Page:NIOSH Manual of Analytical Methods - 1401.pdf/2

 ALCOHOLS II: METHOD 1401, Issue 2, dated 15 August 1994 - Page 2 of 4 REAGENTS:

EQUIPMENT:

1. Eluent: Carbon disulfide* (chromatographic grade) with 1% (v/v) 2-propanol and 0.2% (v/v) n-undecane, 0.1% (v/v) hexane or other suitable standard. 2. Analyte. 3. DE stock solution, 100 mg/mL. Prepare solutions of each analyte in heptane. 4. Nitrogen, purified. 5. Hydrogen, prepurified. 6. Air, compressed, filtered.



See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4-mm ID, flame-sealed ends, 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 foam plug follows the back section. Pressure drop across the tube at 1 L/min airflow must be less than 3.4 kPa. Tubes are commercially available. 2. Personal sampling pump, 0.01 to 0.2 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 1401-1). 4. Vials, glass, 2-mL, PTFE-lined crimp caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Volumetric flasks, 10-mL.

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and an acute fire and explosion hazard (flash point = -30 °C); all work with it must be done in a hood.

SAMPLING: 1. 2. 3. 4.

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 between 0.01 and 0.2 L/min for a total sample size of 1 to 10 L (2 to 10 L for sec-butanol and isobutyl alcohol). Cap the samplers with plastic (not rubber) caps and pack securely for shipment.

SAMPLE PREPARATION: 5. 6. 7.

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

CALIBRATION AND QUALITY CONTROL: 8.

9.

Calibrate daily with at least six working standards covering the range of the samples. a. Add known amounts of analyte to eluent in 10-mL volumetric flasks and dilute to the mark. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (ratio of peak area of analyte to peak area of internal standard vs. mg analyte). Determine desorption efficiency (DE) at least once for each batch of charcoal used for sampling in the calibration range (step 8). Prepare three tubes at each of five levels plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94