University of Illinois at Urbana-Champaign. Water Resources Center
Abstract
The objective of this project was to develop a method for the determination of phosphate in natural water which would be an improvement over the presently accepted spectrophotometric technique in terms of detection limit and freedom from interference. Cathodic stripping chronopotentiometry was found to be an analytically sensitive method for phosphate analysis. The technique is based upon the reversible oxidation of a metallic indicator electrode to an insoluble phosphate salt film. When copper is used as the indicator electrode, the detection limit is 10 ppb. Control of the pH at 6.0 and removal of oxygen from the solution eliminates anticipated interferences in natural water samples. The major drawback of the method is that under the electrolysis conditions employed, salt of mixed stoichiometry is deposited which subsequently results in two separate stripping steps. When mercury is the indicator electrode, the system approaches true Nernstian behavior, so a detection limit considerably below 10 ppb is anticipated. However, an observed interference of chloride ion has, to the present, limited application of the electrode to solutions containing phosphate in excess of 50 ppb.U.S. Department of the InteriorU.S. Geological SurveyOpe
