为婴幼儿配方食品的保质期量化指标提供准确的定量手段,进行了题示项目研究。称取样品约2.0 g,加入10.0 mL衍生液[体积比为1∶1的0.5 g·L^-1 2,4-二硝基苯肼的乙腈溶液-磷酸盐缓冲溶液(pH 5)的混合液]和5.0 mL乙腈饱和的正己烷溶液,混匀,离心;取下层溶液置于60℃水浴中反应1 h,加入5 g硫酸铵,静置5 min,再加入5.0 mL环己烷,涡旋1 min,离心;取上清液,用约1.0 g无水硫酸钠干燥,采用气相色谱法进行分析。结果显示:苯甲醛、2,4-壬二烯醛、2-十一烯醛、1-壬醛的质量在10 μg以内与其对应的峰面积呈线性关系,检出限(3S/N)为0.05~0.1 mg·kg^-1;对空白样品进行加标回收试验,4种醛类化合物的回收率为85.0%~95.4%,测定值的相对标准偏差(n=6)均小于10%。方法用于分析敞开放置一段时间的婴幼儿配方食品,当放置时间超过21 d,随着时间的延长,4种目标物的含量逐渐增加。

In order to provide accurate quantitative means for the shelf life index of infant formula, the work as mentioned by the article was carried out. The sample (about 2.0 g) was taken, and 10.0 mL of derivative solution ［a mixture of 0.5 g·L^-1 of 2,4-dinitrophenylhydrazine acetonitrile solution and phosphate buffer solution (pH 5) at volume ratio of 1∶1］ and 5.0 mL of acetonitrile-saturated n-hexane solution were added. After mixing well and centrifugation, the lower solution was placed in a water bath at 60 ℃ to react for 1 h, and 5 g of ammonium sulfate was added to settle for 5 min, then 5.0 mL of cyclohexane was added to vortex for 1 min. After centrifugation, the supernatant was taken and dried with about 1.0 g of anhydrous sodium sulfate for gas chromatography analysis. It was shown that linear relationships between values of mass of benzaldehyde, 2,4-nonadienal, 2-undecanonal and 1-nonanal and their peak areas were kept within 10 μg, with detection limits (3S/N) in the range of 0.05-0.1 mg·kg^-1. Test for recovery was made on blank sample, giving values of recovery in the range of 85.0%-95.4%, and RSDs (n=6) of the determined values less than 10%. This method has been applied to the analysis of infant formula stored open for a period of time. When the infant formula was stored open for more than 21 d, the contents of 4 characteristic aldehyde compounds gradually increased with the extension of time.