Page:NIOSH Manual of Analytical Methods - 4000.pdf/2

 TOLUENE: METHOD 4000, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS:

EQUIPMENT:

1. Eluent: carbon disulfide (CS2), chromatographic quality.* 2. Toluene, reagent grade. 3. Nitrogen or helium, purified. 4. Hydrogen, prepurified. 5. Air, filtered.

1. Sampler: diffusive monitor with activated charcoal collection element. Monitors must be of known sampling rate for toluene. 2. Gas chromatograph, FID, integrator and column (page 4000-1). 3. Vials, glass, 2-mL, with PTFE-lined septum caps. 4. Pipet, TD, 1.5-mL, and pipet bulb. 5. Syringes, 5-, 10-, 25- and 100-µL. 6. Volumetric flasks, 10-mL. 7. Tweezers.


 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and extremely flammable (flash point = 30 C); work with it only in a fume hood.

SAMPLING: 1.

Remove sampler from package and remove caps, if applicable. Attach sampler in worker's breathing zone. Make sure sampler inlets are unobstructed. Record start of sampling time. Follow manufacturer's recommendations to estimate appropriate sampling time based on relative humidity and suspected concentration of toluene. NOTE: The uptake constant is only valid for samplers in air with ambient velocity higher than ca. 10 cm/sec. For area samples, ensure adequate air movement. 2. Terminate sampling by sealing the sampler as recommended by the manufacturer or by transferring, in a toluene-free environment, the activated charcoal collection element to a vial and sealing the vial with a septum cap. Use tweezers for handling the collection element, taking care not to touch any activated charcoal. NOTE: Some sampler designs (e.g., 3M 3500 [3]) do not require transfer of the collection element; others (e.g., Gilian Trace Air OVM-1 and OVM-2) require transfer of sorbent pad to a sealed vial. Some sampler designs (e.g., Draeger ORSA-5) use granular sorbent.

SAMPLE PREPARATION: 3. Add 1.5 mL CS2 to each collection element. 4. Allow to stand at least 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTROL: 5. Calibrate daily with at least six working standards. a. Add known amounts of toluene to CS2 in 10-mL volumetric flasks and dilute to the mark to produce toluene concentrations in the range 0.01 to 10 mg/mL. b. Analyze with samples and blanks (steps 8 through 10). c. Prepare calibration graph (peak area vs. mg/mL toluene). 6. Determine desorption efficiency (DE) in the calibration range at least once for each lot of samplers used. Prepare three samplers at each of five concentrations plus three media blanks. a. Place the collection element of a media blank sampler into a vial and cap. b. Inject a known amount of toluene directly onto the collection element with a microliter syringe. c. Allow to stand overnight. d. Desorb (steps 3 and 4) and analyze with working standards. e. Prepare a graph of DE vs. mg toluene recovered. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition