The determination of copper,lead, cadmium and zinc in human teeth by anodic stripping voltammetry

Differential pulse anodic stripping voltamrnetry and a hanging mercury drop electrode are used for the determination of copper, lead, cadmium and zinc in Norwegian teeth and pure hydroxyapatite. Special attention is given to the choice of decomposition procedure and the determination of the blank values. A complete dissolution of the tooth material and satisfactory blank values can be obtained by using decomposition with nitric acid in a Teflon bomb.     

Simultaneous determination of trace amounts of zinc, lead and copper in rum by anodic stripping voltammetry

The determination of traces of Zn, Pb and Cu in rum samples by anodic stripping voltammetry without previous treatment or addition of a supporting electrolyte, using a hanging mercury drop electrode, is described. The choice of an appropriate stripping voltammetric method and deposition potential minimizes the influence of the organic content and ensures good reproductibility of the measurements. The reliability of the method was tested by comparing the results with those given by absorption spectrometry, the differences being about 10%. The method allows heavy metal ions to be determined in the mug l(-1) concentration range.     

Interferences in the determination of copper in natural waters by anodic stripping voltammetry

Copper(I)-binding anions such as cyanide and thiocyanate, and polysaccharides, when present in non-saline waters are shown to produce an additional, more anodic wave during the determination of copper by stripping voltammetry. The origins of this wave and potential interferences in determinations of copper and copper-complexing capacities are discussed. The effect of inadequate oxygen removal is reported.     

The determination of copper in silicon by anodic stripping and differential pulse voltammetry

A critical comparison of the application of differential pulse voltammetry and anodic stripping voltammetry to the determination of micro amounts of copper in silicon is described. The anodic stripping technique offers advantages when a dropping mercury capillary with a long drop time is used. The method recommended allows the determination of copper in silicon with a precision of ± 5 %; the limit of determination is about 1μg g^-1. Calibration graphs are linear in the range 0–0.2 μg Cu ml^-1. Methods for the dissolution of silicon are also compared.     

Simultaneous determination of copper and lead in ethanol fuel by anodic stripping voltammetry

The presence of trace metals in car fuels plays an important role in the engine maintenance. In addition, these metals contribute for the environmental contamination in big cities and their control is necessary. Square Wave Stripping Voltammetry (SWSV) is a very sensitive technique for elemental trace determination and was applied for ethanol fuel analysis. The first studies were done searching for the best conditions for copper determination in alcoholic medium, utilizing gold electrodes. During these studies, the possibility of the simultaneous determination of copper and lead in the same experiment was observed. Two procedures for the analysis of these metals were adopted: The direct quantification of metals in alcohol–water mixtures and a second way that involves the evaporation of the organic solvent and re-suspension of the ions with water+electrolyte. Good recovery values were obtained for synthetic samples spiked with known amounts of metals. The results obtained for the two methods were in good agreement. The detection limits for copper and lead in 75% ethanol–water ratio solution were calculated as 120 and 235 ng l⁻¹, respectively, for 15-min deposition time.     

The determination of gold by anodic stripping voltammetry

A method is described for the routine determination of gold as its chloride or cyanide complex by anodic stripping voltammetry at a glassy carbon electrode coupled to a microprocessor-controlled voltammeter. The preferred supporting electrolyte is 0.1 M HCl/0.32 M HNO₃, with plating at ?200 mV or ?1200 mV (vs. Ag/AgCl). The stripping peak potentials range from 830 to 1150 mV (vs. Ag/AgCl) depending on concentration and plating time. Precision (percent relative standard deviation) is better than 5 % for a range of concentrations between 5 μg l^?1 and 1000 μg l^?1. The detection limit is about 5 μg l^?1 for a 5-min plating period. Interferences from Cu, Hg, Ag and other electroactive species are overcome by preliminary extraction with diethyl ether.     

Determination of zinc in sea-water by anodic stripping voltammetry

The horizontal distribution of zinc in surface waters from Guanabara Bay has been studied by use of optimized voltammetric techniques and ultraclean working procedures. The non-linearity observed between the peak current for zinc and the electrolysis time, as well as the appearance of a peak at −1.16 V, are discussed. The values found for total zinc in the samples range between 0.3 and 22 μg/l.     

Determination of copper in seawater by anodic stripping voltammetry

Copper in surface seawater has been determined using both hanging mercury drop and thin film electrodes. Total copper was found to be in the range 0.4–0.7 μg l^?1, and labile copper in the range 0.2–0.4 μg l^?1. Most of the copper present in seawater is complexed with or adsorbed on organic matter, and a smaller percentage is associated with inorganic colloids. Seawater contains both organic and inorganic compounds which will react with approximately 1×10^?8M added ionic copper. Because of the presence of the complexing agents, peak current-copper concentration calibration curves in seawater are non-linear, and care must be exercised in using spiked results in the calculation of the copper content. The thin film electrode (TFE) is more suitable than the hanging mercury drop electrode for determining copper in seawater, although the TFE results are more dependent on deposition potential, and suffer from interference by nickel if very negative deposition potentials are used.     

Trace-metal determination by second-harmonic alternating-current anodic stripping voltammetry

Second-harmonic alternating-current voltammetry can be used for the sequential determination of two electroactive species having very similar half-wave potentials (deltaE(1 2 ) < 50 mV). Since the concentrations of such metals in samples of special interest are often at trace levels, for their determination second-harmonic a.c. voltammetry (extremely selective but not sufficiently sensitive) can usefully be combined with the anodic stripping method, which has a very high analytical sensitivity. The determination of tin and lead as well as of indium and cadmium in 1M hydrochloric acid is described. The half-wave potentials are only 35 and 45 mV apart, respectively, for these systems. A three-electrode cell was used with a long-lasting sessile-drop mercury electrode as the working electrode, with a drop-time of 240-300 sec. The detection limit was found to be 10(-8)M for all four elements studied. The precision expressed as the relative standard deviation was 2-3% and the relative error was 1-2%.     

Simultaneous determination of lead, cadmium and zinc in aerosols by anodic stripping voltammetry

Summary The simultaneous determination of lead, cadmium and zinc in air particulate matter by anodic stripping voltammetry is described. Optimum conditions for the anodic stripping of lead, cadmium and zinc were determined using ammonium tartrate buffer at pH 4.5. Interferences from other metals were not encountered and the estimations were reproducible within a standard deviation of ±10%. Low blank values and high sensitivity of the method allowed the determinations at sub-ppb levels with an electrolysis time of 3–10 min. The geometric mean concentrations of lead, cadmium and zinc at various locations in Greater Bombay during 1979 are also presented.

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Simultanbestimmung von Blei, Cadmium und Zink in Aerosolen durch anodische Stripping-Voltammetrie

Zusammenfassung Die optimalen Bedingungen für die Bestimmung von Pb, Cd und Zn unter Verwendung von Ammoniumtartratpuffer pH 4,5 wurden ausgearbeitet. Störungen durch andere Metalle traten bei den untersuchten Aerosolen nicht auf. Die Standardabweichungen lagen bei ±10%. Infolge niedriger Blindwerte und hoher Empfindlichkeit konnten Bestimmungen im sub-ppb-Bereich mit Elektrolysenzeiten von 3–10 min durchgeführt werden. Ein Überblick über die Konzentration der genannten Metalle in der Luft von Bombay wird gegeben.

     

Simultaneous determination of lead,copper, cadmium and zinc in pure zirconium metal by differential-pulse anodic stripping voltammetry

Zirconium metal (ca. I g) was dissolved in hydrofluoric acid, excess of which was removed by fuming with sulphuric acid. An aliquot of this solution was treated with sodium citrate and adjusted to pH 4.5. Lead, copper and cadmium were deposited on the hanging mercury drop electrode by applying a potential of ?0.8 V vs. Ag/AgCl for 1 min and anodic stripping voltammograms were recorded; the anodic peaks appeared at ?0.51, ?0.14 and ?0.67 V, respectively. In a separate run, zinc was deposited at ?1.2 V and the stripping peak appeared at ?1.1 V. Standard additions were used to quantify these impurities at levels in the low mg kg^?1 range, with relative standard deviations of 5–11%.     

Quantitative determination of zinc in milkvetch by anodic stripping voltammetry with bismuth film electrodes

Bismuth film electrode (BiFE) was shown to be an attractive alternative to common mercury film electrode (MFE) for anodic stripping voltammetric measurements. In this study, bismuth film, that was in situ deposited onto glassy carbon electrode, was used to detect zinc content of milkvetch, used in traditional Chinese medicine. Variables affecting the response have been evaluated and optimized. Experimental results showed a high response, with a good linearity (between 0.5 × 10⁻⁶ mol L⁻¹ and 3 × 10⁻⁶ mol L⁻¹) a good precision (R.S.D. = 3.58%) and a low detection limit (9.6 × 10⁻⁹ mol L⁻¹ with a 120 s anodic). The anodic stripping performance makes the bismuth film electrode very desirable for measurements of trace nutritive element zinc in milkvetch and should impart possible restrictions on the use of mercury electrode.     

Simultaneous determination of mercury and arsenic by anodic stripping voltammetry

An electrochemical method for the simultaneous determinations of Hg^II concentration and total As^III and As^V concentration has been developed. The method does not require the additional preliminary step of the chemical reduction of As^V to As^III, or oxidation of As^III to As^V before stripping analysis takes place. Also, the method for the simultaneous determination of Hg^II concentration and As^III concentration is described. Measurements were performed in 0.1 M HCl using a gold-plated graphite electrode as sensor. Detection limits for both methods are below 0.4 ppb. Relative standard deviation did not exceed 15%. The possible interference by other trace metals was investigated. Analyses of natural water and industrial solutions were made using proposed methods and AAS. The t-test demonstrates that there was no significant difference between the results obtained with these methods. Proposed methods decrease the time of analysis because concentrations of the Hg^II and arsenic ions were measured simultaneously. Also, the removal of the additional step of chemical reduction of As^V to As^III or oxidation of As^III to As^V decreases analysis time, and also reduces the chance of contamination due to the use of additional reagents.     

Determination of copper and lead in schist by anodic stripping voltammetry

Samples were decomposed in HClO₄/HF mixture in a Teflon beaker to avoid electrochemical interference from platinum ions. The residue remaining after evaporation to dryness was taken up in nitric acid and examined by anodic stripping voltammetry. Both the hanging mercury drop electrode and the rotating glassy carbon electrode, mercury-plated in situ, were used with success. Copper at 120 ppm and lead at 40 ppm were determined with a relative standard deviation of 6%. The schist was the Nordic reference sample ASK-2.     

The determination of trace amounts of zinc, cadmium, lead and copper in airborne particulate matter by anodic stripping voltammetry

The application of anodic stripping voltammetry, with a hanging mercury drop electrode, to the determination of zinc, cadmium, lead and copper in airborne particulate matter collected by filtration is discussed. This procedure allows for the destruction of the filter material followed by the complete dissolution (including silicates) of the collected particulate matter. A low-temperature ashing process is described and the recovery of cadmium in this procedure is studied. Analytical data obtained by anodic stripping and atomic absorption for zinc, cadmium, lead and copper are compared.     

The determination of zinc,cadmium, lead and copper in a single sea-water sample by differential pulse anodic stripping voltammetry

A comparative study is described of the anodic stripping voltammetry of sea water at its natural pH and at acetate-buffered pH, with a mercury film electrode. The reproducibility of the oxidation current peaks for copper and lead is improved and the electrode memory effect decreases, when the sample is acetate-buffered (pH 5.8). Determinations of zinc at the natural pH of sea water are inaccurate, because of the formation of Zn—Cu and Zn—Ni intermetallic compounds in the mercury film. The formation of such compounds can be prevented by the addition of gallium ions to acetate-buffered samples. A procedure for the determination of Cu, Pb, Cd and Zn in sea water is described.     

Selective method for the determination of gold by anodic stripping voltammetry

A highly selective method for the deter- mination of gold by anodic stripping voltammetry is described. For preconcentration a glassy carbon electrode, activated by deposition of small amounts of gold before the measurement, is proposed. The Au³⁺ reduction process at such an electrode is effective starting with the potential +0.4 V vs. Ag/AgCl electrode. A linear dependence of the current of the gold stripping peak on the gold concentration was obtained in the range from 5×10⁻⁸ to 1×10⁻⁶ mol/l. The relative standard deviation for 2×10^-7 mol/l HAuCl₄ was 4.2% (n=5). The detection limit was 4×10^-9 mol/l. The accuracy of the method was verified by the determination of gold in reference materials.     

Selective method for the determination of gold by anodic stripping voltammetry

A highly selective method for the deter- mination of gold by anodic stripping voltammetry is described. For preconcentration a glassy carbon electrode, activated by deposition of small amounts of gold before the measurement, is proposed. The Au³⁺ reduction process at such an electrode is effective starting with the potential +0.4 V vs. Ag/AgCl electrode. A linear dependence of the current of the gold stripping peak on the gold concentration was obtained in the range from 5×10^–8 to 1×10^–6 mol/l. The relative standard deviation for 2×10^-7 mol/l HAuCl₄ was 4.2% (n=5). The detection limit was 4×10^-9 mol/l. The accuracy of the method was verified by the determination of gold in reference materials.     

The determination of silver in ores by anodic stripping voltammetry

Stripping voltammetry at a rotating glassy carbon electrode is proposed for the determination of silver in ores. The ores or concentrates are dissolved in suitable acid mixtures, and silver is separated either by extraction with dithizone in carbon tetrachloride, or by adsorption on silica from ammoniacal buffered solution and subsequent elution with 0.1 M nitric acid. The results obtained with stationary and rotating glassy carbon electrodes are discussed. Stripping voltammetry and fire assay give results in reasonably good agreement.