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61.
《Electroanalysis》2003,15(14):1204-1211
Two types of glassy carbon (GC) powder (i.e., Sigradur K and Sigradur G) have been mixed with mineral oil to obtain glassy carbon paste electrodes (GCPE's). The electrochemical behavior of such electrodes at different percentages of glassy carbon has been evaluated with respect to the electrochemistry of ferricyanide as revealed with cyclic voltammetry and the best paste composition was chosen. GC was then modified with Prussian Blue (PB), mixed at different percentages with unmodified GC and with a fixed amount of mineral oil in order to obtain PB modified glassy carbon paste electrodes (PB‐GCPE's). PB‐GCPE's with different percentages of GC modified with PB (PB‐GC) were compared and the dependence on the amount of PB on their performances was evaluated by studying the parameters of cyclic voltammetry (i.e., current peak, ΔEp, anodic and cathodic current ratio, charge density) and the amperometric response to H2O2. Data interpretation based on the GC surface area is presented. GCPE's with a selected amount of PB‐GC were then tested as H2O2 probes and all the analytical parameters together with the dependence on pH were evaluated. Some preliminary experiments with these electrodes assembled as glucose, lysine and lactate biosensors are also reported. 相似文献
62.
Lawrence W Dick Jr. 《Analytica chimica acta》2004,511(2):197-205
The synthesis and the spectroscopic and potentiometric characterization of electropolymerized films obtained from neutral red (NR) on Pt surface are described. FT Raman and NMR spectroscopy were used for evaluation of the resulting poly(NR) layers. Then potentiometry was applied to study the characteristics of the complexation of carboxylates with the poly(NR) films. A potentiometric poly(NR) sensor showing high selectivity for citrate anion was employed for its determination in soft drinks. 相似文献
63.
采用了研磨后超声和离心分离方法制备了二硫化钼纳米片,通过原子力显微镜(AFM)和扫描电子显微镜(SEM)对不同离心速度分离的二硫化钼纳米片进行了表征。使用循环伏安法(CV)和差分脉冲伏安法(DPV)在磺胺甲恶唑溶液中对二硫化钼纳米片修饰的玻碳电极进行了电化学行为研究。结果显示,磺胺甲恶唑在二硫化钼修饰电极的循环伏安图上有一对氧化还原峰。其峰电流值与扫描速度的平方根成正比,是扩散控制过程。DPV扫描结果显示,磺胺甲恶唑的峰电流与其浓度之间存在着明显的线性关系。研磨超声方法制备出的二硫化钼纳米片层材料在电极上能够加速电子的转移和传输,从而有效提高峰电流值,为进一步研制准确测定磺胺甲恶唑电化学传感器提供了一种可选择的材料和电化学分析方法。 相似文献
64.
An anionic sensor based on Reichardt’s betaine is described here. The dye is blue-green in chloroform but becomes colorless under protonation. Increasing amounts of different anions were added into the solution of the protonated dye. The addition of F− and caused the reappearance of the original blue-green color, while the addition of I− made the solution of the protonated dye yellow. The observations are discussed based on the fact that F− and can act as bases accepting a proton from the protonated dye and also in relation to the formation of a complex between the protonated dye and iodide. 相似文献
65.
A solid state copper(II) ion sensor is reported based on the application of electropolymerized undoped (neutral) polycarbazole
(PCz) and polyindole (PIn) modified electrodes. The new sensor shows high selectivity to Cu2+ ions with a detection limit of 10–5 M. PCz and PIn are formed respectively by the anodic oxidation of 50 mM carbazole and 5 mM indole monomers in dichloromethane
containing 0.1 M tetrabutylammonium perchlorate on a platinum electrode using a single compartment cell. Potentiostatic polymerization
of both the monomers are carried out at 1.3 V and 1.0 V vs. Ag/AgCl, respectively. Perchlorate ions were electrochemically
removed from the polymer films by applying – 0.2 V vs. Ag/AgCl. Polymer-coated electrodes are incubated in 1 M KCl solution
for 8 h followed by incubation in distilled water for 2 h before using as a metal ion sensor. The undoped PCz and PIn electrodes
were found to be highly selective and sensitive for Cu2+ ions with little selectivity for Pb2+ and negligible response towards Ag+, Hg2+, Cu+, Ni2+, Co2+, Fe2+, Fe3+ or Zn2+. Potentiometric responses for Cu2+ ions are recorded for both the sensor electrodes together with a double-junction Ag/AgCl reference electrode. Calibration
curves for Cu2+ are reported for both ion sensors. The polymer-modified electrodes were found to be stable for several weeks.
Electronic Publication 相似文献
66.
67.
Nitrile butadiene rubber, NBR, structural foam of different apparent densities was obtained by using different concentrations of foaming agent, azodicarbonamide, ADC/K. The true stress-strain characteristics, in case of compression, of foamed samples after the application of cyclic stress-strain were measured. The effect of the cyclic stress-strain on strain energy density of ADC/K foaming agent-filled NBR rubber composites was studied. The mechanical parameters were found to depend on the foaming agent concentration and on the pre-cyclic fatigue number. Results also indicated that the strain energy decreased with filler concentration.The effects of the cyclic stress-strain on the conductivity of ADC/K foaming agent-filled NBR rubber composites were studied. The electrical properties were found to depend on the foaming agent concentration, the strain amplitude and the number of stress-strain cycles of pre-strain. This study was assisted by the current-voltage characteristics which were measured under the effect of different compression ratios: 0%, 5%, 10%, 15%, 20%, 25% and 30%. The free current carrier mobility and the equilibrium concentration of charge carriers in the conduction band were produced as functions of compressive strain. Results also indicate that there is a linear variation between pressure and conductivity for all samples, which means that these samples can be used as a pressure sensor. 相似文献
68.
This paper describes a copper selective optical chemical sensor based on static quenching of the fluorescence of 2-(2′-hydroxyphenyl)benzoxazole entrapped in a poly(vinyl chloride) (PVC) membrane. The effect of the composition of the sensing membrane was studied, and experimental conditions were optimized. The sensors exhibit stable response over the concentration range from 4.0 × 10−8 M to 5.0 × 10−5 M Cu2+ at pH 4.0-6.5, and a high selectivity. The response time for Cu2+ with concentration ≤5 × 10−6 M is less than 7 min. The optode can be regenerated using 0.1 M HCl and acetate buffer solution. The sensor has been used for direct measurement of copper content in river water samples with a relative error less than 4% with reference to that obtained by atomic absorption spectrometry. 相似文献
69.
V. A. Drebushchak 《Journal of Thermal Analysis and Calorimetry》2005,79(1):213-218
One-point (Mettler) and many-point (Netzsch) heat flow calibration of a DSC is discussed. It is shown that the two types of calibration are the alternative extremes between quick but rough procedure and time-consuming but accurate one. One-point calibration compares a typical function k(T) at the melting point of indium with the measured value for particular DSC and multiplies k(T) by a scaling factor. Many-point calibration is based on general mathematical procedure, namely fitting a set of experimental values of sensitivity to a polynomial. The polynomial coefficients are evaluated by the method of least squares. Based on the relationship between the sensitivity of a thermocouple and calibration coefficient of a DSC sensor made from it, two-point heat flow calibration is suggested. This is an optimal calibration procedure, for the relationship contains only two unknown coefficients. An example of how to perform the two-point calibration with Netzsch-Proteus Software is described in the Appendix. 相似文献
70.
Recently, a novel enzymatic method was developed for determination of homocysteine. This method utilizes the electrochemical hydrogen sulfide sensor along with methionine α,γ‐lyase to accomplish the fast, accurate, sensitive and selective measurements. As a continuation of this work, another enzyme, homocysteine α,γ‐lyase, was used and the parallel experiments of using both enzymes were carried out against the effect of pH, sensitivity, linearity, and interferences, in an intended comparison between these two enzymes. The excellent linearity of amperometric currents against homocysteine concentrations, high sensitivities and low detection limits for both enzymes reconfirmed that the electrochemical method is superior over other analytical means. The high enzymatic activity of methionine α,γ‐lyase surpassing homocysteine α,γ‐lyase endowed the former higher sensitivity, lower detection limit and faster response than the latter, suggesting methionine α,γ‐lyase a better candidate for homocysteine measurement by electrochemical method. The differences between these two enzymes on the trends of response time and sensitivity at different pH environments, reactivity toward several forms of homocysteine as well as on the interference from several agents were also addressed and discussed. 相似文献