Recent Advances in the Use of Capillary Electrophoresis Coupled to High-Resolution Mass Spectrometry for the Analysis of Small Molecules

The hyphenation of separation methods with mass spectrometry (MS) is one of the major topics in analytical chemistry. This is not only true for pressure-driven methods like HPLC but also for electro-driven ones such as capillary electrophoresis (CE). Research during the first years of CE-MS was primarily focused on technical improvements leading to commercially available equipment, making this combination more reliable and robust. On the other hand investigations on the applicability of CE-MS for the solution of real-world analytical problems were already performed during the early stages of this hyphenated technique. Thereby, CE was able to impress with its exceptional separation efficiency, whereas in most cases low-resolution MS instruments were used as detectors. The further development of reasonably priced benchtop reflectron time-of-flight (TOF)-MS and quadrupole time-of-flight (QTOF) instruments also promoted their use in CEMS, now providing high resolution in both dimensions separation and detection. Although TOF-MS is the most abundant high-resolution mass spectrometer coupled to CE, also other types of MS instruments such as Orbitraps of Fouriertransform- ion- cyclotron-resonance (FTICR)-MS have been employed for this purpose. The main goal of this critical review is to give an overview on the current state in the hyphenation of high-resolution mass spectrometry with electroseparation methods and to discuss possible future trends in this field.