National Institute for Occupational Safety and Health

“ 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. ”

“ 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. ”

“ HNO 3 each time. Add 2 mL conc. HCl, cover with a watchglass, and heat on hotplate (400 °C) until the volume is reduced to ca. 0.5 mL. Repeat 2 more times using 2 mL conc. HCl. Do not allow the solution to go to dryness at any point. Cool solution and add 10 mL distilled water. Transfer the solution quantitatively to a 25-mL volumetric flask. Dilute to volume with distilled water.
NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition, 8/15/94 CADMIUM and compounds, as Cd: METHOD 7048, Issue 2, dated 15 August 1994 - Page 3 of 4 CALIBRATION AND QUALITY CONTROL: 11. ”