Determination of Cr(VI) in Natural and Waste Waters Using Differential Pulse Polarography (US EPA SW-846 Method 7198)

Abstract

The accurate determination of hexavalent chromium in environmental matrices such as natural and waste waters is crucial for the safety of both human and wildlife populations. The United States Environmental Protection Agency (U.S.EPA) has put forth SW-846, Method 7198, using differential pulse polarography for determination of Cr (VI) in both, the natural as well as waste waters. In Method 7198, the cathodic peak current resulting from the reduction of Cr (VI) to Cr (III) is measured and the concentration range for this method is listed as 10 ppb to 5 ppm Cr (VI). Using BASi Epsilon Potentiostat that is specifically made for measuring ultra-low current resolutions and a controlled growth mercury electrode (CGME) set-up, the US EPA method 7198 has been successfully optimized in this work for higher detection limits. It is observed that a detection limit of up to 7 ppb can be easily obtained by efficiently managing the interference of iron and Sulphur through a combination of various supporting electrolytes. This work may also become a valuable source of reference information on the behavior of wide variety of electrolytes and their control parameters needed to achieve extremely low detection limits. Figure 1