Metal Logarithmic Scale Titration as a Tool for Complexing Ligand Distribution Determination : an Application by DPASV

• Published in: Environmental technology Vol. 25; no. 5; pp. 589 - 599
• Main Authors: Garnier, C., Mounier, S., Benaïm, J. Y.
• Format: Journal Article
• Language: English; French
• Published: London Taylor & Francis Group 01.05.2004; Selper; Taylor & Francis: STM, Behavioural Science and Public Health Titles
• Subjects: Analytical chemistry; Applied sciences; CADMIUM; Cadmium - analysis; Cadmium - chemistry; Chemical Sciences; Continental interfaces, environment; Continental surface waters; DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY; Earth Sciences; Electrochemistry; Environment and Society; Environmental Sciences; Exact sciences and technology; Geochemistry; Global Changes; Hydrogen-Ion Concentration; LEAD; Lead - analysis; Lead - chemistry; Ligands; LOGARITHMIC SCALE TITRATIONS; Models, Statistical; Natural water pollution; Ocean, Atmosphere; Organic Chemicals; ORGANIC LIGANDS; Pollution; Rivers; Sciences of the Universe; Titrimetry; Water Pollutants - analysis; Water treatment and pollution; Complexation; Organic matter; Pollutant behavior; Ligand; Anodic stripping voltammetry; Stability constant; Modeling; Optimization; Concentration measurement; Trace element; Surface water; Lead; pH; Stream; Speciation; DIFFERENTIAL PULSE ANODIC STRIPPING VOLTAMMETRY; ORGANIC LIGANDS; CADMIUM; LOGARITHMIC SCALE TITRATIONS; LEAD
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2004.9619349

A new logarithmic scale titration is proposed for the characterisation of natural organic matter-trace metals interactions in natural systems. The Suwannee River Fulvic Acid complexation with Cd and Pb ions has been analysed by this technique, using Differential Pulse Anodic Stripping Voltammetry (DPASV) for labile metal concentrations measurement. Results of titrations have been modelled by four ligands. Their complexing properties (C Li , K i Cd , K i Pb ) have been determined by a non-linear optimisation based on the speciation program MINEQL, coupled with a simplex. These ligands were called "very weak, weak, strong and very strong" with respect to their complexing constants (K i Cd , K i Pb ) ranging from 10 4 to 10 11 . The obtained ligands concentrations (C Li ) are respectively 1.9 μM, 150 nM, 25.1 nM and 21.1 nM for a 7.9 ppm carbon content. Moreover, this model takes account of the pH dependency and metals competition respectively by experiments at pH 7.8 and 4.6, and by definition of stability constants for each ligand toward each analysed metal. As a conclusion, the authors suggest a systematic use of the logarithmic scale titrations when full characterisation of the metal-organic matter interactions is necessary.