Spectrophotometric determinations of 3-dimethylaminomethylkhellin hydrochloride and khellin

Spectrophotometric assays are proposed for the determination of 3-dimethylaminomethylkhellin hydrochloride and khellin in bulk chemical and dosage forms. The acid dye method, using methyl orange at pH5, is applied to assay the amine in the form of an ion-pair extractable in chloroform with maximum abosrbance at 420 nm. The perchloric acid method, depending on formation and extraction of the oxonium salts of both compounds, is used to assay the amine and khellin at 333 or 430 nm and at 325 or 410 nm, respectively. The reineckate method can be used to assay the amine as the reineckate derivative in acetone with maximum absorbance at 530 nm. However, small amounts of the amine (1.5--3 mg) can be determined as the reineckate in methanol with maximum absorbance at 245 nm. Stability determination of the two compounds can be done by the acid dye and perchloric acid methods. The three methods are sufficiently accurate, sensitive, and precise.