Narváez Alfonso, Gámiz-Gracia Laura, García-Campaña Ana M, Hernández-Mesa Maykel
Department of Analytical Chemistry, Faculty of Sciences, University of Granada; Department of Preventive Medicine and Public Health, Food Science, Toxicology and Forensic Medicine, Faculty of Pharmacy and Food Science, University of Valencia.
Department of Analytical Chemistry, Faculty of Sciences, University of Granada.
J Vis Exp. 2024 Nov 22(213). doi: 10.3791/67484.
Ion mobility mass spectrometry (IMS) acts as an additional separation dimension when integrated into liquid chromatography-mass spectrometry (LC-MS) workflows. LC-IMS-MS methods provide higher peak resolution, enhanced separation of isobaric and isomeric compounds, and improved signal-to-noise ratio (S/N) compared to traditional LC-MS methods. IMS provides another molecular characteristic for the identification of analytes, namely the collision cross section (CCS) parameter, reducing false positive results. Therefore, LC-IMS-MS methods address important analytical challenges in the field of food safety (i.e., detection of compounds at trace levels in complex food matrices and unambiguous identification of isobaric and isomeric molecules). Ergot alkaloids (EAs) are a family of mycotoxins produced by fungi that attack a wide variety of grass species, including small grains such as rye, triticale, wheat, barley, millet, and oats. Maximum levels (MLs) of these mycotoxins have been established in several foodstuffs, as detailed in the Commission Regulation EC/2023/915. This new legislation includes six main EAs and their corresponding epimers, so an efficient methodology is required to properly distinguish these isomeric molecules considering their co-occurrence. Therefore, the goal of this protocol is to show how the integration of IMS in LC-MS workflows contributes to the separation of isomeric EAs, enhancing the selectivity of the analytical method. Additionally, it illustrates how the generation of CCS libraries through the characterization of analytical standards provides higher confidence for the identification of mycotoxins. This protocol is designed to clearly explain the benefits of implementing IMS in food safety, taking as an example the determination of EAs in cereals. A QuEChERS-based extraction followed by an LC-trapped ion mobility spectrometry (TIMS)-MS analysis provided limits of quantification ranging from 0.65 to 2.6 ng/g with acceptable accuracy (although low recovery for ergotaminine) at 1.5x, 1x, and 0.5x the ML and exhibited a negligible matrix effect.
离子淌度质谱（IMS）与液相色谱 - 质谱（LC - MS）工作流程相结合时，可作为一种额外的分离维度。与传统的LC - MS方法相比，LC - IMS - MS方法具有更高的峰分辨率、对等压和同分异构体化合物的分离能力增强以及信噪比（S/N）提高等优点。IMS为分析物的鉴定提供了另一个分子特征，即碰撞截面（CCS）参数，减少了假阳性结果。因此，LC - IMS - MS方法解决了食品安全领域的重要分析挑战（即在复杂食品基质中痕量水平化合物的检测以及对等压和同分异构体分子的明确鉴定）。麦角生物碱（EAs）是一类由真菌产生的霉菌毒素，可侵袭多种禾本科植物，包括黑麦、小黑麦、小麦、大麦、小米和燕麦等小谷物。如欧盟委员会法规EC/2023/915中详细规定，已在多种食品中设定了这些霉菌毒素的最大限量（MLs）。这项新法规涵盖六种主要的EAs及其相应的差向异构体，因此需要一种有效的方法来妥善区分这些同分异构体分子，考虑到它们的共存情况。因此，本方案的目标是展示IMS在LC - MS工作流程中的整合如何有助于同分异构体EAs的分离，提高分析方法的选择性。此外，它还说明了通过分析标准品的表征生成CCS库如何为霉菌毒素的鉴定提供更高的可信度。本方案旨在清晰解释在食品安全中实施IMS的益处，以谷物中EAs的测定为例。基于QuEChERS的提取方法，随后进行LC - 阱式离子淌度光谱（TIMS） - MS分析，在ML的1.5倍、1倍和0.5倍浓度下，定量限范围为0.65至2.6 ng/g，具有可接受的准确度（尽管麦角胺的回收率较低），且基质效应可忽略不计。
