Development of Photocatalyst-Based ICP-MS Coupling Techniques for Determination of Trace Elements and Their Species

It is well known that the speciation, or chemical form, of metals governs its fate, toxicity, mobility, and bioavailability in environmental and biological systems. To assess these chemical properties and to accurately gauge their impact on human health and the environment, metals need to be characterized at the atomic level. To attain new information about environmental and biological effects of trace elements, new methodologies or modify conventional analytical methods is deemed as vital factor for the progress of bio- and environmental- studies. In view of the limitation on the analytical capability of single instrumental technique, analytical chemists can seldom rely on a single instrumental technique to analyze a sample with complicated matrix and analyte species with a variety of physico-chemical form. It is thus necessary to develop a technique which can fulfill ultratrace analyses of metal species down to the sub-g/L concentration range in complicated samples.
Accordingly, the most important features of an analytical tool suitable for meeting the requirement of modern bio-analytical works are shorter temporal resolution, good selectivity and high sensitivity. For ultratrace elements measurements, ICP coupled with Mass Spectrometry (ICP-MS) has been considered as first priority option. Although the analytical sensitivity has been significantly improved by the technical advances in ICP-MS, instrumental limitations, such as difficulties in differentiating elemental species and removing matrix interferences caused by the concomitant salt, still remain in advanced analytical technologies. To satisfy the analytical requirements, the potency of hyphenating analytical separation techniques to mass spectrometers has been recognized. Basically, according to Hirschfeld1, the advantages brought about by coupling techniques are increasing the differentiating and separating power of analytical methods and synergism between methods. However, the design of the analytical system is difficult, owing to the complex composition of the real-world sample, the diversity of physicochemical forms of the element, their lability and low concentrations. For overcoming the abovementioned problems, attempts to couple ICP-MS with various types of chromatography for separation, as well as on-line sample pretreatment techniques for signal enhancement and matrix removal have been made. To expand the analytical capability, in this study, we developed several hyphenated systems by integrating the alternative photo-redox characteristic of nano-TiO₂ into the interfacing device to convert both inorganic and organic metal-containing species to gaseous products that are favor for ICP-MS determination. Based on our experimental results, this presentation will describe the studied hyphenated methods which have been proven feasible for the analyses of trace elements and their chemical species in environmental and biological systems.