Chiral Separations using Miniaturized Techniques: State of the Art and Perspectives

The separation and analysis of chiral compounds is an important topic of research, because these analytes are involved in various processes, e.g., biological, pharmacological, human health, etc. Their separation has also been recently obtained utilizing microfluidic techniques, such as capillary electrophoresis (CE), electrochromatography (CEC), and capillary/nano-liquid chromatography (CLC/nano-LC). Enantiomeric separation is mainly obtained by applying the direct resolution method, where a chiral selector (CS) is present in the separation system, either added to the mobile phase (MP) or bonded to the stationary phase or to the capillary wall. Among the several CSs used in microfluidic techniques, cyclodextrins, proteins, peptides, glycopeptide antibiotics, and modified polysaccharides are the most employed. Microfluidic techniques can offer several advantages over conventional analytical tools, e.g., high efficiency, high mass sensitivity, and reduced volumes of MP and sample. Optimized methods have been applied in different fields, such as biomedical, food chemistry, environment, pharmaceutical, etc. Excellent results have been achieved in CE and nano-LC. Although CEC can offer higher efficiency due to the use of a strong electroosmotic flow, its use is less popular than the other. This limitation can be explained with the limited number of the stationary phases (SPs) commercially available.