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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.

Petroleum Distillate Fractions
(This method was fully evaluated with Stoddard solvent.
It can also be used to determine V.M.&P. naphtha and mineral spirits.)



Related Information: Chemical Sampling - Petroleum Distillate Fractions


 
Method no.: 48

Matrix: Air

Target concentration: 2900 mg/m3 Stoddard solvent (OSHA PEL)

Procedure: Samples are collected by drawing a known volume of air through charcoal tubes. Samples are desorbed with carbon disulfide (CS2) and analyzed by gas chromatography (GC) using a flame ionization detector (FID).

Recommended air volume
and sampling rate:

3 L at 0.2 L/min

Reliable quantitation limit: 0.77 mg/sample (260 mg/m3)

Precision: (1.96 SD)
(Section 4.3.2.)
17.8%

Status of method: Evaluated method. This method has been subjected to the established evaluation procedures of the Organic Methods Evaluation Branch.



Date: November 1984 Chemist: Michael L. Shulsky
Organic Methods Evaluation Branch
OSHA Analytical Laboratory
Salt Lake City, Utah


1. General Discussion
1.1. Background
1.1.1. History Three refined petroleum mixtures are routinely analyzed at this laboratory. They are Stoddard solvent (boiling range 160-210C), mineral spirits (boiling range 150-200C), and petroleum distillates (V.M.&P. naphtha; boiling range 95-160C). These mixtures will collectively be termed petroleum distillate fractions (PDF) throughout this method. All of these PDFs contain aliphatic and to a lesser extent aromatic hydrocarbons. (Ref. 5.1.)

The procedures for collection (charcoal tubes) and analysis (GC/FID) of PDFs described in this evaluation are basically those used in NIOSH methods S380 and S382. (Ref. 5.2.) For preparation of analytical standards, these NIOSH methods require a sample of the bulk material presumed to be the source of the air contamination (this bulk material will be referred to as the "source PDF" throughout this method). The shipment of source PDFs, which are often flammable, is inconvenient and the materials sometime require distillation before use in standards. For these reasons and because similar responses to different hydrocarbons are observed using a FID (Ref. 5.3.), the use of analytical standards prepared from a PDF which is not the source PDF was investigated. In order to determine analytical conditions, it was assumed that this substitute PDF ("non-source PDF") should be of the same type, i.e. Stoddard solvent, mineral spirits, or petroleum distillates, as that used at the sampling site.

Internal standards (Istd) are routinely used in solvent analyses at this laboratory. Since the actual constituents of PDFs are unknown, the presence of an internal standard may cause an interference with the PDF or unduly lengthen the analysis time. For these reasons, the possibility of using an external standard (Estd) procedure was examined.

Also, in preliminary work it became apparent that the manner in which the baseline was set was a concern. If the data system was allowed to automatically set the baseline, inconsistencies in the positions to which the baseline was drawn were noticed (Figures 4.8.1. and 4.8.2.). This produced calibration errors at lower concentrations of PDFs. To overcome this problem, an evaluation of certain "integrate functions" available in the data system software which control the baseline was done (Section 4.8.4.).

In order to evaluate the parameters of baseline, Estd, and material used to prepare analytical standards, a study was done utilizing eight different PDFs consisting of five Stoddard solvents, two V.M.&P. naphthas and one mineral spirits. These were used to spike 8 sets of 12 charcoal tubes. Each 12-tube set was quantitated using analytical standards prepared from both source and non-source PDF. There were no restrictions on the analytical conditions or GC column used for these analyses, in order to avoid having data which would apply to only certain analytical conditions. (Section 4.8.)

The results of this study indicate several things; there is no significant difference in results obtained by using either the source or non-source PDF (Section 4.8.2.), an internal standard is not needed when consistent injection size can be maintained (Section 4.8.2.), and consistent setting of the baseline may be obtained by using "integrate functions". (Section 4.8.4.).

Other tests performed for this evaluation were break through, storage stability, desorption efficiencies, precision of the analytical procedure, sensitivity and reliable quantitation limit. The breakthrough tests were performed with both a Stoddard solvent (Section 4.4.1.) and a V.M.&P. naphtha (Section 4.4.2.) to ensure the collection procedure would work for the more volatile constituents of a V.M.&P. naphtha. All of the other tests were performed using a Stoddard solvent but the collection and analytical procedure should also be applicable to petroleum distillates and mineral spirits.

There are two OSHA PELs that pertain to petroleum distil late fractions. The PELs are 2900 mg/m3 for Stoddard solvent and 2000 mg/m3 for petroleum distillates (naphtha). Due to numerous synonyms and the overlapping boiling range fractions that are available, there is much confusion as to which standard is applicable in many instances. Mineral spirits, which is almost identical to Stoddard solvent in boiling range, should be compared to the Stoddard solvent PEL; while the lower boiling range petroleum distillate fractions should be compared to the petroleum distillate (naphtha) PEL.

This evaluation shows that PDFs can be collected using charcoal with a 3-L air volume, analyzed by GC/FID and a non-source PDF may be used to prepare analytical standards.


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

"Short-term Exposure: Overexposure to Stoddard solvent causes irritation of the eyes, nose, and throat and may cause dizziness. Very high air concentrations may cause unconsciousness and death. Long-term Exposure: Prolonged overexposure to the liquid may cause skin irritation." (Ref. 5.4.)

"Short-term Exposure: Overexposure to petroleum distillates may cause dizziness, drowsiness, headache, and nausea. They may also cause irritation of the eyes, throat, and skin. Long-term Exposure: Prolonged exposure may cause drying and cracking of the skin." (Ref. 5.5.)

Men were exposed to mineral spirits concentrations of 2500 to 5000 mg/m3 for an unspecified time period. Both concentrations produced nausea and vertigo in the subjects. In another study at 4000 mg/m3 there was a prolongation of reaction time. (Ref. 5.1.)


1.1.3. Potential workplace exposure

NIOSH estimates that about 600,000 workers in the United States are potentially exposed to all "specialized naphthas" (Ref. 5.1.).

Petroleum distillates (V.M.&P. naphtha) is used as a quick evaporating paint thinner. Stoddard solvent is used in the dry cleaning industry. Mineral spirits is a general purpose thinner, a dry cleaning agent, and a solvent for paint and varnish industries. (Ref. 5.1.)


1.1.4. Physical properties (Ref. 5.1. unless otherwise stated)

Petroleum distillates
molecular weight: approximately 87-114
odor: pleasant aromatic odor
boiling range: 95 - 160C
specific gravity: 0.7275 - 0.7603
color: clear, water white to yellow
vapor pressure: 2 - 20 mm Hg at 20C
flashpoint: -6.7 to 12.8C (closed cup)
synonyms: benzine, naphtha 76, ligroin, high boiling petroleum ether
molecular species: C7-C11

Stoddard solvent
molecular weight: approximately 135 - 145
odor: kerosene-like
boiling range: 160 - 210C
specific gravity: 0.75 - 0.80
color: colorless
vapor pressure: 4 - 4.5 mm Hg at 25C
flashpoint: 37.8C (closed cup)
synonyms: 140 flash solvent, odorless solvent and low end point solvent
molecular species: C9-C11

Mineral spirits
molecular weight: approximately 144 - 169
odor: pleasant sweet odor
boiling range: 150 - 200C
specific gravity: 0.77 - 0.81
color: clear, water white
vapor pressure: 0.8 mm (Hg) at 20C
flashpoint: 30.2 - 40.5C (closed cup)
synonyms: white spirits, petroleum spirits, and light petrol
molecular species: C9-C12
1.2. Limit defining parameters (Air concentrations are based on the recommended air volume (3 L) and a desorption volume of 1 mL.)
1.2.1. Detection limits

Since PDF consist of numerous and varying components, the determination of meaningful detection limits was not considered feasible.


1.2.2. Reliable quantitation limit

The reliable quantitation limit is 0.77 mg/sample (260 mg/m3) This concentration was arrived at by taking all the results for calibration methods #4 and #5 from Tables 4.8.1. through 4.8.8. that were near certain concentrations, i.e. 0.3 mg/mL and 0.7 mg/mL, and finding the average recoveries, the average concentrations, and standard deviations (SD) near those concentrations. The results for samples near 0.77 mg/mL met both the requirements of 75% recovery and a precision (1.96 SD) of 25% or better. (Section 4.2.)


1.2.3. Sensitivity

The sensitivity of the analytical procedure over a range representing 0.5 to 2 times the target concentration based on the recommended air volume is 300954 area units per mg/mL. This is determined by the slope of the calibration curve. (Section 4.3.3.)


1.2.4. Recovery

The recovery of samples used in a 15-day storage test remained above 94% (Section 4.6.). The recovery of the analyte from the collection medium during storage must be 75% or greater.


1.2.5. Precision of the analytical procedure

The pooled coefficient of variation obtained from replicate determinations of analytical standards at 0.5, 1, and 2 times the target concentration is 0.019 (Section 4.3.1.).


1.2.6. Precision of the overall procedure

The precision of the overall procedure at the 95% confidence level is 17.8% (Section 4.3.2.). This includes an additional 5% for sampling error. The overall procedure must provide results that are 25% or better at the 95% confidence level.


1.2.7. Reproducibility

Six samples spiked by liquid injection and a draft copy of this procedure were given to a chemist unassociated with this evaluation. The samples were analyzed after 2 days of storage at 22C. The average recovery was 97.7% with a SD of 3.53%. (Section 4.7.)
1.3. Advantages
1.3.1. The collection procedure is convenient.


1.3.2. The analytical procedure is rapid and precise.
1.4. Disadvantages

None
2. Sampling Procedure
2.1. Apparatus
2.1.1. A personal sampling pump which can be calibrated within 5% of the recommended flow rate is needed.


2.1.2. Coconut shell charcoal tubes which consist of glass tubes 7 cm long, 6-mm o.d., and 4-mm i.d., containing a 100-mg section and a 50-mg section of charcoal separated with a urethane foam plug are used. The glass tube is flame sealed at both ends. For this evaluation, SKC, Inc. charcoal tubes, lot 120, were used.
2.2. Reagents

None required


2.3. Technique
2.3.1. Immediately before sampling, break open the ends of the charcoal tube. All tubes should be from the same lot of charcoal.


2.3.2. Connect the charcoal tube to the pump with a short piece of flexible tubing. The 50-mg portion of the charcoal tube is used as the backup section; therefore, air should flow through the 100-mg portion first.


2.3.3. Position the tube vertically to avoid channeling through the charcoal.


2.3.4. Air being sampled should not pass through any hose or tubing before entering the charcoal tube.


2.3.5. Record the temperature and relative humidity of the atmosphere being sampled.


2.3.6. Immediately after sampling, seal the ends of the tubes with the plastic caps.


2.3.7. With each set of samples, submit at least one blank charcoal tube from the same lot as the sample tubes. The blank tube should be treated in the same manner as the samples (break ends, seal, transport) except no air is drawn through it.


2.3.8. Transport the samples and corresponding paperwork to the laboratory for analysis.


2.3.9. Submit source PDF whenever possible. Place the material in glass bottles with Teflon-lined caps, and transport to laboratory separately from air samples.
2.4. Breakthrough

Studies to determine the 5% breakthrough value were done near the PEL for Stoddard solvent, using a dynamically generated atmosphere with approximately 75% relative humidity at 22C and a sampling rate of 0.203 L/min. These studies were performed using only the 100 mg portion of a charcoal tube. The average breakthrough for Stoddard solvent was 6.9 L and average capacity was 20 mg. (Section 4.4.1.). Breakthrough studies were performed with a petroleum distillate (V.M.&P.) naphtha since this type of PDF boils at a lower temperature. The average breakthrough volume for this V.M.&P. naphtha was 9.4 L and the average capacity was 20.3 mg. (Section 4.4.2.)


2.5. Desorption efficiency

Desorption efficiencies were determined at several different loadings of Stoddard solvent. These loadings corresponded to the mass of Stoddard solvent which would be collected on a charcoal tube when sampling 3 L of an atmosphere containing 0.1, 0.5, 1, and 2 times the PEL. The tubes were prepared by liquid injection of the Stoddard solvent and stored in a refrigerator for 24 h before analysis. The average desorption efficiency was 100%. (Section 4.5.)


2.6. Recommended air volume and sampling rate.

The recommended air volume is 3 L at 0.2 L/min.


2.7. Interferences
2.7.1. Since charcoal will collect vapors from many organic compounds all organics being used in significant amounts near the sampling area could decrease the capacity of the charcoal for PDF.


2.7.2. Water vapor also may decrease the capacity of charcoal.
2.8. Safety precautions
2.8.1. Wear eye protection when breaking the ends of the charcoal tubes.


2.8.2. Place the sampling pump on the employee in a manner so it will not interfere with the work being done.


2.8.3. Place the charcoal tube in a holder so the broken ends are not exposed.


2.8.4. Obey all safety regulations of the workplace.
3. Analytical Procedure
3.1. Apparatus
3.1.1. A gas chromatograph (GC) equipped with a flame ionization detector (FID) is used for analysis. A Hewlett-Packard 5710 GC was primarily used in this evaluation.


3.1.2. A GC column capable of separating carbon disulfide (CS2) and the internal standard, if any, from the constituents of the PDF. For this evaluation, a 20 ft by 1/8 in. stainless steel column packed with 10% SP-1000 on 80/100 Supelcoport was used.


3.1.3. An integrator for determining peak area is needed. A Hewlett-Packard 3357 data system was used.


3.1.4. Small vials with Teflon-lined caps for desorption of charcoal: Two-milliliter vials are preferable.


3.1.5. Microliter syringes such as 10-µL for preparing standards and 1-µL for sample injection are needed.


3.1.6. Pipettes for dispensing the desorbing solution may be used. A 1-mL reagent dispenser is convenient.


3.1.7. Volumetric flasks are used for standard preparation.


3.1.8. An analytical balance is used to prepare standards.


3.1.9. A distillation apparatus may be needed.
3.2. Reagents
3.2.1. Carbon disulfide, reagent grade.


3.2.2. Source PDF, when possible, from the operation where sampling was done.


3.2.3. Internal standard compound such as hexylbenzene, reagent grade (optional).


3.2.4. GC grade hydrogen, air and nitrogen.


3.2.5. Desorbing solvent: CS2 or 1 µL internal standard/mL CS2.
3.3. Standard preparation
3.3.1. Analytical standards are prepared in the desorbing solvent.


3.3.2. Source PDF received from the sampling site may be used as the analytical standard if it appears clear and colorless, and has a density in the range of 0.74-0.79 g/mL. If the bulk is colored or has a density greater than 0.79 g/mL, it needs to be distilled to separate the volatile solvents from the pigments or heavier oils before it can be used as an analytical standard.


3.3.3. If source PDF is not submitted or is unusable, a nonsource PDF from the laboratory should be used.


3.3.4. Standards must be prepared at four different concentrations so proper integration of the peaks may be confirmed (Section 3.5.3.). A useful range for standard concentrations is approximately 1 µL/mL to 10 µL/mL.
3.4. Sample preparation
3.4.1. The 100-mg portion of the charcoal tube is placed in a vial and the 50-mg portion is placed in a separate vial. The glass wool and urethane plugs are discarded.


3.4.2. One milliliter of desorbing solvent is added to each vial.


3.4.3. The vials are immediately capped and shaken periodically for 30 min before analysis.
3.5. Analysis
3.5.1. GC conditions
oven: initial temperature 100C for 4 min programmed to 180C at 8/min
injector: 200C
detector: 225C
nitrogen (carrier): 22 mL/min
hydrogen: 30 mL/min
air: 250 mL/min

injection size: 1 µL

chromatogram: Figure 3.5.1.



3.5.2. The data system used in this evaluation was a Hewlett-Packard 3357 which contains several "integrate functions." The integrate function termed "hold the baseline" should be used for the analyses. This function should be started before the constituents of the petroleum distillate fraction begin to elute from the column and it should be canceled after the PDF constituents have eluted or when column bleed becomes significant whichever occurs first.


3.5.3. The areas of the peaks due to PDF constituents are added together (area summation) in the analysis of the standards and samples. The summed areas and the concentration of the analytical standards are used to determine a linear least squares fit equation. The concentration of the samples is determined by entering their summed areas into the least squares equation.


3.5.4. If the peaks present in the samples do not elute in approximately the same time range as the standards, a comparison of the constituents in the samples and standard should be done by GC/MS to confirm that the samples do contain PDF type compounds and of what type for reporting purposes. If distinct analytes are confirmed by GC/MS, their identity and approximate concentration should be reported.


3.5.5. Any sample above the PEL should be confirmed by GC/MS or another suitable technique.
3.6. Interferences
3.6.1. Since PDF are mixtures of aliphatic and aromatic hydrocarbons and elute from a GC in a peak cluster, it may be difficult to eliminate interfering compounds. If a large interfering peak appears in an air sample, identification by GC/MS may be necessary.


3.6.2. It may be difficult to separate a single analyte which is requested for analysis from the PDF constituents. Changing columns such as from a polar to a non-polar (SP-1000 to an SP-2100) may help separate the analyte.
3.7. Calculations
3.7.1. PDF should be reported as mg/m3 since any ppm value would require the use of an approximate molecular weight.


3.7.2. The air concentration in mg/m3 is determined from the mass of analyte in the sample as in the following example:

Upon analysis, 3.5 mg was found for a sample with a 3-L air volume.

mg/m3 = (mg/desorption efficiency)/air vol.
mg/m3 = (3.5 mg/1.00)/(0.003 m3)
mg/m3 = 1167 mg/m3
3.8. Safety precautions
3.8.1. Work in a hood when using solvents during sample and standard preparation.


3.8.2. Keep solvents away from sources of high temperatures such as detectors and injectors.


3.8.3. Avoid skin contact with solvents.


3.8.4. Wear safety glasses at all times.
4. Backup data
4.1. Detection limits of the analytical and overall procedure

The determination of detection limit values is not practical in the context of a rigid definition such as a peak with a height of 5 times the baseline noise. Since PDFs may have similar constituents which have unsimilar concentrations, there is no one representative peak that can be used to determine detection limits for all PDFs.


4.2. Reliable quantitation limit

The amount of 0.77 mg/sample (260 mg/m3) is determined to be the approximate amount reliably quantitated for any applicable petroleum distillate fraction within the requirements of at least 75% recovery and a precision (1.96 SD) of 25% or better. The injection size recommended in the analytical procedure (1 µL) was used in the determination of the reliable quantitation limit.

Table 4.2.
Reliable Quantitation Limit Data

sample calibration mass (mg) mass (mg) %
number method* Istd spiked recovered recovered

1



8



14



21



31



35



39



47



51



60



65



70



76



83
#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5

#4

#5
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
yes
no
0.789
0.789
0.789
0.789
0.789
0.789
0.789
0.789
0.777
0.777
0.777
0.777
0.777
0.777
0.777
0.777
0.753
0.753
0.753
0.753
0.753
0.753
0.753
0.753
0.754
0.754
0.754
0.754
0.754
0.754
0.754
0.754
0.779
0.779
0.779
0.779
0.779
0.779
0.779
0.779
0.761
0.761
0.761
0.761
0.761
0.761
0.761
0.761
0.776
0.776
0.776
0.776
0.776
0.776
0.776
0.776
0.873
0.823
0.773
0.762
0.847
0.806
0.751
0.746
0.812
0.779
0.930
0.863
0.753
0.778
0.845
0.845
0.643
0.663
0.703
0.689
0.684
0.696
0.748
0.723
0.658
0.552
0.602
0.529
0.655
0.715
0.609
0.685
0.828
0.823
0.825
0.821
0.820
0.810
0.818
0.809
0.793
0.778
0.816
0.788
0.824
0.793
0.831
0.819
0.900
0.949
0.838
0.845
0.851
0.912
0.792
0.815
111
104
98
96
107
102
95
95
104
100
120
111
97
100
109
109
85
88
93
92
91
92
99
96
87
73
80
70
87
95
81
91
106
106
106
105
105
104
105
104
104
102
107
102
108
104
109
108
116
122
108
109
110
117
102
105
mean = 100.7%
SD = 10.76
1.96 SD = 21.09%

* Explanation of calibration methods under Table 4.8.2.



4.3. Precision and Sensitivity
4.3.1. The precision of the analytical method was determined by replicate injections of analytical standards prepared at 0.5, 1, and 2 times the target concentration. The pooled coefficient of variation is 0.019.

Table 4.3.1.
Precision of Analytical Method

target conc. 0.5 1 2

area counts 1322304 2761497 5482172
1272435 2731651 5394150
1328744 2757576 5505614
1350244 2735224 5451850
1377105 2731653 5466193
1381708 2693328 5413149

mean 1338756 2735155 5452188
SD     40538     24375     42052
CV      0.030    0.0089    0.0077

pooled coefficient of variation = 0.019




4.3.2. The precision of the overall procedure was calculated by taking the average of the SDs for methods #4 and #5 (both Istd and Estd) from Table 4.8.1. and multiplying by 1.96. This number includes 5% for sampling error. The usual value on the cover page is the standard error of estimate from the storage test but in this evaluation this value would not have included variability for using different PDFs for analytical standards.


4.3.3. Sensitivity is defined as the slope of the calibration curve for analytical standards from 0.5 to 2 times the target concentration. (Table 4.3.1., Figure 4.3.2.) The sensitivity is 300954 area counts/(mg/mL). The sensitivity will change depending on the detector and method of integration.
4.4. Breakthrough
4.4.1. Breakthrough was determined by sampling a dynamically generated test atmosphere of Stoddard solvent (about 2900 mg/m3 with 76% RH at 23C), using a charcoal tube containing only the 100-mg portion of charcoal and monitoring the concentration of Stoddard solvent in the air which had passed through the charcoal. Five-percent breakthrough is defined as the point during this sampling when the air exiting the charcoal tube has a concentration of Stoddard solvent that is 5% of the test atmosphere. Two tests were performed, with 5% breakthrough air volumes of 6.5 L and 7.3 L and capacities of 19.1 mg and 21.5 mg being obtained respectively. The average 5% breakthrough air volume was 6.9 L and capacity was 20.3 mg. (Fig. 4.4.)


4.4.2. Breakthrough tests were also performed using a petroleum distillate bulk since its boiling range is lower than Stoddard solvent and it contains more volatile constituents. The test atmospheres were about 2000 mg/m3 with 74% RH at 23C. Three tests were performed, with 5% breakthrough air volumes of 9.6, 9.1 and 9.5 L and capacities of 20.82, 19.73 and 19.95 mg being obtained respectively. The average capacity was 20.3 mg and the average 5% breakthrough air volume was 9.4 L.
4.5. Desorption efficiencies

Desorption efficiencies were determined by injecting known amounts of Stoddard solvent onto the 100-mg portion of six charcoal tubes, allowing them to sit overnight and analyzing the tubes on the next day. The average desorption efficiency over the range of 0.08 to 2 times the target concentration is 100%.

Table 4.5.
Desorption Efficiencies

target conc.
µg/sample
0.08
0.76
0.5
4.55
1
9.1
2
18.6

desorption
efficiency,
%




mean

mean = 100%
103
102
99
102
100
103

102
100
101
102
102
101
101

101
100
100
100
101
101
101

101
99
99
98
95
96
94

97




4.6. Storage data

Thirty-six samples were collected from a dynamically generated atmosphere of Stoddard solvent. The atmosphere was approximately 2900 mg/m3 and 75% RH at 22C. Of these 36 samples, six were analyzed immediately, while the remaining 30 were stored; 15 at ambient temperature and 15 at -5C. Approximately every third day, 3 samples from each of the storage sets were analyzed. The average recovery was 96% for ambient storage and 97% for refrigerated storage. The data of Table 4.6. are shown graphically in Figures 4.6.1. and 4.6.2.

Table 4.6.
Storage Tests

storage time
(days)
% recovery
(refrigerated)
% recovery
(ambient)

  0
  3
  7
11
13
19
99
96
96
97
96
97
99
97
97
96
96
99
99
96
97
96
96
97
97
95
95
95
95
98
99
96
96
96
96
96
100  
96
97
97
96
96




4.7. Reproducibility data

Six samples, spiked by liquid injection, and a draft copy of this procedure were given to a chemist unassociated with this evaluation. The samples were analyzed after 3 days of storage at 22C. The average recovery was 97.7% with a standard deviation of 3.53%.

Table 4.7.
Reproducibility Results

amount spiked (µg) amount recovered (µg) % recovered

7756
7756
7756
7756
7756
7756
7432
7510
7443
7493
7466
8136
95.8
96.8
95.8
96.6
96.3
104.9

mean
SD
=
=
97.7
3.53




4.8. Quantitation factors
4.8.1. A total of 96 samples were used to evaluate differences between source and non-source PDF, automatic baseline set and controlled baseline set, and internal and external standard procedures. They were prepared by liquid injection of each of 8 PDFs on 12 charcoal tubes. These 8 sets were prepared at different times. Each set and an aliquot of the source PDF were given to the branch of this laboratory which routinely analyzes samples for PDF. The samples were desorbed with a CS2/Istd solution and analytical standards were prepared in the same solution from the source PDF and a non-source PDF chosen by the analyst. The data for these standards and samples was quantitated with nine different calibration methods. Explanations of these calibration methods are given at the bottom of Table 4.8.2. Both internal and external standard procedures were used for calibration methods #1-5. For the external standard procedure, the peak from the internal standard was ignored in all the calculations. The results from these 8 sets of PDF samples are presented in Tables 4.8.2. 4.8.9., each table represents the data from one PDF. Table 4.8.1. summarizes the data as average percent recoveries for all PDFs analyzed with each calibration method using internal and external standard procedures. For all calibration methods except #3 the summation of the peak areas for the constituents of the PDF was used to determine the response factors. Method #3 used the peak area of the largest peak in the PDF for determination of the response factors.


4.8.2. The six analytical standards were analyzed at the same time as the samples. A linear least squares fit for each set of standards was used in all of the calibration methods except methods #3, #8 and #9. In these cases only one standard was used for calibration. Source PDF was used with calibration methods #1, #4, #6 and #8. By comparing the average results and the standard deviations obtained for method #1 to #2, #4 to #5, #6 to #7, and #8 to #9 in Table 4.8.1., it can be seen that there is no significant difference in the results; therefore, source or non-source PDF may be used to prepare analytical standards.


4.8.3. An internal standard was present in all of the samples used but results were calculated both with the internal standard correction and without it for calibration methods #1 through #5. (Tables 4.8.1. to 4.8.9.). For all of the analyses, automatic liquid sampling devices were used with a single injection of each sample. At the bottom of Table 4.8.1. are the average results for all the PDFs using all the calibration methods calculated with both the internal standard (Istd) and external standard (Estd) procedures. From this data there appears to be no real difference between the results using the Istd correction and not (Estd). The use of an internal standard is left to the judgment of the analyst since the lengthening of the analysis and possible interferences caused by an internal standard compound will be different for each set of samples.


4.8.4. Three different techniques of setting the baseline during analysis were investigated. One technique was to allow the data system (Hewlett-Packard 3357) to calculate the baseline and set it automatically. The other techniques require the analyst to control the baseline by using either a basic program to set the baseline and integrate the area under the chromatogram or an "integrate function" built into the data system to set the baseline.
4.8.4.1. At lower concentrations of PDFs, the technique of allowing the data system to automatically set the baseline produced inconsistent results. (Figure 4.8.1. and 4.8.2.) This may be due to a parameter in the data system termed "slope sensitivity", but since single analytes are often requested in addition to PDF, setting the slope sensitivity for PDF may not be accurate for the single analytes. Calibration methods #6, #7, #8 and #9 used this technique (Tables 4.8.1. - 4.8.9.). The results in Table 4.8.1. are the average recoveries for each calibration technique with the 8 different PDFs. As can be seen in this table, the percent recoveries for each separate PDF using calibration methods #6, #7, #8 and #9 ranged from 28-143%. The average results listed at the bottom of the table for all PDFs using these four calibration methods ranged from 74-103%. Methods #6 and #7 used a linear least squares fit for calibration while methods #8 and #9 used a one point calibration. The linear least squares fit does provide results (103 and 96%) closer to the expected value but the standard deviation is larger than for methods #1-#5 in which the baseline is controlled. Therefore, controlling the baseline is recommended.


4.8.4.2. Calibration methods #1 and #2 used a basic program for baseline setting and integration. This basic program was written to be used after analyzing the standards, blanks and samples. The raw data collected during an analysis is in the form of area slices which are simply detector voltages taken and stored every 0.5 s. The analyst enters into the basic program the time span over which the PDF constituents elute. The program saves the value of the first area slice in the analytical run to be used as the baseline and when the start time of the PDF is reached the program subtracts the baseline area slice from all the area slices in the specified time span and sums the differences. This summation is used as the area of PDF constituents. This program integrated the area above the baseline but not as individual peaks. The average recoveries are presented in Table 4.8.1. Since this program did not have any peak detection routine, it would not differentiate between a rise in the baseline due to a peak and column bleed. Therefore, if the baseline was not consistent and PDF constituents were eluting from the column at these times, area may be added to the PDF area which was caused by column bleed and not PDF constituents. This technique of baseline control is not recommended.


4.8.4.3. The two evaluated integrate functions which control the baseline were "hold the baseline" (Figure. 4.8.2.) and "valley reset" (Figure 4.8.4.). The "valley reset" function resets the baseline every time the data system detects a zero slope or a switch from negative to positive slope of the detector output. This function is performed by the data system with start and stop times entered by the analyst. Calibration method #3 used this function and the area of the largest peak for calibration of a response factor. As can be seen in Table 4.8.1., the average results for all the PDFs analyzed with method #4 were 102(2.3)% with the internal standard procedure and 102(4.1)% with the external standard procedure. Comparing these results to those of the other calibration methods, method #4 is the most accurate. However, this method requires that the source PDF be used as analytical standards because the ratio of the area of the chosen peak to the others in the PDF must be constant.


4.8.4.4. The "hold the baseline" function simply records the detector voltage at a certain time during the analysis and maintains that as the baseline until the function is canceled. The time to start this function is slightly before the PDF constituents begin to elute and the time to cancel it is after the constituents have eluted or when column bleed becomes significant. Both of these times are set by the analyst. After the function is canceled, the data system is free to set the baseline and it usually does correct for baseline drift due to column bleed; therefore, excess area is not added to the PDF as it was with the basic program. Calibration methods #4 and 5 used this technique. The average results and standard deviations for all PDFs for these two methods given at the bottom of Table 4.8.1. are better than the other calibration methods except #3, although this calibration method (#3) requires the use of source PDF in preparing analytical standards. Therefore, using the integrate function of "hold the baseline" is recommended and a linear least squares fit of the standards should be used to quantitate the samples.
4.8.5. Recommendations

For analysis of petroleum distillate fractions, either the source PDF (Section 3.3.2.) or a non-source PDF may be used to prepare analytical standards. It is recommended that the baseline be controlled with the "hold the baseline" integrate function during elution of the PDF constituents or until column bleed becomes significant whichever occurs first. Finally, either internal standard or external standard may be used with no loss in accuracy or precision.

Table 4.8.1.
Average Percent Recoveries
Calculated from Tables 4.8.2. to 4.8.9.

(see notes)                                calibration methods                                 
table Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

4.8.2. yes 105 96 104 107 95 97 92 100 93
no 103 95 100 102 95 x x x x

4.8.3. yes 106 115 104 100 111 99 101 110 110
no 108 115 104 106 109 x x x x

4.8.4. yes 109 104 99 91 99 93 113 91 93
no 115 106 103 94 98 x x x x

4.8.5. yes 103 102 104 90 83 110 93 93 91
no 103 105 102 87 83 x x x x

4.8.6. yes 99 97 100 104 103 95 84 75 75
no 98 96 99 103 103 x x x x

4.8.7. yes 100 95 104 103 104 107 110 31 32
no 99 97 100 100 102 x x x x

4.8.8. yes 95 91 100 106 99 143 100 29 28
no 104 93 109 114 101 x x x x

4.8.9. yes 119 125 100 99 100 83 73 67 73
no 135 135 95 95 95 x x x x

mean(PDFs-Istd) 105 103 102 100 99 103 96 74 74
SD 7.3 11.5 2.3 6.4 8.1 18.0 13.2 30.6 29.7

mean(PDFs-Estd) 108 105 102 100 98 x x x x
SD 12.1 14.1 4.1 8.2 7.7 x x x x

notes:
1.) Explanation of Calibration methods under table 4.8.2.
2.) Istd column: "yes" indicates internal standard was used; "no" indicates an external standard procedure used.
3.) "x" under calibration methods #6, 7, 8 9 indicates no data was collected with an external standard procedure.




Table 4.8.2.
Percent Found for Stoddard solvent A

(see notes)                             calibration methods                              
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

1 789 yes 104 96 102 111 98 96 91 101 93
no 102 93 97 104 96 x x x x
2 3159 yes 101 94 103 106 94 99 93 102 94
no 100 92 98 100 93 x x x x
3 4739 yes 102 94 104 107 95 99 92 101 93
no 101 94 100 103 95 x x x x
4 237 yes 120 103 107 109 97 91 87 96 88
no 108 98 102 101 94 x x x x
5 6318 yes 103 94 104 104 93 103 96 104 96
no 101 94 101 101 93 x x x x
6 3159 yes 102 95 105 105 94 102 102 105 9
no 103 95 101 101 94 x x x x
7 6318 yes 103 94 104 106 94 101 93 102 94
no 101 95 101 103 95 x x x x
8 789 yes 102 94 101 107 95 91 86 95 88
no 100 92 97 102 95 x x x x
9 4739 yes 103 95 105 107 95 102 95 104 96
no 103 95 102 104 96 x x x x
10 2369 yes 102 95 104 108 96 97 92 101 93
no 103 95 101 104 97 x x x x
11 237 yes 115 99 105 104 92 86 81 90 83
no 105 95 101 99 91 x x x x
12 2369 yes 104 97 106 110 98 99 94 97 95
no 106 97 104 107 99 x x x x

notes:
1.) Calibration method #1 uses as analytical standards the source PDF, the basic program for peak integration and area summation of the standards for calibration.
2.) Calibration method #2 uses as analytical standards a non-source PDF, otherwise the same as #1.
3.) Calibration method #3 uses the source PDF, "valley reset" for peak integration and a single peak in the standards for calibration.
4.) Calibration method #4 uses as analytical standards the source PDF, "hold the baseline" for peak integration and area summation of standards for calibration.
5.) Calibration method #5 uses as analytical standards a non-source PDF, otherwise the same as #4.
6.) Calibration method #6 uses as analytical standards the source PDF, the data system sets the baseline for peak integration, and area summation of standards for calibration.
7.) Calibration method #7 uses as analytical standards a non-source PDF, otherwise the same as #6.
8.) Calibration method #8 uses as analytical standards the source PDF, the data system sets the baseline for peak integration, and area summation of only one standard for calibration.
9.) Calibration method #9 uses as analytical standards a non-source PDF, otherwise the same as #8.




Table 4.8.3.
Percent Found for Stoddard Solvent B

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

13 3109 yes 112 119 111 116 128 103 95 103 103
no 107 114 106 111 118 x x x x
14 777 yes 111 120 108 104 120 125 122 137 136
no 108 116 103 100 111 x x x x
15 233 yes 122 141 103 89 96 79 132 136 136
no 117 125 94 lost 89 x x x x
16 5440 yes 106 113 106 106 117 107 98 105 105
no 104 110 104 104 112 x x x x
17 7772 yes 106 114 104 105 116 107 103 106 105
no 104 110 103 105 112 x x x x
18 233 yes 107 125 103 79 78 55 101 114 113
no 108 116 103 lost 76 x x x x
19 4663 yes 101 108 101 lost 113 99 89 98 98
no 107 114 106 107 115 x x x x
20 3109 yes 100 106 100 99 114 97 86 97 97
no 109 116 107 106 119 x x x x
21 777 yes 99 108 100 97 109 105 102 118 118
no 104 112 103 100 109 x x x x
22 7772 yes 104 112 103 104 114 105 101 104 104
no 106 113 107 108 115 x x x x
23 5440 yes 103 110 104 104 115 104 95 103 103
no 110 117 111 111 119 x x x x
24 4663 yes 100 107 101 102 113 99 89 98 98
no 107 114 108 108 116 x x x x

note: Explanation of calibration methods under Table 4.8.2.




Table 4.8.4.
Percent Found for V.M.&P. Naphtha A

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

25 7528 yes 103 102 104 89 98 102 104 102 104
no 120 105 106 94 98 x x x x
26 5270 yes 102 104 103 89 97 101 105 102 104
no 112 107 107 95 99 x x x x
27 7528 yes 106 104 107 92 100 105 107 105 107
no 119 105 106 94 98 x x x x
28 1506 yes 106 107 98 92 100 93 105 93 95
no 110 109 105 98 102 x x x x
29 3011 yes 100 103 97 88 96 98 104 98 100
no 106 106 104 94 98 x x x x
30 226 yes 172 119 96 100 110 72 148 65 66
no 177 121 101 100 102 x x x x
31 753 yes 98 99 94 85 93 88 111 86 88
no 99 99 99 88 92 x x x x
32 5270 yes 99 102 101 88 96 101 103 100 102
no 106 103 103 92 96 x x x x
33 753 yes 101 103 94 91 99 91 114 89 91
no 101 102 98 92 96 x x x x
34 1506 yes 100 106 98 92 100 93 105 93 95
no 103 108 105 97 101 x x x x
35 226 yes 124 103 95 97 106 71 146 64 65
no 126 103 99 93 96 x x x x
36 3011 yes 97 103 98 89 97 98 104 98 100
no 103 106 105 95 99 x x x x

note: Explanation of calibration methods under Table 4.8.2.




Table 4.8.5.
Percent Found for V.M.&P. Naphtha B

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

37 3768 yes 103 98 106 96 88 103 98 101 99
no 95 93 97 86 83 x x x x
38 6029 yes 102 100 110 96 87 103 99 103 101
no 95 98 97 86 82 x x x x
39 754 yes 102 100 101 87 80 106 84 87 85
no 94 94 93 73 70 x x x x
40 2261 yes 106 100 105 97 89 100 92 95 93
no 99 95 98 88 85 x x x x
41 301 yes 95 109 100 72 66 111 54 58 57
no 90 106 94 52 50 x x x x
42 4522 yes 101 97 102 92 85 100 97 100 98
no 104 105 104 94 90 x x x x
43 3768 yes 104 99 105 94 86 104 99 102 100
no 107 106 107 96 86 x x x x
44 2261 yes 106 99 104 95 87 102 95 97 95
no 109 104 108 98 94 x x x x
45 301 yes 113 124 101 77 70 127 70 74 73
no 117 129 105 79 75 x x x x
46 6028 yes 102 100 111 95 87 103 100 103 101
no 107 114 110 98 94 x x x x
47 754 yes 106 104 191 87 81 157 133 89 87
no 113 111 108 95 91 x x x x
48 4522 yes 103 97 106 94 86 103 99 102 100
no 109 111 112 100 95 x x x x

note: Explanation of calibration methods under Table 4.8.2.




Table 4.8.6.
Percent Found for Stoddard Solvent D

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

49 3897 yes 99 99 101 100 98 100 90 88 88
no 98 97 98 98 97 x x x x
50 6235 yes 99 98 101 98 98 94 88 88 88
no 97 96 99 97 97 x x x x
51 779 yes 96 92 97 106 106 96 78 61 61
no 95 91 96 106 105 x x x x
52 545 yes 92 87 95 105 105 105 82 59 59
no 91 85 94 104 104 x x x x
53 6235 yes 100 99 102 99 98 95 88 89 88
no 100 99 102 99 99 x x x x
54 2338 yes 102 101 102 106 105 109 95 89 89
no 100 99 100 104 104 x x x x
55 545 yes 99 94 101 112 112 69 82 60 60
no 98 93 100 112 112 x x x x
56 3897 yes 101 100 102 101 100 101 91 89 89
no 100 100 101 100 100 x x x x
57 1559 yes 100 99 101 105 105 94 79 70 70
no 101 99 101 106 105 x x x x
58 2338 yes 101 100 101 103 102 89 77 71 71
no 100 99 100 101 101 x x x x
59 1559 yes 100 98 101 105 104 93 79 70 70
no 102 100 102 107 106 x x x x
60 779 yes 100 96 100 105 105 99 80 63 63
no 767 739 769 810 809 x x x x

note: Explanation of calibration methods under Table 4.8.2.




Table 4.8.7.
Percent Found for Stoddard Solvent D

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

61 3045 yes 102 100 102 103 102 102 104 34 34
no 96 100 96 98 103 x x x x
62 3045 yes 102 101 102 104 103 102 104 34 34
no 96 101 97 98 103 x x x x
63 6853 yes 103 102 104 102 102 103 105 34 34
no 100 101 99 98 102 x x x x
64 1523 yes 98 94 96 101 104 100 102 30 31
no 97 98 94 100 101 x x x x
65 761 yes 97 89 99 104 107 114 116 29 30
no 100 92 97 102 104 x x x x
66 533 yes 99 87 119 107 110 125 127 28 28
no 106 90 117 105 106 x x x x
67 6853 yes 99 97 100 98 101 98 100 33 33
no 98 99 97 96 97 x x x x
68 533 yes 99 87 100 107 108 125 127 28 29
no 105 88 96 103 106 x x x x
69 1523 yes 98 94 101 101 103 100 102 30 31
no 96 97 97 98 100 x x x x
70 761 yes 101 93 119 108 109 117 119 30 31
no 102 94 115 104 108 x x x x
71 4568 yes 100 99 99 100 101 99 102 33 34
no 9699 95 96 99 x x x x
72 4568 yes 100 98 104 100 102 99 101 33 34
no 96 100 100 97 99 x x x x

note: Explanation of calibration methods under Table 4.8.2.




Table 4.8.8.
Percent Found for Stoddard solvent E

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

73 7756 yes 104 94 103 99 92 106 102 35 34
no 108 96 111 106 94 x x x x
74 2327 yes 103 98 103 103 95 153 105 35 34
no 110 100 112 109 97 x x x x
75 3878 yes 104 97 102 100 93 132 102 35 34
no 110 98 111 106 95 x x x x
76 776 yes 89 88 96 116 108 139 77 17 16
no 99 88 103 122 109 x x x x
77 5429 yes 101 94 102 97 90 116 98 34 32
no 108 96 109 104 93 x x x x
78 7756 yes 102 93 101 96 89 103 97 33 32
no 110 97 112 106 94 x x x x
79 388 yes 78 81 99 130 125 206 112 17 16
no 91 80 106 140 126 x x x x
80 3878 yes 101 94 103 98 91 129 99 34 33
no 108 97 110 105 94 x x x x
81 5429 yes 102 94 103 99 92 118 100 35 33
no 111 99 112 109 97 x x x x
82 2327 yes 100 96 102 101 94 151 109 34 33
no 110 99 112 108 97 x x x x
83 776 yes 84 83 95 110 102 170 97 24 23
no 96 86 104 117 105 x x x x
84 388 yes 77 79 98 122 114 199 108 16 15
no 92 80 107 132 118 x x x x

note: Explanation of calibration methods under Table 4.8.2.




Table 4.8.9.
Results for Mineral Spirits A

(see notes)                             calibration methods                                    
sample µg Istd #1 #2 #3 #4 #5 #6 #7 #8 #9

85 7673 yes 109 113 106 101 106 103 99 94 100
no 100 98 88 91 90 x x x x
86 230 yes 186 200 108 90 88 57 109 43 46
no 270 275 98 82 94 x x x x
87 1534 yes 149 158 119 129 135 110 93 86 92
no 144 145 107 119 117 x x x x
88 5371 yes 107 110 103 102 107 100 92 86 92
no 115 113 106 108 107 x x x x
89 7673 yes 106 110 103 96 101 107 104 99 106
no 116 113 107 102 101 x x x x
90 537 yes 210 224 65 123 114 50 40 37 40
no 226 228 67 108 106 x x x x
91 2302 yes 110 115 104 104 107 89 76 70 75
no 112 112 101 102 99 x x x x
92 1534 yes 107 113 106 106 108 91 76 70 75
no 112 112 103 103 102 x x x x
93 537 yes 61 65 71 62 56 39 32 30 31
no 73 74 64 54 54 x x x x
94 230 yes 82 89 106 72 78 45 36 33 35
no 143 149 96 67 66 x x x x
95 5371 yes 99 103 101 93 97 110 101 95 102
no 106 105 106 99 97 x x x x
96 2302 yes 104 110 106 106 110 90 77 71 76
no 103 103 104 104 102 x x x x

note: Explanation of calibration methods under Table 4.8.1.




Chromatogram of PDF standard
Figure 3.5.1. Chromatogram of PDF standard.




Sensitivity
Figure 4.3.2. Sensitivity.




Breakthrough curve
Figure 4.4. Breakthrough curve.




Desorption efficiencies
Figure 4.5. Desorption efficiencies.




Ambient storage
Figure 4.6.1. Ambient storage.




Refrigerated storage
Figure 4.6.2. Refrigerated storage.




Automatic baseline set
Figure 4.8.1. Automatic baseline set.




Automatic baseline set
Figure 4.8.2. Automatic baseline set.




Controlled baseline with
Figure 4.8.3. Controlled baseline with "hold the baseline" function.




Controlled baseline with
Figure 4.8.4. Controlled baseline with "valley reset" function.
5. References
5.1. "Criteria for a Recommended Standard...Occupational Exposure to Refined Petroleum Solvents"; Department of Health, Education and Welfare, National Institute for Occupational Safety and Health: Cincinnati, OH, 1977 (DHEW) (NIOSH) Publ. (U.S.) No. 77-192.


5.2. "NIOSH Manual of Analytical Methods", 2nd ed.; Department of Health, Education and Welfare, National Institute for Occupational Safety and Health: Cincinnati, OH, 1977; Vol. 3, Methods S380 and S382; DHEW (NIOSH) Publ. (U.S.) No. 77-157-C.


5.3. Drushel, Harry V. Journal of Chromatographic Science. 21, August 1983, p 375.


5.4. "Occupational Health Guideline for Stoddard Solvent", Department of Health and Human Services, National Institute for Occupational Safety and Health: U.S. Government Printing Office, Washington, D.C., 1978; Publ. 81-123.


5.5. "Occupational Health Guideline for Petroleum Distillates", Department of Health and Human Services, National Institute for Occupational Safety and Health: U.S. Government Printing Office, Washington, D.C. 1978; Publ. 81-123.  



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