Determinatioii of anions with a potentiometric detector for ion chromatography

A potentiometric detector based on an ion-selective electrode (ISE) was constructed and used to determine anions by ion chromatography. The ISEs employed were two types : one is silver-silver halide electrodes (Ag-AgCl, Ag-AgBr, and Ag-AgI) and the other is an epoxy resin matrix electrode using trioctylmethyl-ammonium ion as sensing material. The detectors based on the former electrodes respond specifically to halide and pseudo-halide ions. In case of using CHaCOOH-CHaCOONa solution (2x10-3M, pH 6.4) as eluent, 6 species of anions (Cl-, Br-, I-, SGN-, GN-, and S-) could be detected down to 2x10-6M (100 p,l-injection) with a detector based on an Ag-AgCl electrode. On the other hand, a detector based on the latter electrode could determine more various anions. In particular, the detector was highly sensitive to NO2-, NO3-, CIO4-, I-, and SGN-. The detection limit for these ions was 5x10-5M at 100 jil-injection. The double column chromatography using separation and suppression columns with 5x 10-3 M NaOH solution as eluent was the most efficient system for the detection of anions with a detector based on an epoxy resin matrix electrode. Anions of NO2-, Br-, and NO3- could be detected down to lXlO-6M (100 p,l-injection). The sensitivities of most detectors constructed were kept constant for at least 2 months. The detector can be easily constructed with exchangeable detector assemblies including ISE, which is also prepared with ease. This provides an additional advantage to the detector.