Determination of Chlorite in Drinking Water Using Capillary Electrophoresis with Amperometric Detection

Abstract

Capillary electrophoresis with end-column electrochemical detection (CEEC) was used to determine chlorite (ClO2–1) in drinking water. Two CE methods were developed. The first method used a positive CE polarity with a 25 mM Borate buffer, pH 8.9. The second method used a negative CE polarity and a 25 mM phosphate buffer, pH 7.5 with 1 mM dodecyl trimethyl ammonium bromide (DTAB) added to reverse the EOF. The required detection potential was +1.0 V (vs. Ag/AgCl) in the positive polarity mode and +0.90 V (vs. Ag/AgCl) in the negative polarity mode. In both polarity modes, the analysis time for chlorite was less than 6 minutes. Calibration plots ClO2– in tap water and in deionized water were found to be linear between 0.1 and 10 mg L–1(r≥0.994) with detection limits of 5 μg L–1 (S/N=3) in both modes. The concentration of chlorite found in samples from a water treatment plant was 0.5 to 1.7 mg L–1. The relative standard deviation (RSD) in peak height for injections of 1.0 mg L–1 chlorite standards were 5.4 % using the positive polarity mode and 2.7 % using the negative polarity mode. The RSD in peak height for injections of samples from the water treatment plant were 5.2 % and 6.6 % for positive and negative polarity, respectively (n=5).