Kern Sara E, Lin Lora A, Fricke Frederick L
U.S. Food and Drug Administration, Forensic Chemistry Center, 6751 Steger Drive, Cincinnati, OH, 45237, USA,
J Am Soc Mass Spectrom. 2014 Aug;25(8):1482-8. doi: 10.1007/s13361-014-0912-1. Epub 2014 May 21.
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.
几十年来，美国的食品进口一直在稳步增长，这加剧了对快速且灵敏的筛查技术的需求。现已开发出一种利用泡沫盘对进口农产品表面进行采样的方法。这项工作为使用液相色谱 - 质谱联用系统（LCMS）收集的大量已发表的农药碎片数据提供了补充信息（萨克等人，《农业与食品化学杂志》，59卷，6383 - 6411页，2011年；莫尔等人，《分析与生物分析化学》，403卷，2891 - 2908页，2012年）。这些泡沫盘通过与高分辨率精确质量质谱仪（HRAM - MS）联用的透射模式实时直接分析（DART）常压解吸电离进行直接分析。为了在鉴定所检测到的农药时提供更高的确定性，已建立了一个精确质量碎片和质子化母分子离子（[M + H]⁺）同位素的库。HRAM - MS配备了四极杆质量过滤器，具备“数据依赖型”碎裂能力，与“全离子”碎裂（所有离子进入碰撞室并同时碎裂）不同。采用DART氦气流的温度梯度和多种碰撞能量来检测和碎裂164种不同化学类别、大小和极性的农药。前体离子（[M + H]⁺离子）和碎片离子的精确质量信息对于正确识别进口农产品表面的化学污染物至关重要。此外，数据库中包含[M + H]⁺的同位素为确认过程增添了另一项指标。碎裂数据是使用Q - Exactive质谱仪收集的，并被添加到一个用于处理用Exactive质谱仪收集的数据的数据库中，Exactive质谱仪是一种更便于用于此筛查应用的仪器。所研究的商品范围从苹果等表皮光滑的农产品到西兰花等表面较粗糙的农产品。最少的样品制备和无需色谱分析将每个样品的分析时间缩短至约15分钟，并且该技术的简单性和稳健性使其成为快速筛查的理想选择。
