DETERMINATION OF PHOSPHORUS IN AQUEOUS-SOLUTION VIA FORMATION OF THE PHOSPHOANTIMONYLMOLYBDENUM BLUE COMPLEX - REEXAMINATION OF OPTIMUM CONDITIONS FOR THE ANALYSIS OF PHOSPHATE

This paper describes an investigation of the conditions affecting the determination of phosphate using the reduced phosphoantimonylmolybdic acid method. The aim was to develop a determination method with faster kinetics than the original procedure of Murphy and Riley, for automat ion using how-injection analysis. Optimum colour formation was found t o occur at [H+]/[MoO42-] ratios between 50-80 at all pH values tested (0.36-1.06). The maximum rate of formation occurs at a [H+]/[MoO42-] r atio of 70 within a pH range of 0.57-0.88 when an antimony concentrati on greater than 0.06 mM and ascorbic acid concentration greater than 0 .009 M in the final solution are used. Full colour development occurs within 0.8-1 min. The ascorbic acid reagent was found to be stable for 30 days. The results of the study indicated that by suitable selectio n of reagent conditions, rapid chromophore development can be achieved .