SOLVENT-EXTRACTION SPECTROPHOTOMETRIC DETERMINATION OF BERBERINE AND BENZETHONIUM IN DRUGS WITH TETRABROMOPHENOLPHTHALEIN ETHYL-ESTER BY BATCHWISE AND FLOW-INJECTION METHODS

A spectrophotometric method for the determination of berberine and benzethonium in drugs was studied using batchwise and flow injection techniques coupled with solvent extraction. Tetrabromophenolphthalein ethyl ester (TBPE.H) in 1,2-dichloroethane reacted with berberine and/or benzethonium to form a blue ion associate whose absorbance was determined at 610 nm. The extraction conditions were studied using a batchwise method. On the basis of the results obtained with the batchwise method, a three-line manifold was constructed. The sample was injected into a distilled water stream and the pH adjusted to 11 with a borate-phosphate buffer solution. Then the stream was mixed with the extracting TBPE.H reagent. The organic phase was separated with a polytetrafluoroethylene porous membrane (0.8-mu-m pore size). The sample throughputs were 45 h-1 for berberine and 30 h-1 for benzethonium. The calibration graphs were linear in the range 1 x 10(-6)-1 x 10(-5) mol dm-3 for berberine and/or benzethonium and the relative standard deviation (n = 6) was 0.9% for 1 x 10(-6) mol dm-3 berberine and 1.2% for 4 x 10(-6) mol dm-3 benzethonium. The proposed method was used for the rapid and selective determination of berberine and benzethonium in pharmaceuticals.