Integrating a post-column makeup pump into preparative supercritical fluid chromatography systems to address stability and recovery issues during purifications

Post-Chromatographic Dicationic Ionic Liquid-Based Charge Complexation for Highly Sensitive Analysis of Anionic Compounds by Ultra-High-Performance Supercritical Fluid Chromatography Coupled with Electrospray Ionization Mass Spectrometry

A green analytical strategy has been developed for the analysis of 10 perfluorinated compounds (PFCs) incorporating supramolecular solvent (SUPRAS)-based extraction and ultra-high-performance supercritical fluid chromatography (UHPSFC)-tandem mass spectrometry. The SUPRAS was prepared through self-assembly of reverse micelles by mixing heptanol, tetrahydrofuran, and water at optimized volume ratios. An imidazolium-based germinal dicationic ionic liquid (DIL), 1,1-bis(3-methylimidazolium-1-yl) butylene difluoride ([C₄(MIM)₂]F₂), was dissolved in the make-up solvent of UHPSFC and introduced post-column but before the electrospray ionization source. After chromatographic separation on a Torus DIOL analytical column (100 mm × 2.1 mm, 1.7 μm), the PFC analytes associated with the DIL reagent through charge complexation. The formation of positively charged complexes resulted in improved ionization efficiency and analytical sensitivity. Enhancement in signal intensity by one to two magnitudes was achieved in the positive ionization mode compared to the negative ionization mode without using the dicationic ion-pairing reagent. The developed protocol was applied to 32 samples of real textiles and 6 samples of real food packaging materials, which exhibited great potential for the analysis of anionic compounds.

Chiral Stationary Phases for Liquid Chromatography: Recent Developments

The planning and development of new chiral stationary phases (CSPs) for liquid chromatography (LC) are considered as continuous and evolutionary issues since the introduction of the first CSP in 1938. The main objectives of the development strategies were to attempt the improvement of the chromatographic enantioresolution performance of the CSPs as well as enlarge their versatility and range of applications. Additionally, the transition to ultra-high-performance LC were underscored. The most recent strategies have comprised the introduction of new chiral selectors, the use of new materials as chromatographic supports or the reduction of its particle size, and the application of different synthetic approaches for preparation of CSPs. This review gathered the most recent developments associated to the different types of CSPs providing an overview of the relevant advances that are arising on LC.