Shouguo Wu

Selective Determination of Uric Acid by Using a β-Cyclodextrin Modified Electrode

A β-cyclodextrin (CD) modified poly(N-acetylaniline) (PNAANI) glassy carbon electrode (GCE) was used to study the electrode reaction of uric acid (UA). The formation of a supramolecular complex between β-CD and UA improves the sensitivity and selectivity of the UA determination. The mechanism of selective detection of UA at the β-CD/PNAANI/GCE is proposed. Also, an analytical procedure involving square-wave voltammetry has been developed for determination of UA in the concentration range 1.0×10−5 to 2.0×10−4 mol dm−3.

Continuous wavelet transform and its application to resolving and quantifying the overlapped voltammetric peaks

In order to resolve and quantify the overlapped peaks of voltammetry that can be described by sech2-function, continuous wavelet transform (CWT) is employed. Through CWT by using Marr wavelet, qualitative and quantitative analysis for the mixed solution of Cd(II) and In(III) can be performed from unresolved square wave voltammogram (SWV) and relevant theoretical basis is provided. A new method to construct the baseline for quantitative determination is also proposed. The results of analysis indicate that the overlapped voltammogram can be resolved and quantified effectively, conveniently and satisfactorily via CWT.

Selective determination of dopamine in the presence of ascorbic acid at an over-oxidized poly(N-acetylaniline) electrode

An over-oxidized poly(N-acetylaniline) (PNAANI)/GCE was used to determine dopamine (DA) in a large excess of ascorbic acid (AA) by differential pulse voltammetry. A linear relation between Ip and DA concentration was found over the range 5.0 x 10(-7) to 2.0 x 10(-5) M. The detection limit was 1.68 x 10(-8) M for S/N = 3 and 400 microM AA did not interfere with the DA determination. The high sensitivity was due to accumulation and selectivity was due to charge discrimination. The mechanism of selective determination of DA at over-oxidized PNAANI/GCE was also proposed.

Selective detection of uric acid in the presence of ascorbic acid at physiological pH by using a β-cyclodextrin modified copolymer of sulfanilic acid and N-acetylaniline

A beta-cyclodextrin (CD) modified copolymer membrane of sulfanilic acid (p-ASA) and N-acetylaniline (SPNAANI) on glassy carbon electrode (GCE) was prepared and used to determine uric acid (UA) in the presence of a large excess of ascorbic acid (AA) by differential pulse voltammetry (DPV). The properties of the copolymer were characterized by X-ray photoelectron spectra (XPS) and Raman spectroscopy. The oxidation peaks of AA and UA were well separated at the composite membrane modified electrode in phosphate buffer solution (PBS, pH 7.4). A linear relationship between the peak current and the concentration of UA was obtained in the range from 1.0 x 10(-5) to 3.5 x 10(-4)mol L(-1), and the detection limit was 2.7 x 10(-6)mol L(-1) at a signal-to-noise ratio of 3. Two hundred and fifty-fold excess of AA did not interfere with the determination of UA. The application of the prepared electrode was demonstrated by measuring UA in human serum samples without any pretreatment, and the results were comparatively in agreement with the spectrometric clinical assay method.

Flip shift subtraction method: a new tool for separating the overlapping voltammetric peaks on the basis of finding the peak positions through the continuous wavelet transform

Abstract To separate the overlapping voltammetric peaks that can be described by the sech2-function, a new method, flip shift subtraction method (FSSM), is proposed. It is built on the basis of finding the peak positions using the Marr wavelet through the continuous wavelet transform (CWT). A corresponding theory, which possesses a general meaning, is presented as a basis of finding the peak positions. To guarantee the accuracy of FSSM, an algorithm, crossed iterative algorithm of continuous wavelet transform and original signal (CIACWTOS), is built on to locate the refined peak positions. Meanwhile, the theoretical errors on peak areas caused by FSSM are discussed.

A high-sensitive and fast-fabricated glucose biosensor based on Prussian blue/topological insulator Bi2Se3 hybrid film

A novel and fast-fabricated Prussian blue (PB)/topological insulator Bi(2)Se(3) hybrid film has been prepared by coelectrodeposition technique. Taking advantages of topological insulator in possessing exotic metallic surface states with bulk insulating gap, Prussian blue nanoparticles in the hybrid film have smaller size as well as more compact structure, showing excellent pH stability even in the alkalescent solution of pH 8.0. Based on the Laviron theory, the electron transfer rate constant of PB/Bi(2)Se(3) hybrid film modified electrode was calculated to be 4.05 ± 0.49 s(-1), a relatively big value which may be in favor of establishing a high-sensitive biosensor. An amperometric glucose biosensor was then fabricated by immobilizing glucose oxidase (GOD) on the hybrid film. Under the optimal conditions, a wide linear range extending over 3 orders of magnitude of glucose concentrations (1.0 × 10(-5)-1.1 × 10(-2)M) was obtained with a high sensitivity of 24.55 μA mM(-1) cm(-2). The detection limit was estimated for 3.8 μM defined from a signal/noise of 3. Furthermore, the resulting biosensor was applied to detect the blood sugar in human serum samples without any pretreatment, and the results were comparatively in agreement with the clinical assay.

Electrochemical Studies on the Oxidation of Thymineat β‐Cyclodextrin Modified Electrode

β-Cyclodextrin (CD)-modified poly-N-acetylaniline (PNAANI) electrode is used to study the redox reaction of thymine. The characteristics of a supramolecular inclusion complex between β-CD and thymine is examined. The mechanism of thymine oxidation is proposed. A nontoxic, stable, and convenient method of square-wave voltammetry for the measurement of thymine in the concentration range of 2.5×10−5 mol/L to 1.0×10−3 mol/L has been developed.

Development of wavelet transform voltammetric analyzer

An on-line wavelet transform algorithm and development of voltammetric analyzer with the on-line wavelet transform (WT-voltammetric analyzer) are described. Because the on-line wavelet transform decomposes the sampled signal simultaneously with the progress of sampling, the WT-voltammetric analyzer gives all the components contained in the sampled voltammogram. Applications of the WT-voltammetric analyzer in linear sweep voltammetric analysis of mixtures of Pb(II) and Tl(I) and in square wave voltammetric analysis of mixture of Cd(II) and In(III) were investigated. Results showed that the overlapping peaks of Pb(II) and Tl(I) can be separated easily, and the peak position after the on-line wavelet transform does not change. The linearity of the calibration curves for Cd(II) and In(III) in the overlapping square wave voltammetric curves were kept after the on-line wavelet transform. Quantitative determination of Cd(II) and In(III) in mixture samples were investigated. The recoveries are between 92.5 and 107.1%.

AMPEROMETRIC MICRO-BIOSENSOR ARRAY FOR CHOLINE AND ACETYLCHOLINE BASED ON A GLASSY CARBON ELECTRODE MODIFIED BY PLATINUM-BLACK PARTICLES AND A CO-CROSSLINKED ENZYME SYSTEM

A glassy carbon electrode was first modified by electro-depositing sub-micrometer platinum black particles on the surface. An acetylcholine micro-biosensor array and a choline micro-biosensor array were fabricated based on immobilization of acetylcholineasterase-choline oxidase or choline oxidase by cross-linking with glutaraldehyde on the Pt-black/GCE. Significant enhancement in performances of these biosensors was achieved. The chronoamperometric response of the acetylcholine micro-biosensor array gave a linear relation in the range of 29 to 1200μmol/L and a detection limit of 8.7μmol/L acetylcholine. The amperometric response of the choline micro-biosensor array gave a linear relation in the range of 24 to 1000μmol/L and a detection limit of 7.4μmol/L choline. They also possessed very good stability and reproducibility for long-term use.

Electrocatalytic Oxidation of Saccharides at MoOx/AuNPs Modified Electrode Towards Analytical Application

The MoO x /AuNPs composite film modified glassy carbon electrode was fabricated by electro-depositing simultaneously gold nanoparticles and molybdenum oxides using cyclic voltammetry. The morphology and topography of the MoO x /AuNPs composite were characterized by scan electron microscopy and X-ray photoelectron spectroscopy respectively, and the electrocatalytic oxidation of glucose at the MoO x /AuNPs composite film was investigated and analyzed in detail. It was shown that the MoO x /AuNPs composite was of strong electrocatalytic activity towards oxidation of glucose as well as other saccharides, so that an attempt was made for direct voltammetric determination of glucose. Then the positive scan polarization reverse catalytic voltammetry was proposed for the first time. Based on this method, the pure oxidation current was extracted by subtraction of the blank current in the reverse scan. The current sensitivity was enhanced tremendously and the signal to noise ratio was improved adequately. The electrocatalytic oxidation of glucose at the MoO x /AuNPs modified electrode was performed in alkaline medium, a wide linear range from 0.01 mmol/L to 4.0 mmol/L of glucose, a higher current sensitivity of 2.35 mA/(mmol/L·cm2), and a lower limit of detection of 9.01 µmol/L (at signal/noise=3) were achieved. In addition, the electrocatalytic oxidation of other saccharides such as lactose, fructose and sucrose was also evaluated.