PROBLEMS ASSOCIATED WITH HEXAVALENT CHROMIUM DETERMINATION

The ability to demonstrate that industry products, waste materials and disposal sites are free of hexavalent chromium is of crucial regulatory importance to the leather tanning industry. this requires reliable techniques to extract and detect, without alteration, small quantities of CrVI from complex sample matrices in the presence of a large excess of CrIII as well as other potential interferents. EPA* solid waste methods 7195 (coprecipitation), 7196 (colorimetric) and 7197 (chelation/extraction) are not entirely suitable for this purpose as published, and require some modification to obtain reliable results. This report examines a number of case histories where false-positive CrVI results were reported in tannery-related materials by independent testing laboratories, and recommends procedures to be followed in order to avoid these problems. Method 7195 is not recommended for samples with a large excess of CrIII. Methods 7196 and 7197 can provide reliable results given reasonable care and validation.