Trace elements species

It is evident that huge errors may occur during aU these consecutive steps. The only way to validate the methodology is to have at hand suitable RMs certified for the trace element species content in the relevant matrix, together with suitable cali-brants. Few of these are yet commercially available. 

It is clear that the available RMs certified for trace element species are not sufficient to cover present needs. As it is quite unlikely that producers of CRMs will ever be able to meet all demands, users are encouraged to produce their own RMs to guar-... 

The list of elements and their species listed above is not exhaustive. It is limited to the relatively simple compounds that have been determined by an important number of laboratories specializing in speciation analysis. Considering the economic importance of the results, time has come to invest in adequate CRMs. There is a steadily increasing interest in trace element species in food and in the gastrointestinal tract where the chemical form is the determinant factor for their bioavailability (Crews 1998). In clinical chemistry the relevance of trace elements will only be fully elucidated when the species and transformation of species in the living system have been measured (ComeUs 1996 Cornelis et al. 1998). Ultimately there will be a need for adequate RMs certified for the trace element species bound to large molecules, such as proteins. 

Fingerova H, Koplik R (1999) Study of minerals and trace element species in soybean flour. Fresenius J Anal Chem 363 545-549. 

The principal advantage of the ion microprobe (as opposed to the Auger microprobe) is the ability to obtain depth profiles for trace elemental species present in the analytical volume. The characterization of coal fly ash clearly illustrates this point (11-14). Auger detection limits are comparable to BSCA, and thus only elements with bulk concentrations greater than 1% by weight in fly ash (Si, Al, Fe, Ca, S, Na, K) can be... 

Environmental Monitoring of Selected Elements, Group Elements and Trace Element Species... 

Few trace element species can be analysed in natural samples directly. Ion selective electrodes (ISE) allow measurements of metal ion activity (Cu2+, Cd2+) however, their use in the marine environment is limited due to low sensitivity and interference by Cl-. 

Development of chemical speciation schemes which can be directly related to measures of bioavailability - This would allow the determination of which active trace element species merit the most intensive research from the standpoint of environmental perturbation. Some studies have attempted to correlate metal fractions determined by a particular technique (operationally defined speciation) with those that are bioavailable (functionally defined speciation) (Larsen and Svensmark, 1991 Buckley, 1994 Deaver and Rodgers, 1996). However, any correlation is only empirical and more research is required to achieve an understanding of the mechanisms involved in bioavailability and to develop rational predictive models. 

Gercken, B. and Barnes, R.M. (1991) Determination of lead and other trace element species in blood by size exclusion chromatography and inductively coupled plasma/mass spectrometry. Anal. Chem., 63, 283-287. 

Specialists in speciation analytics are interested in various chemical species and the physical forms that certain elements assume. Here are some examples of the physicochemical forms of trace element species in water bodies ... 

Gonzalez, E.B., Sanz-Medel, A. Liquid chromatographic techniques for trace element speci-ation analysis. In Caruso, J.A., Sutton, K.L., Ackley, K.L. (eds.) Elemental Speciation New Approaches for Trace Element Analysis, pp. 81-121. Elsevier Science B.V, Amsterdam (2000)... 

Sorbed trace element species may range from simple cations to complex polynuclear hydroxides formed by hydrolysis and condensation in solution or... 

The concentration of free metal species in soil solution is controlled by several factors, the most significant of which are thermody-namic/kinetic parameters. Mathematical approaches to modeling soil solution -solid-phase equilibria - are broadly described in numerous publications (Lindsay 1979, Sposito etal. 1984, Waite 1991, Wolt 1994, Sparks 1995, Suarez 1999), and several models for calculating activity coefficients for trace metals are overviewed and discussed. Waite (1991) concluded that mathematical modeling clearly has a place in extending the information that can be obtained on trace element species distributed by other methods and will be of practical use in systems for which determination of concentrations of all species of interest is impossible because of sensitivity constrains or other analytical difficulties . 

The preliminary study reported here is part of an investigation of the abundances and nature of trace-element species in crude oils. Neutron activation... 

Weiss, C. S., The Detection of Trace Element Species in Solvent Refined Coal", Ph.D. Dissertation, Washington State University, 1980. 

In aquatic sediments or soils, there are also a range of trace elements species ranging from ions exchanged to particles, to those bound to organic matter or in various inorganic forms (e.g., oxides, carbonates, sulfides) or as more inert crystalline mineral phases. As in waters, speciation studies in soils and sediments are generally undertaken to better understand the bioavailability of toxic substances and to investigate transport pathways to and from other parts of the ecosystem. Sediment and soil pore waters (soil solutions) are of particular interest because they are in equilibrium with the solid phase and are the medium for contaminant uptake by plants and many other biota. The techniques used for speciation analysis in these aqueous samples differ little from those for waters. 

A recently defined and new objective has been trace element speciation, which provides information about the physical/chemical state of the trace elements. Species separated by chemical methods are subsequently determined by instrumental or radiochemical activation analysis. 

Gercken B, Barnes RM (1991) Determination of lead and other trace element species... 

Hall, G. E. M. (1998) Analytical perspective on trace element species of interest in exploration. J. Geochem. Explor., 61(1-3), 1-19. 

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