Hydro-organic and micellar-organic reversed-phase liquid chromatographic procedures for the evaluation of sulphonamides in pharmaceuticals

Two reversed-phase liquid chromatographic procedures were developed for the analysis of ten pharmaceutical formulations used in medicine and veterinar y, which contained one of the following sulphonamides: sulphacetamide, sulp hadiazine, sulphaguanidine, sulphamethazine, sulphamethizole, sulphamethoxa zole, or sulphathiazole. In both chromatographic modes, the same C-18 colum n was utilized and the mobile phase contained a low amount of acetonitrile and citric buffer at pH 3.0. In one of the procedures, the surfactant sodiu m dodecyl sulphate was added to the mobile phase. The presence of micelles allowed a decrease in the amount of organic solvent from 11% to 6%, and fac ilitated sample dissolution. The surfactant also gave rise to changes in th e elution order and selectivity of the drugs. The analyses of the formulati ons were usually in good agreement with the claimed levels, and the results showed good precision. The procedures were simple and fast, the chromatogr aphic runs took less than 15 min and the samples were injected directly int o the chromatograph after dilution and filtration.