Capillary electrophoresis separation of alkylphosphonic acid monoesters with indirect ultraviolet detection

The separation of two series of alkylphosphonic acid monoesters (methyl and ethyl) by capillary electrophoresis (CZE) with indirect UV detection is described. In order to get short run times and high peak efficiencies the electroosmotic flow (EOF) is reversed by flushing the fused-silica capillary with 0.2% aqueous solution of polybren. The optimisation of several experimental parameters (running voltage, temperature) has been carefully investigated, and resolution, peak efficiency were studied. The signal-to-noise ratio and the repeatability of the EOF were investigated by adding hydroxylamine to the electrolyte system, to improve the buffer capacity. Thus, the electrolyte, composed of 5 mM sorbate anion (pH 6) as background absorbance co-anion and 1.6 mM hydroxylamine, allows the separation of these alkylphosphonic acid monoesters in less than 6 min. (C) 1997 Elsevier Science B.V.