Method for the determination of lycopene in supplements and raw material by reversed-phase liquid chromatography: single-laboratory validation.

A single-laboratory validation study was conducted for a liquid chromatographic (LC) method for the determination of total and all-trans-lycopene in a variety of dietary supplements and raw materials. Gelatin-based and other water-dispersible beadlets, or tablets, capsules, and softgels containing such product forms, were digested with protease. Alginate formulations and the respective applications were treated with an alkaline sodium EDTA acetate buffer to release lycopene from the matrix. Lycopene and other carotenoids were extracted from the resulting aqueous suspensions with dichloromethane and ethanol. Oily product forms were directly dissolved in dichloromethane and ethanol. The extracts were chromatographed on an isocratic high-performance LC system using a C16 alkylamide modified silica column that provided satisfactory resolution of all-trans-lycopene from its predominant cis-isomers and separated the lycopene isomers from other carotenoids such as alpha- and beta-carotene, cryptoxanthin, lutein, and zeaxanthin. The within-day precision relative standard deviation (RSD) for the determination of total lycopene ranged from 0.9 to 5.7% over concentration ranges of 50-200 g/kg for raw materials and 0.3-24 g/kg for dietary supplements. The intermediate precision RSD (total RSD) ranged from 0.8 to 8.9%. Recoveries obtained for beadlet and tablet material for the different extraction variants ranged from 95.0 to 102.1% at levels of 0.02-20 g/kg for tablets and from 95.0 to 101.1% at levels of 1-200 g/kg for beadlet material.