Speciation analysis chromatographic methods

III. TRACE ANALYSIS ALLOWING SPECIATION A. Chromatographic Methods... 

Ellis, L.A. and Roberts, D.J. (1997) Chromatographic and hyphenated methods for elemental speciation analysis in environmental media./. Chromatogr. A., 774, 3-19. 

The nutritional, chemical, biological, and toxicological properties of a chemical element are known to be critically dependent on the form in which it occurs in food. The recognition of this fact has spurred the development of species-selective (speciation) analytical methods for food additives and contaminants. According to the IUPAC s dehnition, speciation analysis deals with the analytical activities of identification and/or measurement of the quantities of one or more individual chemical species in a given sample [1], The analytical approach is usually based on the combination of a chromatographic separation technique with an element-specif>c detection technique. The former ensures that the analyte compound leaves the column unaccompanied by other species of the analyte element, whereas the latter enables a sensitive and specil>c detection of the target element. Coupled (also called hyphenated) techniques have become a fundamental tool for speciation analysis and have been discussed in many published reviews [2D6]. 

A strong preference in speciation analysis is to use a separation step that can be combined with a detection step in an on-line system [45]. In such coupling, analytical selectivity relies on the application of different chromatographic or electrophoretic methods, while the use of atomic spectrometric techniques assures high sensitivity and f>t-for-purpose limits of detection (LoDs). However, hyphenated techniques with element-specif>c detection do not provide structural information on the species. If appropriate standards are available, the assignation of chromatographic peaks can be accomplished by spiking experiments. On the... 

Liquid chromatography, a seemingly simpler procedure than GC in the speciation analysis of arsenic because it does not require the derivatization stage, also generates a number of potential errors. The selection of chromatographic method involves preliminary evaluation of the solubility of compounds to be separated. The... 

Besides the fractionation of metalloids through SEPs, a series of methods has been proposed for the determination of individual species in the various oxidation states (Gong et al., 2002 Kahakachchi et al., 2004). The most popular detectors for metalloid speciation are inductively coupled plasma-mass spectrometry (ICP-MS) and atomic fluorescence spectrometry (AES), especially after liquid chromatographic separation and hydride formation, which are increasingly replacing atomic absorption spectrometry (AAS). Speciation analysis of pollutants in terrestrial environments is, however, beyond our scope in this chapter. 

In addition, chromatographic separation combined with detection methods, such as neutron activation analysis (NAA) and ICP-MS, was also reported for chemical speciation analysis of iodine in water (Hou et at, 1999b Reifenhauser and Heumann, 1990 Schwehr and Santschi, 2003). In... 

The most commonly used methods for speciation analysis of iodine in tissues and food are chromatographic techniques, such as anion exchange, size exclusion and reverse-phase chromatography, coupled with ICP-MS detection. 

The present work which we believe relates to both quantitation and speciation will (1) extend the number of solvents and chromatographic methods which can be employed using this technique, (2) present metal detection limits in a variety of solvents for both direct aspiration and pumped delivery, (3) discuss trace metal quantitative analysis data obtained on pyridine solutions of several SRC s as a function of processing conditions and coal source and (4) describe the isolation of organically bound metal fractions in a SRC process solvent. 

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