Brause Allan R, Woollard David C, Indyk Harvey E
Analytical Chemical Services of Columbia Inc., 9110 Red Branch Rd, Columbia, MD 21045, USA.
J AOAC Int. 2003 Mar-Apr;86(2):367-74.
A interlaboratory study was conducted to evaluate a liquid chromatographic (LC) procedure for the determination of total vitamin C in foods at levels of 5-60 mg/100 g. Emphasis was placed on fruit juices, although selected foods were also included in the study. Following dissolution of sample in water, endogenous dehydroascorbic acid was converted to ascorbic acid by precolumn reduction with dithiothreitol at neutral pH. Total ascorbate was determined by C18 reversed-phase LC with a phosphate eluent at pH 2.5, incorporating dithiothreitol to maintain vitamin C in the reduced form, and UV detection at 254 nm. Seven types of fruit juices and foods were tested by 19 collaborators in 7 countries. Three duplicate juices and foods met the criteria for Youden pairs and yielded repeatability relative standard deviation of 5.80-14.66%. Reproducibility relative standard deviation ranged from 6.36 to 35.54% (n = 10) with HORRAT values of 0.82-4.04. The LC method is suitable for routine use in fruit products and foods containing > 5 mg/100 g vitamin C and is recommended for further validation by AOAC INTERNATIONAL and International Fruit Juice Union.
开展了一项实验室间研究，以评估一种液相色谱（LC）方法，用于测定食品中含量为5 - 60毫克/100克的总维生素C。尽管研究中也包括了选定的其他食品，但重点是果汁。将样品溶解于水中后，在中性pH条件下用二硫苏糖醇进行柱前还原，将内源性脱氢抗坏血酸转化为抗坏血酸。采用C18反相液相色谱法，以pH 2.5的磷酸盐洗脱液进行洗脱，加入二硫苏糖醇以保持维生素C处于还原形式，并在254纳米处进行紫外检测，从而测定总抗坏血酸含量。来自7个国家的19位合作者对7种果汁和食品进行了测试。三种双份果汁和食品符合尤登对标准，重复性相对标准偏差为5.80 - 14.66%。再现性相对标准偏差范围为6.36至35.54%（n = 10），霍拉特值为0.82 - 4.04。该液相色谱法适用于维生素C含量大于5毫克/100克的水果制品和食品的常规检测，建议美国官方分析化学家协会（AOAC INTERNATIONAL）和国际果汁联盟进一步验证。
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