Page:NIOSH Manual of Analytical Methods - 1005.pdf/2

 METHYLENE CHLORIDE: METHOD 1005, Issue 3, dated 15 January 1998 - Page 2 of 4 REAGENTS:

EQUIPMENT:

1. 2. 3. 4. 5.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4-mm ID, flame-sealed ends with plastic caps, containing two sections of activated (600 C coconut shell charcoal (front = 100 mg, back = 50 mg) separated by a 2-mm urethane foam plug. A silylated glass wool plug precedes the front section and a 3-mm urethane plug follows the back section. Tubes are commercially available (SKC #226-01, Supelco ORBO-32s, or equivalent). 2. Personal sampling pump, 0.01 to 0.2 L/min, with flexible connecting tubing. 3. Gas chromatograph, flame ionization detector, integrator, and column (page 1005-1). 4. Vials, autosampler, with PTFE-lined caps. 5. Microliter syringes, 10-µL and other sizes as needed, readable to 0.1 µL. 6. Flasks, volumetric, various sizes. 7. Pipets, various sizes.

Methylene chloride, chromatographic grade.* Carbon disulfide, chromatographic grade. * Helium, purified. Hydrogen, prepurified. Air, filtered.


 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and a serious fire and explosion hazard (flash point = -30 C). Methylene chloride is a suspected carcinogen. Wear appropriate protective clothing and work with these compounds in a well ventilated hood.

SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break ends of sampling tubes immediately before sampling. Attach sampler train to personal sampling pump with flexible tubing. 3. Sample at an accurately known flow rate between 0.01 and 0.2 L/min for total a sample size of 0.5 to 2.5 L. 4. Separate the front and backup tubes to prevent migration of methylene chloride between tubes. Cap the samplers and pack securely for shipment.

SAMPLE PREPARATION: 5. Place front (along with first glass wool plug) and back sorbent sections of each tube in separate vials. Discard the foam plugs. 6. Add 1 mL of desorption solvent, CS2, to each vial and attach crimp caps. NOTE: Significant heat is generated when the desorbing solution is added to the charcoal. To minimize sample loss, chill the desorbing solution before adding to the charcoal [4]. 7. Allow to stand 30 min with occasional agitation to aid desorption.

CALIBRATION AND QUALITY CONTROL: 8. Calibrate daily with at least six working standards over the range of interest. Three standards (in duplicate) should cover the range from the LOD to LOQ. a. Add known amounts of methylene chloride to CS 2 in 10-mL volumetric flasks and dilute to the mark. NOTE: An internal standard such as 2-butanol or hexane can be added to the CS 2. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition