SELECTIVE CHROMATOGRAPHIC DETECTION OF TERTIARY N-ETHYL DRUGS

Document Type : Original Article

Authors

Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt

Abstract

There are reagents available for the detection of basic drugs in general on paper and thin layer chromatograms. However, reagents selective for specific groups of basic drugs are few and usually differentiate compounds with grossly different structural features. There are no reagents available to differentiate tertiary, N-ethyl drugs from their N-methyl analogues. These compounds have common occurance among pharmaceuticals and are frequently prescribed in the same dosage form (e.g, cough, mixture containing N-ethyl antitussive with N-methyl antihistamine or an ephedrine analogue). N-methyl and N-ethyl compounds usually have close pKa values and similar solubility characteristics. This renders clear-cut separation in paper chromatography (PC) or thin layer chromatography (TLC) not always feasible. Thus identification of either type through Rf-values alone is not decisive.