Simultaneous determination of total nitrogen and total phosphorus in water using peroxodisulfate oxidation

A method by which the TN and TP in water samples can be determined simultaneously employing peroxodisulfate oxidation was developed. A solution of 0.074 mol 1−1K2S2O8–0.075 mol 1−1 NaOH was adopted for the oxidizer, which made it possible to carry out alkaline peroxodisulfate oxidation for TN and acid peroxodisulfate oxidation for TP in turn during a single autoclaving. The pH values changed from 12.57 to approx. 2.0 and the period of alkalinity was estimated at 1.42 min at 120°C. The products of oxidation were nitrates and orthophosphates and both were measured simultaneously by an AutoAnalyzer. Good recoveries of both nitrogen and phosphorus compounds were obtained. The method was excellent in terms of its simplicity, speed and efficiency in handling large numbers of samples.