Eco-friendly Deep Eutectic Solvents Contribute to Improving the Separation of Isoquinoline Alkaloids in Supercritical Fluid Chromatography

In this work, for the first time, 10 isoquinoline alkaloids (IQAs) were separated and determined by supercritical fluid chromatography (SFC) utilizing eco-friendly deep eutectic solvents (DESs) as novel mobile phase additives. The effects of DES types, DES concentrations, and other chromatographic parameters on the separation of IQAs were systematically optimized. Improved resolution of alkaloids and decreased peak tailing were distinctly observed when DESs were added to the mobile phase. The supercritical CO2 and MeOH-2% H2O-0.5% FA-0.25% ChCl-Gly were used as the optimized mobile phase, and the 10 IQAs were well separated in SFC. The separation mechanism might be attributed to the fact that DESs were used as silanol blockers to compete for the adsorption sites with IQAs on the silica surface. The present study suggests that the separation of IQAs from complex samples in SFC can be effectively improved using DESs as mobile phase additives. Moreover, the proposed "green" method for analyzing IQAs focuses on reducing the use of organic solvents and improving the applicability for alkaloid analysis.