Quantitative determination of Hexavalent chromium using a microtiter plate: Analytical performance, operational efficiency, and fixation of a colorimetric reagent in the plate wells

Efficient and sensitive trace determination of Cr(VI) in small sample volumes is an important issue for environmental protection and the sustainable development of industries. A microtiter plate and a microplate reader have been applied to the colorimetric determination of Cr(VI) using 1,5-diphenylcarbazide (DPC) as indicator, to realize an efficient method with low detection limits. The DPC reagent was fixed on the plate well and the time for color development was significantly reduced (<1 min) compared to conventional methods by using small volume reaction vessel which made it possible to perform determinations of Cr(VI) in a short period of time. The lower limit of quantification of 0.021 mg/L obtained with this method is better than that of the microplate method reported previously, and is comparable to general analytical methods with large sample volumes. In addition, when the chromogenic reagent is fixed to the plate with a water-soluble polymer, the lower limit of quantitation is the same as that of the unfixed reagent. This results in improved instrument portability and more efficient analytical operations.