Abstracts


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Stripping Analysis at Bismuth-Based Electrodes
Christos Kokkinos and Anastasios Economou

This article is intended as an overview of bismuth-based electrodes as applied to electrochemical stripping analysis. These electrodes rely on a bismuth or bismuth-modified active surface and, while they have analytical performance comparable to mercury electrodes, are characterized by negligible toxicity in comparison to their mercury counterparts. These properties make them ideally suited as sensors for trace monitoring by electrochemical stripping analysis. Topics covered in this review are the main types of bismuth electrodes and their fabrication, the analytical characteristics and common interferences of bismuth-based electrodes in stripping analysis and typical applications of these sensors in industrial, food, clinical and environmental analysis by stripping techniques. Finally, the future prospects of bismuth electrodes in conjunction with stripping analysis are critically discussed.


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³¹P NMR Spectroscopy of Phospholipids: from Micelles to Membranes
Jürgen Schiller, Matthias Müller, Beate Fuchs, Klaus Arnold and Daniel Huster

Phospholipids are the main constituents of biological membranes. Their amphiphilic character is responsible for the typical bilayer arrangement as the structural basis of biological membranes. In addition to their structural role, some phospholipids are of significant functional importance. They act as intercellular messengers and are involved in the pathogenesis of many diseases. Therefore, phospholipid research (“lipidomics”) has significantly advanced in the last decades, generating the need for fast, reliable, and informative analytical techniques. The aim of this review is to demonstrate the power of ³¹P nuclear magnetic resonance (NMR) spectroscopy for structural and analytical phospholipid research. High resolution ³¹P NMR provides information on the composition of phospholipid mixtures, whereas solid-state ³¹P NMR gives structural information about the sample phase and morphology. This review provides an introduction into the field and a short overview of currently used analytical and physicochemical methods to study these biomolecules. We will provide a theoretical description of ³¹P NMR spectroscopy and discuss methods for obtaining highly resolved phospholipid spectra. Selected applications of ³¹P NMR to aid phospholipid analysis and the investigation of phospholipid structures, membrane-peptide interactions, and enzyme activities are discussed. This review ends with an overview on ³¹P NMR applications to the analysis of body fluids, cells, and tissues.


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Calixarene HPLC Phases – Applications
Rüdiger Meyer and Thomas Jira

Calixarenes, following cyclodextrines and crown ethers, are the third generation of supramolecules used in HPLC as stationary phases. They consist of phenol units linked via methylene bridges and can also form inclusion complexes like the other host supramolecules. The resulting interactions influence the retention factors and improve the selectivity of the solutes. Additionally, modification of the calixarenes, for instance by varying the ring size, substitutents, conformations and pKa values, enable a more enhanced interaction spectrum and can improve the specificity for guest molecules.

The application of calixarenes in chromatography also includes medical and environmental applications, preparative chemistry as well as the rapidly developing area of supramolecular chemistry.

Taking the possibilities and the growing interests of calixarenes into account, the aim of the review is to summarise the application possibilities and interactions of calixarenes as stationary phase in HPLC.


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Electrochemical Stripping Techniques in Analysis of Nucleic Acids and Their Constituents
Miroslav Fojta, František Jelen, Ludek Havran and Emil Palecek

The ability of nucleic acids (NA) and their components to accumulate at electrode surfaces and electrochemical properties of these species are closely related. This review is devoted to electrochemical stripping techniques applied in NA studies. Cathodic or anodic stripping voltammetry have been used for a highly sensitive determination of nucleobases, nucleosides, nucleotides or acid-hydrolyzed NAs, based on formation of sparingly soluble complexes of the NA constituents with electrochemically generated mercury or copper(I) ions. DNAs, RNAs and their synthetic analogues, either unmodified or labeled with electroactive markers, have been analyzed by adsorptive stripping (AdS) techniques with mercury, mercury film, amalgam and carbon-based electrodes. Strong adsorption of NAs at the electrode surfaces has been utilized in adsorptive transfer stripping (AdTS) techniques. In AdTS, a NA-modified electrode is prepared by adsorptive accumulation of the NA at the electrode surface, followed by transfer into background electrolyte not containing any NA. NA-modified electrodes can be used as simple electrochemical NA sensors. Recent applications of AdS and AdTS in NA microanalysis, in detection of DNA damage as well as in studies of DNA hybridization or DNA-protein interactions are reviewed.


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Microelectrode Arrays and Microfabricated Devices in Electrochemical Stripping Analysis
Valerio Beni and Damien W.M. Arrigan

In this article a comprehensive overview of the developments in the field of electrochemical stripping analysis with microelectrode arrays and microfabricated devices is presented. Due to the vastness of the topic, this mini-review deals only with the use of regular microelectrode arrays. After the description of the main fabrication methodologies employed, a large part of the review is dedicated to applications, categorised by the electrode material. Microelectrode arrays have found application in several areas of electroanalytical science including clinical and environmental analysis. They have been used for the detection of heavy metals in waters, soil extracts and blood, proving to be reliable analytical devices and bringing the advantages of low-cost, simplicity of use and easy adaptability to field measurement. In many applications, limits of detection are sub-parts per billion. Finally a short section of the review discusses miniaturised potentiostats.


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Adsorptive Stripping Voltammetry of Environmental Carcinogens
Jiri Barek, Karolina Peckova and Vlastimil Vyskocil

This review describes our recent results regarding adsorptive stripping voltammetric determination of submicromolar and nanomolar concentrations of various environmentally important chemical carcinogens using both traditional (hanging mercury drop electrode, carbon paste electrode) and non-traditional types of electrodes (solid amalgam electrodes, glassy carbon paste electrodes, carbon ink film electrodes, solid composite electrodes). The review concentrates on our own results in the context of the general development in the filed.


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Cyclodextrins Host- Guest Chemistry in Analytical and Environmental Chemistry
Sayo O. Fakayode, Mark Lowry, Kristin A. Fletcher, Xiaodong Huang, Aleeta M. Powe and Isiah M. Warner

Native and modified cyclodextrins (CDs) have been shown to dramatically affect the properties of guest molecules solubilized within the relatively hydrophobic interior. By monitoring changes in photophysical processes, researchers have been able to determine the stoichiometry and association constants of the resulting complexes. In addition, chemical modification of the CD structure as well as the selective binding of analytes within the CD cavity has lead to remarkable advances in analytical and environmental applications of CDs. In this review, we discuss a selection of fundamental studies performed in our laboratory, primarily using fluorescence spectroscopy as a tool to study the properties of CD host-guest complexes. In addition, this review includes recent studies conducted in other laboratories which are concerned with exploiting the unique properties of CDs and their inclusion complexes in order to study energy transfer through the use of photochemical antennas as well as the development of chemical and environmental sensors.


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Recent Developments in Stripping Analysis on Microelectrodes
Salvatore Daniele, M. Antonietta Baldo and Carlo Bragato

This review surveys the main aspects of the combination of microelectrodes and stripping analysis, including recent developments in working microelectrodes, analytical methodologies, instrumentation, and applications in both synthetic and real matrices. Emphasis is given to papers published since 2000.


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Stripping Analysis Enhanced by Ultrasound, Electrode Heating and Magnetic Fields
Peter Gründler

Stripping analysis is a two-step procedure. In the first step, the analyte is accumulated at an electrode surface either by electrolysis or by adsorption. In the second step, the deposited material is removed, typically by electrolysis. The second step is the source of the analytical signal. Sensitivity of the method mainly depends on the amount of substance which is transferred to the electrode surface during accumulation. The methods reviewed make use of unconventional techniques to enhance efficiency of accumulation. By ultrasound, a combined action of thermal and mechanical impacts, partially with extreme energetic states, causes improvement of analytical results. Heating of electrodes or of a nearelectrode area induces laminar electrolyte flow acting as stirring, combined with increased surface temperature that is helpful to lower kinetic hindrances. Magnetic fields in a cell with arbitrarily increased deposition current enhances convection without additional thermal effects. Most of the techniques reviewed are able to improve the efficiency of stripping analysis much more than could be done by driving classical stirring up to the limits.


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Application of Capillary Electrophoresis in Drug Metabolism Studies
Jie Zhang, Jirí Konecný, Zdenek Glatz, Jos Hoogmartens and Ann Van Schepdael

Capillary electrophoresis (CE) has been increasingly employed for the separation of pharmaceutical agents and drugs. This has arisen from the complementary mode of separation afforded by CE when compared to high performance liquid chromatography (HPLC). Qualities of CE such as high efficiency of separation, short analysis time, remarkably low injection volume and a variety of detection systems have facilitated acceptance of this technology. Since different drug metabolite enantiomers are formed in many metabolic pathways, the other indispensable advantage of CE over HPLC is the possibility of chiral separation without the need of special expensive columns. Recent advances in automated systems have made CE even more popular. The focus of this paper is to review recent studies and advances (mainly from 2000) of drug metabolism by using CE. The review is divided into two parts: (i) principles of CE separation of drugs and their metabolites and (ii) application of CE in drug metabolism studies. The first part introduces sample preparation, separation and detection modes involved in CE drug metabolism studies. To provide a deeper insight into the achievements, distinction between drug metabolism analysis in vivo and in vitro is made in the second part. Reported methods are discussed and summarized.