Chiral recognition of mandelic acid by l-phenylalanine-modified sensor using quartz crystal microbalance

This study presents a new method for the highly selective recognition of chiral mandelic acid (MA) using l-phenylalanine (l-Phe) as the selector. The proposed method is based on quartz crystal microbalance (QCM) detection, integrated with a vapor diffused molecular assembly (VDMA) reaction technique. The construction of the l-Phe-modified QCM sensor involved a two-step assembly procedure. The chiral recognizability of l- and d-MA on the l-Phe-modified surface was then examined using the VDMA method and QCM. The chiral discrimination factor between l- and d-MA detected by QCM, αl-MA/d-MA, was found to be about 8. The VDMA selective sensing of l-MA on the l-Phe-modified surface was also confirmed by the contact angle measurements. The l-Phe-modified QCM sensor showed good stability and reusability. The present chiral recognition results suggest that l-phe is an excellent resolving agent for the resolution of chiral mandelic acid.