Spectrophotometric determination of traces of phosphorus by an extraction method

A general method is presented for the spectrophotometric determination of phosphorus at trace levels. It involves extraction of the yellow molybdophosphoric acid with isobutyl acetate and subsequent reduction to heteropoly blue. The method covers the range 0.2–20 μg of phosphorus. A comprehensive study of interferences using standard additions of 10 and 20 μg of phosphorus was carried out and modifications are described to permit the determination of phosphorus in a wide variety of metals and salts.