SULFURYL FLUORIDE: METHOD 6012, Issue 1, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 10.
11.
Calibrate daily with at least six working standards. NOTE: Standards should be spiked onto charcoal tubes as follows to avoid high recoveries seen with liquid standards [3]. a. Add known amounts of calibration stock solution onto charcoal tubes (5.0 to 80 µg F -) and desorb in the same manner as field samples (steps 5 through 9). b. Analyze working standards together with samples and blanks (steps 12 through 14). c. Prepare a calibration graph of peak height vs. amount (µg) of fluoride per 20 mL of sample. (Optional). Determine recovery (R) for each lot of tubes used for sampling in the concentration range of interest. Prepare four tubes at each of five levels plus three media blanks. a. Collect a known amount of SO 2F2 gas onto each charcoal tube (steps 1 through 9). b. Analyze samples in the same manner as field samples (steps 12 through 14). c. Prepare graph of recovery vs. µg sulfuryl fluoride.
MEASUREMENT: 12. 13. 14.
Set ion chromatograph to conditions given on page 6012-1. Re-filter sample if necessary, then inject a sample aliquot into the ion chromatograph. Measure peak height.
CALCULATIONS: 15. 16.
Determine mass (µg) of fluoride found on the front (W f) and back (W b) sections, and in the average media blank front (B f) and back (B b) sorbent section. Calculate concentration C of sulfuryl fluoride (mg/m 3) in the actual air volume, V(L), applying the conversion factor 2.686 (MW SO 2F2/MW F -; the reaction is SO 2F2 + 4NaOH → 2NaF + Na 2SO 4 + 2H 2O):
EVALUATION OF METHOD: This method was evaluated over the range 20 to 420 mg/m 3. Overall sampling and measurement precision, SˆrT, was 0.070 [1]. The average recovery of SO 2F2 from charcoal was 99% when sampling atmospheres prepared in aluminized gas bags (Calibrated Instruments, Inc., Hawthorne, NY 10532). Recovery of fluoride from sampling media was 97% in the range 10 to 160 µg F - per sample. Sample stability during storage was evaluated at 417 mg/m 3 SO 2F2 per sample. Samples showed 101% recovery after twelve days of storage at 0-5 °C compared to one-day old samples. REFERENCES: [1] [2] [3] [4] [5]
Williamson, G.Y. Backup Data Report for Sulfuryl Fluoride. NIOSH/MRSB Internal Report (unpublished) (1991). Analysis of NIOSH Samples for Sulfuryl Fluoride, NIOSH/MRSB Sequence #7161-A, (unpublished, May 13, 1991). Analysis of NIOSH Samples for Sulfuryl Fluoride, NIOSH/MRSB Sequence #7691-D (unpublished, January 27, 1993). Bouyoucos, S.A., Melcher, R.G., and Vaccaro, J.R., Collection and Determination of Sulfuryl Fluoride in Air by Ion Chromatography, Am. Ind. Hyg. J., 44, 57-61 (1983). NIOSH Manual of Analytical Methods, 2nd. ed., V. 6, S245, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 80-125 (1980). NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
