ヨウ化物イオンとクリスタルバイオレットを用いる銅の吸光光度定量

A method for spectrophotometric determination of micro amounts of copper with iodide ion and Crystal Violet (CV) was developed. The method is based on the formation of triiodide ion by the oxidative reaction of iodide ion with copper(II) in dilute sulfuric acid solution and the extraction of triiodide ion into toluene as an ion association complex with CV. The main extracted species is expected to be an ion association complex, CV(+)I(-)(3) copper(II) acts as a catalyst. The recommended procedure is as follows. Take a sample solution containing copper(II) up to 1.6 μg into a 25-ml stoppered test tube. Add 1 ml of 0.46 M sodium iodide solution, 1 ml of 0.5 M sulfuric acid solution and 1 ml of 3.2×10(-4)M CV solution, and dilute the solution to 10 ml with distilled water. Shake the mixture with 5 ml of toluene for 8 min. After the phase separation, measure the absorbance of the organic phase at 607 nm against the reagent blank. The calibration graph shows linearity up to 2.5×10(-6) M of copper(II) in the aqueous phase, and the apparent molar absorptivity is 1.7×10(5)1 mol(-1) cm(-1). Small amounts of oxidizing and reducing agents such as Fe(III), Cr(III) and Co(II) interfered with the determination. The present method is very simple and has a high sensitivity.