Looi Wen Donq, Chamand Laura, Brown Blake, Brajter-Toth Anna
Department of Chemistry, University of Florida , P.O. Box 117200, Gainesville, Florida 32611-7200, United States.
Faculty of Chemistry, University of Strasbourg , 1 Rue Blasie Pascal, 67008 Strasbourg, France.
Anal Chem. 2017 Jan 3;89(1):603-610. doi: 10.1021/acs.analchem.6b02406. Epub 2016 Dec 12.
The ionization of LS samples in desorption ionization mass spectrometry (LS DESI MS), supplied continuously through a LS interface separated in space from the spray emitter, was investigated in this work. The role of electrochemistry (EC) in the ionization process was addressed. The visual (observation) of the operation of the LS DESI MS system showed a thick spray plume generated by the electrosonic spray ionization (ESSI), forming a liquid cone at the LS interface. When the LS interface was grounded the cone collapsed and the MS ion signal was lost, indicating that the LS was carried to the MS inlet by the spray that emerged from the cone. Ion signals in a new in-line LS DESI MS system, in angled LS DESI MS, and in electrospray ionization (ESI) MS, which produced the most intense ion signals from methanol/water solutions, and in ESSI MS, of dopamine (DA), tyrosine (Tyr) and N,N-dimethyl-p-phenylenediamine (DMPA), were evaluated using methanol/water and aqueous (aq) solutions. In addition, the effect on ion signals of geometric parameters and the LS and the spray solution flow rates was tested in in-line LS DESI MS. Of the methods tested, the analysis of aq LS containing electrolytes was simplest by LS DESI MS. The signal intensity was higher in in-line than in angled LS DESI MS. In online electrochemistry (EC)/LS DESI MS, when 0 V was applied to the EC cell Tyr ion signal was detected only at low pH (2).
本研究对通过与喷雾发射器在空间上分离的液相色谱（LC）接口连续供应的液相色谱样品在解吸电离质谱（LC DESI MS）中的电离情况进行了研究。探讨了电化学（EC）在电离过程中的作用。对LC DESI MS系统运行的直观观察（观测）显示，电声喷雾电离（ESSI）产生了浓密的喷雾羽流，在LC接口处形成了一个液锥。当LC接口接地时，液锥坍塌，质谱离子信号消失，这表明液相色谱通过从液锥中喷出的喷雾被输送到质谱进样口。使用甲醇/水溶液和水溶液对新型在线LC DESI MS系统、倾斜式LC DESI MS、电喷雾电离（ESI）质谱（从甲醇/水溶液中产生最强离子信号）以及多巴胺（DA）、酪氨酸（Tyr）和N，N-二甲基对苯二胺（DMPA）的电声喷雾电离（ESSI）质谱中的离子信号进行了评估。此外，还在在线LC DESI MS中测试了几何参数、液相色谱和喷雾溶液流速对离子信号的影响。在所测试的方法中，通过LC DESI MS分析含电解质的水溶液最为简便。在线式LC DESI MS中的信号强度高于倾斜式LC DESI MS。在在线电化学（EC）/LC DESI MS中，当向EC池施加0 V电压时，仅在低pH值（2）下检测到Tyr离子信号。
