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Capillary electrophoresis (CE) is a powerful tool for the detection and quantification of a large variety of food-related molecules with different chemical properties. This chapter presents the principles of CE theory and instruments; furthermore, the procedure and development of different CE modes coupled with various detectors, formats (microchips), and interfaces with mass spectrometry are also reported. Advantages and limitations of each CE mode and new technical improvements are also discussed. The main recent CE applications on solid and liquid foods (vegetable and animal origin), other foods (honey, food supplements, and baby foods), additives, and contaminants are reviewed focusing on the potential of CE techniques in food quality, safety, and foodomics. For some sections, CE techniques are summarized in a table listing for each food matrix the most detected analytes in the last decade.

In this work we explored the feasibility of different CE-ESI-MS set-ups for the analysis of conformational states of an intact protein. By using the same background electrolyte at quasi physiological conditions (50 mM ammonium bicarbonate, pH 7.4) a sequential optimization was carried out, initially by evaluating a sheath-liquid interface with both a single quadrupole (SQ) and a time-of-flight (TOF) mass spectrometer; then a sheathless interface coupled with high-resolution QTOF MS was considered. Beta2-microglobulin has been taken as a model, as it is an amyloidogenic protein and its conformational changes are strictly connected to the onset of a disease. The separation of two conformers at dynamic equilibrium is achieved all the way down to the MS detection. Notably, the equilibrium ratio of the protein conformers is maintained in the electrospray source after CE separation. Strengths and weaknesses of each optimized set-up are emphasized and their feasibility in unfolding studies is evaluated. In particular, ESI-TOF MS can assign protein forms that differ by 1 Da only and sheathless interfacing is best suited to preserve protein structure integrity. This demonstrates the CE-ESI-MS performance in terms of separation, detection and characterization of conformational species that co-populate a protein solution.