Direct determination of sub-nanomolar levels of zinc in sea-water by cathodic stripping voltammetry

A novel technique for the determination of nanomolar levels of zinc in aqueous solution is presented. The zinc complex with ammonium pyrrolidine dithiocarbamate is adsorbed on a hanging mercury-drop electrode and the reduction current of zinc is measured by voltammetry. The detection limit for zinc is 3 × 10⁻¹¹M, with 10-min collection time. A procedure is suggested for the simultaneous determination of Ni and Zn in a single sample.     

Determination of trace metals by anodic stripping voltammetry using a bismuth-modified carbon nanotube electrode

A bismuth-modified carbon nanotube electrode (Bi-CNT electrode) was employed for the determination of trace lead, cadmium and zinc. Bismuth film was prepared by in situ plating of bismuth onto the screen-printed CNT electrode. Operational parameters such as preconcentration potential, bismuth concentration, preconcentration time and rotation speed during preconcentration were optimized for the purpose of determining trace metals in 0.1M acetate buffer solution (pH 4.5). The simultaneous determination of lead, cadmium and zinc was performed by square wave anodic stripping voltammetry. The Bi-CNT electrode presented well-defined, reproducible and sharp stripping signals. The peak current response increased linearly with the metal concentration in a range of 2-100 microg/L. The limit of detection was 1.3 microg/L for lead, 0.7 microg/L for cadmium and 12 microg/L for zinc (S/N=3). The Bi-CNT electrode was successfully applicable to analysis of trace metals in real environments.     

A Study of Nafion‐Coated Bismuth‐Film Electrode for the Determination of Zinc,Lead, and Cadmium in Blood Samples

In this article a sensitive differential pulse stripping voltammetry technique on Nafion‐coated bismuth‐film electrode (NCBFE) was studied for the simultaneous determination of zinc, cadmium, and lead ions in blood samples at ultra trace levels. The measurement results were in excellent agreement with those obtained from atomic absorption spectroscopy. Various operational parameters were investigated and discussed in terms of their effect on the measurement signals. Under optimal conditions, calibration curves for the simultaneous determination of zinc, cadmium, and lead ions were achieved, based on three times the standard deviation of the baseline, the limits of detection were 0.09 μg L^?1 for Cd(II), 0.13 μg L^?1 for Pb(II), and 0.97 μg L^?1 for Zn(II) respectively.     

流动注射多元校正-络合滴定法同时测定混合金属离子

将流动注射应用于电位络合滴定分析法,建立了一种可同时测定混合金属离子的电位滴定方法。在该方法中,用EDTA与氟化钠的混合溶液作为滴定剂,在流通池中同时插入汞膜电极和氟离子指示电极,在滴定过程中的任一滴定点,流出液的汞电位和反应物的混合比例可由两个电极的电位测定值同时获得,从而可应用多元校正法由相应的滴定曲线求得混合金属离子中每一种组分的含量。应用该方法对混合样品中的Cu2+、Pb2+、Zn2+进行了同时测定,测定结果的相对标准偏差均在0.14%~0.48%(n=5)之间,回收率均在97.3%~103.9%之间。     

Adsorptive Stripping Voltammetric Determination of Ultra Trace of Zinc and Lead with Carbidopa as Complexing Agent in Food and Water Samples

In the present work, the cathodic stripping voltammetric methodology using a hanging mercury drop electrode was described for simultaneous determination of lead and zinc in different real samples. The method is based on adsorption of metal ions on mercury electrode using carbidopa as a suitable complexing agent. The potential was scanned to the negative direction and the differential pulse stripping voltammograms were recorded. Optimal conditions were found to be: accumulation time; 70 s, accumulation potential; 50 mV versus Ag/AgCl, scan rate; 40 mV s^?1, supporting electrolyte; 0.01 M ammonia buffer at pH 8.5, and concentration of carbidopa; 8.0 μM. The relationship between the peak current versus concentration was linear over the range of 0.1–210 and 0.2–170 nM for lead and zinc, respectively. The detection limits are 0.09 and 0.15 nM for lead and zinc ions respectively. The relative standard deviations at a concentration level of 70 nM of both metal ions are found 1.08 and 1.24% for lead and zinc ions respectively.     

Determination of trace metals by anodic-stripping voltammetry with a new kind of mercury electrode: The long-lasting sessile-drop electrode

A new kind of semi-stationary mercury drop electrode is described, which can be used for the determination of trace metals in natural waters by differential-pulse anodic-stripping voltammetry. Results are reported for the determination of zinc in potassium chloride and in samples of sea-water. The reproducibility of the electrode and of the results obtained with it for zinc at the 10(-8)M level are very satisfactory.     

多壁碳纳米管修饰电极阳极溶出法测定痕量锌

报道了自制的多壁碳纳米管修饰电极测定锌离子的电分析方法。在浓度0.20mol/L的乙酸钠溶液中,以此修饰电极作为工作电极,以-1.50V为富集电位,150s为富集时间,用方波伏安溶出法(起始电位:-1.5V;终止电位:-0.8V;电位增量:0.01V;振幅:0.05V;频率:5Hz)测定-1.30V处的峰电流,用峰高定量。结果表明,该电极对锌离子吸附的灵敏度较高;当锌离子浓度为1.0×10-6～9.0×10-6mol/L时,线性关系好,相关系数为0.9992;对自来水样本进行了测定,取得了满意的结果,加标回收率在97%～105%之间。     

Simultaneous determination of iron and zinc by pH gradient construction in a flow-injection system

A flow-injection method for the simultaneous determination of iron and zinc in the human hair with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) using a pH gradient technique has been developed. The linear range for the determination of iron is 0.1 approximately 1.8 mug ml(-1) and for zinc is 0.2 approximately 5.0 mug ml(-1). About 20 approximately 30 samples can be determined in 1 h. The proposed method is simple, rapid and accurate. It has been applied to the simultaneous determination of trace amounts of iron and zinc in the human hair with satisfactory results.     

Simultaneous determination of copper, zinc and lead by adsorptive stripping voltammetry in the presence of Morin

A sensitive and selective method for the simultaneous determination of copper, zinc and lead is presented. The method is based on the adsorptive accumulation of 2′,3,4′,5,7-pentahydroxyflavone (Morin) complexes of these elements onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. Optimal analytical conditions were found to be Morin concentration of 2.0 μM, pH of 4.0, and an adsorption potential at −500 mV versus Ag/AgCl. With an accumulation time of 60 s, the peak currents are proportional to the concentration of copper, lead and zinc over the 1 to 60, 0.3-80 and 1-70 ng ml⁻¹ range with detection limits of 0.06, 0.08 and 0.06 ng ml⁻¹, respectively. The procedure was applied to the simultaneous determination of copper, lead and zinc in some real and synthetic artificial real samples with satisfactory results.     

A Batch Injection Analysis System with Square-wave Voltammetric Detection for Fast and Simultaneous Determination of Zinc and Ascorbic Acid

The determination of organic and inorganic compounds in a single run is still a great challenge. In this paper, we developed a method for fast simultaneous determination of ascorbic acid (AA) and zinc ions (Zn) using batch injection analysis with detection by square-wave anodic stripping voltammetry (BIA-SWASV). Britton-Robinson (BR) buffer solution (pH=6.0) as the supporting electrolyte and boron doped diamond (BDD) as the working electrode. The method presented favorable analytical characteristics such as fast response (67 injections h⁻¹), low detection limits (0.2 and 5.4 μmol L⁻¹ for Zn ions and AA, respectively) and recovery values of 99±3%.     

Differential pulse anodic stripping voltammetric determination of ziram (a dithiocarbamate fungicide)

A d.c. polarographic technique has been used previously for the determination of the pesticide, ziram, in aqueous samples, this paper reports differential pulse anodic stripping voltammetric determination of ziram zinc in rice samples using a static mercury drop electrode. The procedure developed distinguishes inorganic zinc and ziram zinc in sodium acetate-sodium chloride media. The procedure developed is suitable for the determination of concentrations as low as 10 ppb of ziram with a precision of 2.1% for five successive determinations of 150 ppb of ziram.     

Stripping Voltammetry with Bismuth Modified Graphite‐Epoxy Composite Electrodes

The attractive performance of graphite‐epoxy composite electrodes (GECE) surface‐modified with a bismuth film (Bi‐GECE) for simultaneous and separate stripping determination of trace amounts of heavy metals (lead, cadmium and zinc) is described. Several key parameters have been optimized. Bi‐GECEi electrode shows superior accumulation properties when compared to bare GECE or even to Hg‐GECE. Bi‐GECE exhibits well‐defined, undistorted, reproducible and sharp stripping signals with RSD of 2.99%, 1.56% and 2.19% for lead, cadmium and zinc respectively. Detection limits of 23.1, 2.2 and 600 μg/L for lead, cadmium and zinc were obtained. Sharp peaks with high resolution (of neighboring signals) that permit convenient multi‐elemental measurements resulted. The applicability of the electrodes to the real samples (tap water and soil sample) was also tested and promising results with good recoveries were obtained.     

Parallel and serial dual electrode detectors for capillary electrophoresis

Application of parallel and serial dual electrode detectors for capillary electrophoresis was first described. In parallel dual electrode approach, two 100 μm-diameter Cu disks arranged side by side were used as the dual working electrode for the simultaneous determination of a mixture of carbohydrates and amino acids. In serial dual electrode approach, two working electrodes were arranged in a disk-ring manner for the simultaneous determination of both cysteine and cystine; the disk electrode was Hg/Au serving as the upstream electrode, the ring electrode was 5% CoPC carbon paste serving as the downstream electrode.     

Photometric Endpoint Detection in the Edta Titration of Zinc in the Presence of Manganese

Abstract

A method has been developed for the simultaneous determination of manganese and zinc or just zinc in the presence of manganese using a photometric technique for determination of the zinc end-point. The accuracy of the results is comparable to that obtained with conventional methods but, in most cases, there is a slight increase in precision. The endpoint is much easier to determine photometrically.     

Simultaneous determination of multicomponents by flow injection analysis: determination of copper and zinc in serum by using zincon as colouring reagent

A flow injection system is described for the simultaneous determination of copper and zinc with a single detector. Two sample plugs are injected into the same carrier stream sequentially. One is for zinc determination and the other is for the sum of copper and zinc. For zinc determination, copper masking reagent is simultaneously injected into a parallel carrier stream and merged with the sample plug by using the merging zone technique. Zincon is used as the colour reagent for the spectrophotometric determination of copper and zinc. The results for the analysis of serum by the proposed method correspond well with those obtained by an AAS method. The rate of analysis is about 45 samples/hr.     

Analytical procedure for the simultaneous voltammetric determination of toxic metals in dialysis fluids

A new analytical voltammetric procedure for the simultaneous determination of copper(II), lead(II), cadmium(II), zinc(II), chromium(VI), and manganese(II) in two kinds of dialysis fluid (peritoneal and haemodialysis fluids) is described. The voltammetric measurements were performed using, as working electrode, a stationary mercury electrode, and a platinum electrode and a Agmid R:AgClmid R:KCl ((sat.)) electrode as auxiliary and reference electrodes, respectively, employing 0.1 mol L(-1) dibasic ammonium citrate solution pH 6.9 as supporting electrolyte. For all the elements, the accuracy, expressed as relative recovery R%, was very satisfactory being in the range 94-105%, the precision, expressed as relative standard deviation s(r)%, was lower than 6%, while the limits of detection were of the order of a few units of microg L(-1). The analytical voltammetric procedure has been validated by comparison with spectroscopic (graphite furnace atomic absorption spectroscopy, GFAAS) measurements.     

多巴胺在氧化锌纳米棒嵌入石墨修饰电极上的电化学行为及测定

采用水热法制备了氧化锌纳米棒,用扫描电子显微镜、红外光谱等测试方法对其进行表征,通过嵌入式修饰方法,将制备出的氧化锌纳米棒嵌入到石墨电极中制成修饰电极。 用循环伏安法和差分脉冲伏安法研究了多巴胺在修饰电极上的伏安行为和反应机理。 结果表明,该修饰电极对多巴胺显示出良好的响应,不仅使峰电流增加,并使多巴胺的氧化峰电位负移68 mV。 该电极过程的动力学参数：电子转移数n=2,电子转移系数α=0.48。 多巴胺的脉冲峰电流与其浓度在5.0×10-7~1.0×10-4 mol/L内呈良好的线性关系,检出限为1.0×10-7 mol/L(S/N=3)。 对1.0×10-5 mol/L的多巴胺平行测定8次的相对标准偏差（RSD）为3.42%。 用本法测定了盐酸多巴胺注射液中多巴胺的含量,加标回收率为94.83%~104.5%。     

Applications of a copper microparticle-modified carbon fiber microdisk array electrode for the simultaneous determination of aminoglycoside antibiotics by capillary electrophoresis

A copper microparticle-modified carbon fiber microdisk array electrode was fabricated and employed in capillary electrophoresis for the simultaneous determination of the five aminoglycoside antibiotics (AGs) including netilmicin, tobramycin, lincomycin, kanamycin and amikacin. The array electrode exhibited high catalytic activity for AGs, good reproducibility and stability. Under the optimum separation conditions (separation voltage of 6.2 kV, electrophoretic medium of 125 mM NaOH), the five AGs above were baseline separated within 20 min. At a working electrode potential of 0.7 V (versus saturated calomel electrode), the calibration curves were linear over two orders of magnitude of concentration, and the detection limits (SIN=3) were below 2 microM except for lincomycin (6.7 microM). The developed method was successfully employed for the simultaneous determination of the five AGs studied in pharmaceutical injections. The feasibility of this method for the simultaneous determination of lincomycin, kanamycin and amikacin in urine sample was also demonstrated.     

A simple electroanalytical methodology for the simultaneous determination of dopamine,serotonin and ascorbic acid using an unmodified edge plane pyrolytic graphite electrode

A simple method using an unmodified edge plane pyrolytic graphite electrode (EPPGE) is reported for the simultaneous determination of dopamine (DA), serotonin (ST) and ascorbic acid (AA). The performance of this electrode is superior to other unmodified carbon-based electrodes and also to many modified electrodes in terms of detection limit, sensitivity and peak separation for determination of DA, ST and AA. Using this method, detection limits of 90 nM, 60 nM and 200 nM were obtained for DA, ST and AA respectively. No electrode fouling is observed during a set of experiments and good sensitivity is obtained for the simultaneous determination of DA, ST and AA. The peaks for the three species are well resolved from each other and the electrode is successfully utilised for their determination in standard and real samples.      

Simultaneous Determination of Trace Zinc and Cadmium by Anodic Stripping Voltammetry Using a Polymeric Film Nanoparticle Self‐Assembled Electrode

A promising modified electrode was fabricated by polymerization a conductive polymer film of dipicolinic acid (DPA) onto gold nanoparticle (AuNP)‐cysteine‐gold electrode (Au). The morphology of poly(DPA)‐AuNP‐Au electrode was investigated by scanning electron microscopy (SEM). This chemically modified electrode was used for electrochemical determination of cadmium and zinc in aqueous media using differential pulse anodic stripping voltammetry. The result showed that the modified electrode could clearly resolve the anodic stripping peaks of zinc and cadmium. The linear analytical curves were obtained in the ranges of 0.020–25.0 and 0.045–17.0 µM for zinc and cadmium respectively. The limit of detections (S/N=3) were 0.008 µM for zinc and 0.015 µM for cadmium.