Jiří Barek

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.

Boron-Doped Diamond Film Electrodes—New Tool for Voltammetric Determination of Organic Substances

This review with 194 references summarizes the recent progress in the development and applications of boron-doped diamond film electrodes in electroanalysis of organic compounds. It is based on the survey of 106 papers listed in a comprehensive table devoted to batch voltammetric and liquid flow amperometric methods using boron-doped diamond electrodes. The varieties in their construction, surface pre-treatment and electroanalytical methods used are discussed. Special attention is paid to miniaturized boron-doped diamond electrodes for in vitro/in vivo sensing, or electrochemical detection coupled to conventional or chip-based electrophoretic detection systems. Further, possibilities and limitations of surface modification are discussed.

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.

Analytical Applications of Solid and Paste Amalgam Electrodes

The review describes working and reference electrodes based on solid and/or paste amalgams and their application for voltammetric, amperometric, and potentiometric determination of both inorganic and organic analytes. Attention is paid to their preparation, pre-treatment and possible modification, and their application in classical voltammetric arrangements, in flowing systems (HPLC-ED, FIA-ED), and in adsorptive transfer stripping voltammetry. The review confirms that amalgam electrodes can successfully substitute mercury electrodes and, in some special cases, offer possibilities not available to mercury electrodes.

Polarography and Voltammetry at Mercury Electrodes

Scope and limitations of modern polarographic and voltammetric techniques on mercury electrodes are discussed and many practical examples of their applications in practical analysis are given to demonstrate that even in the third millennium polarography and voltammetry at mercury electrodes can be very useful analytical tools, which in certain cases can successfully compete with modern spectroscopic and separation techniques.

Mercury Electrodes–Possibilities and Limitations in Environmental Electroanalysis

Recent developments in the use of polarography and voltammetry at mercury electrodes in environmental analysis are reviewed and their combination with preliminary separation and pre-concentration using liquid or solid phase extraction is discussed. Attention is focused on ecotoxic nitrated polycyclic aromatic hydrocarbons, heterocyclic compounds, and pesticides. Advantages and limitations of mercury electrodes are critically evaluated and some recent applications of these techniques developed in our laboratory are given.

Voltammetric Determination of Nitronaphthalenes at a Silver Solid Amalgam Electrode

Abstract Electrodes based on amalgam materials were re-introduced in electroanalytical chemistry in the year 2000, partially as reaction to unsubstantiated public fears of liquid mercury. In this publication, the voltammetric behavior of 1-nitronaphthalene and 2-nitronaphthalene was investigated at a mercury meniscus-modified silver solid amalgam electrode. The reduction mechanism in mixed neutral buffer-methanol medium includes the four-electron reduction to hydroxylaminoderivative followed by a two-electron reduction to the amine in acidic medium, similarly to mercury electrodes. In alkaline media, both compounds show the splitting of the main four-electron reduction peak typical for mercury electrodes in two new ones, the first one corresponding to a one electron reduction of the nitroderivative to the nitro radical anion, which was confirmed by microcoulometry. Using optimized conditions (differential pulse voltammetry, Britton-Robinson buffer pH 7.0 – methanol (9:1) medium) the calibration dependences are linear in the range of 2·10−7 (4·10−7) to 1·10−4 mol L−1 for 1-nitronaphthalene (2-nitronaphthalene). After preconcentration of the analytes from drinking and river water samples using solid phase extraction the limit of determination was lowered to ∼3·10−8 mol L−1.

Voltammetric Determination of Carcinogenic Derivatives of Pyrene Using a Boron-Doped Diamond Film Electrode

Based on the study of voltammetric behavior of carcinogenic 1-nitropyrene (1-NP), 1-aminopyrene (1-AP), and 1-hydroxypyrene (1-HP), optimum conditions have been found for the determination of these analytes by differential pulse voltammetry (DPV) at a boron-doped diamond film electrode. The optimum medium was methanol-Britton–Robinson buffer (BR buffer) pH 3.0 (70:30) for 1-NP and 1-AP, and methanol-BR buffer pH 5.0 (70:30) for 1-HP. Concentration dependences of the DPV response were measured in the range 1 · 10−6–1 · 10−4 mol dm−3 (R = −0.9998) with the limit of detection (LOD) 3 · 10−7 mol dm−3 for 1-NP, 1 · 10−7–1 · 10−5 mol dm−3 (R = 0.9971) with LOD 6 · 10−8 mol dm−3 for 1-AP, and 1 · 10−7–1 · 10−5 mol dm−3 (R = 0.9934) with LOD 1 · 10−7 mol dm−3 for 1-HP. Simultaneous determination of 1-NP and 1-AP in a mixture was tested in the methanol-BR buffer pH 3.0 (70:30) medium as well. The content of 1-AP in the concentration range from 1 · 10−6 to 1 · 10−4 mol dm−3 had no effect on the sensitivity of the determination of 1-NP, and vice versa. Due to the close peak potentials of 1-AP and 1-HP, the direct determination of their mixture using voltammetric methods is impossible.

Polarographic and voltammetric determination of triazine-based reactive azo dyes with 4-carboxypyridyl and 1,4-diazabicyclo[2,2,2]octanyl (DABCO) leaving groups

Abstract Direct current and differential pulse polarograms of reactive triazine-based azo dyes containing 4-carboxypyridyl and 1,4-diazabicyclo[2,2,2]octanyl (DABCO) leaving groups show one wave or peak corresponding to reduction of the azo group and other waves or peaks at more negative potentials corresponding to the reduction of reactive groups. Optimum conditions were found for polarographic and voltammetric determination at submicromolar concentrations of the test dyes based on azo group reduction. The peaks corresponding to the reduction of the reactive group can be used for monitoring the hydrolysis of the test dyes.

An Amperometric Detector with a Platinum Tubular Electrode for High Performance Liquid Chromatography

An amperometric detector based on a platinum tubular electrode was constructed from a long narrow-bored platinum tube which was directly connected to the column outlet. The tube is immersed in a vessel containing an electrolyte solution in which a common reference and counter electrodes are also immersed. Only the internal platinum wall is exposed to the electrolyte solution. At this geometrical arrangement, the platinum tube internal wall is nonuniformly polarized so that only a certain length of the tube from its outlet attains a potential suitable for the detection. As a result, the detector effective volume is substantially lower than the platinum tube total geometric volume. The detector was tested both in conventional and micro-HPLC systems. The peak parameters obtained with the test detector are comparable with those obtained with a standard spectrophotometric detector. However, the detector dynamic range from 2×10–8 to 5×10–3 mol L–1, linear dynamic range from 2×10–8 to 2×10–5 mol L–1 and a limit of detection 2×10–8 mol L–1 were obtained for a test compound (1-aminonaphthalene).