Determination of active ingredients in cough-cold preparations by micellarliquid chromatography

The chromatographic behaviour of some active ingredients in cough-cold phar maceutical preparations, the antihistamine chlorpheniramine (or the dextro enantiomer dexchlorpheniramine), and the phenethylamines phenylephrine, phe nylpropanolamine and pseudoephedrine, has been studied using a C-18 column, micellar mobile phases of sodium dodecyl sulphate (SDS) and pentanol, and with UV detection. All possible combinations of chlorpheniramine/phenethyla mine were resolved and determined using a mobile phase of 0.15 M SDS-6% (v/ v) pentanol at pH 7, with analysis time below 7 min. Repeatabilities and wi thin laboratory precisions were evaluated at four different drug concentrat ions in the range 0.5-25 mug ml(-1) (n = 5), resulting RSDs below 1.6%. The drug amounts found in the analysis of 14 commercialised preparations agree d with those declared by the manufacturers within the tolerance limits, and with those obtained using an aqueous 60% (v/v) methanol reference mobile p hase. No interference was observed from other accompanying drugs such as ac etylsalicylic acid, ascorbic acid, betamethasone, caffeine, codeine phospha te, diphenhydramine, lactose, paracetamol, and prednisolone. The studied co mbinations required a rather high amount of methanol in conventional RPLC t o be eluted from the column. In contrast, the proposed procedure used a muc h lower amount of organic solvent (pentanol), which is highly retained in t he SDS solution, being also less toxic than methanol. (C) 2001 Elsevier Sci ence B.V. All rights reserved.