ETHYLENE GLYCOL: METHOD 5500, Issue 2, dated 15 August 1993 - Page 3 of 3 b. c. d.
9.
Add a known quantity of ethylene glycol in 5 µL water solution to the filter. Seal the vial; ultrasonicate for 15 to 30 minutes. Prepare and analyze the filters together with working standards (steps 5, 6, and 10 through 12). e. Calculate recovery (ethylene glycol recovered/ethylene glycol taken). Determine DE from silica gel for each lot of silica gel in the range of interest. Prepare three tubes at each of five levels plus three media blanks. a. Draw ethylene glycol vapor with a pump at 0.2 L/min into sampler tubes with a pump from a U-tube partly immersed in a constant temperature bath at 75 °C. NOTE: Values of DE for liquid and vapor spikes may be different [3]. b. Desorb (steps 5 and 6) and analyze (steps 10 through 12) together with working standards. c. Prepare a graph of DE vs. mg ethylene glycol recovered.
MEASUREMENT: 10. 11. 12.
Set gas chromatograph according to conditions given on page 5500-1. Set flow rates of hydrogen and air according to manufacturer's instructions. Inject sample aliquot manually using solvent flush technique or with autosampler. t r = 4 min for ethylene glycol under these conditions. Measure peak area or peak height.
CALCULATIONS: 13.
14.
Determine the mass, mg (corrected for recovery or DE) of ethylene glycol found on the filter (W) and in the sample tube front (W f) and back (W b) sorbent sections, and in the average media blank filter (B), and 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 glycol in the air volume sampled, V (L):
EVALUATION OF METHOD: The method was tested with spiked samplers and atmospheres generated with a diffusion cell and verified with bubblers of water followed by colorimetric analysis for 54 to 98 mg/m 3. S r = 0.084 (six samples) for 6-L samples at 14 mg/m 3 (aerosol); Sr = 0.065 (17 samples, pooled) for 6-L samples at 45 to 84 mg/m 3 (vapor). Breakthrough volume (79 mg/m 3, 0.2 L/min) = 261 L; recovery from filters (20 to 900 mg per sample) = 1.02; DE from silica gel (20 to 3120 µg per sample) = 0.81 to 0.87; filter storage stability = 49% of 85 mg evaporated from filters during 4 h at 24 °C, 78 µg stable on silica gel for 15 days at 25 °C. Area samples were collected side by side for 4 h at a field location by this method and a reference method (bubblers and colorimetric analysis); concentrations by this method, 0.63, 0.59, and 0.23 mg/m 3, were 1.4, 0.7 and 26.5% higher than corresponding concentrations by the reference method. REFERENCES: [1] Tucker, S. P., and G. J. Deye. Anal. Lett., 14 (A12), 959-976 (1981). [2] Spitz, H. D. J. Pharm. Sci., 1339-1340 (1972). [3] NIOSH Manual of Analytical Methods, 2nd ed., V. 7, P&CAM 338, U.S. Department of Health and Human Services, Publ. (NIOSH) 82-100 (1981). METHOD WRITTEN BY: Samuel P. Tucker, Ph.D., and Gregory J. Deye, NIOSH/DPSE. NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/93
