL/minRSDmL/minRSD

0.08313.752.214.253.813.992.813.852.3
0.16713.531.413.971.313.711.813.681.5
0.2513.910.914.380.914.010.913.960.8
0.513.941.614.392.414.071.713.931.2
113.812.114.172.413.942.213.862.2
213.551.713.791.813.591.713.502.0
314.011.414.271.414.041.413.961.5
413.600.614.930.913.670.713.590.6
614.205.014.405.014.485.014.195.0
813.600.213.700.113.700.213.590.2
1014.112.614.352.514.162.714.062.6
 
mean13.8214.2413.9413.83
RSD1.72.41.91.6


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.

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Figure 4.7.2.1 Sampler capacity data for m-xylene.
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Figure 4.7.2.2 Sampler capacity data for o-xylene.
 
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Figure 4.7.2.3 Sampler capacity data for p-xylene.
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Figure 4.7.2.4 Sampler capacity data for ethylbenzene.
4.8 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-xylene96.396.1
o-xylene93.889.4
p-xylene96.195.3
ethylbenzene97.299.1

4.8.1 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 PELµg per sample123456mean

RQL0.548107.1104.697.992.795.495.798.9
0.0525696.996.195.394.794.695.895.6
0.151296.599.796.394.096.794.096.2
0.2102496.595.294.696.595.694.495.5
0.5256097.796.094.693.995.095.395.4
1.0513697.096.596.597.698.197.997.3
2.01048693.795.694.397.694.595.595.2
wet (1.0)513698.096.497.797.496.697.997.3


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 PELµg per sample123456mean

RQL0.78599.696.9100.888.492.895.095.6
0.0525793.893.092.491.691.692.792.5
0.151493.596.793.391.293.791.293.3
0.2102893.692.391.893.692.691.492.6
0.5257094.993.292.091.392.492.792.8
1.0517994.694.094.095.195.495.494.8
2.01057593.294.693.998.593.994.594.8
wet (1.0)517995.293.895.194.893.995.194.7


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


Table 4.8.1.3
Extraction Efficiency of p-Xylene from SKC Lot 2000 Charcoal
level
sample number
× OSHA PELµg per sample123456mean

RQL0.788102.196.9100.7103.3105.690.899.9
0.0525696.595.795.094.394.295.395.2
0.151296.199.395.993.796.393.395.8
0.2102496.294.894.296.195.194.095.1
0.5256097.395.694.293.694.694.995.0
1.0511896.696.096.097.297.797.596.8
2.01045093.295.293.896.994.195.194.7
wet (1.0)511897.595.997.396.996.297.596.9


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


Table 4.8.1.4
Extraction Efficiency of Ethylbenzene from SKC Lot 2000 Charcoal
level
sample number
× OSHA PELµg per sample123456mean

RQL0.4396.997.196.2100.7109.196.699.4
0.0526098.397.496.695.995.997.196.9
0.151997.8101.297.695.498.095.297.5
0.2103897.996.595.897.996.895.896.8
0.5259699.097.395.895.196.296.596.7
1.0521698.297.799.098.899.399.198.7
2.01065093.095.793.795.394.295.694.6
wet (1.0)521699.397.799.098.697.999.398.6


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
(%)

97.097.40.497.696.1-1.5
96.597.10.698.196.7-1.4
96.598.21.797.995.9-2.0
mean mean
96.797.60.997.996.2-1.6



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
(%)

94.695.10.595.193.6-1.5
94.094.60.695.494.1-1.3
94.095.81.895.493.2-2.2
mean mean
94.295.21.095.393.6-1.7



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
(%)

96.697.00.497.295.6-1.6
96.096.70.797.796.2-1.5
96.097.81.897.595.3-2.2
mean mean
96.297.21.097.595.7-1.8



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
(%)

98.298.60.498.897.2-1.6
97.798.20.599.397.8-1.5
99.099.40.499.197.0-2.1
mean mean
98.398.70.499.197.3-1.7



4.8.2 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 PELµg per sample123456mean

RQL1.42293.090.199.089.9105.4100.996.4
0.057398.697.797.697.298.297.697.8
0.114595.995.993.795.095.895.395.3
0.229093.293.694.294.194.995.694.3
0.572594.195.195.696.394.797.195.5
1.0145197.296.1101.195.896.097.097.2
2.0290299.395.396.095.896.495.896.4
wet (1.0)149896.696.793.898.096.795.396.2


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 PELµg per sample123456mean

RQL1.07583.976.486.387.886.688.184.9
0.057392.390.991.090.491.891.591.3
0.114689.889.687.589.089.989.389.2
0.229287.788.088.488.489.089.888.6
0.572888.489.289.890.488.891.289.6
1.0145691.590.595.390.190.491.391.5
2.0291393.788.790.790.590.990.490.8
wet (1.0)151191.090.888.392.291.189.990.6


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 PELµg per sample123456mean

RQL1.54298.295.792.290.997.399.395.6
0.057397.697.296.996.097.496.797.0
0.114595.094.893.094.395.194.794.5
0.229092.492.993.493.394.294.793.5
0.572593.394.394.895.493.996.294.7
1.0145196.395.2100.294.995.196.196.3
2.0290299.794.595.295.095.694.995.8
wet (1.0)149395.795.792.997.095.894.495.3


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 PELµg per sample123456mean

RQL1.05899.7105.093.788.595.2103.497.6
0.0574102.2101.2101.1100.2101.2100.8101.1
0.114799.199.197.398.699.398.698.7
0.229496.396.897.597.298.498.897.5
0.573697.398.498.999.598.3100.598.8
1.01471100.599.3104.499.099.1100.3100.4
2.02942102.698.399.198.899.698.999.6
wet (1.0)152199.8100.197.0101.3100.098.499.4


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
(%)

97.297.80.695.894.2-1.6
96.195.4-0.796.094.0-2.0
101.1100.0-1.197.095.7-1.3
mean mean
98.197.7-0.496.394.6-1.6



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
(%)

91.591.90.490.188.8-1.3
90.589.7-0.890.488.7-1.7
95.394.2-1.191.390.2-1.1
mean mean
92.491.9-0.590.689.2-1.4



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
(%)

96.396.90.694.993.5-1.4
95.294.6-0.695.193.3-1.8
100.299.3-0.996.194.9-1.2
mean mean
97.296.9-0.395.493.9-1.5



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
(%)

100.5101.00.599.097.3-1.7
99.398.7-0.699.197.1-2.0
104.4103.4-1.0100.398.8-1.5
mean mean
101.4101.0-0.499.597.7-1.7

4.9 Interferences (sampling)
4.9.1 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.

4.9.2 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.
4.10 Qualitative analysis

The identity of suspected mixed xylenes can be confirmed by GC/mass spectrometry. Mass spectra for the analytes are presented below.
For problems with accessibility in using figures, illustrations and PDF in this method, please contact the SLTC at (801) 233-4900.
Figure 4.10.1 Mass spectrum for m-xylene.
  For problems with accessibility in using figures, illustrations and PDF in this method, please contact the SLTC at (801) 233-4900.
Figure 4.10.2 Mass spectrum for o-xylene.
 
 
For problems with accessibility in using figures, illustrations and PDF in this method, please contact the SLTC at (801) 233-4900.
Figure 4.10.3 Mass spectrum for p-xylene.
  For problems with accessibility in using figures, illustrations and PDF in this method, please contact the SLTC at (801) 233-4900.
Figure 4.10.4 Mass spectrum for ethylbenzene.







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