Accurate Mass Fragment Library for Rapid Analysis of Pesticides on Produce Using Ambient Pressure Desorption Ionization with High-Resolution Mass Spectrometry
使用原位电离 DART-MS 高分辨质谱技术并对照精确质量片段库来快速分析农产品中的农药
Sara E. Kern, Lora A. Lin, Frederick L. Fricke
U.S. Food and Drug Administration, Forensic Chemistry Center, 6751 Steger Drive, Cincinnati, OH, 45237, USA
J．AM. Soc. Mass Spectrom., pp. 1-7, May 2014
Abstract:
U.S. food imports have been increasing steadily for decades, intensifying the need for a rapid and sensitive screening technique. A method has been developed that uses foam disks to sample the surface of incoming produce. This work provides complimentary information to the extensive amount of published pesticide fragmentation data collected using LCMS systems (Sack et al. Journal of Agricultural and Food Chemistry, 59, 6383-6411, 2011; Mol et al. Analytical and Bioanalytical Chemistry, 403, 2891-2908, 2012). The disks are directly analyzed using transmission-mode direct analysis in real time (DART) ambient pressure desorption ionization coupled to a high resolution accurate mass-mass spectrometer (HRAM-MS). In order to provide more certainty in the identification of the pesticides detected, a library of accurate mass fragments and isotopes of the protonated parent molecular ion (the [M+H]+) has been developed. The HRAM-MS is equipped with a quadrupole mass filter, providing the capability of "data-dependent" fragmentation, as opposed to "all -ion" fragmentation (where all of the ions enter a collision chamber and are fragmented at once). A temperature gradient for the DART helium stream and multiple collision energies were employed to detect and fragment 164 pesticides of varying chemical classes, sizes, and polarities. The accurate mass information of precursor ([M+H]+ ion) and fragment ions is essential in correctly identifying chemical contaminants on the surface of imported produce. Additionally, the inclusion of isotopes of the [M+H]+ in the database adds another metric to the confirmation process. The fragmentation data were collected using a Q-Exactive mass spectrometer and were added to a database used to process data collected with an Exactive mass spectrometer, an instrument that is more readily available for this screening application. The commodities investigated range from smooth-skinned produce such as apples to rougher surfaces like broccoli. The minimal sample preparation and absence of chromatography has shortened the analysis time to about 15 min per sample, and the simplicity and robustness of the technique make it ideal for rapid screening.
摘要：
近数十年来美国国内进口食品的数量呈逐年稳步增长的趋势，相对应地，对于能用于快速灵敏地筛查与确认的分析技术的渴求也也愈来愈强烈。我们报告一种利用泡沫（海绵）片对入口农产品进行表面采样并随即利用 DART-MS 快速分析和确证的方法。该方法提供了和已发表的含有大量的以 LCMS 系统收集到的农药质谱裂解碎片数据（Sack et al. Journal of Agricultural and Food Chemistry, 59, 6383-6411, 2011; Mol et al. Analytical and Bioanalytical Chemistry, 403, 2891-2908, 2012）补充性的结果。泡沫（海绵）片直接以透过式模块载样输送至 DART-高分辨质谱仪进行直接分析。为了更确切地鉴定农药，我们建立了质子化母离子 [M+H]+ 的精确质量和同位素比例数据库。该 HRAM（高分辨高质量精度）质谱配备四极杆质量过滤器，拥有“数据敲定（data-dependent）“的碰撞活化裂解能力。该能力 和“所有离子all -ion”裂解（所有的离子进入碰撞室后同时裂解）的质谱法有所不同。利用 DART 用氦气的温度梯度及质谱仪的多种碰撞活化能量，可以检测并裂解164种不同种类、不同大小和极性的化学农药。前体母离子和碎片离子的精确质量信息对于识别进口农产品表面化学污染物至关重要。此外，数据库中的母离子的同位素信息则提供了另一个衡量标准来进一步加以识别。碎片数据的收集通过 Q-Exactive 型号的质谱来完成，之后添加到早先采用 Exactive 型号的质谱仪收集建立的数据库当中。后者Exactive为较低端的型号，在普通筛查实验室更容易配置。商品筛查的范围非常广泛，既有果皮光滑的产品如苹果，又有表面粗糙的品种如花菜。极少量或者几乎不需要的样品制备、和无需色谱分离的特性，使该技术将每个样品的分析周期大大缩短到了只有15分钟，其简单、稳定和实用的特性非常适用于快速筛查的目的。
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