Analytical Expediency of Acidic and Alkaline Background Electrolytes in Capillary Zone Electrophoresis: Role of System Zones in Single-Co-Ion Systems

Abstract

Acidic and alkaline background electrolytes (BGEs) are very useful in capillary zone electrophoresis since they offer high selectivity in many cases. They are usually prepared by dissolving a weak base or weak acid and titrating to the required pH with a strong acid or strong base, respectively. At first glance, these background electrolytes appear to be very simple and to present no problems to optical detection. In this paper, it is shown that such systems may, however, be the source of serious problems that stem from the fact that they behave as those with a binary co-ion. The H+ or OH- ions act here as the second co-ion, and consequently system peaks are formed that lessen the usefulness of such background electrolytes. Moreover, an important case is demonstrated and discussed where a second system peak appears in weak alkaline BGEs due to the omnipresent carbonate. This paper presents the theory, related experiments, and practical hints to interpret correctly the patterns of capillary zone electrophe...