Page:NIOSH Manual of Analytical Methods - 7029.pdf/3

 COPPER (dust and fume): METHOD 7029, Issue 2, dated 15 August 1994 - Page 3 of 4 c.

4. 5.

6.

7. 8.

Apply and release the vacuum so that the 37-mm filter is gently wetted from the moisture retained on the 47-mm filter. This also insures the removal of any air bubbles between the filters. d. When the fume sample is visually clear of air bubbles and wet throughout, apply a vacuum of 10 to 15 PSIG (69 to 103 kPa). Release the vacuum. e. Place a 47-mm, 5-µm cellulose ester membrane filter on the surface of water to wet it, remove excess water by blotting with tissue, and place it concentrically on top of the 37-mm filter. Press the surface of the top filter with a clean tissue to insure that no air bubbles remain between any of the filters. f. Mount the upper part of the filtration unit, add 5 mL of distilled water, and allow vacuum to draw water through the filters. Repeat with 5 mL more water. Combine the filtrates which contain soluble copper compounds in a clean beaker. Start reagent blanks at this point. g. Transfer all filters to a clean beaker. Proceed to step 5. NOTE: Each sample blank is a combination of three filters. Open the cassette filter holders and transfer the samples and blanks to clean beakers. Add 6 mL conc. HNO 3. Cover with a watchglass and heat on hotplate (140 °C) until the volume is reduced to approximately 0.5 mL. Repeat two more times using 2 mL conc. HNO 3 each time. NOTE: Start reagent blanks at this point if step 3 was omitted. Add 2 mL conc. HCl, cover with a watchglass, heat on hotplate (400 °C) until the volume is reduced to approximately 0.5 mL. Repeat two 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.

CALIBRATION AND QUALITY CONTROL: 9.

10. 11. 12. 13. 14.

Calibrate daily with at least six working standards. Add known amounts, covering the range 0 to 125 µg Cu per sample, of calibration stock solution to 25-mL volumetric flasks and dilute to volume with 0.5 N HCl. Analyze the working standards together with the blanks and samples (steps 15 and 16). Prepare a calibration graph by plotting absorbance versus solution concentration (µg/mL). Aspirate a standard for every 10 samples to check instrument drift. Check analytical recoveries with at least one spiked media blank per 10 samples. Use method of additions occasionally to check for interferences.

MEASUREMENT: 15. 16.

Set spectrophotometer as specified by the manufacturer and to conditions on page 7029-1. Aspirate standards, samples, and blanks. Record absorbance readings. NOTE: If the absorbance values for the samples are above the linear range of the standards, dilute the sample solutions with 0.5 N HCl, reanalyze, and apply the appropriate dilution factor in the calculations.

CALCULATIONS: 17. 18.

Using the measured absorbances, calculate the corresponding concentrations (µg/mL) of copper 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 of copper in the air volume sampled, V (L):

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94