Dynamic control for the separation of organic acids in capillary electrophoresis

A new and very simple technique has been developed in capillary zone electrophoresis for the separation of organic acids. In this new method, capillaries were simply treated with 0.1 M NaOH via high pressure for 3 min, then flushed with running buffer solutions via high pressure for 10 s before performing separation. After this treatment, electroosmotic flow (EOF) is higher than electrophoretic mobilities (EPM) of all analytes in weak acidic conditions. Thus, eight organic acids are well separated in less than 7 min at an applied voltage of 22 kV. In addition to significant differences of EPM among analytes in weak acidic conditions, dynamic changes in EOF and pH account for the good separation results. Capillary dimensions, ionic strength and type of buffer solution all show dramatic effects on the separations of organic acids. The results also support the existence of dynamic changes in the system during a run. This new method provides the advantages of reproducibility, speed and simplicity for the separation of organic acids which cannot be easily separated in the range of pH 4-6 by any conventional means.