Ultra-High-Performance Micellar Liquid Chromatography Comparing Tween 20 and Tween 40 for the Determination of Hydroxycinnamic Acids

Abstract

A simple and green ultra-high-performance micellar liquid chromatography (MLC) method was developed here, comparing Tween 20 and Tween 40 for the first time as the only mobile phase modifiers with a C18 column. Its application to the separation of nine hydroxycinnamic acid (HCA) derivatives (cinnamic, caffeic, ferulic, sinapic, o-, m-, p-coumaric, 3,4-dihydroxyhydrocinnamic, and chlorogenic acids) was made, due to their importance as antioxidants in a variety of natural beverages such as wine and coffee. The optimal conditions of 45 °C temperature (T), 1% surfactant in the mobile phase, and pH control with 2.5 mM sulfuric acid were determined and used to elucidate the analytical figures of merit. Although the effect of these conditions was insignificant between the two surfactants, the nine-component HCA mixture was separated faster—in about 15 min—and with less peak tailing using Tween 20 than with Tween 40. The linearity of the Van’t Hoff (lnk versus 1/T) plots was evident for Tween 20, indicating a single retention mechanism—but less so for Tween 40. The equilibrium constants of the analytes with the micelles and the stationary phase were calculated. The developed method was successfully used to analyze organic red wine, spiked organic red wine, and green coffee diet pills. The percent recoveries of the nine HCA compounds spiked in the organic red wine ranged from 90% to 107%. The green coffee extract diet pills showed the presence of a significant amount of chlorogenic acid.

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“…Stationary phase temperature, surfactant concentration and type, and co-eluents are the three most crucial chromatographic factors. To increase separation effectiveness and shorten the retention period, the working column temperature should be higher than the Kraft point [38][39][40].…”

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“…The increased temperature contributes to faster mass transfer kinetics, which often improves the separation efficiency [67]. Generally, the increase in the column temperature leads to a shorter retention time of the analytes [68,69]. However, in some cases, it was observed that higher column temperature contributed to the increased value of the tailing factor [69].…”

“…The application of the DoE approach during the mixed MLC method development facilitates the optimization of the critical chromatographic parameters such as concentration of SDS and Brij-35 and allows timely perception of their interaction. Polysorbates are another type of nonionic surfactant that can be used for MLC, including polysorbate 20 (Tween 20) or polysorbate 40 (Tween 40) [68,73]. The comparison of the influence of Tween 20 and Tween 40 as eluents in the MLC mobile phase on the retention of hydroxycinnamic acid compounds showed that shorter retention times and better peak shapes are observed using Tween 20 [68].…”

“…Polysorbates are another type of nonionic surfactant that can be used for MLC, including polysorbate 20 (Tween 20) or polysorbate 40 (Tween 40) [68,73]. The comparison of the influence of Tween 20 and Tween 40 as eluents in the MLC mobile phase on the retention of hydroxycinnamic acid compounds showed that shorter retention times and better peak shapes are observed using Tween 20 [68].…”