On-Line Electrochemical/LC-MS Techniques for Profiling and Characterizing Metabolites and Reactive Species

摘要

>RP-63Oxidation is an important aspect of metabolism and in the formation of chemically reactive intermediates, which may be associated with toxicity. In vitro and in vivo biological systems provide useful insight at various stages. However, significant challenges remain in detecting, identifying and characterizing drug metabolites. Several studies have shown that electrochemical (EC) techniques can be used to produce species that correspond to enzymatic and non-enzymatic oxidations relevant to biological metabolism and toxicity. In this study, EC flow cells were used in a number of configurations in combination with mass spectrometry (EC-MS) including flow injection EC-MS, pre-column EC-LC-MS, and ‘EC-synthesis’ to generate product in sufficient quantities to perform more in-depth structural elucidation experiments (e.g. by NMR). Of the possible flow cell designs, coulometric cells with porous flow-through working electrodes (WE) were chosen. The high surface area (for a given volume) of the micro-porous flow-through WE allows more efficient electrolysis (typically >20-fold at 1.0mL/min) than cells that utilize a planar WE (e.g., wall-jet and thin-layer). The advantages of the coulometric design have been widely demonstrated in the context of LC-EC detection and include much higher and more reproducible signal and lower susceptibility to fouling. These characteristics are also important when considering their use as on-line reaction devices, since higher and more reproducible product yields can be obtained over a wider range of flow rates and on a more routine basis. Coulometric cells can also be used more readily at high pressure (e.g., in pre-column and serial detector configurations), thus allowing greater flexibility in experimental design.