Rodriguez-Amaya D B, Kimura M, Godoy H T, Arima H K
Departamento de Ciência de Alimentos, Faculdade de Engenharia de Alimentos, Universidade Estadual de Campinas, SP, Brazil.
J Chromatogr Sci. 1988 Dec;26(12):624-9. doi: 10.1093/chromsci/26.12.624.
Determination of provitamin A content by open column chromatography/visible absorption spectrophotometry is assessed using food samples of varying carotenoid composition. A general method consisting of extraction with acetone, transfer to petroleum ether, saponification (optional), concentration, separation on activated MgO:Hyflo Supercel column developed with 1 to 15% acetone in petroleum ether, and quantitation of individual provitamins spectrophotometrically demonstrates repeatability comparable with that of high-performance liquid chromatographic (HPLC) methods. Overnight saponification (10% methanolic KOH, ambient temperature) does not degrade the provitamins and is unnecessary for kale, tomato, and squash; however, it is required for good separation of papaya carotenoids due to the presence of carotenol esters. The current Association of Official Analytical Chemists (AOAC) method is found to be inappropriate because (1) the volume of extracting solvent is not adjusted to the type of sample; (2) the less active alpha- and gamma-carotene, alpha- and beta-cryptoxanthin, and 5,6-monoepoxy-beta-cryptoxanthin (50% active) are quantified as beta-carotene (100% active); (3) inactive carotenoids such as xi-carotene and zeinoxanthin are also quantified as beta-carotene.
采用柱色谱/可见吸收分光光度法测定不同类胡萝卜素组成的食品样品中维生素原A的含量。一般方法包括用丙酮萃取、转移至石油醚、皂化（可选）、浓缩、在以1%至15%丙酮的石油醚溶液展开的活性氧化镁：硅藻土柱上分离，以及通过分光光度法定量单个维生素原，该方法的重复性与高效液相色谱（HPLC）法相当。过夜皂化（10%甲醇氢氧化钾，室温）不会降解维生素原，对于羽衣甘蓝、番茄和南瓜来说没有必要；然而，由于存在类胡萝卜醇酯，木瓜类胡萝卜素的良好分离需要皂化。发现现行的美国公职分析化学师协会（AOAC）方法不合适，原因如下：（1）萃取溶剂的体积未根据样品类型进行调整；（2）活性较低的α-和γ-胡萝卜素、α-和β-隐黄质以及5,6-单环氧-β-隐黄质（50%活性）被定量为β-胡萝卜素（100%活性）；（3）无活性的类胡萝卜素如ζ-胡萝卜素和玉米黄质也被定量为β-胡萝卜素。
