Electrokinetic Manipulations Combined With Direct and Ambient Ionization Mass Spectrometry

Mass spectrometry (MS) is a powerful analytical technique that typically involves sample preparation and online analytical separation before MS detection. Traditional methods often face bottlenecks in sample preparation and analytical separation, despite the rapid detection capabilities of MS. This review explores the integration of electrokinetic manipulations directly with the ionization step to enhance MS performance, focusing on methods that eliminate or simplify sample preparation and separation processes. Techniques such as paper spray, electrophoresis in nanoelectrospray ionization (nESI) emitters, induced nESI, counterflow gradient electrofocusing, and in-syringe electrokinetics are highlighted for their ability to combine extraction and ionization in a single step, significantly improving throughput. The review delves into the use of electric fields during sample preparation and separations for these methods, demonstrating the efficiency of electrophoretic methods in driving extractions, crude separations, desalting, and enhanced sensitivity. The integration of these methods directly with MS ionization aims to enhance the analytical capabilities of mass spectrometry, while reducing costs and increasing throughput relative to traditional approaches.