Reciprocal derivative constant-current stripping analysis

Reciprocal derivative constant-current stripping analysis (RD-CCSA) is based on the measurement of dt/dE converted from a derivative signal, dE/dt, vs. electrode potential (E) during the stripping of analyte under galvanostatic conditions from a mercury-film electrode after preconcentration. The potential transient signal (E-t) in normal chronopotentiometric stripping analysis (CPSA) is converted in RD-CCSA into a stripping peak (dT/dE)(p) the height of which is proportional to the bulk concentration of analyte in solution. The theory of RD-CCSA has been derived, and validated by the good correlation obtained between the theory and experimental data. Compared with normal CPSA, RD-CCSA is more sensitive and has higher resolution. The detection limit for cadmium is 6 x 10(-10)M. Simultaneous determination of Cd(2+), In(3+), and Tl(+) (for which the differences between the stripping peak potentials are 58 and 50 mV, respectively) which is impossible for normal CPSA, voltammetry or differential pulse polarography, has become possible with RD-CCSA.     

平面汞膜电极二阶倒导数电位溶出分析法研究

对电位溶出的Ｅ－ｔ曲线进行二阶倒导数处理，提高了二阶倒导数电位溶出分析法理论，其信号较一阶倒导数法增强约４３．１ｎ倍，分辨率由原来的６５．５ｍＶ／ｎ改善到４８．２ｍＶ／ｎ。用根据二阶倒导数法原理自行设计研制的多阶倒导数电位出仪验证了本提出了的理论，富集１２０ｓ，Ｃｄ＾２＋的检测限可达１．０×１０＾－１０ｍｏｌ／Ｌ。     

Catalytic stripping analysis: sensitivity enhancement for reciprocal derivative constant-current stripping determination of palladium in the presence of tin(II) during stripping

The reciprocal derivative constant-current stripping signal of palladium at a mercury film electrode is increased, as in anodic stripping voltammetry (ASV), by a factor of ca. 80 if a certain amount of tin(II) is present in the stripping solution. This catalytic stripping phenomenon has been successfully used as a means of sensitivity enhancement in constant-current stripping determination of trace palladium. The limit of detection is 4 x 10(-10)M at S/N = 3, which is about two decades lower than that obtained without tin(II) present. Linear response was observed over the range 10(-10)-10(-7)M. This method has been applied to determine palladium in waste water and mineral samples. The experimental results support the postulated mechanism of signal enhancement, namely a chemical redeposition reaction occurring during the stripping, giving a cycle of stripping and deposition and thus increasing the stripping signal.     

倒数示波计时电位法

使用dE/dt的倒数对E作图的示波计时电位法,称为倒数示波计时电位法.dE/dt-E曲线上的切口在dE/dt^-1-E上变成峰,可以方便地扣除充电电流,提高分析测试的灵敏度.     

铋膜电极微分电位溶出法测定生物材料中痕量铅

研究了镀铋膜电极替代镀汞膜电极痕量铅的微分电位溶出分析法(DPSA)。考察并优化了同位镀铋膜测定铅的条件。结果表明,在HAc-NaAc(pH=4.4)介质中,铅可在镀铋膜电极上得到灵敏的微分电位溶出峰;利用标准加入法对人尿及血中痕量铅进行了测定。本法避免了镀汞膜电极对人体健康及环境的危害。     

电化学预处理玻碳电极微分计时电位溶出法测定DNA中的嘌呤碱基及DNA浓度

研究了鸟嘌呤(G)、腺嘌呤(A)、鸟嘌呤核苷、腺嘌呤核苷和变性DNA在电化学预处理玻碳电极上的恒电流微分计时电位溶出行为. 实验结果表明, 用电化学方法预处理玻碳电极操作简单, 效果明显, 预处理玻碳电极对嘌呤及其核苷和DNA的吸附能力大大增强, 用微分计时电位溶出法可以得到灵敏的溶出峰, 溶出峰高(dt/dE)与其浓度在一定范围内呈良好的线性关系, 可用于嘌呤碱基及其核苷的定量检测和DNA浓度的测定. 将该方法应用于酸变性DNA样品中鸟嘌呤与腺嘌呤的同时测定, 选择性好、灵敏度高; 还可获得有关DNA损伤的一些信息.     

Absolute analysis of trace metals through galvanostatic stripping chronopotentiometry with signal accumulation

An electrochemical flow-through cell with a porous working electrode made of vitreous carbon particles and plated with mercury was used for the absolute determination of Pb using galvanostatic stripping chronopotentiometry in a flow system. After completing the potentiostatic electrodeposition of the analyte from the flowing sample solution the flow was stopped and oxygen in the solution inside the pores of the electrode was removed by reducing it. The deposit was then stripped by applying a constant current of 50 to 1000 A and the measured potential vs time (E vs t) data were converted to the dt/dE vs E dependence by a memory mapping technique. Owing to the thin layer properties of the cell, the stripping/deposition steps could be repeated reproducibly enabling the accumulation of the signals while improving the signal to noise ratio. The method was also found to be suitable for the simultaneous determination of Cd, Pb and Cu. The experimental conditions, computerized data handling and signal processing have been investigated. Water, grass and sediment samples were analyzed for traces of Pb.     

硒碳糊电极微分电位溶出法测定铜和铋

建立了掺杂硒碳糊电极同时测定铜和铋的微分电位溶出法。在HCl(0.05mol/L)中,在-0.3V(vs.Ag/AgCl)下,Cu2+和Bi3+电沉积在电极表面,再在溶液中溶解氧的作用下,铜和铋从电极表面溶出,分别于0.30V和0.02V获得灵敏的电位溶出峰。微分电位溶出峰高(dt/dE)与铜和铋的浓度成线性关系,线性范围为5.0×10-9～1.55×10-7mol/L,检出限分别为4.0×10-9和2.5×10-9mol/L(S/N=3)。方法用于实际样品中铜和铋的测定,结果令人满意。     

Simultaneous determination of mercury(II), copper(II) and bismuth(III) in urine by flow constant-current stripping analysis with a gold fibre electrode

Urine samples are treated with concentrated nitric acid and potassium permanganate ar 70°C for 10 min prior to injection. The flow electrode system consists of a 10-μm diameter gold fibre working electrode, a glassy carbon reference electrode and a platinum counter electrode. In the fully automated constant-current stripping procedure, the gold fibre is first covered with a fresh gold film after which the sample is electrolyzed for 1 min prior to stripping in 0.1 M hydrochloric acid with a current of 0.1μA. The procedure is repeated on a spiked sample after which the sample analyte concentrations are evaluated and presented digitally and graphically on a printer/plotter. The results obtained for bismuth, copper and mercury in a urine reference sample were 36.9, 39.7 and 47.7 μg l^?1 with standard deviations (n=10) of 3.2, 4.2 and 2.1, respectively. The certified values for copper and mercury were 45 and 51 μg l^?1; no certified value was available for bismuth.     

Investigations on Adsorption Potentiometry Part V Derivative Adsorption Chronopotentiometry of Beryllium(II)-4-[(4-diethylamino-2-hydroxypheanyl)-azo]-5-hydroxy-naphthalene-2,7-disurphonic Acid System

Abstract

An electroanalytical methood, based on derivative chronopotentiometry of the complex of beryllium(II) with 4-[(4-diethylamino-2-hydroxy-phenyl)-azo]-5-hydroxy-naphthalene-2,7-disurphonic acid (Beryllon II) accumulated adsorptively on the surface of a hanging mercury drop electrode, has been developed for determining trace beryllium in food. The dependences of the peak height on the dt/dE vs. E curve on the pre-concentration time, preconcentration potential and the constant reducing current are discussed. In 0.15 mol/1 NH_s+0.05 mol/1 NH₄Cl, 4×10^?7 mol/l Beryllon II, and at a preconcentration potential of -0.30 V (ve. SCE), the limit of detection and linear range are 1 × l0^?10 mol/l and 3 × 10^?10 -2 × l0^?7 mol/l, Iwpectively. The relative standard error of the method is 2.3% for 6 × 10^?8 mol/l Be(II). The method WBB applied to samples of food. The electrode procees hae been diecueeed.     

The cyclic renewable mercury film silver based electrode for determination of molybdenum(VI) traces using adsorptive stripping voltammetry

The new cyclic renewable mercury film silver based electrode (Hg(Ag)FE), applied for the determination of molybdenum(VI) traces using differential pulse adsorptive cathodic stripping voltammetry (DP AdSV) is presented. The Hg(Ag)FE electrode is characterized by very good surface reproducibility (相似文献   

Flow potentiometric and constant-current stripping analysis for mercury(II) with gold,platinum and carbon fibre working electrodes : Application to the Analysis of Tap Water

Gold, platinum and carbon fibres with 10-μm diameter were mounted in PVC tubes and used as flow sensors in computerized potentiometric and constant-current stripping analysis for mercury, after electroplating ofa gold film onto the fibre surfaces. Compared to gold and glassy carbon disc electrodes, the fibre electrodes gare increased sensitivity and stability and were considerably simpler to handle. The gold-coated carbon fibre electrode gave a higher background than the gold fibre electrode, in both the potentiometric and constant-current stripping modes. Mercury(II) could be determined in presence of a 10⁵-fold (molar) amount of copper(II) by constant-current stripping in media with chloride concentrations below 0.05 M. The detection limit for mercury(II) after 10 min of electrolysis was 45 ng l^?1 at the 3 σ level.     

倒数示波计时电位滴定法

提出了一种新的电滴定分析方法——倒数示波计时电位滴定法。它利用(dE/dt)~(-1)-E曲线上去极剂峰的出现或消失指示滴定终点,较经典示波滴定法灵敏,对(dE/dt)~(-1)-E曲线进行反对数非线性放大,则可以使终点峰形突变更加敏锐.     

Interaction between co-deposited metals during stripping voltammetry at boron-doped diamond electrodes

Electrochemical processes, which underlie the use of conductive diamond electrodes for the simultaneous detection of two or more metal ions in solution by anodic stripping voltammetry (ASV), have been investigated. The model analyte system studied contains the two metal species, Ag+(aq) and Pb2+(aq), and the experimental techniques employed include cyclic and square wave voltammetries, along with X-ray photoelectron spectroscopy and secondary electron microscopy. Although the bulk metallic forms of Ag and Pb are immiscible, several interactions in the system between the two metal species present are observed, which significantly influence the electrodeposition and electrodissolution processes which underlie ASV. The subsequent nucleation and growth of a given metal on the electrode surface is enhanced by the presence of the second metal on the surface. The encapsulation of one metal by the other, within the metal particulates that form on the electrode surface, significantly reduces the stripping yield at the potentials characteristic of the individual metals. The stripping potentials are also influenced by bonding interactions between deposited Ag and Pb, which broaden the characteristic stripping peaks in cyclic voltammetry, as well as producing underpotential deposition and stripping. Given these interactions, the extent to which ASV at diamond electrodes can be used to determine the solution concentrations of Ag+(aq) and Pb2+(aq) is considered.     

Flow potentiometric and constant-current stripping analysis for silver(I) with carbon- and platinum-fibre electrodes

At concentrations above 50 μg l^?1, silver(I) is determined in nitric acid medium by means of potentiostatic deposition onto a platinum-fibre electrode and subsequent constant-current stripping in the sample or potentiometric stripping in a potassium permanganate medium. Interference from copper(II) is reduced by a pulsed potential procedure whereby copper deposited onto the fibre electrode is reoxidized intermittently. At concentrations below 50 μg l^?1, silver(I) is determined by using a mercury-coated carbon-fibre electrode and constant-current stripping in acetonitrile containing 0.20 M perchloric acid. Potentiostatic deposition for 30 min yielded a detection limit of 0.24 μg l^?1 silver(I) at the 3σ level.     

利用碘离子增感效应和金电极导数阳极溶出法研究铜丶铅和镉的同时测定

A method of simultaneous determination of copper (II), lead (II) and cadmium (II) in sulphuric acid-iocide ion medium was established by derivative anodic stripping voltammetry (DASV) on the gold electrode. The peak theights of lead and cadmium were increased by enhancement effect of iodide ion and the peaks of bismuth and copper were well formed and completely resolved on gold electrode in the presence of iodide ion, therefore peak of copper is not affected by bismuth. The sensitivities for copper, lead and cadmium were very high and their peak potentials in the stripping voltammogram were +0.25, -0.2 and -0.27 volt, respectively. The dependence of peak height of these elemets on their concentrations was linear. The detection limits for copper, lead and cadmium were 0.2 0.2 and 0.05 ppb, respectively. We have further studied the electrode process by means of triangle cyclic voltammetry and proved that he electrode reaction of copper is reversible, and that the reversibility of electrode reactions of lead and cadmium is not good.     

水杨酸在改性钠基蒙脱土修饰电极上的电化学行为及测定

用十六烷基三甲基溴化铵(CTAB)对钠基蒙脱土进行改性,并用红外光谱、X衍射对CTAB-NaMMT进行表征,制备了改性钠基蒙脱土修饰电极(CTAB-NaMMT-CMC/GCE),研究了水杨酸在该修饰电极上的循环伏安行为.结果表明,在pH 0.8的H_2SO_4-Na_2SO_4电解质溶液中,SA在1.19 V出现一明显的氧化峰,在40 ～400 mV/s范围内,其氧化峰电流与扫描速率的平方根(v~(1/2))呈良好线性关系,表明电极过程为受扩散控制不可逆过程.测得SA在该修饰电极上的反应电子数、质子数、传递系数及扩散系数分别为2、2、0.389、1.275×10~(-6) cm~2/s.方波溶出伏安法的氧化峰电流(I_(pa))与SA浓度在8.0×10~(-7) ～1.25×10~(-4) mol/L范围内呈良好的线性关系(r=-0.999 6),检出限为2.27×10~(-7) mol/L,加标回收率为96% ～101%.     

Novel disposable bismuth-sputtered electrodes for the determination of trace metals by stripping voltammetry

This work describes a novel type of bismuth electrode for stripping voltammetry based on coating a silicon substrate with a thin bismuth film by means of sputtering. The bismuth-based sensors were characterized by optical methods (scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD)) and as well as by linear sweep voltammetry. Subsequently, the electrodes were tested for the detection of low concentrations of trace metals (Cd(II), Pb(II) and Ni(II)) by stripping voltammetry. Well-formed stripping peaks were observed for trace concentrations of the target analytes demonstrating “proof-of-principle” for these sensors. This type of electrochemical device, utilizing thin-film technology for the formation of the bismuth film, holds promise for future applications in trace metal analysis.     

恒电流吸附计时电位法的研究 Ⅱ.铜、铅的微分吸附计时电位法连测

研究了ＮＨ３／ＮＨ４Ｃｌ底液中，铜、铅与水杨基荧光酮（ＳＡＦ）形成的络合物在悬汞电极上的恒电流吸附计时电位溶出行为。讨论了富集时间，溶液ｐＨ值，溶出恒电流大小及铜、铅浓度比值等对ｄｔ／ｄＥ～Ｅ溶出曲线的影响。并得出了连测铜铅的条件。     

交流示波极谱法中i~f-E曲线的研究 7:基于i~f-E曲线的定量分析方法

本文提出基于i~f-E曲线的定量分析方法,并在自行研制的微机电化学数据采集系统上,测定了微量的Tl^+、Pb^2+、Cd^2+、Zn^2+、Mn^2+和Ga^3+.结果表明,与经典的dE/dt-E曲线方法相比,i~f-E曲线方法的准确度提高了2-5倍、灵敏度提高了一个数量级.