Coulometric acid-base titration in nanoliter samples with glass and antimony electrodes.

A modification of the coulometric acid-base titration method is described for the measurement of titratable acid and ammonium in nanoliter samples. The main components consist of a pH-seeking device and a miniaturized antimony electrode system capable of delivering OH- ions at a known rate. The modifications include use of a cup-shaped pH-sensitive glass-membrane electrode for monitoring pH changes during titration and a new electronic titration circuit consisting of a high-impedance differential electrometer, a constant-current source, and an electronic integrating circuit. Details regarding the construction of the components of the titration system and practical aspects of its use are also provided.