Advances and Applications of Capillary Electrophoresis Mass Spectrometry in Food Analysis: Strategies for Online and Offline Preconcentration

Advancements in food technology have increased the need for thorough analysis to ensure food safety, quality, and compliance with regulatory requirements. Capillary electrophoresis–mass spectrometry (CE–MS) has emerged as a powerful tool in food analysis due to its high separation efficiency, low sample consumption, and ability to handle complex matrices. However, challenges such as the use of volatile running buffers and maintaining the stability of the electrical circuit connecting the CE and MS systems have been addressed through advancements in interface designs, such as sheathless systems and optimized sheath-liquid compositions. Online and offline preconcentration techniques have significantly enhanced CE–MS sensitivity (up to 1000-fold) through stacking methods such as large volume sample stacking (LVSS) and dynamic pH junction stacking. Meanwhile, offline sample preparation techniques, such as solid-phase extraction (SPE) and liquid-based methods, are essential for removing matrix interferences and preconcentrating targeted analytes. This review explores both online and offline preconcentration methods and emphasizes the importance of CE–MS in helping researchers develop effective strategies for selecting the best preconcentration methods for food analysis.