Suddendorf R F, Wright S K, Boyer K W
J Assoc Off Anal Chem. 1981 May;64(3):657-60.
A method is presented for improving within-can homogeneity and simplifying the determination of lead in canned foods. The entire content of a canned food product is blended with 2N HNO3 and allowed to stand 16 h; then the sample is again blended and a subsample is taken. The subsample is digested by wet ashing using nitric acid-perchloric acid or nitric acid-sulfuric acid-hydrogen peroxide. The pH of the sample is adjusted with ammonium hydroxide, and the lead is extracted into butyl acetate as the pyrrolidinecarbodithioate complex. Lead concentration is determined by flame atomic absorption spectrometry. Recoveries of lead ranged from 92 to 104% for added 100-mesh lead particulate. Within-sample variability for green beans was reduced from 37% obtained with blending alone to 3.7% using the proposed procedure at the 3.1 micrograms/g added lead level. Variability was 7.6% at the 0.68 microgram/g level and 16.4% at the 0.20 microgram/g level of added lead. The use of nitric acid-sulfuric acid-hydrogen peroxide for digestion has the advantage of not forming a precipitate during the neutralization step, as occurs when nitric acid-perchloric acid is used for dissolution.
本文介绍了一种提高罐装食品罐内均匀性并简化铅测定的方法。将罐装食品的全部内容物与2N硝酸混合，放置16小时；然后再次混合样品并取子样品。子样品通过用硝酸 - 高氯酸或硝酸 - 硫酸 - 过氧化氢进行湿式灰化消化。用氢氧化铵调节样品的pH值，铅以吡咯烷二硫代氨基甲酸盐络合物的形式萃取到乙酸丁酯中。通过火焰原子吸收光谱法测定铅浓度。对于添加的100目铅颗粒，铅的回收率在92%至104%之间。在添加铅水平为3.1微克/克时，使用所提出的方法，绿豆样品内的变异性从单独混合时的37%降低到3.7%。在添加铅水平为0.68微克/克时，变异性为7.6%，在添加铅水平为0.20微克/克时，变异性为16.4%。使用硝酸 - 硫酸 - 过氧化氢进行消化的优点是在中和步骤中不会像使用硝酸 - 高氯酸进行溶解时那样形成沉淀。
