DETERMINATION OF PHOSPHATE AND SULPHITE IN NATURAL WATERS IN THE PRESENCE OF HIGH SULPHATE CONCENTRATIONS BY ION CHROMATOGRAPHY UNDER ISOCRATIC CONDITIONS

摘要

Phosphorus in aquatic systems is generally considered the limiting nutrient in most of cases. Its concentration may be below 0.01 mg/l. The sensitivity of the standard method for phosphate with ascorbic acid does not allow its determination in these kind of samples. Ion chromatography (IC) provides a suitable way for phosphate quantification. However, when the sulphate concentrations are significantly high, interference of the phosphate signal does occur, This can be avoided by precipitating sulphate as lead sulphate with lead perchlorate solution performing a potentiometric titration using a lead ion selective electrode (ISE). The samples are then filtered through a 0.45-mu m membrane filter and analyzed by IC.