Sundström Mira, Pelander Anna, Ojanperä Ilkka
Department of Forensic Medicine, Faculty of Medicine, University of Helsinki, PO Box 40, 00014 Helsinki, Finland.
Forensic Toxicology Unit, National Institute for Health and Welfare, PO Box 30, 00271 Helsinki, Finland.
J Anal Toxicol. 2017 Sep 1;41(7):623-630. doi: 10.1093/jat/bkx044.
The current illicit drug scene, with its unpredictable appearance of new psychoactive substances, challenges drug-testing laboratories. Ultra-high performance liquid chromatography-high-resolution quadrupole time-of-flight mass spectrometry (UHPLC-HR-QTOFMS) provides an especially versatile analytical platform for responding to this continuous change. QTOFMS can be used to collect nonselective MS/MS by broadband data-independent acquisition (DIA), recording all product ions regardless of the precursor ion. Another approach is to collect selective MS/MS by data-dependent acquisition (DDA), using a narrow precursor mass window with preset criteria such as the presence of a particular ion among a precursor ion list. The present study compared methods based on these two modes of data acquisition on a single UHPLC-HR-QTOFMS instrument setup and using identical sample preparation. The DIA method relied on a post-targeted reverse database search and the DDA method on a spectrum library search, each comprising the same selection of 200 drugs of abuse. The performance between the methods was compared in terms of the limit of identification (LOI) and specificity. The median LOI of the DIA method (8 ng/mL) was lower than that of the DDA method (16 ng/mL). Among the 20 model compounds, a better LOI was obtained with DIA for 13 compounds. DIA was superior in resolving closely eluting and co-eluting isomeric and isobaric compounds. Comparison between the feasibility of DIA and DDA for casework was carried out by analyzing 50 authentic case urine samples. DIA produced 266 identifications involving 46 different substances, and DDA produced 225 identifications involving 42 substances. Moreover, substance identification by DIA was more straightforward and the method was easier to deploy in casework. Nonetheless, the DDA approach with substance-specific collision energies produced informative product ion spectra suitable for occasional confirmatory analyses.
当前非法药物领域，新精神活性物质不断出现且难以预测，这给毒品检测实验室带来了挑战。超高效液相色谱-高分辨率四极杆飞行时间质谱（UHPLC-HR-QTOFMS）为应对这种持续变化提供了一个特别通用的分析平台。QTOFMS可通过宽带数据非依赖采集（DIA）来收集非选择性MS/MS，记录所有产物离子而不考虑前体离子。另一种方法是通过数据依赖采集（DDA）收集选择性MS/MS，使用具有预设标准（如前体离子列表中特定离子的存在）的窄前体质量窗口。本研究在单一UHPLC-HR-QTOFMS仪器设置下并使用相同的样品制备方法，比较了基于这两种数据采集模式的方法。DIA方法依赖于靶向后反向数据库搜索，DDA方法依赖于光谱库搜索，每种方法都包含相同的200种滥用药物选择。在鉴定限（LOI）和特异性方面比较了这些方法之间的性能。DIA方法的中位LOI（8 ng/mL）低于DDA方法（16 ng/mL）。在20种模型化合物中，DIA对13种化合物获得了更好的LOI。DIA在分离紧密洗脱和共洗脱的异构体和等压化合物方面更具优势。通过分析50份真实案件尿液样本，比较了DIA和DDA在实际案件中的可行性。DIA产生了266次鉴定，涉及46种不同物质，DDA产生了225次鉴定，涉及42种物质。此外，DIA进行的物质鉴定更直接，该方法在实际案件中更易于应用。尽管如此，采用物质特异性碰撞能量的DDA方法产生了适用于偶尔确证分析的信息丰富的产物离子光谱。
