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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 trivalent chromium is an essential nutrient, hexavalent chromium 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 hexavalent chromium in freshwaters is set at 11 ppb (µg/L). More regulations on hexavalent chromium 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 hexavalent chromium 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 hexavalent chromium is prone to interferences from molybdenum and vanadium. Anion chromatography is used in EPA Method 7199 (1636) to separate hexavalent chromium from the matrix. In that method, hexavalent chromium 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.  

Determination of chromium by conventional inductively coupled plasma mass spectrometry alone has various limitations due to the formation of ⁴⁰Ar¹²C+ and ³⁷Cl¹⁶O⁺ in the plasma in the presence of carbon and chlorine. Therefore, samples high in chloride, carbonate, or organic matter usually produce results with positive bias, making accurate quantitation extremely difficult. By employing the DRC technology, most of these interferences are completely eliminated allowing us to achieve sub-ppt detection limits for hexavalent chromium. Spectrophotometric methods described above only use retention times for identification and anything absorbing at the same wavelength can produce a peak. In IC-ICP-DRC-MS technique, on the other hand, chromium is identified using its unique isotopic abundance ratio ( ⁵²Cr/ ⁵³Cr) in addition to retention times. Therefore, false positives or negatives are completely eliminated in this technique .

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