Xiaoya Hu

Poly(amidosulfonic acid) modified glassy carbon electrode for determination of isoniazid in pharmaceuticals.

Amidosulfonic acid was electropolymerized by cyclic voltammetry onto the surface of glassy carbon electrode (GCE) to fabricate the chemically modified electrode, which showed high stability, good selectivity and reproducibility for determination of isoniazid. The modified electrode showed an excellent electrocatalytical effect on the oxidation of isoniazid. Under the optimum conditions, there was a good linear relationship between anodic peak current and isoniazid concentration in the range of 5.0 x 10(-8)- 1.0 x 10(-5) M, and a detection limit of 1.0 x 10(-8) M (S/N = 3) was obtained after 120 s at the accumulation potential of - 0.2 V (vs. SCE). This developed method had been applied to the direct determination of isoniazid in injection and tablet samples with satisfactory results.

Determination of Isoniazid Using a Gold Electrode by Differential Pulse Voltammetry

Abstract Compared with the present electrochemical method of determining isoniazid (INH) content by polarography using a hanging mercury electrode, using a gold electrode for determination of isoniazid as proposed by this paper has substantial advantages of convenience, sensitivity, and no pollution. An irreversible anodic peak at ca. −0.3V vs SCE of INH in 0.5xa0M NaOH was used for quantitative determination of INH by cyclic voltammetry (CV) or differential pulse voltammetry (DPV). The peak current showed a linear dependence with INH concentration over the range 2.0×10−6–2.3×10−4 M by DPV with the detection limit of 9.69×10−8xa0mol/L. The proposed procedure was successfully applied to the assay of isoniazid tablets. The potential range of CV scan, pH, accumulation potential, accumulation time, interference, and possible response mechanism are also discussed.Abstract Compared with the present electrochemical method of determining isoniazid (INH) content by polarography using a hanging mercury electrode, using a gold electrode for determination of isoniazid as proposed by this paper has substantial advantages of convenience, sensitivity, and no pollution. An irreversible anodic peak at ca. −0.3V vs SCE of INH in 0.5 M NaOH was used for quantitative determination of INH by cyclic voltammetry (CV) or differential pulse voltammetry (DPV). The peak current showed a linear dependence with INH concentration over the range 2.0×10−6–2.3×10−4 M by DPV with the detection limit of 9.69×10−8 mol/L. The proposed procedure was successfully applied to the assay of isoniazid tablets. The potential range of CV scan, pH, accumulation potential, accumulation time, interference, and possible response mechanism are also discussed.

Determination of benorilate in pharmaceutical formulations and its metabolite in urine at carbon paste electrode modified by silver nanoparticles.

Benorilate was determined by the differential pulse voltammetry (DPV) using a carbon paste electrode modified by silver nanoparticles in 1.25x10(-3)moll(-1) KH(2)PO(4) and Na(2)HPO(4) buffer solution (pH=6.88, 25 degrees C) .The anodic peak potential was +0.970V (versus SCE). A good linear relationship was realized between the anodic peak currents and benorilate concentrations in the range of 1.0x10(-7) to 2.5x10(-4)moll(-1) with the detection limit of 1.0x10(-8)moll(-1). The recovery was 95.2-103.6% with the relative standard deviation of 3.6% (n=9). The pharmaceutical preparations, benorilate tablets samples and its metabolite (salicylic acid) in urine were determined with the desirable results.

Differential pulse adsorption voltammetry for determination of procaine hydrochloride at a pumice modified carbon paste electrode in pharmaceutical preparations and urine

Procaine hydrochloride was determined by the differential pulse voltammetry (DPV) using a 6% (m/m) pumice modified carbon paste electrode in 1.25 x 10(-3) mol x l(-1) KH(2)PO(4) and Na(2)HPO(4) buffer solution (pH 6.88, 25 degrees C). The anodic peak potential used was +0.980 V (vs. SCE). A good linear relationship was realized between the anodic peak current and procaine concentration in the range of 9.0 x 10(-7)-2.6 x 10(-5) mol x l(-1) with the detection limit of 5.0 x 10(-8) mol x l(-1). The recovery was 95.2-104.8% with the relative standard deviation of 3.2% (n=10). The pharmaceutical preparations, procaine hydrochloride injection and the urine samples were determined with the desirable results.

Ni and NiO Nanoparticles Decorated Metal–Organic Framework Nanosheets: Facile Synthesis and High-Performance Nonenzymatic Glucose Detection in Human Serum

Ni-MOF (metal-organic framework)/Ni/NiO/carbon frame nanocomposite was formed by combing Ni and NiO nanoparticles and a C frame with Ni-MOF using an efficient one-step calcination method. The morphology and structure of Ni-MOF/Ni/NiO/C nanocomposite were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and energy disperse spectroscopy (EDS) mapping. Ni-MOF/Ni/NiO/C nanocomposites were immobilized onto glassy carbon electrodes (GCEs) with Nafion film to construct high-performance nonenzymatic glucose and H2O2 electrochemical sensors. Cyclic voltammetric (CV) study showed Ni-MOF/Ni/NiO/C nanocomposite displayed better electrocatalytic activity toward glucose oxidation as compared to Ni-MOF. Amperometric study indicated the glucose sensor displayed high performance, offering a low detection limit (0.8 μM), a high sensitivity of 367.45 mA M-1 cm-2, and a wide linear range (from 4 to 5664 μM). Importantly, good reproducibility, long-time stability, and excellent selectivity were obtained within the as-fabricated glucose sensor. Furthermore, the constructed high-performance sensor was utilized to monitor the glucose levels in human serum, and satisfactory results were obtained. It demonstrated the Ni-MOF/Ni/NiO/C nanocomposite can be used as a good electrochemical sensing material in practical biological applications.

Gold microspheres modified with octadecanethiol for capillary liquid chromatography

Monodispersed spherical gold particles synthesized and modified with n-octadecanethiol (C18-Au) were packed into a 100 microm I.D. capillary column and tested in capillary high-performance liquid chromatography (microHPLC). To the best of our knowledge, this represents the first report on the actual use of micron gold particles as stationary phase in a packed column microHPLC. As measured by scanning electron microscopy, the average diameter of these gold microspheres was 3.5 microm and the surface area, average pore diameter, and average pore volume were 49.4m(2)/g, 4.8 nm, and 0.12 cm(3)/g, respectively. The retention behavior of neutral compounds on the n-octadecanethiol-modified gold microspheres was investigated by separating a mixture of small organic compounds using microHPLC. The results from the experiments show that C18-Au behaves basically as a reversed phase. The test of chemical stability of the C18-Au stationary phase under alkaline condition demonstrates that it is stable with the flushing of a mobile phase at pH 12 for at least 140 h. The C18-Au particles are also mechanically strong enough to withstand pressure up to 52 MPa. The preliminary results in this work prove the feasibility of the fabrication of C18-Au micron particles as a novel stationary phase for packed column microHPLC.

Fabrication of nanometre-sized platinum electrodes by controllable electrochemical deposition

A new and simple method for fabricating controllable insulated nanometer-sized platinum electrodes is presented. Electrochemical etching of platinum wire is employed, and then a repeated process of cycle voltammetric deposition of electrophoretic paint and heat curing for shrink film follows which effectively controls the size of the nanoelectrodes, which is different from previous DC electrolysis deposition. This technique allows complete insulation of the whole body of the etched platinum wire, except for the very tip with the shrink film during heat curing of the film, leaving an electrochemical active area with effective diameters of nanometers. The process overcomes the pinhole formation resulting from the electrophoretic paint deposition process. The size of the platinum electrodes and the thickness of the deposed paint for insulation can be properly controlled and reproduced. The fabricated electrodes show ideal steady-state voltammetric behaviors from which the effective areas of the nanoelectrodes are measured. The effective radius of the prepared nanoelectrodes ranges from 3.1nm to hundreds of nanometers.

DIFFERENTIAL PULSE VOLTAMMETRY FOR DETERMINATION OF PARACETAMOL AT A PUMICE MIXED CARBON PASTE ELECTRODE

A method for determination of paracetamol is established by the differential pulse voltammetry (DPV) using a pumice mixed carbon paste electrode with the pumice weight percent of 6% (m/m) in 0.1 mol l−1 H2SO4. The anodic peak potential is ca. 0.640 V (vs. SCE). There is a good linear relationship between the peak current and paracetamol concentration in the range of 6.0 × 10−8 – 1.0 × 10−6 mol l−1, and 2.0 × 10−6 – 9.8 × 10−5 mol l−1 with the detection limit of 2.0 × 10−8 mol l−1. Compared with the carbon paste electrode, the detection limit of this method decreases two orders of magnitude. This method is rapid, simple, accurate and highly sensitive. Satisfactory results for determination of paracetamol in pharmaceutical preparations and urine are obtained.

Metal/Graphitic Carbon Nitride Composites: Synthesis, Structures, and Applications

Graphitic carbon nitride (g-C3 N4 ) has been widely used in fields related to energy and materials science. However, nanostructured g-C3 N4 photocatalysts synthesized by traditional thermal polycondensation methods have the disadvantage of small specific surface areas and wide band gaps; these limit the catalytic activity and application range of g-C3 N4 . Based on the unique nanostructure of g-C3 N4 , it is a feasible method to modify g-C3 N4 with metals to design novel metal-semiconductor composites. Metals alter the photochemical properties of g-C3 N4 , in particular, narrow the band gap and expand photoabsorption into the visible range, which improves the photocatalytic performance. This review covers recent progress in metal/g-C3 N4 nanocomposites for photocatalysts, organic systems, biosensors, and so on. The aim is to summarize the synthetic methods, nanostructures, and applications of metal/g-C3 N4 nanocomposite materials, as well as discuss future research directions in these areas.

Construction of a non-enzymatic glucose sensor based on copolymer P4VP-co-PAN and Fe2O3 nanoparticles.

An electrochemical sensor based on a copolymer poly(4-vinylpyridine)-co-poly(acrylonitrile), P4VP-co-PAN, and Fe2O3 nanoparticle film modified glassy carbon electrode was developed for the determination of glucose. We studied the response of glucose with the proposed electrode, and determined the optimum conditions by changing the potential, pH and P4VP-co-PAN. The current response measurements were performed in PBS (c=0.1 M) with a potential of 0.7 V. The current response of this glucose sensor showed a linear relationship with the concentration in the range of 2.5 μM-0.58 mM (r=0.997). The experimental results demonstrate that this method has such merits as simple operation, low cost, high sensitivity, long term stability and good reproducibility, with satisfactory results.