title: Phosphate determination in seawater: toward an autonomous electrochemical method.
abstract: Initial steps to create an autonomous in situ electrochemical sensor for orthophosphate determination in seawater are presented. First, the optimal conditions to form the molybdophosphate complex in artificial seawater medium were determined by addition of sulphuric acid and sodium molybdate to the solution containing orthophosphate. Secondly, the anodic oxidation of molybdenum to form molybdate ions and protons was used to create the molybdophosphate complex without addition of any liquid reagents. The molybdophosphate complex is detectable by amperometry with an average precision of 2.2% for the concentration range found in the open ocean and the detection limit is 0.12 μM. Three solutions are proposed to address the silicate interferences issue and one of these methods is used for the natural samples collected in the coastal waters offshore Peru during the Pelagico 1011-12-BIC OLAYA cruise in November-December 2010. Results showed a good precision with an average of 2.5% and a reasonable deviation of the amperometric analysis as compared with colorimetric measurements (4.9%).
authors.affiliation: Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, UMR 5566, 18 Avenue Edouard Belin, 31401 Toulouse Cedex 9, France. justyna.jonca@legos.obs-mip.fr
authors.forename: Justyna
authors.initials: J
authors.lastname: Jońca
authors.forename: Violeta
authors.initials: V
authors.lastname: León Fernández
authors.forename: Danièle
authors.initials: D
authors.lastname: Thouron
authors.forename: Aurélien
authors.initials: A
authors.lastname: Paulmier
authors.forename: Michelle
authors.initials: M
authors.lastname: Graco
authors.forename: Véronique
authors.initials: V
authors.lastname: Garçon
mesh_terms: D055664:Electrochemical Techniques / Q000379:methods*; D008982:Molybdenum / Q000737:chemistry; D010084:Oxidation-Reduction; D010710:Phosphates / Q000032:analysis*; D012623:Seawater / Q000737:chemistry*; D012680:Sensitivity and Specificity
chemical_list: D010710:Phosphates; C044659:molybdate; D008982:Molybdenum