An Improved Ion-exchanger Colorimetry for the Determination of a Trace Amount of Phosphate

Abstract A highly sensitive and selective method has been developed for the determination of a trace amount of phosphate. It is based on the concentration of phosphate as the familiar molybdenum blue complex on the coagulated material prepared from finely divided anion and cation exchangers, collection of the mixed resin on a filter paper, and the subsequent measurement of the absorbance of the complex on the resulting thin layer of resin phase. The calibration curve shows a good proportionality in the concentration range of 1 to 6 μg P1−1. The absorbance corresponding to 1 μg P1−1 is 0.095. The method is successfully applied to the determination of phosphate in a tap water and a river water.