Trace Iron Determination by Cyclic and Multiple Square-Wave Voltammetry at Nafion Coated Electrodes. Applicationto Pore-Water Analysis

Abstract

Nafion coated glassy carbon electrodes (NCE) are employed for preconcentrating and detecting Fe2+ and Fe3+ 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: Fe3++e⇋Fe2+. 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.

Titanium carbide nanoparticles/ion-exchange polymer-based sensor for catalytic stripping determination of trace iron in coastal waters

“…In order to solve these problems, great efforts have been taken to develop mercury-free solid electrodes. For example, solid-state gold-amalgamation [14], ion-selective membranes [15], ionomercoatings [16][17][18][19], carbon paste [20], glassy carbon [21] electrodes and gold microelectrode ensembles [22] as new solid electrodes have been developed for iron determination. However, the continuous improvements of functional electrodes are still urgently required for achieving simple, rapid and sensitive detection of trace iron, especially in coastal waters.…”

“…Nafion as one of the most widely used cation-exchange polymer possesses the ideal electrochemical properties as well as the high chemical and mechanical stability. In previous reports, Nafion has shown benefits in facilitating the preconcentration of Fe 3+ , Fe 2+ and iron complexes [16][17][18][19]. Except for the selectivity, the acceleration of electron transfer rate is also an important aspect to be considered.…”

Utilização de técnicas eletroanalíticas na determinação de pesticidas em alimentos

“…Uma técnica que tem sido aplicada nos últimos anos é a múlti-pla voltametria de onda quadrada [95][96][97] , que possibilita a determinação de traços e ultra-traços de espécies orgânicas e inorgânicas, correspondendo a limites de detecção na ordem de 1 ng L -1 (1 ppt) podendo, assim, ser aplicada com sucesso na detecção de pesticidas em alimentos e bebidas 98 . Recentemente, moléculas de DNA têm sido incorporadas à superfícies eletródicas para detecção de bactérias 99 , vírus 100 , monitoramento genético de doenças, monitoramento ambiental NR = não relatado; HMDE = eletrodo de gota pendente de mercúrio; DME = eletrodo gotejante de mercúrio; UME = ultramicroeletrodo Utilização de Técnicas Eletroanalíticas Vol.…”

Electrochemical technique to measure Fe(II) and Fe(III) concentrations simultaneously

“…As one of the most common metal ions, iron ions play an important role in dominating many biogeochemical cycles which determine the trace element availability in the environmental system [1]. In addition, different oxidation states of iron ions play different roles.…”

“…An electrochemical technique to quantify iron ions was proposed by Ugo et al [1,15]. They described a method which applies cyclic and multiple square-wave voltammetry (CMSWV) techniques on a nafion coated electrode (NCE) to track iron species.…”