Theory and computer programs for calculating solution pH, buffer formula, and buffer capacity for multiple component system at a given ionic strength and temperature.

Abstract

A theory and computer programs running on Microsoft Excel for Windows for calculation of solution pH, buffer formula, and buffer capacity at a given ionic strength and temperature were developed. The theory does not limit the category of buffer components, the number of buffer components, or the number of ionizations for each buffer component. The usefulness of the programs was examined. The formulas for 7 single component buffer solutions and 2 multiple component buffer solutions composed of citrate, phosphate, Tris, borate, and glycine were calculated. The solution pH values were measured at 25, 40, 55 and 70 degrees C for comparison with the calculated pH values. Of the 108 predictions made, 96 were of pH values with +/- 0.1 pH unit of the measured values, at temperatures ranging from 25 degrees C to 70 degrees C and at ionic strengths ranging from 0.1 M to 0.5 M. These programs will be useful for identifying appropriate buffer solutions at various temperatures and/or ionic strengths.