Flow methods in chiral analysis.

The methods used for the separation and analytical determination of individual isomers are based on interactions with substances exhibiting optical activity. The currently used methods for the analysis of optically active compounds are primarily high-performance separation methods, such as gas and liquid chromatography using chiral stationary phases or chiral selectors in the mobile phase, and highly efficient electromigration techniques, such as capillary electrophoresis using chiral selectors. Chemical sensors and biosensors may also be designed for the analysis of optically active compounds. As enantiomers of the same compound are characterised by almost identical physico-chemical properties, their differentiation/separation in one-step unit operation in steady-state or dynamic flow systems requires the use of highly effective chiral selectors. Examples of such determinations are reviewed in this paper, based on 105 references. The greatest successes for isomer determination involve immunochemical interactions, enantioselectivity of the enzymatic biocatalytic processes, and interactions with ion-channel receptors or molecularly imprinted polymers. Conducting such processes under dynamic flow conditions may significantly enhance the differences in the kinetics of such processes, leading to greater differences in the signals recorded for enantiomers. Such determinations in flow conditions are effectively performed using surface-plasmon resonance and piezoelectric detections, as well as using common spectroscopic and electrochemical detections.

Enantioselectivity of potentiometric sensors with application of different mechanisms of chiral discrimination.

In the recent years, numerous successful applications of various chiral selectors in high performance separation methods have generated an increasing interest in the application of some of these compounds as electroactive species in potentiometric sensors. The objective of this work was to examine the enantioselectivy of several different sensors employing substituted cyclodextrins, example antibiotic teicoplanin and electrodeposited conductive polymers for various chiral analytes. Varying degrees of enantioselectivity were found for the ion-selective electrodes examined, depending on the chiral selector used and the target analyte.