Chiral separation by chromatographic and electromigration techniques. A Review

Abstract

This review gives a survey of different chiral separation principles and their use in high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography (TLC), capillary electrophoresis (CE) and capillary electrochromatography (CEC) highlighting new developments and innovative techniques. The mechanisms of the different separation principles are briefly discussed and some selected applications are shown.

Sensitive chiral analysis by capillary electrophoresis

“…CEC, which is a hybrid technique of CE and HPLC, is characterized by (i) high separation efficiency due to the plug profile of the mobile phase driven by the EOF, (ii) a wide range of HPLC chiral stationary phases, which can be transferred to CEC to provide broad enantioselectivity, (iii) low solvent consumption and low sample requirements, and (iv) easy coupling to MS. Enantioseparations are possible in three different types of columns: (i) packed capillary columns, (ii) open-tubular capillary columns, and (iii) monolithic capillary columns [33][34][35][36]. In addition, achiral packed capillaries in combination with BGEs where the chiral selector is added have also been used for enantioseparations by CEC.…”

Separation and enrichment of enantiopure from racemic compounds using magnetic levitation

“…The Maglev device was tilted at a 30° in order to increase the separation. 7 After allowing the mixture to separate overnight (~12 hours), two populations of crystals were clearly visible in the sample bottle, as shown in Figure 4. The top and the bottom populations levitated to a height of ~ 19 mm and ~ 16 mm, respectively.…”

“…1 (ii) A particular chiral stationary phase may only work for a limited number of compounds. 6,7 (iii) Formation of diastereomers introduces another compound into the system, and requires additional crystallization and filtration steps. 7 One of the alternative approaches to solution-based separation of enantiomers is to purify the desired enantiomer from a mixture of crystals of enantiomerically pure and racemic compound.…”

“…6,7 (iii) Formation of diastereomers introduces another compound into the system, and requires additional crystallization and filtration steps. 7 One of the alternative approaches to solution-based separation of enantiomers is to purify the desired enantiomer from a mixture of crystals of enantiomerically pure and racemic compound. Given a solution with high enantiomeric excess, one crystallization step usually generates crystals of the desired enantiomer contaminated with crystals of the racemic compound.…”

“…Particle size distribution is important when performing MagLev because the separation is slower as the particle size decreases (due to both Brownian motion and fluid shear). 7 Therefore, we performed particle size measurements on ibuprofen crystals using an optical microscope. Figure 3 show that particles of S-ibuprofen (with a mean size of 30 µm) have smaller sizes than those of RS-ibuprofen (with a mean size of 48 µm).…”