A New Nitric Oxide Gas Sensor Based on Reticulated Vitreous Carbon/Nafion and Its Applications

Reticulated vitreous carbon (RVC), and Nafion membrane are used to fabricate a composition electrode to measure nitric oxide (NO) concentration amperometrically in the gas phase. Limit of detection was found to be 6 ppb at an applied voltage of 0.66 V (vs. mercury sulfate reference electrode) with average response time of less than 30 seconds. The response of the sensor was linearly dependent on the concentration over the whole tested range from 19 ppb‐50 ppm of NO. Simplicity in electrode fabrication and consistent performance between individual sensors make RVC and Nafion attractive materials for detecting very low levels of nitric oxide gas in routine analysis.     

纳米PbO2修饰电极电催化氧化性能的研究

利用旋转圆盘电极对纳米PbO2修饰电极的电催化氧化性能进行了初步的研究．实验表明由于电极表面PbO2晶粒呈纳米结构，使纳米PbO2修饰电极表面具有大的比表面积，高的表面活性中心，良好的导电性及宏观隧道效应，使得纳米PbO2修饰电极对苯酚有很好的氧化催化性能，用安培法测定了多种有机物在纳米PbO2修饰电极上的电流响应，实验表明，纳米PbO2修饰电极可以作为分析传感器用于有机化合物的测定中.     

Batch Injection Analysis Utilizing Modified Electrodes with Tetraruthenated Porphyrin Films for Acetaminophen Quantification

Batch injection analysis (BIA) utilizing amperometric detection with glassy carbon electrodes modified with [Co(TPyP){Ru(bipy)₂Cl}₄](TFMS)₅?H₂O porphyrin films were explored for acetaminophen analysis in pharmaceutical formulations. BIA is an interesting alternative for application of electrodes modified with tetraruthenated porphyrins. This sensor exhibited sharp current response peaks, rapid washout and excellent reproducibility for BIA‐amperometric quantification of acetaminophen. Also, a wide linear working range (10^?4 to 10^?6 mol L^?1) as well as high sensitivity and sampling frequency rate (detection limit=1.1×10^?7 mol L^?1, sampling frequency=120 injections/h) and a small volume of analysis (100 μL/injection) was achieved. Furthermore, the proposed method permits the direct quantification of acetaminophen in many pharmaceutical products, avoiding cumbersome processes as previous separations, solvent extraction or sample filtration. The new procedure was applied to the analysis of commercial pharmaceutical products and the results were in excellent agreement with the ones obtained by spectrophotometric method. Accordingly, this amperometric method showed to be very well suited for quality control analysis and other applications with similar requirements.     

Determination of the hydroxyl radical by its adduct formation with phenol and liquid chromatography/electrochemical detection

An HPLC-ECD method is described for the indirect determination of the hydroxyl (OH) radical. Fenton's reaction is used to produce OH, which simultaneously attacks phenols (phenol or pyrocatechol) to form the adducts, pyrocatechol or pyrogallic acid. Thus, [OH] quantification is based on the separation and detection of pyrogallic acid and/or pyrocatechol by an isocratic HPLC-ECD method. The quantification of OH is also performed alternatively by a chronoamperometric detection in an electrochemical cell, where simultaneously formed Fe^III (Fenton's reaction) combines [Fe^II(CN)₆]⁴⁻ to produce the Prussian blue (PB) molecules (Fe₄^III[Fe^II(CN)₆]₃). Newly formed PB molecules are then immediately converted to colorless Everitts salt (K₄Fe₄^II[Fe^II(CN)₆]₃) with the reduction of the high-spin Fe^III to Fe^II at the surface of a glassy carbon electrode at +0.150 V (versus Ag/AgCl). The calculated concentration of OH during incubation (0.626 ppm) can be detected with negative errors by the HPLC-ECD (0.595 and 0.615 ppm with the errors −5.2 and −1.8%, respectively) and by the chronoamperometric method (0.552 and 0.607 ppm with the errors −11.8 and −3.0%, respectively). For the comparison of the two sets of data, HPLC-ECD method is much more promising.     

Determination of Piroxicam in Pharmaceutical Formulations Combining Amperometry and Multicommutation

This work describes the development of a multicommutated flow system with amperometric detection, applied in the determination of piroxicam in pharmaceutical formulations.     

Characterization of O+ Ion-implanted Glassy Carbon Using the Superconducting Electron Cyclotron Resonance Ion Source and Selective Dopamine Detection

The O and N gas ions (O³⁺, O⁺, N²⁺, and N⁴⁺) were implanted on the glassy carbon surface employing the electron cyclotron resonance ion source, which were characterized using electrochemical and surface analysis methods. The modified electrode was examined for the catalytic oxidation of bioorganic molecules including dopamine, where the O⁺ ion implanted GC revealed the best catalytic performance. The XPS and Raman results represented that the ion implantation made enrichment in graphite nanocrystalline structure with edge plane, showing the enhanced electrochemical activity. It showed excellent performance for dopamine detection without significant interferences between 50.0 nM and 400.0 μM with the detection limit of 10.0±2.5 nM (95 % confidence level). The reliability of proposed electrode was evaluated by the real urine sample analysis.     

A highly sensitive hydrogen peroxide amperometric sensor based on MnO2-modified vertically aligned multiwalled carbon nanotubes

In this report, a highly sensitive amperometric sensor based on MnO₂-modified vertically aligned multiwalled carbon nanotubes (MnO₂/VACNTs) for determination of hydrogen peroxide (H₂O₂) was fabricated by electrodeposition. The morphology of the nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer and X-ray diffraction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were applied to investigate the electrochemical properties of the MnO₂/VACNTs nanocomposite electrode. The mechanism for the electrochemical reaction of H₂O₂ at the MnO₂/VACNTs nanocomposite electrode was also discussed. In borate buffer (pH 7.8, 0.20 M), the MnO₂/VACNTs nanocomposite electrode exhibits a linear dependence (R = 0.998) on the concentration of H₂O₂ from 1.2 × 10⁻⁶ M to 1.8 × 10⁻³ M, a high sensitivity of 1.08 × 10⁶ μA M⁻¹ cm⁻² and a detection limit of 8.0 × 10⁻⁷ M (signal/noise = 3). Meanwhile, the MnO₂/VACNTs nanocomposite electrode is also highly resistant towards typical inorganic salts and some biomolecules such as acetic acid, citric acid, uric acid and d-(+)-glucose, etc. In addition, the sensor based on the MnO₂/VACNTs nanocomposite electrode was applied for the determination of trace of H₂O₂ in milk with high accuracy, demonstrating its potential for practical application.     

Chloroperoxidase Modified Electrode for Amperometric Determination of 2,4,6‐Trichlorophenol

A carbon paste‐poly(o‐phenylendiamine)‐modified electrode to be used as amperometric biosensor for 2,4,6‐trichlorophenol (TCP) is described. The enzyme chloroperoxidase (EC 1.11.1.10) from Caldariomyces fumago is immobilized through dispersion in a graphite paraffin oil carbon paste covered by an electrogenerated poly(o‐phenylendiamine) (PPD) layer. The main enzymatic dehalogenation product, 2,6‐dichloro‐1,4‐benzoquinone (DCQ) is characterized by liquid chromatography‐mass spectrometry and cyclic voltammetry. This product is electrochemically active and can be detected amperometrically at +150 mV vs. Ag|AgCl|KCl (3 M). The biosensor exhibits a response time of 4 min, a detection limit of 10^?7 M, and a dynamic linear range between 10^?7 and 10^?6 M. Selectivity as well as operating and storage stability were evaluated.     

Amperometric detection of ultra trace amounts of Hg(I) at the surface boron doped diamond electrode modified with iridium oxide

Iridium oxide (IrOx) films formed electrochemically on the surface boron doped diamond electrode by potential cycling in the range −0.2 to 1.2 V from a saturated solution of alkaline iridium(III) solution. A strongly adherent deposit of iridium oxide is formed after 5–10 potential scans. The properties, stability and electrochemical behavior of iridium oxide layers were investigated by atomic force microscopy and cyclic voltammetry. The boron doped diamond (BDD) electrode modified with electrodeposition of a thin film, exhibited an excellent catalytic activity for oxidation of Hg(I) over a wide pH range. The modified electrode shows excellent analytical performance for Hg(I) amperometric detection. The detection limit, sensitivity, response time and dynamic concentration ranges are 3.2 nM, 77 nA μM⁻¹, 100 ms and 5 nM–5 μM. These analytical parameters compare favorably with those obtained with modern analytical techniques and recently published electrochemical methods.     

Simultaneous determination of flavonoids and anthraquinones in chrysanthemum by capillary electrophoresis with amperometry detection

<正>A high-performance capillary electrophoresis with amperometry detection method(CE-AD) has been developed for the analysis of flavonoids and anthraquinones(emodin,kaempferol,apigenin,luteolin and rhein) in chrysanthemum.Under optimum conditions,these five analytes were base-line separated within 17 min using a borate-phosphate running buffer(1.5×10~(-2) mol/L borate-3×10~(-2) mol/L phosphate running buffer,pH 9.0) at a working potential of +0.90 V(vs.SCE) and a separation voltage of 19 kV.The linear relationship between concentration and current response was obtained with detection limits(S/N = 3) ranging from 1.0×10~(-7) to 2.1×10~(-7) g/mL for all analytes.This proposed method was successfully used in the analysis of four kinds of chrysanthemum with relatively simple extraction procedures,the assay results were satisfactory.