The analysis for total arsenic is no longer sufficient to describe this contaminant in aquatic environments. Arsenic can undergo extensive chemical and biochemical transformations in an aquatic system. Since each of the resulting arsenic compounds differ in their toxicity to humans, it is important to follow these transformations. Examining the transformations under various chemical and physical conditions will aid in predicting the ultimate fate of the arsenicals in a given aquatic environment. In order to follow the transformations, it is first necessary to identify and quantitate them. It is important that the speciation procedures should be simple and adaptable to analyzing many samples.