Page:NIOSH Manual of Analytical Methods - 2515.pdf/2

 DIAZOMETHANE: METHOD 2515, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS: 1.

2. 3.

4. 5. 6.

EQUIPMENT:

Eluent: Carbon disulfide,* chromatographic quality, with internal standard, tridecane (ca. 20 µg/mL). Methyl octanoate, reagent grade. Octanoic acid-coated resin. Pack 20/50 mesh XAD-2 resin (Rohm & Haas Co.) into a column (length to diameter ratio ca. 10:1). Wash with three bed volumes of methanol and two bed volumes of pentane. Check the washings by GC for interfering peaks. Dry at room temperature. Weigh out ca. 10 g washed and dried XAD-2 into a round-bottomed flask. Add 25 mL acetone to form a slurry. Add octanoic acid equivalent to 1% of the sorbent weight. Evaporate the solvent in a rotary evaporator. Dry the coated resin at room temperature. Hydrogen, prepurified. Nitrogen, purified. Air, filtered.

See SPECIAL PRECAUTIONS.

SAMPLING: 1. 2.

3.

4.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4mm ID,with plastic caps; two sections of 20/50 mesh 1% octanoic acid-coated XAD-2 resin preceded, separated and followed by silylated glass wool plugs (front = 100 mg; back = 50 mg). Tubes are commercially available (SKC, Inc. 226-23 or equivalent). 2. Personal sampling pump, 0.2 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 2515-1). 4. Vials, glass, 2-mL, PTFE-lined caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Pipet, 1.0-mL, with pipet bulb. 7. Volumetric flasks, 10-mL.

Calibrate each personal sampling pump with a representative sampler in line. 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 of 0.2 ±0.03 L/min for a total sample size of 6 to 30 L. Cap the samplers. Pack securely for shipment.

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and a serious fire and explosion hazard (flash point = -30 °C); all work with it must be done in a hood away from ignition sources. Diazomethane is an explosive, insidious poison and a strong irritant which may cause delayed hypersensitivity and cancer [3]. Concentrated solutions may explode violently, especially if impurities are present. Rough surfaces, such as ground glass, may also cause explosions [4].

SAMPLE PREPARATION: 5. 6. 7.

Place front and back sorbent sections of the sampler tube in separate vials. Discard the glass wool plugs. Add 1.0 mL eluent to each vial. Attach cap to each vial. Allow to stand 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 8.

Calibrate daily with at least six working standards over the range 1 to 32 µg methyl octanoate per sample. a. Add known amounts of methyl octanoate to eluent in 10-mL volumetric flasks and dilute to the mark. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94