The accuracy and precision of a modified method of NIOSH Method 7600 and EPA method 218.6 was determined for analyzing hexavalent chromium, Cr(Ⅵ), collected on PVC filter from workplace air. The method was designed to extract from Cr(Ⅵ) on PVC filter with a alkali solution, 2% NaOH/3% Na₂CO₃, and to analyze it using ion chromatography/visible absorbance detection (IC/VAD). The results and conclusion are as the following.
1. The peak of Cr(Ⅵ) was separated sharply on chromatogram and was linearly related with Cr(Ⅵ) concentration in solution. The correlation coefficient was 0.9999 in a calibration curve. The limit of detection was 0.25 ㎍/sample.
2. The accuracy(% recovery) was 93.3% in a set of samples(9-50 ㎍) stored for a day, and 100.1 %(l0-60 ㎍) in another set of samples stored for 2 hours. It is assumed that the difference in recovery by storage time was due to reduction of Cr(Ⅵ) to (Cr(Ⅳ).
3. The precision(coefficient of variation, CV) of the method was 0.015 in spiked samples with Cr(Ⅵ) standard solution, and 0.010 in spiked samples with plating solution from a chrome electroplating factory. The overall CV in ail types of samples was 0.013.
4. The Cr(Ⅵ) was stable in 2% NaOH/3% Na₂CO₃ at least for 10 hours.
In conclusion, the IC/VAD method is appropriate for determining low-level Cr(Ⅵ) in workplace air containing various interferences.
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