Page:NIOSH Manual of Analytical Methods - 2002.pdf/3

 AMINES, AROMATIC: METHOD 2002, Issue 2, dated 15 August 1994 - Page 3 of 6 SAMPLE PREPARATION: 5. 6. 7.

Place the front and back sorbent sections of the sampler tube in separate vials. Add the glass wool plug to the front sorbent section vial. Discard the foam plugs. Add 1.0 mL 95% ethanol to each vial. Attach crimp cap to each vial. Agitate 1 h in an ultrasonic bath.

CALIBRATION AND QUALITY CONTROL: 8.

9.

10.

Calibrate daily with at least six working standards over the range 0.01 to 3 mg analyte per sample. a. Add known amounts of calibration stock solution, or a dilution thereof, in n-hexane to 95% ethanol 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 or height vs. mg analyte). Determine desorption efficiency (DE) at least once for each lot of silica gel used for sampling in the calibration range. 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 (1 to 20 µL) of calibration stock solution, or a dilution thereof, in hexane directly onto front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. mg analyte recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.

MEASUREMENT: 11.

Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2002-1. Inject sample aliquot manually using solvent flush technique or with autosampler. Use the following conditions as a guide (these were used in development of the methods [1]):

COMPOUND Aniline o-Toluidine 2,4-Xylidine N,N-Dimethyl- p-toluidine N,N-Dimethylaniline

Injection 230 240 230 250 150

TEMPERATURES, °C Column 165 180 170 180 100 for 4 min, then 8°C/min to 225

Detector 245 265 235 250 250

NOTE: If peak response is above the linear range of the working standards, dilute with 95% ethanol, reanalyze, and apply the appropriate dilution factor in calculations. 12. Measure peak area or height.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94