Speciation methodologies

Table 8.80 shows the present status of speciation methodology. For trace-metal speciation, atomic absorption detectors feature a relatively high absolute detection limit (10 pg level), as compared to the 0.1 to 1 pg sensitivity level for molecular ion MS techniques as well as for MIP-AES. The detection limit of LEI-ToFMS is in the attogram range. Speciation has been reviewed [550]. Various monographs deal with speciation analysis [542,551,552]. 

As speciation methodology has developed over the past 40 years, it has become clear that quality control issues such as sampling, sample preparation, and calibration are critical to obtain meaningful results regarding environmental samples. Many early studies were flawed by errors in these methodologies that produced inaccurate data. Here some of the major issues in sample handing and treatment are discussed. 

METHODOLOGICAL APPROACHES TO THE INVESTIGATION OF THE METAL SPECIATION IN THE NATURAL WATER... 

Templeton D, Ariese F, Coenelis R, Danielsson LG, Muntau H, van Leeuwen H, and Lobinski R (2000) lUPAC guidelines for terms related to speciation of trace elements Definitions, structural aspects and methodological approaches. Analyst, in preparation. 

R. Cornells, J. C., Crews, H., and Heumann, K. Handbook of Speciation Technique and Methodology, John Wiley Sons, Inc., New York (2003). 

De Cremer, K., in Handbook of Elemental Speciation Techniques and Methodology, Vol. I, R. Cornelis,... 

Olivas, R. M. and Camera, C., in Handbook of Elemental Speciation Techniques and Methodology, Vol I, R. Cornelis, J. Caruso, H. Crews and K. Heumann (eds.). John Wiley Sons, Chichester (2003) 73. 

In the last few years, we have seen the application of isotope dilution methodologies to some new analytical fields. One of these is elemental speciation , where the aim is to determine individual chemical species in which an element is distributed in a given sample. IDMS has also proved its usefulness in element speciation, in which either species-specific or species-unspecific spikes can be used. For example, species-specific IDMS is nowadays used in several laboratories as an effective tool to validate analytical procedures for speciation and to investigate and document eventual interconversion between species. In addition, the study of induced variations in the isotopic composition of a target element can also provide insight into various (bio)chemical and physical processes isotopic analysis is, therefore, also of increasing importance in biological studies. 

Although the topic of speciation is now a major focus of research and application it is not a new one. To give but one example, soil scientists have, for many decades, carried out a type of speciation in which specific selective reagents have been used to extract from soil that portion of an element known from field experiments to correlate with plant availability. A host of methodological approaches to speciation is now available and this edition attempts to provide an up-to-date documentation of the state-of-the-art as we enter the new millennium. 

This second edition retains the structure of the first edition. It aims to provide a comprehensive review of the current science of speciation, covering relevant methodological, analytical and modelling aspects as well as giving an overview of recent work on speciation in various spheres. It is divided into two parts, the first dealing with the more methodological aspects and the second with specific compartments of the environment, with the speciation of radionuclides, and presents a review of current trends and developments. 

In each chapter of Part II, the current state-of-the-art of speciation in the subject area is discussed, important examples and particular methodological aspects are presented, and the needs for further development or research are indicated. A final chapter gives an overview of trends and recent developments in speciation science. 

Templeton, D.M., Ariese, E, Cornelis, R., Danielsson, L.-G., Muntau, H., Leeuwen, H.P. van, Lobinski, R., IUPAC (2000) Guidelines for terms related to chemical speciation and fractionation of elements. Definitions, structural aspects and methodological approaches. (IUPAC Recommendations 2000.) PureAppl. Chem. 72, 1453-1470. 

The existence of an element in different chemical forms in the gaseous, solid or aqueous solution phase provides the conceptual basis for speciation in soils. More particularly, a chemical species in soil refers either to a specific molecular arrangement of the atoms of an element or, quite often, to the result of an operational process of detection and quantitation aimed at elucidating chemical forms (Bernhard et at., 1986, pp. 7-14). In principle, the former definition should be the outcome of the latter, methodological definition. In practice, this connection is difficult to achieve in natural systems (Bernhard et al., 1986) (see Chapter 1 for a definition of speciation). Understanding speciation is important in assessing the availability of plant nutrients, plant uptake of potentially toxic elements (e.g. Al, Cd), and the movement of both nutrient and toxic substances into waterways or other parts of an ecosystem (Da Silva et al., 1991). 

Classical speciation of radionuclides is described in Chapter 13. Methodology for single and sequential extraction of soil to assess radionuclide availability to plants is similar to that used for heavy metals, and has recently been reviewed (Kennedy et al., 1997). Therefore, only recent applications of sequential extraction to speci-ate both natural and anthropogenic nuclides are discussed below. 

The various strategies and methodologies for element speciation are discussed in depth in the first part of this book, Techniques for Speciation . This chapter deals with current trends and recent developments in techniques and with recent examples of their application in different compartments of the environment. It also presents recent studies on the speciation of a group of biologically important elements. 

El Moll, A., Heimburger, R., Lagarde, F., Leroy, M.J.F. and Maier, E. (1996) Arsenic speciation in marine organisms from the analytical methodology to the constitution of reference materials. Fresenius J. Anal. Chem., 354, 550-556. 

As before, the book is broadly divided into two parts, the first dealing with methodology, including the use of quality control, and the second outlining speciation in various compartments of the environment. The final chapter summarises recent developments and trends. 

In conclusion traceability concepts as they are now defined are of little practical use. On the other hand, methods of analysis such as these are certainly needed in science and society and so are RMs and methods. Work must go on in the absence of a full uncertainty budget and lack of clarity concerning the traceability reference [9], The BCR was right to develop a number of CRMs for speciation analysis as a diagnostic aid in the further development of this particular methodology. 

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