Analysis of food supplements with melatonin in their composition using high-performance liquid chromatography

The aim of research: to do a qualitative analysis of supplements with melatonin using thin-layer chromatography and to do qualitative and quantitative analysis of those supplements using high-performance liquid chromatography. Research objects and methods: selected objects were 8 food supplements, bought at drugstores in Lithuania, with melatoin in their composition. All of those objects were dissolved in methanol and the extracts were qualitatively analysed using TLC. Samples were applied on HPTLC Silica Gel 60 F254 10x10 cm chromatographic plates using CAMAG Linomat 5 equipment. For mobile phase toluene, ethyl acetate and formic acid (5:4,5:0,5) were used. For spot visualization CAMAG TLC visualizer was used (254 nm wave length). 8 supplements dissolved in methanol were analyzes with HPLC. During analysis Waters e2695 separations module with photo diode array detector Waters 2998 PDA was used. ACE 5 C18 250 x 4,6 mm id column was used for separation. Mobile phase consisted of acetonitrile and 0,1 pct. trifluoracetic acid. The temperature inside the column was maintained at 25oC. Results and conclusions: 8 samples of food suplements were analysed using TLC and HPLC. Both methods were suitable for qualitative evaluation of melatonin in food supplements. Melatonin was identified in every sample and standart errors fluctuated between 0,002-0,004 during TLC analysis and 0,09-0,046 during HPLC analysis. Standart deviations varied between 0,0032-0,00702 during TLC and 0,0150-0,0792 during HPLC. Quantitative analysis using HPLC showed that all analytes are below the thresholds which are pointed out on the packaging. Every supplement had less than 1 mg of melatonin in their composition. The biggest amount was found in M.P.1 – 0,947 mg which is about 90 pct. of the indicated amount. The lowest quantity was found in M.P.7 – 0,2745 mg or 0,27 pct. of the submitted amount