Homochiral zeolites as chiral modifier for voltammetry sensors with high enantioselectivity

Composite enantioselective voltammetry sensors provide a well-known solution for the analysis and discrimination of enantiomerical drugs by voltammetry. The design of such sensor presumes the use of chiral substances to impart chirality to the electrode surface. We present the results of applying a theoretical approach based on simulating the adsorption of analyte enantiomers for preparing high enantioselectivity of pioneering enantioselective sensors using homochiral zeolites as chiral modifiers.

We investigated the ability of some homochiral zeolites like CZP, ITV, OSO, STW, MFI, and SOF to act as solid chiral modifiers. Using tryptophan and tyrosine as model objects, we found that the maximum difference between the adsorption energies (ΔE_ads) of enantiomers on zeolites occurs if enantiomers are placed into the pores of zeolites. The SOF zeolite demonstrates the best enantioselectivity to both amino acids. Moreover, we compared the theoretical results with the experimental enantioselectivity value for tryptophan on a sensor designed as a paste electrode with MFI as the chiral modifier. We found that the calculated value ΔE_ads(R-S) = −11.0 kJ/mol for MFI, though it is not the best value in the zeolite set considered, it is still enough for the sensor with MFI as the chiral modifier to demonstrate a higher than usual enantioselectivity (i_p1/i_p2 = 1.58) in an experiment with R- and S- tryptophan as the analyte.