METHYL FORMATE
Method number: |
PV2041 |
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Matrix: |
Air |
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Target Concentration: |
100 ppm (246 mg/m3) OSHA permissible exposure limit (PEL). |
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Procedure: |
Samples are collected by drawing known volumes of air through Anasorb 747 sampling tube (6-mm i.d. glass tube, the front section contains 400 mg and the back 200 mg of sorbent). Samples are desorbed with a 90:10 (v/v) methyl alcohol/dimethylformamide solution and analyzed by gas chromatography (GC) using a flame ionization detector (FID). |
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Recommended air volume and sampling rate: |
3 L at 0.05 L/min |
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Detection limit of the overall procedure (based on the recommended air volume and the analytical detection limit): |
1.16 ppm (2.84 mg/m3) |
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Special requirements: |
Ship the samples cold after sampling to the laboratory and analyzed immediately. |
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Status of method: |
Partially evaluated method. This method has been partially evaluated and is presented for information and trial use only. |
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April 1992 (final) |
Chemist: Ing-Fong Chan |
Organic Service Branch II
OSHA Technical Center
Salt Lake City, Utah
1. General Discussion
1.1. Background
1.1.1. History of procedure
This evaluation was undertaken to develop a sampling and
analytical procedure for methyl formate at the OSHA PEL
100 ppm (Ref. 5.1.).
1.1.2. Toxic effects (This section is for information only and
should not be taken as the basis of OSHA policy.)
Inhalation of vapor produces nasal and conjunctival
irritation, retching, narcosis, and death from pulmonary
effects (Ref. 5.2., 5.3. and 5.4.).
1.1.3. Potential workplace exposure
Methyl formate has been employed as a fumigant and
larvicide, as well as a solvent for cellulose acetate and in
organic synthesis. (Ref. 5.2., 5.3. and 5.4.). No data is
available on the extent of work place exposure.
1.1.4. Physical properties (Ref. 5.2., 5.3. and 5.4.)
CAS number: |
107-31-3 |
IMIS number: |
1770 |
Molecular weight: |
60.05 |
Molecular formula: |
C2H4O2 |
Density: |
0.987 at 20°C |
Boiling point: |
31.5°C at 101.3 kPa (760 mmHg) |
Solubility: |
soluble in about 3.3 parts water miscible with alcohol and ether |
Chemical name: |
methyl formate |
Synonyms: |
methyl methanoate formic acid methyl ester |
Appearance: |
colorless liquid with an agreeable odor |
Structure: |
HCOOCH3 |
1.2. Limit defining parameters
The detection limit of the analytical procedure, including a 2.7:1
split ratio, is 3.16 ng per injection. This is the amount of analyte
which will give a peak whose height is approximately five times the
baseline noise.
2. Sampling Procedure
2.1. Apparatus
2.1.1. A sample is collected by using a personal sampling pump that can be calibrated to within
± 5% of the recommended flow rate with the sampling device in line.
2.1.2. A sample is collected with 6-mm i.d. × 8-mm o.d. glass sampling
tube packed with two sections of Anasorb 747 separated by a 2-mm portion of urethane
foam. The sampling section contains 400 mg and the back section contains 200 mg of Anasorb 747.
The sorbent is held in place with a glass wool plug at the front and a foam plug at the end of
the sorbent bed. The sampling tubes are commercially available from SKC.
2.2. Reagents
No sampling reagents are required.
2.3. Sampling technique
2.3.1. Immediately before sampling, break off the ends of the sampling tube. All tubes should be from the same lot.
2.3.2. Attach the sampling tube to the sampling pump with flexible tubing. Position the tube so that sampled air first
passes through the 400-mg section.
2.3.3. Attach the tube vertically in the employee's breathing zone in such a manner that it does not impede work performance.
2.3.4. After sampling for the appropriate time, remove the sample tube and seal it with plastic caps.
2.3.5. Wrap each sample end-to-end with an OSHA seal (Form 21).
2.3.6. Record the air volume for each sample and list any possible interferences.
2.3.7. Submit at least one blank for each set of samples. Handle the blank in the same manner as the samples, except
no air is drawn through it.
2.3.8. Ship the samples cold after sampling to the laboratory and analyzed immediately.
2.3.9. Submit bulk samples for analysis in a separate container. Do not ship bulk samples with air samples.
2.4. Desorption efficiency
Twelve vials, each containing 400-mg portion of Anasorb 747, were
divided into four groups of three vials each. Vials of the first
and the second groups were liquid spiked with 1.2 and 3.8 µL of
10% methyl formate in methyl alcohol, respectively. Vials of the
other two groups, were liquid spiked with 1.6 and 3.2 µL of 50%
methyl formate in methyl alcohol, respectively. These amount
represent 0.15×, 0.5×, 1.0×, and 2.0× the target concentration.
The vials were stored overnight in a refrigerator (0°C), desorbed
with 3.0 mL of the desorbing solution, and analyzed as in Section
3. The average desorption efficiency was 95.7%. The results are
listed in Table 2.4.
Table 2.4. Desorption Efficiency
|
Sample # |
Amount Spiked, µg |
Amount Found, µg |
% Recovered |
|
D1 D2 D3 |
115 115 115 |
115 112 115 |
100.0 97.4 100.0 |
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Average of 0.15× PEL = 99.1% |
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D4 D5 D6 |
366 366 366 |
343 343 347 |
93.7 93.7 94.8 |
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Average of 0.5× PEL = 94.0% |
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D7 D8 D9 |
770 770 770 |
717 729 742 |
93.1 94.7 96.4 |
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Average of 1× PEL = 94.7% |
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D10 D11 D12 D13 |
1540 1540 1540 Blank |
1427 1474 1494 0 |
92.7 95.7 97.0 0.0 |
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Average of 2× PEL = 95.1% |
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2.5. Retention efficiency
Four Anasorb 747 tubes were each liquid spiked with 1.6 µL (1×
PEL) of 50% methyl formate in methyl alcohol. These were allowed
to equilibrate for 2 hours and then 3 L of humid air (~80% relative
humidity) were drawn through each tube at 0.05 L/min. Then
the tubes were desorbed with 3.0 mL of desorbing solution, and
then analyzed as in Section 3. The results are listed in Table
2.5.
Table 2.5. Retention Efficiency
|
Sample # |
Amount Spiked, µg |
Amount Found, µg |
% Recovered |
|
R1 R2 R3 R4 |
770 770 770 770 |
711 724 770 748 |
92.3 94.0 100.0 97.1 |
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Average = 95.9% |
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2.6. Sample storage
Nine Anasorb 747 tubes were each liquid spiked with 1.6 µL (1×
PEL) of 50% methyl formate in methyl alcohol. These were allowed
to equilibrate for 2 hours and then 3 L of humid air (~80%
relative humidity) were drawn through each tube at 0.05 L/min. The
nine tubes were divided into three groups of three tubes each.
The first group was stored in a drawer at ambient temperature,
the second group was stored in a refrigerator (0°C) and the third
group was stored in a freezer (-5°C). After seven days they were
extracted and analyzed as in Section 3. No analytes were observed
in backup section. The results are given in Tables 2.6.1., 2.6.2. and 2.6.3..
Table 2.6.1. Ambient Storage
|
Days Stored |
Amount Spiked, µg |
Amount Found, µg |
% Recovered |
|
7 7 7 |
770 770 770 |
95 143 91 |
12.3 18.6 11.8 |
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Average = 14.2% |
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Table 2.6.2. Refrigerator Storage
|
Days Stored |
Amount Spiked, µg |
Amount Found, µg |
% Recovered |
|
7 7 7 |
770 770 770 |
615 640 633 |
79.9 83.1 82.2 |
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Average = 81.7% |
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Table 2.6.3. Freezer Storage
|
Days Stored |
Amount Spiked, µg |
Amount Found, µg |
% Recovered |
|
7 7 7 |
770 770 770 |
623 642 649 |
80.9 83.4 84.3 |
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Average = 82.9% |
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2.7. Recommended air volume and sampling rate
2.7.1. The recommended air volume is 3 L.
2.7.2. The recommended flow rate is 0.05 L/min.
2.8. Interferences (sampling)
It is not known if any compounds will interfere with the
collection of methyl formate. Any suspected interferences should be
reported to the laboratory with submitted samples.
2.9. Safety precautions (sampling)
2.9.1. Attach the sampling equipment in such a manner that it
will not interfere with work performance or employee
safety.
2.9.2. Follow all safety practices that apply to the work area
being sampled.
3. Analytical Procedure
3.1. Apparatus
3.1.1. A GC equipped with an FID. A Hewlett-Packard 5890 Gas
Chromatograph equipped with a 7673A Autosampler and an
FID was used in this evaluation.
3.1.2. A GC column capable of separating methyl formate from any
interferences. A 60 m × 0.32 mm i.d. (1.0 µm film)
STABILWAX capillary column was used in this evaluation.
3.1.3. An electronic integrator or some other suitable means to
measure detector response. A Waters 860 Networking
Computer System was used in this evaluation.
3.1.4. Volumetric flasks, pipets, and syringes for preparing
standards, making dilutions and performing injections.
3.1.5. Vials, 2-mL, and 4-mL, with PTFE-lined caps.
3.1.6. Mechanical shaker.
3.2. Reagents
3.2.1. Methyl formate. Methyl formate, 97.5+% purity, was
obtained from Eastman Chemical Company.
3.2.2. Methyl alcohol. The methyl alcohol used in this
evaluation was purchased from Fisher Scientific.
3.2.3. Dimethylformamide (DMF). The DMF was purchased from
Burdick and Jackson.
3.2.4. Desorbing solution, 90/10 (v/v) methyl alcohol and DMF.
3.3. Standard preparation
Prepare standards at concentrations of 1 µL, 2 µL and 4 µL of
methyl formate per milliliter of desorbing solution. Standards
must be used the day they are prepared.
3.4. Sample preparation
3.4.1. Transfer the 400-mg section of the sampling tube to a
4-mL vial. Place the 200-mg backup section in a separate
4-mL vial.
3.4.2. Add 3.0 mL of desorbing solultion to each vial and seal
with a Teflon-lined cap.
3.4.3. Shake the vials on a mechanical shaker for an hour.
3.5. Analysis
3.5.1. Instrument conditions
Column: |
STABILWAX, 60 m × 0.32 mm i.d., 1.0 µm film |
Injector temperature: |
150°C |
Detector temperature: |
200°C |
Column temperature: |
50°C (initial temp) |
Temperature program: |
hold initial temp. 5 min, increase temp. at 10°C/min to 190°C, hold final temp. 2 min |
Gas flow rates: |
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column: septum purge: FID: FID: FID: |
2.0 mL/min (hydrogen) 7.5 mL/min (hydrogen) 32 mL/min (hydrogen) 34 mL/min (nitrogen) 400 mL/min (air) |
Injection volume: |
1 µL |
Split ratio: |
2.7:1 |
Retention time: |
5.4 min (methyl formate) 8.7 min (methyl alcohol) 18.9 min (DMF) |
3.5.2. Chromatogram (Figure 1.)
3.5.3. Measure detector response using a suitable method such as
electronic integration.
3.6. Interferences (analytical)
3.6.1. Any collected compound which produces an FID response and
has a similar retention time as methyl formate is a
potential interference.
3.6.2. GC conditions may generally be varied to circumvent
interferences.
3.6.3. Retention time on a single column is not proof of
chemical identity. Analysis by an alternate GC column, high
performance liquid chromatography (HPLC) and confirmation
by mass spectrometry are additional means of identification.
3.7. Calculations
3.7.1. An external standard (ESTD) calibration method is used.
A calibration curve may be constructed by plotting
concentration of analyte per sample versus response of
standard concentration (µg/mL) of methyl formate. Bracket
the samples with freshly prepared analytical standards
over a range of concentrations.
3.7.2. Determine the µg/mL of methyl formate in both sections of each
sample and blank from the calibration curve. If methyl
formate is found on the backup section, it is added to
the amount found on the front section. Blank corrections
should be performed before adding the results together.
3.7.3. Determine the air concentration by using the following formula.
mg/m3 = |
(µg/mL, blank corrected) × (desorption volume, mL) (air volume, L) × (desorption efficiency, decimal) |
ppm = |
(mg/m)(24.46) (60.05) |
where |
24.46 60.05 |
= = |
molar volume (liters) at 101.3 kPa (760 mmHg) and 25°C molecular weight of methyl formate |
3.8. Safety precautions (analytical)
3.8.1. Avoid skin contact and air exposure to methyl formate.
3.8.2. Avoid skin contact with all solvents.
3.8.3. Wear safety glasses in laboratory.
4. Recommendation for Further Study
This method should be fully validated.
Figure 1. Chromatogram of methyl formate at 1.0× target level.
5. References
5.1. "Code of Federal Regulations", 29 CFR 1910.1000, Table Z-1-A.
Limits for Air Contaminants, U.S. Government Printing Office,
Washington, D.C., 1990.
5.2. Documentation of the Threshold Limit Values and Biological
Exposure Indices, American Conference of Governmental Industrial
Hygienist INC., 5th ed., 1986; p 397.
5.3. Sitting, M., Handbook of Toxic and Hazardous Chemicals, Noyes Publications, Park Ridge, N.J., 1981; p 453.
5.4. Windholz, M., Budavari, S., Blumetti, RF., and Otterbein, E., The Merck Index, 10th ed., Merck & CO., Inc., Rahway, N.J., 1983; p 870.
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