Buffer Considerations for LC and LC-MS

Abstract

In this article, the buffer capacity concept is revisited, particularly concerning its behavior in hydroorganic mobile phases. The buffer capacity of a polyprotic acid, or a mixture of monoprotic acids, depends upon the concentration of each weak acid-conjugate base pair, and the pH of its maximum value mainly fits to the acid-base pKA, but it is shifted to a certain degree according to the ionic strength of the buffered solution. Consequently, when an organic solvent is added to an aqueous buffer to prepare a particular mobile phase, the buffer capacity of the hydroorganic mixture is reduced due to the dilution effect, and the maximum buffer capacity is shifted to lower or higher pH values according to the nature of the buffering acid-base pair.