Automated determination of total phosphorus in aqueous samples

The determination of total phosphorus in an automated microbatch analyzer system is described. The procedure combines persulfate digestion of the sample and colorimetric detection of orthophosphate by the ascorbic acid reduction of phosphomolybdate in a single processing chamber. Approximately 9 min are required per sample; approximately 1.7 ml of sample and 0.17 ml of total reagent are consumed. The limit of detection is < or =10 microg/1. phosphorus. The method is tolerant of variations in salinity of the sample. Good agreements with ASTM procedures are shown for a variety of test compounds, lake water, wastewater and urine samples.