Page:NIOSH Manual of Analytical Methods - 2005.pdf/2

 NITROAROMATIC COMPOUNDS: METHOD 2005, Issue 3, dated 15 January 1998 - Page 2 of 5 EQUIPMENT:

REAGENTS:

1. Sampler: glass tube, 7 cm long, 6-mm OD, Methanol, HPLC chromatographic grade. 4-mm ID, flame-sealed ends with plastic Nitrobenzene*, reagent grade. caps, containing two sections (front=150 mg; o-,m-,p-nitrotoluene isomers,* reagent grade. back=75 mg) of 20/40 mesh silica gel 4-chloronitrobenzene*, reagent grade. separated by a 2-mm urethane foam plug. Calibration stock solution, 500 µg/mL. Prepare A silylated glass wool plug precedes the front each analyte in methanol. section and a 3-mm urethane foam plug 6. Helium, purified and filtered. follows the back section. 7. Hydrogen, purified and filtered. 2. Personal sampling pump, 0.01 to 1 L/min, 8. Air, purified and filtered. with flexible connecting tubing. 3. Gas chromatograph, FID, integrator and column (page 2005-1). 4. Autosampler vials, glass, 2-mL, with PTFElined crimp caps. 5. Volumetric flasks, 10-mL. 6. Pipets, 5-mL and 3-mL, with pipet bulb. 7. Syringes, 10-µL, 100-µL, and 1-mL. 8. Ultrasonic bath. 1. 2. 3. 4. 5.
 * See SPECIAL PRECAUTIONS

SPECIAL PRECAUTIONS: These analytes are severe poisons and irritants. Prevent contact with eyes, skin, or clothing by wearing eye protection, chemically resistant gloves, and a lab coat. Avoid inhalation. Nitrobenzene and m-nitrotoluene are absorbed through contact with skin and can cause methemoglobinemia [5,6]. 4-Chloronitrobenzene is a carcinogen. Methanol is highly flammable.

SAMPLING: 1. Calibrate each personal sampling pump with a representative sampler in line. 2. Break the ends of the sampler immediately before sampling. Attach sampler to personal sampling pump with flexible tubing. 3. Sample at an accurately known flow rate between 0.01 and 0.2 L/min for nitrotoluene isomers. Use a flow rate of 1 L/min or less for nitrobenzene and 4-chloronitrobenzene. Note the maximum and minimum sample volumes on page 2005-1. 4. Cap both ends of the sampler. Pack securely for shipment.

SAMPLE PREPARATION: 5. Place the front (include the glass wool plug) and back sorbent sections of each sample tube in separate vials. Discard the foam plugs. 6. Add 1.0 mL of methanol to each vial. Attach crimp cap securely to each vial. 7. Allow to desorb 30 min in an ultrasonic bath.

CALIBRATION AND QUALITY CONTROL: 8. Calibrate daily with at least six working standards to cover the analytical range of the method. If necessary, additional standards may be added to extend the calibration curve. a. Add known amounts of calibration stock to methanol 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 µg analyte). 9. Determine desorption efficiency (DE) at least once for each lot of silica gel used for sampling in the calibration ranges (step 8). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition