Fuhou Lei

Synthesis and characterization of core–shell magnetic molecularly imprinted polymers for solid-phase extraction and determination of Rhodamine B in food

Core-shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs), in which a Rhodamine B-imprinted layer was coated on Fe3O4 NPs. were synthesized. First, Fe3O4 NPs were prepared by a coprecipitation method. Then, amino-modified Fe3O4 NPs (Fe3O4@SiO2-NH2) was prepared. Finally, the MIPs were coated on the Fe3O4@SiO2-NH2 surface by the copolymerization with functional monomer, acrylamide, using a cross-linking agent, ethylene glycol dimethacrylate; an initiator, azobisisobutyronitrile and a template molecule, Rhodamine B. The Fe3O4@MIPs were characterized using a scanning electron microscope, Fourier transform infrared spectrometer, vibrating sample magnetometer, and re-binding experiments. The Fe3O4@MIPs showed a fast adsorption equilibrium, a highly improved imprinting capacity, and significant selectivity; they could be used as a solid-phase extraction material and detect illegal addition Rhodamine B in food. A method was developed for the selective isolation and enrichment of Rhodamine B in food samples with recoveries in the range 78.47-101.6% and the relative standard deviation was <2%.

Comparative study of alkaline hydrogen peroxide and organosolv pretreatments of sugarcane bagasse to improve the overall sugar yield

Green liquor (GL) combined with H2O2 (GL-H2O2) and green liquor (GL) combined with ethanol (GL-ethanol) were chosen for treating sugarcane bagasse. Results showed that the glucose yield (calculated from the glucose content as a percentage of the theoretical glucose available in the substrates)of sugarcane bagasse from GL-ethanol pretreatment (97.7%) was higher than that from GL-H2O2 pretreatment (41.7%) after 72h hydrolysis with 18 filter paper unit (FPU)/g-cellulose for cellulase, 27,175 cellobiase units (CBU)/g-cellulose for β-glucosidase. Furthermore, about 94.1% of xylan was converted to xylose after GL-ethanol pretreatment without additional xylanase, while the xylose yield was only 29.2% after GL-H2O2 pretreatment. Scanning electron microscopy showed that GL-ethanol pretreatment could break up the fiber severely. Moreover, GL-ethanol pretreated substrate was more accessible to cellulase and more hydrophilic than that of GL-H2O2 pretreated. Therefore, GL-ethanol pretreatment is a promising method for improving the overall sugar (glucose and xylan) yield of sugarcane bagasse.

Improvement of the enzymatic hydrolysis of furfural residues by pretreatment with combined green liquor and ethanol organosolv

Furfural residues (FRs) were pretreated with ethanol and a green liquor (GL) catalyst to produce fermentable sugar. Anthraquinone (AQ) was used as an auxiliary reagent to improve delignification and reduce cellulose decomposition. The results showed that 42.7% of lignin was removed and 96.5% of cellulose was recovered from substrates pretreated with 1.0 mL GL/g of dry substrate and 0.4% (w/w) AQ at 140°C for 1h. Compared with raw material, ethanol-GL pretreatment of FRs increased the glucose yield from 69.0% to 85.9% after 96 h hydrolysis with 18 FPU/g-cellulose for cellulase, 27 CBU/g-cellulose for β-glucosidase. The Brauner-Emmett-Teller surface area was reduced during pretreatment, which did not inhibit the enzymatic hydrolysis. Owing to the reduced surface area, the unproductive binding of cellulase to lignin was decreased, thus improving the enzymatic hydrolysis. The degree of polymerization of cellulose from FRs was too low to be a key factor for improving enzymatic hydrolysis.

Synthesis and characterization of molecularly imprinted polymers with modified rosin as a cross-linker and selective SPE-HPLC detection of basic orange II in foods

Basic orange II (BOII) is an alkaline azo dye that is listed as a prohibited substance in food additives. In order to develop a novel molecularly imprinted polymer (MIP) with modified rosin as a cross-linker for the selective solid-phase extraction (SPE) of BOII in foods, MIP was synthesized using BOII as the template molecule, acrylamide as the functional monomer, and maleic rosin glycol acrylate (MRGA) as the cross-linking agent. MIP was characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. Compared to the imprinted polymers prepared by the traditional cross-linker, MIP showed a highly imprinting capacity, significant selectivity, hardness and toughness, and it could be used as a SPE material, as well as for the detection of illegal addition of BOII in food. In the sample with a spiked level of 5–11 mg kg−1, BOII in foods revealed an average recovery rate of 68.43–80.25% with a precision (relative standard deviation) of less than 1.2%.

An electrochemical sensor for the determination of phoxim based on a graphene modified electrode and molecularly imprinted polymer

Graphene and a novel cross-linker (ethylene glycol maleic rosinate acrylate) for preparing highly sensitive, molecularly imprinted sensors were proposed for phoxim determination. A molecularly imprinted polymer (MIP) film was created on a graphene-modified electrode for the determination of phoxim using a free radical polymerization method. The electrochemical properties of the MIP and non-molecularly imprinted polymer (NIP) sensors were investigated via cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The surface morphology of the imprinted film was characterized by scanning electron microscopy (SEM). Under the optimal experimental conditions, the peak currents were proportional to the concentrations of phoxim in the range of 8.0 × 10−7 to 1.4 × 10−4 mol L−1 with a detection limit of 2.0 × 10−8 mol L−1 (S/N = 3). The imprinted electrochemical sensor was employed to determine phoxim in cucumber samples with recovery ranging from 98.06% to 101.13%. An adsorption model for the imprinted sensor was investigated, and the measured imprinting factor β of the sensor was found to be 7.23, with the binding rate constant k being 14.2247 s. The developed electrochemical sensor based on the graphene modified electrode and the molecularly imprinted polymer exhibited good repeatability and stability, and can be successfully used to determine phoxim in cucumber samples.

Electrochemical Sensor for the Determination of Theophylline Based on Molecularly Imprinted Polymer with Ethylene Glycol Maleic Rosi- nate Acrylate as Cross-linker

A novel electrochemical sensor for the determination of theophylline based on ethylene glycol maleic rosinate acrylate as the cross linking agent and acrylic acid as functional monomer was fabricated by molecularly imprinted technology. A molecularly imprinted polymers (MIPs) membrane was synthesized on the surface of a glassy carbon electrode in vacuum drying oven by free radical polymerization method. The electrochemical behavior of the membrane was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry. Under optimum conditions, it was found that the response of peak currents was linear to the concentration of theophylline in range of 2.00×10

Selective separation and determination of glucocorticoids in cosmetics using dual-template magnetic molecularly imprinted polymers and HPLC

Molecularly imprinting polymers (MIPs) are typically prepared using a single template molecule, which allows selective separation and enrichment of only one target analyte. It is not suitable for determination of complex real samples containing multiple analytes. In order to expand the practical application of imprinted polymers, novel dual-template magnetic molecularly imprinted polymers (MMIPs) were synthesized by surface polymerization using hydrocortisone and dexamethasone as the dual-template molecules in this study. The dual-template MMIPs were prepared by copolymerization on the surface of Fe3O4@ SiO2-NH2, the template molecules, the functional monomer acrylamide (AM), the cross-linking agent ethylene glycol dimethacrylate (EGDMA), and the initiator 2,2-azobisisobutyronitrile. The morphology, magnetic properties and adsorption characteristics of the obtained dual-template MMIPs were studied by field emission scanning electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, thermal gravimetric analysis, and vibrating sample magnetometry, and re-binding experiments. The results indicated that dual-template MMIPs had uniform particle size, strong magnetic properties, high thermal stability, and good mass transfer rate. To investigate the selectivity of dual-template MMIPs, the template molecules were mixed along with their structural analogs. The dual-template MMIPs revealed a significantly higher adsorption amount for the template molecule than its structure analog. The dual-template MMIPs can be used for the enrichment and determination of hydrocortisone and dexamethasone in cosmetic products with the recoveries of spiked cosmetic samples ranging from 86.8-107.5% and 91.2-104.3%, respectively. The relative standard deviation (RSD) for hydrocortisone was <2.89%, and RSD for dexamethasone was <2.62%.

Adsorption of phenolic compounds from water by a novel ethylenediamine rosin-based resin: Interaction models and adsorption mechanisms

This study describes the adsorption performance of a novel ethylenediamine rosin-based resin (EDAR) for several industrially-important phenolic compounds. Its removal of 4-nitrophenol (4-NP) from water was comparable to or better than many commercial resins, although it was less effective with other phenols (i. e., phenol, 2,4-dichlorophenol, 4-chlorophenol, and 4-methylphenol). Experimental conditions for batch adsorption of 4-NP by EDAR are evaluated, the adsorption kinetics is well described by the pseudo-second-order model (R2 > 0.99) and isotherm follows the Langmuir isotherm model (R2 > 0.99), with the maximum monolayer adsorption capacity of 82 mg g-1 at pH 6.0 and 293 K. The thermodynamic parameters indicate that the adsorption is spontaneous and endothermic. Also, quantum chemistry calculations indicate involvement of hydrogen-bonding between 4-NP and amino groups of EDAR. 4-NP was efficiently desorbed from the loaded EDAR resin by 0.2 M HCl, and the resin could be recycled with only a small decrease in its initial adsorption capacities. Thus, EDAR is a promising adsorbent for the removal of 4-NP during water treatment.

Performance of a zeolite modified with N,N-dimethyl dehydroabietylamine oxide (DAAO) for adsorption of humic acid assessed in batch and fixed bed columns

Factors that affect adsorption of a synthetic humic acid (HA) on a zeolite modified with the surfactant N,N-dimethyl dehydroabietylamine oxide (DAAO) (SMZ) were investigated in batch and fixed bed column experiments. Adsorption increased with increasing HA concentrations and contact time, but decreased with increasing pH, temperature, and ionic strength. Adsorption of HA on SMZ was increased by the presence of the cations Ca2+ and Mg2+, whereas anions such as NO3−, HCO3−, SO42−, and PO43− showed the opposite trend, and competed with HA adsorption. HA adsorption on SMZ was well-fitted by pseudo-second order kinetics, and described by the Langmuir isotherm model. The maximum adsorption capacity in batch experiments calculated from the Langmuir adsorption isotherm was about 126 mg g−1. Thermodynamic calculations showed that HA adsorption on the zeolite with bilayer DAAO coverage was spontaneous and exothermic. Optimum desorption was obtained using 0.1 M NaOH with a recovery of 94%. The HA adsorption capacity of SMZ at the breakthrough point was greatly influenced by bed depth, and could be described by the Thomas model. Adsorption mechanisms are interpreted as involving mainly hydrogen bonding and electrostatic interactions.

Synthesis, surface properties and temperature dependence of phase separation of DSPE chains in ethanol solutions

A novel renewable dehydroabietic acid trimethylolpropane ester (DATE) and a dehydroabietic-based succinic acid polyester (DSPE) were successfully prepared in a facile way. Various analytical techniques were employed to evaluate the chemical structure of the ester and the polymer. The monomer and the polymer can form stable micelles at low critical micelle concentrations (CMCs), and the CMC values are 0.0026 and 0.0019 mg mL−1 for DATE and DSPE in ethanol, respectively. In addition, the aggregation and dissociation of DSPE chains in ethanol solutions during one cycle of the heating and cooling process were detected. The results indicated that DSPE chains aggregate during cooling. In contrast, during heating, the aggregates dissociated gradually and distinct hysteresis occurred. Moreover, the kinetics of phase separation of the DSPE/ethanol solution was monitored, and the apparent activation energy of phase separation of the DSPE/ethanol solution was estimated by kinetics analysis. The results showed that DSPE with a low CMC and temperature-dependent behavior may have tremendous scope as a drug carrier in the area of controlled drug delivery.