Delgado-Zamarreño M M, Sanchez-Perez A, Gomez-Perez M C, Hernandez-Mendez J
Department of Analytical Chemistry, Nutrition and Food Science, Faculty of Chemistry, University of Salamanca, Spair.
J Chromatogr A. 1995 Mar 10;694(2):399-406. doi: 10.1016/0021-9673(94)01142-2.
We developed an on-line system for the determination of liposoluble vitamins A, D3 and E in milk, both liquid and in powder form, using an automated sample treatment system coupled to chromatographic determination. For this, C18 cartridges were used because of the strong capacity of this material for the extraction and preconcentration of such vitamins, its ease in handling and the possibility of coupling it with automatic analysis systems. Alkaline hydrolysis of the samples was performed in an on-line system comprising two confluent channels through which the sample solution and alcoholic sodium hydroxide plus ascorbic acid flowed for a given period of time. A third channel merged with the other two to neutralize the solution before it arrived at the C18 cartridge. The latter, inserted into a loop with a six-port injection valve, retained the soluble vitamins. The vitamins were eluted with a stream of methanol and the eluate was automatically injected into the chromatographic system. Variables affecting the on-line system were optimized: sample size, flow-rate, preconcentration, washing and elution times, etc. The recoveries for powdered and liquid milk for the three vitamins assayed ranged between 80 and 105% (n = 10). Additionally, a day-to-day precision (10 days) of the method of 4.5% was obtained for the different vitamins.
我们开发了一种在线系统，用于测定液态和粉状牛奶中的脂溶性维生素A、D3和E，该系统采用自动样品处理系统与色谱测定相结合的方式。为此，使用了C18柱，因为这种材料对这些维生素具有很强的萃取和预浓缩能力，易于操作，并且可以与自动分析系统联用。样品的碱性水解在一个在线系统中进行，该系统包括两个汇合通道，样品溶液、乙醇氢氧化钠和抗坏血酸在给定时间内流经这两个通道。第三个通道与另外两个通道汇合，在溶液到达C18柱之前将其中和。将C18柱插入带有六通进样阀的定量环中，保留可溶性维生素。用甲醇流洗脱维生素，洗脱液自动注入色谱系统。对影响在线系统的变量进行了优化：样品量、流速、预浓缩、洗涤和洗脱时间等。所测定的三种维生素在粉状和液态牛奶中的回收率在80%至105%之间（n = 10）。此外，该方法对不同维生素的日常精密度（10天）为4.5%。
