Influence of pH and pK(a) values on electrophoretic behaviour of quinolones in aqueous and hydro-organic media

Through correct pH measurements, pK(a) and activity coefficient values, a m odel describing their effect on electrophoretic behaviour of substances is established. The suggested model uses the pH values in the acetonitrile-wat er mixtures used and takes into account the effect of activity coefficients . The model permits the calculation of acidity constants of analytes in hyd ro-organic media and also the prediction of the effect of pH on the electro phoretic mobility. The model is tested by determining the dissociation cons tants of a series of nine quinolones in acetonitrile-water mixtures of 0, 5 .5, 10 and 30% (w/w) acetonitrile. (C) 2000 Elsevier Science B.V. All right s reserved.