National Institute for Occupational Safety and Health

“ Prepare a series of standard filters using the 10 and 50 mg/L suspensions. Using appropriate pipets, prepare a sufficient number of standards in triplicate to cover the analytical range (or sample range if known) . Standards at 20, 30, 50 100, 200 and 500 μg are usually sufficient. Mount a filter on the filtration apparatus. Place several mL 2-propanol on the filter surface. Turn off the stirrer and shake vigorously by hand. ”

“ In this case, the net intensities of the analyte, I x, should be normalized to the most recently measured reference intensity. Prepare a calibration graph ( vs. μg analyte) . NOTE: Poor reproducibility at any given level indicates problems in the sample preparation technique and new standards should be made. The data should lie along a straight line. A weighted least squares (1/ σ2 weighting) is preferable. Curvature can be eliminated with absorption corrections based on the mass absorption coefficient of the analyte [7,8,9] . ”

“ The working range is 0.25 to 10 mg/m 3 for a 200-L air sample. The method does not distinguish zinc oxide fume from zinc oxide dust.
INTERFERENCES: Major interferences include Fe 2O 3, Zn, Zn (NH 3) 2Cl2, (NH 4) 3ZnCl 5, (NH 4) 2ZnCl 4 and (NH 4) 2Zn (SO 4) 2 6H 2O; these are resolved by using alternate analyte peaks. Particle size affects intensity measurements.
OTHER METHODS: This method combines and replaces Methods P&CAM 222 [1] and S316 [5] . The criteria document contains an elemental analysis for zinc [6] . ”