Computational design and fabrication of core-shell magnetic molecularly imprinted polymer for dispersive micro-solid-phase extraction coupled with high-performance liquid chromatography for the determination of rhodamine 6G.

A novel core-shell magnetic nano-adsorbent with surface molecularly imprinted polymer coating was fabricated and then applied to dispersive micro-solid-phase extraction followed by determination of rhodamine 6G using high-performance liquid chromatography. The molecularly imprinted polymer coating was prepared by copolymerization of dopamine and m-aminophenylboronic acid (functional monomers), in the presence of rhodamine 6G (template). The selection of the suitable functional monomers was based on the interaction between different monomers and the template using the density functional theory. The ratios of the monomers to template were further optimized by an OA9 (3(4) ) orthogonal array design. The binding performances of the adsorbent were evaluated by static, kinetic, and selective adsorption experiments. The results reveal that the adsorbent possesses remarkable affinity and binding specificity for rhodamine 6G because of the enhanced Lewis acid-base interaction between the B(Ш) embedded in the imprinted cavities and the template. The nano-adsorbent was successfully applied to dispersive micro-solid-phase extraction coupled to high-performance liquid chromatography for the trace determination of rhodamine 6G in samples with a detection limit of 2.7 nmol/L. Spiked recoveries ranged from 93.0-99.1, 89.5-92.7, and 86.9-105% in river water, matrimony vine and paprika samples, respectively, with relative standard deviations of less than 4.3%.

Preparation and application of a carbon paste electrode modified with multi-walled carbon nanotubes and boron-embedded molecularly imprinted composite membranes.

An innovative electrochemical sensor was fabricated for the sensitive and selective determination of tinidazole (TNZ), based on a carbon paste electrode (CPE) modified with multi-walled carbon nanotubes (MWCNTs) and boron-embedded molecularly imprinted composite membranes (B-MICMs). Density functional theory (DFT) calculations were carried out to investigate the utility of template-monomer interactions to screen appropriate monomers for the rational design of B-MICMs. The distinct synergic effect of MWCNTs and B-MICMs was evidenced by the positive shift of the reduction peak potential of TNZ at B-MICMs/MWCNTs modified CPE (B-MICMs/MWCNTs/CPE) by about 200 mV, and the 12-fold amplification of the peak current, compared with a bare carbon paste electrode (CPE). Moreover, the coordinate interactions between trisubstituted boron atoms embedded in B-MICMs matrix and nitrogen atoms of TNZ endow the sensor with advanced affinity and specific directionality. Thereafter, a highly sensitive electrochemical analytical method for TNZ was established by different pulse voltammetry (DPV) at B-MICMs/MWCNTs/CPE with a lower detection limit (1.25 × 10-12 mol L-1) (S/N = 3). The practical application of the sensor was demonstrated by determining TNZ in pharmaceutical and biological samples with good precision (RSD 1.36% to 3.85%) and acceptable recoveries (82.40%-104.0%).

A highly sensitive and selective sensor based on a graphene-coated carbon paste electrode modified with a computationally designed boron-embedded duplex molecularly imprinted hybrid membrane for the sensing of lamotrigine.

An innovative electrochemical sensor, based on a carbon paste electrode (CPE) modified with graphene (GR) and a boron-embedded duplex molecularly imprinted hybrid membrane (B-DMIHM), was fabricated for the highly sensitive and selective determination of lamotrigine (LMT). Density functional theory (DFT) was employed to study the interactions between the template and monomers to screen appropriate functional monomers for rational design of the B-DMIHM. The distinct synergic effect of GR and B-DMIHM was evidenced by the positive shift of the reduction peak potential of LMT at B-DMIHM/GR modified CPE (B-DMIHM/GR/CPE) by about 300mV, and the 13-fold amplification of the peak current, compared to a bare carbon paste electrode (CPE). The electrochemical reduction mechanism of lamotrigine was investigated by different voltammetric techniques. It was illustrated that square wave voltammetry (SWV) was more sensitive than different pulse voltammetry (DPV) for the quantitative analysis of LMT. Thereafter, a highly sensitive electroanalytical method for LMT was established by SWV at B-DMIHM/GR/CPE with a good linear relationship from 5.0×10-8 to 5.0×10-5 and 5.0×10-5 to 3.0×10-4molL-1 with a lower detection limit (1.52×10-9molL-1) based on the lower linear range(S/N=3). The practical application of the sensor was demonstrated by determining the concentration of LMT in pharmaceutical and biological samples with good precision (RSD 1.04-4.41%) and acceptable recoveries (92.40-107.0%).

Carbon paste electrode modified with duplex molecularly imprinted polymer hybrid film for metronidazole detection.

A novel electrochemical sensor based on duplex molecularly imprinted polymer (DMIP) hybrid film modified carbon paste electrode (CPE) has been developed for highly sensitive and selective determination of metronidazole (MNZ). A conductive poly(anilinomethyltriethoxysilane) film is firstly electrodeposited on the surface of a CPE, and then a molecularly imprinted polysiloxane (MIPS) membrane is covalently covered on the film via sol-gel process. The as-constructed DMIP hybrid film, combining the advantages of MIPS and conducting MIP, can make feasible the direct and efficient signal transformation between the target analyte and the transducer, as well as enhance the imprinting recognition capability, mass transfer efficiency and the detection sensitivity. Under optimized conditions, the reduction peak currents of MNZ are linear to MNZ concentrations in the range from 4.0×10(-7) to 2.0×10(-4) molL(-1) with a detection limit of 9.1×10(-8)molL(-1). The RSD values vary from 2.9% to 4.7% for intra-day and from 3.4% to 4.2% for inter-day precision. The DMIP-based sensor has been successfully applied for the determination of MNZ in biological and pharmaceutical samples. The accuracy and reliability of the method is further confirmed by high performance liquid chromatography.