Determination of phospholipids from pulmonary surfactant using an on-line coupled silica/reversed-phase high-performance liquid chromatography system.

A basic normal-phase HPLC separation of phospholipids can be improved by introducing a limited contribution of solvophobic retention. For this purpose, the effect of an additional alkylsilica (C18) column of variable length coupled in series with a silica column was investigated. With increasing percentage of reversed phase in this system, the retention of phosphatidylglycerol increased. Phosphatidylinositol and phosphatidylserine were separated into molecular species. The "selective retention" defined in this study permits an evaluation of the solvophobic retention of phospholipids in the coupled system. An alternative column switching procedure is used for specific applications of the biphasic separation on chosen phospholipids. With this system, determination of phosphatidylglycerol and six other phospholipids from pulmonary surfactant could be performed.