Voltammetric Determination of Sulfide Ions

Procedures were proposed for the voltammetric determination of S^2– at a mercury-film electrode. They are based on the oxidation of S^2– at –0.79 to –0.80 V and on the reduction of HgS, the product of the oxidation of S^2–, at –0.76 to –0.96 V in a 1 M NaOH solution. The anodic and cathodic currents are linear functions of S^2– concentration in the ranges from 1 × 10^–5 to 1 × 10^–4 M and from 2 × 10^–6 to 1 × 10^–4 M, respectively.     

吡柔比星在羧基离子注入氧化铟电极上的电化学还原及其测定

采用离子注入技术将羧基离子注入到氧化铟锡(ITO)表面,制备了羧基离子注入氧化铟锡电极(COOH/ITO).电极表面羧基的引入用X射线光电子能谱(XPS)进行表征.此电极被应用到了吡柔比星的电化学行为的研究及其测定当中.在COOH/ITO电极上,吡柔比星在5 nmmol/L磷酸盐缓冲溶液(pH 7.2)中,出现还原峰,...     

Voltammetric Determination of ITX in Hydro-Alcoholic Solutions and Wine

An electrochemical method to detect the Isopropyl-9H-thioxanthen-9-one (ITX), a sulfur-type photo-initiator widely used in UV-curing techniques to promote the polymerization of inks, in a hydro-alcoholic solution, has been developed and tested in a commercial wine sample. The experimental parameters of electroanalytical techniques, mainly differential pulse voltammetry (DPV), as well as the alcohol/water ratio have been optimized to improve the sensitivity and to lower the minimum detectable value. The proposed analytical method has been tested on real samples of commercial wine finding out a decision limit of 2.3 × 10^?7 M and a minimum detectable value of 4.5 × 10^?7 M.     

兴奋剂马钱子碱的电化学氧化及其伏安法测定

以玻碳电极为工作电极，硫酸钾为支持电解质，在合适的ｐＨ条件下，通过循环伏安法，首次观测到了马钱子碱的不可逆氧化峰。在浓度为２０×１０－４～４０×１０－３ｍｏｌ／Ｌ范围内其峰电流与浓度呈线性关系，检测限为１０×１０－５ｍｏｌ／Ｌ。在正常人体的尿样中，采用标准加入法进行回收实验，其平均回收率为１００８％。该法简便、快速，用５０×１０－４ｍｏｌ／Ｌ的马钱子碱溶液重复测定１０次，相对标准偏差为１８％。对其反应机理作了初步探讨。     

Determination of Caffeic Acid in Red Wine by Voltammetric Method

The electrochemical oxidation of 3,4‐dihydroxycinnamic acid, caffeic acid, leads to a stable electroactive poly(caffeic acid) thin film containing quinone moiety on a preactivated glassy polymeric carbon electrode. The properties of the deposited films as well as the stability study under different experimental conditions were investigated. Taking advantage of the electrochemical behavior, an analytical method based on differential pulse voltammetry for determination of caffeic acid in red wine was proposed.     

褪黑素的电化学氧化行为及伏安法测定

采用电化学方法研究了褪黑素在金电极上的不可逆氧化行为.结果表明：其伏安过程为受弱吸附和扩散共同控制的过程,氧化反应电荷转移数为2.采用伏安法对褪黑素进行测定,方法的检出限可达10^-10ml/L数量级.方法可用于脑白金胶囊中褪黑素含量的测定.     

单宁的电化学氧化及伏安测定法

以玻碳电极（ＧＣＥ）为工作电极，ＫＨ２ＰＯ４－Ｎａ２ＨＰＯ４为支持电解质，通过循环伏安法首次观测到了单宁的不可逆氧化峰。在单宁浓度为１．０×１０～（－７）～１．２ × １０～（－５）ｍｏｌ／Ｌ范围内与其峰电流呈线性关系；检出限为 １．３×1０～（－８）ｍｏｌ／Ｌ。在中药五倍子浸提液中用标准加入法进行回收实验，其平均回收率为１００．６％。该法简便、快速，用１．０×１０～（－６）ｍｏｌ／Ｌ的单宁溶液重复测定１１次，ＲＳＤ为２．ｌ％。对其反应机理作了初步探讨。     

大豆黄素的电化学行为及其循环伏安测定

在pH 7.5的三羟甲基氨基甲烷-盐酸(Tris-盐酸)缓冲溶液的底液中,采用循环伏安法测定大豆黄素,得到一良好的氧化峰,其峰电位在0.53 V处;峰电流与大豆黄素的浓度在1.2×10-7～9.6×10-6mol·L-1范围内呈线性关系.该方法的检出限(3S/N)为8.0×10-8mol·L-1.用此法测定红车轴草中大豆黄素含量,加标平均回收率为98.0%;对1.6×10-6mol·L-1大豆黄素平行测定8次,进行精密度试验,相对标准偏差为0.81%.根据大豆黄素在玻碳电极上的电化学行为,表明大豆黄素的电极过程具有吸附性和不可逆性.     

Electrochemical Sensors for the Stripping Voltammetric Determination of Antimony(III)

The conditions of the modification of a glassy-carbon electrode with various polyphenols were studied by multicyclic voltammetry over a wide range of pH. The state of the electrode surface was additionally monitored by measuring cyclic voltammograms of ferrocyanide ions in the presence of a phosphate buffer solution (pH 7.0). It was found that the electrooxidation of all the studied polyphenols at the electrode surface resulted in the formation of a water-insoluble film which is capable of accumulating antimony(III) from aqueous solutions. The surface concentration of chemically active cites was of the order n × 10^–9 M/cm². The electrochemical sensors thus prepared were found to be suitable for the selective determination of antimony(III) by adsorption stripping voltammetry. The maximum signals of antimony(III) were obtained at electrodes modified with pyrocatechol and pyrogallol upon metal deposition from acetate buffer solutions (pH 4.5). The detected peak areas S (A · s) were directly proportional to the deposition time t _d (min) and the concentration of antimony(III). The analytical range was 10–250 g/L at t _d = 5.0 min, and the detection limit was 6 g/L. It was found that a sensor based on a pyrogallol film can selectively determine antimony(III) in the presence of Sb(V), Cu(II), and Pb(II), and can be used for the analysis of natural water.     

A New Voltammetric Approach for Electrochemical Determination of Lamotrigine in Pharmaceutical Samples

A new linear sweep voltammetric method for quantitative lamotrigine (LMT) determination based on an electrochemically pre-treated pencil graphite electrode (PGE*) is presented. Response characteristics of the PGE* toward the mentioned compound were investigated by cyclic voltammetry and linear sweep voltammetry. The quantitative determination of LMT revealed a wide linear range of 2.5 ⋅ 10⁻⁵–1.0 ⋅ 10⁻³ M with a detection limit of 1.94 ⋅ 10⁻⁵ M. The method was used successfully for LMT determination in a pharmaceutical formulation.     

香兰素在玻碳电极上的电化学行为及其循环伏安测定

在pH 7.5的Tris-HCl缓冲介质的底液中,在循环伏安图上在峰电位+0.54 V处可见到香兰素的灵敏的氧化峰.其峰电流Ip与香兰素的浓度在3.286×10-6～3.944×10-4mol·L-1范围内呈线性关系,检出限(3S/N)为1.643×10-6mol·L-1.据此提出了循环伏安测定香兰素的方法,并应用于测定巧克力中香兰素的含量.在巧克力试样中加入不同浓度的香兰素标准,按方法测定以求测定方法的回收率,研究了香兰素在玻碳电极上的电化学行为,结果表明:香兰素的电极过程具有吸附性和不可逆性.     

Electrochemical Oxidation of Donepezil and Its Voltammetric Determination at Gold Electrode

The oxidative ability of donepezil, a frequently prescribed drug for the treatment of Alzheimer’s disease is reported for the first time at a gold electrode. It was oxidized by cyclic voltammetry and determined by square wave voltammetry in phosphate buffer electrolyte. Electrochemical degradation of donepezil was carried out by long term potential cycling. The identification and characterization of the major product, isolated by preparative high performance liquid chromatography, was performed by high resolution mass spectrometry and 1D and 2D nuclear magnetic resonance spectroscopy. Donepezil hydroxy derivative was identified as the major electrochemical oxidation product from donepezil.     

Electrochemical Studies of the Neuraminidase Inhibitor Zanamivir and its Voltammetric Determination in Spiked Urine

Zanamivir is a member of a new class of antiviral agents that selectively inhibit the enzyme neuraminidase of influenza A H5N1 and H1N1 viruses. Although zanamivir is the compound of biological interest, so far it has not been a subject of any electrochemical studies. It was stated, that zanamivir can act as an electrocatalyst at HMDE. The electrode mechanism is connected with the hydrogen evolution reaction catalyzed by zanamivir as the guanidine compound. A new adsorptive catalytic method for its voltammetric (SW AdSV) determination was developed. The dependence of the peak current on pH, buffer concentration, nature of the buffer and instrumental parameters were studied. The best results were received in citrate‐phosphate buffer at pH 2.2. This electroanalytical procedure enabled to determine zanamivir in the concentration range 4.8×10^?7–1.2×10^?5 mol L^?1 in supporting electrolyte and diluted urine. Precision, repeatability and accuracy of the method were checked in both media. The detection and quantification limits were found to be 1.5×10^?7 and 4.8×10^?7 mol L^?1 respectively. A standard addition method was used to determine zanamivir in spiked urine.     

Effect of Lactic Acid on the Electrochemical Determination of Iodide Ions

The results of a study of the effect of lactic acid on the determination of trace iodide ions by stripping voltammetry (SVA) and potentiometry with ion-selective electrodes are presented. In the latter case, the interference of lactic acid was eliminated by adding 30% ethanol to the test sample, whereas various sample preparation procedures with test sample decomposition were used in SVA.     

铋膜电极溶出伏安法测定食品中痕量重金属

以铋膜电极为工作电极,采用微分脉冲阳极溶出伏安法直接测定食品样品中痕量铅、镉和锌。在富集电位-1.4V,富集时间180s,铋膜质量浓度150μg·L-1的条件下,铋膜电极对铅、镉和锌的氧化溶出具有良好的电化学响应。铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)的质量浓度在5.0~40μg·L-1的范围内与其阳极溶出峰电流呈线性关系,铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)的检出限(3S/N)分别为0.80,0.65,0.58μg·L-1。对25μg·L-1铅(Ⅱ)、镉(Ⅱ)和锌(Ⅱ)溶液用铋膜电极连续测定15次,相对标准偏差分别为6.2%,5.1%,7.1%。方法应用于食品中痕量重金属的测定,测定结果与石墨炉原子吸收光谱法的测定值相符。     

离子色谱法测定固体样品中杂质离子的样品处理方法

离子色谱法(IC)是20世纪70年代发展起来的一项液相色谱技术,主要用于水溶液中阴、阳离子或离子型化合物的分析,是分析阴离子的首选方法。对于微量成分的测定来说,随着仪器的灵敏度、精度和自动化程度的不断提高,耗时、繁琐和容易引入误差的样品前处理成为分析过程中的一个难点。在样品前处理方面,针对不同的样品采用相应的样     

石墨烯修饰电极的制备及其对对乙酰氨基酚的伏安测定

利用滴涂的方法制备了石墨烯修饰电极;石墨烯修饰电极对对乙酰氨基酚（ACOP）的电化学氧化具有明显的催化作用。 研究了ACOP在石墨烯修饰电极上的电化学行为,建立了测定ACOP的电化学分析新方法。 考察了磷酸盐缓冲溶液的pH值对ACOP电化学行为的影响。 结果表明,氧化还原峰电位随pH值升高发生负移;在pH=6.0磷酸盐缓冲溶液中,对乙酰氨基酚在修饰电极上呈现一对灵敏的氧化还原峰。 对乙酰氨基酚在石墨烯修饰电极上的氧化峰峰电流与其浓度在6.00×10-7~4.00×10-5 mol/L范围内呈良好的线性关系,相关系数为0.994 0;检出限为5.00×10-8 mol/L。 其回归方程为：ipa(A)=3.00c+1.21×10-5。 该修饰电极具有良好的灵敏度、选择性和稳定性,可用于对乙酰氨基酚药片分析。     

Voltammetric Method for Determining Ferric Ions with Quercetin

A novel, simple, rapid, inexpensive, highly sensitive voltammetric method developed for determining ferric ions with quercetin in water samples and iron supplements using a disposable bare pencil graphite electrode is described. The limit of detection and analytical ranges for the ferric ions were 3.6 nM and 17.9–716.0 nM, respectively. The results with the water samples were compared with those obtained from a potentiometric auto-titration system, and the method's accuracy was tested using certified reference material. The complex stoichiometry and electrode reaction were also systematically investigated with UV-visible spectrophotometry, ¹H-NMR spectroscopy and voltammetry.     

Study on the Determination of Heavy-Metal Ions in Tobacco and Tobacco Additives by Microwave Digestion and HPLC with PAD Detection

A new method for the simultaneous determination of heavy-metal ions in tobacco and tobacco additive by microwave digestion and reversed-phase high-performance liquid chromatography (RP-HPLC) was developed. The tobacco and tobacco additive samples were digested by microwave digestion. The lead, cadmium, mercury, nickel, copper, and tin ions in the digested samples were precolumn derivated with tetra-(4-aminophenyl)-porphyrin (T₄-APP) to form color chelates; the Hg-T₄-APP, Cd-T₄-APP, Pb-T₄-APP, Ni-T₄-APP, Cu-T₄-APP, and Sn-T₄-APP chelates were then enriched by solid-phase extraction with C₁₈ disks and the retained chelates were eluted from the disks using tetrahydrofuran (THF). The chelates were separated on a Waters Xterra RP₁₈ column by gradient using methanol (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH 10.0) and acetone (containing 0.05 mol/L pyrrolidine-acetic acid buffer salt, pH 10.0) as a mobile phase at a flow rate of 0.5 mL/min and detected with a photodiode array detector in the range 350–600 nm. The detection limits of lead, cadmium, mercury, nickel, copper, and tin were 5, 4, 2.5, 5, 8, and 4 ng/L, respectively, in the original samples. The method was applied to the determination of lead, cadmium, mercury, nickel, copper, and tin in tobacco and tobacco additive with good results.__________From Zhurnal Analiticheskoi Khimii, Vol. 60, No. 5, 2005, pp. 542–548.Original English Text Copyright © 2005 by Yang, Li, Shi, Wang.This article was submitted by the authors in English.