Interlaboratory studies of HPLC procedures for the analysis of carotenoids in foods

This paper describes the use of a potential reference material in interlaboratory studies for the analysis of carotenoids in a mixed vegetable material. Seventeen European laboratories have carried out collaborative studies to assess the accuracy of HPLC procedures for the measurement of lutein, zeaxanthin, lycopene, α-carotene and β-carotene in a vegetable mix. The studies investigated possible problem areas including chromatographic systems, standardization of carotenoid stock solutions, extraction procedures and data handling. The results suggested that the effect of the chromatographic system is probably not a major variable, although some systems achieved a more discrete separation of carotenoid isomers than others. In the more experienced laboratories, variation in the standardization of the carotenoid solution was not thought to be a significant problem. However, there were greater variations for lycopene calibration and measurement. Preliminary conclusions from these studies suggested that the preparation of the carotenoid extract may account for about 13% of the overall variance of around 23%.