Toyoda M, Susuki H, Ito Y, Iwaida M
J Assoc Off Anal Chem. 1978 May;61(3):508-12.
The 2,4-xylenol method was modified and a gas-liquid chromatographic (GLC) method was developed for nitrate and nitrite determinations in several foods. Either a flame ionization (FID) or an electron capture detector (ECD) can be used. Proteins and fats are removed from warm alkaline water with zinc sulfate and filtered. The filtrate is evaporated to dryness, redissolved in water, and reacted with 2,4-xylenol in the presence of sulfuric acid to form 6-nitro-2,4-xylenol. Interfering chlorides are precipitated with silver sulfate and the nitrosylenol is extracted with hexane, concentrated, and injected. Nitrite in the filtrate is distilled at pH 5, collected in alkaline solution, and dried. The residue is oxidized to nitrate with permanganate in the presence of sulfuric acid, and then chromatographed in the same manner as nitrate. Recoveries from several foods were 83--100% for nitrate and 80--100% for nitrite. The limit of sensitivity was 0.1 ppm for both residues.
对2,4-二甲苯酚法进行了改进，开发了一种气液色谱（GLC）法，用于测定多种食品中的硝酸盐和亚硝酸盐。可使用火焰离子化（FID）检测器或电子捕获检测器（ECD）。用硫酸锌从温热的碱性水中去除蛋白质和脂肪，然后过滤。滤液蒸发至干，再用水重新溶解，并在硫酸存在下与2,4-二甲苯酚反应生成6-硝基-2,4-二甲苯酚。用硫酸银沉淀干扰性氯化物，并用己烷萃取亚硝基二甲苯酚，浓缩后注入。滤液中的亚硝酸盐在pH 5下蒸馏，收集在碱性溶液中并干燥。残留物在硫酸存在下用高锰酸钾氧化成硝酸盐，然后以与硝酸盐相同的方式进行色谱分析。几种食品中硝酸盐的回收率为83% - 100%，亚硝酸盐的回收率为80% - 100%。两种残留物的检测限均为0.1 ppm。
