Quantitative Spectrodensitometry of Silica Gel Thin Layers Impregnated With Sulfuric Acid

Impregnating silica gel layers with sulfuric acid prior to development of the chromatogram overcomes problems of spraying. Silica gel G plates (250 µ) were dipped for 30 sec in a solution of 4% sulfuric acid in methanol (v/v). After drying, chromatography can be carried out in the usual manner. Separations were comparable to those obtained with normal plates but using solvent systems of lower polarity. After development the plates were heated in an oven at 140° for 20 min for complete charring. At 120° for 10 min various colors developed. Using a Schoeffel Model 3000 double beam spectrodensitometer linear calibration curves were obtained for steroids and fatty acids in submicrogram ranges.