The introduction of thin-layer chromatography (TLC) somewhat more than a decade ago has made separation of lipids into compound classes a practical matter. Separation of lipid classes on a quantitative basis, however, has remained a problem. None of the current methods for class separation were satisfactory in giving clear separation of amounts of lipid needed by our laboratory.
Neither were they conveniently adapted to readily available laboratory equipment.
This report shows how bands of cholesterol esters, triglycerides, free fatty acids, cholesterol, and phospholipids are separated from total lipid extracts for quantitative recovery on 20 x 20 cm commercially prepared sheets of silica gel by a two-step development procedure.
Because of the polarity extremes among lipid classes, use of a single-step solvent system has not proven feasible. The difficulties inherent in trying to chromatograph a mixture of non-polar and more polar lipids by using a one-step developer have been discussed by Freeman and West'. In 1969 Manners et ~1.~ reported that no one-step development was available although earlier Storry and Tuckley3 had used special equipment to accomplish such resolution. Some of the difficulties in achieving lipid class separation are solved by using a step-wise procedure of development that utilizes a polar solvent system preceding, or following a non-polar system. The rationale for using a step-wise approach for lipid class separation instead of a single-step system has been reviewed by Browning4.