Abstract
Methods for separation and determination of provitamin A, were investigated by thin-layer chromatography (TLC) using calcium hydroxide as an adsorbent. 1) The solvent systems for fractionation of carotenoids were n-hexane or n-propanol/n-hexane (5:95). Development with n-hexane was most suitable for distinct separation of α-, β- and ζ-carotenes. When the TLC was developed first with n-hexane, the carotenes were separated from xanthophylls. Then, further development with n-propanol/n-hexane (5:95), separated β-cryptoxanthin from other xanthophylls. 2) Determination after elution: After the chromatogrphy, the fractions on the TLC plate were quantitatively scraped out and eluted with ethanol/n-hexane (1:10). After removal of the solvent under reduced pressure, various compounds dissolved in n-hexane were assayed in a spectrophotometer. Recoveries of α-carotene, β-carotene and β-cryptoxanthin were more than 90%. It was suggested that the method is suitable for quantitative analysis of provitamin A. 3) TLC-densitometry: Quantitative analysis of α- and β-carotenes by TLC-densitometry was also studied. The calibration curves and recovery tests were determinative, and it would be applicable to the practical use.
