title: Spectrophotometric determination of trace amounts of quaternary ammonium salts in drugs by ion-pair extraction with bromophenol blue and quinine.
mesh_terms: D001558:Benzethonium / Q000302:isolation & purification*; D001599:Berberine / Q000302:isolation & purification*; D001600:Berberine Alkaloids / Q000302:isolation & purification*; D001978:Bromphenol Blue; D004338:Drug Combinations; D010636:Phenols; D000644:Quaternary Ammonium Compounds / Q000302:isolation & purification*; D011803:Quinine
chemical_list: D001600:Berberine Alkaloids; D004338:Drug Combinations; D010636:Phenols; D000644:Quaternary Ammonium Compounds; D001599:Berberine; D001978:Bromphenol Blue; D001558:Benzethonium; D011803:Quinine