Abstracts

Abstract

SOME RECENT DESIGNS AND DEVELOPMENTS OF SCREEN‐PRINTED CARBON ELECTROCHEMICAL SENSORS/BIOSENSORS FOR BIOMEDICAL, ENVIRONMENTAL, AND INDUSTRIAL ANALYSES—AN OVERVIEW by John P. Hart, Adrian, Crew, Eric Crouch, Kevin C. Honeychurch, and Roy M. Pemberton, Centre for Research in Analytical, Materials, and Sensors Science, Faculty of Applied Sciences, University of the West of England, Bristol, UK

ABSTRACT: This review describes the design and fabrication of electrochemical sensors/biosensors based on screen‐printing technology and their applications in pharmaceutical, biomedical, environmental, and industrial analyses. Specific emphasis is placed on naturally‐occurring biomolecules, drugs, and potential environmental and industrial pollutants or toxins.

Analytical Letters, 37(5), 789–830, 2004

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ELECTROCHEMICAL ANALYSIS OF OPIATES—AN OVERVIEW by Jorge M. P. J. Garrido and Cristina Delerue‐Matos, CEQUP/Departamento de Engenharia Química, Instituto Superior de Engenharia do Porto, Porto, Portugal; Fernanda Borges, CEQOFFUP/Departamento de Química Orgânica, Faculdade de Farmácia Universidade do Porto, Porto, Portugal; Tice R. A. Macedo, Faculdade de Medicina, Universidade de Coimbra, Coimbra, Portugal; A. M. Oliveira‐Brett, Departamento de Química, Faculdade de Ciências e Tecnologia Universidade de Coimbra, Coimbra, Portugal

ABSTRACT: The analysis of opiates is of vital interest in drug abuse monitoring and research. This review presents a general overview of the electrochemical methods used for detection and quantification of opiates in a variety of matrices. Emphasis has been placed on the voltammetric methods used for study and determination of morphine, codeine, and heroin. Specific issues that need to be solved and better explained as well as future trends in the use of electrochemical methods in the examination of opiates are also discussed.

Analytical Letters, 37(5), 831–844, 2004

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ION‐SELECTIVE ADSORPTION/DESORPTION PROCESSES AT INORGANIC MATERIALS/SOLUTION INTERFACES AS A NOVEL MODE FOR ION SENSING by Yukinori Tani and Yoshio Umezawa, Institute for Environmental Sciences, University of Shizuoka, Yada, Shizuoka, Japan and Department of Chemistry, School of Science, The University of Tokyo, Hongo, Tokyo, Japan

ABSTRACT: Several studies on response mechanisms of solid membrane ion‐selective electrodes (ISEs) and developments of ion sensors mainly from the authors' laboratory were reviewed. Face‐specific responses of CdS single crystals showed that ion‐selective response of solid membrane ISEs based on scarcely soluble salts is due to adsorption of component ions, and resultant charge separation at the membrane/solution interfaces. Potentiometric response mechanisms of CuS‐based ISEs in metal buffer solutions were discussed. Crystal surfaces of scarcely soluble inorganic salts were formed to provide remarkably selective molecular recognition sites at which adsorbed component ions were detected by an underlying quartz crystal microbalance (QCM). Not only single layer adsorption of component ions on the respective inorganic salt, but also multilayer crystal formations at QCM surface also showed ion‐selective response to the respective component ions. Ion selectivities of ion sensors based on scarcely soluble salts, which include ISE and QCM, are basically limited by solubility products. Several studies on ISEs based on inorganic materials having a three‐dimensional (3D) network structure with interstitial ions demonstrated that for ion‐selective responses the formation of vacant sites be required by dissolution of the interstitial ions from the membrane surfaces during the pretreatment. For these ISEs, potentiometric selectivities are essentially governed by size and dehydration energies of analyte ions. Taken these together, approaches for ion‐sensor developments based on inorganic materials were critically evaluated and updated.

Analytical Letters, 37(5), 845–869, 2004

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DEVELOPMENT AND CHARACTERIZATION OF COBALT HEXACYANOFERRATE MODIFIED CARBON ELECTRODES FOR ELECTROCHEMICAL ENZYME BIOSENSORS by Monica Florescu, Departamento de Química, Universidade de Coimbra, Coimbra, Portugal and Department of Physics, Transilvania University of Brasov, Brasov, Romania; Christopher M. A. Brett, Departamento de Química, Universidade de Coimbra, Coimbra, Portugal

ABSTRACT: Carbon film electrode have been modified with films of cobalt hexacyanoferrate by potential cycling from solutions containing cobalt and hexacyanoferrate ions. The voltammetric characteristics of the films have been investigated in different electrolyte solutions and the properties related to insertion reactions within the crystal structure. The application of these modified electrodes as redox mediators in enzyme biosensors has been investigated using the mediated detection of hydrogen peroxide, demonstrated by the determination of glucose using glucose oxidase. Excellent detection limits in the micromolar region have been attained and the principle of measurement in real samples demonstrated by that of glucose in sweet wine.

Analytical Letters, 37(5), 871–886, 2004

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DEVELOPMENT AND CHARACTERIZATION OF COLLOIDAL GOLD‐CYSTEAMINE‐CARBON PASTE ELECTRODES by J. Manso, L. Agüí, P. Yáñez‐Sedeño, and J. M. Pingarrón, Department of Analytical Chemistry, Faculty of Chemistry, University Complutense of Madrid, Madrid, Spain

ABSTRACT: The optimal conditions for the preparation of colloidal gold‐carbon paste electrodes (CPEs) by using CPEs modified with cysteamine (Cyst) are discussed. Cysteamine modified‐CPEs (Cyst‐CPEs) were prepared by immersion in a Cyst solution, the experimental variables involved in this modification process being optimized. Different colloidal gold deposition methods on the Cyst‐CPEs were evaluated by recording cyclic voltammograms of methionine solutions. Better electrochemical responses were found for colloidal gold‐Cyst‐CPEs (nAu‐Cyst‐CPEs) prepared by immersion of Cyst‐CPEs in a colloidal gold suspension for 4 hr. Optimization of the different experimental variables involved (colloidal particle size and time of immersion) was also carried out. The surface of nAu‐Cyst‐CPEs was characterized by SEM, and the gold coating electrochemically tested. A surface coverage, Γ, of 3.07 × 10⁻¹⁰ mol cm⁻² was obtained. The analytical suitability of nAu‐Cyst‐CPEs was verified by testing the voltammetric behavior of several compounds with sulfur atoms.

Analytical Letters, 37(5), 887–902, 2004

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HORSERADISH PEROXIDASE ELECTRODE FOR THE ANALYSIS OF CLOZAPINE by B. Blankert, W. El Ayyas, and J.‐M. Kauffmann, Pharmaceutical Institute, Université Libre de Bruxelles, Brussels, Belgium; O. Dominguez and J. Arcos, Department of Chemistry, University of Burgos, Spain

ABSTRACT: A horseradish peroxidase (HRP) immobilized electrode was developed for the assay of the antipsychotic compound clozapine (CLZ). The biosensor was made of HRP crosslinked with glutaraldehyde and bovine serum albumin (BSA) and blended in the electrode matrix. The latter was a carbon paste based on solid paraffin and graphite particles. A dialysis membrane was secured at the tip of the enzyme based electrode. Cyclic voltamperometry at the solid carbon paste electrode (sCPE) permitted to point out a reversible pattern for CLZ electrooxidation attributed to a relatively stable nitrenium ion. The formation of the latter and of a newly generated species, was inferred at the biosensor. The electroreduction of these generated species was performed at the biosensor at an applied potential of 0.0 V vs. Ag/AgCL 3 M KCl. Several experimental parameters influencing the biosensor response were studied such as pH, buffer composition, and detection potential. The resulting biosensor offered, at pH 4.5 in Britton–Robinson buffer (BRb) in the presence of 0.1 mM H₂O₂ and at 0.0 V vs. Ag/AgCl, a linear response in the concentration range comprized between 1.0 × 10⁻⁶ M and 1 × 10⁻⁵ M with a detection limit of 1.7 × 10⁻⁷ M and a quantification limit of 5.6 × 10⁻⁷ M. In addition to the mechanistic information provided, the biosensor was found useful for the determination of CLZ in tablets. The accuracy of the assay was checked by capillary electrophoresis (CZE).

Analytical Letters, 37(5), 903–913, 2004

Abstract

VOLTAMMETRY OF DICLOFENAC AT GRAPHITE, CARBON COMPOSITES, AND MOLECULARLY IMPRINTED POLYMER‐COMPOSITE ELECTRODES by M. Carmen Blanco‐López, Laura Fernández‐Llano, M. Jesús Lobo‐Castañón, Arturo J. Miranda‐Ordieres, and Paulino Tuñón‐Blanco, Departamento de Química Física y Analítica, Universidad de Oviedo, Oviedo, Spain

ABSTRACT: The electrochemical behavior of diclofenac (DCF) at graphite electrodes was investigated. The drug is irreversibly oxidized at 0.84 V (pH 1), giving rise to some products, which exhibit two reversible process with formal potential of 0.39 and 0.63 V. Carbon composite electrodes of different nature [polytetrafluoroethylene‐graphite (PTFE‐G), epoxy‐graphite (EG), epoxy‐carbon black (E‐CB)] were also investigated for voltammetric detection of DCF. A similar electrochemical behavior was observed on these electrodes although graphite was preferred over carbon black as conducting phase, and both PTFE and epoxy could act as agglomerant. Electrodes constructed with these materials could be modified with molecularly imprinted polymers (HIPs), and allowed detection of DCF after incubation in an acetonitrile solution of the drug.

Analytical Letters, 37(5), 915–927, 2004

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CYTOCHROME P450_2D6 (CYP2D6) BIOELECTRODE FOR FLUOXETINE by E. I. Iwuoha and N. G. R. Mathebe, Department of Chemistry, University of the Western Cape, Bellville, Cape Town, South Africa; A. Wilson and D. Narinesingh, Department of Chemistry, University of The West Indies, St Augustine, Trinidad and Tobago; M. Howel and K. Montane‐Jaime, Department of Pharmacology, Faculty of Medicine, University of The West Indies, St Augustine, Trinidad and Tobago; A. Guiseppi‐Elie, Center For Bioelectronics, Biosensors And Biochips (C3b), Virginia Commonwealth University, School of Engineering, Richmond, Virginia, USA

ABSTRACT: A bioelectrode system consisting of polyaniline (PAn)‐doped glassy carbon electrode (GCE) and cytochrome P450_2D6 (CYP2D6) enzyme solution was used for the amperometric study of in vitro fluoxetine biotransformation. The PAn film was potentiostatically grown at +700 mV vs. Ag/AgCl (20°C) on a 0.071 cm² GCE and used for cyclic voltammetric (CV) measurements in phosphate buffer solution (0.1 M, pH 7.5, 0.1 M KCl) of the enzyme. The response of the CYP2D6 bioelectrode to fluoxetine was consistent with uncompetitive substrate inhibition kinetics. Apparent Michaelis–Menten constant K _m′ of the CYP2D6 electrode was 3.7 µmol L⁻¹, which is within the intra‐hepatic fluoxetine concentration between 2 and 7 µmol L⁻¹. Thus PAn‐mediated electrochemistry can be used to observe the monooxygenation reaction of CYP2D6. K _m′ is the apparent Michaelis–Menten constant and K _i′ is the apparent substrate inhibition constant.

Analytical Letters, 37(5), 929–941, 2004

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DEVELOPMENT OF ELECTROCHEMICAL IMMUNOSENSOR FOR PROGESTERONE ANALYSIS IN MILK by Mark P. Kreuzer, Rafael McCarthy, Miloslav Pravda, and George G. Guilbault, Department of Chemistry, Analytical and Biological Chemistry Research Facility, University College Cork, Ireland

ABSTRACT: A disposable electrochemical biosensor, based on a screen‐printed carbon electrode (SPE) coated with a progesterone (prog)–BSA conjugate, has been prepared and evaluated for measuring progesterone in cows' milk. The immunosensor was employed in an indirect competitive assay format involving anti‐progesterone monoclonal antibody and anti‐species antibody labeled with the enzyme alkaline phosphatase (AP). Differential pulse voltammetry (DPV) and amperometry were used as electrochemical means to detect the product of the enzymatic reaction [p‐aminophenol (p‐AP)]. Amperometric detection was carried out at +350 mV vs. Ag/AgCl reference electrode. The DPV detection was in the potential range of +100 to +500 mV vs. Ag/AgCl reference electrode. Progesterone was detectable in milk matrix by sigmoidal curve (variable slope) method from 13 to 189 ng/mL and from a linear calibration between 16 and 256 ng/mL with an associated limit of detection (LOD) of 3 ± 2 ng/mL progesterone. The use of DPV improved the accuracy of our measurements over conventional amperometric detection by electrode background correction. Errors were significantly lower by this method and allows for non‐hydrodynamic conditions and thus the possibility of decentralization from the laboratory environment allowing on‐site (farm) determination of estrous.

Analytical Letters, 37(5), 943–956, 2004

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DIFFERENTIATIONS IN THE ELECTROCHEMICAL BEHAVIOUR OF THE INTERACTIONS BETWEEN DNA AND COMPOUNDS WITH AFFINITY FOR DNA by I. Ch. Gherghi and R. Tzimou‐Tsitouridou, Analytical Chemistry Laboratory, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece; S. Th. Girousi and A. N. Voulgaropoulos, Analytical Chemistry Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece

ABSTRACT: The interest of developing sensors for medical use is growing rapidly. The potential clinical applications of such devices are enormous and they are expected to have a major impact on health care. Especially, electrochemical DNA biosensors are hoped to be applied to the detection of toxic compounds presenting affinity for DNA, to drug design, gene delivery, and o the detection of infectious or inherited diseases.

Analytical Letters, 37(5), 957–966, 2004

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HYDROGEN ELECTROSORPTION IN PD‐PT‐RH ALLOYS IN THE PRESENCE OF ADSORBED CO by M. Łukaszewski, M. Grdeń, and A. Czerwiński, Department of Chemistry, Warsaw University, Warsaw, Poland; M. Łukaszewski and A. Czerwiński, Industrial Chemistry Research Institute, Warsaw, Poland

ABSTRACT: Electrosorption of hydrogen in Pd‐Pt‐Rh alloys in the presence of adsorbed carbon monoxide has been examined using cyclic voltammetry (CV). CO adsorption has a remarkable influence on both hydrogen adsorption and absorption. Hydrogen adsorption is strongly inhibited by CO adsorption products. The processes of hydrogen absorption and desorption are not totally blocked but proceed much slower than in the absence of CO adsorbates. On electrodes covered with adsorbed CO oxidation of absorbed hydrogen is shifted to higher potentials.

Analytical Letters, 37(5), 967–978, 2004

Abstract

VOLTAMMETRIC AND SPECTROSCOPIC STUDIES OF CHARGED AND UNCHARGED DIFERROCENE DERIVATIVES AT REGULAR AND LOW IONIC STRENGTH SOLUTIONS by Anna Maria Nowicka and Zbigniew Stojek, Department of Chemistry, Warsaw University, Warsaw, Poland; Malgorzata Ciszkowska, Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, New York, USA

ABSTRACT: Electroanalytical aspects of voltammetric behavior of diferrocenemethanol, sodium diferrocenemethanolan, (diferrocenyl)methyltrimethylammonium hexafluorophosphate, and 1,2‐diferrocenyloethane were studied. Special attention was paid to the differences in the wave heights caused by the presence and absence of supporting electrolyte. Linear scan voltammetry (LSV) and normal pulse voltammetry (NPV) were employed in the investigation. The differocenes synthesized differ in charge and in the interactions between the two redox centers. They have both iron atoms at the +2 oxidation number. The charged diferrocenes offer not only a good internal potential scale in electroanalysis, as does the uncharged diferrocene, but are also sensitive to ionic strength in the solution. In the absence of supporting electrolyte, no second voltammetric wave was obtained for the (diferrocenyl)methyltrimethylammonium cation. The IR and UV‐VIS spectroscopic characteristic have been done for all diferrocenes studied.

Analytical Letters, 37(5), 979–994, 2004

Abstract

ANODIC STRIPPING VOLTAMMETRY AT BISMUTH‐COATED AND UNCOATED CARBON MICRODISK ELECTRODES: APPLICATION TO TRACE METALS ANALYSIS IN FOOD SAMPLES by Maria Antonietta Baldo and Salvatore Daniele, Department of Physical Chemistry, University of Venice, Venice, Italy

ABSTRACT: This article reports on the performance of a bismuth‐coated carbon microdisk electrode (BiFμE) for the determination of trace heavy metals by anodic stripping voltammetry (ASV). The BiFμE was prepared by electrodeposition of a metallic bismuth film onto the microdisk, by applying an in‐situ electroplating procedure. To test the performance of the BiFμE, ASV measurements were performed on synthetic solutions containing Cd²⁺, Pb²⁺, and Cu²⁺ as target ions. The results indicated that cadmium and lead gave well‐defined ASV peaks with no interference, and their quantitative determination could be carried out straightforwardly. In particular, linear calibration curves over the range 5.0 × 10⁻⁸–1.0 × 10⁻⁶ M for both ions, and detection limits of 7.8 and 2.9 nM, for cadmium and lead, respectively, after applying a 60 sec preconcentration step, were obtained. The reproducibility was also satisfactory, the relative standard deviation (RSD) being within 2.5% for both ions. Copper, instead, gave an ASV response that, in most experimental conditions, overlapped with that of bismuth. This circumstance made the determination of copper at the BiFμE difficult. Since the latter element could be detected reliably at the uncoated carbon microdisk electrode (CμE), both BiFμE and CμE were employed, respectively, for the determination of lead and copper ions in drinking water, wine, and tomato sauce.

Analytical Letters, 37(5), 995–1011, 2004

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SUPERHEATED WATER CHROMATOGRAPHY: A BRIEF REVIEW OF AN EMERGING TECHNIQUE by Jason W. Coym and John G. Dorsey, Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, USA

ABSTRACT: The use of superheated water as a reversed‐phase mobile phase has been gaining acceptance over the past few years. There have been several recent publications on the properties of superheated water, its utility as a mobile phase, and the instrumental considerations required for its use. Because of its low cost and toxicity, the use of pure water has several advantages, particularly in the field of “green chemistry,” in which toxic solvents and reagents are avoided. This review will detail work performed using superheated water chromatography over the past several years.

Analytical Letters, 37(5), 1013–1023, 2004

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EFFECT OF EXHAUSTION HOOD FLOW RATE IN FLOW INJECTION COLD VAPOR AND HYDRIDE GENERATION ATOMIC ABSORPTION SPECTROMETRY by Oktay Cankur and O. Yavuz Ataman, Department of Chemistry, Middle East Technical University, Ankara, Turkey

ABSTRACT: The effect of exhaustion hood flow rate in the laboratory was investigated. It has been observed that this parameter significantly affects the analytical signal. This effect was more evident in cold vapor (CV) atomic absorption spectrometry (AAS) signal when unheated quartz T‐tube atomizer (QTA) was used as atom cell. At maximum exhaustion hood flow rate, the peak height and peak area values for Cd decreased to 36% and 35%, respectively, of those obtained under no exhaustion. When CV cell with both ends covered with quartz plates was used, exhaustion hood flow rate did not affect the analytical signal significantly. The exhaustion hood flow rate effect was less pronounced in case of heated QTA as compared to unheated QTA. In addition to exhaustion hood flow rate, the air movements around the atom cell also influenced the analytical signal and precision of the measurement.

Analytical Letters, 37(5), 1025–1034, 2004