DIRECT QUANTITATIVE DIGITAL AUTORADIOGRAPHY TLC COUPLING FOR THE ANALYSIS OF NEUTRAL C-14 LIPIDS NEOSYNTHETIZED BY THE HUMAN SEBACEOUS GLAND

A simple digital autoradiographic-thin-layer chromatographic method is described for the direct quantification of the major sebaceous neutra l C-14-lipids (squalene, sterol esters, waxes, triglycerides, free fat ty acids, and free sterols). Direct quantification in the range of 20- 2000 disintegrations min(-1) (dpm) is performed by radioscanning the p late. For very low activities (15-100 dpm) enlargement of the opening window of the collector is necessary. Satisfactory accuracy (8.4%) is obtained both by external standardization of plates by use of calibrat ed amounts of neutral C-14-lipids and internal standardization of bioa ssays by use of radioactive dotriacontane. Some analytical criteria re lating to the stability of small amounts of neutral C-14-lipids on sil ica are discussed and quantification parameters depending on position- sensitive proportional counters are detailed. A radiometabolic pattern of neutral C-14-lipids obtained from one single human sebaceous gland is shown. The precision of the overall methodology, evaluated from a pool of neosynthesized lipids, is close to 15% for the range 50-100 dp m and reaches 8.5% for the range 300-2000 dpm.