Guofan Wu

Determination of malachite green in fish based on magnetic molecularly imprinted polymer extraction followed by electrochemiluminescence.

A novel procedure for selective extraction of malachite green (MG) from fish samples was set up by using magnetic molecularly imprinted polymers (MMIP) as the solid phase extraction material followed by electrochemiluminescence (ECL) determination. MMIP was prepared by using Fe3O4 magnetite as magnetic component, MG as template molecule, methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent. MMIP was characterized by SEM, TEM, FT-IR, VSM and XRD. Leucomalachite green (LMG) was oxidized in situ to MG by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). And then MMIP was successfully used to selectively enrich MG from fish samples. Adsorbed MG was desorbed and determined by ECL. Under the optimal conditions, calibration curve was good linear in the range of 0.29-290 μg/kg and the limit of detection (LOD) was 7.3 ng/kg (S/N=3). The recoveries of MMIP extraction were 77.1-101.2%. In addition, MMIP could be regenerated. To the best of our knowledge, MMIP coupling with ECL quenching of Ru(bpy)3(2+)/TPA for the determination of MG has not yet been developed.

A Novel Amperometric Sensor for Salicylic Acid Based on Molecularly Imprinted Polymer-Modified Electrodes

A novel electrochemical MIP-sensor for salicylic acid (SA) has been synthesized firstly by electropolymerizing o-phenylenediamine on glassy carbon electrode in presence of template molecule (salicylic acid). The response of the sensor to SA is investigated by square wave voltammetry (SWV). The linearity is obtained over a concentration range of 6 × 10−5 ∼ 1 × 10−4 mol/L (R2 = 0.9961). And the detection limit of SA is about 2 × 10−5 mol/L. The sensor exhibits good selectivity for salicylic acid by virtue of the interaction between molecularly imprinted binding sites and the template.

Quenching of the electrochemiluminescence of Ru(bpy)32+/TPA by malachite green and crystal violet

Efficient and stable quenching of electrochemiluminescence of Ru(bpy)3(2+)/TPA by malachite green(MG) and crystal violet(CV) at the glass carbon (GC) electrode is reported. A novel quenching mechanism has been proposed. Resonance energy transfer from the excited-state luminophore Ru(bpy)3(2+*) to MG/CV and dynamic quenching are suggested as the mechanism for quenching ECL. The quenching mechanism is discussed in detail based on UV-visible absorption spectra, cyclic voltammograms, ECL curves and fluorescence methods. MG shows more efficient quenching than CV. Moreover, the quenched ECL intensity versus the concentration of MG and CV are linear over the concentration ranges of 8 × 10(-10)-8 × 10(-7)M and 3.46 × 10(-9)-5.5 × 10(-7)M, respectively. The corresponding limit of detection (LOD) was 1.0 × 10(-10)M for MG and 1.1 × 10(-10)M for CV (S/N=3).

Electrochemical detection of β-1,3-glucanase gene from transgenic capsicums using asymmetric PCR generated by a detecting probe and an anchoring probe

A design for recognition of beta-1,3-glucanase gene (Glu) specific sequence based on probe extension was described. The detecting probe DNA and the anchoring prober were hybridized with the same target DNA firstly, then the probes were extended by DNA polymerase reaction. After that the double strand DNA was denatured, and the extended detecting probe was immobilized on a glassy carbon electrode via nanoparticle gold (AuNP). In electrochemical detection (cyclic voltammetry, CV and differential pulse voltammetry, DPV), an increased peak current (i(p)) of the indicator (methylene blue, MB) was obtained compared with the probe without extension. Three differently long DNAs of Glu specific sequence were employed as the target: oligonucleotide acid, molecular cloning vector DNA and total genome DNA of transgenic capsicum. The estimated DPV detection limits for three targets of oligonucleotide, the molecular cloning vector DNA and genome DNA were 2.6x10(-13), 6.0x10(-13) and 8.0x10(-13)moll(-1) respectively.

An Electrochemical Assay of β-1,3-Glucanase Gene from Transgenic Capsicum Using Asymmetric PCR

5′-Thiol-derivatized specific DNA probes were added to the single primer polymerase chain reaction (asymmetric PCR) solution. In the PCR process, the DNA probes extended in the presence of target; the extended probes were then immobilized on a glassy carbon electrode (GCE) via gold nanoparticles. Finally, methylene blue and the extended probes were combined and the electrochemical signals were measured. This signal was higher than that of the GCE modified only by the original probe. When there was no target in PCR solution, the probe did not extend and the signal did not increase. The specific sequences of the β-1,3-glucanase gene were detected successfully from three targets with different length: oligonucleotide, molecule clone vector DNA, and total genome DNA of transgenic capsicum. The detection limits of 2.6 × 10−13, 7.8 × 10−13, and 9.1 × 10−13 moll−1 for oligonucleotide, molecule clone vector DNA, and total transgenic capsicum genome DNA were estimated.

Development and application of the tartrazine voltammetric sensors based on molecularly imprinted polymers

ABSTRACT A modified glassy carbon electrode was prepared as an electrochemical voltammetric sensor based on molecularly imprinted polymer film for tartrazine (TT) detection. The sensitive film was prepared by copolymerization of tartrazine and acrylamide on the carbon nanotube-modified glassy carbon electrode. The performance of the imprinted sensor was investigated by cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy in detail. Under the optimum conditions, two dynamic linear ranges of 8 × 10−8 to 1 × 10−6 mol L−1 and 1 × 10−6 to 1 × 10−5 mol L−1 were obtained, with a detection limit of 2.74 × 10−8 mol L−1(S/N = 3). This sensor was used successfully for tartrazine determination in beverages.

(Z)-4-Bromo-N-{(Z)-3-[(4-bromo-2,6-diisopropyl­phen­yl)imino]­butan-2-yl­idene}-2,6-diisopropyl­aniline

The title compound, C28H38Br2N2, is centrosymmetric with the mid-point of the central C—C bond of the butyl group located on an inversion center. The terminal benzene ring is approximately perpendicular to the central 1,4-diazabutadiene mean plane [dihedral angle = 78.23 (3)°]. No hydrogen bonding or aromatic stacking is observed in the crystal structure.