RESOLUTION AS A FUNCTION OF THE PH OF THE BUFFER BASED ON THE ANALYTE CHARGE NUMBER FOR MULTIVALENT IONS IN CAPILLARY ZONE ELECTROPHORESIS WITHOUT ELECTROOSMOTIC FLOW - THEORETICAL PREDICTION AND EXPERIMENTAL EVALUATION

The electrophoretic resolution, R, consists of two terms: the selectivity term (with the ratio of the effective mobilities as the selectivity coefficient) and the efficiency term. It was shown that the latter depends on the effective charge number of the separands as the only analyte-specific parameter, when solely longitudinal diffusion is causing peak broadening, and when electroosmosis does not occur. Both terms, and thus the resolution, depend on the pH of the buffering electrolyte. The resolution was calculated for all pairs of separands (polyvalent acids) as a function of the pH, with the pK values and the actual mobilities of the separands, based on the equations derived. That unique pH was calculated where a certain resolution is established within the shortest time. The theoretically predicted pH values for a given resolution were compared with the experimental data. An excellent agreement was found for di- and tribasic weak acids, where the pH could be predicted within few hundredths units.