Determination of palladium by stripping voltammetry in raw gold ores

The electroconcentration of gold(III) and palladium(II) on the electrode surface gives a binary alloy whose components are electrochemically oxidized at almost the same potential. Two methods were proposed for the separation of overlapping anodic peaks: the chemical reduction of gold(III) under UV irradiation and the use of a special computer software built into the analyzer. The results of determining palladium(II) in raw gold ore using stripping voltammetry and two proposed methods of peak separation are compared.     

Determination of gallium by adsorptive stripping voltammetry

A procedure for the determination of gallium by differential pulse adsorptive stripping voltammetry (DPADSV), using different complexing agents (ammonium pyrrolidine dithiocarbamate (APDC), pyrocatechol violet (PCV) and diethyldithiocarbamate (DDTC)), has been optimized. The selection of the experimental conditions was made using experimental design methodology. Under these conditions, the calibration was made and the detection limit was determined for each gallium-ligand complex. A robust regression method was applied which allowed the elimination of anomalous points. The detection limit, with α=β=0.05, for gallium-APDC complex was 5.0×10⁻⁸ mol dm⁻³, for gallium-PCV complex was 9.9×10⁻⁹ mol dm⁻³, and the lowest detection limit (1.3×10⁻⁹ mol dm⁻³) was obtained with DDTC. For this reason, DDTC was selected for the determination of the gallium concentration in a certificate sample and in a spiked tap water sample. The linear dynamic range for gallium-APDC complex was from 5.0×10⁻⁸ to 2.7×10⁻⁷ mol dm⁻³, for gallium-PCV complex was from 5.0×10⁻⁹ to 4.8×10⁻⁷ mol dm⁻³, and for gallium-DDTC complex was from 1.0×10⁻⁹ to 2.1×10⁻⁷ mol dm⁻³.     

Determination of trichlorobiphenyl by adsorptive stripping voltammetry

Trichlorobiphenyl is determined in the concentration range 0.004–1 mg l^?1 by adsorptive stripping voltammetry at a hanging mercury drop electrode. Preconcentration is achieved by adsorption at a potential of ?0.40 (V (vs. Ag/AgCl), and desorption at ?1.10 V. Biphenyl interferes with the determination only when present in 5-fold molar amounts compared to trichlorophenyl. The interference of DDT is eliminated by prior treatment of the sample solution with sulphuric acid. The method was applied for the analysis of waste and natural waters, the relative standard deviation being <5%.     

Determination of uranium by adsorptive stripping voltammetry

A voltammetric method for the determination of uranium in natural waters in the concentration range from 0.4 μg 1⁻¹ to 0.2 mg 1⁻¹ is described. The method is based on adsorptive accumulation of the uranium(VI)—pyrocatechol complex on the hanging mercury drop electrode followed by the reduction of the absorbed complex.     

Determination of palladium by adsorptive stripping voltammetry

 Adsorptive accumulation of the Pd(II) complex with dimethylglyoxime was evaluated for stripping voltammetry with respect to different parameters. The sensitivity of the method and the linearity between the peak current and the concentration of Pd(II) depends on the ionic strength, the electrode area, the preconcentration time, the transport rate to the electrode, and the potential scan rate. The most appropriate medium was 0.1 mol/L acetate buffer between pH 3.5 and 4. Using 2 min of preconcentration at a 2.6 mm² electrode and the differential pulse mode, a detection limit of 0.05 μg/L Pd was achieved for liquid samples and 50 ng/g for solid samples. Different aqueous and solid samples were analysed and the recovery from biological and inorganic materials investigated. Received: 29 February 1996/Revised: 29 July 1996/Accepted: 1 August 1996     

Determination of azinphos-methyl by adsorptive stripping voltammetry

A very sensitive electrochemical stripping procedure for azinphos-methyl (Guthion) is reported. Accumulation is achieved by adsorption of the compound on a hanging mercury drop electrode. The adsorptive stripping response was evaluated with respect to accumulation time and potential, concentration dependence, electrolyte and other variables. The determination limit is 0.2 ng ml^?1 after 300 s accumulation and 0.4 ng ml^?1 after 180 s accumulation. The procedure was applied to spiked river water.     

Determination of cardiac preparations by stripping voltammetry

It was shown that cardiac preparations (Enduracin, Digoxin, Cordanum, and Diltiazem) can be determined in individual solutions and biological media by stripping voltammetry. The pharmacokinetic studies of cardiac preparations were carried out in patients with cardiovascular diseases using the developed medical procedures. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.     

Determination of iron in high purity materials by adsorptive stripping voltammetry with solochrome violet

Stripping voltammetry peaks of an iron solochrome violet complex are shown to be strongly effected by anions present in the sample solution. Chloride and sulphate exhibit different dependencies of the peak height as a function of concentration. They have to be taken into account if the results of iron determinations are to be precise as well as accurate (i.e. the same as those obtained by an independent method). Graphite furnace atomic absorption spectrometry, after extraction of the acetylacetone complex, has been used here for comparison purposes.     

Determination of ruthenium as ruthenate by stripping voltammetry

Stripping voltammetric analysis of ruthenium with a platinum RDE was studied in the concentration range from 5×10^?7 to 1.2×10^?5M RuO₄^2?, where linear dependence of the anodic peak height on the ruthenate concentration was obtained. Special attention has been paid to a simple preparation of the sample for analysis. Ruthenate can be prepared directly in the electrolytic vessel from the ruthenium compounds by oxidation with potassium persulphate in alkaline medium. As a supporting electrolyte 10^?2 to 5×10^?2M K₂S₂O₈ with 10^?1 to 1 M KOH was used.     

电位溶出法测定铅和镉

重金属铅和镉元素在环境中普遍存在并可长期蓄积,是不可降解的环境污染物,常危害人体健康.建立快速准确的测定方法具有实际意义[1].     

Determination of captopril in pharmaceutical forms by stripping voltammetry

A voltammetric procedure is developed for determining captopril in pharmaceuticals. It is based on the preliminary electrochemical accumulation of the captopril oxidation product on a platinum electrode in a 0.1 M HNO₃ solution at 1.2 V versus a saturated silver-silver chloride electrode. The reduction current of the oxidation product is a linear function of captopril concentration in the range from 1.2 × 10^?6 to 3.2 × 10^?4 M. The determination limit is 9.2 × 10^?7 M. The relative standard deviation is between 1 and 4%.     

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.     

Determination of alprazolam in serum by adsorptive stripping voltammetry

The surface-active properties of alprazolam at a hanging mercury drop electrode allow their sensitive determination by differential-pulse adsorptive stripping voltammetry. Detection limits are 0.07 ng/ml for accumulation in water (accumulation time 240 s) and 0.3 ng/ml for accumulation in serum extract (accumulation time 30 s). Coefficients of variation at 5 ng/ml (10 determinations) were typically <2%.     

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 secnidazole in urine by adsorptive stripping voltammetry

Cyclic voltammetry was used to explore the adsorption behavior of secnidazole on a hanging mercury drop electrode (HMDE). The effects of various operational parameters on the accumulation behavior of the adsorbed species were tested. Thus, a sensitive stripping voltammetry procedure for the determination of secnidazole with an adsorptive accumulation on the surface of HMDE has been developed. Measurements were taken by differential-pulse voltammetry after determination of the optimum conditions. The linear concentration range was 1 x 10(-8)-1 x 10(-7) s when using a 120 s preconcentration at -0.1 V vs. Ag/AgCl in acetate buffer of pH 4.0. The detection limit of secnidazole was 5 x 10(-9) M. The precision, expressed by the coefficient of variation, was 2.5% (n = 10) at a concentration of 1 x 10(-7) m. The method was successfully applied to the analysis of secnidazole in urine.     

Determination of chitosan by cathodic stripping voltammetry.

A sensitive method for the determination of chitosan (CTS) by cathodic stripping voltammetry is presented. The method exploits a pair of oxidation-reduction peaks of CTS at -0.62 V (vs. SCE) and -0.54 V (vs. SCE), and an enhancement of the peak current of CTS observed in a 0.05 mol l(-1) potassium hydrogenphthalate buffer solution (pH 2.5). The peak current is linear with the concentration of CTS from 5.0 x 10(-7) to 1.5 x 10(-5) g ml(-1), and the detection limit is 1.0 x 10(-7) g ml(-1). We studied the characteristics and the mechanism of the electrode reaction, which proved that this process was diffusion controlled. This method was applied to determine the content of CTS in real samples with satisfactory results.     

Determination of cobalt in plant digests by adsorption stripping voltammetry

The procedure involves adsorption of cobalt onto a static mercury drop as its dimethylgloximate complex (pH 9.3, adsorption potential ?0.70 V, adsorption time 2 min), followed by a d.c. cathodic scan, effecting reduction at ?1.15 V (SCE). Of the dominant electroactive trace elements in plants (Mn, Fe, Zn), only zinc interfered; it was masked by nitrolotriacetic acid (2 × 10^?4 M). The detection limit is 0.01 μg l^?1 cobalt in the digest; the relative standard deviation is 2.5% at 0.75 μg l^?1. Calibration is linear in the range 0–6.0 μg l^?1 cobalt. Results obtained by the voltammetric method, by electrothermal atomic absorption spectrometry and neutron activation analysis are compared for seven pasture samples containing 0.1–0.2 mg kg ^?1 cobalt. The activation method provides validation for the same preparation and voltammetric results.     

Determination of thallium in natural waters by anodic stripping voltammetry

Thallium was determined in natural waters by anodic stripping voltammetry at a hanging mercury drop electrode, in acetate buffer pH 4.6+EDTA, after preconcentration and separation on an anion exhange resin. For Pacific Ocean surface waters a mean value of 13.0±1.4 ng Tl l^?1 was found, while for freshwater samples the value was 3.7±1.0 ng Tl l^?1. Thermodynamic considerations of thallium speciation predict that both in seawater and freshwater thallium exists primarily in the trivalent state. This was confirmed by experiment.     

Determination of pyrithione in natural waters by cathodic stripping voltammetry

A method was developed to determine the biocide pyrithione in natural waters. The method is based on cathodic stripping voltammetry (CSV) in the presence of Triton-X-100, which is used to separate the peak from interfering thiol compounds. Optimised conditions include a Triton-X-100 concentration of 4 ppm and a pH adjusted to 9 using ammonia buffer. The adsorption potential for pyrithione was −0.10 V and the peak occurred at −0.2 to −0.3 V. Detection was by differential-pulse CSV. The detection limit in UV-digested seawater was 1.5 nM for a deposition time of 60 s. In principle, this limit of detection could be lowered by extending the adsorption time, but in practice this may not be possible due to interferences by other organic compounds (surfactants and thiol compounds) in natural waters.