This paper discusses continued studies and new analytical applications of a recently developed three-electrode controlled-potential electrochemical cell incorporated into an electrospray ion source (Van Berkel, G. J.; Asano, K. G.; Granger, M. C. Anal. Chem. 2004, 76, 1493−1499.). This cell contains a porous flow-through working electrode (i.e., the emitter electrode) with high surface area and auxiliary electrodes with small total surface area that are incorporated into the emitter electrode circuit to control the electrochemical reactions of analytes in the electrospray emitter. The current at the working and auxiliary electrodes, and current at the grounding points upstream and downstream of the emitter in the electrospray circuit, were recorded in this study, along with the respective mass spectra of model compound reserpine, under various operating conditions to better understand the electrochemical and electrospray operation of this emitter cell. In addition to the ability to control analyte oxidation in positive ion mode (or reduction in negative ion mode) in the electrospray emitter, this emitter cell system was shown to provide the ability to efficiently reduce analytes in positive ion mode and oxidize analytes in negative ion mode. This was demonstrated by the reduction of methylene blue in positive ion mode and oxidation of 3,4-dihydroxybenzoic acid in negative ion mode. Also, the ability to control electrochemical reactions via potential control was used to selectively ionize (oxidize) analytes with different standard electrochemical potentials within mixtures to different charge states to overcome overlapping molecular ion isotopic clusters. The analytical benefit of this ability was illustrated using a mixture of nickel and cobalt octaethylporphyrin.
本文讨论了最新开发的三电极受控电位电
化学电池与电喷雾离子源相结合的持续研究和新的分析应用(Van Berkel, G. J.; Asano, K. G.; Granger, M. C. Anal.Chem.2004, 76, 1493-1499.).该样品池包含一个高表面积的多孔流动工作电极(即发射器电极)和一个总表面积较小的辅助电极,后者被纳入发射器电极电路,用于控制电喷雾发射器中分析物的电
化学反应。本研究记录了工作电极和辅助电极的电流,以及电喷雾电路中发射器上游和下游接地点的电流,同时还记录了模型化合物瑞瑟平在各种操作条件下的相应质谱,以便更好地了解该发射器样品池的电
化学和电喷雾操作。除了能够在电喷雾发射器中控制正离子模式下的分析物氧化(或负离子模式下的分析物还原)外,该发射池系统还具有在正离子模式下有效还原分析物和在负离子模式下氧化分析物的能力。
亚甲基蓝在正离子模式下被还原,3,4-二羟基
苯甲酸在负离子模式下被氧化就证明了这一点。此外,通过电位控制电
化学反应的能力还被用于选择性地电离(氧化)混合物中具有不同标准电
化学电位的分析物,使其处于不同的电荷状态,以克服分子离子同位素簇的重叠。使用八乙基
卟啉镍钴混合物说明了这种能力的分析优势。