Highly selective and efficient separations of a wide range of acidic species in capillary electrophoresis employing non-aqueous media

The novel application of CE using non-aqueous media has been studied for the separation of a range of acidic compound types. This enabled the first quantitative assay by CE employing non-aqueous media to be performed. Separation selectivity manipulation for closely related species was achieved through variation of organic solvent types and composition, ionic strength changes, alteration of pH* values and the addition of cyclodextrin additives soluble in organic solvents. This offers a greater range of possibilities during method development than use of aqueous buffer. The generation of low operating currents permitted rapid, highly efficient and selective separations to be achieved by applying high field strengths across short capillaries. Optimised rinsing and capillary regenerating procedures were devised which allowed highly repeatable separations to be achieved with migration time repeatability below 1 % RSD. Use of internal standards also allowed 1 %RSD values to be obtained for injection precision. Routine operating effects were assessed and it was observed that stacking effects remain important in non-aqueous CE. Also, optimal separations are obtained when the samples are diluted in the pure solvent used to prepare the electrolyte. The application range of non-aqueous CE was appreciably extended to include acidic drugs, dyes, surfactants and preservatives.