Page:NIOSH Manual of Analytical Methods - 1405.pdf/2

 ALC OH OLS CO MB INED : MET HO D 140 5, Issue 1, dated 15 M arch 200 3 - Page 2 o f 6 EQUIPMENT:

REAGENTS: 1. 2. 3. 4. 5.

6. 7. 8. 9. 10.

Ca rbon disulfide, chrom atog raph ic grade.* 2-Propa nol, ch rom atog raph ic grade.* He xan e, chrom atog raph ic grade.* He ptan e, chrom atog raph ic grade.* Desorbing solution: Carbon disulfide with 5% (v/v) 2-propanol and 0.05% (v/v) hexane as an internal standard. NOT E: n-Undecane, 0.1 (v/v) or other suitable standard can be used. Analyte(s). Stock solution, 100 mg/mL. Prepare solutions of each analyte in heptane. Nitrogen, purified. Hydrogen, prepurified. Air, compressed, filtered.

1. Sam pler: Glass tube, 7-cm long, 6-mm OD, 4mm ID, flame-sealed ends, containing two sectio ns of a ctivate d (6 00 °C) coconut s hell charcoal (front - 100 mg; back - 50 mg) separated by a 2-mm urethane foam plug follows the back section. Pressure drop across the tube at 1 L/min airflow must be less tha n 3.4 k Pa. Tubes are com m ercially available. 2. Personal sampling pump, 0.01 to 0.2 L/min, with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and colum n (page 14 05-1). 4. Vials, glass, 2-mL, PTFE -lined crimp caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Volumetric flasks, 2 mL.


 * See SPECIAL PRECAUTIONS

SPE CIAL PR ECAU TIO NS: 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. Propanol, hexane, and heptane are flamm able. Analytes should be han dled in a fume hood. W ear gloves, safety glasses, and app ropriate protective clothing.

SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break the ends of the sampler imm ediately before sampling. Attach sampler to personal sampling pump with flexible tubing. 3. Sam ple at a n ac curately kn own flow ra te betwee n 0.01 an d 0.2 L/m in for a total sam ple size of 1 to 10 L (2 to 10 L for n-butan ol, sec-butanol, and isobutyl alcohol). 4. Ca p the sam plers with plastic (not rub ber) cap s and pa ck sec urely for shipm ent.

SAMPLE PREPARATION: 5. Place the front and back sorbent sections of the sampler tube in separate vials. Discard the glass wool and foam plugs. 6. Ad d 1.0 m L desorbing solution (DS) to each vial. Attac h crim p cap to each vial. 7. Allow to stand 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTRO L: 8. Calibrate daily with at least six working standards covering the range of samples. a. Add know n am oun ts of a nalyte to D S in 2-m L volum etric flas ks and dilute to the m ark. b. Analyze together with samp les and blanks (steps 11 and 12). c. Prepare calibration graph (ratio of peak area of analyte to peak area of internal standard vs. µg analyte. 9. Dete rm ine desorption efficiency (DE) at least once for each batch of c harcoal used for sam pling in the calibration range (step 8). Prepare three tubes at each of five levels plus tree media blanks. a. Rem ove and disca rd back sorbent sec tion of a med ia blank sam pler. b. Inject a known amount of stock solution directly onto front sorbent section with a microliter syringe. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition