A Note on TLC Densitometry for Drug and Metabolite Determination

Abstract

Although in our Department we make extensive use of HPLC, GC and GC-MS, we have also found quantitative TLC to be a very useful technique for the analysis of drugs and metabolites in body fluids. This approach is not often discussed but deserves mention since the equipment is simple and the thin-layer plate can accept heavy loading of relatively crude extracts of plasma. Analytical methods can be developed quickly as extensive ‘clean-up’ is not necessary. The procedure calls for automatic equiment. We use a ‘Multi-spotter’ (A.I.S.; from Universal Scientific, London) and the Vitatron densitometer which can quantitate compounds on TLC plates by direct absorption in visible or UV light, by fluorescence quenching (a fluorescent substance being incorporated in the absorbent layer), or by fluorescence emission. Examples are now given.