National Institute for Occupational Safety and Health

“ Dilutions can be stored in the freezer until determined that they are needed. CALIBRATION AND QUALITY CONTROL: 8.
Calibrate daily with at least six working standards over the range 0.14 to 272 μg methyl bromide per sample from calibration stock solution. NOTE:
0.085 μmoles bromine per μL is equivalent to a methyl bromide concentration of 8.07 μg/μL. a. Add known aliquots (2.0-, 20-, 45-, and 120-μL) of calibration stock solution to methylene chloride in 10-mL vials with PTFE-lined caps. Take 1 mL of lowest standard and dilute to 10 mL with methylene chloride. ”

“ Limit sample volume to 1.0 L if RH ≥ 50% and no drying tube is used. 4.
Separate the front and back tubes immediately after sampling. Cap the tubes. Pack securely in dry ice for shipment. Store at −10 °C until analysis. SAMPLE PREPARATION: 5.
Place the sorbent sections from each sampling tube in separate vials. Discard the glass wool plugs. 6.
Add 3.0 mL chilled eluant (methylene chloride) to each 400-mg section, and 2.0 mL chilled eluant to each 200-mg section. Immediately cap each vial. 7.
Allow to stand at least 30 minutes at room temperature with occasional agitation. ”

“ If peak area is above the linear range of the working standards, dilute with eluant, reanalyze, and apply the appropriate dilution factor in calculations. 12.
Measure peak area. CALCULATIONS: 13.
Determine the mass, μg (corrected for DE) of methyl bromide found in the 400-mg sample tube ( ) and 200-mg sample tube ( ) , and in the average media blanks for the 400-mg ( ) and 200-mg ( ) sorbent tubes. 14.
Calculate concentration, , of methyl bromide in the air volume sampled, (L) : , mg/m3. ”