| Method number: | 111 | |||
| Matrix: | Air | |||
| Target concentration: OSHA PEL: ACGIH TLV: |
TWA
200 ppm (753 mg/m3) 200 ppm (753 mg/m3) 50 ppm (188 mg/m3) |
Ceiling (10 min)
300 ppm (1130 mg/m3) 300 ppm (1130 mg/m3) none |
Peak
500 ppm (1883 mg/m3) 500 ppm (1883 mg/m3) none | |
| Procedure: | Adsorbent tube samples are collected by drawing
workplace air through either coconut shell charcoal or
Anasorb® 747 tubes with personal sampling
pumps. Diffusive samples are collected by exposing either 3M 3520
Organic Vapor Monitors (OVMs) or SKC | |||
| Recommended sampling parameters: |
TWA Samples |
Ceiling Samples |
Peak Samples | |
| Adsorbent tubes | ||||
| Sampling rate: | 50 mL/min | 50 mL/min | 50 mL/min | |
| Sampling time: | < 240 min | > 10 min | > 1 min | |
| Diffusive samplers | ||||
| Exposure time: | < 240 min | > 10 min | Not Recommended | |
| | ||||
| Charcoal Tubes |
Anasorb®747 Tubes |
3M 3520 OVMs |
SKC Samplers | |
| Reliable quantitation limit: (240-min samples) |
18.1 ppb (68.3 µg/m3) |
25.4 ppb (95.5 µg/m3) |
82 ppb (309 µg/m3) |
224 ppb (844 µg/m3) |
| Standard error of estimate at: | ||||
| TWA: (240 min) Ceiling: (10 min) Peak: (1 min) |
5.5% 5.2% 5.2% |
5.2% 5.1% 5.4% |
7.2% 7.9% ---- |
9.2% 9.5% ---- |
| * For samples where sampling site atmospheric pressure and temperature are known. When either or both of these values are unknown, see Section 4.6 for applicable standard errors of estimate. | ||||
| Status of method: | Evaluated method. This method has been subjected to the established evaluation procedures of the Organic Methods Evaluation Branch. | |||
| Date: April 1998 | Chemist: Carl J. Elskamp | |||
OSHA Salt Lake Technical Center
Salt Lake City, UT 84115-1802
1. General Discussion
- 1.1 Background
- 1.1.1 History
The determination of toluene in air has consistently been one of the top analyses performed at the OSHA Salt Lake Technical Center (SLTC) for the last 25 years. It is based on a pioneering method developed by Otterson and Guy to determine airborne solvent vapors. (Ref. 5.1) Samples were collected by drawing air through glass tubes packed with 4 inches of 20/40 mesh activated charcoal, then desorbed with an appropriate solvent and analyzed by GC. Further developmental work was done to incorporate a flame-sealed tube containing two 1-inch sections of activated charcoal. (Ref. 5.2) Procedures for a multitude of solvents were subsequently evaluated through NIOSH based on a standardized "NIOSH charcoal tube" consisting of two sections of coconut shell activated charcoal contained in a 7-cm flame sealed glass tube. The front section contains 100 mg and the back section 50 mg of charcoal. There are at least three different methods for toluene using this sampling tube that utilize carbon disulfide (CS2) as the desorption solvent. (Refs. 5.3-5.5)
In the work presented here, tests were done to validate procedures for charcoal tubes as well as Anasorb® 747 tubes. Additional tests were done so the new method can also be used for determinations of peak and ceiling exposures to toluene. Also, the recommend sampling rate was reduced to 50 mL/min to allow samples to be taken for as long as 240 minutes, which makes it convenient to assess an all-day exposure to a worker by taking only two samples. The most significant change was in the solvent used to desorb the samples.
When air is drawn through activated charcoal tubes, a significant amount of water may be collected by adsorption along with the analytes of interest. (Ref. 5.6) The amount of water collected is dependent on the water content of the air and the volume of air sampled. Water is not very soluble in CS2, thus when samples containing excessive amounts of water are desorbed with this commonly used solvent, the desorbed water can form a separate layer. Only the CS2 layer is analyzed by GC, so if an analyte of interest is appreciably soluble in water, it will partition into the aqueous layer and the concentration of the analyte may be grossly under determined. This problem does not occur for toluene because being fairly nonpolar, it is very soluble in CS2 and only partially soluble in water. But toluene is frequently used with a mixture of solvents in workplaces, some of which may be very soluble in water. It is often desirable to analyze the mixture of solvents simultaneously from the same sample, so a solution to this problem was to use a desorption solvent that would result in a homogeneous solution that includes water after the samples are desorbed and one that would also desorb the analytes of interest with high efficiency.
A desorption solvent mixture consisting of 60/40 (v/v)
It is imperative that an internal standard procedure be used in the analysis to compensate for the water that is desorbed and put into solution. For instance, if an external standard method is used and a sample that contains 45 mg of water is desorbed with 1.00 mL of 60/40 DMF/CS2, an uncorrectable error of approximately 4.5% is introduced. The amount of water (in this case 45 mg or 0.045 mL) that was adsorbed by the adsorbent is not determined in the analysis, so a correction for the dilution of the sample by the desorbed water can not be made. In this case, the final volume of the desorption solution is approximately 1.045 mL because of the desorbed water, not 1.00 mL. The necessary correction is automatically made when an internal standard procedure is used. Not only does the internal standard procedure compensate for any desorbed water, it also compensates for the volume of any other solvents that are also desorbed, which in some cases could be quite significant.
Recently, SLTC decided to evaluate diffusive samplers for
possible alternative sampling devices for solvent vapors and gases.
Extensive work was done to help determine the evaluation tests
needed to validate this type of sampler for use by OSHA. (Ref. 5.10)
The 3M Company markets two different samplers that are widely used
for the determination of airborne solvent vapors. The 3500 Organic
Vapor Monitor (OVM) has a single carbon disk, while the 3520 OVM has
a secondary disk used as a backup sampler. By consensus decision, in
order to have a common sampler and based on the aforementioned work
done at SLTC, the 3520 OVM will be evaluated for all methods
utilizing a 3M monitor, even though in many cases the 3500 OVMs may
suffice. Also, by consensus decision, the SKC
Under very controlled conditions in the laboratory, it was found that both the 3M and SKC diffusive samplers could be used to reliably sample for as short as 1 minute, which would make them useful to determine peak exposures. But in real world situations, mostly because the samplers begin sampling as soon as they are removed from their sealed containers, it was felt that there could be too much chance for introduction of significant sampling errors. Thus the shortest recommended sampling time for toluene using diffusive samplers was determined to be 10 minutes, making them valuable tools to assess ceiling exposures, provided diligent sampling techniques are used.
1.1.2 Toxic effects (Ref 5.12) (This section is for information only and should not be taken as the basis of OSHA policy.)
Toluene is a central nervous system depressant. Exposure to very high levels (15,000 to 30,000 ppm) for a short time may cause mental confusion, loss of coordination, and unconsciousness. Exposures to 200 ppm for 8 hours caused mild fatigue, weakness, confusion, lacrimation, and paresthesias (sensation of pricking, tingling, or creeping) of the skin. Exposures to 600 ppm for 8 hours produced additional effects including euphoria, headache, dizziness, dilated pupils, and nausea while at 800 ppm for 8 hours the symptoms were more pronounced and also included nervousness, muscular fatigue, and insomnia that persisted for days.
In another study, exposure to 100 ppm for 6 hours resulted in eye and nose irritation, and in some cases, headaches, dizziness, and a feeling of intoxication, but no significant differences in performance on some neurobehavioral tests were observed. No symptoms were noted at 10 or 40 ppm exposures.
Long-term inhalational abuse by glue-sniffers resulted in chronic organic brain dysfunction associated with cerebral and cerebellar atrophy. Some studies of workers chronically exposed to toluene suggested minor abnormalities on neuropsychological testing, but a recent study of 43 rotogravure printers exposed to average concentrations of 117 ppm for an average of 22 years failed to demonstrate significant clinical neuropsychological differences compared to a control group of unexposed workers.
Exposure to toluene does not result in the hematopoietic effects caused by benzene. Most of the toluene introduced in the body by inhalation is metabolized to benzoic acid, which is conjugated with glycine in the liver to form hippuric acid. The hippuric acid is then excreted in the urine.
Repeated or prolonged skin exposure to toluene causes skin drying, fissuring, and dermatitis. Liquid splashed in the eyes of two workers caused transient corneal damage and conjunctival irritation with complete recovery within 48 hours.
Recent inhalation studies on rats exposed to levels of 600 to 1200 ppm and mice exposed to 120, 600, or 1200 ppm for two years found no evidence of carcinogenic activity.
1.1.3 Workplace exposure
Toluene is used in the manufacture of benzoic acid, benzaldehyde, explosives, dyes and many other organic compounds. It is also used as a solvent for paints, lacquers, gums, and resins and as a thinner for inks, perfumes, and dyes. It is used in the extraction of various principles from plants. It is a component in gasoline and is also used as a gasoline additive. (Ref. 5.13)
1.1.4 Physical properties (Ref. 5.13 unless otherwise noted)
| CAS number: | 108-88-3 |
| molecular weight: | 92.14 |
| boiling point: | 110.6°C |
| melting point: | -95°C |
| appearance: | colorless liquid |
| density: | 0.866 g/mL at 20°C |
| molecular formula: | C7H8 |
| vapor pressure: | 2.92 kPa (21.9 mmHg) at 20°C (Ref. 5.14) |
| flash point: | 40°F (4.4°C) (closed cup) |
| odor: | benzene-like |
| explosive limits: | 1.27-7% in air (Ref. 5.15) |
| solubility: | very slightly soluble in water [0.067% (w/w) in water at 23.5°C]; miscible with alcohol, chloroform, ether, acetone, glacial acetic acid, carbon disulfide. |
| synonyms: | methylbenzene; toluol; phenylmethane; Methacide. |
| structural formula: |  |
The analyte air concentrations throughout this method are based on the recommended sampling and analytical parameters. TWA target concentration samples are based on 240 minutes, ceiling samples on 10 minutes and peak samples on 1 minute of sampling/diffusive sampler exposure. Air concentrations listed in ppb and ppm 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 limit of the analytical procedure is 2.60 pg. This is the amount of toluene that will give an instrument response that is significantly different from the background response of a reagent blank. (Sections 4.1 and 4.2)
1.2.2 Detection limit of the overall procedure
The detection limits of the overall procedure are 246 ng per
sample (5.4 ppb or 20.5 µg/m3), 344
ng per sample (7.6 ppb or 28.7
µg/m3), 657 ng per sample (25 ppb
or 93 µg/m3) and 904 ng per sample
(67 ppb or 253 µg/m3) for charcoal
tubes, Anasorb® 747 tubes, 3M 3520 OVMs
and SKC
1.2.3 Reliable quantitation limit
The reliable quantitation limits are 820 ng per sample (18.1 ppb
or 68.3 µg/m3), 1146 ng per sample
(25.4 ppb or 95.5 µg/m3), 2190 ng
per sample (82 ppb or 309 µg/m3)
and 3012 ng per sample (224 ppb or 844
µg/m3) for charcoal tubes,
Anasorb® 747 tubes, 3M 3520 OVMs and SKC
1.2.4 Precision (analytical procedure)
The precisions of the analytical procedure, measured as the
pooled relative standard deviations from standards over
concentration ranges equivalent to 0.5 to 2 times the TWA target
concentration, are 0.76%, 0.94% and 0.76% for the adsorbent tubes,
3M 3520 OVMs and SKC
1.2.5 Precision (overall procedure)
- 1.2.5.1 Adsorbent tubes samples
The precisions of the overall procedure at the 95% confidence
level from the ambient temperature storage tests for TWA, ceiling
and peak samples for charcoal tubes and
Anasorb® 747 tubes are given in Table
1.2.5.1. The TWA samples are 240-min samples taken from 200-ppm
atmospheres, the ceiling samples are
Precision of the Overall Procedure at the 95% Confidence Interval
for Adsorbent Tubes
|
| |||
| Adsorbent | TWA Samples | Ceiling Samples | Peak Samples |
|
| |||
| Charcoal Anasorb® 747 |
±10.8% ±10.1% |
±10.2% ±10.1% |
±10.3% ±10.5% |
|
| |||
1.2.5.2 Diffusive samplers
The precisions of the overall procedure at the 95% confidence
level from the ambient temperature storage tests for TWA and
ceiling samples for 3M 3520 OVMs and SKC
Precision of the Overall Procedure at the 95% Confidence Interval
for Diffusive Samplers When Sampling Site Temperature (T)
or Atmospheric Pressure (P) are Known or Unknown
|
| ||
| Sampler | TWA Samples | Ceiling Samples |
|
| ||
| 3M 3520
OVM both T&P known only T known only P known neither T nor P known SKC both T&P known only T known only P known neither T nor P known |
±14.1% ±15.3% ±20.6% ±21.5% ±18.0% ±18.9% ±23.5% ±24.3% |
±15.5% ±16.6% ±21.7% ±22.4% ±18.6% ±19.5% ±23.9% ±24.7% |
|
| ||
1.2.6 Recovery
The recovery of toluene from TWA samples used in 19-day storage
tests remained above 99.9%, 99.5%, 102.5% and 97.3% for charcoal
tubes, Anasorb® 747 tubes, 3M 3520 OVMs
and SKC
1.2.7 Reproducibility
Six samples at the TWA target concentration for each of the four
different samplers that were collected from controlled test
atmospheres, along with a draft copy of this procedure, were
submitted to an SLTC service branch for analysis. The charcoal tube
and the 3M 3520 OVM samples were analyzed 20 days after generation
and the Anasorb® 747 tube and SKC
2. Sampling Procedure
- 2.1 Apparatus
- 2.1.1 Adsorbent tube samples
- 2.1.1.1 Samples are collected using personal sampling pumps
that have been calibrated, with sampling devices attached, to
within ±5% at the recommended flow rate of 50 mL/min. The sampling
devices consist of adsorbent tubes that are contained in
commercially available tube holders (such as SKC Inc., Fullerton,
CA, Catalog No. 222-3-1). The devices are connected to the pumps
with flexible,
2.1.1.2 Samples are collected with 7-cm × 4-mm i.d. × 6-mm o.d. glass sampling tubes packed with two sections of either coconut shell charcoal or Anasorb® 747. Anasorb® 747 is a beaded activated carbon. SKC adsorbent tubes were used in this evaluation. Charcoal tubes (Catalog No. 226-01) contain 100 mg of adsorbent in the front section and 50 mg in the back section. Anasorb® 747 tubes (Catalog No. 226-81A) contain 140 mg of adsorbent in the front section and 70 mg in the back section. The adsorbent sections are held in place with glass wool plugs and are separated by urethane foam plugs. The ends of the glass sampling tubes are heat sealed. Lot 120 charcoal and Lot 299 Anasorb® 747 tubes were used for this evaluation.
2.1.2 Diffusive samplers
- 2.1.2.1 Samples are collected with either 3M (3M Occupational
Health and Safety Products Division, St. Paul, MN) 3520 Organic
Vapor Monitors (OVMs) or SKC
2.1.2.2 A thermometer to determine the sampling site air temperature.
2.1.2.3 A barometer to determine the sampling site atmospheric pressure.
2.2 Reagents
None required
2.3 Technique
- 2.3.1 Adsorbent tubes
- 2.3.1.1 Immediately before sampling, break off the ends of the
adsorbent tube. All tubes should be from the same lot.
2.3.1.2 Connect the sampling tube to the sampling pump with
flexible,
2.3.1.3 Air being sampled should not pass through any hose or tubing before entering the sampling tube.
2.3.1.4 To avoid channeling, place the sampling tube vertically in the employee's breathing zone. Position the sampler so it does not impede work performance or safety.
2.3.1.5 After sampling for the appropriate time, immediately remove the sampling tube and seal it with plastic caps. Wrap each sample lengthwise with a Form OSHA-21 seal.
2.3.1.6 Submit at least one blank sampling tube with each sample set. Blanks should be handled in the same manner as samples, except no air is drawn through them.
2.3.1.7 Record sample volumes (in liters of air), sampling times (minutes) and sampling rate (mL/min) for each sample on Form OSHA-91A.
2.3.1.8 Also list any compounds that could be considered potential interferences, especially solvents, that are being used in the sampling area.
2.3.1.9 Ship any bulk sample(s) in a container separate from the air samples.
2.3.2 3M OVMs (In general, follow the manufacturer's instructions supplied with the samplers.)
- 2.3.2.1 The monitors come individually sealed in small metal
cans. When ready to begin sampling, remove the plastic lid from
the can and lift up on the revealed ring. Pull back on the ring to
open the can. Discard the metal top of the can and remove the
monitor. CAUTION- The monitor immediately begins to sample when
the can is unsealed.
2.3.2.2 Keep the two closure caps with attached port plugs, cup and Teflon® tubes in the can for later use. Close the can with the plastic lid.
2.3.2.3 Record the start time on the back of the monitor or on Form OSHA-91A.
2.3.2.4 Attach the monitor to the worker near his/her breathing zone with the white face forward. Assure that the area directly in front of the sampler is unobstructed throughout the sampling period. Do not remove the white film and ring from the monitor until the sampling period is terminated.
2.3.2.5 At the end of the sampling period, detach the monitor from the worker and remove the white film and retaining ring. Immediately snap a closure cap onto the primary (top) section of the monitor (where the white film and ring were removed). It is critical that this step be done as quickly as possible because the sampling rate is more than 5 times faster without the white film in place, which can be an important consideration, especially for short-term sampling. Assure that the attached port plugs are placed firmly into the port holes. The white film and ring can be discarded. Record the stop time on the back of the monitor or on Form OSHA-91A.
2.3.2.6 The following steps should be performed in a low background area for a set of monitors as soon as possible after sampling.
2.3.2.7 Ready a blank by removing the white film and ring and attaching a closure cap onto an unused monitor.
2.3.2.8 For each monitor (one at a time), separate the primary (top) and secondary (bottom) sections of the monitor using the edge of a coin as a pry.
2.3.2.9 Securely snap a cup onto the bottom of the primary section.
2.3.2.10 Snap a closure cap onto the secondary section of the monitor and assure that the attached port plugs are placed firmly into the port holes.
2.3.2.11 Return the sampler sections with closure caps and cup in place to the metal can which contains the Teflon® tubes (which will be used by the laboratory). Close the can with the plastic lid, and wrap it with a Form OSHA-21 seal.
2.3.2.12 Verify that the sampling times are properly recorded on Form OSHA-91A for each sample. Also identify blank samples on this form.
2.3.2.13 Record the room temperature and atmospheric pressure (station pressure) of the sampling site on Form OSHA-91A.
2.3.2.14 List any compounds that could be considered potential interferences, especially solvents, that are being used in the sampling area.
2.3.2.15 Submit the monitors (contained in the metal cans) to the laboratory for analysis as soon as possible.
2.3.2.16 Ship any bulk sample(s) in a container separate from the air samples.
2.3.3 SKC
- 2.3.3.1 Remove the sampler (enclosed in a clear inner package)
from the envelope. Keep the O-ring, press-on cover, cover
retainer, port plugs and Teflon® tube in
the envelope for later use.
2.3.3.2 Remove the sampler from the clear inner package when ready to begin sampling. CAUTION- The monitor immediately begins to sample when it is removed from this package.
2.3.3.3 Record the start time on the sampler label or on Form OSHA-91A.
2.3.3.4 Attach the sampler to the worker near his/her 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.
2.3.3.5 At the end of the sampling period, immediately detach the sampler from the worker and attach the cover with the O-ring in place onto the sampler using the cover retainer. Make sure the O-ring is forming a proper seal around the entire circumference of the sampler. Record the stop time on sampler label or on Form OSHA-91A.
2.3.3.6 Prepare a blank by removing an unused sampler from its clear package and immediately attaching a cover with the O-ring in place onto it.
2.3.3.7 Wrap each sampler with a Form OSHA-21 seal.
2.3.3.8 Verify that the sampling times are properly recorded on Form OSHA-91A for each sample. Also identify blank samples on this form.
2.3.3.9 Record the room temperature and atmospheric pressure (station pressure) of the sampling site on Form OSHA-91A.
2.3.3.10 List any compounds that could be considered potential interferences, especially solvents, that are being used in the sampling area.
2.3.3.11 Submit the samplers to the laboratory for analysis as soon as possible. Include all port plugs and Teflon® tubes which will be used in the laboratory analyses.
2.3.3.12 Ship any bulk sample(s) in a container separate from the air samples.
2.4 Sampler capacity (adsorbent tubes) and sampler rate/capacity (diffusive samplers)
- 2.4.1 Charcoal tubes
The sampling capacity of the front section of charcoal sampling tubes was tested by sampling from a dynamically generated test atmosphere of toluene at 401.6 ppm (1513 mg/m3). The samples were collected at a nominal flow rate of 50 mL/min and the relative humidity of the atmosphere was 73% at 29.1°C. The average 5% breakthrough volume was determined to be 16.8 L (25.4 mg or 336 min) from three determinations. (Section 4.9.1)
2.4.2 Anasorb® 747 tubes
The sampling capacity of the front section of Anasorb® 747 sampling tubes was tested by sampling from a dynamically generated test atmosphere of toluene at 401.6 ppm (1513 mg/m3). The samples were collected at a nominal flow rate of 50 mL/min and the relative humidity of the atmosphere was 73% at 29.1°C. The average 5% breakthrough volume was determined to be 20.6 L (31.1 mg or 412 min) from three determinations. (Section 4.9.2)
2.4.3 3M 3520 OVMs
The sampling rate and capacity of 3M 3520 OVMs were determined by taking samples from a dynamically generated test atmosphere of toluene (nominal concentration of 400 ppm or 1507 mg/m3) for increasing time intervals. A sampling rate of 29.54 mL/min (at 760 mmHg, 25°C) and capacity of greater than 32 mg per sample (>21.2 L or >718 min) were obtained from this test. (Section 4.9.3)
2.4.4 SKC
The sampling rate and capacity of SKC
2.5 Desorption efficiency
- 2.5.1 Charcoal tubes
- 2.5.1.1 The average desorption efficiency from charcoal tubes
over the range of 0.5 to 2 times the TWA target concentration is
99.0%. (Section 4.10.1.1)
2.5.1.2 The desorption efficiency at 0.05, 0.1 and 0.2 times the target concentration was found to be 97.4, 98.2% and 98.4% respectively. (Section 4.10.1.1)
2.5.1.3 Desorbed samples remain stable for at least 24 h. (Section 4.10.1.2)
2.5.2 Anasorb® 747 tubes
- 2.5.2.1 The average desorption efficiency from
Anasorb® 747 tubes over the range of 0.5
to 2 times the TWA target concentration is 99.1%. (Section
4.10.2.1)
2.5.2.2 The desorption efficiency at 0.05, 0.1 and 0.2 times the target concentration was found to be 97.3, 98.1% and 99.1% respectively. (Section 4.10.2.1)
2.5.2.3 Desorbed samples remain stable for at least 24 h. (Section 4.10.2.2)
2.5.3 3M OVMs
- 2.5.3.1 The average desorption efficiency from 3M OVMs over
the range of 0.5 to 2 times the TWA target concentration is 98.1%.
(Section 4.10.3.1)
2.5.3.2 The desorption efficiency at 0.05, 0.1 and 0.2 times the target concentration was found to be 98.4, 98.2% and 98.0% respectively. (Section 4.10.3.1)
2.5.3.3 Desorbed samples remain stable for at least 24 h. (Section 4.10.3.2)
2.5.4 SKC
- 2.5.4.1 The average desorption efficiency from SKC
2.5.4.2 The desorption efficiency at 0.05, 0.1 and 0.2 times the target concentration was found to be 98.0, 98.1% and 97.6% respectively. (Section 4.10.4.1)
2.5.4.3 Desorbed samples remain stable for at least 24 h. (Section 4.10.4.2)
2.6 Recommended air volume and sampling rate
- 2.6.1 When using adsorbent tubes for TWA (long-term) samples,
sample up to 12 L of air at 50 mL/min (up to 240 min). When using
diffusive samplers, sample for as long as 240 minutes.
2.6.2 When using adsorbent tubes for ceiling samples, sample greater than 0.5 L of air at 50 mL/min (greater than 10 min). When using diffusive samplers, sample for greater than 10 minutes.
2.6.3 When using adsorbent tubes for peak samples, sample at least 0.05 L of air at 50 mL/min (at least 1 min). The use of diffusive samplers is not recommended for peak samples.
2.6.4 When short-term samples are collected, the air
concentrations equivalent to the reliable quantitation limits
becomes larger. For example, the reliable quantitation limits for
charcoal tubes become 0.43 ppm (1.6 mg/m3)
for
2.7 Interferences (sampling)
- 2.7.1 The presence of other contaminants in the sampled air can
potentially reduce the capacity of all four samplers to collect
toluene. Also, the sampling rates of diffusive samplers could
possibly be altered. Interference studies were performed by sampling
for 240 minutes from a test atmosphere (10% RH, 26°C, 654.8 mmHg)
containing 396 ppm of toluene with 50 ppm of 2-butanone (MEK), 20
ppm of
2.7.2 Short-term sampling interference studies were performed for
all four samplers by sampling for 1 minute from a test atmosphere
(10% RH, 25°C, 654.3 mmHg) containing 495 ppm of toluene with 50 ppm
of 2-butanone (MEK), 20 ppm of
2.7.3 A reverse diffusion study for the diffusive samplers and a stripping study for the adsorbent tubes was performed by sampling a 402 ppm atmosphere of toluene (78% RH, 23.5°C, 649.2 mmHg) for 120 minutes with six of each samplers. Three samplers from each set were additionally subjected to 120 minutes of the same atmosphere without the toluene present to determine if any of the collected toluene diffused off of the diffusive samplers and also whether it was stripped off of the adsorbent tubes. Upon analysis of the samples, the average recovery of the removed samplers versus the average recovery of the samplers that were additionally exposed to the atmosphere without toluene was within 90% for all samplers, indicating that reverse diffusion and stripping are not significant. (Section 4.11.3)
2.7.4 The effects of sampling from relatively dry atmospheres was investigated by sampling from a 403.2-ppm toluene atmosphere (9% RH, 25.3°C, 654.5 mmHg) for 240 minutes and by sampling from a 499-ppm atmosphere (9% RH, 26.1°C, 653.9 mmHg) for 1 minute with all four samplers. Sampling from dry atmospheres did not have a significant effect on results using any of the samplers. (Section 4.11.4)
2.7.5 The effects from sampling from atmospheres containing low
concentrations of toluene was investigated by sampling from a
19.8-ppm toluene atmosphere (74% RH, 26.0°C, 651.4 mmHg) for 240
minutes and from a 49.3-ppm atmosphere (73% RH,
2.7.6 Suspected interferences should be reported to the laboratory with submitted samples.
2.8 Safety precautions (sampling)
- 2.8.1 Attach the sampling equipment to the employee so that it
will not interfere with work performance or safety.
2.8.2 Follow all safety procedures that apply to the work area being sampled.
3. Analytical Procedure
- 3.1 Apparatus
- 3.1.1 A GC equipped with a flame ionization detector. For this
evaluation, a
3.1.2 A GC column capable of separating toluene from the desorption solvent, internal standard and any interferences. A 30-m × 0.32-mm i.d. fused silica XTI-5 (bonded 5% phenyl - 95% dimethylsiloxane) capillary column with a 1.0-µm df from Restek Corporation (Bellefonte, PA) was used in this evaluation.
3.1.3 An electronic integrator or some other suitable means of measuring peak areas. A Waters MillenniumTM 2020 Networking Computer System was used in this evaluation.
3.1.4 Two-milliliter vials with Teflon®-lined caps.
3.1.5 A dispenser capable of delivering 1.0 mL of desorption solvent to prepare standards and samples. If a dispenser is not available, a 1.0-mL volumetric pipet may be used.
3.1.6 A sampler rack (SKC Cat. No. 226-04-5) and a specialized
shaker (SKC Cat. No. 226D-03-1) to facilitate the desorption of SKC
3.2 Reagents
- 3.2.1 Toluene (CAS 108-88-3), reagent grade. Baxter Burdick
& Jackson B&J BrandTM High Purity
Solvent, Lot BK583, was used in this evaluation.
3.2.2 N,N-Dimethylformamide (DMF) [CAS 68-12-2], chromatographic grade. EM Science OmniSolv®, Lot 36130, was used in this evaluation.
3.2.3 Carbon disulfide (CS2) [CAS 75-15-0], chromatographic grade. EM Science OmniSolv®, Lot 35200, was used in this evaluation.
3.2.4 A suitable internal standard, reagent grade. Supelco Neat EPA Standard, Lot LA59304, ethylbenzene (CAS 100-41-4) was used in this evaluation.
3.2.5 The desorption solvent consists of 60/40 (v/v) DMF/CS2 containing 1.0 milliliter of internal standard per liter of solution (1µL/mL).
3.2.6 GC grade nitrogen, air and hydrogen.
3.3 Standard preparation
- 3.3.1 Prepare standards by injecting microliter amounts of
toluene into vials containing 1.0 mL (for adsorbent tubes) or 2.0 mL
(for diffusive samplers) of desorption solvent delivered from the
same dispenser used to desorb samples. For example, inject 6.00
µL of toluene into a vial containing 1.0 mL of desorption
solvent. Assuming the density of toluene is 0.866 g/mL (which is
dependent on the temperature of the toluene), this standard contains
5196 µg of toluene per sample for adsorbent tube samples.
3.3.2 Bracket sample concentrations with standard concentrations. If upon analysis, sample concentrations fall outside the range of prepared standards, prepare and analyze additional standards to ascertain the linearity of instrument response or dilute high samples with desorption solvent and reanalyze the diluted samples.
3.4 Sample preparation
- 3.4.1 Adsorbent tube samples
- 3.4.1.1 Transfer each section of adsorbent from the sampling
tubes to separate labeled vials. Discard the glass tubes, urethane
foam plugs and glass wool plugs.
3.4.1.2 Add 1.0 mL of desorption solvent to each vial using the same dispenser as used for preparation of standards.
3.4.1.3 Immediately cap the vials.
3.4.1.4 Allow the adsorbent sections to desorb for 30 minutes. Periodically apply gentle agitation to the vials during the desorption period.
3.4.2 3M 3520 OVMs (In general, follow the manufacturer's instructions supplied with the samplers.)
- 3.4.2.1 Remove each sampler section from its individual metal
can, along with the sections of Teflon®
tubing. Assure that the closure caps are firmly snapped to the
primary and secondary sections of all the samplers. Also assure
that all cap plugs are firmly seated in the cap ports. Any
deviations must be noted.
3.4.2.2 Prepare one section of sampler at time by temporarily removing the cap plugs from the ports and adding 2.0 mL of desorption solvent through the center port. This is most easily done by dispensing two 1.0-mL aliquots of desorption solvent using a dispenser. Immediately replace the plugs in the ports.
3.4.2.3 Allow the sampler sections to desorb for 30 minutes. Periodically apply gentle agitation to the sampler sections during the desorption period.
3.4.2.4 Transfer the solution from each sampler section by removing both plugs from the ports, inserting a decanting spout (a small section of Teflon® tubing) into the rim port and pouring the liquid through the spout into a labeled autosampler vial. Immediately cap each vial.
3.4.3 SKC
- 3.4.3.1 Cut off the ends of the two protruding tubes of each
sampler with a razor blade or sharp knife.
3.4.3.2 Slowly add 1.0 mL of desorption solvent through one of the protruding tubes (ports). After about 30 seconds, slowly add another 1.0 mL of desorption solvent.
3.4.3.3 Immediately insert plugs into the ports.
3.4.3.4 Mount the samplers in the sampler rack (SKC Cat. No. 226-04-5) of a specialized shaker (SKC Cat. No. 226D-03-1) and shake the samplers for 1 hour.
3.5.2.5 According to the manufacturer of the sampler, do not leave the desorbed sample in the sampler. Transfer each desorbed sample by removing the plugs from the sampler ports, firmly inserting the tapered end of a supplied Teflon® tube into the outer port and carefully pouring the solution through the Teflon® tube into a labeled autosampler vial.
3.5 Analysis
- 3.5.1 GC conditions
| zone temperatures: | column- 60°C (isothermal) injector- 250°C detector- 275°C |
| gas flows: | hydrogen (carrier)- 2.5 mL/min (43 kPa head
pressure) nitrogen (makeup)- 50 mL/min hydrogen (flame)- 38 mL/min air- 450 mL/min |
| signal range: | 0 |
| injection volume: | 1.0 µL (with a 100:1 split) |
| column: | 30-m × 0.32-mm i.d. fused silica, XTI-5 1.0-µm df |
retention times:| toluene- 5.2 min | ethylbenzene- 9.8 min (internal standard) (CS2- 1.7 min, DMF- 6.1 min) |
Figure 3.5.1.1. Chromatogram of a standard near the TWA target
concentration for the adsorbent tubes. Key: (1)
CS2, (2) toluene, (3) DMF, (4)
ethylbenzene.
Figure 3.5.1.2. Chromatogram of a standard near the TWA target
concentration for 3M 3520 OVMs. Key: (1)
CS2, (2) toluene, (3) DMF, (4)
ethylbenzene.
Figure 3.5.1.3. Chromatogram of a standard near the TWA target
concentration for SKC
Figure 3.5.1.4. Chromatogram of a standard near the ceiling
concentration for the adsorbent tubes. Key: (1)
CS2, (2) toluene, (3) DMF, (4)
ethylbenzene.
Figure 3.5.1.5. Chromatogram of a standard near the ceiling
concentration for 3M 3520 OVMs. Key: (1)
CS2, (2) toluene, (3) DMF, (4)
ethylbenzene.
Figure 3.5.1.6. Chromatogram of a standard near the ceiling
concentration for SKC
Figure 3.5.1.7. Chromatogram of a standard near the peak target concentration for adsorbent tubes. Key: (1) CS2, (2) toluene, (3) DMF, (4) ethylbenzene.
3.5.2 Peak areas are measured by an integrator or other suitable means.
3.5.3 An internal standard (ISTD) calibration method is used. A calibration curve is prepared by analyzing standards and plotting micrograms of toluene per sample versus ISTD-corrected area counts of the toluene peaks. Sample concentrations must be bracketed by standards.
Figure 3.5.3.1. Calibration curve for adsorbent tubes constructed
from the data in Table 4.5. The equation of the line is Y =
150.7X-15400.
Figure 3.5.3.2. Calibration curve for 3M 3520 OVMs constructed
from the data in Table 4.5.2. The equation of the line is Y =
74.93X+1609.
Figure 3.5.3.3. Calibration curve for SKC
3.6 Interferences (analytical)
- 3.6.1 Any compound that produces a response on a flame
ionization detector and has the same general retention time of
toluene or the internal standard is a potential interference.
Possible interferences should be reported to the laboratory with
submitted samples by the industrial hygienist. These interferences
should be considered before samples are desorbed.
3.6.2 GC parameters (i.e. column and column temperature) may be changed to possibly circumvent interferences.
3.6.3 The desorption efficiency from wet samplers was investigated by spiking samplers with amounts of toluene equivalent to the mass that would be collected for 240 minutes from atmospheres containing 200 ppm. Before being spiked with toluene, humid air (~80% RH, 25°C) had been drawn through the adsorbent tubes at 50 mL/min for 240 minutes. Similarly, the diffusive samplers had been exposed to the humid atmosphere for 240 minutes. The desorption efficiencies were comparable to those reported in Section 2.5. (Section 4.12)
3.6.4 When necessary, the identity or purity of an analyte peak may be confirmed with additional analytical data. (Section 4.13)
3.7 Calculations
- 3.7.1 Adsorbent tube samples
The toluene concentration for samples is obtained from the appropriate calibration curve in terms of micrograms of toluene per sample, uncorrected for desorption efficiency. The air concentration is calculated using the following formulae. The back (50-mg) section is analyzed primarily to determine if there was any breakthrough from the front section during sampling. If a significant amount of analyte is found on the back section (e.g., greater than 25% of the amount found on the front section), this fact should be reported with sample results. If any analyte is found on the back section, it is added to the amount found on the front section. This total amount is then corrected by subtracting the total amount (if any) found on the blank.
mg/m3 = (µg of toluene per sample)/((L of air sampled)(desorption efficiency))
| where: | desorption efficiency = 0.990 for Charcoal and
0.991 for Anasorb® 747 Tubes L of air sampled = [(sampling time, min)(sampling rate, mL/min)]/1000 |
ppm = (mg/m3)(24.46)/(molecular weight of analyte) = (mg/m3)(0.2655)
| where: | 24.46 is the molar volume at 25°C and 101.3 kPa
(760 mmHg) and the molecular weight of toluene = 92.14 |
3.7.2 3M 3520 OVMs and SKC
The toluene concentration for samples is obtained from the appropriate calibration curve in terms of micrograms of toluene per sample, uncorrected for desorption efficiency. The air concentration is calculated using the following formulae. For the 3M OVMs, the back section is analyzed primarily to determine if there was any breakthrough from the front section during sampling. If a significant amount of analyte is found on the back section (e.g., greater than 25% of the amount found on the front section), this fact should be reported with sample results. If any analyte is found on the back section, the amount found is multiplied by 2.2 (as per manufacturer's instructions) and then added to the amount found on the corresponding front section. This total amount is then corrected by subtracting the total amount (if any) found on the blank.
mg/m3 = (µg of toluene per sample)/((L of air sampled)(desorption efficiency))
| where: | desorption efficiency = 0.981 for 3M OVMs and
0.970 for SKC L of air sampled = [(sampling time, min)(sampling rate, mL/min)]/1000 Sampling rate (3M OVMs) = (29.54)(760/P)(T/298.2)1.5 Sampling rate (SKC P = the sampling site pressure (mmHg) T = the sampling site temperature (K) |
ppm = (mg/m3)(24.46)/(molecular weight of analyte) = (mg/m3)(0.2655)
| where: | 24.46 is the molar volume at 25°C and 101.3 kPa
(760 mmHg) and the molecular weight of toluene = 92.14 |
If the sampling site temperature is not provided, assume that it
is 22.2°C (295.4 K,
P = (3.3887 × 10-7)(E2) B (2.7468 × 10-2)(E) + 760
| Where | P = the calculated approximate atmospheric
pressure (mmHg) E = the sampling site elevation (ft) |
Figure 3.7.2 Plot of atmospheric pressure versus altitude. Data taken from Reference 5.16.
3.8 Safety precautions (analytical)
- 3.8.1 Adhere to the rules set down in your Chemical Hygiene
Plan.
3.8.2 Avoid skin contact and inhalation of all chemicals.
3.8.3 Wear safety glasses and a lab coat at all times while in the lab area.
4. Backup Data
- 4.1 Determination of detection limits
Detection limits (DL), in general, are defined as the amount (or concentration) of analyte that gives an instrument response (YDL) that is significantly different (three standard deviations (SDBR)) from the background response (YBR).
The direct measurement of YBR and SDBR in chromatographic methods is typically inconvenient and difficult because YBR is usually extremely low. Estimates of these parameters can be made with data obtained from the analysis of a series of analytical standards or samples whose responses are in the vicinity of the background response. The regression curve obtained for a plot of instrument response versus concentration of analyte will usually be linear. Assuming SDBR and the precision of data about the curve are similar, the standard error of estimate (SEE) for the regression curve can be substituted for SDBR in the above equation. The following calculations derive a formula for DL:
| Yobs | = observed response |
| Yest | = estimated response from regression curve |
| n | = total no. of data points |
| k | = 2 for a linear regression curve |
At point YDL on the regression curve
| YDL = A(DL) + YBR | A = analytical sensitivity (slope) |
therefore
| DL = | (YDL - YBR)
A |
Substituting 3(SEE) + YBR for YDL gives
| DL = | 3(SEE)
A |
4.2 Detection limit of the analytical procedure (DLAP)
The DLAP is measured as the mass of analyte introduced into the chromatographic column. Ten analytical standards were prepared in equal descending increments with the highest standard containing 4325 ng of toluene per mL. This standard produces a peak approximately 10 times the baseline noise of a reagent blank when a 1-µL injection with a 1:100 split is made onto the GC column. Standards, plus a reagent blank, were analyzed and the data obtained were used to determine the required parameters (A and SEE) for the calculation of the DLAP. Values of 17.66 and 15.3 were obtained for A and SEE respectively. The DLAP was calculated to be 2.60 pg.
DLAP for Toluene
|
| ||
| concentration (ng/mL) |
mass on column (pg) |
peak
area (µV·s) |
|
| ||
| 0.000 432.5 865.0 1298 1730 2162 2595 3028 3460 3892 4325 |
0.00 4.325 8.650 12.98 17.30 21.62 25.95 30.28 34.60 38.92 43.25 |
0 92.7 167 226 338 368 456 547 641 696 761 |
|
| ||
Figure 4.2. Plot of data from Table 4.2. to determine the DLAP. The
equation of the line is
Y = 17.66X + 8.40.
4.3 Detection limit of the overall procedure (DLOP)
The DLOP is measured as mass per sample and expressed as equivalent
air concentrations, based on the recommended sampling parameters. Ten
samplers of each type were spiked with equal descending increments of
toluene such that the highest sampler loadings were 4325 ng/sample for
the adsorbent tubes and 8650 ng/sample for the 3M 3520 OVMs and SKC
samplers. (The diffusive samplers were spiked with twice the amounts
of toluene compared to adsorbent tubes because they are desorbed with
2 mL of solvent versus 1 mL for the adsorbent tubes.) These are the
amounts, when spiked on the samplers, that would produce peaks
approximately 10 times the baseline noise for sample blanks. These
spiked samplers, plus blanks, were analyzed with the recommended
analytical parameters, and the data obtained used to calculate the
required parameters (A and SEE) for the calculation of the DLOPs.
Values of 0.1768 and 14.5, 0.1745 and 20.0, 0.0831 and 18.2, and
0.0943 and 28.4 were obtained for A and SEE for charcoal tubes,
Anasorb® 747 tubes, 3M 3520 OVMs and SKC
Detection Limit of the Overall Procedure
for Charcoal Tubes
|
| |
| mass (ng) per sample |
peak
area (µV·s) |
|
| |
| 0.0 432.5 865.0 1298 1730 2162 2595 3028 3460 3892 4325 |
0 90.1 162 244 322 386 491 518 639 686 776 |
|
| |
Figure 4.3.1. Plot of data from Table 4.3.1 to determine the
DLOP/RQL for charcoal tubes. The equation of the line is Y = 0.1768X +
9.83.
Detection Limit of the Overall Procedure
for Anasorb® 747 Tubes
|
| |
| mass (ng) per sample |
peak
area (µV·s) |
|
| |
| 0.0 432.5 865.0 1298 1730 2162 2595 3028 3460 3892 4325 |
0 130 168 254 308 429 488 579 626 694 768 |
|
| |
Figure 4.3.2. Plot of data from Table 4.3.2. to determine the
DLOP/RQL for Anasorb® 747 tubes. The
equation of the line is Y = 0.1745X + 26.7.
Detection Limit of the Overall Procedure
for 3M 3520 OVMs
|
| |
| mass (ng) per sample |
peak
area (µV·s) |
|
| |
| 0.0 865 1730 2595 3460 4325 5190 6055 6920 7785 8650 |
0 91.1 146 209 304 370 455 546 599 646 700 |
|
| |
Figure 4.3.3. Plot of data from Table 4.3.3. to determine the
DLOP/RQL for 3M 3520 OVMs. The equation of the line is Y = 0.0831X +
10.4.
Detection Limit of the Overall Procedure
for SKC
|
| |
| mass (ng) per sample |
peak
area (µV·s) |
|
| |
| 0.0 865 1730 2595 3460 4325 5190 6055 6920 7785 8650 |
0 95.1 195 223 307 423 556 588 639 730 813 |
|
| |
Figure 4.3.4. Plot of data from Table 4.3.4 to determine the
DLOP/RQL for SKC
4.4 Reliable quantitation limit (RQL)
The RQL is considered the lower limit for precise quantitative measurements. It is determined from the regression line data obtained for the calculation of the DLOP (Section 4.3). The RQL is defined as the amount of analyte that gives an instrument response (YRQL) such that
therefore
| RQL = | 10(SEE)
A |
The RQLs were calculated to be 820 ng per sample (18.1 ppb or 68.3
µg/m3), 1146 ng per sample (25.4 ppb
or 95.5 µg/m3), 2190 ng per sample
(82 ppb or 309 µg/m3) and 3012 ng per
sample (224 ppb or 844 µg/m3) for
charcoal tubes, Anasorb® 747 tubes, 3M 3520
OVMs and SKC
Figure 4.4.1. Chromatogram of a sample (865 ng of toluene per
sample) near the RQL for charcoal tubes (820 ng). Key: (1)
CS2, (2) toluene, (3) DMF and impurities,
(4) ethylbenzene.
Figure 4.4.2. Chromatogram of a sample (1298 ng of toluene per
sample) near the RQL for Anasorb® (1146 ng).
Key: (1) CS2, (2) toluene, (3) DMF and
impurities, (4) ethylbenzene.
Figure 4.4.3. Chromatogram of a sample (2595 ng of toluene per
sample) near the RQL for 3M 3520 OVMs (2190 ng). Key: (1)
CS2, (2) toluene, (3) DMF and impurities,
(4) ethylbenzene.
Figure 4.4.4. Chromatogram of a sample (1298 ng of toluene per
sample) near the RQL for SKC
4.5 Precision (analytical method)
The precisions of the analytical procedure are defined as the
pooled relative standard deviations (RSDP).
Relative standard deviations were determined from six replicate
injections of standards at 0.5, 0.75, 1, 1.5 and 2 times the TWA
target concentrations. After assuring that the RSDs satisfy the
Cochran test for homogeneity at the 95% confidence level, the
RSDPs were calculated to be 0.76%, 0.94% and
0.76% for the adsorbent tubes, 3M 3520 OVMs and SKC
Instrument Response for Adsorbent Tubes
|
| |||||
| × target
concn (µg/sample) |
0.5× 4541.2 |
0.75× 6920.0 |
1.0× 9082.5 |
1.5× 13840 |
2.0× 18165 |
|
| |||||
| peak
areas (µV·s) |
672250 679710 676130 686650 667840 676290 |
1030700 1024500 1033400 1035000 1029400 1033100 |
1388800 1382300 1358700 1375800 1372900 1374800 |
2034600 2055000 2092000 2060800 2093000 2069600 |
2718600 2737100 2744500 2729200 2734000 2744000 |
| mean SD RSD (%) |
676479 6427.5 0.950 |
1031017 3770.1 0.366 |
1375550 10126.2 0.736 |
2067500 22532.0 1.090 |
2734567 9778.9 0.358 |
|
| |||||
Instrument Response for 3M 3520 OVMs
|
| |||||
| × target
concn (µg/sample) |
0.5× 2681.5 |
0.75× 4022.2 |
1.0× 5363 |
1.5× 8044.5 |
2.0× 10726 |
|
| |||||
| peak
areas (µV·s) |
204130 200620 202700 198390 201720 201940 |
305410 302040 304170 03280 307530 300290 |
407980 399910 400930 406990 404850 404490 |
605690 595360 601140 608650 606270 606280 |
811630 808570 810300 803260 811770 786360 |
| mean SD RSD (%) |
201584 1949.6 0.967 |
303787 2542.8 0.837 |
404192 3214.82 0.795 |
603899 4849.7 0.803 |
805315 9803.1 1.217 |
|
| |||||
Instrument Response for SKC
|
| |||||
| × target
concn (µg/sample) |
0.5× 1340.8 |
0.75× 2011.1 |
1.0× 2681.5 |
1.5× 4022.2 |
2.0× 5363 |
|
| |||||
| peak
areas (µV·s) |
100120 100800 100590 100320 100050 100100 |
151260 150640 149190 151860 150840 152170 |
204130 200620 202700 198390 201720 201940 |
305410 302040 304170 303280 307530 300290 |
407980 399910 400930 406990 404850 404490 |
| mean SD RSD (%) |
100330 304.6 0.304 |
150994 1059.0 0.701 |
201584 1949.6 0.967 |
303787 2542.8 0.837 |
404192 3214.8 0.795 |
|
| |||||
The Cochran test for homogeneity:
The g statistics are 0.410, 0.337 and 0.328 for the
adsorbent tubes, 3M 3520 OVMs and SKC
4.6 Precision (overall procedure)
The precision of the overall procedure is determined from the storage data in Section 4.7. The determination of the standard error of estimate (SEER) for a regression line plotted through the graphed storage data allows the inclusion of storage time as one of the factors affecting overall precision. The SEER is similar to the standard deviation, except it is a measure of dispersion of data about a regression line instead of about a mean. It is determined with the following equation:
| n | = | total no. of data points |
| k | = | 2 for linear regression |
| k | = | 3 for quadratic regression |
| Yobs | = | observed % recovery at a given time |
| Yest | = | estimated % recovery from the regression line at the same given time |
The following formula is used to determine the total standard error of estimate (SEE) for adsorbent tubes. An additional 5% for pump error (SP) is added to the SEER by the addition of variances.
The following formula is used to determine the total standard error of estimate (SEE) for diffusive samplers when the sampling site temperature and pressure are known. SR is the sampling rate variability that has been determined in separate studies to be 6.4% for 3M OVMs and 8.7% for SKC samplers. (Refs. 5.10 and 5.17)
The following formula is used when the sampling site temperature or
pressure are not known. Additional variances are included that account
for uncertainty for uncorrected temperature (ST) and pressure (SPr)
effects on the sampling rate. When the temperature is unknown, it will
be assumed that it is 22.2°C (295.4 K,
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). The 95% confidence intervals are drawn about their respective regression lines in the storage graphs, as shown in the figures in Section 4.7. The SEEs and precisions of the overall procedure are given in the following tables for adsorbent tubes and diffusive samplers. All values are based on the ambient storage tests in Section 4.7.
SEEs and Precisions of the Overall Procedure at the 95% Confidence Interval
for Adsorbent Tubes
|
| ||||||
| TWA Samples | Ceiling Samples | Peak Samples | ||||
| Adsorbent |
| |||||
| SEE | Precision | SEE | Precision | SEE | Precision | |
|
| ||||||
| Charcoal Anasorb® 747 |
5.51% 5.15% |
±10.8% ±10.1% |
5.20% 5.14% |
±10.2% ±10.1% |
5.25% 5.36% |
±10.3% ±10.5% |
|
| ||||||
SEEs and Precisions of the Overall Procedure at the 95% Confidence Interval
for Diffusive Samplers When Sampling Site Temperature (T)
or Atmospheric Pressure (P) are Known or Unknown
|
| ||||
| TWA Samples | Ceiling Samples | |||
| Sampler |
| |||
| SEE | Precision | SEE | Precision | |
|
| ||||
| 3M 3520
OVM both T&P known only T known only P known neither T nor P known SKC both T&P known only T known only P known neither T nor P known |
7.19% 7.79% 10.5% 11.0% 9.18 9.66 12.0% 12.4% |
±14.1% ±15.3% ±20.6% ±21.5% ±18.0% ±18.9% ±23.5% ±24.3% |
7.93% 8.48% 11.1% 11.5% 9.49% 9.95% 12.2% 12.6% |
±15.5% ±16.6% ±21.7% ±22.4% ±18.6% ±19.5% ±23.9% ±24.7% |
|
| ||||
4.7 Storage tests
Adsorbent tube storage samples were prepared by sampling at 50
mL/min from controlled test atmospheres that were at approximately 80%
RH and at room temperatures ranging from
TWA Storage Tests for Charcoal Tubes
|
| |||||||
| time (days) | refrigerated
storage recovery (%) |
ambient
storage recovery (%) | |||||
|
| |||||||
| 0 0 3 6 11 14 19 |
100.6 102.8 99.7 101.7 99.8 99.4 98.1 |
102.0 100.4 99.1 101.3 100.4 101.4 99.5 |
99.9 101.3 101.4 101.3 99.4 99.9 100.8 |
100.6 102.8 100.2 100.0 99.5 99.6 100.3 |
102.0 100.4 90.7 99.7 100.1 99.8 99.8 |
99.9 101.3 99.2 100.2 100.1 100.6 100.8 | |
|
| |||||||
Figure 4.7.1.1. Charcoal tubes refrigerated storage test,
240-minute samples at 200 ppm.
Figure 4.7.1.2. Charcoal tubes ambient storage test, 240-minute
samples at 200 ppm.
TWA Storage Tests for Anasorb® 747 Tubes
|
| |||||||
| time (days) | refrigerated
storage recovery (%) |
ambient
storage recovery (%) | |||||
|
| |||||||
| 0 0 3 6 11 14 19 |
100.2 100.7 100.4 100.2 100.6 103.3 100.9 |
100.5 100.0 100.3 99.6 99.2 101.2 100.6 |
99.8 95.6 99.9 100.6 101.0 103.8 100.3 |
100.2 100.7 98.6 99.9 99.2 100.7 99.3 |
100.5 100.0 101.5 99.4 100.1 101.6 101.6 |
99.8 95.6 99.5 100.2 100.4 100.6 101.5 | |
|
| |||||||
Figure 4.7.2.1. Anasorb® 747 tubes
refrigerated storage test, 240-minute samples at 200 ppm.
Figure 4.7.2.2. Anasorb® 747 tubes
ambient storage test, 240-minute samples at 200 ppm.
TWA Storage Tests for 3M 3520 OVMs
|
| |||||||
| time (days) | refrigerated
storage recovery (%) |
ambient
storage recovery (%) | |||||
|
| |||||||
| 0 0 3 6 11 14 19 |
105.0 104.3 101.9 103.9 103.1 104.3 105.2 |
100.7 102.4 99.1 104.6 107.2 104.0 102.6 |
104.4 99.7 101.9 100.9 103.8 101.0 101.4 |
105.0 104.3 107.9 98.1 99.0 109.6 111.0 |
100.7 102.4 102.7 105.8 102.9 102.1 107.9 |
104.4 99.7 103.9 104.3 101.3 104.4 104.4 | |
|
| |||||||
Figure 4.7.3.1. 3M 3520 OVMs refrigerated storage test, 240-minute
samples at 200 ppm.
Figure 4.7.3.2. 3M 3520 OVMs ambient storage test, 240-minute
samples at 200 ppm.
TWA Storage Tests for SKC
|
| |||||||
| time (days) | refrigerated
storage recovery (%) |
ambient
storage recovery (%) | |||||
|
| |||||||
| 0 0 3 6 11 14 19 |
100.3 99.8 100.1 91.2 101.1 97.4 101.0 |
95.8 97.8 97.3 92.3 95.8 98.8 101.3 |
102.6 96.3 99.2 98.5 93.9 97.8 90.6 |
100.3 99.8 97.0 95.9 100.2 100.2 100.2 |
95.8 97.8 94.9 96.5 91.4 102.2 95.7 |
102.6 96.3 94.9 94.8 99.9 100.6 99.9 | |
|
| |||||||
Figure 4.7.4.1. SKC
Figure 4.7.4.2. SKC
Ceiling Storage Tests for Adsorbent Tubes
|
| |||||||
| time (days) | Charcoal recovery (%) |
Anasorb® 747 recovery (%) | |||||
|
| |||||||
| 0 0 3 6 10 12 15 |
97.9 99.2 99.9 97.3 98.5 97.0 98.8 |
99.7 98.6 100.2 94.7 97.1 99.4 98.0 |
101.4 99.7 97.2 98.0 100.0 97.5 98.4 |
98.0 100.9 97.4 97.4 97.7 98.0 97.1 |
98.0 100.9 99.7 97.1 98.9 99.2 98.5 |
99.5 98.0 97.7 96.4 96.6 97.6 98.0 | |
|
| |||||||
Figure 4.7.5.1. Charcoal tubes ambient storage test,
Figure 4.7.5.2. Anasorb® 747 tubes
ambient storage test,
Ceiling Storage Tests for Diffusive Samplers
|
| |||||||
| time (days) | 3M 3520 OVMs recovery (%) |
SKC recovery (%) | |||||
|
| |||||||
| 0 0 3 6 10 12 15 |
110.8 102.5 102.7 103.6 101.8 100.0 96.7 |
111.6 101.6 100.8 99.4 102.7 95.6 100.8 |
96.9 101.8 104.4 100.7 111.7 94.2 106.0 |
98.8 90.5 97.6 ?99.8 93.9 90.2 94.6 |
94.3 94.6 100.7 99.2 96.6 92.4 98.2 |
97.3 87.7 93.5 89.3 92.2 97.2 92.0 | |
|
| |||||||
Figure 4.7.6.1. 3M 3520 OVMs ambient storage test,
Figure 4.7.6.2. SKC
Peak Storage Tests for Adsorbent Tubes
|
| |||||||
| time (days) | Charcoal Tubes recovery (%) |
Anasorb® 747
Tubes recovery (%) | |||||
|
| |||||||
| 0 0 3 6 10 12 15 |
96.1 98.0 95.5 92.0 95.0 95.3 96.6 |
94.9 99.7 96.5 94.4 95.0 95.2 95.9 |
97.8 95.1 93.8 94.1 94.8 95.8 94.3 |
95.3 97.5 97.9 95.2 96.4 97.4 90.7 |
98.2 97.5 97.6 95.0 96.5 99.0 96.8 |
99.3 96.8 99.4 95.7 93.0 95.1 96.7 | |
|
| |||||||
Figure 4.7.7.1. Charcoal tubes ambient storage test, 1-minute
samples at 500 ppm.
Figure 4.7.7.2. Anasorb® 747 tubes ambient storage test, 1-minute samples at 500 ppm.
4.8 Reproducibility
Six TWA reproducibility samples for each of the four types of
samplers were prepared by collecting them from a controlled test
atmosphere similar to that which was used in the collection of the
storage samples in Section 4.7. The samples were submitted to an SLTC
service branch for analysis. The charcoal tube and 3M 3520 OVM samples
were analyzed 20 days after generation and the
Anasorb® 747 tube and SKC
Reproducibility Data for Charcoal Tubes
|
| ||||
| sample no. |
ppm reported |
ppm expected |
percent found |
deviation (%) |
|
| ||||
| 1 2 3 4 5 6 |
183.0 183.1 183.8 180.5 183.0 182.2 |
197.1 197.1 197.1 197.1 197.1 197.1 |
92.8 92.9 93.3 91.6 92.8 92.4 |
-7.2 -7.1 -6.7 -8.4 -7.2 -7.6 |
|
| ||||
Reproducibility Data for Anasorb® 747 Tubes
|
| ||||
| sample no. |
ppm reported |
ppm expected |
percent found |
deviation (%) |
|
| ||||
| 1 2 3 4 5 6 |
197.8 197.6 197.4 198.2 194.2 199.1 |
201.1 201.1 201.1 201.1 201.1 201.1 |
98.4 98.3 98.2 98.6 96.6 99.0 |
-1.6 -1.7 -1.8 -1.4 -3.4 -1.0 |
|
| ||||
Reproducibility Data for 3M 3520 OVMs
|
| ||||
| sample no. |
ppm reported |
ppm expected |
percent found |
deviation (%) |
|
| ||||
| 1 2 3 4 5 6 |
197.7 193.4 192.6 197.1 195.6 199.1 |
197.1 197.1 197.1 197.1 197.1 197.1 |
100.3 98.1 97.7 100.0 99.2 101.0 |
+0.3 -1.9 -2.3 0.0 -0.8 +1.0 |
|
| ||||
Reproducibility Data for SKC
|
| ||||
| sample no. |
ppm reported |
ppm expected |
percent found |
deviation (%) |
|
| ||||
| 1 2 3 4 5 6 |
207.9 213.0 208.1 206.8 191.7 209.7 |
201.1 201.1 201.1 201.1 201.1 201.1 |
103.4 105.9 103.5 102.8 95.3 104.3 |
+3.4 +5.9 +3.5 +2.8 -4.7 +4.3 |
|
| ||||
4.9 Sampler capacity and sampling rate
- 4.9.1 Charcoal tubes
The sampling capacity of the front section of charcoal sampling tubes was tested by sampling from a dynamically generated test atmosphere of toluene at 401.6 ppm (1513 mg/m3). The samples were collected at a nominal flow rate of 50 mL/min and the relative humidity of the atmosphere was 73% at 29.1°C. Complete charcoal tubes were placed in-line behind the front test sections and changed at measured intervals. The average 5% breakthrough volume was determined to be 16.8 L from three determinations.
Breakthrough of Toluene with
Charcoal Sampling Tubes
|
| ||||
| smplr tube no. | air vol (L) | sampling time (min) | downstream concn (mg/m3) | break-through (%) |
|
| ||||
| 1 2 3 |
5.50 12.56 15.71 18.84 21.99 25.13 5.28 12.77 15.96 19.15 22.34 25.54 5.25 11.97 14.97 17.96 20.95 23.95 |
0-210 210-270 270-330 330-390 390-450 450-510 0-210 210-270 270-330 330-390 390-450 450-510 0-210 210-270 270-330 330-390 390-450 450-510 |
0 0 9.68 410.6 1301 1461 0 0.63 9.75 406.4 1273 1424 0 0 4.65 248.8 1136 1495 |
0 0 0.64 27.1 86.0 96.6 0 0.04 0.65 26.9 84.1 94.1 0 0 0.31 16.4 75.1 98.8 |
|
| ||||
Figure 4.9.1. Determination of the 5% breakthrough volume for charcoal tubes.
4.9.2 Anasorb® 747 tubes
The sampling capacity of the front section of Anasorb® 747 sampling tubes was tested by sampling from a dynamically generated test atmosphere of toluene at 401.6 ppm (1513 mg/m3). The samples were collected at a nominal flow rate of 50 mL/min and the relative humidity of the atmosphere was 73% at 29.1°C. Complete Anasorb® 747 tubes were placed in-line behind the front test sections and changed at measured intervals. The average 5% breakthrough volume was determined to be 20.6 L from three determinations.
Breakthrough of Toluene with
Anasorb® 747 Sampling Tubes
|
| ||||
| smplr tube no. | air vol (L) | sampling time (min) | downstream concn (mg/m3) | break-through (%) |
|
| ||||
| 1 2 3 |
5.06 11.56 14.45 17.34 20.24 23.13 5.65 12.91 16.13 19.36 22.59 25.81 5.28 12.06 15.07 18.09 21.10 24.11 |
0-210 210-270 270-330 330-390 390-450 450-510 0-210 210-270 270-330 330-390 390-450 450-510 0-210 210-270 270-330 330-390 390-450 450-510 |
0 0 0.28 4.67 40.9 198.9 0 0 1.05 26.6 192.3 830.3 0 0 1.73 20.9 100.2 352.5 |
0 0 0.02 0.31 2.70 13.2 0 0 0.07 1.76 12.7 32.2 0 0 0.11 1.38 6.62 14.6 |
|
| ||||
Figure 4.9.2. Determination of the 5% breakthrough volume for Anasorb® 747 tubes.
4.9.3 3M 3520 OVMs
The sampling rate and capacity of 3M 3520 OVMs was determined by taking samples from a dynamically generated test atmosphere of toluene (nominal concentration of 400 ppm or 1507 mg/m3) for increasing time intervals. The atmosphere was at approximately 75% relative humidity, 29°C and 647 mmHg. The flow of the atmosphere through the exposure chamber provided for face velocities on the diffusive samplers of approximately 0.4 m/s. The data obtained are shown in Table 4.9.3 and Figure 4.9.3. Three samples were taken for each sampling interval. Sampler capacity is exceeded when the sampling rate decreases rapidly. Because this did not occur for the time period tested, the capacity is estimated to be greater than 32 mg. A sampling rate standardized to 760 mmHg and 25°C of 29.54 mL/min was determined to be average sample rate from samples collected from 7.5 to 240 minutes.
Sampling Rate and Capacity
for Toluene using 3M 3520 OVMs
|
| ||
| sampling
time (min) |
sampling
rate (mL/min) |
RSD (%) |
|
| ||
| 7.5 15 30 60 120 240 362 481 600 720 |
30.92 29.79 29.37 29.93 28.99 28.25 28.60 27.93 29.61 27.52 |
2.12 2.28 0.71 3.10 0.38 3.68 3.11 0.69 0.84 2.17 |
|
| ||
Figure 4.9.3. Determination of sampling rate and capacity for toluene using 3M 3520 OVMs.
4.9.4 SKC
The sampling rate and capacity of the SKC
Sampling Rate and Capacity
for Toluene using SKC 575-002 Samplers
|
| ||
| sampling
time (min) |
sampling
rate (mL/min) |
RSD (%) |
|
| ||
| 7.5 15 30 60 120 245 360 480 600 720 |
15.25 14.90 14.90 14.78 14.47 15.02 14.90 14.93 15.13 14.67 |
2.13 1.02 1.08 2.48 3.38 1.48 2.19 2.62 1.56 1.55 |
|
| ||
Figure 4.9.4. Determination of sampling rate and capacity for
toluene using SKC
4.10 Desorption efficiency
- 4.10.1 Charcoal tubes
- 4.10.1.1 The desorption efficiency (DE) of toluene was
determined by
Desorption Efficiency of Toluene from Charcoal Tubes
|
| ||||||
| × target concn mass spiked (µg) |
0.05× 451.5 |
0.1× 903.9 |
0.2× 1807.8 |
0.5× 4515.3 |
1.0× 9039.2 |
2.0× 18078 |
|
| ||||||
| DE (%) |
96.9 97.7 97.9 97.4 97.3 97.4 |
97.8 98.0 98.9 98.4 97.8 98.2 |
98.0 98.9 98.9 98.4 98.6 97.9 |
98.3 98.9 98.4 98.1 98.6 98.0 |
100.2 99.2 99.8 99.3 98.7 98.2 |
98.9 100.4 98.8 99.0 100.4 98.2 |
 |
97.4 | 98.2 | 98.4 | 98.4 | 99.2 | 99.3 |
|
| ||||||
4.10.1.2 Stability of desorbed charcoal tubes samples
The stability of desorbed samples was investigated by reanalyzing the target concentration samples 24 h after initial analysis. After the original analysis was performed three vials were recapped with new septa while the remaining three retained their punctured septa. The samples were reanalyzed with fresh standards. The average percent change was -0.5% for samples that were resealed with new septa and -1.5% for those that retained their punctured septa.
Stability of Desorbed Charcoal Tube Samples
|
| |||||
| punctured septa replaced | punctured septa retained | ||||
| initial DE (%) |
DE after one day (%) |
difference |
initial DE (%) |
DE after one day (%) |
difference |
|
| |||||
| 100.2 99.2 99.8 99.7 |
99.7 99.0 99.1 (averages) 99.3 |
-0.5 -0.2 -0.7 -0.5 |
99.3 98.7 98.2 98.7 |
97.7 97.0 97.0 (averages) 97.2 |
-1.6 -1.7 -1.2 -1.5 |
|
| |||||
4.10.2 Anasorb® 747 tubes
- 4.10.2.1 The desorption efficiency (DE) of toluene was
determined by
Desorption Efficiency of Toluene from Anasorb® 747 Tubes
|
| ||||||
| × target concn mass spiked (µg) |
0.05× 451.5 |
0.1× 903.9 |
0.2× 1807.8 |
0.5× 4515.3 |
1.0× 9039.2 |
2.0× 18078 |
|
| ||||||
| DE (%) |
96.2 98.9 97.6 97.8 95.9 97.4 |
98.2 98.6 98.1 98.1 97.4 98.2 |
99.2 99.0 99.5 99.4 98.8 99.0 |
99.5 99.0 98.7 98.9 98.9 98.9 |
98.9 99.6 99.6 98.3 98.7 99.1 |
97.2 99.6 98.8 99.4 100.7 99.7 |
|
97.3 | 98.1 | 99.2 | 99.0 | 99.0 | 99.2 |
|
| ||||||
4.10.2.2 Stability of desorbed Anasorb® 747 tube samples
The stability of desorbed samples was investigated by reanalyzing the target concentration samples 24 h after initial analysis. After the original analysis was performed three vials were recapped with new septa while the remaining three retained their punctured septa. The samples were reanalyzed with fresh standards. The average percent change was -0.6% for samples that were resealed with new septa and -1.5% for those that retained their punctured septa.
Stability of Desorbed Anasorb® 747 Tube Samples
|
| |||||
| punctured septa replaced | punctured septa retained | ||||
| initial DE (%) |
DE after one day (%) |
difference |
initial DE (%) |
DE after one day (%) |
difference |
|
| |||||
| 98.9 99.6 99.6 99.4 |
97.8 99.2 99.4 (averages) 98.8 |
-1.1 -0.4 -0.2 -0.6 |
98.3 98.7 99.1 98.7 |
97.2 97.0 97.5 (averages) 97.2 |
-1.1 -1.7 -1.6 -1.5 |
|
| |||||
4.10.3 3M 3520 OVMs
- 4.10.3.1 The desorption efficiency (DE) of toluene was
determined by
Desorption Efficiency of Toluene from 3M 3520 OVMs
|
| ||||||
| × target concn mass spiked (µg) |
0.05× 259.5 |
0.1× 519.0 |
0.2× 1038 |
0.5× 2595 |
1.0× 5190 |
2.0× 10380 |
|
| ||||||
| DE (%) |
99.4 97.9 98.2 98.2 98.6 98.4 |
98.0 98.4 99.1 98.3 98.0 97.5 |
98.1 98.5 98.1 98.4 97.8 97.3 |
98.0 98.3 97.8 99.4 98.0 97.7 |
98.3 97.7 97.8 97.8 98.2 98.5 |
98.0 98.0 98.2 97.8 98.1 98.0 |
|
98.4 | 98.2 | 98.0 | 98.2 | 98.0 | 98.0 |
|
| ||||||
4.10.3.2 Stability of desorbed 3M 3520 OVM samples
The stability of desorbed samples was investigated by reanalyzing the target concentration samples 24 h after initial analysis. After the original analysis was performed three vials were recapped with new septa while the remaining three retained their punctured septa. The samples were reanalyzed with fresh standards. The average percent change was +0.7% for samples that were resealed with new septa and +0.3% for those that retained their punctured septa.
Stability of Desorbed 3M 3520 OVM Samples
|
| |||||
| punctured septa replaced | punctured septa retained | ||||
| initial DE (%) |
DE after one day (%) |
difference |
initial DE (%) |
DE after one day (%) |
difference |
|
| |||||
| 98.3 97.7 97.8 97.9 |
98.7 98.5 98.7 (averages) 98.6 |
+0.4 +0.8 +0.9 +0.7 |
97.8 98.2 98.5 98.2 |
98.4 98.5 98.6 (averages) 98.5 |
+0.6 +0.3 +0.1 +0.3 |
|
| |||||
4.10.4 SKC
- 4.10.4.1 The desorption efficiency (DE) of toluene was
determined by
Desorption Efficiency of Toluene from SKC
|
| ||||||
| × target concn mass spiked (µg) |
0.05× 129.8 |
0.1× 259.5 |
0.2× 519.0 |
0.5× 1297.5 |
1.0× 2595 |
2.0× 5190 |
|
| ||||||
| DE (%) |
97.6 97.8 98.0 96.6 99.8 98.2 |
97.4 98.2 99.8 98.4 97.3 97.6 |
97.2 97.0 96.8 98.9 98.1 97.9 |
96.0 97.3 97.2 97.1 96.8 96.6 |
97.4 98.6 97.9 97.7 97.0 97.3 |
97.0 97.1 97.3 96.7 94.7 96.6 |
|
98.0 | 98.1 | 97.6 | 96.8 | 97.6 | 96.6 |
|
| ||||||
4.10.4.2 Stability of desorbed SKC
The stability of desorbed samples was investigated by reanalyzing the target concentration samples 24 h after initial analysis. After the original analysis was performed three vials were recapped with new septa while the remaining three retained their punctured septa. The samples were reanalyzed with fresh standards. The average percent change was -0.2% for samples that were resealed with new septa and -0.6% for those that retained their punctured septa.
Stability of Desorbed SKC
|
| |||||
| punctured septa replaced | punctured septa retained | ||||
| initial DE (%) |
DE after one day (%) |
difference |
initial DE (%) |
DE after one day (%) |
difference |
|
| |||||
| 97.4 98.6 97.9 98.0 |
97.6 98.1 97.5 (averages) 97.7 |
+0.2 -0.5 -0.4 -0.2 |
97.7 97.0 97.3 97.3 |
97.4 96.1 96.7 (averages) 96.7 |
-0.3 -0.9 -0.6 -0.6 |
|
| |||||
4.11 Interferences (sampling)
- 4.11.1 Interference studies were performed by sampling for 240
minutes from a test atmosphere (10% RH, 26°C, 654.8 mmHg) containing
396 ppm of toluene with 50 ppm of 2-butanone (MEK), 20 ppm of
Recovery (%) from the Atmosphere Described in 4.11.1 for Each Sampler
|
| |||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers | |
|
| |||||
| 1 2 3 4 5 6 |
102.5 100.9 105.8 102.3 99.7 102.0 102.2 |
98.5 99.2 99.6 100.2 99.6 98.7 99.3 |
107.5 106.9 102.2 105.7 98.1 109.8 105.0 |
96.0 98.7 97.5 100.7 96.1 96.8 97.6 | |
|
| |||||
4.11.2 Short-term sampling interference studies were performed by
sampling for 1 minute from a test atmosphere (10% RH, 25°C, 654.3
mmHg) containing 495 ppm of toluene with 50 ppm of 2-butanone (MEK),
20 ppm of
Recovery (%) from the Atmosphere Described in 4.11.2 for Each Sampler
|
| |||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers | |
|
| |||||
| 1 2 3 4 5 6 |
96.5 98.1 97.8 100.7 94.8 96.4 97.4 |
95.4 96.6 97.7 99.3 98.8 95.0 97.1 |
113.0 113.0 105.7 111.6 105.7 111.8 110.1 |
103.0 106.3 106.7 102.4 102.8 112.4 105.6 | |
|
| |||||
4.11.3 A reverse diffusion study for the diffusive samplers and a stripping study for the adsorbent tubes was performed by sampling a 402 ppm atmosphere of toluene (78% RH, 23.5°C, 649.2 mmHg) for 120 minutes with six of each samplers. Three samplers from each set were additionally subjected to 120 minutes of the same atmosphere without the toluene present to determine if any of the collected toluene diffused off of the diffusive samplers and also whether it was stripped off of the adsorbent tubes. Upon analysis of the samples, the average recovery of the removed samplers versus the average recovery of the samplers that were additionally exposed to the atmosphere without toluene was within 90% for all samplers, indicating that reverse diffusion and stripping is not significant. The first three samples in Table 4.11.3 for each sampler were used to sample the toluene atmosphere for 120 minutes, while the last three were additionally exposed to a blank atmosphere for another 120 minutes.
Recovery (%) for the Circumstances Described in 4.11.3 for Each Sampler
(Samples 1-3 used to sample toluene atmosphere for 120 minutes,
samples 4-6 for an additional 120 minutes of blank atmosphere)
|
| ||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers |
|
| ||||
| 1 2 3 (1-3)4 5 6 (4-6)(4-6)/(1-3) |
99.6 98.2 100.0 99.3 100.4 100.1 100.1 100.2 1.01 |
97.9 98.3 98.2 98.1 97.6 97.1 98.2 97.6 1.00 |
99.7 101.9 94.0 98.5 99.9 99.4 99.5 99.6 1.01 |
108.6 101.0 99.3 103.0 105.0 100.4 98.4 101.3 0.98 |
|
| ||||
4.11.4 The effects from sampling from relatively dry atmospheres
was investigated by sampling from a 403.2-ppm toluene atmosphere (9%
RH, 25.3°C, 654.5 mmHg) for 240 minutes and from a 499-ppm
atmosphere (9% RH, 26.1°C, 653.9 mmHg) for 1 minute with all four
samplers. The average results for the adsorbent tubes did not
deviate from the theoretical concentration of toluene by more than
three standard deviations of the Day 0 storage samples in Section
4.7 (RSD = 1.07% and 1.94% for 240-min and 1-min charcoal tube
samples respectively, RSD= 1.93% and 1.38% for 240-min and 1-min
Anasorb® 747 tube samples respectively).
The average results for the diffusive samplers did not deviate from
the theoretical concentration of toluene by more than three standard
deviations based on the sampling rates determined in Section 4.9.3
for 3M OVMs (RSD = 3.49%) and in Section 4.9.4 for SKC
Recovery (%) for 240-minute Samples from a
Dry 403.2-ppm Toluene Atmosphere for Each Sampler
|
| ||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers |
|
| ||||
| 1 2 3 4 5 6 |
99.2 98.0 99.3 99.8 99.9 98.8 99.2 |
99.0 98.6 98.5 96.9 98.8 97.1 98.2 |
110.5 101.4 104.0 103.2 98.6 101.7 103.2 |
96.4 99.1 100.1 97.4 102.1 98.0 98.8 |
|
| ||||
Recovery (%) for 1-minute Samples from a
Dry 499-ppm Toluene Atmosphere for Each Sampler
|
| ||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers |
|
| ||||
| 1 2 3 4 5 6 |
98.6 98.0 97.7 100.3 97.5 96.9 98.2 |
98.0 99.3 99.0 100.8 100.2 98.1 99.2 |
112.6 113.9 106.7 103.2 109.9 107.6 109.0 |
104.8 106.0 105.7 103.2 105.0 109.4 105.7 |
|
| ||||
4.11.5 The effects from sampling from atmospheres containing low
concentrations of toluene was investigated by sampling from a
19.8-ppm toluene atmosphere (74% RH, 26.0°C, 651.4 mmHg) for 240
minutes and from a 49.3-ppm atmosphere (73% RH,
Recovery (%) for 240-minute Samples from a
19.8-ppm Toluene Atmosphere for Each Sampler
|
| ||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers |
|
| ||||
| 1 2 3 4 5 6 |
97.8 98.7 98.1 99.2 98.4 98.1 98.4 |
100.2 98.5 97.2 98.8 101.4 100.0 99.4 |
104.4 108.1 101.5 94.8 100.3 97.2 101.0 |
97.6 99.2 97.9 99.5 100.3 101.6 99.4 |
|
| ||||
Recovery (%) for 1-minute Samples from a
49.3-ppm Toluene Atmosphere for Each Sampler
|
| ||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers |
|
| ||||
| 1 2 3 4 5 6 |
97.3 97.7 100.7 90.3 94.4 92.4 95.5 |
107.1 99.6 105.8 103.0 101.2 99.3 102.7 |
112.0 107.2 108.5 110.6 106.8 104.6 108.3 |
111.9 96.2 103.9 104.1 114.0 96.0 104.4 |
|
| ||||
4.12 Desorption efficiency from wet samplers
The desorption efficiency from wet samplers was investigated by
spiking samplers with amounts of toluene (9039 µg for the
adsorbent tubes, 5190 µg for the 3M OVMs and 2595 µg for
the SKC
Desorption Efficiency (%) from Wet Samplers
|
| ||||
| sample no. |
Charcoal Tubes |
Anasorb®
747 Tubes |
3M OVMs |
SKC
Samplers |
|
| ||||
| 1 2 3 4 5 6 |
97.8 97.7 97.5 98.5 98.3 98.5 98.0 |
97.3 98.5 97.8 98.1 98.5 98.3 98.1 |
97.4 97.5 97.6 98.8 100.7 97.5 98.2 |
98.4 97.1 100.1 97.3 97.4 96.2 97.8 |
|
| ||||
4.13 Qualitative analysis
Toluene can easily be identified by GC/mass spectrometry. A typical mass spectrum of toluene is shown in Figure 4.13.
Figure 4.13. Representative mass spectrum of toluene.
5. References
- 5.1 Otterson, E. J.; Guy, C. U. Transactions of the
Twenty-Sixth Annual Meeting of the American Conference of Governmental
Industrial Hygienists, Philadelphia, PA, 1964; pp 37-46.
5.2 White, L. D.; Taylor, D. G.; Mauer, P. A.; Kupel, R. E. Am. Ind. Hyg. Assoc. J., 1970, 31, 225-232.
5.3 NIOSH Manual of Analytical Methods, 2nd ed. Vol. 1; U.S. Department of Health, Education and Welfare, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health; Cincinnati, OH, 1977, Method P&CAM 127, DHEW (NIOSH) Publication No. 77-157-A.
5.4 NIOSH Manual of Analytical Methods, 2nd ed. Vol. 3; U.S. Department of Health, Education and Welfare, Public Health Service, Centers for Disease Control, National Institute for Occupational Safety and Health; Cincinnati, OH, 1977, Method S343, DHEW (NIOSH) Publication No. 77-157-C.
5.5 OSHA Analytical Methods Manual; Vol. 1; U.S. Department of Labor, Occupational Safety and Health Administration; Directorate for Technical Support, OSHA Salt Lake Technical Center: Salt Lake City, UT, 1990; Method 7: Organic Vapors; American Conference of Governmental Industrial Hygienists (ACGIH): Cincinnati, OH, Publication No. 4542.
5.6 Elskamp, C. J., A Study to Determine (1) How Much Water is Collected by SKC Lot 120 Activated Charcoal at Various Relative Humidities, (2) How the Presence of Water Effects the Apparent Desorption Efficiency of 2-Methoxyethanol from Lot 120 Charcoal, and (3) How Effective Anhydrous Magnesium Sulfate is in Removing Water During the Desorption Process, OSHA Salt Lake Technical Center, unpublished, Salt Lake City, UT 84115-1802, January 1994.
5.7 OSHA Analytical Methods Manual; Vol. 4; U.S. Department of Labor, Occupational Safety and Health Administration; Directorate for Technical Support, OSHA Salt Lake Technical Center: Salt Lake City, UT, 1993; Method 91: Methyl Alcohol; American Conference of Governmental Industrial Hygienists (ACGIH): Cincinnati, OH, Publication No. 4542.
5.8 OSHA Analytical Methods Manual; Vol. 4; U.S. Department of Labor, Occupational Safety and Health Administration; Directorate for Technical Support, OSHA Salt Lake Technical Center: Salt Lake City, UT, 1993; Method 100: Ethyl Alcohol; American Conference of Governmental Industrial Hygienists (ACGIH): Cincinnati, OH, Publication No. 4542.
5.9 Eide, M. "OSHA Method No. 109, Isopropyl Alcohol"; OSHA Salt Lake Technical Center, unpublished, Salt Lake City, UT 84115-1802, June 1997.
5.10 Hendricks, W. Development of a Protocol for Laboratory Testing of Diffusive Samplers, OSHA Salt Lake Technical Center, unpublished, Salt Lake City, UT 84115-1802, December 1996.
5.11 Elskamp, C. J., The Collection of Water by 3M and SKC Diffusive Samplers from Humid Air, OSHA Salt Lake Technical Center, unpublished, Salt Lake City, UT 84115-1802, January 1997.
5.12 Proctor and Hughes' Chemical Hazards of the Workplace, 3rd ed.; Hathaway, G. J.; Proctor, N. H.; Hughes, J. P.; Fischman, M. L., Eds.; Van Nostrand Reinhold: New York, 1991, pp 546-547.
5.13 The Merck Index, 12th ed.; Budavari, S., Ed.; Merck & Co., Whitehouse Station, NJ, 1996, p 9666.
5.14 Kirk-Othmer Encyclopedia of Chemical Technology, 3rd ed.; Grayson, M., Ed.; John Wiley & Sons: New York, 1983, Vol. 23; pp 246-273.
5.15 Hawley's Condensed Chemical Dictionary, 12th ed.; Revised by Lewis, R. J.; Van Nostrand Reinhold: New York, 1993; p 1157.
5.16 Nelson, G. O. Gas Mixtures: Preparation and Control; Lewis: Boca Raton, 1992; Appendix M.
5.17 Hendricks, W., Determination of the Sampling Rate Variation for SKC 575 Series Passive Samplers, OSHA Salt Lake Technical Center, unpublished, Salt Lake City, UT 84115-1802, April 1998.