Comparison of a liquid solvent extraction technique and supercritical fluid extraction for the determination of alpha- and beta-carotene in vegetables.

An ethanol-pentane solvent extraction procedure and a supercritical CO2 extraction procedure are compared for the high-performance liquid chromatographic determination of alpha- and beta-carotene in vegetables. The vegetables tested included carrots, collard greens, turnips, turnip greens, kale, mustard greens, broccoli florets, zucchini, and squash. Homogenization of the sample prior to liquid or supercritical fluid extraction significantly improved recovery of the carotenoids. A combination of static and dynamic modes of extraction with ethanol modifier at 338 atm and 40 degrees C was necessary in order to achieve optimum recovery with the supercritical fluid procedure. beta-Carotene results with the supercritical CO2 procedure averaged 23% higher than results for the liquid extraction procedure. Only corn and carrots contained detectable levels of alpha-carotene, and, in both cases, liquid extraction yielded slightly higher results. Liquid extractions were performed in approximately 90 min, and supercritical fluid extractions were performed in 30 min; however, the supercritical fluid extractions procedure required less than 10 min of an analyst's time while the liquid extraction procedure was labor intensive.