Ion-pair liquid chromatographic assay of decongestants and antihistamines.

The quantitative determinations of combinations of antihistamine and decongestant drugs including phenylephrine, dl-ephedrine, psi-ephedrine, phenylpropanolamine, pyrilamine, pheniramine, l-ephedrine, chlorpheniramine, brompheniramine, oxymetazoline, naphazoline, and antazoline contained in solid and liquid dosage forms are described. All active ingredients except the ephedrine optical isomers were separated from other ingredients with ion-paired high-pressure liquid chromatography. Manipulation of the mobile phase either by changing the hydroalcoholic ratio or by changing the alkyl chain length of the counterion (sulfonic acid) for achieving optimum separations is discussed. The method is simple, short, accurate, and precise.