Sundaresan P Ramnathan
U.S. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Division of Research and Applied Technology, College Park, MD 20740, USA.
J AOAC Int. 2002 Sep-Oct;85(5):1127-35.
Several liquid chromatography (LC) methods for analysis of vitamin A in foods and feeds have been previously reported but only a few have been applied in non-food matrixes. A validated LC method is needed for determination of vitamin A and beta-carotene in the various matrixes presented by dietary supplements. The performance of a reversed-phase method with methanol-isopropanol gradient elution was evaluated with standard retinyl derivatives and beta-carotene. The reversed-phase method is capable of separating retinol from other derivatives such as retinyl acetate, retinyl palmitate, and beta-carotene. Two types of extraction were used to extract the analytes from the dietary supplements: a hexane-methylene chloride extraction for soft-gel capsules containing beta-carotene, and a direct solvent extraction for dietary supplements in tablet form. The direct solvent extraction consisted of treatment with ethanol and methylene chloride following addition of hot water (55 degrees C). Results with the reversed-phase method for vitamin A and beta-carotene in the products examined (n = 8) indicated excellent method performance. The main form of vitamin A or beta-carotene in dietary supplements was the all-trans isomer. The reversed-phase method avoids saponification and is rapid, accurate, precise, and suitable for simultaneous determination of retinyl derivatives and beta-carotene in dietary supplements.
此前已有多篇关于食品和饲料中维生素A分析的液相色谱（LC）方法的报道，但仅有少数方法应用于非食品基质。对于膳食补充剂中各种基质的维生素A和β-胡萝卜素的测定，需要一种经过验证的LC方法。采用标准视黄醇衍生物和β-胡萝卜素对甲醇-异丙醇梯度洗脱的反相方法的性能进行了评估。该反相方法能够将视黄醇与其他衍生物如乙酸视黄酯、棕榈酸视黄酯和β-胡萝卜素分离。采用两种萃取方法从膳食补充剂中萃取分析物：对于含有β-胡萝卜素的软胶囊采用己烷-二氯甲烷萃取，对于片剂形式的膳食补充剂采用直接溶剂萃取。直接溶剂萃取包括在加入热水（55℃）后用乙醇和二氯甲烷处理。在所检测的产品（n = 8）中，采用反相方法测定维生素A和β-胡萝卜素的结果表明该方法性能优异。膳食补充剂中维生素A或β-胡萝卜素的主要形式是全反式异构体。该反相方法避免了皂化反应，快速、准确、精密，适用于同时测定膳食补充剂中的视黄醇衍生物和β-胡萝卜素。
