12th General Conference of the Romanian Physical Society "TRENDS IN PHYSICS"

FOREWORD

The Romanian Physical Society (RPS) has been organizing, every year, the National Conference of Physics, since 1990, the date of society's post-war initiation. It however continues a tradition that the community of physicists managed to pursue for two decades earlier. There are important differences as comparing with the past in many respects: logistics, means, motivation of participation both of institutions and individuals, scope and aims. However from several points of view the word "continuity" has a factual support.

The main purpose of the national conference is to bring together physicists from various institutions, universities, research laboratories, colleges, and high schools, to discuss all matters referring to our profession and activity. And problems appear more and more acute in the present stage of historical development of our country.

Equally important is to watch to what extent the standard of research and education in physics correspond to the mainstream of the world science and to what extent we find the physics in Romania imbedded in .the world's civilization.

The sub-title "trends in physics" , adopted from the European general conferences, expresses exactly the desire of the organizers to have an overview of the status of research and education in physics in our country capable to constitute a frame for further steps and a signal for competent authorities in science policy - and for physicists themselves, too. From this point of view the Romanian Physical Society is the ideal institution, if not the only one, capable to engage on such a task. Specialized conferences more, or less successful, have been abundant during the last few years and they are extremely necessary. They solve punctual problems of scientific communication and cooperation. National conferences are expected to be a general real forum for physics promotion and advancement in Romania.

The present book contains the abstracts of contributions submitted to the conference. They will be catalogued by several international agencies (i.e. INIS-AIEA) and will be kept in the web page of RPS. As we have found an increase of the standard of presentation by the authors no paper was rejected, though we recognize that there are many misprints and language mistakes in many texts. The meaning and the intrinsic value of these texts are however transparent. Unfortunately the organizers did not have the means and time to make the necessary corrections; we operated in general to the printing aspect and uniformity of presentations. Regarding the content, spelling, grammar and logical flow, these remain entirely as the responsibility of the authors themselves.


Articles

Synthesis of a chitosan-based chelating resin and its application to the selective concentration and ultratrace determination of silver in environment

Abstract

A novel chelating resin using chitosan as a base material, ethylenediamine-type chitosan, has been synthesized for the first time in the present study, and applied to the collection/concentration of ultratrace amounts of silver in environmental water samples. In the present study, ultratrace amounts of silver collected on the resin were eluted and determined by ICP-MS. The resin packed in a 1 mL mini column could adsorb silver selectively and quantitatively at a flow rate of 2 mL min⁻¹ in the wide pH range from 1 to 8, and silver adsorbed on the resin could be easily recovered by passing 1 M nitric acid as an eluent into the column. High adsorption capacity for silver at pH 5, 0.37 mmol mL⁻¹ of the resin, was achieved, and t_1/2 of the adsorption is less than 5 min. The effect of chloride on the collection of silver was examined by varying chloride concentrations from 10⁻⁴ to 0.75 M; the results showed that the present resin can be used for the collection/concentration of ultratrace amounts of silver in natural waters, as well as seawater. To ensure the accuracy and the precision of the method, CASS-4 near shore seawater reference material from the NRCC has been analyzed. This is not a certified SRM for silver, but has been used for comparative silver analysis by several groups, who report very similar results to those that are reported here. The developed method using ethylenediamine-type chitosan resin gives 0.7 pg mL⁻¹ of the detection limit when 50-fold enrichment was used. The proposed method was successfully applied to the determination of silver in tap, river, and seawater samples.

Keywords: Chelating resin; Chitosan; Determination of silver; Environmental water samples; ICP-MS

Article Outline

1. Introduction

2. Experimental

2.1. Instruments

2.2. Reagents and solutions

3. Procedure

3.1. Synthesis of ethylenediamine-type chitosan resin

3.2. Mini column procedure for collection and concentration of silver

4. Results and discussion

4.1. Characteristics of the ethylenediamine-type chitosan resin

4.2. Adsorption capacity of ethylenediamine-type chitosan resin

4.3. Adsorption behavior of metal ions on ethylenediamine-type chitosan resin

4.4. Detection limit

4.5. Effect of chloride ion

4.6. Speciation of silver in water and adsorption mechanism of silver on the ethylenediamine-type chitosan resin

4.7. Determination of silver in CASS-4 nearshore seawater reference material

4.8. Determination of silver in tap, river, and seawater samples

5. Conclusion

Acknowledgements

References

Quality Traceability DependabilityWorld wide

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Chelating Sorbents in Inorganic Chemical Analysis

INTRODUCTION
Accurate analysis of various complex samples (natural and waste waters, geological, biological and industrial materials, substances of high purity), especially at trace levels, is one of the most difficult and complicatedanalytical tasks.
The rapid development of electronic instrumentation has created powerful analytical tools for trace element determination. At the same time, matrix effects (which can give erroneous results) and the extent of separation chemistry in instrumental methods have become evident.1
In the last years, the importance of separation and concentration techniques involving chelating sorbents in the trace analysis has risen substantially.
Pre-treatment of an aqueous sample by the sorption technique not only increases the ion concentration to a detectable level but also eliminates matrix effects. The use of chelating sorbents can provide a concentration factor up to several hundred folds, better separation of interferent ions, high efficiency and rate of process, and the possibility of combining with different determination methods.2¿5
A chelating sorbent essentially consists of two components: the chelate forming functional group and the polymeric matrix or the support; the properties of both components determine the features and the applications of the respective material.

[PDF] Chelating Sorbents in Inorganic Chemical Analysis

Biosorption of heavy metals by Saccharomyces cerevisiae: A review

Abstract

Heavy metal pollution has become one of the most serious environmental problems today. Biosorption, using biomaterials such as bacteria, fungi, yeast and algae, is regarded as acosteffective biotechnology for the treatment of high volume and low concentration complex wastewaters containing heavy metal(s) in the order of 1 to 100 mg/L. Among the promising biosorbents for heavy metal removal which have been researched during the past decades, Saccharomyces cerevisiae has received increasing attention due to the unique nature in spite of its mediocre capacity for metal uptake compared with other fungi. S. cerevisiae is widely used in food and beverage production, is easily cultivated using cheap media, is also a by-product in large quantity as a waste of the fermentation industry, and is easily manipulated at molecular level.

The state of the art in the field of biosorption of heavy metals by S. cerevisiae not only in China, but also worldwide, is reviewed in this paper, based on a substantial number of relevant references published recently on the background of biosorption achievements and development. Characteristics of S. cerevisiae in heavy metal biosorption are extensively discussed. The yeast can be studied in various forms for different purposes. Metal-binding capacity for various heavy metals by S. cerevisiae under different conditions is compared. Lead and uranium, for instances, could be removed from dilute solutions more effectively in comparison with other metals. The yeast biosorption largely depends on parameters such as pH, the ratio of the initial metal ion and initial biomass concentration, culture conditions, presence of various ligands and competitive metal ions in solution and to a limited extent on temperature. An assessment of the isotherm equilibrium model, as well as kinetics was performed. The mechanisms of biosorption are understood only to a limited extent. Elucidation of the mechanism of metal uptake is a real challenge in the field of biosorption. Various mechanism assumptions of metal uptake by S. cerevisiae are summarized.

Article Outline

1. Introduction

2. Advantages of S. cerevisiae as biosorbents in metal biosorption

3. Forms of S. cerevisiae in biosorption research

4. Biosorption capacity of S. cerevisiae

4.1. Metal ion uptake

4.2. Biosorption capacity

4.3. Selectivity and competitive biosorption by S. cerevisiae

4.4. Comparison with other biomaterials

5. Influential factors

5.1. Properties of metal ions in solution

5.2. Environmental conditions

5.2.1. pH

5.2.2. Temperature

5.2.3. Contact time

5.2.4. Competing ions/co-ions

5.2.5. Initial concentration of metal ions and biomass

5.2.6. Composition of cultural medium

5.2.6.1. Glucose

5.2.6.2. Other compositions of cultural medium

5.2.7. Cell age

6. Pretreatment

7. Biosorption equilibrium isotherm models and kinetics models

7.1. Equilibrium isotherm models

7.2. Kinetics of biosorption

7.3. Process of metal uptake

7.4. Kinetic models for S. cerevisiae

8. Biosorption mechanism by the cell of S. cerevisiae

8.1. Extracellular accumulation/precipitation

8.2. Cell surface sorption/precipitation

8.3. Intracellular accumulation/ precipitation

9. Instrumental tools and techniques used in metal biosorption studies

10. Discussions and future directions

10.1. Mechanism research

10.2. Application of biosorption technology

10.3. Screening of biomaterials

10.4. Hybrid technology

Acknowledgements

References

REVIEW OF HEAVY METALS

1. INTRODUCTION
In natural aquatic ecosystems, metals occur in low concentrations, normally at the nanogram to microgram per litre level. In recent times, however, the occurrence of metal contaminants' especially the heavy metals in excess of natural loads, has become a problem of increasing concern. This situation has arisen as a result of the rapid growth of population, increased urbanisation, expansion of industrial activities, exploration and exploitation of natural resources, extension of irrigation and other modern agricultural practices as well as the lack of environmental regulations.
At the global level the scientific community has investigated some of these problems and the results have been published in several reviews and books (Nriagu, 1989; Förstner and Wittmann, 1981; Salomons and Förstner, 1984). Most of the present introductory material is based on these sources.
Unlike other pollutants like petroleum hydrocarbons and litter which may visibly build up in the environment, trace metals may accumulate, unnoticed, to toxic levels. Thus problems associated with trace metal contamination were first highlighted in the industrially advanced countries because of their larger industrial discharges and especially by incidents of mercury and cadmium pollution in Sweden and Japan (Kurland et al., 1960; Nitta, 1972; Goldberg, 1976). In spite of the relatively low level of industrial activity in less developed regions such as Africa, there is nevertheless growing awareness of the need for rational management of aquatic resources including control of waste discharges into the environment. This becomes even more important in view of the expected increases in industrial and urban activities in all parts of the continent.
Existing information on various environmental problems has been reviewed by Dejoux (1988) in a monograph of pollution in African inland waters and by Phillips (1991) on a worldwide basis on tropical marine ecosystems. These publications showed that the existing information on Africa is scattered and scarce, and therefore demonstrated the need for a more precise and specific review of the occurrence of trace heavy metals in various aquatic environmental compartments in the continent.
For effective water pollution control and management there is a need for a clear understanding of the inputs (loads), distribution and fate of contaminants, including trace metals from land-based sources into aquatic ecosystems. In particular, the quantities and qualities need to be considered together with the distribution pathways and fate and the effects on biota.
The need to make an assessment of the level of heavy metal contamination in the African environment has led to the initiation of several pollution monitoring programmes and research work in various universities and scientific institutions in the region. The most relevant programmes are the Mediterranean pollution monitoring programme (MEDPOL) covering also North Africa, the West and Central Africa marine pollution and research programme (WACAF 2) and the Eastern Africa marine pollution and research programme (EAF/6).
During the last decade, there have also been considerable improvements in the sampling and analytical techniques for trace metals. These, coupled with international intercomparison exercises, have facilitated the generation of more reliable data. The present paper thus attempts to compile and analyze the available information on the occurrence of trace metals in both freshwater and marine ecosystems of Africa as a contribution towards the formulation of rational management policies for aquatic resources in the continent.
The decision to review freshwater and marine data jointly is a result of the need to have a holistic approach that could influence future control strategies.

Articles

An Extractive Spectrophotometric Method of Determination of Molybdenum(VI) Using 3-Hydroxy-2-(4-methoxyphenyl)-6-methyl-4H-chromen-4-one

Abstract
3-Hydroxy-2-(4-methoxyphenyl)-6-methyl-4H-chromen-4-one (HL) behaved as a sensitive spectrophotometric reagent for molybdenum(VI). The metal ion formed a yellow complex with the reagent in acetic acid medium. The complex was extractable into 1,2-dichloroethane and the absorbance values remained unchanged for more than one week. Spectral data showed the formation of 1 : 2 species with λ_max value at 411 nm. Beer’s law was obeyed over the concentration range of 0—2.3 ppm. The molar absorptivity and Sandell’s sensitivity were calculated to be 5.61 × 10⁴ dm³ mol⁻¹ cm⁻¹ and 0.0017 μg Mo cm⁻² respectively, at 411 nm. The effect of as many as 41 cations and 28 anions and complexing agents was studied. Out of these only Sn(II), Ce(IV), citrate, oxalate, disodium dihydrogen ethylenediaminetetraacetate, and hydrogen peroxide interfered seriously. For ten replicate determinations of 1 μg Mo cm⁻³ the standard deviation was 0.008 with a relative mean error of ±0.09%. The method is simple, selective, precise and rapid. It has been applied satisfactorily to the determination of molybdenum in steels, waters and flue dust samples.



[Image PDF (564K)] [References]

Performance and frequency of use of NAA and other techniques during the certification of two new Polish CMRs prepared by INCT

Abstract
Two new candidate reference materials of biological origin, viz. Tea Leaves (INCT-TL-1) and Mixed Polish Herbs (INCT-MPH-2), were prepared, and world-wide interlaboratory comparison involving over 100 laboratories was organised with the aim to certify these materials for the content of possibly great number of trace elements. In this paper a preliminary analysis of the contribution of various analytical techniques to the certification of the new reference materials is presented and discussed with the emphasis on the role played by neutron activation analysis (NAA). The potential significance of “very accurate methods” by radiochemical NAA in the certification process is pointed out. An attempt is made to compare the outcome of the present intercomparison with those formerly organised by INCT as well as with some earlier IAEA intercomparisons in order to demonstrate similarities, differences and trends in the use of the various analytical techniques in trace analysis as a function of time.


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SOIL GENESIS ON FELSIC ROCKS IN THE ST. FRANCOIS MOUNTAINS. I. THE ROLE OF SAPROLITE AND ITS INFLUENCE ON SOIL PROPERTIES.

Abstract
One soil profile from Taum Sauk Mountain and two soil profiles from Mudlick Mountain in the St. Francois Mountains of Southeast Missouri were investigated to determine if the soils evolved from the underlying rock unit and to characterize the role of saprolite on soil genesis. Taum Sauk Mountain is composed of rhyolite lava and ash flow of the Van East Group. The rock is quartz and orthoclase phenocrysts in an orthoclase groundmass. Mudlick Mountain consists of rock composed of orthoclase, oligoclase, and a minor amount of quartz phenocrysts in a groundmass of quartz and orthoclase. The shallow Aquic Hapludult formed on the summit of Taum Sauk Mountain shows no evidence of saprolite, whereas the two Typic Paleudalfs formed on Mudlick Mountain rest on a thick layer of saprolite. The presence of minerals in the host rock that weather more easily is largely responsible for the development of the saprolite on Mudlick Mountain. The very strongly acid Typic Paleudalfs have textures ranging from cobbly silt loam to cobbly sandy loam for the eluvial horizons, whereas the argillic and C horizons are generally fine or clayey-skeletal. The extremely acid Aquic Hapludults have a fine-silty texture. The clay mineralogy is mixed, with hydroxy-Al interlayered vermiculite and hydrous mica prominent in the eluvial horizons and kaolinite dominating the Bt and C horizons. The aluminum hydroxide potentials of soil solutions extracted from selected horizons are saturated or slightly supersaturated with respect to kaolinite. Elemental analysis demonstrates that the soil and saprolite originate from the same parent material and that elemental depletion is important to the formation of the saprolite. Iron oxides represent nearly all of the total Fe, and Fe is correlated highly with clay content. The rare earth elements are more abundant in the soil than in the host rock. The weathered thin loess capping is suggested as the source of the rare earth elements.
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Trace element geochemistry in acid rock drainage

INTRODUCTION
Acid rock drainage (ARD) has an impact upon our water, soil and plant quality and fish habitat with regard to trace elements, whether in a toxic or non-toxic, available or non-available form. Its impact will be determined by the type and amount of trace element(s) within the host medium (e.g. mineral assemblage). Prediction of trace element geochemistry is readily determined from standard analytical methods, providing that the sample medium is collected and analyzed in a manner that includes a program of Quality Assurance and Quality Control (QA/QC). The cost of trace element analyses and geochemistry prediction is relatively inexpensive when undertaken as part of an overall ARD study.

Article

Differential Pulse Polarographic Determination of Trace Amounts of Lead in Alloys and Biological Samples after Column Preconcentration Using Nitroso-S

Abstract:

A highly selective, sensitive, rapid, and economical differential pulse polarographic method has been developed for the determination of trace amounts of lead in various standard alloys and biological samples after the adsorption of its 2-nitroso-l-naphthol-4-sulfonic acid (nitroso-S)—tetradecyldimethylbenzylammonium (TDBA) chloride on microcrystalline naphthalene in the pH range of 8.0–10.5. After filtration, the solid mass is shaken with 9.0 mL of 1 M hydrochloric acid, and lead is determined by differential pulse polarography (DPP). Lead can alternatively be quantitatively adsorbed on 2-nitroso-l-naphthol-4-sulfonic acid-tetradecyldimethylbenzylammonium-naphthalene adsorbent packed in a column and determined similarly. In this case, 1.0 g of lead can be concentrated in a column from 500 mL of an aqueous sample in which its concentration is as low as 2 ng/mL. Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters, such as the pH effect, volume of aqueous phase, HCl concentration, reagent concentration, naphthalene concentration, shaking time, and the interference of a number of metal ions on the determination of lead were studied in detail to optimize the conditions for determination in standard alloys and standard biological samples.
Document Type: Research article
DOI: 10.1023/B:JANC.0000043917.37406.b3
Affiliations: 1: Department of Chemistry, Shahid Bahonar University of Kerman, Kerman, IRAN ma_taher@yahoo.com, Email: ma_taher@yahoo.com
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Recent development of the XANES spectral analysis methods for the structure characterization of metal complexes in solution.

Anal Sci. 2008;24(11):1385-92.
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Recent development of the XANES spectral analysis methods for the structure characterization of metal complexes in solution.

Kurisaki T, Matsuo S, Tóth I, Wakita H.

Department of Chemistry, Faculty of Science, Fukuoka University, Japan.Recent progress of the XANES (X-ray absorption near-edge structure) spectral analysis methods for the structure characterization of metal complexes (MC) in solution is reviewed. Typical examples showing the scheme of the apparatus for XAFS (X-ray absorption fine structure) data collection, preparation and handling of solution samples, data treatment and analysis for XANES spectra, and future of XANES spectroscopy are presented. Detailed examples for the apparatus developed for laboratory scale spectrometers for XANES together with a combined spectral analyses using multi scattering method (MS) and molecular orbital (MO) calculation are discussed.

PMID: 18997363 [PubMed]

Micro-channel chemiluminescence analysis using a peroxyoxalate reaction that works through liquid-liquid interface collapse under laminar-flow conditi

Anal Sci. 2008;24(11):1393-8.
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Micro-channel chemiluminescence analysis using a peroxyoxalate reaction that works through liquid-liquid interface collapse under laminar-flow conditions.

Tsukagoshi K, Hattori Y, Hayashi T, Nakajima R, Yamashita K, Maeda H.

Department of Chemical Engineering and Materials Science, Faculty of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan. ktsukago@mail.doshisha.ac.jpAn oxalate reagent-hydrogen peroxide-fluorescent compound chemiluminescence reaction, i.e., peroxyoxalate chemiluminescence, was introduced into micro-channel chemiluminescence analysis (MCCLA) to establish the concept of MCCLA through the direct observation of fluorescence and chemiluminescence using a fluorescence microscope-CCD camera and a microscope-CCD camera. It was confirmed from visual data that chemiluminescence in the MCCLA generated through the liquid-liquid interface collapsed during the course of molecular diffusion in the micro-channel. In addition, the visual data of chemiluminescence were transformed to line drawings on a computer to obtain chemiluminescence profiles. The chemiluminescence profiles were examined in detail at various flow rates and detection points; the relationship between the residence times and the chemiluminescence peak heights, or areas in the profiles, was easily represented as one smoothly changing reaction curve. Furthermore, the fluorescent compounds were detected with high sensitivity and good reproducibility in MCCLA by turning the syringe pumps on and off to produce determinable chemiluminescence signals; a photomultiplier tube was used as a detector. The chemiluminescence intensities in the signals of erythrosine, rhodamine B, Rose Bengal, fluorescein isothiocyanate, and eosin Y were examined; their intensities increased in this order, and eosin Y responded over the range of 1 x 10(-9) - 1 x 10(-6) M with a detection limit of 1 x 10(-9) M (S/N = 3). Introducing of the peroxyoxalate chemiluminescence reaction into MCCLA can extend the analysis system to the analysis of various types of sample and applications incorporating fluorescence labeling techniques.

Biphasic electrospray ionization for the study of interfacial complexes.

Anal Sci. 2008;24(11):1399-404.
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Biphasic electrospray ionization for the study of interfacial complexes.

Prudent M, Méndez MA, Girault HH.

Laboratoire d'Electrochimie Physique et Analytique, Ecole Polytechnique Fédérale de Lausanne.Biphasic electrospray ionization (BESI) mass spectrometry is achieved by using a dual-channel microsprayer, where channels filled with different immiscible phases meet at the Taylor cone. Two types of interfacial complexation reactions have been studied: the interfacial complexation of aqueous lead ions by thioether crown molecules, and the interfacial complexation of an aqueous dipeptide by dibenzo-18-crown-6 as ionophore. The mass spectra also give valuable information on the stoichiometry of the complexation reaction.

PMID: 18997365 [PubMed]

Bioluminescent indicators for Ca2+ based on split Renilla luciferase complementation in living cells.

Anal Sci. 2008;24(11):1405-8.
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Bioluminescent indicators for Ca2+ based on split Renilla luciferase complementation in living cells.

Kaihara A, Umezawa Y, Furukawa T.

Department of Bio-Informational Pharmacology, Medical Research Institute, Tokyo Medical and Dental University, Chiyoda, Tokyo 101-0062, Japan. kaihara.bip@mri.tmd.ac.jpGenetically encoded bioluminescent indicators for intracellular Ca2+ are described here with CaM-M13 interaction-induced complementation of split Renilla luciferase. The Ca2+-induced interaction between CaM and M13 leads to complementation of the N- and C-terminal halves of split Renilla luciferase in living cells. This intramolecular interaction results in the spontaneous and simultaneous emission of bioluminescence split Renilla luciferase. This is how intracellular Ca2+ is illuminated with the intramolecular complementation of split Renilla luciferase. The Ca2+-dependent spontaneous and simultaneous emission of bioluminescence promises to reveal Ca2+ dynamics in living cells, and also in vivo using the present indicators.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18997366 [PubMed - indexed for MEDLINE]

Polymeric membrane sensors for the selective determination of dextromethorphan in pharmaceutical preparations.

Anal Sci. 2008;24(11):1409-14.
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Polymeric membrane sensors for the selective determination of dextromethorphan in pharmaceutical preparations.

El-Naby EH.

Narcotic Department, National Center for Social and Criminal Research, P. O. Zamalek Post, 11561, Cairo, Egypt. emanhasab@gmail.comThe construction and electrochemical response characteristics of poly(vinyl chloride) matrix ion-selective electrodes (ISEs) for dextromethorphan (DXM) hydrobromide are described. The membranes incorporate ion-association complexes of DXM with reineckate salt {[Cr(NH3)2(SCN)4]NH4} or phosphomolybdic acid [H3(PMo12O40)], as electroactive materials and dioctylphthalate or dibutylsebacate as a plasticizing solvent mediator. The sensors display a fast, stable and linear response with slopes of 54.4 to 59.5 mV/decade at pH 2.5-6.5 and a detection limit of 1.0 x 10(-6) M. Moreover, the sensors exhibit very good selectivity for DXM over opiate alkaloids, as well as organic and inorganic cations. The sensors proved to be useful for the determination of 5.0 x 10(-5)-1.0 x 10(-3) M DXM hydrobromide in pure as well as in dosage forms by direct potentiometry and standard addition methods. Determination of 5.0 x 10(-4) M DXM using the standard addition method and a sensor based on phosphomolybdate and dioctylphthalate shows an average recovery of 99.8% and a relative standard deviation (RSD) of 0.4%.

Publication Types:
Evaluation Studies

PMID: 18997367 [PubMed - indexed for MEDLINE]

Application of polyammonium cations to enzyme-immobilized electrode: application as enzyme stabilizer for bilirubin oxidase.

Anal Sci. 2008;24(11):1421-4.
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Application of polyammonium cations to enzyme-immobilized electrode: application as enzyme stabilizer for bilirubin oxidase.

Katano H, Tatsumi H, Hibi T, Ikeda T, Tsukatani T.

Department of Bioscience, Fukui Prefectural University, Japan. hajime@fpu.ac.jpBilirubin oxidase was stored in the solutions containing polyammonium salts for a given time at 30 degrees C, and the activity was assayed. The enzyme catalyzes the reaction: 4[Fe(CN)6]4- + 4H+ + O2 --> 4[Fe(CN)6]3- + 2H2O, and the activity can be measured by the absorbance at the wavelength for the absorption maxima of [Fe(CN)6)]3-. The results show that polyammonium cations comprising quaternary ammonium in the main chain and hydrophilic groups, such as hydroxyl and amide groups, stabilize the enzyme in solution. These polyammonium cations may act like a protective colloid. The membrane-covered electrode containing the polyammonium cations, the enzyme, and [Fe(CN)6]4-/3- in the internal solution phase was constructed. The electrode gave a well-defined current-potential curve with a steady state limiting current due to the polycation-[Fe(CN)6]4-/3- complex-mediated bioelectrocatalytic current for the reduction of O2. The time-dependent decrease of the limiting current indicates again the stabilizing effect of the polyammonium cations on the enzyme.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18997369 [PubMed - indexed for MEDLINE]

An amperometric glucose biosensor based on titania sol-gel/Prussian Blue composite film.

Anal Sci. 2008;24(11):1425-30.
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An amperometric glucose biosensor based on titania sol-gel/Prussian Blue composite film.

Liang R, Jiang J, Qiu J.

Department of Chemistry, Nanchang University, Nanchang 330031, China. rpliang@ncu.edu.cnAn improved amperometric glucose biosensor was constructed by immobilizing glucose oxidase (GOD) in a titania sol-gel film, which was prepared by a vapor deposition method, on a Prussian Blue (PB)-modified electrode. The method combined the merits of immobilizing biomolecules in the titania sol-gel film by vapor deposition method and the synergic catalysis effects of PB and GOD molecules. Results showed that the fabricated titania sol-gel/PB membrane possessed high surface area, good mechanical stability, and good hydrophilicity, which provided a biocompatible microenvironment for maintaining the bioactivity of the immobilized enzyme and prevented the enzyme from leaking out of the film. Therefore, the present biosensor exhibited fast response time (10 s), high sensitivity (12.74 muA cm(-2) mM(-1)), long-term operational stability, good suppression of interference, and a wide linear range from 0.02 to 15 mM with a low detection limit of 5 muM for the detection of glucose. In addition, this simple and controllable method could fabricate biosensors in batches with a very small amount of enzyme.

Publication Types:
Evaluation Studies Research Support, Non-U.S. Gov't

PMID: 18997370 [PubMed - indexed for MEDLINE]

Detection of cytochrome c at biocompatible nanostructured Au-lipid bilayer-modified electrode.

Anal Sci. 2008;24(11):1431-6.
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Detection of cytochrome c at biocompatible nanostructured Au-lipid bilayer-modified electrode.

Liu Y, Wei W.

State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China.The present work describes the dectection of cytochrome c (cyt c) at biocompatible aurum (Au) nanoparticle-structured supported bilayer lipid membrane (sBLM) modified with anionic sites. Au nanoparticles were directly deposited through sBLM modified with lauric acid (LA) to build a hybrid device of nanoscale electrode array via potential cycling in 10 mM HAuCl4 solution containing 0.1 M KCl. The properties of Au nanoparticle-doped sBLM composite were then characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Results indicated that Au nanoparticles grew in voids of the sBLM with size around 20 - 30 nm. With SWV, after optimization, the results of the experiments indicate that the currents of cyt c were linear functions of its concentrations over the range from 1.0 x 10(-7) to 3.2 x 10(-6) M and the limit of detection (LOD, S/N = 3) was 5 x 10(-8) M. The influences of several common base pairs, amino acids and metal ions on determination of cyt c via this Au nanoparticle-doped sBLM composite were relatively low in experiments, suggesting the excellent biocompatibility of this detection method.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18997371 [PubMed - indexed for MEDLINE]

Electrochemical and spectroscopic investigations of protonated ferrocene-DNA intercalation.

Anal Sci. 2008;24(11):1437-41.
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Electrochemical and spectroscopic investigations of protonated ferrocene-DNA intercalation.

Shah A, Qureshi R, Janjua NK, Haque S, Ahmad S.

Department of Chemistry, Quaid-i-Azam University, 45320 Islamabad, Pakistan. afzal_toru@yahoo.comThe interaction of protonated ferrocene (PF) with chicken blood DNA (CB-DNA) has been investigated in vitro by cyclic voltammetry (CV) and UV-Vis spectroscopy as well as viscosity measurements under stomach pH and body temperature. The peak potentials shift in CV, hyperchromism in UV absorption titration, an increase in the viscosity of DNA and the results of the effect of ionic strength on the binding constant strongly support the intercalation of PF into the DNA double helix. The diffusion coefficients of PF in the presence and absence of DNA were 9.54 x 10(-11) and 1.34 x 10(-10) m2/s, respectively. The binding constant of the PF-DNA complex and the number of binding sites on a DNA molecule were calculated as being 3.07 x 10(2) M(-1) and 2.96, with the help of the Scatchard equation. An expression by Carter et al. was used for determining the binding site size (0.17 bp). The binding constant was also determined by UV absorption titration.

Publication Types:
Research Support, Non-U.S. Gov't

PMID: 18997372 [PubMed - indexed for MEDLINE]