Ion Pair-Based Mobile Phase Additives to Improve the Separation of Polar Compounds in Supercritical Fluid Chromatography

In this study, a supercritical fluid chromatography (SFC) method based on ion pair reagents was used to separate polar alkaloids. The chromatographic parameters containing stationary phases, additive types, additive concentrations, back pressures, temperatures and flow rates, were optimized. Baseline separation of the compounds were completed in 20 min on an Agilent Pursuit 5 PFP column (4.6 × 150 mm) by using carbon dioxide as mobile phases and 7.5 mM sodium 1-pentanesulfonate as additive with a gradient elution at 140 bar, 60 °C, and a flow rate of 1.5 mL/min. The retention rate and resolution of the analytes are satisfactory. The limits of detection were 27.04−298.03 ng/mL, and the limits of quantification were 90.15−993.42 ng/mL. The recoveries of low and high concentrations were 77.46%−111.86% and 83.84%−111.00%, respectively. This ion pair additive greatly improved the separation efficiency of polar compounds. Consequently, this SFC method was successfully applied to the separation of alkaloids from rhizoma corydalis.