Critical review perspective: elemental speciation analysis methods in environmental chemistry - moving towards methodological integration

We review the application of speciation analysis used in environmental chemistry studies to gain information about the molecular diversity of elements in various environmental compartments. The review focuses on three major analytical methodologies: electrochemical, X-ray absorption spectroscopy, and methods that couple chromatography with mass spectrometric detection. In particular, the review aims to highlight the advantages and disadvantages of the three methods, and to demonstrate that both the chemistry of the element and the nature of the environmental compartment determine the choice of the preferred analytical technique. We demonstrate that these two factors can lead to technique-dependent shortcomings that contribute to the current gaps in knowledge of elemental speciation in the environment. In order to fill those gaps, multi-method approaches are urgently needed. Finally, we present a selection of recent studies that exhibit the potential to use complementary techniques to overcome method-dependent limitations in order to reduce ambiguities and to gain more confidence in the assignment of the molecular structure of elements in environmental samples.