Analysis of lycopene in nutritional supplements by silica gel high- performance thin-layer chromatography with visible-mode densitometry

A quantitative method using silica gel 60 HPTLC plates, automated bandwise sample application, petroleum ether-dichloromethane 9:1 as mobile phase, and automated slit-scanning densitometry has been developed for the analysis of lycopene in nutritional supplements consumed to reduce the risk of prostate cancer and other forms of cancer and cardiovascular disease. Four products containing 300 μg, 3 mg, 5 mg, or 10 mg lycopene plus other ingredients were analyzed using a ChromaDex lycopene standard. The amount of lycopene in the tested samples ranged from 77.7 to 98.1% relative to the stated label values. Accuracy was validated by spiked blank analysis, and precision by performing replicate analysis. Accuracy was found to be within 1.90% of theoretical values for the 3 mg softgels and 1.10% of theoretical values for the 10 mg softgels, and precision was 1.44% relative standard deviation (RSD) for the 10 mg softgels and 2.39% RSD for the spiked blank for the 3 mg softgels. Lycopene standards available from two other companies were analyzed and found to contain 55.6, 57.6, and 20.0% of the minimum amount expected from the stated label values. © 2008 Akadémiai Kiadó, Budapest.