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Chromium is a naturally occurring metal found in small quantities associated with other metals, particularly iron. It is commonly used for making steel and other alloys, bricks in furnaces, dyes and pigments, chrome plating, leather tanning, and wood preserving. Due to its extensive use in industrial processes, large quantities of chromium compounds are discharged into the environment. Although chromium can exist in all oxidation states from 0 to VI, Cr(III) and Cr(VI) are the most prevalent. Even though Cr(III) is an essential nutrient, Cr(VI) is a known mutagen and carcinogen and is more soluble and therefore, more mobile than Cr(III).

There is a need for lower detection limits because public awareness of hexavalent chromium has increased recently and the US National Water Quality Criteria for Cr(VI) in freshwaters is set at 11 ppb (µg/L). More regulations on Cr(VI) are expected in the future. In addition, for better risk assessment, treatment, and remediation studies, an accurate trace value can be more valuable than a nondetect from a method that only has a detection limit in the sub-ppm range (EPA Method 7196A). Accurate determination of Cr(VI) at ng/L levels is a major challenge because the existing methods are neither not selective or not sensitive enough. For instance, the colorimetric determination of Cr(VI) is prone to interferences from molybdenum and vanadium. Anion chromatography is used in EPA Method 7199 (1636) to separate Cr(VI) from the matrix. In that method, Cr(VI) is determined spectrophotometrically after a post column reaction with diphenylcarbazide. Even though most of the problems mentioned above are avoided with this technique, there are still problems when permanganate is present in the samples.