Burini Giovanni
Department of Internal Medicine, Section of Applied Biochemistry and Nutritional Sciences, University of Perugia, Via San Costanzo, 06126 - Perugia, Italy.
J Chromatogr A. 2007 Jun 22;1154(1-2):97-102. doi: 10.1016/j.chroma.2007.03.013. Epub 2007 Mar 15.
A new method has been developed for the determination of total vitamin C in foods. The method requires less time than the traditional methodologies and uses a radical oxidation of L-ascorbic acid (AA) to obtain dehydro-L-ascorbic acid (DHAA) by means of a peroxyl radical generated in situ by thermal decomposition of an azo-compound, 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH). The dehydro-L-ascorbic acid is condensed with benzene-1,2-diamine (o-phenylenediamine, OPDA) to form its highly fluorescent quinoxaline derivative, 3-(1,2-dihydroxyethyl)furo[3,4-b]quinoxaline-1-one (DFQ), which is then separated on a C(18) column eluted with a mobile phase of 80 mM phosphate buffer and methanol at pH=7.8 and detected fluorometrically at lambda(ex)=355 nm and lambda(em)=425 nm. The reaction conditions for the complete conversion of AA to DFQ were 56 degrees C, 36 min and a mumol AAPH/AA ratio of 60. The sample, extracted with an aqueous metaphosphoric acid solution, was analyzed after being filtered through a 0.45 microm membrane. The method has shown good repeatability, sensitivity and accuracy compared to the results obtained with the reference method. The response of the detection system was linear within a range of 0.5-8.0 microg/mL with a correlation coefficient of 0.9997. The limit of detection was 0.27 microg/mL and the limit of quantification was 0.83 microg/mL. The AA contents of some selected foods were analyzed.
已开发出一种测定食品中总维生素C的新方法。该方法所需时间比传统方法少，利用偶氮化合物2,2'-偶氮二(2-脒基丙烷)二盐酸盐(AAPH)热分解原位生成的过氧自由基将L-抗坏血酸(AA)自由基氧化为脱氢-L-抗坏血酸(DHAA)。脱氢-L-抗坏血酸与苯-1,2-二胺(邻苯二胺,OPDA)缩合形成高荧光喹喔啉衍生物3-(1,2-二羟乙基)呋喃并[3,4-b]喹喔啉-1-酮(DFQ)，然后在C(18)柱上分离，用pH = 7.8的80 mM磷酸盐缓冲液和甲醇的流动相洗脱，并在λ(ex)= 355 nm和λ(em)= 425 nm处进行荧光检测。将AA完全转化为DFQ的反应条件为56℃、36分钟，AAPH/AA摩尔比为60。样品用偏磷酸水溶液萃取，经0.45μm滤膜过滤后进行分析。与参考方法得到的结果相比，该方法具有良好的重复性、灵敏度和准确性。检测系统的响应在0.5 - 8.0μg/mL范围内呈线性，相关系数为0.9997。检测限为0.27μg/mL，定量限为0.83μg/mL。分析了一些选定食品的AA含量。
