EXTRACTION-SPECTROPHOTOMETRIC DETERMINATION OF BERBERINE IN CRUDE DRUGS BY THE FORMATION OF A NEW ION ASSOCIATE

A sensitive and selective method based on the formation of ternary complexes of berberine, quinidine and a divalent anion of dibasic acid dyes (A2-) such as Bromophenol Blue, Bromochlorophenol Blue and Bromocresol Green is described. Berberine was extracted in large amounts into 1,2-dichloroethane with A2-; only in the presence of quinidine in a neutral aqueous media. Berberine could react in 1,2-dichloroethane with A2- to give a blue product. In addition, the extractability of berberine in a neutral aqueous media could be enhanced by the formation of bulky ternary complexes (berberine+-A2-(-)quinidine+); the selectivity was improved because most of the amines and alkaloids did not react with A2- in the above-mentioned media. The blue complexes can be used for a sensitive and selective spectrophotometric determination of berberine in crude drugs.