Speciation analysis definition

In both cases the species, forms or phases are defined (a) functionally, (b) operationally, or (c) as specific chemical compounds or oxidation states. This usage is employed in this book but IUPAC has proposed a useful clarification in that definition (1) above is abandoned in favour of speciation analysis and the term spe-ciation is reserved for the concept of a description of the distribution of species. 

Trace element speciation analysis is a base for the description of forms and compounds in which they occur in soils. Other definitions are also used to define properties of trace elements in soils. In fact, the general term availability has been recently defined as geoavailability, geochemical availability, biogeochemical availability and bioavailability (Wolt 1994, Smith and Huyck 1999) ... 

Chapter 2 discusses several aspects of speciation analysis, e.g. definitions, existing regulations and sources of errors likely to occur at various steps of the analytical procedures. It is followed by Chapter 3 describing general principles of improvement schemes (organizational aspects) and basic requirements to be followed for the certification of reference materials. 

Results can only be accurate and comparable worldwide if they are traceable. By definition, traceability of a measurement is achieved by an unbroken chain of calibrations connecting the measurement process to the fundamental units. In the vast majority of chemical analyses, the chain is broken because in the treatment the sample is physically destroyed by dissolutions, calcinations, etc. With respect to speciation analysis, the chain is even more complex since it involves successive analytical steps. To approach full traceability it is necessary to demonstrate that no loss or contamination has occurred in the course of the sample treatment. 

Speciation analysis of an element is usually defined as the determination of the concentrations of the individual physico-chemical forms of the element in a sample that together constitute its total concentration. The International Union for Pure and Applied Chemistry (lUPAC) has recently recommended the definition of speciation as the distribution of an element amongst defined chemical species in a system. lUPAC defines chemical species as the specific forms of an element defined as to isotopic composition, electronic or oxidative state, and/or complex or molecular stmcture. 

The definition of metallome and metallomics should be seen in the context of speciation of an element (as mentioned above which was defined by lUPAC as the distribution of an element amongst defined chemical species in a system), but distinguished by consideration of the global role of all metals/metalloids in a system. In speciation analysis, analytical activities of identifying and/or measuring the quantities of one or more individual chemical species in a sample, narrowed to metallobiomolecules, can be referred to as metallomics. In other words, metallomics can be considered as a subset (referring to cellular biochemistry) of speciation analysis understood as the identification and/or quantification of elemental species. 

The lUPAC (International Union for Pure and Applied Chemistry) recommends the following definitions for the terms chemical species , speciation analysis and speciation ... 

Although carbon has long been recognized as an important constituent of ambient aerosols, the analysis of carbon in its many molecular forms has presented formidable obstacles. An approach taken by many investigators (1-12) has been to separate aerosol carbon into organic, elemental, and carbonate classes. However, at the present time only carbonate carbon has an unequivocal analytical definition. Speciation between organic and elemental car-... 

The guiding principles for the selection or development of speciation procedures are similar to those recommended for other forms of chemical analysis. For example, the initial step should be careful definition of the problem, including listing of the analytical specifications (e.g. type of analysis, concentration range, potential sources of error). This step can be followed by selection of a suitable measurement procedure, nomination of a selective separation procedure (if required) and organisation of the total protocol. 

The term speciation , according to Bernhard et al. (1986a), encompasses three aspects (1) the actual distribution among molecular level entities in a given matrix, (2) the processes responsible for an observable distribution (species distribution), and (3) the analytical methods used (species analysis). Aspects (1) and (3) are compatible with the definition given by Ure (1990) and presented in Chapter 1. The second aspect, (2) above, is now seldom used in chemistry and... 

The principle of the isotope dilution analysis (IDA) is described in Section 6.4. Due to its advantages as a definitive and accurate analytical method for the determination of element concentration via isotope ratio measurements, IDA is being increasingly applied in mass spectrometry, especially in ICP-MS and LA-ICP-MS as one of the most frequently used techniques. For example, the isotope dilution technique is employed in species analysis in biological systems, " e.g., for the determination of mercury species in tuna material,or in aquatic systems. Further applications of the isotope dilution technique are the determination of selenomethionine in human blood serum by capillary HPLC-ICP (ORC) MS ° or sulfur speciation in gas oil, diesel or heating fuel by LA-ICP-MS. Evans and co-workers have reported on the high accuracy analysis of sulfur in diesel fuel by IDA. ICP-SFMS has been employed for Si species analysis in biological or clinical samples and... 

Both filterable and particulate forms of organic phosphorus are transferred from soils, but the lack of suitable techniques for determining specific phosphorus compounds in aqueous samples means that there is little information available on the chemical composition of either fraction. Conceptual understanding of organic phosphorus forms and their behaviour in water is also limited by the operational definitions that arise from conventional analysis procedures (see below). For detailed reviews of speciation techniques for organic phosphorus in soil waters see McKelvie (Chapter 1, this volume) and Cooper et al. (Chapter 3, this volume). 

It may not be trivial for an analyst to say that the method actually does measure what it purports to. When there are possibilities of speciation, or different isomers, then the analyst must be aware of the client s requirements and ensure that the method is specific for them. For example, analysis for total copper is different from bioavailable copper , and with the latter the definition of bioavailable must be carefully considered. 

Rodriguez-Gonzalez P, Encinar JR, Alonso JIG, and Sanz-Medel A (2003) Isotope dilution analysis as a definitive tool for the speciation of organotin compounds. The Analyst 128 447-452. 

Recently it has been possible to observe a definite trend in elemental analysis, from detection of the total content of a heavy metal in a sample to the detection of its different chemical compounds or oxidation states (speciation). This is because the essentiality or toxicity of the metals should not be attributed to an element itself but to element compounds with distinct biological, physical, and chemical properties. A compact and relatively cheap DL based instrument could be a reasonable alternative to the powerful but expensive ICP-MS, presently used for speciation. The potential of... 

---