Measurement of pKa values of newly synthesized heteroarylaminoethanols by CZE

Heteroarylaminoethanol derivates are drugs which affect sympathetic nervous system and are used for medications of hypertensis. In solutions they behave like weak bases and their pKa values represent important information on their potential biological uptake, pharmacological activity and in vivo biodisponsibility. This article brings the measurement of pKa values of the series of seven new important heteroarylaminoethanols, compounds with potential vasodilating, β-adrenolytic and antioxidant activity, by capillary zone electrophoresis (CZE) with diode-array detection. It has been shown that capillary zone electrophoresis measurements of pKa can be easily performed with very small quantities of studied substances, and, due to CZE separation power, the purity of samples is not of key importance. Moreover, the CZE method is fast and reliable, providing that suitable operational conditions are selected. The method is based on the measurement of the effective mobility curves within a suitable pH range and related regression analysis where pKBH+ and electrophoretic mobility of BH+ are explicitly involved. The selection of sufficient operational buffers is of key importance for accurate and reproducible results, and, this article brings step by step the consideration procedure involved in this process. Further, this paper brings principles of least square regression analysis of non-linear function corresponding to exact explicit formula for mobility curve of monovalent weak base.