Chemical speciation studies are essential to an understanding of toxicity and bioavailability of the element in the environment. Although total element concentration has been traditionally used to assess environmental impact and health risk of the element, it is now established that no meaningful interpretation can be made without speciation information. Each chemical form of an element has a different toxicity. For example, the toxicity of arsenic to animals varies from the more toxic arsenite, to the moderately toxic methylated arsenicals, to the essentially non-toxic arsenobetaine. We are interested in chemical speciation studies of metalloids (such as arsenic, antimony, and selenium) and heavy metals (such as mercury, lead, and cadmium) in the environment and biological systems, in view of their important impact on the environment and potential health risk.