Ghanekar A G, Das Gupta D
J Pharm Sci. 1978 Sep;67(9):1247-50. doi: 10.1002/jps.2600670915.
Paired ion high-pressure liquid chromatography was useful for separating intact catecholamines (epinephrine, isoproterenol, levodopa, and methyldopa) and phenylephrine from some of their decomposition products. Furthermore, methyldopa was separated from either hydrochlorothiazide of levodopa. Under identical conditions without 1-heptanesulfonic acid (a counterion for paired ion chromatography) in the mobile phase, these separations were not possible. Paired ion chromatography also was tried successfully for the quantitative determinations of isoproterenol, levodopa, methyldopa, and phenylephrine in some dosage forms. The results were compared with the results obtained using some literature methods.
