抽出比色による水中の超微量銅の定量

概要

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A method is presented for the determination of trace amounts of copper (II) in water for high pressure boilers etc. Cadmium diethyldithiocarbamate in chloroform is used as the reagent for extraction of copper (II) from water. The recommended procedure is as follows. Ten ml of buffer solution containing sodium acetate and hydrochloric acid, and 10 ml of 1M citric acid solution are added to 400 ml of sample solution in a 500 ml separatory funnel. Adding 20 ml of cadmium diethyldithiocarbamate chloroform solution, 1 ml of which is equivalent to about 17 μg of copper, the mixture is shaken vigorously for 3 min. After being set aside for 2 min., chloroform phase is separated. The extract is transferred into a 25 ml volumetric flask containing 2 ml of ethanol, and is diluted to the mark with pure chloroform. The absorbance is measured at 435 mμ in a 50 mm cell, using pure chloroform as a reference blank solvent. The interference due to iron (II) is avoided by the addition of citric acid. One ppb of copper can be determined, whereby 95% confidence interval extends from 0.71 ppb to 1.29 ppb at 1 ppb copper (II) concentration. The regression line is given by X=44.420Y+0.045, where Y is the absorbance at copper concentration X.
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