Reverse Polarity Capillary Zone Electrophoretic Analysis of Nitrate and Nitrite in Natural Water Samples

This paper describes the application of reverse polarity capillary zone electrophoresis (CZE) for rapid and accurate determination of nitrate and nitrite in natural water samples. Using hexamethonium bromide (HMB) as an electroosmotic flow modifier in a borate buffer at pH 9.2, the resolution of nitrate and nitrite was accomplished in less than 3 min. CZE was compared with ion chromatographic (IC) and cadmium reduction flow injection analysis (Cd−FIA) methods which are the two most commonly used standard methods for the analysis of natural water samples for nitrate and nitrite. When compared with the IC method for the determination of nitrate and nitrite, CZE reduced analysis time, decreased detection limits by a factor of 10, cut laboratory wastes by more than 2 orders of magnitude, and eliminated interferences commonly associated with IC. When compared with the cadmium reduction method, CZE had the advantage of simultaneous determination of nitrate and nitrite, of being able to be used in the presence of various metallic ions that normally interfere in cadmium reduction, and of decreased detection limits by a factor of 10.