Page:NIOSH Manual of Analytical Methods - 1450.pdf/2

 EST ERS 1: MET HO D 145 0, Issue 3, dated 15 M arch 200 3 - Page 2 o f 6 REAGENTS:

EQUIPMENT:

1.

1. S am pler: glass tube, 7-cm long, 6-mm OD, 4m m ID, flame-sealed ends, containing two sections of activated (600 °C) coconut s hell charcoal (front - 100 mg; back - 50 mg) separated by a 2-m m ureth ane foam plug. A silylated glass wool plug precedes the front section and a 3-m m urethane foam plug follows the back section. Pressure drop across the tube at 1 L/m in airflow must be less than 3.4 kPa. Tubes are comm ercially available. 2. Personal sampling pump, 0.01 to 0.2 L /m in, with flexible connecting tubing. 3. Refrigerant, bagged (“Blue Ice,” or equivalent). 4. Gas chromatograph, FID, integrator and column (page 145 0-1). 5. Vials, glass, 2-mL, PTFE -lined crimp caps. 6. Syringe, 10-µL, readable to 0.1 µL, 25-, 50- and 100-µL. 7. Volumetric flasks, 10-mL. 8. Pip et, volumetric, 1-mL, with pipet bulb or repipet.

2. 3. 4. 5.

Desorbing solution: Carbon disulfide* (chromatographic grade) with 0.05% (v/v) nhexane or other suitable internal standard. Analyte, reagent grade. Helium, purified. Hydrogen, prepurified. Air, compressed, filtered.
 * See SPECIAL PRECAUTIONS

SPE CIAL PR ECAU TIO NS: Carbon disulfide is toxic and an acute fire and explosion hazard (flash point = -30 °C); work with it only in a hood. W ear appropriate protective clothing and gloves.

SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler tube in line. 2. Break the ends of the sampler tube immediately before sampling. Attach sampler tube to personal sampling pump with flexible tubing. 3. Sa m ple at an accurately known flow rate between 0.01 and 0.2 L/min for a total sam ple size of 1 to 10 L. 4. Cap the sam plers with plastic (not rubber) caps and pack securely for shipm ent w ith bag ged refrige rant.

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 to each vial. Attac h crim p cap to each vial. 7. Allow to stand 30 min with occasional agitation. NOTE: The desorption efficiency of 2-ethoxyethyl acetate has been found to decrease with the resident tim e of the des orbe d so lution with charcoal [4]. After 30 min desorption transfer the supernatant solution of 2-ethoxyethyl acetate to a clean 2-mL vial and seal with a crimp cap.

CALIBRATION AND QUALITY CONTRO L: 8. Calibrate daily with at least six working standards over the range 0.001 to 10 mg analyte per sample. a. Add k now n am ounts of analyte to desorbing solution in 10-mL volumetric flasks 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 ana lyte to pea k area o f internal stan dard vs.m g analyte).

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition