The method is based on the formation of phosphomolybdate with added
molybdate followed by its reduction with sodium sulphide in aqueous sulfuric
acid medium. The system obeys Lambert-Beer’s law at 715 nm in the
concentration range 0.3-12.24 ppm. Molar absorptivity, correlation
coefficient and Sandell’s sensitivity values were found to be 6.1x103 mol-1
cm,-1 0.999 and 0.0156 mg cm-2 respectively. The results obtained were
reproducible with acceptable standard deviation 3.7% and relative error 3.4%.
For a comparison of the method phosphate present in various samples were
also determined separately following an official method. The results of the
developed method compare well with those of the official method.
Keywords: Phosphate, water, detergents, and spectrophotometry.