D.T Gjerde and H.C. Mehra

The term chemical speciation is the identification and determination of the individual amounts of the various chemical forms of an element. 

Several elements such as As and Se are converted to diflferent species during weathering, uptake by biota, elimination from biota, fixation in sediments, or remobilization. In order for an analysis to be successful the metal species must be stable throughout the entire analysis. 

Handling of the sample may result in changes in the amounts or types of species. The chromatography or sample preparation may change the sample. This may prevent the accurate measurement of some metal species. In fact, the literature maybe slanted toward those species that are relatively easy to do. For example, there are several papers in the literature on the separation of Fe(II) and Fe(III), but there are very few reports on the separation of V(IV) and V(V). Thus, there are many opportunities for future work. 

There are several reasons for performing speciation. Of course there are the academic studies of various types of trace metals and their conversion and equilibria of various forms. Industrial speciation is important. The effectiveness of chromium plating baths depends on the amounts of Cr(III) and Cr(VI) that are present. Gold plating processes involve the use of Au(I) and Au(III) cyanide complexes. Vanadium speciation is important in the recovery of sulfur from geothermal water. 

But environmental applications appear to be of greatest current interest. Speciation is important because each inorganic species of a particular element may possess quite different biological, medicinal and toxicological properties. There are differences of element-specific species in physicochemical reactivity, biological availability and element trans- 

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