Quantitative high-performance thin-layer chromatography of lipids in plasma and liver homogenates after direct application of 0.5-microliter samples to the silica-gel layer

Lipid profiles were determined by high-performance thin-layer chromatography (HPTLC) after direct application of 0.5 microliter plasma from capillary blood to the silica-gel layer. Coefficients of variation for the fluorescence measurements were 2.1% for phosphatidylcholine. The recovery of known amounts of lipid was 96--100%. A linear relationship between peak area and amount of lipid was found in the nmole range, corresponding to the amount of lipid in 0.125--0.75 microliter Lipid-Trol, which served as the standard reference sample. The plasma lipids of healthy subjects and of patients suffering from various illnesses were analyzed using reference methods and HPTLC. Identical values were obtained for cholesterol esters, triacylglycerols and phosphatidylcholine. Free cholesterol values determined by HPTLC were slightly lower (7%). The correlation between data obtained by reference methods and HPTLC was as follows: cholesterol, r = 0.938; cholesterol esters, r = 0.964; triacylglycerols, r = 0.985; phosphatidylcholine, r = 0.938. The separaiton and quantitation of liver lipids using HPTLC after direct application of the tissue homogenate to the silical-gel layer was carried out. Comparison with reference methods revealed that HPTLC gave higher cholesterol values (24%). The triacylglycerol concentrations, however, were identical under both methods and correalted satisfactorily (r = 0.959).