Determination of nitrites and nitrates in drinking water using capillary electrophoresis

This work was concerned with developing an electrophoretic method for rapid determination of nitrites and nitrates in drinking water. The background electrolyte was Tris-HCl buffer with an addition of cetyltrimethylammonium chloride to reverse the electro-osmotic flow. Online preconcentration of samples using the field-amplified sample stacking method provided detection limits of 0.003 mg L-1 (i.e. 65 nM) for nitrites and 0.010 mg L-1 (i.e. 160 nM) for nitrates, which are sufficiently low for quality control of drinking water. The method was tested in a concentration range corresponding to real drinking water samples and the differentiation between nitrites and nitrates was sufficient for simultaneous determination of nitrites at their concentrations of the order of tenths of mg L-1 and nitrates at their concentrations of the order of units to tens of mg L-1. A number of authors have neglected this important aspect when concentrating only on achieving the lowest possible detection limits. Separation of the two analytes and iodate as an internal standard was achieved in only three minutes. Total analysis time including preconditioning was eight minutes.