Chiral discrimination in the gas phase using different transducers: thickness shear mode resonators and reflectometric interference spectroscopy.

The discrimination of optical isomers (enantiomers) in the gas phase has been performed using two different analytical tools:  thickness shear mode resonators (TSMRs) and reflectometric interference spectroscopy (RIFS). The selective coatings included both enantiomers ((S)- and (R)-receptor) of a Chirasil-Val derivative (stationary phase material in GC) with octyl side chains. Successful discrimination of the enantiomers of different types of analytes (amino acids and lactates) was achieved. The results of both transduction methods were consistent and in good agreement with GC measurements. In addition, different mixtures of both enantiomers of the respective analyte were measured, and the enantiomeric composition could be quantitatively determined with excellent reliability. Since the sensors allow on-line monitoring (not possible with GC) of enantiomeric purity, an application in industrial synthesis (process control) of such compounds represents an interesting feature, especially with regard to the tested derivatives of lactic acid.