Direct and replacement ion chromatography with potentiometric detection using a silver/silver bromide electrode

Abstract

The use of Ag/AgX electrodes as potentiometric detectors in modern ion chromatography methods is re-examined. Contrary to previous reports, in both flow-injection and chromatographic experiments the Ag/AgBr electrode is shown to exhibit the greatest sensitivity to the widest range of anions tested. For direct detection in non-suppressed ion chromatography systems, use of the Ag/AgBr electrode permits the measurement of separated anions at levels lower than those obtainable by the conventional conductivity method. The Ag/AgBr electrode is further shown to be useful as a sensitive detector in replacement ion chromatography. In this case, all anions separated in a suppressed system are quantitatively replaced by bromide before the effluent passes through the electrochemical detector. Cation measurements can also be made by monitoring the exchange of bromide for co-eluting counter hydroxide ions following the replacement stage of the system.