Introduction

Monitoring the bioavailability, toxicity and risk relationships arising from trace element contaminants in ecosystems requires the determination of the their concentrations in soil, water, microorganisms, plants and animals. Therefore, the appropriate analytical method(s) for addressing the particular question(s) of interest need to be chosen from among the broad array of analytical methods that are available. In the first part of this chapter, we will deliberately focus on the presentation and use of X-ray-fluorescence (XRF)-based methods for the analysis of "bulk" biological samples, such as standard and total-reflection energy-dispersive XRF (EDXRF, TXRF). Although EDXRF and TXRF are far less popular methods for analyses of element concentrations in biological samples than, for example, atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic-emission spectroscopy (ICP-AES), there is still no particular reason why they cannot be used for this purpose. From the viewpoints of economics and environmental protection, EDXRF

Department of Biology, University of Ljubljana, Vecna pot 111, 1000, Ljubljana, Slovenia e-mail: [email protected] e-mail: [email protected] e-mail: [email protected]

Jozef Stefan Institute, Jamova 39, 1000, Ljubljana, Slovenia e-mail: [email protected]

e-mail: [email protected]

e-mail: [email protected]

I. Arcon

University of Nova Gorica, Vipavska 13, P.O. Box 301, 5001, Nova Gorica, Slovenia e-mail: [email protected]

B. Povh

Max-Planck-Institut fur Kernphysik, P.O. Box 103980, 69029, Heidelberg, Germany e-mail: [email protected]

I. Sherameti and A. Varma (eds.), Soil Heavy Metals, Soil Biology, Vol 19, DOI 10.1007/978-3-642-02436-8_6, © Springer-Verlag Berlin Heidelberg 2010

and TXRF are generally much cheaper and environmentally friendlier than the other popular methods mentioned. They also have the further advantage that a whole suite of different elements can be determined simultaneously (Necemer et al. 2008), which is especially important for the analysis of unknown samples with unknown element concentrations. When samples are analyzed, for example, with AAS, the concentration range of the measured element must be predicted, so that the samples with high element concentrations can be appropriately diluted to bring them into the range of the reference standard curve applied. Additionally, XRF spectrometry allows the analysis of biologically important elements like phosphorus, sulfur and chlorine, which cannot be analyzed by AAS or ICP-AES.

Since the presence of elevated trace element concentrations in the environment usually raises questions about the ways that organisms interact and deal with them, the second and third parts of the chapter will be dedicated to the more specialized and highly sophisticated X-ray fluorescence/absorption-based methods. Micro-proton-induced X-ray emission (micro-PIXE) using accelerated protons is one of the most modern, sensitive, and reliable methods for the localization and quantification of different elements in biological samples at the tissue and cellular levels. On the other hand, X-ray absorption spectroscopy (extended X-ray absorption fine structure or "EXAFS", and X-ray absorption near-edge structure or "XANES") using synchrotron light offers studies of the chemical speciation and coordination of trace elements in biological samples, therefore opening up new dimensions in research into interactions between trace elements and organisms at the organ, tissue and cellular levels.

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