Synthesis of magnetic halloysite nanotube-based molecularly imprinted polymers for sensitive spectrophotometric detection of metoclopramide in urine samples.

A novel molecularly imprinted polymer was synthesized on magnetic halloysite nanotube via surface initiated reversible addition-fragmentation chain transfer polymerization in the presence of 2-aminoethylmethacrylamide, 2-Cyano-2-propyl benzodithioate, ethylene glycol dimethacrylate (EGDMA) and azobis(isobutyronitrile) for sensitive and selective spectrophotometric determination of metoclopramide in urine samples. The synthesized imprinted polymer was characterized by several surface characterization techniques and the results indicated there was a thin polymer network on the magnetic halloysite nanotube. The rebinding properties of the molecularly imprinted magnetic halloysite nanotube were also investigated in detail and the maximum adsorption capacity and imprinting factor were found to be 37.8 mg/g and 4.51, respectively. The application of the proposed method was carried out by enrichment and spectrophotometric determination of metoclopramide via formation of a charge transfer complex between picric acid and eluted metoclopramide. Under the optimized conditions, the calibration curve was linear in the concentration range of 5.0-150.0 ng/mL and the limit of detection and the limit of quantification were calculated to be 1.5 ng/mL and 4.95 ng/mL, respectively. The inter-day and intra-day precisions were below 5% and recoveries were between 92.8% and 99.2%. The results showed that the proposed method increased the sensitivity and selectivity for spectrophotometric determination of metoclopramide.

Selective separation and determination of quercetin from red wine by molecularly imprinted nanoparticles coupled with HPLC and ultraviolet detection.

In this study, a highly sensitive and selective sample pretreatment procedure using molecularly imprinted silica nanoparticles was developed for the extraction and determination of quercetin in red wine samples coupled with high-performance liquid chromatography with ultraviolet detection. The imprinted silica nanoparticles were prepared in the presence of N-acryoyl-l-aspartic acid (functional monomer), quercetin (template), azobisisobutyronitrile (initiator) and methylene bisacrylamide (cross-linker) and methanol/water (porogen) via surface-initiated reversible addition-fragmentation chain transfer polymerization. Surface characterization was performed and several imprinting parameters were investigated, and the results indicated that adsorption of quercetin on the imprinted silica nanoparticles followed a pseudo-first-order adsorption isotherm with a maximum adsorption capacity at 26.4 mg/g within 60 min. The imprinted silica nanoparticles also showed satisfactory selectivity towards quercetin as compared with its structural analogues. Moreover, the imprinted nanoparticles preserved their recognition ability even after five adsorption-desorption cycles. Meanwhile, the nanoparticles were successfully applied to selective extraction of quercetin from red wine with a high recovery (99.7-100.4%). The limit of detection was calculated to be 0.058 µg/mL with a correlation coefficient 0.9996 in the range of 0.2-50 µg/mL. As a result, the developed selective extraction method using molecular imprinting technology simplifies the sample pretreatment procedure before determination of quercetin in real samples.