National Institute for Occupational Safety and Health

“ APPENDIX: STANDARDIZATION OF CALIBRATION STOCK SOLUTION. Pipet 10-mL aliquots of the stock solution into two separate 250-mL Erlenmeyer flasks. Add 10 mL 2.5% hydrazine sulfate to one of the flasks and allow to stand 10 minutes with occasional swirling. The other flask serves as a blank and determines any free halide ion already present. Add 10 mL 0.100 N silver nitrate solution, 5 mL nitric acid solution, and 2 mL ferric ammonium sulfate solution to each flask. Swirl and add 2 mL nitrobenzene. ”

“ Attach sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.05 and 0.2 L/min for a total sample size of 3 to 16 L. Cap the samplers with plastic (not rubber) caps and pack securely for shipment.
SAMPLE PREPARATION: 5. 6. 7.
Transfer the glass wool plug and front section of silica gel to a 50-mL Erlenmeyer flask. Transfer the backup sorbent section to another flask. Pipet 25 mL 50% aqueous methanol into each flask. Shake each flask occasionally over a 30-min period. Analyze samples within 1 day.
CALIBRATION AND QUALITY CONTROL: 8. ”

“ Prepare calibration graph of μg chloroacetaldehyde/25 mL vs. peak area. Determine desorption efficiency (DE) at least once for each batch of silica gel used for sampling in the calibration range (step 8) . Prepare three tubes at each of five concentrations plus three media blanks. a. Remove and discard the back sorbent section of a media blank sampler. b. Inject a known amount of standard ( ≤ 100 μL) directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. ”