Cuproine (2,2'-biquinolyl) and its analogues have been used in the spectrophotometric determination of copper( I). The methods, though selective, involve time-consuming extraction procedures. This paper reports the use of 4-(2-quin01ylazo)phenol~ (p-QAP), a heterocyclic azo dye, as a selective and sensitive reagent for copper(1): The reagent forms a greenish yellow complex (Amax. 440 nm) over the pH range 2.94.0 in a medium containing 40% of ethanol. The complex is stable for more than 24 h. Under these conditions there is no interference from other metal ions and copper(1) can be determined selectively. The method has also been used for the selective determination of copper in blood sera and the results compare favourably with those obtained by use of other published method^.^-^ Experimental Apparatus the spectra.A Unicam SP600 spectrophotometer with matched 10-mm glass cells was used for recording A Beckman Expandomatic SS-2 pH meter was used for the pH adjustments.
ReagentsAll chemicals used were of analytical-reagent grade unless specified otherwise. p-QAP solution. p-QAP was prepared by the method of Barua et aZ.l A 1 x l O P 3 ~ solution of the reagent was prepared by dissolving 0.249 g in 1 1 of ethanol. The solution was stable for several days.A stock solution of copper(I1) (2 x lou2 M) was prepared by dissolving an appropriate amount of analytical-reagent grade copper(I1) sulphate pentahydrate in waterCo@er(Ill) solution.
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