SOLID PHASE SPECTROPHOTOMETRIC DETERMINATION OF SELENIUM(IV) USING DITHISONE IMMOBILIZED IN A POLYMETHACRYLATE MATRIX
This paper presents a solid-phase spectrophotometric method for the determination selenium(IV). The proposed method is based on the reaction between the selenium(IV) and dithizone immobilized into transparent polymethacrylate matrix in strongly acidic solution. It was shown that the interaction of selenium(IV) with dithizone in solid phase was accompanied by the formation of the complex with an absorption maximum 420 nm. The change of absorption at wavelength 610 nm corresponding to absorption of excess dithizone remaining after the reaction into polymethacrylate matrix was chosen as an analytical signal. The study of dithizone content into polymethacrylate matrix on the analytical characteristics of the proposed method showed the sensitivity of the selenium(IV) determination increases with its contents. Values of range of determined concentrations are 0.1…0.5 mg/L with the limit of detection 0.09 mg/L where the time of the contact of the sample solution with the polymethacrylate matrix is 60 min. The proposed method was successfully applied to the determination of selenium(IV) in pharmaceutical multivitamin and mineral formulations. Statistical analysis of the results confirms the precision and accuracy of the proposed method. The relative error of determination does not exceed ±8%. The developed method is ecological, cost-effective and involves easily accessible instrumentation technique which can be used by ordinary research laboratories.