同轴式电化学电喷雾质谱离子源研究蒽电化学衍生十二胺(英文)

Online Electrochemistry/Electrospray Mass Spectrometry with a Coaxial Probe for Investigation of Electrochemical Derivatization of Anthracene with Dodecylamine

提出一种同轴式电化学电喷雾质谱离子源,用于电化学与质谱分析在线联用.离子源结构简单,造价低廉,容易制作.离子源内的电化学反应器工作在两电极模式,利用自制的悬浮在电喷雾高压上的无线电化学工作站控制.使用二苯基蒽或三乙胺的乙腈溶液作为分析物,全面测试了离子源的性能,包括电势控制精度、电化学转化率、响应时间和抗污能力等.测试溶液添加浓度约10mmo.lL-1的银盐作为电解质和去极剂,将溶液电阻降至250Ω,提高了在线联用的电势控制精度.所测二苯基蒽溶液流动时的伏安曲线与常规三电极体系的循环伏安曲线基本一致.在3.6μL.min-1的流速下,离子源的响应时间不超过5s,三乙胺的电化学转化率高达77%.利用此离子源,研究了蒽的电化学衍生反应,衍生试剂为十二胺.蒽作为一种非极性物质,不能为常规电喷雾质谱检测.而利用电化学电喷雾质谱离子源,蒽首先发生电化学氧化反应,进而与衍生试剂作用生成各种极性物质,被电喷雾质谱检测.依据质谱检测到的主要反应产物的相对分子质量与结构提出了衍生反应的机理,有助于理解蒽的复杂电化学行为.

In the present study, a coaxial probe was used for online electrochemistry/electrospray mass spectrometry （EC/ES-MS）. The probe can be constructed quickly using readily available materials at low cost. A wireless potentiostat floating at the electrospray high voltage was used to control the probe in a two-electrode configuration. Using an acetonitrile solution containing diphenylanthracene or triethylamine, we examined the performances of the probe, including the accuracy of potential control, the conversion efficiency, the response time, and the tolerance to fouling. A silver（I） salt solution （10 mmol·L-1） in acetonitrile was used as the electrolyte and depolarizer. This decreased the solution resistance of the probe to approximately 250 Ω and enabled precise potential control during online operations. Good correspondence was observed between the hydrodynamic and cyclic voltammograms of diphenylanthracene. At 3.6 μL·min-1, the response time of the probe was as low as 5 s and the conversion efficiency for triethylamine was 77%. Using the coaxial probe, we investigated the electrochemical derivatization of anthracene with dodecylamine. As a non-polar compound, anthracene usually cannot be detected by ES-MS. However, with the EC/ES-MS, the anthracene was first oxidized electrochemically, and then derivatized online by reactions with dodecylamine. The derivatization produced polar compounds that appeared in the ES-MS in high abundance. The products were identified and the reaction mechanism was elucidated. The results provide insight into the complex electrochemical behavior of anthracene.