Department of Analytical Chemistry, University of Barcelona, Diagonal 645, 08028, Barcelona, Spain.
J Mass Spectrom. 2013 Nov;48(11):1241-51. doi: 10.1002/jms.3287.
In this work, the mass spectrometry behaviour of the veterinary drug family of phenicols, including chloramphenicol (CAP) and its related compounds thiamphenicol (TAP), florfenicol (FF) and FF amine (FFA), was studied. Several atmospheric pressure ionization sources, electrospray (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization were compared. In all atmospheric pressure ionization sources, CAP, TAP and FF were ionized in both positive and negative modes; while for the metabolite FFA, only positive ionization was possible. In general, in positive mode, M + H dominated the mass spectrum for FFA, while the other compounds, CAP, TAP and FF, with lower proton affinity showed intense adducts with species present in the mobile phase. In negative mode, ESI and atmospheric pressure photoionization showed the deprotonated molecule M-H, while atmospheric pressure chemical ionization provided the radical molecular ion by electron capture. All these ions were characterized by tandem mass spectrometry using the combined information obtained by multistage mass spectrometry and high-resolution mass spectrometry in a quadrupole-Orbitrap instrument. In general, the fragmentation occurred via cyclization and losses or fragmentation of the N-(alkyl)acetamide group, and common fragmentation pathways were established for this family of compounds. A new chemical structure for the product ion at m/z 257 for CAP, on the basis of the MS(3) and MS(4) spectra is proposed. Thermally assisted ESI and selected reaction monitoring are proposed for the determination of these compounds by ultra high-performance liquid chromatography coupled to tandem mass spectrometry, achieving instrumental detection limits down to 0.1 pg.
在这项工作中，研究了兽医用酚类药物家族，包括氯霉素（CAP）及其相关化合物丁胺卡那霉素（TAP）、氟苯尼考（FF）和 FF 胺（FFA）的质谱行为。比较了几种大气压电离源，包括电喷雾（ESI）、大气压化学电离（APCI）和大气压光电离（APPI）。在所有大气压电离源中，CAP、TAP 和 FF 均可在正、负离子模式下电离；而对于代谢物 FFA，仅可进行正离子化。一般来说，在正离子模式下，M + H是 FFA 质谱的主要离子，而其他化合物，如 CAP、TAP 和 FF，由于质子亲和力较低，与流动相中存在的物质形成强烈的加合物。在负离子模式下，ESI 和大气压光电离显示出去质子化分子M-H，而大气压化学电离则通过电子捕获提供自由基分子离子。所有这些离子均通过串联质谱法进行鉴定，串联质谱法使用多级质谱和四极杆-Orbitrap 仪器中的高分辨率质谱获得的组合信息。一般来说，通过 N-(烷基)乙酰胺基团的环化和损失或断裂发生碎裂，为该类化合物建立了常见的碎裂途径。基于 MS(3)和 MS(4)谱，提出了 CAP 产物离子 m/z 257 的新化学结构。提出了热辅助 ESI 和选择反应监测，用于通过超高效液相色谱-串联质谱法测定这些化合物，实现了仪器检测限低至 0.1 pg。
