title: Toward an in situ phosphate sensor in seawater using Square Wave Voltammetry.
abstract: A Square Wave Voltammetry electrochemical method is proposed to measure phosphate in seawater as pulse techniques offer a higher sensitivity as compared to classical cyclic voltammetry. Chronoamperometry cannot be either adapted for an in situ sensor since this method requires to have controlled convection which will be impossible in a miniaturised sensor. Tests and validation of Square Wave Voltammetry parameters have been performed using an open cell and for the first time with a small volume (<400µL) laboratory prototypes. Two designs of prototypes have been compared. Using high frequency (f=250Hz) allows to obtain a linear behaviour between 0.1 and 1µmolL(-1) with a very low limit of detection of 0.05 µmolL(-1) after 60min of complexation waiting time. In order to obtain a linear regression for a larger concentration range i.e. 0.25-4µmolL(-1), a lower frequency of 2.5Hz is needed. A limit of detection of 0.1µmolL(-1) is obtained in this case after 30min of complexation waiting time for the peak measured at E=0.12V. Changing the position of the molybdenum electrode for the complexation step and moving the detection into another electrochemical cell allow to decrease the reaction time down to 5min.
authors: Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, UMR 5566, Université de Toulouse, CNRS, CNES, IRD, UPS, 18 Avenue Edouard Belin, Toulouse Cedex 9, 31401 France. Electronic address: carole.barus@legos.obs-mip.fr.
authors: C
authors: C
authors: Barus
authors: Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, UMR 5566, Université de Toulouse, CNRS, CNES, IRD, UPS, 18 Avenue Edouard Belin, Toulouse Cedex 9, 31401 France.
authors: I
authors: I
authors: Romanytsia
authors: Observatoire Midi-Pyrénées, 14 Avenue Edouard Belin, Toulouse Cedex 9, 31401 France.
authors: N
authors: N
authors: Striebig
authors: Laboratoire d'Etudes en Géophysique et Océanographie Spatiales, UMR 5566, Université de Toulouse, CNRS, CNES, IRD, UPS, 18 Avenue Edouard Belin, Toulouse Cedex 9, 31401 France.
authors: V
authors: V
authors: Garçon
keywords: Frequency influence; Phosphate in situ detection; Small volume prototypes validation; Square Wave Voltammetry