Modified electrode voltammetric sensors for trace metals in environmental samples

Abstract

Eletrodos de filmes finos de mercúrio modificados com Náfion foram investigados para análise de traços de metais em amostras ambientais de águas e efluentes, pela combinação das técnicas de análise por injeção de fluxo descontínuo e de voltamentria de onda quadrada com redissolução anódica. O método, envolvendo injeção de cerca de 50 microlitros de amostras sem tratamento prévio sobre o eletrodo detector, apresenta resposta rápida. O bloqueio e o envenenamento do eletrodo são mínimos, como mostram os estudos com componentes tensoativos. Foi realizada uma comparação entre substratos de carbono vítreo e de rede de microeletrodos de fibra de carbono, com este último apresentando um pequeno aumento de sensibilidade. Como aplicação foram analisadas amostras de água de rio e de efluentes industriais, coletadas e digeridas em meio ácido para a determinação de íons zinco, cádmio, chumbo e cobre. Nafion -modified mercury thin film electrodes have been investigated for the analysis of trace metals in environmental samples of waters and effluent by batch injection analysis with square wave anodic stripping voltammetry. The method, involving injection over the detector electrode of untreated samples of volume of the order of 50 microlitres has fast response, blocking and fouling of the electrode is minimum as shown by studies with surface-active components. Comparison is made between glassy carbon substrate electrodes and carbon fibre microelectrode array substrates, the latter leading to a small sensitivity enhancement. Application to analysis of river water and industrial effluent for labile zinc, cadmium, lead and copper ions is demonstrated in collected samples and after acid digestion.

Influence of Nafion Coatings and Surfactant on the Stripping Voltammetry of Heavy Metals at Bismuth-Film Modified Carbon Film Electrodes

“…Comparing these responses with those of the bismuth electrodes without the polymer film, in Figures 1 and 2, it can be seen that even in the absence of Triton, the peak currents are lower with the Nafion-covered electrodes, by 75% for Zn but by only 4% for Cd and Pb, the decrease in signal being due to diffusion limitations imposed by Nafion. This contrasts with a decrease of 15% at the mercury thin film electrode [34]. The Zn signal decreased so much probably due to a small amount of hydrogen evolution during deposition at the Nafion-coated Bi film as was also observed with in situ deposited Bi films at these potentials.…”

“…Often these films are made from polymers, and the one most used for trace metal ion analysis is the cation exchange polymer Nafion. The Nafion coating is easy to prepare, and the antifouling effect is significant [34].…”

Batch Injection Analysis: An Almost Unexplored Powerful Tool

“…In the subsequent studies, the electrodeposition of thin mercury films inside polymeric films of Nafion [55, 56, 59 ± 61], poly(ester sulfonic acid) [57], poly(vinyl sulfonic acid) alone and associated to different polymers [58] was optimized. Some of these studies involved the quantification of heavy metals in effluents and wastewater samples [55,58,59].…”

UV-Assisted Digestion of Petrochemical Industry Effluents Prior to the Determination of Zn, Cd, Pb and Cu by Differential Pulse Anodic Stripping Voltammetry

“…11 Wet acid digestion are commonly used method for breakdown of dissolved organic matter prior to the application of the voltammetry. 19,20 However, when these digestion methods are performed, the use of high levels of chemical oxidants can be necessary, introducing contamination to the samples. Normally, these digestions are time consuming and performed under aggressive conditions, requiring the use of heating.…”