Jiří Zima

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.

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.

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.

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.

A PTFE-based carbon adsorbent in high-performance liquid chromatography

Abstract A new type of carbon adsorbent, prepared by reduction of PTFE, was studied and modified with the aim of obtaining a material with a relatively homogeneous, non-polar surface for applications in high-performance liquid chromatography. Three types of sorbent differing in the specific surface area, oxygen remainder and porosity were investigated. The chromatographic behaviour of various solutes, both in non-polar (e.g., pentane) and polar (aqueous buffer) media, has been studied. The plots of natural logarithm of the capacity factor vs. the carbon number were reasonably parallel for a homologous series with different functional groups. The influence of the ionization of some amino acids on their retention over the whole pH range has been shown.

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).

Critical Review. High-performance liquid chromatography of nitrated polycyclic aromatic hydrocarbons

Josef Cvaĉkaa, Jiri Barek*a, Arnold G. Foggb, Josino C. Moreirac and Jiri Zimaa aUNESCO Laboratory of Environmental Electrochemistry, Department of Analytical Chemistry, Charles University, Hlavova 2030, 128 43 Prague 2, Czech Republic b Department of Chemistry, Loughborough University, Loughborough, Leicestershire, UK LE11 3TU c CESTEH/ENSP/FIOCRUZ, Rua Leopoldo Bulhoes 1480, Manguinhos, 21041-210 Rio de Janeiro, Brazil

Photodegradation of 1-nitropyrene in solution and in the adsorbed state

The photodegradation of the 1-nitropyrene (NPy) has been studied using conventional (Xe and medium pressure Hg lamps) and laser sources (XeCl excimer and Nd-YAG UV). Low energy monochromatic light sources were used to study the early stages of degradation (up to 50% conversion). The medium pressure Hg lamp was used for longer periods of irradiation (up to 6h) and for greater degradation of NPy. The results of our work confirm that degradation occurs by radical mechanism. Aromatic hydroxymethyl, methoxy, hydroxy and nitroso derivatives of pyrene (Py) are created by low energy UV irradiation. After a massive UV irradiation, the Py aromatic system is destroyed and more polar low-molecular compounds are generated. The photochemical method described in this paper, based on irradiation by UV lamp, is therefore, suitable for degradation of fused benzene ring(s) and thus should also be effective for degradation of other nitrated polycyclic aromatic compounds.

Polarographic and Voltammetric Determination of Trace Amounts of 9‐Nitroanthracene

The polarographic behavior of 3-nitrofluoranthene was investigated by DC tast polarography (DCTP) and differential pulse polarography (DPP), both at a dropping mercury electrode, differential pulse voltammetry (DPV) and adsorptive stripping voltammetry (AdSV), both at a hanging mercury drop electrode. Optimum conditions have been found for its determination by the given methods in the concentration ranges of 1 × 10 -6 -1 × 10 -4 mol l -1 (DCTP), 1 × 10 -7 -1 × 10 -4 mol l -1 (DPP), 1 × 10 -8 -1 × 10 -6 mol l -1 (DPV) and 1 × 10 -9 -1 × 10 -7 mol l -1 (AdSV), respectively. Practical applicability of these techniques was demonstrated on the determination of 3-nitrofluoranthene in drinking and river water after its preliminary separation and preconcentration using liquid-liquid and solid phase extraction with the limits of determination 4 × 10 -10 mol l -1 (drinking water) and 2 × 10 -9 mol l -1 (river water).

A method for the efficient degradation of melphalan into nonmutagenic products

Abstract A new chemical method has been developed for the destruction of an antineoplastic agent melphalane in laboratory waste, based on its oxidation by potassium permanganate in sodium hydroxide medium. To monitor the efficiency of destruction, analytical methods based on UV spectrophotometry, differential pulse voltammetry on a glassy carbon rotating disk electrode, and HPLC coupled with UV spectrophotometry have been developed. It has been demonstrated that the proposed method of destruction is highly efficient (more than 99.8% destruction) and the corresponding degradation products were found to be nonmutagenic to Salmonella typhimurium strains TA98, TA100, and TA1535, in both the presence and the absence of a rat liver S9 activation system.