COLUMN-SWITCHING TECHNIQUES IN THE ANALYSIS OF PHOSPHATE BY ION CHROMATOGRAPHY

A comparative study of ion chromatography systems for the analysis of phosphate in samples with high levels of sulphate has been performed. Two low-capacity ion-exchange columns, a high-capacity column and switching systems with direct transfer and with loop transfer have been studied. A high-capacity column permits the determination of phosphate in samples with sulphate-to-phosphate ratio of 5000:10 (mg/l), but at this sulphate level the detection limit for phosphate was relatively high (200 ng). For the column-switching systems, switching time and phosphate detection limits have been studied. A low detection limit (50 ng) was obtained using direct-transfer column switching at sulphate concentrations of 4000 mg/l. A similar detection limit was obtained using a loop-transfer column-switching system with a high-capacity column as a primary column for levels of sulphate of 5000 mg/l. Their applicability for the analysis of water samples is demonstrated.