Development of a modified Britton-Robinson buffer with improved linearity in the alkaline pH region

Britton-Robinson buffer is a multi-buffer system that consists of citric acid, phosphate, barbital, and boric acid. Although this buffer system is known to be effective from pH 2.6 to 12, the linearity of the alkaline region (pH 9?12) is poor. Searching for a weak acid additive to maintain the buffering capacity in the alkaline region, we found that glycine (pKa = 2.35 and 9.78) was effective in improving the linearity of the pH titration curve. The pH titration formula of the improved Britton-Robinson buffer is provided in this report. The pH-dependent activities of renin, a key enzyme that regulates blood pressure and electrolyte balance, were investigated using the improved buffer, and the results found were similar to those measured with the typical Britton-Robinson buffer.