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 swit ching systems with direct transfer and with loop transfer have been st udied. A high-capacity column permits the determination of phosphate i n samples with sulphate-to-phosphate ratio of 5000:10 (mg/l), but at t his sulphate level the detection limit for phosphate was relatively hi gh (200 ng). For the column-switching systems, switching time and phos phate detection limits have been studied. A low detection limit (50 ng ) was obtained using direct-transfer column switching at sulphate conc entrations 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 applicabi lity for the analysis of water samples is demonstrated.