Page:NIOSH Manual of Analytical Methods - 1007.pdf/3

VINYL CHLORIDE: METHOD 1007, Issue 2, dated 15 August 1994 - Page 3 of 4 SAMPLE PREPARATION: 5. 6. 7. 8.

Add 1.0 mL CS 2 to an empty vial. Loosely cap the vial. Score each sampler tube with a file in front of the glass wool plug. Break the tube at the score line. Transfer the charcoal from the front and back tubes to separate vials. Discard the glass wool and foam plugs. Seal the vials with septum caps immediately. Allow to stand for 30 min, with occasional agitation. Analyze the sample within the next 30-min period.

CALIBRATION AND QUALITY CONTROL: 9.

10.

Calibrate with at least six working standards covering the range 0.2 to 200 µg per sample. a. Add known amounts of calibration stock solution to CS 2 in 10-mL volumetric flasks and dilute to the marks, using serial dilution as appropriate. NOTE: Working standards can be stored at -20 °C for at least three days. b. Analyze together with samples and blanks (steps 12 and 13). c. Prepare calibration graphs of peak area vs. quantity (µg) of vinyl chloride per tube and peak area vs. quantity (ng) per injection. Determine desorption efficiency (DE) at least once for each lot of charcoal used in the calibration range (step 9). Prepare three tubes at each of five levels plus three media blanks. a. Prepare three atmospheres of vinyl chloride in air by injecting 0.01, 0.08, and 0.2 mL vinyl chloride gas into 10 L air in Tedlar bags. The resulting concentrations are approximately 2.6, 21 and 52 mg/m 3. b. Following steps 1 through 4, sample these atmospheres according to the following scheme: Concentration in Bag (mg/m 3)

Volume Sampled (L)

Quantity of Vinyl Chloride (µg)

2.6

0.8 2.2 0.8 2.2 2.5

2 6 17 46 130

21 52

Obtain three samples at each level. Desorb (steps 6 through 8) and analyze together with working standards (steps 12 and 13). No vinyl chloride should be found on the back tubes. d. Analyze the atmospheres in the bags (steps 12 and 13) using 1-mL gas samples to verify concentration. e. Prepare a graph of DE vs. µg of vinyl chloride recovered. Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control. c.

11.

MEASUREMENT: 12.

13.

Set the gas chromatograph according to manufacturer's instructions and to conditions given on page 1007-1. Inject sample aliquot manually using solvent flush technique or with autosampler. The retention time of vinyl chloride is about 1.7 min. NOTE: If peak area is above the linear range of the working standards, dilute with CS 2, reanalyze and apply the appropriate dilution factor in calculations. Measure peak area.

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