Development and characterization of a novel semiautomated arrangement for electrochemically assisted injection in combination with capillary electrophoresis time‐of‐flight mass spectrometry

Electrochemically assisted injection ( EAI ) is an attractive injection concept for CE that enables the separation of neutral analytes via electrochemical generation of charged species during the injection process. A new semiautomated EAI configuration was developed and applied in conjunction with CE ‐MS ( EAI ‐ CE ‐ MS ). The EAI cell arrangement consists of an integrated buffer reservoir for CE separations and a compartment holding screen‐printed electrodes. A drop of sample solution (50 μL) was sufficient to cover the three‐electrode structures. A piezo motor provided a fast and precise capillary positioning over the screen‐printed electrode assembly. Using ferrocene methanol as a model system, the EAI arrangement was characterized regarding coulometric efficiency, precision, and sensitivity of electrospray ionization‐time‐of‐flight‐ MS . The formation of the cationic oxidation product of ferrocene methanol enhanced the sensitivity of CE ‐ MS determination by two orders of magnitude and the electrochemically formed product showed a migration time corresponding to its individual electrophoretic mobility. Preliminary studies of EAI ‐ CE ‐ MS in the field of the analysis of nitroaromatic compounds were carried out. The formation of corresponding hydroxylamines and amines paved the way for selective and sensitive CE ‐ MS determinations without the need of adding surfactants to the electrophoresis buffer.