Page:NIOSH Manual of Analytical Methods - 1300.pdf/2

 KETONES I: METHOD 1300, Issue 2, dated 15 August 1994 - Page 2 of 5 REAGENTS: 1. 2. 3. 4. 5.

EQUIPMENT:

Carbon disulfide (CS 2) GC grade.* Analytes, reagent grade. Nitrogen, prepurified. Hydrogen, dry. Air, filtered, dry.



See SPECIAL PRECAUTIONS.

1. Sampler: glass tube, 7 cm long, 6-mm OD, 4mm ID, flame-sealed ends with plastic caps, 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 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 equipped with FID, integrator and column (page 1300-1). 4. Vials, 2-mL, glass, PTFE-lined crimp caps. 5. Syringe, 10-µL, readable to 0.1 µL. 6. Pipet, TD, 1-mL, with pipet bulb. 7. Volumetric flasks, 10-mL.

SPECIAL PRECAUTIONS: Carbon disulfide is toxic and an acute fire and explosion hazard (flash point = -30 °C); work with it only 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 0.5 to 3 L for acetone or 1 to 10 L for the other analytes. Cap the samplers and pack securely for shipment.

SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler in separate vials. Discard the glass wool and foam plugs. Add 1.0 mL CS 2 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 over the range 0.02 to 10 mg analyte per sample. a. Add known amounts of analyte to CS 2 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 (peak area vs. mg analyte). Determine desorption efficiency (DE) at least once for each lot 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. b. Inject a known amount of analyte or of a standard solution of analyte in CS 2 directly onto NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94