Evaluation and validation of an LC method for the analysis of carotenoids in vegetables and fruit

In many epidemiologic studies, an increased intake of fruits and vegetables was associated with a reduced risk of various cancers. Research on possible anticarcinogenic compounds is often focussed on carotenoids. We elaborated a method for the determination of lutein, zeaxanthin, α-carotene, β-carotene, lycopene and β-cryptoxanthin in fruit and vegetables. After extraction, carotenoids were dissolved and a fraction was injected onto the LC-system and chromatographed isocratically on a Vydac polymer C18 column. The mobile phase was a mixture of methanol and THF (95/5 vv). Carotenoids were detected at 450 nm using a diode array detector. The separation between the individual carotenoids was satisfactory and the interference of other compounds small. Low recoveries (60%) for lycopene were found due to presence of hastalloy frits in LC system. Problems were solved by changing them for PAT (Peek Alloyed with Teflon) frits. Values for repeatability relative standard deviation (RSDr) of carotenoids in carrot, spinach, tomato, corn and tangerine ranged from 1.9–4.9%. The mean standard recoveries for carotenoids in tomato and tangerine ranged from 93–107%. With this procedure, carotenoids may be determined in fruits and vegetables under routine conditions, yielding reliable and reproducible results.