Page:NIOSH Manual of Analytical Methods - 2513.pdf/3

 ETHYLENE CHLOROHYDRIN: METHOD 2513, Issue 2, dated 15 August 1994 - Page 3 of 4 b. c. 9.

10.

Analyze together with samples and blanks (steps 11 and 12). Prepare calibration graph (ratio of peak area of analyte to peak area of internal standard vs. µg ethylene chlorohydrin). 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 the back sorbent section of a media blank sampler. b. Inject a known amount (2 to 20 µL) of calibration stock solution, or a dilution thereof, 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 ethylene chlorohydrin 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 2513-1. 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, reanalyze, and apply the appropriate dilution factor in the calculations. Measure peak area. Divide the peak area of analyte by the peak area of internal standard on the same chromatogram.

CALCULATIONS: 13.

14.

Determine the mass, µg (corrected for DE) of ethylene chlorohydrin found in the sample front (W f) 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 ethylene chlorohydrin in the air volume sampled, V (L):

EVALUATION OF METHOD: Method S103 was issued on April 11, 1975 [2] and evaluated over the range 7 to 30 mg/m 3 at 25 °C and 742 mm Hg using a 20-L sample [1]. Overall precision, SˆrT, was 0.076 with an average recovery of 0.914. The concentration of ethylene chlorohydrin was independently verified using a GC-FID calibrated with gas mixtures of ethylene chlorohydrin in nitrogen. Breakthrough volume (effluent concentration = 5% of influent concentration) was >48 L; the test was conducted in dry air containing 31 mg/m 3 ethylene chlorohydrin with a sampling flow rate of 0.2 L/min. Desorption efficiency was 0.94 in the range 0.16 to 0.64 mg per sample. For the DE determination experiments, an 80 mg/mL solution of ethylene chlorohydrin in 2-propanol was used for spiking.

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