Polarographic determination of indium(III) after salting-out extraction of the bromide complex into acetonitrile.
A simple and sensitive method has been developed for the polarographic determination of indium(III) after solvent extraction into acetonitrile, salted-out from aqueous solution with sodium bromide. The extracted indium(III)-bromide complex gives a well-defined d.c. wave with E(1 2 ) = -0.69 V vs. SCE. The wave-height is directly proportional to the concentration of indium(III) from 1.6 x 10(-6) to 3.0 x 10(-4)M with respect to the original aqueous solution. In the a.c. polarographic method, a linear calibration curve is obtained for indium(III) over the concentration range from 1.6 x 10(-6) to 1.5 x 10(-5)M, and interference from most foreign ions can be eliminated. In particular, 10.0 mg of Fe(III) and 2.5 mg of Tl(III) are tolerated when 1.0 g of ascorbic acid is added. The lower limit of determination is 8 x 10(-8)M indium(III) by the square-wave polarographic method.
Nagaosa
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Faculty of Engineering, Fukui University, 3-chome, Bunkyo, Fukui, 910 Japan.