Flow-injection spectrofluorimetric determination of dissolved inorganic and organic phosphorus in waters using on-line photo-oxidation

The development and application of a continuous flow method for the rapid d etermination of inorganic and organic phosphorus in waters is proposed. The flow-injection (FI) system includes a simple ultraviolet photoreactor for the on-line photodegradation of organophosphorus compounds in the presence of peroxydisulphate, and an external decomposition unit for hydrolysing con densed phosphates with 0.5 mol l(-1) hydrochloric acid. The fluorimetricall y monitored product is thiochrome, which is formed by the oxidation of thia mine by phosphomolybdic acid. The FI configuration designed allows two inje ctions to be performed for each sample; the first, without irradiation, cor responds to inorganic phosphorus and the second, with irradiation, total ph osphorus (inorganic plus organic). Calibration graphs are linear up to 350 ng P ml(-1) and the detection limit is 0.3 ng P ml(-1). The results obtained with this FI system were in good agreement with those obtained by a batch spectrophotometric method [1]. (C) 2001 Elsevier Science B.V. All rights reserved.