The complexation features of xylenol orange with Bi(III) and its spectrophotometric determination in pharmaceuticals

Abstract

The complexation features of Bi(III) with xylenol orange (XO) have been studied. It was found that three complexes of different stoichiometry have been formed in the studied system. The complex composition of Bi(III) : XO = 1 : 1 (λ = 540 nm, ε = 17000, log β = 10.5) has been formed at pH = 1.0 in reagent excess, and its dimerization with the formation of the complex stoichiometry 2 : 2 (λ = 560 nm, ε = 24000, log β = 17.8) has been observed in excess of Bi (III). The complex composition of Bi(III) : XO = 1 : 2 has been formed with weak light absorbing properties (λ = 500 nm, ε = 9000, log β = 9.9) at pH = 6.8. The complexation mechanism of Bi(III) with XO has been proposed based on the totality of the spectrophotometric data and its theoretical interpretations. In the acidic environment (pH = 1.0) the coordinating ion is Bi 3+ and coordinated ligand is an ionized by sulfo-groups reagent form. At pH = 6.8, the ion chelator is BiOH 2+ , and XO reacts in ionized by sulfo and carboxyl groups form. The effect of extraneous ions on the absorbance value of the complex Bi (III) with a XO at pH = 1.0 was studied. The complex with molar ratio 1 : 1 is recommended as an analytical form. Beer’s law holds in the Bi(III) concentrations range 0.4-10.0 μ g/cm 3 . The detection limit is 0.12 μ g/cm 3 and the limit of quantification is 0.37 μ g/cm 3 . The simple method of spectrophotometric determination of Bi(III) with xylenol orange in pharmaceuticals has been developed. Keywords : spectrophotometric analysis, complexation, xylenol orange, bismuth (III), pharmaceuticals (Russian) DOI: http://dx.doi.org/10.15826/analitika.2016.20.3.007 A.N. Chebotarev, D.V. Snigur , V.P. Dubovyiy Odessa I.I. Mechnikov National University ul. Dvorianskaya, 2, Odessa, Ukraine , 65082