1,1,1-TRICHLOROETHANE
Method no.: |
14 |
|
Matrix: |
Air |
|
Target Concentration: |
350 ppm (1900 mg/m3) OSHA PEL |
|
Procedure: |
Collection on charcoal adsorbent, desorption
with carbon disulfide, analysis by GC using a flame ionization detector. |
|
Recommended air volume
and sampling rate: |
3 L at 0.2 L/min |
|
Reliable quantitation limit: |
0.07 ppm (0.4 mg/m3) |
|
Standard error of estimate
at the PEL concentration:
(Section 4.4.) |
5.2% |
|
Status of method: |
Evaluated method, This method has been
subjected to the established evaluation procedures of the Organic Methods Evaluation
Branch. |
|
Date: January 1980 |
Chemist: Duane E. Lee |
Organic Methods Evaluation Branch
OSHA Analytical Laboratory
Salt Lake City, Utah
1. General Discussion
1.1. Background
1.1.1. History
Outdated methods for the sampling and analysis of 1,1,1-trichloroethane
called for collection of the sample in a gas sampling bag and analysis by infrared
spectroscopy or GC. (Ref. 5.1.) The use of gas sampling bags is awkward and impractical
when they must be transported to a central laboratory for the analysis. Infrared
absorption analysis is subject to serious interferences from other components collected in
the sample. GC offers an efficient and specific mode of analysis when air samples are
collected on charcoal, as in the NIOSH method. (Ref. 5.2.) This procedure was evaluated in
order to obtain additional data on storage stability of collected samples and collection
capacity in humid atmospheres.
1.1.2. Toxic effects (This section is for information only
and should not be taken as the basis of OSHA policy.)
The following information is taken directly from Reference
5.3.
1,1,1-Trichloroethane causes central nervous system
depression.
A number of human fatalities related to industrial exposure
in closed spaces have been reported, some of which may have been "sudden deaths"
due to sensitization of the myocardium to epinephrine.
Based on effects caused in monkeys and rats, the following
effects are expected in humans: 20,000 ppm for 60 min, coma and possibly death; 10,000 ppm
for 30 min, marked incoordination; 2000 ppm for 5 min, disturbance of equilibrium. Human
subjects exposed to 900 to 1000 ppm for 20 min experienced lightheadedness,
incoordination, and impaired equilibrium; transient eye irritation has also been reported
at similar concentrations.
A few scattered reports have indicated mild kidney and
liver injury in humans from severe exposure; animal experiments have confirmed the
potential for liver, but not for kidney, injury. Skin irritation has occurred from
experimental skin exposure to the liquid and from occupational use. The liquid can be
absorbed to a moderate degree through the skin.
In dogs, myocardial sensitization to epinephrine occurred
at concentrations of 5000 to 10,000 ppm. In a carcinogenicity study, rats and mice were
given the liquid orally at two different dose levels, five days a week for 78 weeks. Both
female and male test animals exhibited early mortality compared with untreated controls,
and a variety of neoplasms was found in both treated animals and controls. Although rats
of both sexes demonstrated a positive dose-related trend, no relationship was established
between the dosage groups, the species, sex, type of neoplasm, or the sites of occurrence.
The odor threshold has been described by various
investigators as ranging from 16 to 400 ppm.
The TLV was set at a level to prevent mild irritation.
1.1.3. Worker exposure
NIOSH estimates that there were 2.9 million workers exposed
to 1,1,1-trichloroethane. (Ref. 5.4.)
1.1.4. Use and operations where exposure occur
1,1,1-Trichloroethane is mainly used as a solvent for
cleaning and other solvent applications. There were 630 million pounds produced in 1976.
(Ref. 5.5.)
Industries where 1,1,1-trichloroethane is used
include: medical and other health services, automotive dealers and service stations,
wholesale trade, printing and publishing, eating and drinking places, communications,
chemicals and allied products, electrical equipment and supplies, fabricated metal
products, and others. (Ref. 5.4.)
1.1.5. Physical properties (Refs. 5.6. and 5.7.)
molecular weight: |
133.42 |
specific gravity: |
1.3249 (26°C/4°C) |
melting point: |
-32.62°C |
boiling point: |
74.1°C |
vapor density: |
4.6 (air = 1) |
vapor pressure: |
127 mm Hg (25°C) |
color: |
colorless liquid |
refractive index: |
1.43765 (21°C) |
saturated air: |
16.7% (25°C) |
saturated air density: |
1.6 (air = 1) |
solubility: |
insoluble in water; soluble in ethanol and
ethyl ether |
molecular formula: |
CCl3CH3 |
synonyms: (Ref. 5.4.) |
Aerothene TT; Chloroethene NU; Chlorothene;
Chlorothene NU; Chlorothene VG; Chlorten; Inhibisol; methyl chloroform;
methyltrichloromethane; NCI-C04626; Alpha-T; trichlorethane; a-trichloroethane. |
1.2. Limit defining parameters
1.2.1. Detection limit of the analytical procedure
The detection limit of the analytical procedure is 1.2 ng
per injection. This is the amount of analyte which will give a well defined peak on the
tail from the solvent peak. (Section 4.1.)
1.2.2. Detection limit of the overall procedure
The detection limit of the overall procedure is 1.2 µg per
sample (0.07 ppm or 0.4 mg/m3). This is the amount of analyte spiked on the
sampling device which allows recovery of an amount of analyte equivalent to the detection
limit of the analytical procedure. (Section 4.1.)
1.2.3. Reliable quantitation limit
The reliable quantitation limit is 1.2 µg per sample (0.07
ppm or 0.4 mg/m3). This is the smallest amount of analyte which can be
quantitated within the requirements of 75% recovery and 95% confidence limits of ±25%.
(Section 4.2.)
The reliable quantitation limit and detection limits
reported in the method are based upon optimization of the instrument for the smallest
possible amount of analyte. When the target concentration of an analyte is exceptionally
higher than these limits, they may not be attainable at the routine operating parameters.
1.2.4. Sensitivity
The sensitivity of the analytical procedure over a
concentration range representing 0.1 to 2.1 times the PEL concentration based on the
recommended air volume is 53430 area units per mg/mL. The sensitivity is determined by the
slope of the calibration curve. (Section 4.3.) The sensitivity will vary somewhat with the
particular instrument used in the analysis.
1.2.5. Recovery
The recovery of analyte from the collection medium must be
75% or greater. The average recovery over the range of 0.5 to 2 times the PEL is 99.6%.
(Section 4.1.)
1.2.6. Precision (analytical method only)
The pooled coefficient of variation obtained from replicate
determinations of analytical standards at 0.5, 1 and 2 times the PEL concentration is
0.0086. (Section 4.3.)
1.2.7. Precision (overall procedure)
The overall procedure must provide results at the PEL
concentration that are ±25% or better at the 95% confidence level. The precision at the
95% confidence level for the 15-day storage test is ±11.0% (Section 4.4.).
This includes an additional 5% for sampling error.
1.3. Advantages
1.3.1. The sampling procedure is convenient.
1.3.2. The analytical procedure is quick, sensitive, and
reproducible.
1.3.3. Reanalysis of the samples is possible.
1.4. Disadvantages
If other compounds are present, the GC run time must be
lengthened so the late eluting peaks will not interfere with the next sample.
2. Sampling Procedure
2.1. Apparatus
2.1.1. An approved and calibrated personal sampling pump
whose flow can be determined within ±5% at the recommended flow.
2.1.2. Charcoal tubes: Glass tube, with both ends heat
sealed, 7.0 cm × 6-mm i.d. × 4-mm i.d., containing 100-mg front and 50-mg
backup sections of 20/40 mesh charcoal SKC tubes or equivalent.
2.2. Reagents
None required.
2.3. Sampling technique
2.3.1. Immediately before sampling, break open the ends of
the charcoal tube. All tubes must be from the same lot.
2.3.2. Connect the charcoal tube to the sampling pump with
flexible tubing. The short section of the charcoal tube is used as a backup and should be
positioned nearer the sampling pump.
2.3.3. The tube should be placed in a vertical position
during sampling to minimize channeling.
2.3.4. Air being sampled should not pass through any hose
or tubing before entering the charcoal tube.
2.3.5. Seal the charcoal tube with plastic caps immediately
after sampling. Also, seal each sample with OSHA sealing tape lengthwise.
2.3.6. With each batch of samples, submit at least one
blank tube from the same lot used for samples. This tube should be subjected to exactly
the same handling as the samples (break, seal, transport) except that no air is drawn
through it.
2.3.7. Transport the samples (and corresponding paperwork)
to the lab for analysis.
2.3.8. If bulk samples are submitted for analysis, they
should be transported in glass containers with Teflon-lined caps. These samples must not
be put in the same container used for the charcoal tubes.
2.4. Breakthrough
Breakthrough tests were run on the primary portion of a
charcoal tube (SKC Lot 107) at a sampling rate of 0.2 L/min from a generated test
atmosphere. The test atmosphere was 708 ppm 1,1,1-trichloroethane with an
average relative humidity of 81.4% at 24.6°C. The 5% breakthrough volume was 3.7 L. This
was determined by monitoring the downstream effluent for 1,1,1-trichloroethane.
2.5. Desorption efficiency
The desorption efficiency from liquid injections on
charcoal tubes (SKC Lot 107), averaged 99.6% for 2.98 to 11.9 mg per tube, which is 182 to
728 ppm for a 3-L air volume (Section 4.1.).
2.6. Recommended air volume and sampling rate
2.6.1. The recommended air volume is 3 L.
2.6.2. The recommended sampling rate is 0.2 L/min.
2.6.3. If a longer sampling time is required, the sampling
rate should be lowered to 0.1 L/min or 0.05 L/min.
2.7. Interferences (sampling)
2.7.1. At the present time, it is unknown if any compound
would severely interfere with the collection of 1,1,1-trichloroethane on
charcoal. In general, the presence of other solvents will decrease the breakthrough volume
for a particular solvent.
2.7.2. Any compound which is suspected of interfering in
the collection or analysis should be listed on the sampling data sheet.
2.8. Safety precautions
2.8.1. Safety glasses should be worn when breaking the ends
of the tubes.
2.8.2. The broken ends of the tubes should be protected to
avoid injury to the person being sampled.
2.8.3. When working in environments containing flammable
vapors, do not provide any spark source from equipment used or pumps.
2.8.4. Observe all safety practices for working in
hazardous areas.
3. Analytical Procedure
3.1. Apparatus
3.1.1. A GC equipped with a flame ionization detector.
3.1.2. A number of GC columns are available and adequate.
The column used for this study was a 10-ft × 1/8-in. stainless steel 7% Penta 100/120
Chrom P AW.
3.1.3. An electronic integrator or other suitable method of
measuring peak area.
3.1.4. Two-milliliter vials with Teflon-lined caps.
3.1.5. Microliter syringes, 50-µL for preparing standards,
1-µL for sample injections.
3.1.6. Pipets for diluting standards. A 1-mL pipet for
dispensing solvent for desorption, or a 1-mL dispenser pipet.
3.1.7. Volumetric flasks, convenient sizes for preparing
standards.
3.2. Reagents
3.2.1. Carbon disulfide, chromatographic grade.
3.2.2. 1,1,1-trichloroethane, reagent grade.
3.2.3. Purified GC grade helium, hydrogen, and air.
3.3. Standard preparation
3.3.1. Standards are prepared by diluting pure 1,1,1-trichloroethane
with carbon disulfide.
3.3.2. Forty-five microliters of 1,1,1-trichloroethane
per 10 mL of carbon disulfide equals 364 ppm for a 3-L air sample desorbed with 1 mL of
carbon disulfide.
3.4. Sample preparation
3.4.1. The front and backup sections of each sample are
transferred to separate 2-mL vials.
3.4.2. Each section is desorbed with 1.0 mL of carbon
disulfide.
3.4.3. The vials are sealed immediately and allowed to
desorb for 30 min with intermittent shaking.
3.5. Analysis
3.5.1. GC conditions
helium (carrier gas) flow rate: |
25.1 mL/min |
injector temperature: |
150°C |
detector temperature: |
200°C |
column temperature: |
80°C |
detector: |
flame ionization |
hydrogen flow rate: |
43 mL/min |
air flow rate: |
248 mL/min |
injection size: |
1 µL |
3.5.2. Chromatogram (Section 3.5.2.)
3.5.3. Peak areas are measured by an electronic integrator
or other suitable means.
3.5.4. An external standard procedure is used. The
integrator is calibrated to report results in ppm for a 10-L air sample after correction
for desorption efficiency.
3.6. Interferences (analytical)
3.6.1. Any compound having the same general retention time
of 1,1,1-trichloroethane is an interference.
3.6.2. GC parameters may be changed to circumvent most
interferences.
3.6.3. Retention time on a single column is not considered
proof of chemical identity. Samples should be confirmed by GC/MS or other suitable means.
3.7. Calculations
Usually the integrator is programmed to report results in
ppm (corrected for desorption efficiency) for a 3-L air sample. The following calculation
is used:
ppm = (A)(3)/B |
where |
A = ppm on report
B = air volume, L |
3.8. Safety precautions
3.8.1. All work using solvents (preparation of standards,
desorption of samples, etc.) should be done in a hood.
3.8.2. Avoid any skin contact with all of the solvents.
3.8.3. Safety glasses should be worn throughout the
procedure.
4. Backup Data
4.1. Detection limit data
4.1.1. Analytical detection limit
A small amount of analyte (1.2 ng/injection) which still
produced a well defined peak on the tail of the solvent peak was designated as the
analytical detection limit. This was determined with an analytical standard which
contained 0.009 µL of 1,1,1-trichloroethane per milliliter of carbon
disulfide or 1.2 µg/mL. The chromatogram is shown in Figure 4.1.1.
Reproducibility of the peak, produced by replicate 1.2-ng
injections, was good. Twelve injections gave an average analyte peak height of 35 mm with
coefficient of variation of 2.4%.
A sample collected from 3 L of air which contained 1.2
ng/µL after desorption with 1 mL of carbon disulfide would represent an air concentration
of 0.07 ppm.
4.1.2. Desorption efficiencies for determining the overall
detection limit and the reliable quantitation limit
Liquid injections were made on the front portion of
charcoal tubes (SKC Lot 107) at 0.0012 to 11.92 mg. These charcoal tubes were refrigerated
overnight and desorbed and analyzed the following day. These results are presented in
Table 4.1.2. and in Figures 4.1.2.1. and 4.1.2.2. The overall detection limit was
determined to be 1.2 µg/sample in Figure 4.1.2.1.
Table 4.1.2.
Desorption Efficiencies for Various Sampler Loadings
|
µg/sample |
11920 |
5960 |
2980 |
1484 |
296.8 |
59.4 |
11.9 |
2.37 |
1.187 |
|
desorption |
98.2 |
99.6 |
101.7 |
99.8 |
100.4 |
97.2 |
101.1 |
99.7 |
100.7 |
efficiency, |
98.5 |
99.5 |
99.4 |
99.0 |
100.2 |
98.0 |
101.0 |
-- |
100.0 |
% |
96.4 |
94.7 |
100.1 |
99.1 |
100.2 |
101.0 |
100.4 |
99.0 |
102.0 |
|
97.3 |
98.6 |
99.2 |
|
|
98.2 |
99.5 |
100.3 |
The
average desorption efficiency over the
range of 2980 to 11920 µg (0.5 to 2 times
the target concentration) is 99.6%. |
|
98.5 |
98.3 |
100.1 |
|
102.2 |
102.2 |
104.5 |
|
101.3 |
102.1 |
102.4 |
|
![mean](https://webarchive.library.unt.edu/eot2008/20081106064103im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif) |
98.8 |
99.3 |
101.0 |
|
|
4.2. Reliable quantitation limit
The reliable quantitation limit was verified to be the same
as the overall detection limit by liquid spiking six samples with loadings equivalent to
the overall detection limit (1.187 µg/sample). These samples were analyzed to assure the
requirements of at least 75% recovery with a precision (1.96 SD) of at least ±25% were
met.
Table 4.2.
Reliable Quantitation Limit
|
sample no. |
% recovered |
sample no. |
% recovered |
|
1
2
3 |
98.6
94.3
99.3 |
4
5
6 |
100.0
100.0
98.6 |
|
= 98.5 |
SD = 2.135 |
1.96(SD) = 4.2 |
|
|
4.3. Precision data
Multiple injections were made of standards that were
prepared over a range of 0.1 to 2.1 times the OSHA standard. A standard deviation was
determined at each concentration. The pooled coefficient of variation was determined for
the range.
Table 4.3.
Analytical Precision
|
× target conc.
µg/sample |
0.1×
596 |
0.2×
1190 |
0.5×
2980 |
1.0×
5960 |
2.1×
11920 |
|
area counts
![mean](https://webarchive.library.unt.edu/eot2008/20081106064103im_/http://www.osha.gov/dts/sltc/methods/images/mean.gif)
SD
CV
= 0.0086 |
33828
33747
34117
33516
33586
33650
33742
216
0.0064 |
67545
66599
66413
68164
67086
67182
67165
638
0.0095 |
166773
165396
167897
164153
163485
163222
165150
1882
0.0114 |
327123
327763
328157
325401
322931
324246
323908
323029
325319
2117
0.0065 |
647551
643296
642360
635031
634452
633876
639427
5735
0.0090 |
|
4.4. Storage data
Samples were collected on charcoal tubes (SKC Lot 107) from
a generated atmosphere containing 354 ppm 1,1,1-trichloroethane with an
average relative humidity of 81% at 23.5°C. A storage study was then
conducted in which the collected samples were divided into two groups; one stored at
ambient temperature and the other under refrigeration. Every few days, three samples from
each group were analyzed. The results are shown in Table 4.4. and in Figures 4.4.1. and
4.4.2.
Table 4.4.
Storage Tests
|
storage time |
% recovery |
(days) |
(-4°C to 3°C) |
|
(18.2°C to 21°C) |
|
1
3
6
9
12
15 |
102.8
100.6
104.2
102.0
102.2
102.3 |
104.7
99.8
101.6
99.3
101.0
100.8 |
102.5
100.8
102.0
101.6
101.5
101.1 |
|
106.0
101.0
101.8
105.4
104.3
100.9 |
103.1
103.2
101.5
102.6
103.0
100.0 |
104.4
102.8
103.3
100.9
102.1
101.6 |
|
Figure 3.5.2. Chromatogram of a standard of 1,1,1-trichloroethane.
Figure 4.1.1. Chromatogram of the analytical
detection limit of 1,1,1-trichloroethane.
Figure 4.1.2.1. The detection limit of the
overall procedure of 1,1,1-trichloroethane.
nt face="Arial" size="2">Figure 4.1.2.2. Desorption efficiency data
for 1,1,1-trichloroethane.
Figure 4.3. Calibration curve of instrument
response to 1,1,1-trichloroethane.
Figure 4.4.1. Ambient storage test of 1,1,1-trichloroethane.
Figure 4.4.2. Refrigerated storage test of 1,1,1-trichloroethane.
5. References
5.1. American Industrial Hygiene Association: Analytical
Abstract "Halogenated Hydrocarbons" A.I.H.A., 1965.
5.2. National Institute for Occupational Safety and Health,
U.S. Department of Health, Education, and Welfare: NIOSH Manual of Analytical Methods,
Vol. 3, Washington, D.C.: U.S. Government Printing Office, (NIOSH) Pub. No. 77-157-C,
Method No. S328, 1977.
5.3. Proctor, N.H., and Hughes, J.P., Chemical Hazards of
the Workplace., Philadelphia: J.B. Lippincott Co., pp 488-489, 1978.
5.4. National Institute for Occupational Safety and Health,
U.S. Department of Health, Education and Welfare: NIOSH Current Intelligence Bulletin 17.
Washington, D.C.: U.S. Government Printing Office (NIOSH) Pub. No. 78-181, 1978.
5.5. A.C.G.I.H.: Methyl chloroform (1,1,1-trichloroethane).
Documentation of the TLVs for Substances in Workroom Air. ed. 3, Cincinnati, pp 161-162,
1976.
5.6. Standen, A. (editor), Kirk-Othmer Encyclopedia of
Chemical Technology. 2nd ed., New York: Interscience Publishers, Vol. 5, pp. 154-157,
1964.
5.7. Patty, F.A. (editor) Industrial Hygiene and
Toxicology, 2nd ed., New York: John Wiley and Sons, Inc., p. 1288, 1963.
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