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Trace Iron Determination by Cyclic and Multiple Square‐Wave Voltammetry at Nafion Coated Electrodes. Applicationto Pore‐Water Analysis
Author(s) -
Ugo P.,
Moretto L. M.,
Rudello D.,
Birriel E.,
Chevalet J.
Publication year - 2001
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/1521-4109(200105)13:8/9<661::aid-elan661>3.0.co;2-n
Subject(s) - nafion , redox , voltammetry , cyclic voltammetry , analytical chemistry (journal) , electrolyte , chemistry , aqueous solution , supporting electrolyte , electrode , ion exchange , inorganic chemistry , detection limit , electrochemistry , ion , chromatography , organic chemistry
Nafion coated glassy carbon electrodes (NCE) are employed for preconcentrating and detecting Fe 2+ and Fe 3+ cations from aqueous solutions. The influence of the supporting electrolyte composition and of the redox state on the analyte partitioning within the Nafion coating are examined. By using cyclic voltammetry, the ion‐exchange voltammetric determination of iron in the μM concentration range is achieved from voltammetric peak currents relevant to the reversible redox process: Fe 3+ +e⇋Fe 2+ . Depending on the starting potential of the voltammetric scan, all the iron is initially converted to the Fe(III) or Fe(II) redox state, so that, from the voltammogram, the overall concentration of iron is always obtained. However, the simple measurement of the open circuit potential at the NCE before starting the scan allows one to get information on the ratio between Fe(III) and Fe(II) incorporated in the Nafion coating. From relevant ion‐exchange distribution coefficients, open circuit potential values can be related to the Fe(III)/Fe(II) concentration ratio in the sample. The use at the NCE of a new electroanalytical technique named multiple square‐wave voltammetry in the double differential mode allows the significative lowering of detection limits pushing the operative range of the method in the nM range. Application to analysis of Fe(II) in the pore‐waters of sediments of the lagoon of Venice (Italy) is presented.