Development of Novel Dual-Electrochemical Techniques for Capillary Electrophoresis by Means of Dead-Volume Free Flow Splitting

The combination of capillary electrophoresis (CE) and electrochemistry, commonly in the form of amperometric detection (AD), has gained increasing importance by providing good selectivity, stability, and detection performance, especially when combined with non-aqueous media (NACE-AD). Despite these advantages, conventional NACE-AD systems face limitations when analyzing complex samples, being confronted with co-migrating analytes or the need for oxidative and reductive information at the same time. Established techniques for simultaneous oxidative and reductive detection often rely on complex electrode arrays, which are not able to provide completely independent electrode processes while posing complex electrochemical systems. To address these issues, a dual-detection concept (DDC) relying on dead-volume free flow splitting combined with two independent AD cells (CE-AD2) could provide a user-friendly alternative to existing approaches, avoiding most of these problems and giving new opportunities for method development. Moreover, dead-volume free flow splitting also allows other destructive, electroanalytical methods to be combined with CE-AD, e.g., voltammetry. The combination with linear-sweep voltammetry (LSV) offers a versatile tool for online identification of various analytes by their characteristic voltammogram (qualitative information) while using AD for quantitative information (CE-AD/LSV). This work presents two novel electrochemical DDCs for NACE using newly designed, synchronized, independent AD cells connected via a commercially available flow splitter. The first DDC, CE-AD2, simultaneously detects oxidizable and reducible species using independently optimized electrodes (platinum for oxidation and silver for reduction) and detection potentials within a single measurement run. The second approach, CE-AD/LSV, combines sensitive fixed-potential AD for quantification with LSV for online analyte identification. Together, these systems could improve flexibility, selectivity, and analytical performance for monitoring complex samples in NACE applications.