Automation of a flow-injection system for multispeciation

Introduction Differentiating between the two most frequent oxidation states of chromium is fundamental in speciation studies of this element on account of the toxicity of hexavalent chromium. In fact, most of the works on this element published so far deal solely with this aspect [1]. Flow-injection analysis (FIA) has been used several times for determining this element in one [2 and 3] or in its two most common oxidation states [4-10]. Nevertheless, it is known that there is a large variety of chemical forms of Cr(III) and Cr(VI), which show different properties depending on the groups or elements to which they are bound. Their relative abundance is a function of the type of medium. Since the pH is a major parameter in any type of solution (especially in aqueous ones) and taking into account that its value dictates the predominance of a particular species of Cr(III) and Cr(VI) (hydroxylated, dimer etc.), the following species of chromium must be considered to be present in waters.