ELECTROPHORETIC SELECTIVITY AS A FUNCTION OF OPERATING PARAMETERS IN FREE SOLUTION CAPILLARY ELECTROPHORETIC SEPARATION OF DIPEPTIDES

Free-solution capillary electrophoretic separation of some dipeptides were carried out under acidic and alkaline conditions. The reproducibility of two migration parameters (migration time and relative migration time) for some dipeptides was examined under various operating conditions. ''The electrophoretic selectivity ''or relative migration time which is defined as the ratio of the migration time of test component to that of the reference standard shows better reproducibility than migration time. In addition, better reproducibility in migration times was obtained -from the capillary previously stored in acidic conditions for a certain period of time. Migration times of a neutral marker (t(o)) and dipeptides (t(m)) and relative migration times were examined as functions of operating column temperature and applied current(I). A quantitative linear correlation between logarithm of migration time (log t(o) or log t(m)) and the reciprocal of column temperature (1/T) under constant applied voltage has been derived . Plots of the reciprocal of migration times (1/t(m)) for dipeptides versus the applied current(I) yielded parallel lines. The parallel linear relationships between log t(m) and 1/T, 1/t(m) and I implied that the electrophoretic selectivity was independent of column temperature and operating current.