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Cobalt and compounds, as Co: Method 7027, Issue 2, dated 15 August 1994 - Page 3 of 3 13. 14. 15. 16.

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: 17. 18.

Set spectrophotometer according to the manufacturer's recommendations and to the conditions on page 7027-1. 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 5% HNO3, reanalyze, and apply the appropriate dilution factor in the calculations.

CALCULATIONS: 19. 20.

Using the measured absorbances, calculate the corresponding concentrations (µg/mL) of cobalt in the sample, Cs, and average media blank, Cb, from the calibration graph. Using the solution volumes (mL) of the sample, V s, and media blanks, Vb, calculate the concentration, C (mg/m3), of cobalt in the volume of air sampled, V (L):

C

NOTE: µg/mL

( CsVs

CbVb ) V

, mg/m 3.

mg/m3

EVALUATION OF METHOD: 3 Method S203 [2] was issued on February 18, 1977, and validated over the range 0.03 to 0.22 mg/m Co fume and 0.04 to 0.26 mg/m3 Co dust using spiked filters and generated atmospheres of cobalt dust and fume (Co2O3) [1]. Precision and accuracy data are given on page 7027-1. A separate check on this method showed 98% recovery from filters spiked with 12 or 96 µg soluble Co [3].

REFERENCES: [1] Documentation of the NIOSH Validation Tests, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-185 (1977). [2] NIOSH Manual of Analytical Methods, 2nd ed., V. 4, Method S203, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 78-175 (1978). [3] User check, UBTL, NIOSH Seq. #3990-N (unpublished, November 29, 1983). [4] 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).

METHOD REVISED BY: Mark Millson, NIOSH/DPSEand R. DeLon Hull, Ph.D., NIOSH/DSHEFS; S203 originally validated under NIOSH Contract CDC-99-74-45.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition

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