ZINC and compounds, as Zn: METHOD 7030, Issue 2, dated 15 August 1994 - Page 3 of 3 CALIBRATION AND QUALITY CONTROL: 10. 11. 12. 13. 14. 15.
Add known amounts, covering the range 0 to 100 µg Zn per sample, of calibration stock solution to 100-mL volumetric flasks and dilute to volume with 1% HNO3. Analyze the working standards together with the samples and blanks (steps 16 and 17). Prepare a calibration graph of absorbance vs. solution concentration (µg/mL). Aspirate a standard for every 10 samples to check instrument drift. Check recoveries with at least one spiked media blank per 10 samples. Use method of standard additions occasionally to check for interferences.
MEASUREMENT: 16.
17.
Set spectrophotometer according to manufacturer's recommendations and to conditions on page 7030-1. NOTE: Non-atomic absorption may require the use of D2 or H2 continuum background correction in some samples. Aspirate standards and samples. Record absorbance readings. NOTE: If the absorbance values for the samples are outside of the range of the standards, dilute the solutions with 1% HNO3, reanalyze, and apply the appropriate dilution factor in the calculations.
CALCULATIONS: 18. 19.
Using the measured absorbances, calculate the corresponding concentrations (µg/mL) of zinc in the sample, Cs, and average media blank, Cb, from the calibration graph. Using the solution volumes (mL) of the sample, Vs, and media blanks, Vb, calculate the concentration, C (mg/m3), of zinc in the volume of air sampled, V (L):
EVALUATION OF METHOD: Estimated LOD was 3 µg Zn per sample [2]. Since only the analytical procedure was studied, bias, overall precision, and accuracy were not determined.
REFERENCES: [1] [2] [3]
NIOSH Manual of Analytical Methods, 2nd ed., V. 5, P&CAM 173, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979). User check, UBTL, NIOSH Seq.# 3990-P (unpublished, November 29, 1983). Criteria for a Recommended Standard...Occupational Exposure to Zinc Oxide, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 76-104 (1976).
METHOD WRITTEN BY: Mark Millson, NIOSH/DPSE and R. DeLon Hull, Ph.D., NIOSH/DBBS.
NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
