Speciation biological materials

The nomenclature of nickel compounds should be further standardized (WHO 1991). Analytical methods must be developed and standardized in order to facilitate speciation of nickel compounds in atmospheric emissions, biological materials, and in other environmental samples (NAS 1975 WHO 1991). Studies are needed to elucidate the biogeochemical nickel cycle on a global scale and determine its potential for long-range transport (WHO 1991). 

The development of sensitive and rapid analytical schemes for the extraction and separation of inorganic tin and organic tin compounds and their chemical speciation products from water, sediments, and biological materials (WHO 1980 Reuhl and Cranmer 1984 Hall and Pinkney 1985 Laughlin and Linden 1985 Thompson et al. 1985 Blunden and Chapman 1986 USPHS 1992). 

In this article some of the methods and techniques that have been used for the speciation of trace inorganic elements in biological materials, and the approaches used to solve some of the above problems will be discussed. 

A complication in the study of biological materials is that the species of an element which are either formed and/or take part in physiological reactions in different compartments may vary. It is therefore necessary, especially during the sampling and pretreatment steps, that the constituents from different compartments are very carefully separated. For example, in the study of the speciation of an element in blood serum contaminants originating from the erythrocytes could lead to errors in the results. 

Although lEC has been used to separate large molecules most application have been in the fractionation of low molecular mass species. Some of the applications to the study of the speciation of trace elements in biological materials and the necessary pretreatment steps are summarised in Table 2. 

Advances in selenium biochemistry (Arthur, 1994 Heider and Boeck, 1994 Foster and Sumar, 1997 Patching and Gardiner, 1999) and methods for the determination and speciation of the element in biological and environmental samples (Pyrzynska, 1996 D Ullivo, 1997 Thomson, 1998) have been reviewed. In this section, a brief overview of more recent developments in analytical methods and their application to the study of selenium-containing species in biological materials is provided. 

The number of analytical methods developed for the study of the distribution of metal- and metalloid-containing species in the last decade has been impressive. However, a majority of these are as yet to be applied to real biological materials. With the greater appreciation of the pre- and post-sampling factors that influence chemical speciation, and the development of appropriate quality control materials the results of these studies will become more reliable. Consequently, the use of chemical speciation data will become indispensable to accurate environmental impact assessment, and to our understanding of the roles that metals and metalloids play in biological systems. 

Anion-exchange (AE) HPLC-ICP-MS seems to be the most attractive technique for a comprehensive speciation analysis of organo-As species in biological materials. An example chromatogram for such an analysis is shown in Figure 16.4. Cation-exchange HPLC has often been used in parallel to AE-HPLC to conFrm... 

S. Slaets, F. Adams, I. R. Pereiro, R. Lobinski, Optimization of the coupling of multicapillary GC with ICP-MS for mercury speciation analysis in biological materials, J. Anal. Atom. Spectrom., 14 (1999), 851D857. 

Albert, J., Rubio, R., Rauret, G. Arsenic speciation in marine biological materials by LC-UV-HG-ICP/OES. Fresenius J. Anal. Chem. 351, 415 19 (1995)... 

Potin-Gautier, M., Gilon, N., Astruc, M., De Gregori, I., Pinochet, H. Comparison of selenium extraction procedures for its speciation in biological materials. Int. J. Environ. Anal. Chem. 67, 15-25 (1997)... 

Filippelli M. 1987. Determination of trace amounts of organic and inorganic mercury in biological materials by graphite furnace atomic absorption spectrometry and organic mercury speciation by gas chromatography. Anal Chem 59 116-118. 

Element speciation in biological materials is a difficult analytical task. The challenge is to identify and/or quantify very low concentrations of few to several target species (concentration values far below the total element content) in a complex chemical matrix. Additional difficulties include similar physicochemical properties exhibited by the species of one element and their chemical lability. Very often, not all element forms in the sample are known and, finally, the list of certified reference materials (CRMs) for speciation analysis is still limited. " The two most important features of an analytical tool suitable for speciation analysis are excellent selectivity and high sensitivity. Special care should be paid to preserve the natural composition and distribution of species in the sample during the entire procedure. 

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