In Situ Metal Speciation Using a New Technique

2016

Up to now, different approaches have been proposed for in situ trace metal speciation, based on the deployment of in situ devices such as Donnan Membrane device (DMT) and then analysis by ICP-MS [1], or by means of preconcentration systems hyphenated wih electrochemical detection such as gel integrated microelectrode (GIME) probe [2] or a direct in situ electrochemical stripping speciation method such as Absence Gradient Nernstian Equilibrium Stripping (AGNES) [3]. Although numerous in situ methods have been proposed, currently there is no reliable in situ probe for trace metal speciation at concentration levels present in natural systems. Regarding autonomy problems of in situ probes, electrochemical devices have the advantage of being easily available in smaller sizes and with the possibility to be operated with batteries. This work presents the probe ISIDORE developped for in situ trace metal speciation [4]. This probe is based on the hyphenation between a DMT and a screen-printe...

Talanta, 2016

In this work we propose a trace metal speciation methodology to determine the total, free and ultrafiltered (o1 KDa) metal fractions using electrochemical methods (SCP and AGNES) and tangential ultrafiltration (UF) experiments that can easily be carried out on-site. We tested our methodology spiking Cadmium ions into two natural waters samples from Itapanhau and Sorocabinha rivers in Sao Paulo State, Brazil. The limits of detection (LOD) was 1.6 Â 10 À 9 M for the total Cd 2 þ determination performed by Stripping Chronopotentiometry (SCP) in the source and acidified ultrafiltered solution and 1.9 Â 10 À 9 M for the free Cd 2 þ determination using Absence of gradients and Nernstian equilibrium stripping (AGNES), using a thin mercury film electrode. The total metal determination was performed by SCP in acidified samples and the results compared with graphite furnace atomic absorption spectroscopy (GF-AAS). The SCP results were adequate with a 96% of recovery from the known metal spike for the 12 samples tested. For the Itapanhau sample the free metal determined by AGNES and the ultrafiltered fraction are identical, while for the Sorocabinha the free metal in the source is significantly smaller than the ultrafiltered fraction, indicating that this sample must be rich in metal complexes with small inorganic ligands that are able to permeate the 1 kDa membrane. The proposed metal speciation methodology validated in the laboratory combining UF and SCP/AGNES is able to be used in on-site experiments providing valid information regarding the total and free metal concentrations and additionally some insight on the role of small inorganic ligands to the metal complexation.

Analytica Chimica Acta, 1992

The use of kmetics of metal ion transfer from naturally occurrmg colloidal hgand systems to complexes with spectrophotometncally favourable hgands as a means of study of speciation of metal ions m natural systems IS described The systems have a species dlstnbution which IS determined by the conditions of sample "eqmhbratlon", but kinetic analysis is conducted under condltlons (pH, ionic strength) defined by the reagent solutron The resulting species dlstrtbution is that of the eqmhbratmn condmon with relative lability characterized Apphcatlon of the approach to complexes of simple metal ions, Cuzc and Ni*+, with humlc collolds and hydrous fernc oxides and to ternary systems of iron (U) or alum~mum(III) with humlcs and OH-are revIewed The latter studies have been extended to application to natural waters The conditions for extension of the study of simpler systems to actual natural samples are considered A method based on laser thermal lensmg IS proposed

Talanta, 1986

The analytical potential of a closed flow-injection system with multidetection by a single detector (for calculation of rate constants, reaction rate, dilution and amplification methods, etc.) is extended to simultaneous determinations for chromium speciation, with injection of the reagent(s) into the sample solution (which acts as the carrier).

Current Opinion in Electrochemistry

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ELECTROPHORESIS, 2005

Metal ions are essential for human beings at low concentrations but they are toxic or even carcinogenic at high concentrations. Many metallic ions are found in the environment in different species which are differentiated not only by their physicochemical forms but also by their diverse toxicities with respect to living organisms (speciation). CE has been used for metal ion speciation. The present review article describes the recent trends in metal ion speciation by CE. This article deals with the speciation of metal ions, optimization of the speciation (by independent and dependent variables), hyphenation of CE, validation of the methods, mechanisms of speciation, CE versus chromatography and conclusions.

Analytical Chemistry, 2005

Ecotoxicology and Environmental Safety, 2003

This paper gives definitions related to element speciation and the reasons for the need for speciation. The problems focused on, involve sampling, sample preparation and storage, as well as changes in species information that occur during the use of various separation technologies. However, the potential and advantages of the separation methods in element speciation are also discussed. In addition, problems arising during element detection that are attributable to analytes or mobile-phase composition are outlined, as well as the pronounced advantages of detection by inductively coupled plasma-mass spectrometry (ICP-MS). The combination of the various separation systems with element-or molecule-specific detectors creates problems especially in element speciation. These difficulties are described along with recent developments for overcoming them or for improving their coupling efficiency. Finally, several elements for which the issue of speciation is important are discussed, with examples from some recent publications on arsenic, selenium and iodine speciation.

International Journal of Environmental Research and Public Health

Speciation analysis is a key aspect of modern analytical chemistry, as the toxicity, environmental mobility, and bioavailability of elemental analytes are known to depend strongly on an element’s chemical species. Henceforth, great efforts have been made in recent years to develop methods that allow not only the determination of elements as a whole, but also each of its separate species. Environmental analytical chemistry has not ignored this trend, and this review aims to summarize the latest methods and techniques developed with this purpose. From the perspective of each relevant element and highlighting the importance of their speciation analysis, different sample treatment methods are introduced and described, with the spotlight on the use of modern nanomaterials and novel solvents in solid phase and liquid-liquid microextractions. In addition, an in-depth discussion of instrumental techniques aimed both at the separation and quantification of metal and metalloid species is pres...

2005

The inability to determine metal species in soils hampers efforts to understand the mobility, bioavailability, and fate of contaminant metals in environmental systems, to assess health risks posed by them, and to develop methods to remediate metal contaminated sites. Fortunately, great strides have been made in the development of methods of species characterization and in their application to the analysis of particulates and mixtures of solid phases in physics, analytical chemistry, and materials science. This manuscript highlights a selection of the analytical methods available today offering the greatest promise, briefly describes the fundamental processes involved, examines their limitations, points to how they have been used in the environmental and geochemical literature, and offers some suggested research directions in the hope of stimulating further investigation into the application of these powerful tools to the problems outlined above.