Spectrophotometric determination of ephedrine HCl, cinchonine HCl, chlorpheniramine maleate, atropine sulphate and diphenhydramine HCl by solvent extraction of reineckate complexes.

A spectrophotometric method for the determination of some alkaloids (namely ephedrine HCl, cinchonine HCl, chlorpheniramine maleate, atropine sulphate and diphenhydramine HCl) as separate compounds as well as in pharmaceutical preparations through the formation of their ion-pair (reineckate complexes) is described. These complexes were prepared and the final products were extracted with nitrobenzene in situ. The optimum conditions for complete extraction were evaluated by investigating the nature of solvent, pH, time of shaking, temperature and reineckate concentrations. The absorption spectra of the extracted organic layer were measured at 520 nm. The extraction constants were calculated and found to have a mean of log KE congruent to 2. The application of the present method was compared with the accepted pharmacopoeia method and the effects of some interfering ions were also studied.