Perfetti G A, Joe F L, Diachenko G W
Food and Drug Administration, Division of Food Chemistry and Technology, Washington, DC 20204.
J Assoc Off Anal Chem. 1989 Nov-Dec;72(6):903-6.
A liquid chromatographic (LC) method is described for the determination of sulfite in grapes and certain grape products. Sulfite is extracted from grapes with aqueous formaldehyde solution buffered at pH 5; free sulfite is converted to hydroxymethylsulfonate (HMS), which is extremely stable at pH 3-7. Subsequent heating to 80 degrees C for 30 min converts reversibly bound forms of sulfite to HMS. The extract is then analyzed by reverse-phase ion-pairing liquid chromatography, using a C18 column and a mobile phase of aqueous 0.005 M tetrabutylammonium ion in 0.05 M acetate, pH 4.7, and a flow rate of 1 mL/min. Aqueous KOH is added to the eluate to convert HMS to free sulfite, which is then treated with 5,5'-dithiobis[2-nitrobenzoic acid]. This reaction produces the 3-carboxy-4-nitrothiophenolate anion, which is determined by measurement of electronic absorption at 450 nm. For grapes spiked with HMS at 5-20 ppm (as SO2), recoveries ranged from 92 to 112%, with a coefficient of variation of 4.6%. The method was also used to determine sulfite in various grape products. Results were comparable to those obtained by the AOAC official Monier-Williams method.
描述了一种用于测定葡萄及某些葡萄产品中亚硫酸盐的液相色谱（LC）方法。用pH值为5的甲醛水溶液从葡萄中提取亚硫酸盐；游离亚硫酸盐转化为羟甲基磺酸盐（HMS），其在pH 3 - 7时极其稳定。随后加热至80℃ 30分钟，可将亚硫酸盐的可逆结合形式转化为HMS。然后通过反相离子对液相色谱法分析提取物，使用C18柱，流动相为0.05 M乙酸盐中含0.005 M四丁基铵离子的水溶液，pH 4.7，流速为1 mL/min。向洗脱液中加入氢氧化钾水溶液，将HMS转化为游离亚硫酸盐，然后用5,5'-二硫代双[2-硝基苯甲酸]处理。该反应产生3-羧基-4-硝基硫酚酸根阴离子，通过在450 nm处测量电子吸收来测定。对于添加了5 - 20 ppm（以SO₂计）HMS的葡萄，回收率在92%至112%之间，变异系数为4.6%。该方法还用于测定各种葡萄产品中的亚硫酸盐。结果与通过AOAC官方莫尼尔 - 威廉姆斯法获得的结果相当。
