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.
This paper reports the analytical potential of 4-(2-quinolylazo)phenol (p-QAP), a new heterocyclic azo dye, as a sensitive chromogenic reagent in the spectrophotoinetric determination of silver(1). The silver(1) -(p-QAP) complex has also been used in the micro-determination of iodide ions. The principle involved is the ligand exchange reaction and the difference in absorbance between the silver(1) -(9-QAP) complex before and after the addition of iodide ions and the reagent blank is proportional to the concentration of iodide ions. The method is simple, rapid and the precision is high compared with some of the (other published methods.lJ Experimental Apparatus the spectra.
Reaction behavior of 4-(2-quinolylazo)phenol (p-QAP) is established with three noble metals, i.e. palladium(II), osmium(VIII), and gold(III), under various conditions. Palladium(II) forms a 1:1 greenish violet complex at pH 8–10 (absorption maximum at 580 nm), while osmium(VIII) forms a 1:1 violet compex at pH 8–9.5 (absorption maximum at 550 nm) with the ethanolic solution of p-QAP. Color reaction with gold(III) with ethanolic solution of p-QAP is instantaneous, but fades away with time. However, a 4:4:2 mixture of water, ethanol, and cyclohexanol stabilizes this color for 45 min. Thus a 1:1 red gold(III) complex formed at pH 8–9.5 absorbs maximum at 550 nm. The Sandell’s sensitivities (ng cm−2) of the color reactions are 2.7, 3.9, and 9.8 with palladium(II), osmium(VIII), and gold(III) respectively. Other physicochemical characteristics of the complexes are established. A number of foreign ions tested for their interferences and use of masking agents wherever necessaty it tabulated. Synthetic solutions identical in composition to some palladium(II) and gold(III) alloys are estimated to ascertain the suitability of the reagent.
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