CADMIUM and compounds, as Cd: METHOD 7048, Issue 2, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 11.
12. 13. 14. 15. 16.
Calibrate daily with at least six working standards. Add known amounts, covering the range 0 to 30 µg Cd per sample, of calibration stock solution to 100-mL volumetric flasks and dilute to volume with 0.5 N HCl. Analyze the working standards together with the blanks and samples (steps 17 and 18). Prepare a calibration graph of absorbance vs. solution concentration (µg/mL). Aspirate a standard after every 10 samples to check for instrument drift. Check recoveries with at least 2 spiked media blanks per 10 samples. Use method of additions occasionally to check for interferences.
MEASUREMENT: 17. 18.
Set spectrophotometer according to manufacturer's recommendations and to conditions on page 7048-1. Aspirate standards and samples. Record absorbance readings. NOTE: If the absorbance values for the samples are above the linear range of the standards, dilute the solutions with 0.5 N HCl, reanalyze, and use the appropriate dilution factor in calculations.
CALCULATIONS: 19. 20.
Using the measured absorbances, calculate the corresponding concentrations (µg/mL) of cadmium in the sample, C s, and average media blank, C b, from the calibration graph. Using the solution volumes (mL) of the sample, V s, and media blanks, V b, calculate the concentration, C (mg/m 3), of cadmium in the volume of air sampled, V (L):
EVALUATION OF METHOD: Method S312 was issued on June 12, 1976 [4], and validated over the range 0.12 to 0.98 mg/m 3 for a 25-L sample of CdO dust [1]. Method S313 was issued on November 26, 1976 [6], and validated over the range 0.12 to 0.57 mg/m 3 for a 25-L sample of Cd fume, and over the range 0.04 to 0.18 mg/m 3 for a 140-L sample of Cd fume [1].
REFERENCES: [1] Documentation of the NIOSH Validation Tests, S312 and S313, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977). [2] User check, UBTL, NIOSH Seq. #3990-M (unpublished, November 29, 1983). [3] Current Intelligence Bulletin 42: Cadmium. U.S. Department of Health and Human Services, Publ. (NIOSH) 84-116 (Sept. 27, 1984). [4] NIOSH Manual of Analytical Methods, V. 3, Method S312, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157-C (1977). [5] Ibid, 2nd ed., V. 5, P&CAM 173, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979).
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
