HEXACHLORO-1,3-CYCLOPENTADIENE: METHOD 2518, Issue 2, dated 15 August 1994 - Page 3 of 4 a. Add known amounts (5 to 140 µL) of calibration stock solution to hexane 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. ng hexachloro-1,3-cyclopentadiene). 9. Determine desorption efficiency (DE) at least once for each lot of Porapak T used for sampling in the range 25 to 12,500 ng hexachloro-1,3-cyclopentadiene per sample. Prepare three tubes at each of five levels plus three media blanks. a. Prepare five DE standard solutions in the range 5 to 2500 µg/mL by diluting aliquots of 20 mg/mL stock solution with hexane. b. Inject 5 µL of a DE standard solution directly into a media blank front sorbent section with a microliter syringe. c. Cap the tube. Allow to stand 12 hrs at room temperature. d. Desorb (steps 5 through 7) and analyze together with working standards (steps 11 and 12). e. Prepare a graph of DE vs. ng hexachloro-1,3-cyclopentadiene recovered. 10. 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 2518-1. Prior to analyzing samples, condition the column by making three 5-µL injections of a 1-µg/mL solution of hexachloro-1,3-cyclopentadiene in hexane. Inject sample aliquot manually using solvent flush technique or with autosampler. t r = 7 min for these conditions. NOTE: If peak area is above the useful range of the working standards, dilute with hexane, reanalyze and apply the appropriate dilution factor in calculations. 12. Measure peak area or height.
CALCULATIONS: 13. Determine the mass, ng (corrected for DE) of hexachloro-1,3-cyclopentadiene found in the sample front (W f) and back (W b) sorbent tubes, and in the average media blank front (B f) and back (B b) sorbent tubes. NOTE: If W b > W f/10, report breakthrough and possible sample loss. 14. Calculate concentration, C, of hexachloro-1,3-cyclopentadiene in the air volume sampled, V (L):
EVALUATION OF METHOD: A variation of this method employed single 100- or 50-mg sections of Porapak T per sampler. This variation was tested with controlled atmospheres and verified with impingers containing hexane and with gas chromatographic analysis for 13.1 to 873 µg/m 3 [1]. Overall precision ( SˆrT) was 0.082 (18 samples, pooled) for 2.9-L samples; the temperature of each atmosphere was 25 to 28 °C, and the relative humidity was at least 90%. Mean recovery for three concentration levels was 99.7%. The average concentration found at each level was not significantly different from the corresponding reference concentration at 95% confidence level. Breakthrough (1 mg/m 3, 0.2 L/min, 27 °C, RH 90%) = 55 L for a 50-mg section of Porapak T. Values of DE from 50 mg of Porapak T with 1 mL of hexane were 1.01, 0.99, and 1.01 for 24.5, 352, and 3670 ng per sample, respectively; Sr = 0.030 (18 samples, pooled). Hexachloro-1,3-cyclopentadiene (about 30 ng per sample) was stable for 28 days inside each tube which contained 100- and 50-mg sections of Porapak T (samples were stored at room temperature for the first seven days and at 0 °C for the next 21 days). However, hexachloro-1,3-cyclopentadiene did NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
