Yang-Guang Wang

Surface-Imprinted Magnetic Carboxylated Cellulose Nanocrystals for the Highly Selective Extraction of Six Fluoroquinolones from Egg Samples

We herein describe a novel adsorbent based on molecularly imprinted polymers (MIPs) on the surface of magnetic carboxylated cellulose nanocrystals (Fe3O4@CCNs@MIPs) for the separation and purification of six fluoroquinolones (FQs) from egg samples. The obtained Fe3O4@CCNs@MIPs not only exhibited a large surface area and specific recognition toward FQs, but also were easily gathered and separated from the egg samples using an external magnetic field. The morphologies and surface groups of the Fe3O4@CCNs@MIPs were assessed by X-ray photoelectron spectroscopy, transmission electron microscopy, vibrating sample magnetometry, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller surface area analysis. The Fe3O4@CCNs@MIPs exhibited high selectivity toward six structurally similar FQs. An enrichment approach was established for the measurement of six FQs from egg samples using Fe3O4@CCNs@MIPs coupled to high-performance liquid chromatography. The recovery of spiked FQs ranged from 75.2-104.9% and limit of detection was in the range of 3.6-18.4 ng g-1 for the six FQs. Therefore, the proposed method is a promising technique for the enrichment, separation, and determination of FQs from biomatrices.

Partially Hydrolyzed Bamboo (Phyllostachys heterocycla) As a Porous Bioadsorbent for the Removal of Pb(II) from Aqueous Mixtures

A novel porous succinylated bioadsorbent was prepared by the partial enzymatic hydrolysis of bamboo (Phyllostachys heterocycla) and its subsequent modification with succinic anhydride. Pb(II) removal from solutions that also contained sodium chloride and an amino acid was investigated using the bioadsorbent. Enzymatic hydrolysis increased the number of accessible hydroxyl groups and surface area of the raw bamboo, and created many pores within the material. The porous succinylated bioadsorbent exhibited high efficiency for Pb(II) binding. The sodium chloride content significantly decreased the Pb(II) adsorption capacity, whereas a minor effect was observed in the presence of arginine. The experimental data could be accurately described by a pseudo-second-order kinetics model, and the adsorption proceeded via an ion exchange mechanism. Even in a solution containing sodium chloride and arginine, the maximum adsorption capacity of Pb(II) by the porous succinylated bioadsorbent was 99.5 mg/g at 303 K.

Bamboo-derived porous bioadsorbents and their adsorption of Cd(II) from mixed aqueous solutions

Two porous bioadsorbents were successfully prepared from the partial enzymatic hydrolysis of bamboo and subsequent chemical modification with succinic anhydride. We investigated the abilities of the partially enzymatically hydrolyzed bamboo (PEB) and the porous succinylated bamboo (PSB) to adsorb Cd(II) from a solution containing sodium chloride and an amino acid. The partial enzymatic hydrolysis created many pores within the raw bamboo, and both the porous structure and the post-succinylation carboxyl group content were important for high adsorption capacity. The presence of sodium chloride and the amino acid markedly decreased the adsorption capacities of the bioadsorbents. The experimental data could be described perfectly with the Langmuir adsorption isotherm model and pseudo second-order kinetics model. Even in solutions containing sodium chloride and arginine, the maximum Cd(II) adsorption capacities at 303 K were 38.18 and 120.34 mg g−1 for PEB and PSB, respectively.

Synthesis and Characterization of Magnetic Molecularly Imprinted Polymer for the Enrichment of Ofloxacin Enantiomers in Fish Samples

A new method for the isolation and enrichment of ofloxacin enantiomers from fish samples was developed using magnetic molecularly imprinted polymers (MMIPs). These polymers can be easily collected and rapidly separated using an external magnetic field, and also exhibit a high specific recognition for ofloxacin enantiomers. The preparation of amino-functionalized MMIPs was carried out via suspension polymerization and a ring-opening reaction using rac-ofloxacin as a template, ethylenediamine as an active group, glycidyl methacrylate and methyl methacrylate as functional monomers, divinylbenzene as a cross-linker, and Fe3O4 nanoparticles as magnetic cores. The characteristics of the MMIPs were assessed using transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM) measurements. Furthermore, the adsorption properties were determined using Langmuir and Freundlich isotherm models. The conditions for use of these MMIPs as magnetic solid-phase extraction (MSPE) sorbents, including pH, adsorption time, desorption time, and eluent, were investigated in detail. An extraction method using MMIPs coupled with high performance liquid chromatography (HPLC) was developed for the determination of ofloxacin enantiomers in fish samples. The limits of quantitation (LOQ) for the developed method were 0.059 and 0.067 μg∙mL−1 for levofloxacin and dextrofloxacin, respectively. The recovery of ofloxacin enantiomers ranged from 79.2% ± 5.6% to 84.4% ± 4.6% and ofloxacin enantiomers had good linear relationships within the concentration range of 0.25–5.0 μg∙mL−1 (R2 > 0.999). The obtained results demonstrate that MSPE-HPLC is a promising approach for preconcentration, purification, and simultaneous separation of ofloxacin enantiomers in biomatrix samples.

Fabrication of Composite Beads Based on Calcium Alginate and Tetraethylenepentamine-Functionalized MIL-101 for Adsorption of Pb(II) from Aqueous Solutions

In this work, a tetraethylenepentamine (TEPA)-grafted metal-organic framework material (MIL-101) was synthesized. The introduction of TEPA increased the abundance of functional groups on the MIL-101. As a powdery adsorbent, MIL-101-TEPA can be difficult to separate. In order to solve this problem, we combined MIL-101-TEPA with sodium alginate (SA) and injected the mixture into a CaCl2 solution to solidify the powder into beads with a particle size of 3 mm. The easily recovered adsorbent was applied to the adsorption of Pb(II) from water. The structure and characterization of the adsorbent were investigated through scanning electron microscope (SEM), Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). We also optimized the adsorption conditions. The results of the study showed that the adsorption process was chemisorptive and endothermic in nature. The maximum adsorption capacity of the composite beads was 558.6 mg/g. Meanwhile MIL-101-TEPA@CA showed good repeatable utilization.

Facile Preparation of Metal-Organic Framework (MIL-125)/Chitosan Beads for Adsorption of Pb(II) from Aqueous Solutions

In this study, novel composite titanium-based metal-organic framework (MOF) beads were synthesized from titanium based metal organic framework MIL-125 and chitosan (CS) and used to remove Pb(II) from wastewater. The MIL-125-CS beads were prepared by combining the titanium-based MIL-125 MOF and chitosan using a template-free solvothermal approach under ambient conditions. The surface and elemental properties of these beads were analyzed using scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopies, as well as thermal gravimetric analysis. Moreover, a series of experiments designed to determine the influences of factors such as initial Pb(II) concentration, pH, reaction time and adsorption temperature was conducted. Notably, it was found that the adsorption of Pb(II) onto the MIL-125-CS beads reached equilibrium in 180 min to a level of 407.50 mg/g at ambient temperature. In addition, kinetic and equilibrium experiments provided data that were fit to the Langmuir isotherm model and pseudo-second-order kinetics. Furthermore, reusability tests showed that MIL-125-CS retained 85% of its Pb(II)-removal capacity after five reuse cycles. All in all, we believe that the developed MIL-125-CS beads are a promising adsorbent material for the remediation of environmental water polluted by heavy metal ions.

Investigation into the enantiospecific behavior of trichlorfon enantiomers during microorganism degradation

Trichlorfon (TF) is commonly used as an antiparasitic agent in aquaculture. A chiral HPLC method for the detection of the two TF enantiomers in fish was developed using metolcarb as an internal standard. Both the enantiospecific behavior of R-(−)-TF and S-(+)-TF and the formation of the toxic metabolite dichlorvos during fish storage were investigated using the developed HPLC method. Results showed that the degradation of R-(−)-TF and S-(+)-TF during fish storage was enantiospecific at both 18 °C and 25 °C, with R-(−)-TF being preferentially degraded. However, no enantiospecific behavior of TF enantiomers was observed when fish was stored at either −18 °C or 4 °C. In addition, dichlorvos formation was detected in TF-contaminated fish at a range of storage temperatures. Furthermore, microbial activity was found to play an important role in the degradation of TF enantiomers and in the formation of dichlorvos, and contributed to the enantiospecific behavior of TF enantiomers during storage.

Chiral separation and enantioselective degradation of trichlorfon enantiomers in mariculture pond water

In this study, the dissipation and enantioselective degradation of trichlorfon (TF) enantiomers in mariculture pond water was investigated under various conditions using a chiral HPLC method. The results showed that the TF enantiomers dissipated following first-order kinetics in the mariculture pond water under natural, dark, sterile, and dark and sterile conditions. S-(+)-TF degraded more rapidly than R-(−)-TF under natural and dark conditions, whereas the dissipation of TF enantiomers in mariculture pond water was non-enantioselective under sterile, and dark and sterile conditions. Light and microbial activity played important roles in the dissipation of the TF enantiomers in mariculture pond water, and the TF enantiomers degraded faster at higher temperatures. Microbial activity was found to be responsible for the enantioselectivity under these conditions. The results of the study can be used to evaluate the environmental risk of TF at the enantiomer level.

Validation a solid-phase extraction-HPLC method for determining the migration behaviour of five aromatic amines from packaging bags into seafood simulants

The simultaneous determination of five aromatic amines and their potential migration from packaging bags into seafood simulants were investigated. A validated HPLC method was developed for the separation and qualification of five aromatic amines in seafood simulants. By combining solid-phase extraction (SPE), these amines were efficiently separated on a Halo C18 column (150 × 4.6 mm i.d., 2.7 μm, particle size) using a mobile phase of methanol/phosphate buffer solution (5 mmol l−1, pH 6.9) with gradient elution. The linear range was 0.1–10.0 mg l−1; the absolute recoveries ranged from 85.3% to 98.4%; and the limits of detection of the five aromatic amines were between 0.015 and 0.08 mg l−1. In this work the migration profile of aromatic amines from black plastic bags was investigated at temperatures of 4°C with water, 3% acetic acid solution, 10% ethanol solution and 50% ethanol solution as seafood simulants, respectively. The migration of the five aromatic amines under different conditions showed that residual o-methoxyaniline, p-chloroaniline, aniline and 2,6-dimethylaniline leaching from black plastic bags increased with incubation time. No detectable 3,3´-dimethylbenzidine was found to leach from the bags.

Validation of a Chiral Liquid Chromatographic Method for the Degradation Behavior of Flumequine Enantiomers in Mariculture Pond Water.

In this work, flumequine (FLU) enantiomers were separated using a Chiralpak OD-H column, with n-hexane-ethanol (20:80, v/v) as the mobile phase at a flow rate of 0.6 mL/min. Solid phase extraction (SPE) was used for cleanup and enrichment. The limit of detection, limit of quantitation, linearity, precision, and intra/interday variation of the chiral high-performance liquid chromatography (HPLC) method were determined. The developed method was then applied to investigate the degradation behavior of FLU enantiomers in mariculture pond water samples. The results showed that the degradation of FLU enantiomers under natural, sterile, or dark conditions was not enantioselective. Chirality 28:649-655, 2016.