Rapid spectrophotometric determination of total phosphorus in industrial wastewaters by flow injection analysis including a capillary digestor

The method described is suitable for the rapid determination of total phosphorus in industrial wastewaters. A coiled teflon capillary digestor (10 m long, 1 mm i.d.), which contains a platinum wire as catlyst for oxidation with potassium peroxodisulfate at 160°C, is directly connected to the color-development system based on ion-pair formation between molybdophosphate and malachite green. A single determination of total phosphorus can be completed in 4 min. Calibration graphs are linear for ranges of 0–500 and 10–50 ng ml^-1 phosphorus. The determination limit is 2 ng ml^-1 phosphorus when the sample injection volume is optimized for a given analyte concentration. Applications to seawaters and industrial wastewaters mixed with seawater are discussed. Results are in good agreement with those obtained by the standard method.