Ivan Švancara

Carbon Paste Electrodes in Modern Electroanalysis

Recent trends and advances in the electrochemistry with both unmodified and modified carbon paste electrodes are reviewed (247 refs.). Present day knowledge of their basic physico-chemical properties and characteristics is surveyed, including some specifics important in electrochemical measurements. Special attention is paid to the possibilities of carbon paste-based electrodes in electrochemical investigations and in modern electroanalysis of inorganic ions or molecules, organic substances, biologically important compounds, and pharmaceuticals.

Carbon paste electrodes in the new millennium

In this review (with 500 refs), both electrochemistry and electroanalysis with carbon paste-based electrodes, sensors, and detectors are of interest, when attention is focused on the research activities in the years of new millennium. Concerned are all important aspects of the field, from fundamental investigations with carbon paste as the electrode material, via laboratory examination of the first electrode prototypes, basic and advanced studies of various electrode processes and other phenomena, up to practical applications to the determination of inorganic ions, complexes, and molecules. The latter is presented in a series of extensive tables, offering a nearly complete survey of methods published within the period of 2001–2008. Finally, the latest trends and outstanding achievements are also outlined and future prospects given.

Recent Advances in Electroanalysis of Organic Compounds at Carbon Paste Electrodes

In this review (with 223 refs), electroanalysis of organic compounds with carbon paste-based electrodes, sensors, and detectors is discussed. The individual methods, covering the period of 2004–2008, are summarized in tables with accompanying commentaries, attention being paid to environmental pollutants, pharmaceutical formulations and drugs, as well as other biologically active organic compounds. Recent achievements and trends are discussed, critically evaluated, and some future prospects are outlined.

Amperometric Determination of Hydrogen Peroxide With a ManganeseDioxide-modified Carbon Paste Electrode Using Flow InjectionAnalysis

A carbon paste electrode bulk modified with MnO 2 was investigated as an amperometric detector for hydrogen peroxide in flow injection analysis (FIA). With an operating potential of +0.46 V versus Ag/AgCl, H 2 O 2 produces catalytic oxidation currents which can be exploited for quantitative determinations. Factors influencing the analytical performance of the electrode, such as paste composition and pH, were studied both for batch voltammetry and for FIA. For the flow system the influence of the injection volume and flow rate were examined. The amperometric signals are linearly proportional to H 2 O 2 concentrations in the range 0.5–350 mg l - 1 , showing a detection limit (three times the signal-to-noise ratio) of 45 µg l - 1 .

A study on the determination of chromium as chromate at a carbon paste electrode modified with surfactants

A procedure for the determination of chromium is described based on synergistic pre-concentration of the chromate anion at a carbon paste electrode modified in situ with quarternary ammonium salts such as 1-ethoxycarbonylpentadecyltrimethylammonium bromide (Septonex((R))), cetyltrimethylammonium bromide (CTAB) or cetylpyridinium bromide (CPB). The proper electrochemical detection utilises the reduction Cr(VI) --> Cr(III) performed in the differential pulse cathodic voltammetric mode. In discussion, considerable attention has been paid to the accumulation mechanism at the carbon paste electrode in the presence of surfactants. Furthermore, after optimising the corresponding experimental conditions (0.1-0.3M HCl + 0.1M NaCl as the supporting electrolyte, 2.5-25muM as the total concentration of modifier, pre-concentration at +0.7V versus Ag/AgCl and the stripping from +0.7 to -0.4V), the analytical performance of the method has been evaluated. The signal of interest was reproducible within +/-8% and proportional to the concentration in a range of 0.5-50muM CrO(4)(2-), with a limit of detection (S/N = 3:1) of about 5x10(-8)M CrO(4)(2-) (with accumulation for 300s). Interference studies were focused mainly on the species capable of forming ion-pairs with the modifier; i.e., TlCl(4)(-), AuCl(4)(-), PdCl(4)(2-), PtCl(6)(2-), VO(4)(3-), MnO(4)(-) and I(-). Practical applicability of the method was tested on model solutions via the recovery rates (typically 90-110%) or using selected certified reference materials (tea, bush leaves, clover) and two samples of black tea when the respective results were compared to those obtained by the reference determinations with ICP-AES.

(Bio)sensors based on manganese dioxide-modified carbon substrates: retrospections, further improvements and applications

An overview is presented which summarizes our accomplishment in the development of sensors and biosensors based on heterogenous carbon electrodes modified with manganese dioxide. Brief account of each sensor and biosensor has been given and example of real sample applications provided where appropriate.

Determination of arsenic at a gold-plated carbon paste electrode using constant current stripping analysis

A new stripping method for the determination of arsenic in water samples with a gold film-plated carbon paste electrode has been developed for the use in constant current stripping analysis (CCSA). In the novelized procedure, differentiation between As(III) and chemically pre-reduced As(V), the effect of Cu(II) on the response of arsenic, and the stability of sample solutions were studied in detail. Compared to the voltammetric approach, the method utilizing CCSA offers a more rapid procedure with improved analytical characteristics such as reproducibility, selectivity over the Cu(II) ions, or lower detection limit (3 ppb for As(III) and 0.5 ppb for As(V), respectively). The possibilities of the optimized method are demonstrated by determinations of As(III), As(V), and total arsenic in samples of polluted river water.

Voltammetry with carbon paste electrodes containing membrane plasticizers used for PVC-based ion-selective electrodes

Abstract Carbon paste electrodes were prepared by mixing graphite powder with liquids that have been applied as plasticizers for membranes of ion-selective electrodes. In voltammetric measurements, these electrodes exhibited interesting properties such as a wide anodic and cathodic potential range, very low reduction peak of oxygen in the cathodic scan and high extraction and adsorption capabilities. They were shown to be convenient, especially for the selective accumulation of metals in the form of their anionic complexes. Two examples are given. The voltammetric behaviour of gold as its [AuCl4]− complex and of bismuth as the [BiI4]− anion is discussed.

AMPEROMETRIC DETERMINATION OF GLUCOSE WITH AN MnO2 AND GLUCOSE OXIDASE BULK-MODIFIED SCREEN-PRINTED CARBON INK BIOSENSOR

A simple biosensor, constructed by bulk-modification of carbon ink with manganese dioxide as a mediator and glucose oxidase as a biocomponent was investigated for its ability to serve as amperometric detector for glucose in hydrodynamic as well as in flow injection analysis (FIA) mode. The sensor could be operated at a potential of 0.48 V under physiological conditions (0.1 M phosphate buffer, pH 7.5) and exhibited excellent reproducibility and stability. Factors influencing the amperometric response such as injection volume, flow rate and applied working potential were studied in detail. The screen-printed electrode exhibited a linear amperometric increase with the concentration of D-glucose from 2 to 2500 mg L−1 and gave a 3σ detection limit of 0.085 mg L−1. Due to its remarkable stability such a sensor could be operated continuously for more than four weeks or more than 1000 sample injections. No change of signal height could be observed within an operation period of 12 h. The sensor was exploited for FIA-amperometric determination of glucose in beer and wine samples

Trace level voltammetric determination of lead and cadmium in sediment pore water by a bismuth-oxychloride particle-multiwalled carbon nanotube composite modified glassy carbon electrode

Two multiwalled carbon nanotubes-based composites modified with bismuth and bismuth-oxychloride particles were synthesized and attached to the glassy carbon electrode substrate. The resultant configurations, Bi/MWCNT-GCE and BiOCl/MWNT-GCE, were then characterized with respect to their physicochemical properties and electroanalytical performance in combination with square-wave anodic stripping voltammetry (SWASV). Further, some key experimental conditions and instrumental parameters were optimized; namely: the supporting electrolyte composition, accumulation potential and time, together with the parameters of the SWV-ramp. The respective method with both electrode configurations has then been examined for the trace level determination of Pb(2+) and Cd(2+) ions and the results compared to those obtained with classical bismuth-film modified GCE. The different intensities of analytical signals obtained at the three electrodes for Pb(2+) and Cd(2+) vs. the saturated calomel reference electrode had indicated that the nature of the modifiers and the choice of the supporting electrolyte influenced significantly the corresponding stripping signals. The most promising procedure involved the BiOCl/MWCNT-GCE and the acetate buffer (pH 4.0) offering limits of determination of 4.0 μg L(-1) Cd(2+) and 1.9 μg L(-1) Pb(2+) when accumulating for 120 s at a potential of -1.20 V vs. ref. The BiOCl/MWCNT electrode was tested for the determination of target ions in the pore water of a selected sediment sample and the results agreed well with those obtained by graphite furnace atomic absorption spectrometry.