Speciation of Dissolved Trace Nickel in Environmental Waters by On-Line Sonodigestion-Flow Injection Solid Phase Extraction Coupled to Flame Atomic Absorption Spectrometry

M C Yebra-Biurrun,J M Castro-Romero

doi:10.4236/ajac.2011.22013

M C Yebra-Biurrun, J M Castro-Romero

Open Access

https://doi.org/10.4236/ajac.2011.22013

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Abstract

A simple on-line sonodigestion system was successfully used for breakdown organic nickel complexes in environmental waters acidified with diluted nitric acid prior to flow injection total dissolved nickel preconcentration in a microcolumn containing a chelating resin (Chelite Che with iminodiacetic acid groups) and determination by flame atomic absorption spectrometry. For the determination of the dissolved labile nickel fraction, microcolumns packed with the chelating resin were loaded in-situ with the sample without sample pH modification, and once in the laboratory were inserted in the flow injection device where nickel elution-detection was carried out. The performance of the chelating resin was investigated in order to elucidate its behavior in the presence of dissolved nickel species. The results obtained reveal that the resin, at the experimental employed conditions, retained only dissolved free nickel ions and nickel bound to weak complexes (labile fraction). The figures of merit for determinations in both nickel fractions are given and the obtained values are discussed. The speciation scheme is applied to the analysis of nickel in river and seawater samples collected in Galicia (Northwest, Spain). The results of fractionation showed that Ni are mainly in the dissolved labile fraction in river water, while in seawater samples analyzed was mainly present in the organic fraction.

Highlights

Nickel is a transition metal element that is widespread in the natural environment, and fulfils an important role in many biochemical processes
A simple on-line sonodigestion system was successfully used for breakdown organic nickel complexes in environmental waters acidified with diluted nitric acid prior to flow injection total dissolved nickel preconcentration in a microcolumn containing a chelating resin (Chelite Che with iminodiacetic acid groups) and determination by flame atomic absorption spectrometry
ethylenediaminetetraacetic acid (EDTA) is an organic ligand present in environmental waters, which is frequently used as organic ligand model because has high affinity for metals, with which forms strong complexes [29]

Summary

Introduction

Nickel is a transition metal element that is widespread in the natural environment, and fulfils an important role in many biochemical processes. Once dissolved in fresh or sea water, the form of aqueous nickel is influenced by pH, redox conditions, ionic strength, the type and concentration of inorganic and organic ligands, pressure and temperature, and the surfaces available for adsorption [1,2]. The dissolved nickel fraction in fresh and sea water forms free hydrated Ni(II) cations and soluble nickel inorganic and organic complexes of different stability [3]. An important group of complexing agents in natural waters, which forms very stable complexes with transition metals, is called the dissolved organic matter (DOM) [4]. Humic and fulvic substances, which are made up of a complex mixture of residues from the decomposition of plants and animals, are the main components of DOM in the aquatic environment, consisting of 30% - 80% dissolved organic carbon in waters.

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