Research Goals: A primary objective of this research group is the development of methods by which to analyze the species of various elements within complex matrices.

Overview: The Analytical Core is primarily responsible for assistance to other scientists in the area of elemental speciation. Elemental speciation is defined as the analyses that lead to determination of the distribution of an element’s particular chemical species in a sample. This may be further associated with oxidation state, organometallic nature or complex form. This field has grown exponentially recently as it has been found that total elemental analyses are not adequate to answer the complex risk/benefit questions that are arising. Different species or forms of a single element are often markedly different in their toxicity. Therefore, knowledge of the total amount of an element may be uninformative and even misleading regarding any positive or negative effects.

The most common approach to accomplish speciation is to couple a separation technique (such as gas or liquid chromatography) to some type of sensitive and selective detection. The inductively coupled plasma mass spectrometer (ICP-MS) is one of the most common chromatographic detectors to which GC and LC separation techniques are interfaced; this detector has shown to be both selective and selective for many elements. Detection limits are in the range of the ppt for most of the elements of the periodic table. Additionally, the plasma produces mainly single-charged ions that can be identified according to their isotopic abundance. Finally, ICP-MS is almost simultaneous and it can be used to monitor 12-15 isotopes in transient signals coming from chromatographic systems.

Sample preparation is a crucial step in elemental speciation analyses as it is imperative to preserve the nature of the species. Digestion methods commonly employed for total element determinations are not adequate as they most probably will induce a change in the original species. Therefore, milder procedures are required and, in some cases, concentration techniques may be necessary due to the low levels of some elemental species.

Progress to Date: Our group has developed a method for the analysis of several arsenic species, As(III), As(V), MMAA and DMAA. Anion exchange chromatography was coupled to ICP-MS and a mobile phase containing 2mM NaH2PO4 and 0.2 mM EDTA at pH 6 allowed adequate separation of four As species in less than 10 minutes. [J.A. Day, M. Montes-Bayón, A.P. Vonderheide and J. A. Caruso, "Evaluation of a Rough Method for the Analysis of Arsenic Species in Drinking Water Samples by LC-ICP-MS", Analytical and Bioanalytical Chemistry, 2002, 373, 664-668.]

Application of Knowledge: Analysis of specific elements in complex matrices. This may be in support of the research of other groups or may be used in regulatory measures.