Separation and determination of phenolic compounds using novel deep eutectic solvent-in-water microemulsion...

Microemulsion electrokinetic chromatography (MEEKC) is a mode of capillary electrophoresis with a wide range of applications in which microemulsion is utilized as background electrolyte to achieve the separation of analytes. Microemulsions are composed of oil droplets, aqueous buffer, surfactant, and co-surfactant. Currently, conventional organic reagents act as the most commonly used oil phase in microemulsions, which are unfriendly to the environment. Recently, deep eutectic solvent (DES) has become a new type of eco-friendly solvent due to its non-toxicity. Therefore, it is of great value to establish a new MEEKC method by replacing conventional organic reagents as the oil phase with DES.

The novel DES/W MEEKC method was established for phenolic compounds in Senecio scandens samples. Single-factor experiments and response surface methodology were performed to systematically optimize the crucial parameters for the method, including the type and content of the oil phase, surfactant content, concentration of borax buffer, and pH of the background solution. Under the optimized conditions, satisfactory regression curves were established for all standard analytes with correlation coefficients ≥0.9990. The method featured high sensitivity and favorable accuracy, with the instrumental detection limit in the range of 0.22-1.04 μg/mL, and intraday and interday precision for migration time expressed as relative standard deviations of 0.18-0.82% and 1.25-2.50%, respectively. The DES/W MEEKC method was successfully applied to Senecio scandens with good recoveries of 87.72-106.99%. In conclusion, the newly established DES/W MEEKC method is highly efficient, green and environmentally friendly.

DES is considered a green and efficient solvent. The DES/W MEEKC method is highly efficient and environmentally friendly. Actually, the method provides a novel and effective analytical tool for the simultaneous separation and determination of multiple phenolic compounds, especially in complex plant matrices. In the future, the DES/W MEEKC method still has the prospect of being widely used in the separation of other complex phytochemicals.