When tissue samples are very tiny (1 mm or less), the analysis of their lipid content (neutral lipids or phospholipids) may be effected directly on the TLC plate without previous extraction (Lecomte M et al., Prostagl Leukot Essent Fatty Acids 1998, 59, 363).
The tiny piece of tissue is directly applied in a small hole or groove made in the concentration zone (kieselgur preadsorbent) of the TLC plate (cf Whatman plates). This plate is then rapidly applied onto a steel plate pre-cooled in liquid nitrogen. After one or two minute freezing, the plate is lyophilized one or two hours under vacuum. The plate is then rapidly submitted to a solvent elution adapted to the desired analysis.