First truly deep eutectic solvent (DES) based stationary phase for high-performance liquid chromatography (HPLC)

Deep eutectic solvents (DESs) have gained significant attention due to their environmentally friendly properties and versatile applications in various fields, including analytical chemistry. This study investigates the use of a deep eutectic solvent (DES) composed of l-proline protonated with hydrochloric acid and xylitol as a surface modifier for silica-based stationary phases in high-performance liquid chromatography (HPLC). The DES was successfully immobilized on silica, and its impact on chromatographic performance was evaluated in normal-phase liquid chromatography (NP-HPLC). It was observed that DES immobilized layer acted as a real liquid stationary phase. The DES-modified columns exhibited improved selectivity, resolution for polar analytes, and shorter retention times for non-polar compounds compared to unmodified silica columns. Additionally, the DES-modified phase demonstrated long-term stability over multiple chromatographic cycles. These results highlight the potential of DESs as customizable, environmentally friendly stationary phase modifiers for enhancing chromatographic efficiency and selectivity, particularly in separating polar analytes, opening new avenues for the development of advanced chromatographic materials and contributing to greener and more efficient separation techniques. The robust preparation method also facilitates easy scalability for large-scale applications, such as the isolation of valuable compounds and the purification of complex mixtures, including phenols, amines, and nitro-derivatives.