Department of Chemistry, The Hong Kong University of Science and Technology , Clear Water Bay, Kowloon, Hong Kong SAR.
J Agric Food Chem. 2013 Jun 19;61(24):5758-63. doi: 10.1021/jf401446n. Epub 2013 Jun 7.
Food irradiation is a common preservation method that is used in many countries. The ability to identify irradiated food is important for assuring compliance with regulatory policies, such as food labeling requirements, and for informed consumer choice. There is thus a significant demand for analytical methods of high sensitivity and selectivity to identify irradiated food, especially for foods subjected to low-dose irradiation and for processed or composite foods that contain small quantities of irradiated ingredients. 2-Alkylcyclobutanones (2-ACBs) are uniquely formed during food irradiation and have been adopted by the European Committee for Standardization as signature biomarkers for the identification of irradiated foods. We now report the development of a novel assay for quantification of 2-ACBs in γ-irradiated food by liquid extraction of fat content followed by precolumn derivatization and liquid chromatography-tandem mass spectrometric (LC-MS/MS) detection. Precolumn derivatization with hydroxylamine introduced a polar functional group into the otherwise nonpolar 2-ACBs, which greatly enhanced ESI-MS response. The method was validated for extraction efficiency, precision, accuracy, and detection limit. In comparison with the current GC-MS based European official method (EN1785:2003) for 2-ACBs determination, our new LC-MS/MS method offers a more efficient sample processing protocol with reduced solvent consumption. More importantly, the combination of chemical derivatization and LC-MS/MS detection significantly enhanced the analytical sensitivity of the method, which allows confident identification of food irradiated with as little as 10 Gy. To the best of our knowledge, this is the first report of 2-ACB determination by LC-MS/MS and the first analytical method allowing confident identification of irradiated food at dosage of down to 10 Gy.
食品辐照是一种常见的保鲜方法，许多国家都在使用。能够识别辐照食品对于确保符合监管政策（如食品标签要求）以及消费者知情选择非常重要。因此，对于具有高灵敏度和选择性的分析方法来识别辐照食品的需求非常大，特别是对于低剂量辐照的食品和含有少量辐照成分的加工或复合食品。2-烷基环丁酮（2-ACBs）是食品辐照过程中特有的产物，已被欧洲标准化委员会采用为识别辐照食品的特征生物标志物。我们现在报告了一种通过液体提取脂肪含量，然后进行柱前衍生化和液相色谱-串联质谱（LC-MS/MS）检测来定量辐照食品中 2-ACBs 的新方法。用羟胺进行柱前衍生化在非极性 2-ACBs 中引入了一个极性官能团，这极大地增强了 ESI-MS 的响应。该方法经过了提取效率、精密度、准确度和检测限的验证。与当前基于 GC-MS 的欧洲官方方法（EN1785:2003）相比，我们的新 LC-MS/MS 方法提供了更有效的样品处理方案，减少了溶剂消耗。更重要的是，化学衍生化和 LC-MS/MS 检测的结合大大提高了方法的分析灵敏度，使得能够自信地识别辐照剂量低至 10Gy 的食品。据我们所知，这是首次报道通过 LC-MS/MS 测定 2-ACB，也是首次报道能够在 10Gy 以下剂量下自信地识别辐照食品的分析方法。
