Page:NIOSH Manual of Analytical Methods - 1500.pdf/2

 HYD RO CAR BO NS, BP 36-216 °C : MET HO D 150 0, Issue 3, dated 15 M arch 200 3 -Page 2 of 8 REAGENTS:

EQUIPMENT:

1. Eluent: Carbon disulfide *, low benzene, chrom ato graphic quality. 2. Analytes, reage nt gra de.* 3. Helium, prepurified and filtered. 4. Hydrogen, prepurified and filtered. 5. Air, prepurified and filtered.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4-mm ID, flame-sealed ends, containing two sections of activated 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. Tubes are comm ercially available. 2. Personal sampling pumps (0.01 to 1.0 L/min, Table 3) with flexible tubing. 3. Gas chromatograph, FID, integrator, and a Rtx-1 or equivalent capillary column (page 150 0-1). 4. Glass a utos am pler vials (2-m L) with PTFE-lined caps. 5. Pipettes (1-mL) and pipette bulb. 6. Syringes (10, 25, 100, and 250 µL). 7. Volum etric flasks (10-m L).


 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: Carbon disulfide is tox ic and extre m ely flam m able (flash point = -30°C ). Prepare samples and standards in a well-ventilated hood. SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break the ends of the sam pler im m ediately before sa m pling. Attach the sampler to a personal sampling pump with flexible tubing. 3. Sa m ple at an accurately known flow rate between 0.01 and 0.2 L/min (0.01 to 0.05 L/m in for n-pentane) for a total sample size as shown in Table 3. 4. Ca p the sam plers with plastic (not rub ber) cap s an d pa ck sec urely for shipm ent.

SAMPLE PREPARATION: 5. Place the front and back sorbent sections of the sampler tube in separate vials. Include the glass wool plug in the vial with the front sorbent section. Discard the foam plugs. 6. Ad d 1.0 m L carbon disulfide to each vial. Attac h crim p cap to each vial im m ediate ly. 7. Allow to stand at least 30 min with occasional agitation.

CALIBRATION AND QUALITY CONTRO L: 8. Ca librate daily with at leas t six wo rking standa rds from below the LOD to 10 times the LO Q. Additional sta ndards m ay be added to exte nd the calibra tion curve if ne cessary. a. Add known amounts of analytes to carbon disulfide in 10-mL volumetric flasks and dilute to the mark. Prepare additional standards by serial dilution in 10-mL volumetric flasks. b. Analyze with samp les and blanks (steps 11 and 12). c. Prepare a calibration graph (pe ak area of analyte vs. µg of analyte per sam ple). 9. Determine the desorption efficiency (DE) at least once for each batch of charcoal used for sampling in the calibra tion ran ge (s tep 8). a. Prepare three tubes at each of five levels plus three media blanks. b. Rem ove and disca rd the back sorbent sec tion of a med ia blank sam pler.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition