| For its excellent properties, the chemicals contain chromium have been widely used in many fields. In nature, chromium commonly exists in two oxidation states: chromium(III) and chromium(VI). Chromium(III) has long been recognized as an essential element for life. However, chromium(VI) is highly carcinogenic and has sever damage to human and other lives. There are numerous regulations on permissible limits of chromium(VI) in water and wastewater and industry products. Spectrophotometry, atomic absorption spectrometry and other analytical methods are applied in determination of chromium(VI).In this paper, a new method, Automatic Reference reverse Flow Colorimetry was introduced. And the application in leather analysis was also advanced.Firstly, three flow injection systems were compared and the Automatic Reference reverse Flow injection system was recognized the most fit for analysis of chromium(VI). Through tests, the conditions for analysis of chromium(VI) was chose : 0.5 mmol/L 1,5-diphenylcarbazide dissolved in 0.4 mol/L H2SO4, the flow rate of reaction solution was 2.5 ml/min, the length of reactor was 3m, and the volume of sample injection valve was 235.5ul. The method was also evaluated under this condition. The calibration graph was linear in the range of 1 x10-6-1580x 10-6g/L and the detection limit was 0.46x10-6g/L .The conditions of applying the Automatic Reference reverse Flow>Colorimetry in leather analysis was also discussed. Leather sample was extracted in 0.1 mol/L Na2HPO4 solution (pH8.0) for 3h with temperature of 25C , to avoid the oxidation of chromium(III), protection with nitrogen was suggested. The extracted samples was then bleached by flowing through DJ-4 resin.With its high sensitive, resistance to interference, easy to operate and other excellence, the Automatic Reference reverse Flow Colorimetry could be used for determination of chromium(VI) in water, wastewater, leather and other samples.
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