Quantitative Densitometry on Thin Layer Plates of Silica Gel Impregnated with Phosphomolybdic Acid

Thin layer chromatograms using silica gel with 10% phosphomolybdic acid have been developed. Incorporation of phosphomolybdic acid into the silica gel before spreading on the plates provides a medium for both separation and quantitation. After development, heating of the plates at 110°C for 20 minutes results in reproducible spot density. Linear calibration curves for serial amounts of steroids were obtained after densitometry of spots with a Schoeffel Model 3000 double beam spectrodensitometer. Reproducible spot density with amounts as low as 0.05 µg have been shown. Preliminary results for quantitation of estriol in biological fluids are presented. The results compare favorably with those obtained by GC.