Applications of paired ion high pressure liquid chromatography to some catecholamines (epinephrine, isoproterenol, levodopa and methyldopa) and phenylephrine

Paired ion high pressure liquid chromatography has been shown to be a useful technique for the separation of intact catecholamines: epinephrine hydrochloride, isoproterenol hydrochloride, levodopa and methyldopa from some of their products of decomposition. Furthermore, it has been shown that methyldopa can be separated either from hydrochlorothiazide or from levodopa using paired ion chromatography. Under identical conditions, without the presence of 1-heptane sulfonic acid (the counter ion for paired ion chromatography) in the mobile phase, these separations are not possible. The phenylephrine hydrochloride has also been separated from phenylpropanolamine hydrochloride, brompheniramine maleate and sodium benzoate successfully using the counter ion. Moreover, paired ion chromatography has been applied to the quantitative determination of isoproterenol hydrochloride, levodopa, methyldopa and phenylephrine hydrochloride in some commercial dosage forms. The results obtained by the developed method have been compared with other literature methods. The comparison is very favorable.