Ion-pair reversed-phase liquid chromatographic identification and quantitation of papaverine congeners.

A reversed-phase ion-pair high-performance liquid chromatographic separation was developed for identification and quantitation of papaverine drug congeners, namely papaverine (1), moxaverine (2), drotaverine (3), and ethaverine (4) hydrochlorides. A synthetic reference mixture of the four congeners in the range 1-4 micrograms showed good separation. With a reference standard (codeine phosphate), the relative retention times to codeine were 1.356, 1.984, 2.46, and 2.91 (mean of six) for 1, 2, 3, and 4, respectively. Good linearity was obtained in the quantitation of 1 and 2 in the range 1-2 micrograms [correlation coefficient (r), 0.9978 and 0.9997, respectively] and 3 and 4 in the range 2-4 micrograms, (r, 0.9998 and 0.9991, respectively). Analysis of some commercial dosage forms containing one of these congeners showed good recovery with sufficient accuracy and precision. The method was sensitive and permitted the use of small sample sizes or unit doses.

Application of orthogonal functions to spectrophotometric analysis of the preservatives benzylalcohol, phenol and parabens in aqueous cyanocobalamin solutions.

The orthogonal polynomials P3 and P2, 12 and 8 points, at 2 nm intervals over certain wavelength ranges were used for the spectrophotometric analysis of benzylalcohol, phenol or parabens in aqueous cyanocobalamin solutions. The 12 point-methods proved to be more sensitive and direct and to have sufficient accuracy and precision.

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.