Colorimetric and Atomic Absorption Spectrometric Methods for the Determination of Hyoscine N-Butylbromide in Pharmaceutical Formulations Using Cobalt (II) and Chromium (III) Thiocyanate Complexes

Two simple and sensitive colorimetric and atomic absorption spectrometric procedures have been established for determination of hyoscine N-butylbromide (Hyo.Br) in pure form and in pharmaceutical formulation. The methods are based on formation of an insoluble coloured ion-associate between the examined drug and tetrathiocyanatocobaltate (CoTC) or hexathiocyanatochromate (CrTC). The first method involves extraction of Hyo-CoTC and Hyo-CrTC ion-associates with methylene chloride and isobutyl alcohol, followed by measuring the absorbance at 630 and 557 nm, respectively. Optimization of the extraction conditions is investigated. Beer's law is obeyed in the concentration ranges 144.20-865.20 and 72.00-640.00 μg/ml using CoTC and CrTC, respectively. The molar absorptivities, Ringbom ranges, Sandell sensitivities and quantification and detection limits are also calculated. The second method is based on measuring the absorbance of the excess cobalt or chromium in the aqueous solution, after precipitation of the drug, at 240.7 and 357.9 nm using atomic absorption spectrometer, respectively. Linear application ranges, characteristic concentrations and detection limits of Hyo.Br are 0.404-1.617 mg/ml, 16.11 and 10.78 μg/ml in the case of CoTC, while 0.040-0.283 mg/ml, 29.50 and 2.70 μg/ml in the case of CrTC. The present methods have been successfully applied for the determination of the drug in commercial dosage form. The data obtained by the developed methods are compared with the official one.