SFC for chiral separations in bioanalysis

This review covers literature investigating methods for enantioselective chromatography using supercritical fluids as mobile phase constituents (SFC) in the field of bioanalysis. It provides an overview on method development and screening approaches published in scientific literature 2014-2018. Chiral stationary phases are used to create a chiral environment that allows for discrimination of enantiomers. Especially polysaccharide-based stationary phases are used in methods of recent investigations. In comparison to HPLC chiral SFC separation provides more selective cavity effects of inclusion-type chiral separation phases. Modifier and additive choices as well as further operating conditions like backpressure, temperature and flow rate are summarized and critically discussed. Further on, observed sample pretreatment and possible detection techniques are presented. SFC hyphenated to mass detection was found of major relevance and is therefore further discussed. Coupling of SFC with different detectors allows for straightforward use in bioanalysis. Interfacing MS detectors is generally performed including a make-up pump. Thus, applied make-up conditions were also reviewed. While most of the chiral separations in HPLC are performed in normal phase mode, and thus, challenge MS hyphenation, SFC-MS hyphenation can be easily achieved. This allows for convenient application in chiral trace analyses, often required in bioanalysis. Even worse in enantioseparation than in achiral chromatography, method development in SFC suffers from a lack of knowledge in separation mechanisms and thus approaches are often quite unique and most often achieved by screening using a One-Factor-at-a-Time (OFAT) design. Broad screening experiments with methodical approaches still appear as method of choice for now.