1 Department of Pediatrics, School of Medicine, University of California, San Diego, P.O. Box 109, La Jolla, California 92037
Dr. Roux is correct; the procedure he outlines and executes which is his own modification is neither valid nor reliable.
We use Silica Gel H containing (NH4)2SO4 (Dr. Roux did not) which gives a different chromatographic separation from his. His statements about Eastman chromatogram sheets No. 6061 do not apply; these cannot be charred. His application of a large overload of phospholipids (0.5 mg) gives poor separation on TLC; we use about 30 µg. We long ago advised Dr. Roux that we stopped spraying with H2SO4 since this chars less uniformly than does the heated (NH4)2SO4-Silica Gel H plate.