865 SOLUBLE PHOSPHOROUS IN WATER
PO4-P
Quantitative determination by ascorbic acid reduction of phosphomolybdate complex and quantitative measurement by flow injection analysis.
Summary: This method quantitatively determines the amount of PO4-P in water. Orthophosphate concentration in water is determined spectrophotometrically by reacting with ammonium molybdate and antimony potassium tartrate under acidic conditions to form a complex. This complex is reduced with ascorbic acid to form a blue complex which absorbs light at 880 nm. The absorbance is proportional to the concentration of phosphorus in the sample. Samples are analyzed using an automated Flow Injection Analyzer (Lachat). The method has a detection limit of 0.05 mg/L. The analysis requires approximately 2 mL of sample but 10 mL is requested to allow for quality control samples.
Method 4500-P G (Flow Injection Analysis for Orthophosphate) in Standard Methods for the Examination of Water and Wastewater, 20th Edition. Clesceri, L. S.; Greenberg, A. E.; and Eaton, A. D.; eds. American Public Health Association; Washington DC; 1998. pp. 4-149 - 4-150.