Yusun Zhou

Highly selective and sensitive determination of dopamine by the novel molecularly imprinted poly(nicotinamide)/CuO nanoparticles modified electrode.

A novel electrochemical sensor was proposed for the determination of dopamine (DA) based on the molecularly imprinted electropolymers (MIPs)/copper oxide (CuO) nanoparticles modified electrode. MIPs were firstly prepared by using nicotinamide as an environment-friendly monomer to selectively recognize the template molecules. CuO nanoparticles were used to enhance the number of imprinted sites per unit surface area of the electrode and then improve the selectivity and sensitivity of the electrochemical sensor. Thus, the obtained electrochemical sensor could effectively minimize the interferences caused by ascorbic acid (AA), uric acid (UA) and sample matrix. The linear range for the detection of DA was changed from 0.02 μmol L(-1) to 25 μmol L(-1) with the detection limit of 8 nmol L(-1) (S/N=3), which was lower than those of the reported MIPs-based sensor. Finally, the proposed method was applied to measure dopamine in serum samples. The spiked recoveries were changed from 96.9% to 105.9% and the RSD was not higher than 8.8%. It was shown that the proposed sensor exhibited significant promise as a reliable technique for the detection of DA in human serum samples.

Rapid and selective extraction of multiple macrolide antibiotics in foodstuff samples based on magnetic molecularly imprinted polymers

Magnetic molecularly imprinted polymers (MMIPs) were prepared based on surface molecular imprinting using erythromycin (ERY) as template molecule and Fe3O4 nanoparticles as support substrate. The MMIPs possessed high adsorption capacity of 94.1 mg/g for ERY and the imprinting factor was 11.9 indicating good imprinted effect for ERY. Selective evaluation demonstrated favorable selectivity of MMIPs for multiple macrolide antibiotics (MACs). Using MMIPs as adsorptive material, a rapid and convenient magnetic solid-phase extraction (MSPE) procedure was established for simultaneous and selective separation of six MACs in pork, fish and shrimp samples, then the MACs was subjected to high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis. At different fortified concentrations, the extraction recoveries could reach 89.1% and the relative standard deviations were lower than 12.4%. Chromatogram revealed the response signals of MACs in spiked samples were greatly enhanced and matrix interferences were effectively eliminated after treatment with MSPE. The proposed MSPE procedure coupled with HPLC-UV realized selective and sensitive determination of multiple MACs in foodstuff samples.

Determination of trace 2,4-dinitrophenol in surface water samples based on hydrophilic molecularly imprinted polymers/nickel fiber electrode.

A rapid, sensitive and selective electrochemical method was proposed for the determination of 2,4-dinitrophenol (2,4-DNP) in surface water samples, using hydrophilic molecular imprinted polymers (MIPs) as the recognition element and nickel (Ni) fiber as the catalytic element. Hydrophilic MIPs were synthesized using 2,4-DNP as the template, acrylamide as the monomer, glycidilmethacrylate as the pro-hydrophilic co-monomer and acetonitrile as the solvent. Hydrophilic modification could enhance the accessibility of 2,4-DNP to the imprinted cavities and improve the selective recognition properties of traditional MIPs in water medium. Subsequently, hydrophilic MIPs/Ni fiber electrode was prepared to determine trace 2,4-DNP by cyclic voltammetry. The parameters affecting the analytical performance were investigated. Under optimized conditions, the linear range was 0.7-30 μg L⁻¹ and the detection limit was 0.1 μg L⁻¹. Finally, the proposed method was applied to measure 2,4-DNP in surface water samples. The spiked recoveries were changed from 91.3% to 102.6% and the RSD was not higher than 5.1%. There was no statistically significant difference between the results obtained by the proposed method and the traditional chromatographic method.

A simple and sensitive immunoassay for the determination of human chorionic gonadotropin by graphene-based chemiluminescence resonance energy transfer

In this study, we report a strategy of chemiluminescence resonance energy transfer (CRET) using graphene as an efficient long-range energy acceptor. Magnetic nanoparticles were also used in CRET for simple magnetic separation and immobilization of horseradish peroxidase (HRP)-labeled anti-HCG antibody. In the design of CRET system, the sandwich-type immunocomplex was formed between human chorionic gonadotropin (HCG, antigen) and two different antibodies bridged the magnetic nanoparticles and graphene (acceptors), which led to the occurrence of CRET from chemiluminescence light source to graphene. After optimizing the experimental conditions, the quenching of chemiluminescence signal depended linearly on the concentration of HCG in the range of 0.1 mIU mL(-1)-10 mIU mL(-1) and the detection limit was 0.06 mIU mL(-1). The proposed method was successfully applied for the determination of HCG levels in saliva and serum samples, and the results were in good agreement with the plate ELISA with colorimetric detection. It could also be developed for detection of other antigen-antibody immune complexes by using the corresponding antigens and respective antibodies.

Occurrence investigation of perfluorinated compounds in surface water from East Lake (Wuhan, China) upon rapid and selective magnetic solid-phase extraction

Using a novel magnetic nanocomposite as adsorbent, a convenient and effective magnetic solid-phase extraction (MSPE) procedure was established for selective separation and concentration of nine perfluorinated compounds (PFCs) in surface water sample. Then an ultra high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) system was employed for detection of PFCs. Good linearity of the developed analytical method was in the range of 0.5–100 ng L−1 with R2 > 0.9917, and the limits of detection (LODs) ranged from 0.029 to 0.099 ng L−1. At three fortified concentrations of 0.5, 5 and 50 ng L−1, the spiked recoveries of PFCs were in the range of 90.05–106.67% with RSDs < 12.62% (n = 3). The proposed analytical method was applied for determination of PFCs in surface water from East Lake (Wuhan, China). The total concentrations of nine PFCs ranged from 30.12 to 125.35 ng L−1, with perfluorooctane sulfonate and perfluoroctanoic acid as the most prevalent PFCs, and the greatest concentrations of PFCs were observed in Niuchao lakelet. The concentrations of the PFCs (C ≥ 11) were mostly less than the limits of quantification (LOQs), attributed to the possibility that the more hydrophobic long-chain PFCs are potential to accumulate in sediment and aquatic biota.

A nano-nickel electrochemical sensor for sensitive determination of chemical oxygen demand

Nano-nickel particles (nano-Ni) were electrodeposited on the surface of a glassy carbon (GC) electrode under −0.9 V for 25 min, and then used to construct an electrochemical sensor for sensitive determination of chemical oxygen demand (COD). The parameters such as electrolyte, deposition potential, deposition time and surface morphology were investigated. It was shown that nano-Ni film with high electrocatalytic activity was stably modified on the surface of the GC electrode, which could be used to effectively oxidize a wide spectrum of organic compounds. Under optimized conditions, the linear range was 10–1533 mg L−1 and the detection limit was as low as 1.1 mg L−1. Subsequently, this sensor was used to detect the COD values of different water samples and the results were linearly correlated to those by the classic dichromate method (R = 0.9493, p < 0.01, n = 54). This confirmed the reliability and practicality of the proposed method in the determination of COD in various water samples.

Fabrication of a Selective and Sensitive Sensor Based on Molecularly Imprinted Polymer/Acetylene Black for the Determination of Azithromycin in Pharmaceuticals and Biological Samples

A new selective and sensitive sensor based on molecularly imprinted polymer/acetylene black (MIP/AB) was developed for the determination of azithromycin (AZM) in pharmaceuticals and biological samples. The MIP of AZM was synthesized by precipitation polymerization. MIP and AB were then respectively introduced as selective and sensitive elements for the preparation of MIP/AB-modified carbon paste (MIP/ABP) electrode. The performance of the obtained sensor was estimated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Compared with non-molecularly imprinted polymer (NIP) electrodes, NIP/ABP electrodes, and MIP-modified carbon paste electrodes, MIP/ABP electrode exhibited excellent current response toward AZM. The prepared sensor also exhibited good selectivity for AZM in comparison with structurally similar compounds. The effect of electrode composition, extraction parameters, and electrolyte conditions on the current response of the sensor was investigated. Under the optimized conditions, the prepared sensor showed two dynamic linear ranges of 1.0 × 10−7 mol L−1 to 2.0 × 10−6 mol L−1 and 2.0 × 10−6 mol L−1 to 2.0 × 10−5 mol L−1, with a limit of detection of 1.1 × 10−8 mol L−1. These predominant properties ensured that the sensor exhibits excellent reliability for detecting AZM in pharmaceuticals and biological fluids without the assistance of any separation techniques. The results were validated by the high-performance liquid chromatography–tandem mass spectrometry method.