DIMETHYL SULFATE: METHOD 2524, Issue 2, dated 15 August 1994 - Page 3 of 4 SAMPLE PREPARATION: 5. 6. 7.
Place the front and back sorbent sections of the sampler tube in separate vials. Discard the separating plugs. Add 1.0 mL diethyl ether to each vial. Attach crimp cap to each vial. Allow to stand 30 min with occasional agitation.
CALIBRATION AND QUALITY CONTROL: 8.
9.
10.
Calibrate daily with at least five working standards over the range 0.25 to 120 µg dimethyl sulfate per sample (2.5 to 1200 µg/10 mL). a. Add known amounts of calibration stock solution to 10-mL volumetric flasks and dilute to the mark with diethyl ether. b. Analyze together with samples and blanks (steps 11 and 12). c. Prepare calibration graph (peak area vs. µg dimethyl sulfate). Determine desorption efficiency (DE) at least once for each lot of Porapak P 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 calibration stock solution 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. µg dimethyl sulfate 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.
12.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 2524-1. Set electrolytic conductivity detector for operation in sulfur mode according to manufacturer's recommendations. Inject sample aliquot manually using solvent flush technique or with autosampler. NOTE: If peak area is above the linear range of the working standards, dilute an aliquot of the desorbed liquid with diethyl ether, reanalyze, and apply the appropriate dilution factor in calculations. Measure peak height.
CALCULATIONS: 13.
14.
Determine the mass, µg (corrected for DE) of dimethyl sulfate found in the sample front (W and back (W b) sorbent sections, and in the average media blank front (B f) and back (B b) sorbent sections. NOTE: If W b > W f/10, report breakthrough and possible sample loss. Calculate concentration, C, of dimethyl sulfate in the air volume sampled, V (L):
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
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