Comparing Different Approaches for Assembling Selective Electrodes for Heavy Metals

Abstract

Different approaches for increasing the sensitivity and selectivity of voltammetric probes for heavy metals have been examined. These have involved adsorbed monolayers of host molecules, functionalized self‐assembled monolayers and thin polymeric films. Two systems are presented that focus on the selective analysis of Hg(II) and Fe(II). The electrode for Hg(II) is based on a macrocyclic ligand, i.e., Kryptofix‐222, while that for Fe(II) relies on the selective complexation by ferroin ligands, such as 1,10‐phenanthroline. The monomeric and polymeric approaches were examined and compared for both systems. The principal aim of this manuscript is to highlight the ability of fine‐tuning the selectivity characteristics of the solid‐liquid interface as a result of considering and optimizing analyte‐interface interactions. We find that basically, an interface comprising a monolayer, which is capable of forming a strong and selective complex with the analyte, is likely to exhibit sensitivity that is at least as good as a polymeric film. On the other hand, the stability and durability of the latter usually makes it a superior interface for repetitive analysis and will therefore be the preferred choice for flow analysis systems.

Emprego de monocamadas auto-organizadas no desenvolvimento de sensores eletroquímicos

“…Uma das principais vantagens de se utilizar este tipo de superfície para construção de sensores eletroquí-micos, principalmente para determinação de metais pesados, está no considerável aumento na sensibilidade em relação a outros eletrodos, como por exemplo os eletrodos modificados com matrizes poliméricas, possibilitando assim a determinação em amostras reais em níveis de partes por bilhão (ppb) e trilhão (ppt) 51 .…”

“…Um emparelhamento perfeito entre os alcanotióis (geralmente com uma inclinação de 20 a 30 graus em relação à normal da superfície) e o retículo do ouro resulta numa estrutura altamente ordenada (Figura 2) e tem feito deste sistema objeto de um grande número de estudos por meios espectroscópicos, microscópicos e eletroquímicos 12 . Vári-os trabalhos têm sido dedicados ao entendimento da estrutura e do ordenamento das monocamadas, que são caracterizadas pelo alto grau de organização e têm sido empregadas em estudos de transferência de elétrons [34][35][36][37][38][39] , adsorção de proteínas 38,[40][41][42][43] e, principalmente, em vários campos da eletroanalítica 12,[19][20][21][22][44][45][46][47][48][49][50][51][52][53] . A preparação da monocamada possui um papel fundamental no desempenho eletroanalítico do eletrodo modificado.…”

An HMV mapping study of a pulsating jet system

“…Examples of such techniques are stripping voltammetry, pulse voltammetric techniques [2,3] and hydrodynamic modulated systems [4]. In the last of these techniques a particular experimental protocol is developed which results in a periodically altering mass transfer regime.…”

Detection of Heavy Metals Based on Boron-doped Diamond Nanograss Array, Boron-doped Diamond Film and Glassy Carbon Electrodes

“…The glassy carbon (GC) electrode is commonly considered to be the electrode material for anodic stripping voltammetry 3 and numerous applications in trace metal analysis involve the mercury-coated GC electrode 4,5 or polymer-covered GC electrode 6,7 .However, these types of electrodes pose some problems such as the inherent toxicity of the material, the introduction of discouraging environmental legislation 5,[8][9] , film stability 10,11 and preparation and deactivation of the electrode surface 12 .…”