Food for Thought: A Critical Overview of Current Practical and Conceptual Challenges in Trace Element Analysis in Natural Waters

Abstract

Abstract:The practical and conceptual challenges faced by the analysis of trace elements present in natural waters are not merely, as is often thought, an endless race towards lower detection limits or to the development of techniques allowing the determination of any possible chemical species formed by all chemical elements. Rather, as discussed in this paper, they include the development of (i) robust, cheap, and reliable methods that could also be used by laypeople (the experience gained in the development of field kits for As is discussed as an example from which similar developments for other elements may be drawn); (ii) more environmentally-friendly methods (the current guiding criteria probably being too simplistic); and (iii) methods making it possible to follow diel concentration changes and sharp concentration variations caused by the probable increase of heavy rainfall events. This paper also claims that neither the measurement of total concentrations (reliable methods are lacking for many elements of the periodic table of trace elements, as illustrated through the cases of Bi, Te, and Sb), nor chemical speciation analysis, are as mature as often thought. In particular, chemical speciation studies demand the development of a better, comprehensive conceptual framework. A trial is carried out to lay the basis of such a framework.

A review on electrochemical methods for trace metal speciation in environmental media

“…The limits of these models have recently been 38 reviewed [4], highlighting numerous cases where specific fractions of metal complexes 39 can be internalized, either directly or through the dissociation of labile complexes. Thus, 40there is a need to design, develop, apply and interpret analytical techniques able to 41 provide reliable speciation information [5][6][7] that can be used by regulatory bodies. 42Although there are numerous non-electrochemical techniques [5][6][7][8][9][10][11][12][13], those that are 43 provide attractive possibilities such as speed of analysis, low-cost and miniaturization in 44 view to on-site (and in-situ) measurements [14], and can also provide thermodynamic 45 (i.e.…”

“…Thus, 40there is a need to design, develop, apply and interpret analytical techniques able to 41 provide reliable speciation information [5][6][7] that can be used by regulatory bodies. 42Although there are numerous non-electrochemical techniques [5][6][7][8][9][10][11][12][13], those that are 43 provide attractive possibilities such as speed of analysis, low-cost and miniaturization in 44 view to on-site (and in-situ) measurements [14], and can also provide thermodynamic 45 (i.e. equilibrium) information (such as the amount of the free metal, the amount of 46 complexing sites, the stoichiometry of complexes and their stability constants [15]) as 47 [16;17].…”

Environmental chemistry: a discipline standing on two shoulders

“…2) with the measurement of global parameters, such as water complexation capacities and binding constants (column C). [29] Coexistence of two different strategies is also found in other fields, such as in the study of environmental colloids [30] where an approach that tends to emphasise complexity and heterogeneity and attempts to describe colloid behaviour by using global descriptors (power-laws) coexists with a second, reductionist approach that targets selected fractions for detailed analysis of specific features that might be extrapolated back to the bulk pool. Many years ago, Tipping already recognised that drawing the different approaches together was a major, 'perhaps insurmountable', challenge in the field.…”

“…[32] [34] Figure reproduced from Filella. [29] The reader will find a detailed description of the approaches in this reference.…”

Another decade of water quality assessment studies in Tanzania: Status, challenges and future prospects

“…In most cases, sophisticated analytical research instruments and methods with very low detection limits are needed in order to detect most micro-contaminants in environmental samples. In recent decades, some robust and reliable methods that allow multiple analyses of samples have replaced the rudimentary, labour-intensive and time-consuming methods (Filella, 2013). Modern methods for measuring trace amounts of contaminants in the water are based on application of analytical techniques such as gas chromatography-mass spectrometry (GC-MS), highperformance liquid chromatography (HPLC), inductively coupled plasma-mass spectrometry (ICP-MS), ion chromatography (IC) and advanced liquid chromatography-tandem mass spectrometry (LC-MS 2 ), hydride generation atomic absorption spectrometry (HG-AAS) among others.…”