Melatonin: quantitative analysis in pharmaceutical oral dosage forms using thin-layer chromatography (TLC) densitometry

A thin-layer chromatography densitometric method for the quantitative analysis of melatonin in tablets and capsules has been developed. High-performance thin-layer chromatography (HPTLC) silica gel plates were used as the stationary phase and the elution was made with CH2Cl2MeOH (95:5). Densitometric evaluation of the spots was performed with a TLC scanner in reflectance mode at 223 nm with a deuterium lamp. A linear relation between the peak areas and the amount of melatonin deposited was found in the range 63–399 ng. The method was applied with success for the quantitative determination of melatonin in commercial and experimental samples.