Direct potentiometry of residual water in acetonitrile using the proton isoconcentration technique

Abstract

Direct potentiometry of the system acetonitrile –0.008–1%m/m water –10^–3 mol dm^–3 perchloric acid in glacial acetic acid, using a glass pH electrode and a calomel reference electrode with saturated lithium chloride in acetic acid as the internal filling solution, shows a systematic and large change in potential with variation in water concentration. This technique allows a fast and accurate determination of trace amounts of water in acetonitrile.