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721.
A composition of multiwalled carbon nanotube (MWCNT), Nafion and cobalt(II)‐5‐nitrosalophen (CoNSal) is applied for the modification of carbon‐paste electrode (CPE). The pretreated MWCNT is well dispersed in the alcoholic solution of Nafion under the ultrasonic agitation, and the resulted suspension is used as modifier (with 10% w/w) in the matrix of the paste electrode. The prepared electrode further modified by addition of 3 wt% of CoNSal. The resulted modified electrode is used as a sensitive voltammetric sensor for simultaneous determination of uric acid (UA) and ascorbic acid (AA). The electrode showed efficient electrocatalytic activity in lowering the anodic overpotentials and enhancement of the anodic currents. This electrode is able to completely resolve the voltammetric response of UA and AA. The effects of potential sweep rate and pH of the buffer solution on the response of the electrode, toward UA and AA, and the peak resolution is thoroughly investigated by cyclic and differential pulse voltammetry (CV and DPV). The best peak resolution for these compounds using the modified electrode is obtained in solutions with pH 4. The ΔEp for UA and AA in these methods is about 315 mV, which is considerably better than previous reports for these compounds. A linear dynamic range of 1×10?7 to 1×10?4 M with a detection limit of 6×10?8 M is resulted for UA in buffered solutions with pH 4.0. The voltammetric response characteristics for AA are obtained as, the linear range of 5×10?7 to 1×10?4 M with the detection limit of 1×10?7 M. The voltammetric detection system was very stable and the reproducibility of the electrode response, based on the six measurements during one month, was less than 3.5% for the slope of the calibration curves of UA and AA. The prepared modified electrode is successfully applied for the determination of AA and UA in mixture samples and reasonable accuracies are resulted. 相似文献
722.
Cu2+-mediated salbutamol-imprinted polymer nanoparticles, synthesized by precipitation polymerization, were mixed with graphite powder and n-eicosane in order to fabricate a modified carbon paste electrode. This electrode was then applied for indirect differential pulse voltammetry determination of salbutamol. In the presence of Cu2+ ions, the formed Cu2+–salbutamol complex was adsorbed in to the pre-designed cavities of the MIP particles, situated on the electrode surface. Since the electrochemical signal of salbutamol was intrinsically small, the oxidation peak of the participant Cu2+, after reduction step, was recorded and used as an indication of salbutamol amount, adsorbed in the electrode. Different variables influencing the sensor performance were studied and the best conditions were chosen for the determination purpose. Correlation between the sensor response to salbutamol and its concentration was linear in the range of 1.0 × 10−9–5.5 × 10−8 M. Detection limit was calculated equal to 6.0 × 10−10 M (S/N). Five replicated determination of salbutamol (1 × 10−8 M) resulted in standard error of 3.28%, meaning a satisfactory precision of the determination method. The prepared sensor was applied for real sample analysis. In order to minimize the interference effect, the synthesized polymer was successfully used as a solid phase sorbent for salbutamol extraction, before analysis of real samples by the developed sensor. 相似文献
723.
Sayed Mehdi Ghoreishi Mohsen Behpour Mahshid Golestaneh 《International journal of environmental analytical chemistry》2013,93(12):1403-1416
In this paper, a simple, convenient and sensitive electrochemical method has been developed for the determination of C.I. Direct Red 80. A gold nanoparticle modified carbon paste electrode was fabricated and used for study and sensitive determination of Direct Red 80 by cyclic voltammetry and differential pulse voltammetry. The overall analysis involved a two-step procedure: an accumulation step under open-circuit conditions, followed by voltammetric measurements of Direct Red 80 in a 0.1?M phosphate buffer solution at pH?=?3.0. The experimental conditions, such as the medium, pH and accumulation time, were optimised. The oxidation peak current was proportional to the concentration of Direct Red 80 from 5.0?×?10?8 to 5.0?×?10?7?M and 5.0?×?10?7 to 3.0?×?10?6?M, and the detection limit was 1.15?×?10?8?M (S/N?=?3). The proposed method was used to detect Direct Red 80 in natural water and sewage with good accuracy. 相似文献
724.
马明明 《理化检验(化学分册)》2006,42(8):651-653
研究活性染料常用的嫩黄基础谱带——活性嫩黄K-4G,在具有较小表面积(约为0.07cm^2)的碳糊电极上的电化学响应行为。在-1.0~1.3V的扫描电位窗内,活性嫩黄K-4G显示良好的电氧化还原性质,电极反应速率为吸附控制,电极反应机理为先质子化后电氧化还原。 相似文献
725.
Karl-Heinz Lubert Markus Guttmann Lothar Beyer 《Journal of Solid State Electrochemistry》2002,6(8):545-552
The study of the electrode reactions of palladium(II) at non-modified carbon paste electrodes (CPEs) in chloride solution
has revealed the existence of a chloropalladate(II) complex at the electrode surface. The complex is formed during the application
of anodic potentials after preceding palladium deposition. In the present paper the electrode reactions of PdII at CPEs modified with some N′,N′-disubstituted derivatives of N-benzoylthiourea [as selective ligands for palladium(II)] are studied in chloride solution by cyclic voltammetry. Two reduction
peaks are observed in the cathodic scans recorded after deposition of palladium and anodization of the electrode. From the
results it is concluded that [in addition to the chloropalladate(II) complex, observed at the non-modified electrode] a second
palladium complex is formed at positive potentials. The formation of the palladium(II) complex of the N-benzoylthiourea derivatives by ligand exchange at the electrode surface is assumed. The ligand exchange itself occurs without
charge transfer across the electrode|solution interface; therefore, it cannot be detected electrochemically. After palladium
deposition and anodic treatment a pronounced "inverse" peak (i.e., an anodic peak in the cathodic scan) with peak currents
up to 100 μA is observed at about +0.8 V. Its peak current increases with the amount of deposited palladium and the number
of cycles. The reactions at the electrode surface are discussed. The results of the study reveal the existence of two different
surface complexes of palladium(II) at ligand-modified CPEs, but the surface reactions could not be elucidated in detail.
Electronic Publication 相似文献
726.
A chemically modified electrode (CME) was prepared and studied as a potentiometric sensor for the end-point detection in the automatic titration of vanadium(V) with EDTA. The CME was constructed with a paste prepared by mixing spectral-grade graphite powder, Nujol oil and N-2-naphthoyl-N-p-tolylhydroxamic acid (NTHA). Buffer systems, pH effects and the concentration range were studied. Interference ions were separated by applying a liquid-liquid extraction procedure.The CME did not require any special conditioning before using. The electrode was constructed with very inexpensive materials and was easily made. It could be continuously used, at least two months without removing the paste.Automatic potentiometric titration curves were obtained for V(V) within 5 × 10−5 to 2 × 10−3 M with acceptable accuracy and precision. The developed method was applied to V(V) determination in alloys for hip prothesis. 相似文献
727.
Hasan Bagheri Abbas Afkhami Ali Shirzadmehr Hosein Khoshsafar Hamid Khoshsafar Hamed Ghaedi 《International journal of environmental analytical chemistry》2013,93(5):578-591
A novel ion selective carbon paste electrode for Cd2+ ions based on 2,2′-thio-bis[4-methyl(2-amino phenoxy) phenyl ether] (TBMAPPE) as an ionophore was prepared. The carbon paste was made based on a new nano-composite including multi-walled carbon nanotubes (MWCNTs), nanosilica and room-temperature ionic liquid, 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6). The constructed nano-composite electrode showed better sensitivity, selectivity, response time, response stability and lifetime in comparison with typical Cd2+ carbon paste sensor for the successful determination of Cd2+ ions in water and in waste water samples. The best performance for nano-composite sensor was obtained with an electrode composition of 18% TBMAPPE, 20% BMIM-PF6, 48% graphite powder, 10% MWCNT and 4% nanosilica. The new electrode exhibited a Nernstian response (29.95?±?0.10?mV?decade?1) toward Cd2+ ions in the range of 3.0?×?10?8 to 1.0?×?10?1?mol?L?1 with a detection limit of 7.5?×?10?9?mol?L?1. The potentiometric response of prepared sensor was independent of the pH of test solution in the pH range 3.0 to 5.5. It had a quick response with a response time of about 6?s. The proposed electrode showed fairly good selectivity over some alkali, alkaline earth, transition and heavy metal ions. 相似文献
728.
结合学生的生活实际,金属复习课从学生熟悉的暖宝宝入手,采用项目式教学法。项目式教学法使学生作为项目的执行者,调动学生学习的积极性和主动性,培养学生的动手能力、思维能力、知识综合运用的能力,最终促成学生对金属知识深入而全面的掌握。 相似文献
729.
A graphite powder – ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate, BMIMPF6) paste coated gold electrode (graphite – BMIMPF6/Au) is presented. The area and the thickness of the paste film are controlled through a sticking film with a hole. The electrode
shows good stability and high electric conductivity, and K4Fe(CN)6 exhibits reversible voltammetric peaks at it. A voltammetric study of promethazine revealed that promethazine exhibits a
sensitive anodic peak in pH 6.7 buffer solutions. Under the optimized conditions, the peak current is linearly related to
the promethazine concentration in the range of 5.0 × 10−8–5.0 × 10−5 M. A 5 μM promethazine solution is measured successively for ten times with the same electrode, the relative standard deviation
(RSD) of peak current is 1.7%. The promethazine content in a Chinese medicine (i.e. Complex Reserpine) is determined. The
result is in accordance with the declared value, and the recoveries are 96.1–104%. 相似文献
730.
The synthesis of NiO/NiCo2O4 nanoparticles by an eco-friendly, fast, simple and cost-effective approach employing Urtica extract is reported in this study. The NiO/NiCo2O4 nanocomposite were characterized using VSM, FTIR, XRD, and SEM techniques. Moreover, to construct a modified carbon paste electrode, NiO/NiCo2O4 were employed and this sensor was used for dopamine (DA) detection. Using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques, the electrochemical behavior of dopamine at the NiO/NiCo2O4/CPE was investigated. Analysis of dopamine, with a limit of detection (LOD) equal to 0.04 μM, in the concentration range of 0.1–100.0 μM, was facilitated by NiO/NiCo2O4/CPE. Moreover, the satisfactory selectivity for DA determination in the presence of uric acid (UA) and ascorbic acid (AA), was obtained. The suggested new sensor displayed a good reproducibility, sensitivity, and stability for determination of DA in drug and biological samples. 相似文献