Determination of thallium in lead salts by differential pulse anodic-stripping voltammetry

The determination of trace levels of thallium in lead and lead salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte without surfactant, lead at concentrations below 0.5mM does not give a peak. When the electrolyte also contains tetrabutylammonium chloride (TBAC) at 0.01 M concentration, lead can be tolerated at concentrations up to 0.05M, while the height of the thallium peak is unaffected. It is thus possible to determine 5nM T1(I) in the presence of 0.05M Pb(II), i.e., Tl at the 1 x 10(-5)% level in lead. The precision of the determination (1-4%) and the recovery are satisfactory. Neither an 800-fold excess ratio of Cu(II) to Tl(I) nor a 10(7)-fold ratio of Bi(III) interferes in the determination. Thallium has been determined in a range of lead salts of various degrees of purity.     

Determination of thallium in bismuth by differential pulse anodic-stripping voltammetry without preliminary separation

The determination of trace levels of thallium in bismuth and bismuth salts by differential pulse anodic-stripping voltammetry has been made possible by using a surfactant as an electrochemical masking agent, in addition to a complexing agent. In 0.2M EDTA at pH 4.5 as supporting electrolyte in the absence of surfactant, bismuth at concentrations below 10(-4)M does not interfere. When the electrolyte also contains tetrabutylammonium ions at 0.01 M concentration, bismuth can be tolerated at concentrations up 0.05M, and the height of the thallium peak is unaffected. It is thus possible to determine 1 nM Tl(I) in the presence of 0.05M Bi(III), i.e., Tl at the 1 x 10(-6)% level in bismuth. The precision of the determination and the recovery are satisfactory. Neither an 800-fold ratio of Cu(II) nor a 10(7)-fold ratio of Pb(II) to Tl(I) interferes in the determination. Other cations such as Zn(2+), Cd(2+), In(3+), Hg(2+), Fe(3+), Sb(3+) and Sn(4+) in 10(4)-fold molar ratio to Tl(I) have no effect on the determination. Thallium has been determined in bismuth metal and in bismuth nitrate of various degrees of purity.     

Determination of dissolved manganese in natural waters by differential pulse cathodic stripping voltammetry

A procedure based on differential pulse cathodic stripping voltammetry on the graphite electrode is described for the determination of dissolved manganese in natural waters buffered at pH about 6.5 with acetate solution. In order to avoid interference of iron(II) the addition of fluoride is used. The limit of detection is 3 g/l for a deposition time of 6 min. Acidification and UV-irradiation are recommended for samples containing dissolved organic matter. Results of manganese determination in table mineral waters are reported and the possibility of manganese speciation is discussed.     

Determination of cadmium by differentialn pulse anodic-stripping voltammetry after salting-out extraction into acetonitrile

A selective and specific method is presented for anodic-stripping voltammetric determination of cadmium after extraction with 0.1Mtetrabutylammonium iodide solution in acetonitrile from aqueous ammonium sulphate solutions. The detection limit of this method is 0.2 ng ml (in the acetonitrile extract). Interference from matrices or large amounts of elements reduced at more positive potentials can be eliminated by prior extraction. The method has been applied to trace analysis for cadmium in zinc, lead and indium metals, and some inorganic salts.     

Investigation by automated differential pulse anodic-stripping voltammetry of the problem of storage of dilute solutions

The storage of dilute solutions of metal ions before their laboratory analysis presents a difficult problem in the examination of many environmental samples. By utilizing the solution container as an electrochemical cell and employing the method of differential pulse anodic-stripping voltammetry at a hanging mercury drop electrode, it is shown that an automated read-out system in an enclosed environment can be developed for monitoring the solution-container interactions that occur over short or extended periods of time. In the present work, interactions of dilute solutions (1-10 mug/l.) of cadmium(II), lead(II), copper(II), zinc(II), and thallium(I) in glass, polyethylene and Teflon containers have been investigated at various pH values and in different ionic environments. The results demonstrate the importance of factors other than pH.     

Determination of arsenic in gold samples using matrix exchange differential pulse stripping voltammetry

A method comprising matrix exchange differential pulse stripping voltammetry (DPSV) at a gold film electrode has been proposed for the determination of small quantities of arsenic in pure gold. A wall-jet cell (WJC) and an on-line deoxygenation system were used to facilitate matrix exchange. The gold(I) cyanide complex was formed to avoid gold deposition on the electrode together with the arsenic. The pH of the sample solutions were adjusted to 3, as alkaline solutions gold(I) cyanide produced interference and the uncomplexed cyanide led to passivation of the gold film electrode. Matrix exchange electrolytes consisting of 4 mol l⁻¹ hydrochloric acid or a combination of 2 mol l⁻¹ sulphuric acid and 0.2 mol l⁻¹ hydrochloric acid could be utilised. Arsenic concentrations as low as 0.1 mg l⁻¹, could readily be detected in a gold matrix with a 60 s deposition time. While, cobalt and silver did not interfere with the arsenic determination, copper interfered even when present at similar concentrations to that of arsenic.     

Determination of ascorbic acid by differential pulse voltammetry

Summary A new approach to the determination of ascorbic acid has been realized with differential pulse voltammetry (DPV) on the carbon paste electrode (CPE). The problems of the reproducibility of the surface of this electrode have been resolved by using always the same surface after its conditioning. The developed method has been applied to the direct determination of vitamin C in pharmaceutical tablets and in different types of fruit juices. Limits of determination are 1.5 ×10^–7 M, 8×10^–7 M and 1×10^–5 M for tablets, dehydrated and liquid juices, respectively.

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Bestimmung von Ascorbinsäure durch Differential-Puls-Voltammetrie

Zusammenfassung Als neues Verfahren zur Ascorbinsäurebestimmung wird die Differential-Puls-Voltammetrie mit Hilfe der Kohlepasteelektrode vorgestellt. Das Problem der Reproduzierbarkeit der Elektrodenoberfläche wurde dadurch gelöst, daß nach Konditionierung immer dieselbe Oberfläche verwendet wurde. Das Verfahren wurde zur Analyse von pharmazeutischen Tabletten und Fruchtsäften angewendet. Die Bestimmungsgrenzen liegen bei 1,5·10^–7 M, 8·10^–7 M und 1·10^–5 M für Tabletten, dehydratisierte bzw. flüssige Säfte.

     

微分脉冲阴极溶出伏安法测定呋喃唑酮

研究了呋喃唑酮在玻碳电极上的伏安行为。在 1mol LHCl底液中 ,用微分脉冲阴极溶出伏安法得到一灵敏的呋喃唑酮还原峰 ,峰电位为 0 .0 38V(vs.Ag AgCl)。峰电流与呋喃唑酮浓度在 8× 1 0 -6～ 1× 1 0 -4 mol L范围内呈线性关系 (r=0 .9984) ,检出限为 8× 1 0 -8mol L。该法已用于片剂与合成血清样品中呋喃唑酮含量的测定     

Determination of thallium at subtrace level in rocks and minerals by coupling differential pulse anodic-stripping voltammetry with suitable enrichment methods

Ten international reference samples have been analysed for thallium content by differential pulse anodic-stripping voltammetry. Two separation techniques, solvent extraction and ion-exchange, were employed to preconcentrate the thallium: the results were critically compared to establish which was the better separation technique. The values found were quite satisfactory and confirmed the wide scope for application (not yet fully investigated) of voltammetry in geochemical studies.     

Determination of cobalt by catalytic-adsorptive differential pulse voltammetry

A novel method is described for the determination of cobalt(II) by differential pulse voltammetry, based on accumulation of a cobalt complex, [CoSCNNO]⁺, on a hanging mercury drop electrode, followed by measurement of the catalytic current of the adsorbed complex. The effects of various experimental parameters on the catalytic current were investigated. The current was found to be linear for 0.3 nM to 100 nM Co, with a detection limit of 70 pM (4.1 ng l⁻¹) and a relative standard deviation of 1.6% for 50 nM Co (n = 25). The developed method showed considerable selectivity against nickel and zinc. A possible mechanism of the reduction process is proposed.     

Evaluation of differential pulse anodic-stripping voltammetry at a stationary mercury-film electrode with stirred solution

Differential pulse anodic-stripping voltammetry at a stationary mercury-film electrode with the solution stirred during the deposition step has been investigated. The sensitivity achieved by using such a simple set-up is similar to that obtained with a mercury-film rotating disk electrode. The effects of various experimental parameters on the peak current are described. Lead and cadmium were used as test systems, and gave detection limits of around 1 x 10(-10)M with 5-min deposition times.     

微分脉冲阴极溶出伏安法测定阿米卡星

硫酸阿米卡星(Am ikacin sulfate)是一种氨基糖苷酸类抗生素,化学名为O-3氨基-3-脱氧-а-D-蒲吡喃糖基-(1-6)-O-[6-氨基-6-脱氧-а-D-蒲吡喃糖基-(1-4)]-N-(4-氨基-2-羟基-1-氧丁基)-2-脱氧?D-链霉胺硫酸盐。目前报道的测定方法主要有高效液相法[1]、镍毛细管电泳法[2]。本文研究了阿米卡星在玻碳电极上的电化学行为。微分脉冲溶出伏安法是一种灵敏度很高的痕量分析方法,本文利用该方法对阿米卡星进行了测定,发现阿米卡星在pH=2的盐酸底液中,产生一灵敏的还原峰,可用于定量测定。平行测定了7次,RSD为2·05%,该方法可用于注射液及血清中…     

Determination of palladium in deoxo catalysts by differential pulse voltammetry

A differential pulse voltammetric (DPV) method is proposed for the determination of palladium in deoxo catalysts, which are used in recombination units of the cover gas system of nuclear reactors. The electrode system consists of hanging mercury drop electrode (HMDE)/ platinum auxillary/ Ag-AgCl reference electrode. The supporting electrolyte consists of 0.02 M diammonium tartrate + 0.08 M ammonia-ammonium chloride buffer at pH 9.0. Fe, Cu, Pb, Ni, Co and Zn did not interfere. The interference by Cd could be eliminated using 0.005 M EDTA. The relative standard deviation of the proposed method was about 4.0% at ∼ 0.5% palladium content in the catalyst. The method is simple, rapid and free from any possible interferences. Received: 8 December 1998 / Revised: 11 January 1999 / Accepted: 18 January 1999     

Determination of palladium in deoxo catalysts by differential pulse voltammetry

A differential pulse voltammetric (DPV) method is proposed for the determination of palladium in deoxo catalysts, which are used in recombination units of the cover gas system of nuclear reactors. The electrode system consists of hanging mercury drop electrode (HMDE)/ platinum auxillary/ Ag-AgCl reference electrode. The supporting electrolyte consists of 0.02 M diammonium tartrate + 0.08 M ammonia-ammonium chloride buffer at pH 9.0. Fe, Cu, Pb, Ni, Co and Zn did not interfere. The interference by Cd could be eliminated using 0.005 M EDTA. The relative standard deviation of the proposed method was about 4.0% at ～ 0.5% palladium content in the catalyst. The method is simple, rapid and free from any possible interferences.     

Determination of gallium traces by differential pulse anodic stripping voltammetry

Summary The determination of gallium traces is carried out on the hanging drop mercury electrode in solutions of low ionic strength and in absence of complexing agents. At pH=3.2, where stable solutions are obtained, concentrations of 0.2 g Ga l^–1 are determinated with a standard deviation of 0.96% and a detection limit of 4 ng Ga l^–1.The effect of various instrumental parameters is investigated and optimized conditions established. The theory of differential pulse anodic stripping voltammetry is verified with the results obtained experimentally. The use of salicylate as base electrolyte is also considered.

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Bestimmung von Galliumspuren durch Differentialpuls-Anodic Stripping-Voltammetrie

     

Determination of palladium in synthetic nuclear wastes by differential pulse voltammetry

A novel method for the determination of palladium in synthetic nuclear waste samples has been developed using a computerized voltammetric analyzer. The electrode system consists of hanging mercury drop electrode (HMDE)/glassy carbon/Ag-AgCl electrode. Various experimental conditions including electrolyte type, pH and concentration have been optimized, leading to a detection limit of 40 ng/ml. The mixture of 4^.10^-3M citric acid + 2^.10^-2M ammonia-ammonium chloride buffer + 4^.10^-3M EDTA was used as a supporting electrolyte at pH 9.0. Standard addition method was employed to determine the concentration of palladium present in the nuclear waste sample. The relative standard deviation of the proposed method was found to be 8% at 40 ng/ml of palladium content. The method is direct, simple, rapid and free from any possible interference.     

Determination of bromadiolone in pheasants and foxes by differential pulse voltammetry

Bromadiolone, a commercially used anticoagulant rodenticide, was determined in tissues of various animals by differential pulse voltammetry with a carbon-paste electrode. Under the most suitable experimental conditions (step potential of 25?mV?s^?1 and 0.2?mol?L^?1 acetate buffer, pH 4.2), the limit of detection was 0.5?ng?mL^?1. The electroanalytical method was consequently used to investigate the bromadiolone transport within the food chain. Pheasants were exposed to bromadiolone and then used as feed for a fox. The average levels were 528 and 198?ng of bromadiolone per gram of fresh weight of liver of pheasant and fox, respectively. Due to the surprisingly lower content of bromadiolone in the latter, a basic biochemical analysis, particularly blood coagulation, was performed. Among the parameters studied (thrombin time, prothrombin time, activated partial thromboplastin time, and fibrinogen), there was prolongation of the prothrombin time and activated partial thromboplastin time.     

胆红素的伏安特性及其微分脉冲伏安法测定

建立中成药中胆红素定量测定的微分脉冲伏安法。在多种介质中研究胆红素在玻碳电极上的电化学行为 ,全面优化条件后 ,采用标准加入法对中成药中胆红素进行测定 ,并通过与药典中标准方法对照和干扰实验及回收率实验对本方法进行评价。在 0 .2mol·L-1HAc NaAc 5 0 %EtOH和 1 1 5mol·L-1KH2 PO4 Na2 HPO4 溶液中 ,峰电流与胆红素浓度分别在 6.2 5× 1 0 -7～ 1 .0 0× 1 0 -5mol·L-1(r=0 .9976)和 5 .0 0× 1 0 -8～ 3.0 0× 1 0 -6mol·L-1(r=0 .9939)范围内呈良好的线性关系 ,检测下限分别为 5 .0× 1 0 -8mol·L-1和 5 .0× 1 0 -9mol·L-1。众生丸和牛黄解毒片中胆红素的质量分数分别为 0 .0 86%和 0 .1 0 9% ,RSD分别为 3 4%和 3.0 % ,回收率为 96.6%～ 1 0 4 .1 % ,其结果与药典中标准方法测定结果基本一致。     

Indirect trace determination of NTA in natural waters by differential pulse anodic stripping voltammetry

Summary Bismuth(III) is added to the water sample in excess to NTA and EDTA to form inert stable complexes with them at pH 2. The uncomplexed Bi(III) is then deposited into a hanging mercury drop electrode at a potential of –0.15 V vs. SCE and subsequently stripped anodically in the differential pulse mode. The peak current of uncomplexed Bi(III) is recorded. By a second deposition at –0.35 V vs. SCE Bi(III) from Bi³⁺ and Bi-NTA is deposited. The concentrations of NTA and EDTA in the sample are determined from the concentration of added Bi(III) and the voltammetrically determined Bi(III) at these two potentials by the standard addition method. Cd, Cu, Pb, and Zn do not interfere. Fe(III) has to be reduced by ascorbic acid or hydroxylamine before the determination. Cu(II) in concentrations larger than 40 g/l has to be removed by preelectrolysis. In samples with chloride contents above 0.05 M the stripping step has to be performed after medium exchange to a perchloric acid solution of pH 2. For a deposition time of 2 min the determination limit is approximately 0.2 g/l NTA and 0.1 g/l EDTA. The relative standard deviation for NTA concentrations at 2 or 10 g/l lies at 10 or 1.3%, respectively. Good accuracy is established by finding within 2% the levels adjusted when water samples are spiked with a standard solutions of NTA or EDTA.

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Indirekte Spurenbestimmung von NTA in natürlichen Wässern durch differentielle Pulsinversvoltammetrie

Zusammenfassung Bismuth(III) wird zur Wasserprobe in Überschuß zur NTA- und EDTA-Konzentration bei pH 2 zugegeben, wobei stabile inerte Komplexe gebildet werden. Nicht komplexiertes Bi(III) wird an der hängenden Quecksilbertropfenelektrode beim Potential –0,15 V (SKE) kathodisch als Amalgam abgeschieden und dann anodisch wieder gelöst. Dabei wird im differentiellen Pulsmodus der Bi(III)-peak registriert. Durch die zweite kathodische Abscheidung beim Potential –0,35 V (SKE) wird Bi(III) aus unkomplexiertem Bi³⁺ und dem BiNTA-Komplex abgeschieden. Die Konzentrationen von NTA und EDTA in der Probe werden aus den voltammetrisch bestimmten Bi(III)-Konzentrationen bei den zwei angegebenen Potentialen und der zugegebenen Konzentration von Bi(III) mit der Standard-Additions-Methode bestimmt. Die Spurenmetalle Cd, Cu, Pb und Zn stören die Bestimmung nicht. Fe(III) muß vor der Bestimmung mit Ascorbinsäure reduziert werden, Cu in der Konzentration von mehr als 40 g/l muß durch Vorelektrolyse entfernt werden. Wenn die Probe mehr als 0.05 M Chlorid enthält, muß der Strippingvorgang nach Elektrolytwechsel in einer Perchlorsäurelösung bei pH 2 durchgeführt werden. Für eine Anreicherungszeit von 2 min liegt die Bestimmungsgrenze bei 0,2 g/l NTA und 0,1 g/l EDTA. Die relative Standardabweichung beträgt bei einer Konzentration von 2, bzw. 10 g/l NTA 10 bzw. 1,3%. Die Richtigkeit ist gut, was aus der Wiederfindungsrate von 2% der zur Probe zugegebenen Lösung des NTA- oder EDTA-Standards hervorgeht.

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Dedicated to Prof. Dr. W. Fresenius on the occasion of his 70th birthday

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On leave from the University of Thessaloniki, Greece     

Additive differential pulse voltammetry,instead of double differential pulse voltammetry

A new electrochemical double pulse potential technique called additive differential pulse voltammetry (ADPV) is proposed. This technique is inspired by the original idea of Birke et al. [Anal. Chem. 53 (1981) 852] of recording two differential pulse (DP) voltammograms and it consists of plotting the sum of these two signals versus the first pulse potential, although in this paper the proposal is to obtain the ADPV signal through just one experiment. ADPV behaves in an identical way to the triple-pulse technique double differential pulse voltammetry (DDPV) for reversible processes when diffusion coefficients are equal for spherical electrodes and for any value of diffusion coefficients in planar electrodes. In the case of reversible electrode processes with amalgamation of reaction product or other more complex processes, ADPV is more advantageous than DDPV. This is due, among other reasons, to the fact that, under these conditions, a double potential step is much simpler to analyse than a triple potential step.