基于铜离子与DNA相互作用的铜离子检测

利用铜离子(Cu~(2+))可与DNA分子中的碱基相互作用形成络合物的性质,将Cu~(2+)富集在DNA修饰电极表面,进而采用微分脉冲伏安法(DPV)实现了铜离子的检测.此外,由于乙二胺四乙酸(EDTA)对Cu~(2+)具有更强的络合能力,富集于DNA修饰电极表面的Cu~(2+)很容易被洗脱液中的EDTA络合,从而实现修饰电极的再生和重复利用.实验结果表明,在最佳实验条件下,Cu~(2+)浓度在2.0×10-6~1.0×10-5mol/L和2.0×10-5~1.0×10-4mol/L范围内与其相对还原峰电流强度(I-I0)呈良好的线性关系,且该传感器简单、稳定,可循环使用.     

Polarographic and voltammetric determination of trace amounts of 2-nitronaphthalene

The polarographic behaviour of 2-nitronaphthalene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, and differential pulse voltammetry and adsorptive stripping voltammetry, both at a hanging mercury drop electrode. Optimum conditions have been found for the determination of 2-nitronaphthalene by the given methods in the concentration ranges of 2×10^–6–1×10^–4, 2×10^–7–1×10^–4, 1×10^–8–1×10^–4 and 2×10^–9–1×10^–8 M, respectively. Practical applicability of these techniques was demonstrated by the determination of 2-nitronaphthalene in drinking and river water after its preliminary separation and preconcentration using liquid–liquid and solid-phase extraction with limits of determination of 3×10^–10 M (drinking water) and 3×10^–9 M (river water).     

Biamperometric and Differential Pulse Polarographic Methods for the Assay of Nomifensine Maleate

Abstract

Biamperometric titration and differential pulse polarography (DPP) are described for the analysis of nomifensine maleate powder and commercial capsules (Merital^R -50 mg). The biamperometric method involved the titration in cold dil. HCl medium against 0.01 M - NaN0₂ and electrometric detection of end point. The mean percent recoveries obtained were 100.0 ± 0.87 and 99.2 ± 0.95 for the authentic powder and capsules, respectively. The DPP method was performed by measuring the peak current, i_P, obtained from the recorded differential polarogram under constant 50mV modulation amplitude. The peak current was measured at the peak potential of ? 1.02 V on the dropping mercury electrode (DME) versus Ag/AgCl/KCl (sat.) reference electrode at pH 5.0 (acetate buffer). A linear relationship between peak current and concentration was demonstrated in the range 3 to 30μg ml^?1. The mean percent recovery for the capsules was 103.1 ± 1.26.     

Voltammertric Behaviour of Clonixin and its Differential Pulse Polarographic Determination in Tablets

ABSTRACT

Clonixin, a non-steroid analgesic, can be both reduced at the mercury electrode and oxidised at the glassy carbon electrode. The anodic response shows well-defined waves in a pH range between pH 2-12. The polarographic response shows two irreversible waves or peaks in the range between pH 1-6 shifting cathodically when pH increases. Above pH 7.0 all the signals disappeared. The first signal in the dpp mode at pH 1.8 was selected for analytical use. The polarographic     

The Determination of Nitrite and Nitrate Ions by Differential Pulse Polarography

Abstract

A previously reported method for the determination of nitrite ion has been extended to include nitrate ion. Nitrate is reduced to nitrite by a cadmium column and the nitrite ion determined as diphenylnitrosamine. Cadmium interference is removed by pH adjustment and the use of KDTA.     

Simultaneous Polarographic Determination of Lead (II) and TIN (II) by Multivariate Calibration

ABSTRACT

The polarographic waves of lead (II) and tin (II) overlap due to their similar reductive potentials and it is difficult to determine these two components simultaneously without a pre-separation. In this paper, differential pulse polarography (DPP) combined with multivariate calibration approaches, such as classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS), were successfully applied to the resolution of overlapping polarographic waves of these two components in the concentration range of 0.05-3.50 mg 1^?1. Satisfactory quantitative results were obtained.     

Polarographic study of hydrogen peroxide anodic current and its application to antioxidant activity determination

Behavior of hydrogen peroxide in alkaline medium has been studied by direct current (DC) polarography with dropping mercury electrode (DME) aiming to apply it in antioxidant (AO) activity determination. Development of a peroxide anodic current having form of a peak, instead of common polarographic wave, has been investigated. As a base for this investigation the interaction of H₂O₂ with anodically dissolved mercury was followed. Formation of mercury complex [Hg(O₂H)(OH)] has been confirmed. The relevant experimental conditions, such as temperature, concentration and pH dependence, as well as time stability of hydrogen peroxide anodic current, have been assessed. Development of an AO assay based on decrease of anodic current of hydrogen peroxide in the presence of antioxidants (AOs) has been described. Under optimized working conditions, a series of benzoic acids along with corresponding cinnamate analogues have been tested for hydrogen peroxide scavenging activity. In addition, the assay versatility has been confirmed on various complex samples.     

Electrochemical Reduction of Benzaldehyde as its Girard-P Derivative at the Mercury Electrode and Differential-Pulse Polarographic Determination of Benzaldehyde

 The polarographic behaviour of benzaldehyde as its Girard-P derivative was studied using various electrochemical techniques and a method for the determination of benzaldehyde (10⁻⁶ − 8 × 10⁻⁵ M) by differential-pulse polarography, based on the in situ formation of its Girard-P derivative in aqueous solution at pH 2.5, is proposed. The relative standard deviation was 1.7% (ten determinations at the 5 × 10⁻⁵ M level). The applicability of this method is checked in benzyl alcohol and synthetic samples containing, o-aminophenol, 2-amino pyridine, o-cresol, amylic alcohol, salicylic acid, 4-aminobenzoic acid and naphthalene sulfonic acid. Received April 6, 2000. Revision February 13, 2001.     

Electroanalytical Study of the Antioxidant and Antitumor Agent Curcumin

Curcumin (CU) shows a wide range of pharmacological properties including antioxidant, anti‐inflammatory, and antitumor effects. In order to understand the chemical basis of different activities of curcumin, we have studied the oxidation and reduction of curcumin. Based on cyclic and differential pulse voltammetric methods, using carbon paste and hanging mercury drop electrodes, in the present study we tested different parameters to optimize the conditions for the determination of curcumin and its electrochemical characteristics. Better results were obtained via differential pulse voltammetry using carbon paste electrode. Curcumin yields well‐defined differential pulse voltammetric responses with well‐defined oxidation (in the potential region of 0.3–0.6 V, vs. Ag/AgCl) and reduction (at 0.3 V) peaks using carbon paste electrode.     

秋水仙碱的电化学性质及电分析方法研究

本文研究了抗癌药物秋水仙碱在玻碳电极上的电化学行为。在HAc NaAc缓冲溶液中,秋水仙碱在玻碳电极上产生一不可逆的氧化峰,峰电位为1.22V(vs.SCE)。用差示脉冲伏安法测定,峰电流与秋水仙碱浓度在8.00×10-7～1.00×10-5mol/L范围内有良好的线性关系,检出限达1.00×10-7mol/L。将之应用于模拟血清样品的测定,结果令人满意。同时,对电极反应机理进行了初步探讨。     

Simple,Rapid and Sensitive Electrochemical Method for the Determination of the Triketone Herbicide Sulcotrione in River Water Using a Glassy Carbon Electrode

We report a novel, simple, rapid and sensitive electrochemical method for the determination of sulcotrione, a member of the relatively new class of triketone herbicides, using differential pulse voltammetry on a glassy carbon electrode. Its electrochemical behavior including influences of electrolyte composition, pH and scan rate was studied to select optimal experimental parameters for its determination. In Britton? Robinson buffer at pH 3 sulcotrione provided a well‐defined reduction peak at ?0.84 V (vs. Ag/AgCl electrode), with good repeatability (relative standard deviation of 2.3 % for 8 measurements at 10 µM concentration level). With optimized parameters differential pulse voltammetry rendered two linear concentration ranges from 0.2 to 2 µM and from 2 to 50 µM with a detection limit of 0.05 µM. The proposed procedure was successfully applied to the determination of sulcotrione in spiked river water samples with satisfactory recoveries (93–109 %). The developed method may represent a simple, rapid and sensitive alternative to highly toxic mercury electrodes and chromatographic methods.     

In Situ Amperometric Detection of Vesicles and Microgel Phases in an Aggregating System: Calcium Alginate

In situ amperometric characterization of an aggregating system in terms of molecular adsorption and single microparticle interactions at the electrode interface is demonstrated using a model system: alginate/Ca(II) in an aqueous electrolyte solution. Recording of chronoamperometric curves of oxygen reduction at the dropping mercury electrode is designed for detection of dip‐shaped signals of individual gel microparticles. By addition of Ca(II) decrease of alginate adsorption is accompanied by appearance of signals indicating vesicle type association of alginate molecules and microparticles of gel phase. AFM imaging provided evidence of initial stage in calcium alginate gel formation.     

铌钼杂多酸的极谱行为及其应用于铌的测定

在ｐＨ２．５的硫酸、抗坏血酸溶液中，铌与钼形成了具有电活性的铌钼蓝杂多酸，并在ｐＨ８．８的ＮＨ３－ＮＨ４Ｃｌ溶液中可在滴汞电极上于－１．１０Ｖ（ｖｓ．ＳＣＥ）产生一灵敏的还原波。导数波高与铌量在０．００５￣０．４ｍｇ／Ｌ范围内呈线性关系。研究了极谱波性质，证明其为吸附波，电极反应属于准可逆。求得电极反应中电子转移数及质子转移数均为２。应用本法已测定了合金钢标样中的铌。     

金钼蓝杂多酸极谱行为及痕量金的测定

在０．０２ｍｏｌ／Ｌ盐酸和Ｖ－溶液中，金（Ⅲ）与钼酸铵形成金钼蓝杂多酸，在ＰＨ１０．０的ＮＨ３－ＮＨ４Ｃｌ缓冲溶液中于－１．１８Ｖ产生灵敏的极谱还原波，导数波高与金浓度在０．５￣１２０μｇ／Ｌ范围内呈线性关系。方法应用于矿样（经泡塑分离富集）中金的测定，结果满意，研究了极谱波性质，证实了其为吸皮，电极反应不可逆。求得电极反应中电子转移数及质子转移数均为２。     

Application of Net Analyte Signal Standard Addition Method (NASSAM) for Simultaneous Determination of Lead and Tin by Differential Pulse Polarography

Differential pulse polarography was used for simultaneous determination of Sn²⁺ and Pb²⁺. But there is a problem for simultaneous determination and it is high overlapped DPPs of mentioned cations that their determination is impossible in the presence of each other, so multivariate calibration methods as chemomatrics methods were used for this determination. There are some disadvantageous for multivariate calibration methods that can be solved by a new and simple method called net analyte signal standard addition method. This method has some advantages, such as: the use of a full voltammogram, realization in a single step, therefore it does not require calibration and prediction steps and only a few measurements are required for the determination.     

Polarographic study on the evolution of the diphenylamine as stabiliser of the solid propellants

Differential pulse polarography (DPP) and square wave voltammetry (SWV) were investigated, in order to know the stability of solid propellants which contain diphenylamine. The simultaneous determination of N-nitrousdiphenylamine (NnDPA), 2-nitrodiphenylamine (2nDPA), 4-nitrodiphenylamine (4nDPA) and 2,4-dinitrodiphenylamine (2,4dnDPA) by DPP and SWV was proposed due to these nitro-derivatives appear during the stabilisation process from degradation of diphenylamine (DPA) used as stabiliser in propellant compositions. The proposed methods were successfully applied to the simple base solid propellant (with nitrocellulose as the only active component), with its stabiliser DPA. In all cases and with both the techniques, detection limits ≤0.01 ppm were obtained.When the usual LC procedure was applied to the real sample, no significant differences were found between the obtained results and those given by the electroanalytical techniques. In addition, the detection limits reached by the electrochemical methods were better than those obtained by LC.Moreover, the proposed procedure can be considered an objective test that would avoid the use of the classic stability tests and would allow one to determine the stability of propellants accurately, faster and cheaper than LC methods.     

A new and direct method for the trace element determination in cauliflower by differential pulse polarography

Using the DPP polarograms of wet digested cauliflower sample in acetate buffer at pH values of 2, 4 and 6, Fe, Zn, Mo, Se, Cr, Cd, Pb, Ti and Cu quantities were determined. The best separation and determination conditions for Zn, Se and Mo was pH 2; for Cr, Zn, Mo and As was pH 4; for Pb pH 6, for Ti, Cu and Fe was pH 6-7 EDTA, for Cd pH 2 EDTA and for lead pH 6, all in acetate buffer. The trace element ranges for cauliflowers from two different seasons were (first figure for winter, the second for summer) for Se 120-250 μg g⁻¹, Fe 70-85 μg g⁻¹, Cu 320-150 μg g⁻¹, Ti 90-120 μg g⁻¹, Cr 130-630 μg g⁻¹, Zn 90-550 μg g⁻¹, Mo 170-230 μg g⁻¹, Cd 20 μg g⁻¹ (in winter) and Pb 130-300 μg g⁻¹ in dry sample. Cd was under the detection limit in summer. The length of digestion time had no effect on the recovery of copper, iron, molybdenum and zinc between 15 and 3 h of digestion.     

Components of the Net Current in Differential Pulse Polarography. Part 2. Kinetics and Adsorption

Components of the net response in differential pulse polarography were studied theoretically, assuming gradually changing electrode rate constant or strength of the reactant adsorption. The difference between the maximum potential of the peak component and the half‐wave potential of the wave component appear as an important parameter. From its value, the electrode rate constant can be calculated even when the standard potential is not known. In a reversible process, effects of the reactant adsorption on the mentioned separation are less pronounced. The results were compared with experimentally obtained effects. For deeper insight into the applicability of this approach, additional experimentally obtained polarograms (that reflect different potential/timing parameters or changing character of the electrode process) should be studied in terms of their components.     

Protonation constant of monoaza-12-crown-4 ether and stability constants with selected metal ions in aqueous solution in the presence of an excess of sodium ion: a potentiometric and differential pulse polarographic study at fixed ligand to metal ratio and varied pH

The ligand monoaza-12-crown-4 ether (A12C4) was studied in aqueous solution at 298 K and an ionic strength of 0.5 mol dm⁻³ in the presence of an excess of sodium ion (0.5 mol dm⁻³ NaNO₃). The protonation constant of A12C4, determined by glass electrode potentiometry (GEP) in the same background electrolyte, was found to be log K=9.36±0.03. Polarographic experimental and calculated complex formation curves (ECFC and CCFC) for labile metal–ligand systems, studied at a fixed total ligand (L_T) to total metal (M_T) concentration ratio and varied pH, were used for the modelling of the metal species formed and the refinement of their stability constants. The metal–ligand model and formation constants are optimised by solving mass-balance equations written for the assumed model and by fitting the CCFC to the ECFC. The CCFC can be generated for any metal–ligand model, including polynuclear metal species, for any L_T:M_T ratio, and for more than one ligand competing in the complex formation reaction. Three lead complexes with the ligand A12C4, viz. PbL²⁺, PbL(OH)⁺ and PbL(OH)₂, were found and their overall stability constants from differential pulse polarography (DPP), as log β, were estimated to be 3.75±0.03, 9.30±0.05 and 12.70±0.05, respectively. Two copper complexes CuL²⁺ and CuL(OH)₂ are reported and their stability constants (from DPP) were estimated to be 6.00±0.05 and 21.77±0.1, respectively. Two cadmium complexes CdL²⁺ and CdL(OH)⁺ are reported. The stability constant for CdL²⁺ was estimated from DPP and GEP as 2.80±0.05 and 2.68±0.03 (the latter value was obtained from a few potentiometric experimental points), respectively, and the stability constant for CdL(OH)⁺ from DPP was estimated to be 7.88±0.05. GEP could not be used for the stability constants determination of other metal complexes studied because of precipitation occurring prior the completion of a complex formation reaction.     

Dediazoniation of Arenediazonium Ions in Homogeneous Solutions. Part XVII. Kinetics and mechanisms of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate in weakly alkaline aqueous solutions in the presence of oxygen

The kinetics of dediazoniation of p-chlorobenzenediazonium tetrafluoroborate have been studied in buffer solutions in the pH-range 9.0–10.0, ionic strength I = 0.10, at 20.0° in glass and polytetrafluoroethylene vessels. The presence of oxygen (<5 ppb of O₂, 60 to 100 ppb of O₂, air, > 99% of O₂) has a decisive influence on the rate and kinetic order of the dediazoniation. Iodoacetic acid inhibits the reaction, whereas p-chlorophenol has a catalytic effect, and in air and >99% of O₂ it acts as an autocatalyst. The reaction is subject to general-base catalysis by water, hydroxyl ions, hydrogen carbonate and carbonate ions. The kinetic results are interpreted in conjunction with data concerning the reaction products [2] and a ¹⁵N-CIDNP. investigation of a related system [3]. Specific radical chain mechanisms are consistent with the results.