Synergistic Effect of MWNTs/CeO2/CHIT Film for Detection of CdSe Nanoparticle Labeled Sequence‐Specific of 35S Promoter of Cauliflower Mosaic Virus Gene

A porous composite film was fabricated combining the advantages of multiwalled carbon nanotubes, CeO₂ and chitosan. The synergistic effect of the film improved the immobilization of probe ssDNA. The loaded probe ssDNA was used for detection of CdSe quantum dots labeled target DNA. The DNA hybridization reaction was detected by differential pulse anodic stripping voltammetry of Cd²⁺ after the oxidative release of labeled CdSe quantum dots. The established DNA biosensor can discriminate different target sequences associated with 35S promoter of cauliflower mosaic virus gene with relatively wide linear range and low detection limit (2.4×10^?13 mol/L).     

Antimony Film Electrode Prepared In Situ in Hydrogen Potassium Tartrate in Anodic Stripping Voltammetric Trace Detection of Cd(II), Pb(II), Zn(II), Tl(I), In(III) and Cu(II)

An antimony film electrode (SbFE) was prepared in situ on a glassy carbon support and in a new supporting electrolyte, a saturated solution of hydrogen potassium tartrate in which Sb(III) ions were complexed using tartrate. Its performance in anodic stripping voltammetric (ASV) determination of Cd(II), Pb(II), Zn(II), Tl(I), In(III) and Cu(II) traces was examined. It was found that 1.2 mg/L of Sb(III) yields the finest quality SbFE for analytical purposes. The procedure with in situ SbFE ensures well‐defined anodic stripping voltammetric curves of the investigated elements, low detection limits (0.5–3.8 µg/L), good reproducibility (1–5 %) and satisfactory sensitivity (32–184 nA/(µg/L)).     

Determining Trace Concentrations of Copper in Water by Cathodic Film Stripping Voltammetry with Adsorptive Collection

Abstract

A technique is presented for the determination of trace concentrations of copper (II) in natural water samples by cathodic stripping voltammetry of a film of copper-catechol complex ions adsorbed on the hanging mercury drop electrode. The peak height of the copper-catechol reduction peak is linearly dependent upon the copper (II) concentration between 10^?10 and 10^?7 M. The detection limit of the technique is below 10^?10 M copper (II) for a collection time of 3 minutes, but the sensitivity can be further increased four-fold by collecting for 15 minutes. The sensitivity is reduced by high concentrations of competing trace metals and of surfactants, which necessitate the use of standard additions to the sample.     

Voltammetric Measurement of [Cu(II)]/[Cu(I)] at a Platinum Rotating Disc Electrode and Control by Electrolysis at a Platinum Net Electrode in Chloride Solutions

ABSTRACT

A method has been described to measure and control the [Cu(II)]/[Cu(I)] bulk concentration ratio in aqueous chloride solutions. A variation of the ratio is achieved by controlled potential electrolysis at appropriate reducing or oxidizing potentials. The concentration ratio can be monitored by a repetitive double potential step amperometric method at a platinum rotating disc electrode. The amperometric signal can be used to control the electrolytic process in order to obtain and maintain a predetermined bulk concentration ratio. Diffusion coefficients of respectively 6.2 10^?6 and 5.6 10^?6 cm² s^?1 have been determined for Cu(II) and Cu(I). Potential applications of the method are the control of polymerisation reactions, of the reduction of textile dyes with the aid of a mediator system and of the colour characteristics of different kinds of glass.     

Electrochemical Reduction Behavior and Polarographic Determination of Methoxy Triazine Herbicides in Environmental Samples

The electrochemical reduction behavior of 1,3,5-triazine herbicides, Atraton (AN), Prometon (PN), Secbumeton (SN), and Terbumeton (TN) at mercury electrodes was studied in aqueous Britton Robinson buffer (BR) solutions by using different voltammetric techniques. The nature of the electrode process was examined. Number of electrons involved in the reduction process of all the four compounds was evaluated and a reduction mechanism was proposed. The electrolysis products were separated and identified by IR spectra. For analytical purposes, BR buffer of pH 4.0 was chosen as working medium for all the four analytes. The detection limits were found to be 1.5 × 10^?8 mol l^?1, 2 × 10^?8 mol l^?1, 2.8 × 10^?8 mol l^?1, and 1 × 10^?8 mol l^?1 for AN, PN, SN, and TN, respectively. A differential pulse voltammetric method was developed for the determination of these compounds in agricultural formulations, water, and soil samples. The interference from the ions and other herbicides were also evaluated.     

Adsorptive Stripping Voltammetry of 9‐Phenanthrol in the Presence of Copper at the Static Mercury Drop Electrode—Basis for Quantitative Determination of PAH Metabolite in Biological Materials

Abstract

The electrochemical behavior of 9‐phenanthrol in the presence of copper (II) at a static mercury drop electrode was investigated to provide the basis for development of an inexpensive, sensitive, and reliable method for determination of polycyclic aromatic hydrocarbon (PAH) metabolites in biological matrices. Optimum experimental conditions for analytical applications were obtained in 0.005 M NaOH solution using an accumulation potential of ?0.25 V, a scan rate of 5 mV. s^?1, a pulse height of 25 mV, and a differential pulse scan mode. The response of 9‐phenanthrol is linear over the concentration range 1.0–12.0 ppb. For an accumulation time of 5 minutes, the detection limit was found to be 0.2 ppb (1.03×10^?9 M). The more convenient relation to measure the 9‐phenanthrol in the presence of copper and other metals was also investigated. The utility of the method was demonstrated by the presence of 9‐phenanthrol in samples of sea water and human urine. Cyclic voltammetry was used to characterize the interfacial and redox behavior.     

Subsecond FFT‐adsorptive Voltammetric Technique as a Novel Method for Subnano Level Monitoring of Piroxicam in its Tablets and Bulk Form at Au Microelectrode in Flowing Solutions

Abstract

In this work a novel method for the determination of piroxicam in flow‐injection systems has been developed. A system using fast Fourier transform continuous cyclic voltammetry (FFTCV), at a gold microelectrode in flowing solution, was used for determining piroxicam in its pharmaceutical formulations. The developed technique is very simple, precise, accurate, time saving, and economical, compared to all of the previously reported methods. The effects of various parameters on the sensitivity of the method were investigated. The best performance was obtained with a pH value of 2, scan rate value of 40 V/s, accumulation potential of (400) mV, and accumulation time of 0.4 s. The proposed method has some advantages over other reported methods, such as, no need for the removal of oxygen from the test solution, a picomolar detection limit, and finally that the method is fast enough for the determination of any such compound, in a wide variety of chromatographic methods. To obtain a sensitive determination, the integration range of currents was set for all the potential scan ranges, including oxidation and reduction of the Au surface electrode, while performing the measurements. The potential waveform, consisting of the potential steps for cleaning, accumulation, and potential ramp of analyte, was applied on an Au disk microelectrode (with a 12.5 µm in radius) in a continuous way. The method was linear over the concentration range of 1.5–364000 pg/ml (r=0.998) with a limit of detection and quantitation of 0.33 and 1.5 pg/ml, respectively. The method has the requisite accuracy, sensitivity, precision, and selectivity to assay piroxicam in tablets.     

Electrochemical Behaviors of Adenosine‐5′‐triphosphate on Molecular Wire Modified Carbon Paste Electrode and Its Sensitive Detection

A new electrochemical method was proposed for the determination of adenosine‐5′‐triphosphate (ATP) based on the electrooxidation at a molecular wire (MW) modified carbon paste electrode (CPE), which was fabricated with diphenylacetylene (DPA) as the binder. A single well‐defined irreversible oxidation peak of ATP appeared on MW‐CPE with adsorption‐controlled process and enhanced electrochemical response in a pH 3.0 Britton‐Robinson buffer solution, which was due to the presence of high conductive DPA in the electrode. The electrochemical parameters of ATP were calculated with the electron transfer coefficient (α) as 0.54, the electron transfer number (n) as 1.9, the apparent heterogeneous electron transfer rate constant (k_s) as 2.67 × 10^?5 s^?1 and the surface coverage (Γ_T) as 4.15 × 10^?10 mol cm^?2. Under the selected conditions the oxidation peak current was proportional to ATP concentration in the range from 1.0 × 10^?7 mol L^?1 to 2.0 × 10^?3 mol L^?1 with the detection limit as 1.28 × 10^?8 mol L^?1 (3σ) by sensitive differential pulse voltammetry. The proposed method showed good selectivity without the interferences of coexisting substances and was successful applied to the ATP injection samples detection.     

CoSALEN/APO-5复合材料的制备及其电催化还原氧的性能

将金属钴离子引入磷酸铝分子筛APO-5制得CoAPO-5分子筛,再把N,N-双水杨醛缩乙二胺(SALEN)希夫碱通过扩散进入CoAPO-5分子筛孔道并与其中的钴离子配位,形成了CoSALEN配合物,构成CoSALEN/APO-5复合材料.应用物理吸附法,以聚苯乙烯(PS)作粘结剂,将CoSALEN/APO-5涂敷在玻碳电极表面制成修饰电极PS/CoSALEN/APO-5/GCE.循环伏安法(CV)、计时电流法(CA)研究了该修饰电极在不同pH电解质溶液中的电化学行为以及对分子氧的催化还原作用.结果表明,制备的修饰电极能有效地催化分子氧的四电子还原,即氧气被电催化还原为水,据此提出可能的氧还原机理.     

Determination of Trace Thiocyanate by a Chitosan-Modified Glassy Carbon Electrode

IntroductionMany methods for the determination ofthiocyanate,such as spectrophotometry[1— 6] ,ion-selective electrodes[7— 10 ] ,chromatography[11,12 ] ,flow- injection analysis[13 ] ,voltammetry[14 ] ,fluorimetry[15] ,amperometry[16] ,potentiometricprecipitation titration[17] have been reported. Sincethe methods have been used for the determinationof thiocyanate in waste water,biological samples,food and chemical reagents,the determination ofthiocyanate is of great significance. But theexist…