Page:NIOSH Manual of Analytical Methods - 2538.pdf/2

 ACETALDEHYDE: METHOD 2538, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1.

2. 3.

4. 5. 6. 7.

EQUIPMENT:

Toluene, chromatographic quality, containing 0.02% (v/v) dimethylformamide or other suitable internal standard. Acetaldehyde*, high-purity. Store in freezer at ca. -20 °C. 2-(Hydroxymethyl)piperidine (2-HMP). Recrystallize several times from isooctane until there is one major peak (>95% of area) by GC analysis. Store in desiccator. Calibration stock solution, 31.2 mg/mL. (APPENDIX A) Helium, purified. Hydrogen, prepurified. Air, filtered, compressed.



See Special Precautions

SPECIAL PRECAUTIONS: Acetaldehyde is toxic if inhaled or if it comes in contact with the eyes or skin [3], and is an animal carcinogen [4]. Exercise appropriate precautions in handling this chemical.

3. 4.

1. Sampler: glass tube, 11 cm long, 8-mm OD, 6-mm ID, flame sealed ends with plastic caps, containing two sections of 40/60 mesh 2(hydroxymethyl) piperidine coated on XAD-2 and separated by 2-mm glass-wool plug (front = 450 mg; back = 225 mg). Tubes are commercially available (Supelco, Inc. ORBO-25 or equivalent), or may be prepared (see APPENDIX B). 2. Personal sampling pump, 0.01 to 0.05 L/min. with flexible connecting tubing. 3. Gas chromatograph, capillary column, FID, integrator (page 2538-1). 4. Vials, 7-mL, glass, with PTFE-lined screw caps. 5. Ultrasonic bath or mechanical shaker. 6. Pipets, volumetric, 1- and 5-mL with pipet bulb. 7. Flasks, volumetric, 10- and 25-mL. 8. Syringe, 10 µL, readable to 0.1 µL. SAMPLING: 1.

Calibrate each personal sampling pump with a representative sampler in line. 2. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. Sample at an accurately known flow rate between 0.01 and 0.05 L/min for a total sample size of 1 to 12 L. Cap the samplers. Pack securely for shipment.

SAMPLE PREPARATION: 5. 6. 7.

Place front section and front glass-wool plug of the sampler in a vial. Place back section and center glass-wool plug in a separate vial. Discard rear glass-wool plug. Add 5.0 mL to toluene to each vial. Cap each vial tightly. Agitate in an ultrasonic batch for 60 min.

CALIBRATION AND QUALITY CONTROL: 8.

Calibrate daily with at least six working standards covering the range of the samples. a. Place 450-mg portions of coated XAD-2 sorbent, from the same lot as used to collect the air samples, into vials. b. Inject known volumes of calibration stock solution or a serial dilution thereof onto the sorbent to obtain acetaldehyde working standards in the range 2 to 2200 µg. Cap vials. NOTE: Prepare working standards ca. 16 h before air samples are to be analyzed to ensure that the reaction between acetaldehyde and 2-HMP is complete. c. Prepare three media blanks. d. Desorb (steps 5 through 7) and analyze (steps 10 and 11) the working standards and media blanks along with the samples and field blanks. e. Prepare calibration graph, ratio of peak area of analyte/peak area of internal Standard vs. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94