依诺沙星在碳糊电极上的阳极吸附伏安法研究

在0.40 mol/L的NaAc-HAc(pH 4.5)缓冲液中,使用JP-303极谱分析仪,依诺沙星在碳糊电极(CPE)上有一灵敏的吸附伏安氧化峰,峰电位为1.17 V(vs.SCE).该氧化峰的二阶导数峰电流与依诺沙星的浓度在4.0×10-9～4.0×10-7 mol/L(富集90 s)范围内呈良好的线性关系,相关系数为0.995,检出限为2.0×10-9 mol/L(S/N=3,富集110 s).探讨了依诺沙星在碳糊电极上的伏安性质和电极反应机理,并且用于诺佳胶囊中依诺沙星的测定.     

Preconcentration and voltammetric determination of the herbicide metamitron with a silica-modified carbon paste electrode

A carbon paste electrode incorporating silica (Si-MCPE) was fabricated to accumulate Metamitron at the electrode surface. Several electroanalytical techniques were used to explore its reductive behaviour. The results indicate that the system is irreversible and fundamentally controlled by adsorption. The adsorptive stripping response has been evaluated with respect to accumulation time, deposition potential, scan rate, pH and other variables, using differential pulse voltammetry (DPV) and square wave voltammetry (SWV) as redissolution techniques. In both cases a voltammetric peak is obtained, at –0.542 V (DPV) and –0.421 V (SWV) in Britton-Robinson buffer (pH 1.9). The detection limits were 3.66 × 10^–1 M and 4.22 × 10^–9 M for AdS-DPV and AdS-SWV, respectively. Under optimum conditions the Metamitron reduction peak gave two linear regions in the range from 4.0 × 10^–9 M to 8.0 × 10^–8 M by means of AdS-DPV, with a coefficient of variation of 2.19% (n = 10) for 1 × 10^–8 M herbicide solution. A method was developed for determination of Metamitron in soils, with a recovery of 98.8% and a coefficient of variation of 5.26% (0.01 g/g of soil).     

Anodic stripping voltammetric determination of silver ion at a carbon paste electrode modified with carbon nanotubes

A carbon paste electrode (CPE) was modified with multi-wall carbon nanotubes and successfully applied to the determination of silver ion by differential pulse anodic stripping voltammetry. Compared to a conventional CPE, a remarkably improved peak current response and sensitivity is observed. The analytical procedure consisted of an open circuit accumulation step for 2?min in ?0.4?V, this followed by an anodic potential scan between +0.2 and?+?0.6?V to obtain the voltammetric peak. The oxidation peak current is proportional to the concentration of silver ion in the range from 1.0?×?10^?8 to 1.0?×?10^?5?mol?L^?1, with a detection limit of 1.8?×?10^?9?mol?L^?1 after an accumulation time of 120?s. The relative standard deviation for 7 successive determinations of Ag(I) at 0.1???M concentration is 1.99%. The procedure was validated by determining Ag(I) in natural waters.

Copper oxide nanopowder modified carbon paste electrode for the voltammetric assay of vonoprazan

Vonoprazan (VPZ) is a novel promising member of gastric acid-suppressive medicinal administrated in Japan in 2015. Only a few HPLC analysis protocols were reported for VPZ assaying, therefore, the present work describes for the first time a novel copper oxide nanoparticles-based sensor as a promising analytical tool for differential pulse voltammetric determination of vonoprazan with enhanced sensitivity compared with the bare electrode. An irreversible oxidation process with the two-electron transfer was elucidated with scan rate measurements. At the optimized conditions, peak heights showed against VPZ in the concentration range from 0.99 to 20.00 µg mL^?1, and detection limit of 0.24 µg mL^?1. The proposed sensor showed prolonged stability with a 95% recovery of the original peak height within the first 30 days. Good reproducibility and repeatability of the fabrication protocol was reported with RSD 1.3%. Noticeable resolution between the VPZ, ascorbic acid, and uric voltammetric peaks allows accurate assaying of VPZ in biological fluids with average recoveries agreeable with the conventional HPLC techniques.     

玻碳电极阳极微分脉冲伏安法测定雌激素

本文报道了雌激素的阳极微分脉冲伏安法测定.雌激素在甲醇-Britton-Robinson缓冲液中,以玻碳为工作电极,能获得一个良好的阳极氧化伏安峰,峰高与激素的浓度在1.0×10~(-6)～4.0×10~(-5)M之间有良好线性关系,峰电位随溶液pH值增加而降低,经循环伏安法验证,电极反应为不可逆反立.并报道了孕妇尿中雌三醇的测定.     

Anodic stripping voltammetric determination of titanium(IV) using a carbon paste electrode modified with cetyltrimethylammonium bromide

A method is described for the voltammetric determination of titanium(IV) using a carbon paste electrode modified in situ with cetyltrimethylammonium bromide. The cationic micellar surfactant adsorbs onto the electrode particularly at negative potentials, simultaneously preconcentrating titanium(IV) as the oxalate complex with reduction to titanium(III). Anodic stripping voltammetry exploiting reoxidation can be used for the determination of trace levels of titanium(IV). Linearity between current and concentration exists between 5 and 160 mug l(-1) Ti(IV) (preconcentration time 2 min). The limit of detection (calculated as 3sigma) is 0.1 mug l(-1), with a preconcentration time of 10 min.     

碳糊电极阳极吸附伏安法测定吡哌酸

吡哌酸（Pipmidic acid,简称PPA）,是吡喹酮类合成抗菌药物,目前的主要分析方法有分光光度法、交流示波滴定法、高效液相色谱法、阴极吸附溶出伏安法、单扫描示波极谱法、微分脉冲极谱法和循环伏安法。本文提出了在CPE上阳极吸附伏安法测定PPA的方法,并探讨了PPA在CPE上的伏安性质和电极反应机理。该法准确、简便、灵敏度高,应用于模拟尿样中痕量PPA的测定,得到满意的结果。     

Multi-walled carbon nanotube paste electrode for selective voltammetric detection of isoniazid

A multi-walled carbon nanotube paste electrode (MWCPE) is prepared as an electrochemical sensor with high sensitivity and selectivity in responding to isoniazid. The electrochemical oxidation of isoniazid is investigated in buffered solution by cyclic and differential pulse voltammetry. The electrode is shown to be very effective for the detection of isoniazid in the presence of other biological reductant compounds. The electrochemical oxidation of cysteine, due to the high overvoltage, is completely stopped at the surface of MWCPE. The electrode exhibits a very good resolution between the voltammetric peak of isoniazid and the peaks of ascorbic acid (AA) and dopamine (DA). A resolution of more than 450 mV between the anodic peak potentials makes the MWCPE suitable for simultaneous detection of isoniazid in the presence of AA or DA in clinical and pharmaceutical preparations. Differential pulse voltammetry (DPV) is applied as a sensitive method for the determination of isoniazid. The linear range in these determinations is 1 × 10⁻⁶–1 × 10⁻³ M for isoniazid and the detection limit is 5 × 10⁻⁷ M. The electrode was applied to the simultaneous determinations in isoniazid and AA mixtures and also, isoniazid and DA mixture over a wide concentration range. The slope variation for the calibration curves of isoniazid (RSD) was less than 4.5% (based on ten measurements over a period of three months).     

Catalytic adsorptive stripping voltammetric determination of copper(II) on a carbon paste electrode

A catalytic adsorptive stripping voltammetric method for the determination of copper(II) on a carbon paste electrode (PCE) in an alizarin red S (ARS)-K₂S₂O₈ system is proposed. In this method, copper(II) is effectively enriched by both the formation and adsorption of a copper(II)-ARS complex on the PCE, and is determined by catalytic stripping voltammetry. The catalytic enhancement of the cathodic stripping current of the Cu(II) in the complex results from a redox cycle consisting of electrochemical reduction of Cu(II) ion in the complex and subsequent chemical oxidation of the Cu(II) reduction product by persulfate, which reduces the contamination of the working electrode from Cu deposition and also improves analytical sensitivity. In Britton-Robinson buffer (pH 4.56±0.1) containing 3.6×10⁻⁵ mol L⁻¹ ARS and 1.6×10⁻³ mol L⁻¹ K₂S₂O₈, with 180 s of accumulation at −0.2 V, the second-order derivative peak current of the catalytic stripping wave was proportional to the copper(II) concentration in the range of 8.0×10⁻¹⁰ to ∼3.0×10⁻⁸ mol L⁻¹. The detection limit was 1.6×10⁻¹⁰ mol L⁻¹. The proposed method was evaluated by analyzing copper in water and soil.     

Differential pulse voltammetric determination of aniline with a carbon paste electrode modified by sepiolite

Summary The determination of aniline by means of a carbon paste electrode (CPE) modified with 10% sepiolite was studied using differential pulse voltammetry. The best pre-concentration was achieved at pH 6.9 over 5 min and the besti _p in the measuring cell was obtained at pH 1.5 using E = 100 mV and a scan rate of 40 mV/s.Under these conditions detection limits (10 ) of 15 ng/ ml were obtained. The method was applied to different beverages without the need for prior separation.

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Differentialpuls-voltammetrische Bestimmung von Anilin mit einer Sepiolit-modifizierten Kohlepaste-Elektrode

     

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L^–1 HCl solution containing 0.02 mol L^–1 KI, Hg²⁺ was firstly preconcentrated at the MWNT film and then reduced at –0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about –0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I^– remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg²⁺ at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg²⁺ over the range 8×10^–10–5×10^–7 mol L^–1. The lowest detectable concentration of Hg²⁺ is 2×10^–10 mol L^–1 at 5 min accumulation. The relative standard deviation (RSD) at 1×10^–8 mol L^–1 Hg²⁺ was about 6% (n=10). By using this proposed method, Hg²⁺ in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.     

Electroregenerable anion-exchange resin with triiodide carbon paste electrode for the voltammetric determination of adrenaline

An electroregenerable carbon paste electrode modified with triiodide ions immobilized in an anion-exchange resin (Lewatit M500) is proposed for the determination of adrenaline in pharmaceutical products by differential-pulse voltammetry (DPV). Adrenaline was chemically converted into adrenochrome by the I3- ions at the electrode surface. The electrochemical reduction back to adrenaline was obtained at a potential of -0.16 V vs. Ag/AgCl (3 mol l(-1) KCl). A 20% decrease of the initial analytical signal was observed after 350-400 determinations; the carbon paste electrode was 100% electroregenerated at a fixed potential of +0.65 V vs. Ag/AgCl (3 mol l(-1) KCl) in 0.1 mol l(-1) KI solution for 20 min. The differential-pulse voltammograms were obtained by applying a sweep potential between 0.0 and -0.34 V, following the adrenochrome reduction at -0.16 V. Under the optimum conditions established, such as pH 6.0; scan rate 20 mV s(-1) and pulse amplitude 50 mV, the calibration curve was linear from 2.0 x 10(-5) to 3.1 x 10(-4) mol l(-1) adrenaline with a detection limit of 3.9 x 10(-6) mol l(-1). The recovery of adrenaline ranged from 99.8 to 103.1% and the RSD was 2.6% for the solution containing 1.0 x 10(-4) mol l(-1) adrenaline (n = 10). The results obtained for adrenaline in pharmaceutical samples using the proposed carbon paste electrode are in agreement with those obtained using a pharmacopoeial procedure at the 95% confidence level.     

Stripping voltammetric determination of platinum metals at a carbon paste electrode modified with cationic surfactants

In this contribution, a novel method is described for the determination of platinum metals. The procedure developed employs a carbon paste electrode modified in situ with cationic surfactants of the quaternary ammonium salt type. The pre-concentration step is based on a specific accumulation mechanism involving ion-pair formation; the detection being performed by cathodic scanning in the differential pulse voltammetric mode. Regarding the individual forms of platinum metals, the method has been found convenient for the determination of three heavy platinum metals in the form of Pt(IV), Ir(III) and Os(IV), whereas for the remaining elements (Ru, Rh, and Pd) was almost inapplicable. Platinum metals of the former group can be pre-concentrated in chloride-containing supporting media via PtCl₆²⁻, IrCl₆³⁻ and OsCl₆²⁻ complex anions, the central atom of each species being fairly reducible during the voltammetric scan. Stripping signals for both platinum and iridium were proportional to the concentration in a range of 1-10 × 10⁻⁶ M Pt(IV) and Ir(III); the response for osmium being linear within 0.1-6 × 10⁻⁷ M Os(IV) with a detection limit of about 5 × 10⁻⁹ mol l⁻¹. During optimisation, special attention was paid to the accumulation mechanism, choice of key experimental conditions, and to interference effects from foreign ions with potentially ion-pairing capabilities (AuCl₄⁻, TlCl₄⁻, CrO₄²⁻, MnO₄⁻, SCN⁻, and I⁻). The method elaborated has been tested on both model solutions and real samples of industrial waste water, showing in both cases satisfactory analytical performance.     

Sensitive voltammetric determination of rutin at an ionic liquid modified carbon paste electrode

An ionic liquid modified carbon paste electrode (IL/CPE) had been fabricated by using hydrophilic ionic liquid 1-amyl-3-methylimidazolium bromide ([AMIM]Br) as a modifier. The IL/CPE was characterized by scanning electron microscope and voltammetry. Electrochemical behavior of rutin at the IL/CPE had been investigated in pH 3.29 Britton-Robinson (B-R) buffer solution by cyclic voltammetry (CV) and square wave voltammetry (SWV). The experimental results suggested that the modified electrode exhibited an electrocatalytic activity toward the redox of rutin. The electron transfer coefficient (α) and the standard rate constant (k_s) of rutin at the modified electrode were calculated. Under the selected conditions, the reduction peak current was linearly dependent on the concentration of rutin in the range of 4.0 × 10⁻⁸ to 1.0 × 10⁻⁵ mol L⁻¹ (r = 0.9998), with a detection limit of 1.0 × 10⁻⁸ mol L⁻¹ (S/N = 3). The relative standard deviation (R.S.D.) for six times successful determination of 8.0 × 10⁻⁷ mol L⁻¹ rutin was 1.2%. The proposed method was applied to determine rutin in tablet and urine sample. In addition, the IL/CPE exhibited a distinct advantage of simple preparation, surface renewal, good reproducibility and good stability.     

Stripping voltammetric determination of mercury(II) at antimony-coated carbon paste electrode

A new procedure was elaborated to determine mercury(II) using an anodic stripping square-wave voltammetry at the antimony film carbon paste electrode (SbF-CPE). In highly acidic medium of 1 M hydrochloric acid, voltammetric measurements can be realized in a wide potential window. Presence of cadmium(II) allows to separate peaks of Hg(II) and Sb(III) and apparently catalyses reoxidation of electrolytically accumulated mercury, thus allowing its determination at ppb levels. Calibration dependence was linear up to 100 ppb Hg with a detection limit of 1.3 ppb. Applicability of the method was tested on the real river water sample.     

Studies on the voltammetric behaviour of a 2-mercaptoimidazole containing carbon paste electrode: determination of traces of silver

The voltammetric behaviour of a 2-mercaptoimidazole (2-MI) containing carbon paste electrode was studied. When mixed to carbon paste as an electrode modifier, 2-MI can be reduced at negative potentials (–1 V vs. SCE), but it does not give a response in the potential range where Ag(0) is oxidized to Ag(I). Silver could be accumulated from 0.1 mol l^–1 acetate buffer onto a 2-MI modified carbon paste electrode without a potential applied; after medium exchange, it was reduced at –1 V vs. SCE in 0.1 mol l^–1 acetate buffer solution and determined by differential pulse anodic stripping voltammetry. With suitable preconcentration times, the detection limit was 0.1 g l^–1; a linear relation between current and concentration was found to exist within a range of 0.5 to 1000 g l^–1. In the presence of EDTA, common metal ions have no or only little effect on the voltammetric determination of silver.     

Anodic stripping voltammetry of silver(I) using a carbon paste electrode modified with multi-walled carbon nanotubes

We describe a silver(I)-selective carbon paste electrode modified with multi-walled carbon nanotubes and a silver-chelating Schiff base, and its electrochemical response to Ag(I). Effects of reduction potential and time, accumulation time, pH of the solution and the stripping medium were studied by differential pulse anodic stripping voltammetry and optimized. The findings resulted in a method for the determination of silver over a linear response range (from 0.5 to 235 ng?mL^?1) and with a detection limit as low as 0.08 ng?mL^?1. The sensor displays good repeatability (with the RSD of ±?2.75 % for 7 replicates) and was applied to the determination of Ag(I) in water samples and X-ray photographic films.

Application of mesoporous SiO2-Modified carbon paste electrode for voltammetric determination of epinephrine

Mesoporous SiO₂ of SBA-15 is reported to modify carbon paste electrodes for detecting epinephrine (EP). Carbon paste electrodes modified with synthesized SBA-15 show high sensitivity for voltammetric determination of EP, which is attributed to the strong adsorption ability of SBA-15 to EP and large surface area of the working electrode resulted from SBA-15 modification. The effects of pH value, amount of SBA-15 and scan rate were investigated. Under optimum conditions, the anodic peak current of EP was proportional to its concentration over the range from 1.0 × 10^?6 to 6.0 × 10^?5 mol L^?1 and the limit of detection was 6.0 × 10^?7 mol L^?1. The results show mesoporous SiO₂-modified carbon paste electrodes, particularly SBA-15-modificd electrodes, create new opportunities for sensitive, simple and suitable method in the electrochemical analysis of EP.