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Related Information: Chemical Sampling - Ethyl Methacrylate


Method no.: PV2100
 
Control no.: T-PV2100-01-8903-CH
 
Matrix: Air
 
Target concentration: 100 ppm (467mg/m3)
 
Procedure: Samples are collected by drawing a known volume of air through a charcoal tube (100/50 mg, 20/40 mesh) lot 120. Samples are desorbed with carbon disulfide and analyzed by gas chromatography with a flame ionization detector (GC-FID).
 
Air volume and sampling rate studied: 10 liters at 0.2 L/min
 
Status of method: Stopgap method. This method has been only partially evaluated and is presented for information and trial use.
 
Date: March 1989
Chemist: Mary E. Eide
   
Solvents Branch
OSHA Analytical Laboratory
Sandy, Utah 84070

1. General Discussion

1.1 Background
1.1.1 History of procedure

The OSHA Laboratory recently received samples collected on charcoal tubes requesting analysis for ethyl methacrylate. A desorption study using carbon disulfide as the desorbing solvent showed a 92.8% recovery. The other analytes requested on the samples could not be desorbed with carbon disulfide. Other desorbing solvents tried were 1:99 dimethyl formamide:carbon disulfide (97.4% desorption efficiency) and 5:95 methanol:methylene chloride (98.5% desorption efficiency). The retention studies gave 100% recovery. The storage study for 14 days averaged 98.3% recovery.

1.1.2 Toxic Effects (Ref. 5.1) (This section is for information purposes and should not be taken as the basis for OSHA policy.)

Ethyl methacrylate causes irritation to mucous membranes in high concentrations. Ethyl methacrylate in high concentrations is a teratogen.

1.1.3 Potential workplace exposure (Ref. 5.2)

Ethyl methacrylate is used in the manufacture of resins, polymers, fake nails, and contact lens.

1.1.4 Physical properties: (Ref. 5.3)
Synonyms:


Methacrylic acid, ethyl ester; ethyl 2-methylacrylate; ethyl 2-methyl-2-propenoate; Rhoplex AC-33; 2-propenoic acid, 2-methyl-ethyl ester.
Structure: structure
Molecular weight:
Density:
Freezing point:
Boiling point:
Odor:
Color:
Molecular formula:
Flash point:
CAS:
IMIS:
RTECS:
114.14
0.9135
-75°C
117°C
acrylate odor
clear or light yellow liquid
C6H10O2
21°C (70°F)
97-63-2
E115
47787 (OZ 4550000)
1.2 Limit defining parameters
1.2.1 The detection limit of the analytical procedure is 1 µg ethyl methacrylate. This is the smallest amount that could be detected under normal operating conditions. 1.2.2 The overall detection limit is 0.02 ppm based on a 10 liter air volume. All ppm amounts in this study will be based on a 10 liter air volume.
1.3 Advantages
1.3.1 The sampling procedure is convenient.

1.3.2 The analytical method is reproducible and sensitive.

1.3.3 Re-analysis of samples is possible.

1.3.4 It may be possible to analyze other compounds at the same time.

1.3.5 Interferences may be avoided by proper selection of column and GC parameters.
1.4 Disadvantages

None found.

2. Sampling procedure

2.1 Apparatus
2.1.1 A calibrated personal sampling pump, the flow of which
can be determined within ±5% at the recommended flow.

2.1.2 Coconut shell charcoal tubes, lot 120, containing a 100 mg adsorbing section with a 50 mg backup section separated by a 2 mm portion of urethane foam, with a silane-treated glass wool plug before the adsorbing section and a 3 mm plug of urethane foam at the back of the backup section. The ends are flame sealed and the glass tube containing the adsorbent is 7 cm long, with a 6 mm O.D. and 4 mm I.D., SKC tubes or equivalent.
2.2 Sampling technique
2.2.1 The ends of the charcoal tube are opened immediately before sampling.

2.2.2 Connect the charcoal tube to the sampling pump with flexible tubing.

2.2.3 Tubes should be placed in a vertical position to minimize channeling, with the smaller section towards the pump.

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

2.2.5 Seal the charcoal tube with plastic caps immediately after sampling. Seal each sample lengthwise with OSHA Form-21 sealing tape.

2.2.6 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 ends, seal, & transport) except that no air is drawn through it.

CV equation

2.2.7 Transport the samples (and corresponding paperwork) to the lab for analysis.

2.2.8 Bulks submitted for analysis must be shipped in a separate mailing container from the samples.
2.3 Desorption and/or Extraction efficiency
2.3.1 The desorption study of ethyl methacrylate with 1 mL carbon disulfide standard was performed by liquid spiking six charcoal tubes at each of the following levels; 0.4568 mg (9.79 ppm), 2.284 mg (48.9 ppm), and 4.568 mg (97.9 ppm). The tubes were allowed to equilibrate overnight at room temperature. They were opened, each section placed into separate 2 mL vials and desorbed with 1 mL carbon disulfide, for 30 minutes with occasional shaking. They were analyzed by GC-FID. The desorption efficiency was 92.8% (Table 2.3.1).
Table 2.3.1

Carbon Disulfide Desorption Study
% Desorption

Tube # 0.4568 mg 2.284 mg 4.568 mg

1 89.1 94.7 94.6
2 88.3 94.3 94.4
3 88.8 94.1 93.6
4 89.5 94.2 94.3
5 89.4 93.9 93.9
6 89.5 99.6 94.4
Average 89.1 95.1 94.1
Overall Average 92.8
Standard Deviation ±2.98


2.3.2 The desorption efficiency using 1:99 dimethyl formamide: carbon disulfide was performed by liquid spiking six tubes with ethyl methacrylate at the following levels (equivalent air concentrations) of 0.4568 mg (9.79 ppm), 2.284 mg (48.9 ppm), and 4.568 mg (97.9 ppm). The samples were stored overnight at room temperature. They were opened, each section placed into a separate 2 mL vial, desorbed with 1 mL desorbing solvent for 30 minutes with occasional shaking and analyzed by GC-FID. The desorption efficiency averaged 97.4% (Table 2.3.2).

Table 2.3.2

1:99 Dimethyl Formamide: Carbon Disulfide
Desorption Study
% Desorption

Tube # 0.14568 mg 2.284 mg 4.568 mg

1 97.9 96.0 97.1
2 98.2 96.0 97.3
3 97.3 96.4 97.3
4 99.3 97.4 97.7
5 96.9 96.8 97.8
6 98.4 96.6 98.2
Average 98.0 96.5 97.6
Overall Average 97.4
Standard Deviation ±0.855

2.3.3 The desorption study using 5:95 methanol: methylene chloride was performed by liquid spiking six charcoal tubes with ethyl methacrylate at the following levels (equivalent air concentration), 0.4568 mg (9.79 ppm), 2.284 mg (48.9 ppm), 4.568 mg (97.9 ppm), and 9.135 mg (196 ppm). The tubes were allowed to equilibrate at room temperature overnight. They were opened, each section placed into a separate 2 mL vial, and desorbed with 1 mL of the desorbing solution for 30 minutes with occasional shaking, and analyzed by GC-FID. The desorption efficiency averaged 98.5% (Table 2.3.3).

Table 2.3.3

5:95 Methanol: Methylene Chloride Desorption Study
% Desorption

Tube # 0.457 mg 2.28 mg 4.57 mg 9.14 mg

1 98.0 100 96.8 100
2 99.7 96.5 97.7 100
3 96.4 100 95.6 100
4 100 96.5 99.5 100
5 99.5 100 96.4 99.8
6 95.9 lost 95.3 100
Average 98.3 98.7 96.9 100
Overall Average 98.5
Standard Deviation ±1.79

2.4 Retention efficiency

The retention efficiency was performed by spiking six tubes with 4.568 mg (97.9 ppm) ethyl methacrylate, and drawing 10 liters of humid air (94% RH) through them. They were opened, desorbed with 1 mL desorbing solution, and analyzed by GC-FID. The amounts in Table 2.4 are desorption corrected and the average recovery was 102%.

Table 2.4

Retention Efficiency

1 104 ND 104
2 105 ND 105
3 101 ND 101
4 102 ND 102
5 101 ND 101
6 102 ND 102
Average 102


2.5 Storage

Six charcoal tubes were spiked with 4.568 mg (97.9 ppm) and stored at room temperature. Three of these tubes were analyzed at 6 and 14 days after spiking. The amounts reported are desorption corrected. The average recovery was 99.7% (Table 2.5).

Table 2.5

Storage Study

Days Stored % Recovered

6 100
6 100
6 101
14 99.1
14 98.6
14 99.6
Average 99.7


2.6 Precision

The precision was determined by six injections of standard at concentrations of 0.4568 mg/mL (9.79 ppm), 2.284 mg/mL (48.9 ppm), 4.568 mg/mL (97.9 ppm), and 9.135 mg/mL (196 ppm) (Table 2.6).

Table 2.6

Precision of the Analytical Procedure

Injection Number 0.4568 mg/mL 2.284 mg/mL 4.568 mg/mL 9.135 mg/mL
1 498338 2444481 4974609 9745276
2 493750 2448606 4968818 9755312
3 492081 2479016 4940095 9774749
4 497300 2480853 4925562 9732824
5 498060 2476000 4980306 9718711
6 497177 2483968 4942801 9719335
Average 496118 2468821 4955365 9741035
Standard Deviation ±2574 ±17497 ±22849 ±21887
CV 0.00519 0.00709 0.00461 0.00225
Pooled CV 0.00519         

A(1), A(2), A(3), A(4) = # of injections at each level
CV1, CV2, CV3, CV4 = Coefficients at each level

2.7 Air volume and sampling rate studied
2.7.1 The air volume studied was 10 liters.

2.7.2 The sampling rate studied was 0.2 liters per minute.
2.8 Interferences
Suspected interferences should be listed on sample data sheets.
2.9 Safety precautions
2.9.1 Sampling equipment should be placed on an employee in a manner that does not interfere with work performance or safety.

2.9.2 Safety glasses should be worn at all times.

2.9.3 Follow all safety practices that apply to the workplace being sampled.

3. Analytical method

3.1 Apparatus
3.1.1 Gas chromatograph equipped with a flame ionization-
detector.

3.1.2 GC column capable of separating the analyte and an
internal standard from any interferences. The column used in this study was a 12 ft stainless steel column packed with 10% FFAP on 80/100 mesh Chrom WAW.

3.1.3 An electronic integrator or some other suitable method of measuring peak areas.

3.1.4 Two milliliter vials with Teflon-lined caps.

3.1.5 A 10-µL syringe or other convenient size for sample injection.

3.1.6 Pipets for dispensing the desorbing solution. The Glenco 1 mL dispenser was used in this evaluation.

3.1.7 Volumetric flasks - 5 mL and other convenient sizes for preparing standards.
3.2 Reagents
3.2.1 Purified GC grade nitrogen, hydrogen, and air.

3.2.2 Ethyl Methacrylate, Reagent grade 3.2.3 Carbon Disulfide, Reagent grade

3.2.4 Internal Standard (p-Cymene) Reagent grade

3.2.5 Desorbing solution contains 1 µL/mL p-cymene in carbon
disulfide.
3.3 Sample preparation
3.3.1 Sample tubes are opened and the front and back section of each tube are placed in separate 2 mL vials.

3.3.2 Each section is desorbed with 1 mL of carbon disulfide with 1 µL/mL p-cymene internal standard.

3.3.3 The vials are sealed immediately and allowed to desorb for 30 minutes with occasional shaking.
3.4 Standard preparation
3.4.1 Standards are prepared by diluting a known quantity of ethyl methacrylate with carbon disulfide containing 1 µL/mL internal standard. A 1 µl/mL standard of ethyl methacrylate in the desorbing solution contains 984.4 µg/mL (21.09 ppm) corrected for the desorption efficiency of 92.8%.

3.4.2 At least two separate standards should be made.

3.4.3 A third standard at a higher concentration should be prepared to check the linearity of the analysis. This third standard is at 4 µL/mL.
3.5 Analysis
3.5.1 Gas chromatograph conditions.
Flow Rates (mL/min) Temperature (ºC)

Nitrogen (carrier): 29 Injector: 180
Hydrogen: 40 Detector: 220
Air: 240 Column: 80ºC, hold 4 min ramp at 10ºC/min to 140ºC
Injection Size: 1 µL
Elution time: 2.56 min
Chromatogram: chromatogram
3.5.2 Peak areas are measured by an integrator or other suitable means.
3.6 Interferences (analytical)
3.6.1 Any compound having the general retention time of the analyte or the internal standard used is an interference. Possible interferences should be listed on the sample data sheet. GC parameters should be adjusted if necessary so these interferences will pose no problems.

3.6.2 Retention time data on a single column is not considered proof of chemical identity. Samples over the target concentration should be confirmed by GC/Mass Spec or other suitable means.
3.7 Calculations
3.7.1 The integrator is calibrated with two standards at the same concentration, and the linearity of the analysis is checked with the third standard.

3.7.2 To calculate the air concentration of analyte in the sample, the following formulas are used:

equations for analyte

3.7.3 The above equations can be consolidated to form the following formula. To calculate the ppm of analyte in the sample based on a 5 liter air sample:

    (µg/mL)(DV)(24.46)(106)(g)(mg)
ppm =
    (5 L)(DE)(MW)(1000 mg)(1000 mg)

µg/mL = concentration of analyte in sample or standard
24.46 = Molar volume (liters/mole) at 25°C and 760 mmHg
MW = Molecular weight (g/mole)
DV = Desorption volume
5 L = 5 liter air sample
DE = Desorption efficiency

3.7.4 This calculation is done for each section of the sampling tube and the results added together.
3.8 Safety precautions
3.8.1 All handling of solvents should be done in a hood.

3.8.2 Avoid skin contact with all solvents.

3.8.3 Wear safety glasses at all times.

4. Recommendations for further study: Collection studies for ethyl methacrylate need to be performed.

5. References

5.1 Sweet, D., "Registry of Toxic Effects of Chemical Substances," 1985-86 edition, U.S. Department of Health and Human Services, Public Health Service, Center for Disease Control, NIOSH, 1987, Vol. 3A, p. 3060-101.

5.2 Hawley, G., "The Condensed Chemical Dictionary", Van Nostrand Reinhold Co. New York, N.Y. Tenth Edition, 1981, p. 440.

5.3 Weast, R.C., Grasselli, J.G., "Handbook of Data on Organic Compounds", CRC Press, Inc. Boca Raton, FL. 2nd Edition, 1985, page 3810.