Determination of urinary oxalate using oxalate-selective membrane electrodes

The paper proposes two counter-ions for oxalate-selective liquid membrane construction: [Fe(o-phenanthroline)3]2+ (I) and [Fe(neocuproine)3]2+ (II). Nitrobenzene (NB) was used as solvent. The ion-selective membrane electrodes have a near-Nernstian response over the concentration ranges: 100–0.01 (I) and 100–0.1 (II) μmol/l, respectively. The limit of detection was 1 nmol/l for both membrane electrodes. The working pH ranges are: 2.0–8.0 (I) and 2.0–7.0 (II), respectively. Due to their response characteristics as well as to the results obtained for the recovery tests (relative standard deviation (RSD) <1%), the ion-selective membrane electrodes can be used for urinary oxalate determination.