POTENTIOMETRIC DETECTORS FOR THE DETERMINATION OF ACIDITY BY DISCONTINUOUS FLOW-ANALYSIS

Three potentiometric detectors, each incorporating a vibrating reed mixer, were investigated for use in the determination of acidity by discontinuous flow analysis (DFA). Two of these used PVC and glass membrane pH-sensors, and the third employed a novel differential titration technique based on two quinhydrone electrodes. These detectors were applied to the determination of the total acidity of vinegars and the titratable acidity of wines, the results agreeing well with standard procedures. The analysis of wine proved to be difficult because of the gradual change in pH at the end-point and so a method was developed which determined the titratable acidity at pH 8.3.