Non‐aqueous electrophoresis on microchips: a review

The use of organic solvents as electrolytic medium in electrophoresis has become an important alternative for the analysis of compounds that exhibit low or no solubility in water. In recent years, nonaqueous electrophoresis has been extensively explored in conventional capillary systems for different applications. On the other hand, this separation strategy is still not as popular as free solution electrophoresis on chip-based platforms due to the effects of solvent in the background electrolyte on the sample injection, detection performance, and microfluidic platform compatibility. In this way, this review summarizes the main achievements on nonaqueous microchip electrophoresis (NAME). To the best of our knowledge, this is the first review dedicated to discuss exclusively nonaqueous electrophoresis on chip-based systems. For this purpose, some important theoretical aspects involved when separations are performed in organic medium, such as equilibrium, interactions and electrophoretic considerations, are included in the review. In addition, the main challenges, advantages and influences of nonaqueous media on the sample injection, detection as well as the choice of the substrate to fabricate chip-based electrophoresis devices are highlighted. Last, examples showing the feasibility of nonaqueous microchip electrophoresis for applications exploiting different methodologies, operational, and instrumental conditions are summarized and discussed. We hope this review can be useful to spread the huge potential of nonaqueous electrophoresis on microfluidic platforms.