Determination of melatonin in pharmaceutical formulations and human plasma by gas chromatography-electron impact mass spectrometry.

A simple and reliable method for gas chromatography-mass spectrometry (GC-MS) has been developed for the determination of melatonin in commercially available tablet formulations and human plasma. The dissolution of the tablets in ethyl acetate was simply obtained by sonication. The filtrate of the resultant solution, after concentration, was derivatized with pentafluoropropionic anhydride (PFPA) and analysed by GC-MS using splitless injection. The linear response range for melatonin was 5-250 ng on column. The same method can be used, with minor modifications, for the determination of melatonin in spiked human plasma in the range 50-1000 pg/mL plasma.