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Chiral discrimination is critical in environmental and life sciences. However, an ideal chiral discrimination strategy has not yet been developed because of the inevitable nonspecific binding entity of wrong enantiomers or insufficient intrinsic optical activities of chiral molecules. Here, we propose an “inspector” recognition mechanism (IRM), which is implemented on a chiral imprinted polydopamine (PDA) layer coated on surface-enhanced Raman scattering (SERS) tag layer. The IRM works based on the permeability change of the imprinted PDA after the chiral recognition and scrutiny of the permeability by an inspector molecule. Good enantiomer can specifically recognize and fully fill the chiral imprinted cavities, whereas the wrong cannot. Then a linear shape aminothiol molecule, as an inspector of the recognition status is introduced, which can only percolate through the vacant and nonspecifically occupied cavities, inducing the SERS signal to decrease. Accordingly, chirality information exclusively stems from good enantiomer specific binding, while nonspecific recognition of wrong enantiomer is curbed. The IRM benefits from sensitivity and versatility, enabling absolute discrimination of a wide variety of chiral molecules regardless of size, functional groups, polarities, optical activities, Raman scattering, and the number of chiral centers.

Water compatible hollow porous molecularly imprinted nanospheres (HP-MINs) have been prepared for specific recognition and extraction of the blood pressure regulating drugs valsartan (VAL) and losartan (LOS). All synthetic steps were performed in aqueous medium and without consumption of organic solvents. The morphology and functionality of the materials were characterized by FT-IR, FE-SEM, and TEM techniques. The adsorption and selectivity experiments demonstrate that the HP-MINs possess a high binding capacity, fast kinetics, excellent water dispersibility and remarkable selectivity for VAL and LOS. The HP-MINs were utilized for dispersive solid phase extraction of VAL and LOS prior to their determination by HPLC-UV. Main variables and their interactions on extraction yield were optimized by multivariate analysis with least amount of experiments. Under optimized conditions, the method has a linear response in the 5–2000 μg L−1 concentration range of both VAL and LOS. The limits of detection are 1.5 μg L−1 for VAL and 1.4 μg L−1 for LOS.

The authors describe the preparation of molecularly imprinted nanoparticles (MINPs) for the solid phase extraction of hippuric acid (HA). The MINPs consists of a water-compatible organic-inorganic silica composite which was obtained from a functionalized silica by the sol-gel method. HA acted as the template, 3-aminopropyl trimethoxysilane as the functional monomer, and tetraethoxysilane as the crosslinker. Subsequently, methacryloxypropyltrimethoxysilane was used as a coupling agent to deposit a hydrophilic acrylamide coating onto the surface of the MINPs. The morphology and structure of the resulting restricted access material (referred to as RAM-MINP) were characterized by scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. Solid phase extraction of HA was accomplished by passing urine samples through a RAM-MINP-packed SPE cartridge. Following elution, HA was quantified by HPLC using UV detection at 228 nm. The effects of sample pH, amount of sorbent and eluent and washing solvent volumes were optimized by experimental design methodology under response surface methodology. Under optimized conditions, the mean extraction efficiency of HA from spiked samples is adequately repeatable, with relative standard deviations of