A colorimetric assay for vanillin detection by determination of the luminescence of o-toluidine condensates

Vanillin (4-hydroxy-3-methoxybenzaldehyde), a food additive with rich milk flavor, is commonly used in the food, beverage and cosmetic industries. However, excessive consumption of vanillin may cause liver and kidney damage. Therefore, methods for detecting and controlling the level of vanillin in food, especially in infant powder, have important practical significance. In this study, we established a colorimetric assay for vanillin detection. The detection was performed under high-temperature and acidic conditions, which can induce the reaction of the aldehyde group of vanillin with the amino group of o-toluidine. The resulting product had a maximum absorption at 363 nm, which was quantified by a UV spectrophotometer. This assay had a limit of detection (LOD) of 1 pg mL−1 and a linear range between 1 μg mL−1 and 100 μg mL−1. The average recoveries at three spiked levels were in the range from 91.1% to 101.6% with a relative standard deviation (RSD) of 4.62% ~ 7.27%.香兰素（Vanillin，化学名4-羟基-3-甲氧基苯甲醛）是一种奶香浓郁的食品添加剂，广泛应用于食品、饮料及化妆品工业。但过量摄入香兰素可造成肝肾功能损伤，因此建立食品尤其是婴幼儿配方奶粉中香兰素的检测与管控方法，具备重要的现实意义。本研究建立了一种用于香兰素检测的比色分析法：检测过程在高温酸性条件下进行，可诱导香兰素的醛基与邻甲苯胺的氨基发生反应；反应产物在363 nm处具有最大吸收峰，通过紫外分光光度计完成定量分析。该方法的检测限（limit of detection, LOD）为1 pg·mL⁻¹，线性范围为1 μg·mL⁻¹至100 μg·mL⁻¹；在三个加标水平下的平均回收率为91.1%~101.6%，相对标准偏差（relative standard deviation, RSD）为4.62%~7.27%。