CHARACTERIZATION OF BUFFERS FOR ELECTROKINETIC SEPARATIONS

Buffers used in electrophoresis and electrochromatography must have a relatively low ionic strength in order to minimize ohmic heating in th e presence of an applied potential. Calculation of pH, ionic strength, and the van Slyke buffer capacity, beta is therefore important. This paper describes the a priori calculation of these parameters for tris buffer made up with either glycine (a zwitterion) or HCl. A quadratic expression for pH, valid over wide ranges, is obtained for both buffer systems. The calculated values of pH, ionic strength, and buffer capa city are shown to agree with experimental results as a function of tri s, HCl, and glycine concentrations ranging from 1 to 50 mM. A new para meter, the electrokinetic buffer effectiveness factor, is introduced t o characterize buffers being considered for use in electrokinetic syst ems such as electrochromatography, and is used to determine the approp riate composition ranges for the buffer components.