Nanoparticles for improved trace metal analysis

During the past decades environmental research and monitoring has received increased interest in order to evaluate possible risks for human health and living organisms. Particular attention has been paid to the determination of elements such as As, Cd, Co, Cr, Hg, Ni, Pb and Sb in environmental, biological and medical samples. Measurement of these trace metals with common multi-element techniques such as inductively coupled plasma atomic emission spectrometry (ICP-AES) or inductively coupled plasma mass spectrometry (ICP-MS) makes exhaustive sample pre-treatment prior to detection mandatory. Among the many techniques available for matrix separation and/or analyte pre-concentration, solid-phase extraction (SPE) is probably the most widely employed. However, although well established is conventional SPE with sorbent columns still related with some inherent limitations (e.g. surface deactivation, irreversible retention of sample constituents, creation of flow resistance, ) affecting accuracy and precision of sample pretreatment. The central aim of the proposed project is to establish a new approach for sample pre-treatment including analysis as an alternative to common SPE-techniques. Within this project for the first time the concept of renewable surfaces (also referred as bead-injection (BI) technique) will be combined with on-bead detection and multi- element ICP analysis. The proposed research covers the following innovative aspects: synthesis and surface functionalization of nanoparticles (with particle diameters ranging from a few nm to some hundred nm) for selective/specific enrichment of trace elements and simultaneous separation of interfering matrix constituents development of a flow cell for on-line trapping of nano-particles with an ultrasonic standing wave, which will be integrated in a fully automated sequential-injection (SI) system to overcome the drawbacks of manually performed batch-mode techniques multi-element measurement of nanoparticles including the retained trace elements will be performed using solid sampling techniques, namely slurry procedures and electro thermal vaporisation (ETV) in combination with ICP-AES/ICP-MS analysis circumventing the elution step allows the use of sorbent materials with functional moieties which bind the metal non-reversible, which broadens the choice of appropriate functional groups for analyte retention and offers therefore improvements in selectivity. The project will be performed at the Vienna University of Technology (Institute of Chemical Technologies and Analytics and the Institute of Material Chemistry) in collaboration with the University of the Balearic Islands (Department of Chemistry) and the University of Venice (Department of Environmental Sciences).

One major task of analytical chemistry is to determine the concentration of chemical elements in samples of environmental, medical, or technological origin. Motivations for such quantitative determinations can be of toxicological nature (e.g., to monitor heavy metals in environmental compartments), or can be found in product optimization (e.g., to track and reduce impurities that have negative effects on a technological product), to name a few. When quantifying elements in such samples, unfortunately, there is a multitude of possible sources of error which can lead to severe over- or under-estimation of the targeted element. There are many mechanisms how such systematic errors influence the result, but most of them originate from the sample matrix, which interferes the final measurement of the target analytes.To overcome such matrix-effects, one very well-established way is to isolate the targeted element from its original surrounding. In other words, the sample is dissolved, and all components that are not the targeted element are chemically separated. So far, there are numerous ways to achieve this goal, but they have in common that they are very time-consuming and require large amounts of chemicals, and are therefore disadvantageous both in economic and ecologic terms.In this project, an alternative method for target element isolation was developed. In short, the sample is dissolved, and small beads are added to the liquid solution. The surface of those beads is covered with chemical anchor-groups that selectively interact with the targeted element. This interaction causes the targeted element to be trapped on the beads surface. Other sample components do not react with the surface-anchors. The beads now contain the element of interest, and in order to obtain quantitative information, it is only necessary to now measure these beads. In this project, we developed different approaches to do so (e.g., by dissolving the beads chemically, or by evaporating them, either by means of conventional heat, or by means of a laser).For the analysis of challenging liquids such as blood or fermentation media, this approach was not applicable, and therefore we developed an alternative approach for measuring such samples using a laser system.Summing up, we have developed methods for fast, straight-forward, and effective isolation of target elements from environmental, biological and technological samples. We applied this methodology to determine heavy metals in urban airborne dust, to quantify rare elements in green tea samples, to determine the heavy-element concentration in human whole-blood, and to quantify phosphorus in biochemical fermentation media.