We explored the use of pulsed flow modulation (PFM) two-dimensional comprehensive gas chromatography (GCxGC) mass spectrometry with supersonic molecular beams (SMB) (also named Cold electron ionization (EI)) for achieving universal pesticide analysis in agricultural products. The use of GCxGC serves as an alternative to MS-MS in the needed reduction of matrix interference while enabling full-scan MS operation for universal pesticide analysis with reduced number of false negatives. Matrix interference is further reduced with Cold EI in view of the enhancement of the molecular ions. Pulsed flow modulation is a simple GCxGC modulator that does not consume cryogenic gases while providing tuneable second GCxGC column injection time for enabling the use of quadrupole-based mass spectrometry regardless its limited scanning speed. PFM-GCxGC-MS with Cold EI combines improved separation of GCxGC with Cold EI benefits of tailing-free ultra-fast ion source response time and enhanced molecular ions for the provision of increased sample identification information and reduced matrix interference. Consequently, PFM GCxGC-MS with Cold EI also improved NIST library identification probabilities of the spiked pesticides. PFM GCxGC is further characterized by largely increased second column sample and matrix capacity that as a result performs much better than thermal modulation GCxGC-MS with standard EI in the suppression of matrix interference. In a comparison with standard GC-MS, we measured with PFM GCxGC-MS with Cold EI an average total ion count matrix interference reduction factor of 32 for 12 pesticides in two matrices of baby leaves mixture and lettuce. In addition, Cold EI further increases the range of pesticides amenable for GC-MS analysis and its response is relatively uniform hence with it the need for pesticides specific calibration is reduced.

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我们探索了使用脉冲流调制（PFM）二维综合气相色谱（GCxGC）质谱与超音速分子束（SMB）（也称为冷电子电离（EI））来实现农产品中通用农药分析的方法。GCxGC的使用可作为MS-MS的替代方法，从而减少了基质干扰，同时实现了全扫描MS操作，可进行通用农药分析，并减少了假阴性数。考虑到分子离子的增强，使用Cold EI可以进一步降低基体干扰。脉冲流调制是一种简单的GCxGC调制器，它不消耗低温气体，同时提供了可调整的第二GCxGC色谱柱进样时间，无论扫描速度如何，均可使用基于四极杆的质谱仪。带有Cold EI的PFM-GCxGC-MS结合了GCxGC的改进分离和Cold EI的优点，即无拖尾的超快离子源响应时间和增强的分子离子，从而提供了更多的样品鉴定信息和减少的基质干扰。因此，具有Cold EI的PFM GCxGC-MS还提高了加标农药的NIST库鉴定概率。PFM GCxGC的特征还在于大大提高了第二色谱柱样品和基质的容量，因此，在抑制基质干扰方面，其性能要比标准EI的热调制GCxGC-MS好得多。在与标准GC-MS的比较中，我们使用带有Cold EI的PFM GCxGC-MS测量了两种母叶混合物和生菜中12种农药的平均总离子计数矩阵干扰降低因子为32。此外，

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