Abstract：
In the multiclass, multiresidue analysis of pesticides in food and environmental samples, pyrethroid insecticides are generally more difficult to analyze than other types of analytes. They do not ionize well by electrospray ionization, and although they are suitable for analysis by gas chromatography-mass spectrometry (GC-MS), selectivity using standard electron ionization (EI) in GC-MS is often insufficient because the molecular ion is rarely present. Many pyrethroids tend to have the same fragment ions in MS or high-resolution (HR)MS, and similar ion transitions in tandem MS/MS, leading to difficulties in distinguishing different pyrethroids from each other and chemical interferences in complex matrices. In this study, different forms of fast GC coupled with different types of MS detectors were compared for the analysis of up to 15 pyrethroids in barley extracts as a test case to assess which approach was the most advantageous. The three studied GC-MS techniques consisted of Cold EI using supersonic molecular beams in selected ion monitoring (SIM) mode with a single quadrupole instrument; triple quadrupole MS/MS; and HRMS using an orbital ion trap (orbitrap). A higher flow rate was used in Cold EI, and low pressure (LP) GC was employed in the MS/MS and orbitrap methods, to speed up the GC analyses (<10 min chromatograms in all cases). Each technique had some advantages over the others depending on specific pyrethroid analytes in the matrix. Nontargeted LPGC-orbitrap typically yielded the highest selectivity, but it rarely achieved the needed detectability to quantidentify the residues at 10 ng g-1. Cold EI-SIM and LPGC-MS/MS usually met the needed detection limits and generally achieved similar capabilities for the targeted pyrethroids.
摘要：
在多类中，食品和环境样品中农药的多残留分析，拟除虫菊酯杀虫剂通常比其他类型的分析物更难以分析。它们通过电喷雾电离不能很好地电离，尽管它们适合通过气相色谱-质谱（GC-MS）进行分析，在GC-MS中使用标准电子电离(EI)的选择性通常不足,因为分子离子很少存在。许多拟除虫菊酯在MS或高分辨率（HR）MS中倾向于具有相同的碎片离子，以及串联MS/MS中类似的离子跃迁，导致难以区分不同的拟除虫菊酯和复杂基质中的化学干扰。在这项研究中,比较了不同形式的快速GC与不同类型的MS检测器，以分析大麦提取物中多达15种拟除虫菊酯，以评估哪种方法最有利。研究的三种GC-MS技术包括使用单个四极子仪器在选定的离子监测（SIM）模式下使用超音速分子束的ColdEI；三重四极MS/MS;和使用轨道离子阱（轨道阱）的HRMS。在冷EI中使用了更高的流速，在MS/MS和轨道阱方法中采用了低压（LP）GC，以加速GC分析（在所有情况下<10分钟色谱图）。取决于基质中特定的拟除虫菊酯分析物，每种技术都比其他技术具有一些优势。非靶向LPGC-orbitrap通常产生最高的选择性，但是它很少达到定量10ngg-1的残留物所需的可检测性。冷EI-SIM和LPGC-MS/MS通常满足所需的检测限，并且通常实现了目标拟除虫菊酯的类似能力。
