Comparative study of solid-phase and liquid-phase extraction techniques for isolation of phospholipids from plasma.

A liquid-liquid extraction technique and six solid absorbents, silica gel, octadecyl silica (C18), XAD-2, XAD-4, XAD-7 and XAD-8, were compared as effective tools for extraction of phosphatidylcholine (Ptd C), phosphatidylethanolamine (Ptd E), phosphatidylinositol (Ptd I) and phosphatidylserine (Ptd S) from plasma. Using liquid-liquid extraction the recovery of the four phospholipids was in the order of 60% in organic phase and 20% in the liquid interface. Neither silica gel nor C18 materials significantly adsorbed phospholipids from plasma. Amberlite resins were more selective for removal of phospholipids. A recovery of greater than 85% was obtained for Ptd C, Ptd I and Ptd S when XAD-7 or XAD-8 were used as adsorbents. A recovery of approximately 90% for Ptd E was obtained when XAD-2 or XAD-4 were used as adsorbents. A solvent mixture of isopropanol-acetonitrile (1:1) was found to be the most effective eluent for removal of phospholipids from amberlite polymeric resins. These results suggest that resins could be used as an extracting tool for removal of phospholipids from body fluids.