Anodic stripping voltammetric determination of Zn, Pb and Cu traces in whisky samples

The simultaneous “in natura” determination of trace Zn, Pb and Cu in whisky samples by anodic stripping voltammetry (ASV), using a hanging mercury drop electrode, without previous treatment or addition of supporting electrolyte is described. The choice of an appropriate stripping voltammetric method and deposition potential minimizes the influence of the organic content and ensures a good reproducibility of the measurements. The reliability of the method was tested comparing the results with those of atomic absorption spectroscopy (AAS), with differences of about 10%. The method allows the determination of heavy metal ions in the μg L^–1 range.     

Anodic stripping voltammetric determination of antimony in gunshot residue

Anodic stripping voltammetry (a.s.v.) ata mercury film on a glassy carbon working electrode was utilized to determine the amount of antimony from hand swabs. The procedure described is useful for determining 10–120 ng of antimony found in the residue ou the hands of an individual suspected of discharging or handling a firearm. The voltammogram provides an elemental pattern recognizable as gunshot residue containing small amounts of antimony and much larger amounts of copper and lead. The amount of antimony in a variety of gunshot-residue samples was determined by both anodic stripping voltammetry and graphite-furnace atomic absorptiou spectrometry for comparison purposes. Anodic stripping voltammetry is excellent for observation of the multielement pattern which proves to be very useful for gunshot-residue samples.     

Anodic stripping voltammetric determination of lead and cadmium in soil extracts

Two single-step extraction procedures validated by BCR, extraction with 0.43 mol dm⁻³ acetic acid and 0.05 mol dm⁻³ EDTA, are used for assessing bioavailable species of Pb and Cd in soils. After an extensive study of interferences of humic substances and using standard additions procedures, the extractable contents of Pb and Cd have been determined by DPASV directly in soil extracts with a good reproducibility (RSD varied from 1.0 to 7.9 %). Pb(II) and Cd(II) were released from complex in EDTA extracts by pH adjustment to 1 with 1 mol dm⁻³ HCl. The results were compared with those obtained with atomic absorption spectrometry and indicated reasonable agreement of both methods. Exchangeable forms represented 0.2 to 3.3 % and 13.0 to 63.6 % of total content of Pb and Cd in soils, respectively. EDTA extraction released from soils 7.9 to 29.9 % and 33.5 to 59.6 % of total content of Pb and Cd, respectively.     

Decomposition of vegetables for determination of Zn,Cd, Pb and Cu by stripping voltammetry

A simple and accurate digestion method using nitric acid, perchloric acid and hydrogen peroxide has been developed for use in trace analysis for heavy metals in vegetables by differential pulse anodic stripping voltammetry. The recovery of the metals from the samples is lower if the hydrogen peroxide is omitted from the digestion mixture. Standard reference materials have been analysed satisfactorily by this method.     

Anodic stripping voltammetric determination of vardenafil hydrochloride at pencil graphite electrode

In this paper, we present a very popular and low-cost sensor material as disposable pencil graphite electrode (PGE) system for the trace-level determination of vardenafil hydrochloride (VRL). Electrochemical behavior and determination of VRL was carried out by cyclic and square-wave adsorptive anodic stripping (SW-AdAS) voltammetry. The proposed method was highly sensitive and had a linear calibration range from 3 × 10^?10 to 1 × 10^?7 M with a correlation coefficient of 0.997. The limit of detection and limit of quantitation values were calculated as 1 × 10^?10 and 3 × 10^?10 M, respectively. Developed method with disposable PGE shows high sensitivity, selectivity and stability in a wide concentration range for VRL determination without the necessity of any modification. Additionally, this system was successfully applied in Levitra^® tablets and spiked human serum in trace level of VRL. Some kinetic parameters of VRL’s were represented for the first time. The results showed that the proposed method is highly sensitive, easy and low cost for trace-level determination of VRL.     

Anodic stripping voltammetric determination of heavy metals in solutions containing humic acids

Summary Various simultaneous effects of humic acids on the current and potential of differential pulse anodic stripping peaks of copper, lead, cadmium and zinc in weakly alkaline and acidic (pH 2) solutions have been investigated and interpreted with regard to metal complexation and the adsorption of humic acid on the mercury electrode. The applicability of the standard additions method for metal quantitation and the experimental conditions for UV-photolysis with a high-pressure mercury lamp have been examined in model as well as real water samples.     

Simultaneous square wave anodic stripping voltammetric determination of Cr, Pb, Sn, Sb, Cu, Zn in presence of reciprocal interference: application to meal matrices

An analytical procedure for simultaneously determining chromium(VI), lead(II), tin(II), antimony(III), copper(II) and zinc(II) by square wave anodic stripping voltammetry (SWASV) in matrices involved in foods and food chain as wholemeal, wheat and maize meal is described.The digestion of each matrix was carried out using a concentrated HCl–HNO₃–H₂SO₄ acidic attack mixture. Dibasic ammonium citrate buffer solution pH 6.5 was employed as the supporting electrolyte. The voltammetric measurements were carried out using, as working electrode, a stationary hanging mercury drop electrode (HMDE) and a platinum electrode and an AgAgClKCl_sat electrode as auxiliary and reference electrodes, respectively. The analytical procedure was verified by the analysis of the standard reference materials Wholemeal BCR-CRM 189, Wheat Flour NIST-SRM 1567a and Rice Flour NIST-SRM 1568a.For all the elements in the certified matrix, the precision as repeatability, expressed as relative standard deviation (s_r) was of the order of 3–5%. The accuracy, expressed as relative error (e) was generally of the order of 3–6%, while the detection limits were lower than 0.123 μg/g.In the presence of reciprocal interference, the standard addition method considerably improved the resolution of the voltammetric technique.Once set up on the standard reference materials, the analytical procedure was transferred and applied to commercial meals sampled on market for sale. A critical comparison with spectroscopic measurements is also discussed.     

Determination of traces of Zn, Cd, Pb and Cu in white sugar by anodic stripping voltammetry and a modified oxygen-flask combustion technique

Anodic stripping voltammetry with a hanging-drop mercury electrode is used for determination of traces of Zn, Cd, Pb and Cu in white sugar. The sample (1.5 g) is decomposed by ignition in oxygen in a specially modified system.     

Anodic stripping voltammetric determination of total lead, copper and selenium in whole blood and blood serum

A two-step procedure including appropriate wet-digestions, separation of selenium from interfering ions such as heavy metal ions with pentyl alcohol and anodic stripping voltammetric (ASV) determination of Pb²⁺, Cu²⁺ and SeO₃ ^2– is developed. The elements in digested whole blood and serum sample solutions were determined by using a standard addition method. 1 × 10^–9 mol/L SeO^2– ₃, Cu²⁺ and Pb²⁺ were successfully determined with relative standard deviations of approximately 1–2% (n = 6–8). Received: 19 August 1996 / Revised: 24 February 1997 / Accepted: 28 February 1997     

Trace determination of Cd, Cu, Pb and Zn in annual growth rings by differential pulse anodic stripping voltammetry

Summary A new voltammetric procedure has been developed for the determination of toxic heavy metals in annual growth rings. The method is based on a wet digestion of minute quantities of wood material of 10–25 mg with an acid mixture of HNO₃ and HClO₄ in a quartz cup and the subsequent simultaneous determination of Cd, Pb, Cu and Zn by differential pulse anodic stripping voltammetry (DPASV) at the hanging mercury drop electrode (HMDE). The accuracy of the method has been proved by using electrothermal atomic absorption spectrometry as an independent procedure. The problems of the contamination by ubiquitous heavy metals during the wet digestion were investigated and their influence on the results was effectively diminished. Losses of the studied metals have not been observed. The high sensitivity of the method enables the determination of the toxic metals Pb and Cd in the analyte of the wet digestion with a relative standard deviation of less than 20% in the low level range 0.1–4 g/l.The potentialities of the method have been shown in the determination of Cd, Pb, Cu and Zn in cores of oak (Quercus petraea) from Königstein (Taunus, FRG). The high sensitivity made it possible to analyze individual growth rings and thus to avoid damages on trees using an excessive quantity of material. In two samples taken as example a distinct increase of the concentration of Cd and Pb during the last decade indicates metal pollution of the region by atmospheric precipitates.

---

Spurenbestimmung von Cd, Cu, Pb und Zn in Jahresringen mit Hilfe der Differentialpuls-ASV

---

Attached from the Institute of Chemistry, Universidad del Norte, Antofagasta, Chile. Taken in part from the Ph.D. Thesis, University in Bonn     

Anodic stripping voltammetric determination of mercury by use of a sodium montmorillonite-modified carbon-paste electrode

A sodium montmorillonite (SWy-2)-modified carbon-paste electrode has been examined for determination of trace levels of mercury. Because of its strong cation-exchange and adsorptive characteristics, SWy-2 greatly improves the sensitivity of determination of Hg(2+). Hg(2+) is preconcentrated and reduced on the modified electrode surface at -0.40 V and then stripped from the electrode surface during the positive potential sweep. The conditions used for determination, e.g. supporting electrolyte, pH, amount of SWy-2, accumulation potential, and accumulation time, were optimized. The peak current was linearly dependent on the concentration of mercury from 1 x 10(-9) to 5 x 10(-7) mol L(-1). The detection limit (signal-to-noise ratio=3) was 1 x 10(-10) mol L(-1) after accumulation for 6 min. When the SWy-2-modified carbon-paste electrode was used to detect mercury in water samples the average recovery was 101.11%.     

Anodic stripping voltammetric determination of thallium as [TlBr4]-rhodamine B complex

The anodic stripping voltammetric behaviour of the [TlBr₄]-rhodamine B complex is described and compared with that of thallium(I) and thallium(III) ions. The electrolyte composition, the best potential for the deposition of thallium from the complex in the selected electrolyte, the duration of the electrolysis, and the possibility of reduction of thallium in the [TlBr₄]-rhodamine B complex before the electrolysis with ascorbic acid were investigated. The results showed good reproducibility of the measurements of thallium as [TlBr₄]-rhodamine B complex and are similar to those obtained for thallium as Tl(I) and Tl(III) ions. As the [TlBr₄]-rhodamine B complex is strongly adsorbed on polyethylene, a previous preconcentration step on a column, packed with polyethylene powder, allowed the voltammetric determination of thallium as [TlBr₄]-rhodamine B complex in samples of KCl and NaCl as solid salts after the separation of the matrix. With this procedure it was possible to reach enrichment factors of 25 with recoveries from 96.7 to 107.9% for thallium concentrations from 5 to 40 μg L^–1 and RSD between 4.2 and 9.2%. The procedure was used to determine thallium traces in KCl and in sea salt. The results of these determinations were compared with the results obtained by graphite furnace atomic absorption spectrometry. Received: 5 February 1998 / Revised: 19 May 1998 / Accepted: 29 May 1998     

Anodic stripping voltammetric determination of thallium as [TlBr4]-rhodamine B complex

The anodic stripping voltammetric behaviour of the [TlBr₄]-rhodamine B complex is described and compared with that of thallium(I) and thallium(III) ions. The electrolyte composition, the best potential for the deposition of thallium from the complex in the selected electrolyte, the duration of the electrolysis, and the possibility of reduction of thallium in the [TlBr₄]-rhodamine B complex before the electrolysis with ascorbic acid were investigated. The results showed good reproducibility of the measurements of thallium as [TlBr₄]-rhodamine B complex and are similar to those obtained for thallium as Tl(I) and Tl(III) ions. As the [TlBr₄]-rhodamine B complex is strongly adsorbed on polyethylene, a previous preconcentration step on a column, packed with polyethylene powder, allowed the voltammetric determination of thallium as [TlBr₄]-rhodamine B complex in samples of KCl and NaCl as solid salts after the separation of the matrix. With this procedure it was possible to reach enrichment factors of 25 with recoveries from 96.7 to 107.9% for thallium concentrations from 5 to 40 μg L^–1 and RSD between 4.2 and 9.2%. The procedure was used to determine thallium traces in KCl and in sea salt. The results of these determinations were compared with the results obtained by graphite furnace atomic absorption spectrometry.     

Anodic stripping voltammetric determination of trace lead with a nafion/crown-ether film electrode

An electrode for the anodic stripping voltammetric determination of trace lead has been made by coating glassy carbon with a film of Naflon in which a crown ether is incorporated. The sensitivity is increased because of continuous transfer of lead from solution to the electrode surface by complexation with the crown ether and reduction during the deposition period. A detection limit of 5 x 10(-10)M has been obtained by electrodeposition for 3 min. The method is sensitive, simple and relatively rapid, with a relative standard deviation of 8% at the 2 x 10(-9)M level.     

Simultaneous determination of the toxic trace metals Cd, Cu, Pb and Zn in soils by differential pulse anodic stripping voltammetry

Summary A convenient and accurate analytical procedure has been developed for the simultaneous determination of the toxic trace metals Cd, Cu, Pb and Zn in soils. The method is based on differential pulse anodic stripping voltammetry at the hanging mercury drop electrode in the analyte resulting from the digested soil. Pressurized wet digestion of the finely powdered soil in a mixture of HNO₃-HCl optionally followed by UV irradiation of the analyte to decompose dissolved organic matter, was used to prepare the analyte for the voltammetric analysis. The applicability of the method was proved by the analysis of 12 soil samples from various polluted and unpolluted regions. The accuracy was verified with the standard soil material SO-6 from JRC, Ispra, and by the parallel analysis of 8 different soil samples with the described procedure and with the relevant modes of atomic absorption spectrometry as an independent determination method.

---

Simultanbestimmung der toxischen Spurenmetalle Cd, Cu, Pb und Zn in Böden mit Hilfe der differentiellen Pulsinversvoltammetrie

Zusammenfassung Ein zuverlässiges und leicht durchführbares Analysenverfahren zur Simultanbestimmung der toxischen Spurenmetalle Cd, Cu, Pb und Zn in Böden wird vorgestellt. Die Bestimmungsmethode ist die differentielle Pulsinversvoltammetrie an der hängenden Quecksilbertropfenelektrode im Analyten, der aus dem Aufschluß der Bodenprobe resultiert. Die fein pulverisierte Bodenprobe wird einem Druckaufschluß mit HNO₃-HCl-Gemisch unterworfen. Gegebenenfalls wird der resultierende Analyt mit UVLicht bestrahlt zur photolytischen Zersetzung noch vorhandener gelöster organischer Substanzen. Die breite Anwendbarkeit des Verfahrens wird durch die Analyse von 12 Bodenproben aus verschiedenen belasteten und unbelasteten Regionen demonstriert. Zur Richtigkeitssicherung wurden der Bodenstandard SO-6 von JRC, Ispra, untersucht und acht verschiedene Bodenproben einer Parallelbestimmung mit der differentiellen Pulsinversvoltammetrie und mit entsprechenden Moden der Atomabsorptionsspektrophotometrie unterzogen.

     

Adsorptive stripping voltammetric determination of antimony

A new method is described for the determination of antimony based on the cathodic adsorptive stripping of Sb(III) complexed with 2′,3,4′,5,7-pentahydroxyflavone(morin) at a static mercury drop electrode (SMDE). The reduction current of the adsorbed antimony complex was measured by 1.5th-order derivative linear-sweep adsorption voltammetry. The peak potential is at −0.51 V (vs. SCE). The effects of various parameters on the response are discussed. The optimized analytical conditions were found to be: supporting electrolyte, chloroacetic acid (0.04 mol/l, pH 2.3); concentration of morin, 5×10⁻⁶ mol/l; accumulation potential, −0.25 V (vs. SCE); scan rate, 100 mV/s. The limit of detection and the linear range were 7×10⁻¹⁰ mol/l and 1.0×10⁻⁹3.0×10⁻⁷ mol/l Sb(III) for a 2-min accumulation time, respectively. This method has been applied to the determination of Sb(III) in steel and brass samples and satisfactory results were obtained. The adsorptive voltammetric characteristics and composition of the Sb(III)–morin complex were studied.     

Adsorptive stripping voltammetric determination of ofloxacin

The fluoroquinolone antibacterial agent ofloxacin was studied by adsorptive stripping voltammetry. Controlled interfecial accumulation of ofloxacin on a static mercury drop electrode in the hanging mercury drop mode provides high sensitivity. The linear concentration range was 0.079–197.5 μg ml^?1 when using a 60-s preconcentration at ?1 V vs. Ag/AgCl in Britton-Robinson buffer of pH 6.00. The detection limit of ofloxacin was 1 ng ml^?1. The precision is excellent with a relative standard deviation of ca. 0.75% at a concentration of 0.848 μg ml^?1.     

Anodic stripping voltammetric determination of mercury using multi-walled carbon nanotubes film coated glassy carbon electrode

An electrochemical method for the determination of trace levels of mercury based on a multi-walled carbon nanotubes (MWNT) film coated glassy carbon electrode (GCE) is described. In 0.1 mol L^–1 HCl solution containing 0.02 mol L^–1 KI, Hg²⁺ was firstly preconcentrated at the MWNT film and then reduced at –0.60 V. During the anodic potential sweep, reduced mercury was oxidized, and then a sensitive and well-defined stripping peak at about –0.20 V appeared. Under identical conditions, a MWNT film coated GCE greatly enhances the stripping peak current of mercury in contrast to a bare GCE. Low concentrations of I^– remarkably improve the determining sensitivity, since this increases the accumulation efficiency of Hg²⁺ at the MWNT film coated GCE. The stripping peak current is proportional to the concentration of Hg²⁺ over the range 8×10^–10–5×10^–7 mol L^–1. The lowest detectable concentration of Hg²⁺ is 2×10^–10 mol L^–1 at 5 min accumulation. The relative standard deviation (RSD) at 1×10^–8 mol L^–1 Hg²⁺ was about 6% (n=10). By using this proposed method, Hg²⁺ in some water samples was determined, and the results were compared with those obtained by atomic absorption spectrometry (AAS). The two results are similar, suggesting that the MWNT-film coated GCE has great potential in practical analysis.     

Anodic stripping voltammetric determination of bismuth(III) using a Tosflex-coated mercury film electrode

A Tosflex-mercury film electrode (TMFE) was prepared by spin-coating a solution of the perfluorinated anion exchange polymer Tosflex onto a glassy carbon electrode surface followed by electrodeposition of mercury film on this electrode. This electrode was used for the determination of trace bismuth(III) which was preconcentrated onto the TMFE as anionic bismuth(III) complexes with chloride in a chloride medium. The preconcentration was carried out at a potential of-0.2 V, and the preconcentration of the bismuth(III) was enhanced significantly by the anion-exchange feature of Tosflex. The accumulated bismuth(III) was then determined by anodic square-wave stripping voltammetry (SWSV). Various parameters influencing the determination of bismuth(III) were examined in detail. With 2 min accumulation, the analytical signal versus concentration dependence was linear up to 50 ppb, and the detection limit was 0.58 ppb. This modified electrode showed good resistance to the interferences from surface-active compounds and common ions.