Determination of Chromium(VI) by Two-channel Flow Injection Analysis System Using Dilute Acetone-based Diphenylcarbazide Solution

概要

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Many spectrophotometric methods by flow-injection analysis (FIA) have been reported, which are based on the reaction of chromium(VI) with diphenylcarbazide. In those methods, organic solvents, such as acetone, ethanol, 1-propanol, are used to dissolve diphenylcarbazide, so that the reagent solution contained organic solvent in high or less concentration. However, it is preferable to reduce the amount of organic solvent flowing into the system, especially in cases using a peristaltic pump. In this study, FIA with the reagent solution containing acetone less than the conventional methods was examined using a compact manifold, which consists of an all-in-one peristaltic pump, injector, thermostat and photometric detector. The absorbance was measured at 540 nm. The reagent conditions and the FIA parameters were examined for optimization; the reagent solution (H2SO4 0.36 mol L−1-diphenylcarbazide 0.5 g L−1-5 v/v% acetone) and carrier (water) were both flowed at a flow rate of 0.425 mL min−1, the reactor was maintained at 40°C, and a 200 μL sample was injected. Under these conditions, the calibration curve was linear from 0.005 to 5 mg L−1 (R2: 0.9998) of chromium(VI) and the relative standard deviation was 3% (n = 5) at the 0.005 mg L−1 level. Good results were obtained in recovery tests using sample solutions from soil leaching and content tests according to the Japanese environmental quality standards for soil pollution.