Detection and Spectrophotometric Determination of Microgram Quantities of Ethylenediaminetetraacetic Acid with Phosphomolybdic Acid

A simple, rapid and accurate method for the detection and determination of microgram quantities of EDTA is based on the absorbance of the complex formed by its reaction with phosphomolybdic acid at pH 2. Absorbance is measured against a phosphomolybdic acid reference solution at a wave length of 690 am. The effect of time, temperature and amount of phosphomolybdic acid is studied and optimum operating conditions established. Beer's law is obeyed in the concentration range 18.6–186.0 μg ml−1 of EDTA. Its detection limit is 18.6 μg in the solution phase and 3.72 μg in the resin phase. The relative standard deviation is ±0.445 μg. Ion exchange resin beads act as a catalyst and detection medium to improve the sensitivity and selectivity of the test.