Supercritical fluid chromatography for vitamin and carotenoid analysis: an update covering 2011-2021.

As it is known, the chromatographic separations of vitamins is not a trivial issue. The subtle heterogeneity among homologs belonging to the same group makes it difficult to perform their speciation. On the other hand, differences in terms of structure complicate the simultaneous analysis of the main forms belonging to the several vitamin groups. Long times of analysis as well as the use of conventional toxic organic solvents, such as hexane and MeOH, are other downsides of conventional methods based on liquid chromatography. Over the last few years, Ultra-Performance Convergence Chromatography (UPCC or UPC2) has emerged as a unique separation technique for its green character and the unparalleled ability to achieve chiral and achiral separations with an unequalled speed and reproducibility. Conceived after 2010, UPCC merges the advantages of the conventional supercritical fluid chromatography (SFC) with those of the ultra-high performance liquid chromatography (UHPLC) technology. Its application to vitamin and carotenoid analysis has shown a potential in solving the above-mentioned issues, which is still untapped. This review offers a comprehensive perspective of the SFC advancements in the last ten years and the advantages that arise from its application in vitamin and carotenoid analysis. Compared to conventional techniques, the flexibility of UPCC is unique, making it possible the simultaneous analysis of different group of achiral and chiral vitamins within the same short chromatographic run.