A fast method for pKa determination by capillary electrophoresis.

In this article, we describe a recently developed capillary-electrophoresis method for the determination of acidity constants and compare it with other existing methods. The new method is based on the use of an internal standard (compound similar in nature and pKa value to the analyte), and offers several benefits, since it has all the advantages of capillary electrophoresis. In addition, it is very fast, because the exact measure of the pH of the separation electrolytes is not needed, and only a few electrophoretic runs are required to perform a pKa determination. The acidity constants of some monoprotic weak acids and bases were determined by this fast method, yielding a very good agreement with literature values.