Elimination of sulfate interferences in the Chromatographic determination of o-phosphate using liquid-liquid extraction

A liquid–liquid extraction procedure for the elimination of high levels of sulfate is described. The proposed method allows the ion-chromatographic determination of ppb concentrations of phosphate in the presence of a 20000-fold excess of sulfate. The liquid anion exchange resin Amberlite LA-2 was selected to retain sulfate from the sample solution acidified by acetic acid as well as cation-exchange cartridges in the H-form. The detection limit for phosphate was 0.03 mg/L.