bluuebunny/crossref_metadata_2025 huggingface dataset:
Anodic Oxidation and Amperometric Sensing of Hydrazine at a Glassy Carbon Electrode Modified with Cobalt (II) Phthalocyanine–cobalt (II) Tetraphenylporphyrin (CoPc- (CoTPP)4) Supramolecular Complex
Authors: Ozoemena Kenneth I.
Published: October 2008

This paper describes the electrocatalytic behaviour of a glassy carbon electrode (GCE)modified with cobalt(II)phthalocyanine (CoPc) complex peripherally tetrasubstituted withcobalt(II)tetraphenylporphyrin (CoTPP) complexes via ether linkages (i.e., CoPc-(CoTPP)4). Thefeatures of the immobilised pentamer were interrogated with cyclic voltammetry andelectrochemical impedance spectroscopy (EIS) using [Fe(CN)6]3-/4- as redox probe revealedenhanced electron transfer properties with kapp ≈ 18 x 10-6 cms-1 compared to that of the bareGCE (4.7 x 10-6 cms-1). The viability of this supramolecular complex as a redox mediator for theanodic oxidation and sensitive amperometric determination of hydrazine in alkaline conditions isdescribed. The electrocatalytic oxidation of hydrazine by GCE-CoPc-(CoTPP)4 was characterisedwith satisfactory catalytic current response with low non-Faradaic current (ca. 30 times lowerthan the bare GCE) and at much lower oxidation potential (ca. 300 mV lower than the bareGCE). A mechanism for the studied electrocatalytic reaction was proposed based on thespectrophotometric evidence that revealed the major involvement of the Co(III)/Co(II) redox coupleof the central CoPc species rather than the CoTPP component of the pentamer. Rate constant forthe anodic oxidation of hydrazine was estimated from chronoamperometry as ~ 3x103 M-1s-1. Theproposed amperometric sensor displayed excellent charateristics towards the determination ofhydrazine in 0.2 M NaOH ; such as low overpotentials ( 100 mV vs Ag|AgCl), very fastamperometric response time (1 s), linear concentration range of up to 230 μM, with micromolardetection limit, high sensitivity and stability.
A New Composition for Co(II)-porphyrin-based Membranes Used in Thiocyanate-selective Electrodes
Authors: Vlascici Dana , Fagadar-Cosma Eugenia , Bizerea-Spiridon Otilia
Published: October 2008

In the present paper, the potentiometric response characteristics of ametalloporphyrin-based electrode in o-nitrophenyloctylether (o-NPOE) plasticizedpolyvinyl chloride (PVC) membrane are presented for a set of monovalent anions. Asmembrane ionophore, 5,10,15,20-tetrakis-(4-methoxyphenyl)-porphyrin-Co(II)(CoTMeOPP) was used. To establish the optimum composition of the membrane, differentmolar percents of cationic derivative (mol.% relative to ionophore) were used. Electrodesformulated with membranes containing 1 wt.% ionophore, 66 wt.% o-NPOE, 33 wt.% PVC(plasticizer: PVC = 2:1) and the lipophilic cationic derivative (35 mol%) are shown toexhibit high selectivity for thiocyanate with a near-Nernstian slope in the workingconcentration range of 1.0×10−1–1.0×10−5 M, with a good stability in time.
Uses of Dendrimers for DNA Microarrays
Authors: Caminade Anne-Marie , Padié Clément , Laurent Régis , Maraval Alexandrine , Majoral Jean-Pierre
Published: October 2008

Biosensors such as DNA microarrays and microchips are gaining an increasingimportance in medicinal, forensic, and environmental analyses. Such devices are based onthe detection of supramolecular interactions called hybridizations that occur betweencomplementary oligonucleotides, one linked to a solid surface (the probe), and the other oneto be analyzed (the target). This paper focuses on the improvements that hyperbranched andperfectly defined nanomolecules called dendrimers can provide to this methodology. Twomain uses of dendrimers for such purpose have been described up to now; either thedendrimer is used as linker between the solid surface and the probe oligonucleotide, or thedendrimer is used as a multilabeled entity linked to the target oligonucleotide. In the firstcase the dendrimer generally induces a higher loading of probes and an easier hybridization,due to moving away the solid phase. In the second case the high number of localized labels(generally fluorescent) induces an increased sensitivity, allowing the detection of smallquantities of biological entities.
Synthesis of a Molecularly Imprinted Polymer for Dioxin
Authors: Malitesta Cosimino , Picca Rosaria Anna , Ciccarella Giuseppe , Sgobba Vito , Brattoli Magda
Published: October 2008

A molecularly imprinted polymer for recognising selectively 2,3,7,8-tetrachlorodibenzodioxin (TCDD) was made by a new non-covalent method employing a“dummy” template. The proposed way represents a simplification of a synthetic schemeproposed by Lübke et al.[1] for covalent imprinting. Comparison of extraction yields of thenovel polymer, a non imprinted polymer and an imprinting polymer, prepared by theoriginal procedure demonstrates the binding capacity of the proposed polymer, which is inprinciple applicable to solid phase extraction (SPE) of dioxin.
Biosensing with Luminescent Semiconductor Quantum Dots
Authors: Sapsford Kim E. , Pons Thomas , Medintz Igor L. , Mattoussi Hedi
Published: October 2008

Luminescent semiconductor nanocrystals or quantum dots (QDs) are a recentlydeveloped class of nanomaterial whose unique photophysical properties are helping tocreate a new generation of robust fluorescent biosensors. QD properties of interest forbiosensing include high quantum yields, broad absorption spectra coupled to narrow sizetunablephotoluminescent emissions and exceptional resistance to both photobleaching andchemical degradation. In this review, we examine the progress in adapting QDs for severalpredominantly in vitro biosensing applications including use in immunoassays, asgeneralized probes, in nucleic acid detection and fluorescence resonance energy transfer(FRET) - based sensing. We also describe several important considerations when workingwith QDs mainly centered on the choice of material(s) and appropriate strategies forattaching biomolecules to the QDs.
A New Saccharides and Nnucleosides Sensor Based on Tetrathiafulvalene-anthracene Dyad with Two Boronic Acid Groups
Authors: Tan Wei , Wang Zhuo , Zhang Deqing , Zhu Daoben
Published: October 2008

A new saccharides sensor based on the TTF-anthracene dyad with two boronicacid (2) groups was designed and synthesized. This new saccharides sensor showsselectivity towards D-glucose while its analogue with one boronic acid group (1) wasreported to bind D-Fructose selectively. Moreover, reaction of compound 2 with uridineinduced even larger fluorescence enhancement under the same condition.
The Nature of Aqueous Solutions of a Cationic Calix[4]arene: A Comparative Study of Dye–Calixarene and Dye–Surfactant Interactions
Authors: Mchedlov-Petrossyan N. O. , Vilkova L. N. , Vodolazkaya N. A. , Yakubovskaya A. G. , Rodik R. V. , Boyko V. I. , Kalchenko V. I.
Published: October 2008

Among different types of calixarenes, the water–soluble ones are of especial interestbecause of their possible applications in biochemical research. In order to elucidate the natureof aqueous solutions of a cationic amphiphilic calixarene, substituted tetrapropoxycalix[4]arene bearing hydrophilic choline groups at the upper rim, we studied vis–spectroscopically the influence of the above system on the acid–base behavior of threeindicator dyes, namely, 2,4-dinitrophenol, bromophenol blue, and N,N/-dioctadecylrhodamine,at constant ionic strength of 0.05 M, maintained with NaCl addition. Simultaneously,‘apparent’ ionization constants, Kaa , of the same dyes were determined in the presence ofcommon cationic surfactant micelles. Within the concentration range from 1.0×10–5 to 0.01 M,the aforementioned water–soluble calixarene displays effects similar to those of micelles ofcetyltrimethylammonium bromide (or chloride). The shifts of the absorption and emissionbands in the visible region, as well as the alterations of the Kaa values against the ‘aqueous’ones appeared to be very similar in aqueous solutions of both calix[4]arene and cationicsurfactant. A conclusion can be made about aggregation (or association), i.e., micelleformation of the cationic calix[4]arene under study.
Tripodal Receptors for Cation and Anion Sensors
Authors: Kuswandi Bambang , N/a Nuriman , Verboom Willem , Reinhoudt David N.
Published: October 2008

This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing are emphasised, along with their potential applications in optical sensors or optodes.
Supramolecular Based Membrane Sensors
Authors: Ganjali Mohammad Reza , Norouzi Parviz , Rezapour Morteza , Faridbod Farnoush , Pourjavid Mohammad Reza
Published: October 2008

Supramolecular chemistry can be defined as a field of chemistry, which studiesthe complex multi-molecular species formed from molecular components that haverelatively simpler structures. This field has been subject to extensive research over the pastfour decades. This review discusses classification of supramolecules and their application indesign and construction of ion selective sensors.
Effect of Limited Hydrolysis on Traditional Soy Protein Concentrate
Authors: Barac Miroljub  B. , Jovanovic Snezana  T. , Stanojevic Sladjana  P. , Pesic Mirjana  B.
Published: October 2008

The influence of limited proteolysis of soy protein concentrate on proteinextractability, the composition of the extractable proteins, their emulsifying properties andsome nutritional properties were investigated. Traditional concentrate (alcohol leachedconcentrate) was hydrolyzed using trypsin and pepsin as hydrolytic agents. Significantdifferences in extractable protein composition between traditional concentrate and theirhydrolysates were observed by polyacrylamide gel electrophoresis (PAGE) and by SDSPAGE.All hydrolysates showed better extractability than the original protein concentrate,whereas significantly better emulsifying properties were noticed at modified concentratesobtained by trypsin induced hydrolysis. These improved properties are the result of twosimultaneous processes, dissociation and degradation of insoluble alcohol-induced proteinaggregates. Enzyme induced hydrolysis had no influence on trypsin-inibitor activity, andsignificantly reduced phytic acid content.
Self-Powered Wireless Sensor Networks for Remote Patient Monitoring in Hospitals
Authors: Hande Abhiman , Polk Todd , Walker William , Bhatia Dinesh
Published: October 2008

Patient vital sign monitoring within hospitals requires the use of non-invasivesensors that are hardwired to bedside monitors. This set-up is cumbersome, forcing thepatient to be confined to his hospital bed thereby not allowing him to move around freelywithin the hospital premises. This paper addresses the use of wireless sensor networks formonitoring patient vital sign data in a hospital setting. Crossbow MICAz motes have beenused to design a robust mesh network that routes patient data to a remote base station withinthe hospital premises. A hospital care giver can have access to this data at any point in timeand doesn’t have to be physically present in the patient’s room to review the readings. Thenetwork infrastructure nodes are self-powered and draw energy from overhead 34Wfluorescent lights via solar panels. The sensor nodes can be interfaced to a variety of vitalsign sensors such as electrocardiograms (ECGs), pulse-oximeters and blood pressure (BP)sensors. In order to verify a completely functioning system, a commercial BP/heart-ratemonitor (BPM) was interfaced to a wireless sensor node. The sensor node controls the BPMto initiate a reading, then collects the data and forwards it to the base station. An attractivegraphical user interface (GUI) was designed to store and display patient data on the basestation PC. The set-up was found to be extremely robust with low power consumption.
Influence of Shielding Arrangement on ECT Sensors
Authors: Olmos A. Martinez , Primicia J. Alberdi , Marron J. L. Fernandez
Published: October 2008

This paper presents a full 3D study of a shielded ECT sensor. The spatialresolution and effective sensing field are obtained by means of Finite Element Methodbased simulations and are the compared to a conventional sensor's characteristics. Aneffective improvement was found in the sensitivity in the pipe cross-section, resulting inenhanced quality of the reconstructed image. The sensing field along the axis of the sensoralso presents better behaviour for a shielded sensor.
Electronic Tongue for Qualitative Analysis of Aqueous Solutions of Salts Using Thick-film Technology and Metal Electrodes
Authors: Gil Luis , Garcia-Breijo Eduardo , Ibañez Javier , Labrador Roberto  H. , Llobet Eduard , Martínez-Máñez Ramón , Soto Juan
Published: October 2008

An electronic tongue for the qualitative analysis of aqueous solutions of salts hasbeen developed. The following set of electrodes was used: RuO2, Ag, and Cu in thick-filmtechnology and Au, Pb, Zn and Ni as small bars of the corresponding metal. The response ofthe designed “electronic tongue” was tested on a family of samples containing pure salt andcomplex mixtures. The electrodes were used as potentiometric un-specific sensors and thee.m.f. of each electrode in contact with a certain aqueous solution was used as input signalfor a PCA analysis. The study showed that the set of electrodes were capable to discriminatebetween aqueous solutions of salts basically by their different content in anions and cations(the anions SO42-, Cl-, PO4H2-, CO3H-, NO3- and cations Na+ and K+ were studied). In orderto better analyze the basis for the discrimination power shown by the electronic tongue, aquantitative analysis was also envisaged. A fair estimation of the concentrations of thedifferent ions in the solutions studied appeared to be possible using this electronic tonguedesign.Keywords:
Voltammetric Determination of Meloxicam in Pharmaceutical Formulation and Human Serum at Glassy Carbon Electrode Modified by Cysteic Acid Formed by Electrochemical Oxidation of L-cysteine
Authors: Wang Cheng Yin , Wang Zhi Xian , Guan Jun , Hu Xiao Ya
Published: October 2008

The improvement of electrochemical detection of meloxicam is presented bymodification of a glassy carbon electrode with anionic layer of cysteic acid providingelectrostatic accumulation of the analyte onto the electrode surface. The modificationformed by electrochemical oxidation of L-cysteine was performed by cycling potential incysteine solution. The anodic peak current obtained at 1.088 V (vs. Ag/AgCl) byvoltammetry was linearly dependent on the meloxicam concentration in the range of 4.3 ×10-8 ~ 8.5 × 10-6 M in the B-R buffer solution (0.04 M, pH 1.86) with a correlationcoefficient of 0.999. The detection limit (S/N = 3) is 1.5 × 10-9 M. The low-cost modifiedelectrode shows good sensitivity, selectivity and stability and has been applied to thedetermination of meloxicam in pharmaceutical formulation and spiked serum withsatisfactory results. The electrochemical reaction mechanism of meloxicam was discussed.
Biasing Voltage Dependence of Sensitivity of Electron Beam Evaporated SnO2 Thin Film CO Sensor
Authors: Durrani Sardar M. Ayub
Published: October 2008

Thin films of tin oxide were deposited by electron beam evaporation. The effectsof the sensor biasing voltage and film thickness on the CO-sensing of tin oxide thin filmswere investigated. The films were characterized using X-ray diffraction and X-rayphotoelectron spectroscopy All the films were found to be amorphous. The current-voltagecharacteristic of the sensor in air has shown that semiconductor-metal interface formsSchottky barrier. It was found that the CO-sensing properties depend on the sensor biasingvoltage and film thickness. For lower biasing voltages the sensitivity was much higher thanfor the higher voltages. It was found that the sensitivity of the films to CO increased withthe film thickness.
Trends in Flow-based Biosensing Systems for Pesticide Assessment
Authors: Prieto-Simón Beatriz , Campàs Mònica , Andreescu Silvana , Marty Jean-Louis
Published: October 2008

This review gives a survey on the state of the art of pesticide detection usingflow-based biosensing systems for sample screening. Although immunosensor systems havebeen proposed as powerful pesticide monitoring tools, this review is mainly focused onenzyme-based biosensors, as they are the most commonly employed when using a flowsystem. Among the different detection methods able to be integrated into flow-injectionanalysis (FIA) systems, the electrochemical ones will be treated in more detail, due to theirhigh sensitivity, simple sample pretreatment, easy operational procedures and real-timedetection. During the last decade, new trends have been emerging in order to increase theenzyme stability, the sensitivity and selectivity of the measurements, and to lower thedetection limits. These approaches are based on (i) the design of novel matrices for enzymeimmobilisation, (ii) new manifold configurations of the FIA system, sometimes includingminiaturisation or lab-on-chip protocols thanks to micromachining technology, (iii) the useof cholinesterase enzymes either from various commercial sources or genetically modifiedwith the aim of being more sensitive, (iv) the incorporation of other highly specificenzymes, such as organophosphate hydrolase (OPH) or parathion hydrolase (PH) and (v) thecombination of different electrochemical methods of detection. This article discusses thesenovel strategies and their advantages and limitations.
A New Overpotential — Capacitance Mechanism for H2 Electrode
Authors: Cheng K. , Ashraf Naila , Wei Glenn
Published: October 2008

The H2 electrode is commonly assumed to be a half-cell, 2 H+ 2e == H2, andexplained by the Nernst equation. We cannot assume that the H+ is easily reduced to H2 inan H2 saturated solution, and H2 becoming oxidized to H+ in a strongly acid solution againstthe equilibrium principle. How can the H2 gas is involved from a basic solution where thereis practically no H+ ions? Another equilibrium has been postulated, H2 (soln) = 2H(adsorbed on metal) = 2 H 2e. This paper reports the results of studying the H2 electrodeusing various techniques, such as adsorption, bubbling with H2, and N2, charging,discharging, and recharging, replacing the salt bridge with a conducting wire, etc. Aninteresting overpotential was observed that bubbling H2 into the solution caused a suddenchange of potential to more negative without changing the solution pH. The H2 may bereplaced by N2 to give a similar calibration curve without the overpotential. The resultscontradict the redox mechanism. When the Pt is separated by H2 coating, it cannot act as acatalyst in the solution. Our results seem to explain the H2 electrode mechanism as thecombination of its overpotential and capacitance potential. Bubbling of H2 or N2 onlyremoves interfering gases such as O2 and CO2. Since neither H2 nor N2 is involved in thepotential development, it is improper to call the H2 or N2 electrode. A term of pH / OH Ptelectrode, like the pH / OH glass electrode, is suggested.
Application of an IR Thermographic Device for the Detection of a Simulated Defect in a Pipe
Authors: Joung Ok  Jin , Kim Young  Han
Published: October 2008

An infrared (IR) temperature sensor module developed for the detection ofdefects in a metal plate is modified for defect detection in a pipe. A module giving closesensor arrangement and maintaining a constant distance between sensor and measuredobject is developed and utilized in the present modification of the IR thermographic device.The defect detection performance is experimentally investigated, and the measuredtemperature is compared with the computed temperature distribution and with a previousexperimental result. The outcome of this experiment indicates that detection of a simulateddefect is readily obtainable, and the measured temperature distribution is better for defectdetection than with the previously utilized device. The comparison of standard deviations ofdifferent sensors clearly indicates an improvement in the location of defects in this study.Also, the measured temperature distribution is comparable to the one calculated using a heatconduction equation. The device developed for defect detection here is suitable forimplementation in chemical processes, where most vessels and piping systems arecylindrical in shape.
Monitoring the Freshness of Moroccan Sardines with a Neural-Network Based Electronic Nose
Authors: Amari Aziz , El Barbri Noureddine , Llobet Eduard , El Bari Nezha , Correig Xavier , Bouchikhi Benachir
Published: October 2008

An electronic nose was developed and used as a rapid technique to classify thefreshness of sardine samples according to the number of days spent under cold storage (4 ±1°C, in air). The volatile compounds present in the headspace of weighted sardine sampleswere introduced into a sensor chamber and the response signals of the sensors wererecorded as a function of time. Commercially available gas sensors based on metal oxidesemiconductors were used and both static and dynamic features from the sensorconductance response were input to the pattern recognition engine. Data analysis wasperformed by three different pattern recognition methods such as probabilistic neuralnetworks (PNN), fuzzy ARTMAP neural networks (FANN) and support vector machines(SVM). The objective of this study was to find, among these three pattern recognitionmethods, the most suitable one for accurately identifying the days of cold storage undergoneby sardine samples. The results show that the electronic nose can monitor the freshness ofsardine samples stored at 4°C, and that the best classification and prediction are obtainedwith SVM neural network. The SVM approach shows improved classificationperformances, reducing the amount of misclassified samples down to 3.75 %.
Flow-through Bulk Optode for Spectrophotometric Determination of Thiocyanate and Its Application to Water and Saliva Analysis
Authors: García Soledad , Ortuño Joaquín A. , Sánchez-Pedreño Concepción , Albero Isabel , Fernández José
Published: October 2008

A flow-through spectrophotometric bulk optode for the flow-injectiondetermination of thiocyanate is described. As active constituents, the optode incorporatesthe lipophilized pH indicator 5-octadecanoyloxy-2-(4-nitrophenylazo)phenol andmethyltridodecyl ammonium chloride, dissolved in a plasticized poly(vinyl)chloridemembrane entrapped in a cellulose support. The optode is applied, in conjunction with theflow injection technique, to the determination of thiocyanate at pH 7.5 (TRIS/H2SO4). Thesensor is readily regenerated with a 10-2 M NaOH carrier solution. The analyticalcharacteristics of this optode with respect to thiocyanate response time, dynamicmeasurement range, reproducibility and selectivity are discussed. The proposed FI methodis applied to the determination of thiocyanate in waters from different sources and in humansaliva samples in order to distinguish between smokers and non-smokers.
Studies on the Interaction Mechanism of 1,10-Phenanthroline Cobalt(II) Complex with DNA and Preparation of Electrochemical DNA Biosensor
Authors: Niu Shuyan , Li Feng , Zhang Shusheng , Wang Long , Li Xuemei , Wang Shiying
Published: October 2008

Fluorescence spectroscopy and ultraviolet (UV) spectroscopy techniques coupled with cyclic voltammetry (CV) were used to study the interaction between salmon sperm DNA and 1,10-Phenanthroline cobalt(II) complex, [Co(phen)2(Cl)(H2O)]Cl·H2O, where phen = 1,10-phenanthroline. The interaction between [Co(phen)2(Cl)(H2O)]+ and double-strand DNA (dsDNA) was identified to be intercalative mode. An electrochemical DNA biosensor was developed by covalent immobilization of probe single-strand DNA (ssDNA) related to human immunodeficiency virus (HIV) on the activated glassy carbon electrode (GCE). With [Co(phen)2(Cl)(H2O)]+ being the novel electrochemical hybridization indicator, the selectivity of ssDNA-modified electrode was investigated and selective detection of complementary ssDNA was achieved using differential pulse voltammetry (DPV).
Recent Development in Optical Chemical Sensors Coupling with Flow Injection Analysis
Authors: Ojeda Catalina Bosch , Rojas Fuensanta Sánchez
Published: October 2008

Optical techniques for chemical analysis are well established and sensors based on thesetechniques are now attracting considerable attention because of their importance in applications suchas environmental monitoring, biomedical sensing, and industrial process control. On the other hand,flow injection analysis (FIA) is advisable for the rapid analysis of microliter volume samples and canbe interfaced directly to the chemical process. The FIA has become a widespread automatic analyticalmethod for more reasons; mainly due to the simplicity and low cost of the setups, their versatility, andease of assembling. In this paper, an overview of flow injection determinations by using opticalchemical sensors is provided, and instrumentation, sensor design, and applications are discussed. Thiswork summarizes the most relevant manuscripts from 1980 to date referred to analysis using opticalchemical sensors in FIA.
Sub-Nanoliter Spectroscopic Gas Sensor
Authors: Alfeeli Bassam , Pickrell Gary , Wang Anbo
Published: October 2008

In this work, a new type of optical fiber based chemical sensor, the sub-nanolitersample cell (SNSC) based gas sensor, is described and compared to existing sensors designsin the literature. This novel SNSC gas sensor is shown to have the capability of gasdetection with a cell volume in the sub-nanoliter range. Experimental results for variousconfigurations of the sensor design are presented which demonstrate the capabilities of theminiature gas sensor.
Gas/Liquid and Liquid/Liquid Solvent Extraction in Flow Analysis with the Chromatomembrane Cell
Authors: Moskvin Leonid N. , Simon Juergen
Published: October 2008

Since twelve years the Chromatomembrane Cell has been proposed as a new andversatile device for extraxtion procedures in the flow based analysis. In the meantime aremarkable number of papers was submitted dealing with applications of the novel methodto all the conceivable varieties of flow injection and sequential injection analysis. Thedevice supports important analytical procedures such as sampling, sample preparation, andpreconcentration each being combined with a phase transfer of the analyte. TheChromatomembrane Cell can be coupled to most of the modern detectors which workcomputer aided in the laboratories of today. Centrepiece of the cell is a block made frombiporous hydrophobic PTFE, inside which polar (in the macropores) and nonpolar (in themicropores) solvents come into a close contact with each other and might flowindependently with different flow rates. Microporous PTFE membranes prevent polarphases from their flowthrough into directions which are reserved for nonpolar fluids only.Thus, a strict control over the fluxes can be established at the analysts request. Especially,that PTFE block offers outstanding possibilities as a sampling unit for air monitoring.
Development of Multichannel Artificial Lipid-Polymer Membrane Sensor for Phytomedicine Application
Authors: Ahmad Mohd  Noor , Ismail Zhari , Chew Oon–Sim , Islam AKM  Shafiqul , Md Shakaff Ali  Yeon
Published: October 2008

Quality control of herbal medicines remain a challenging issue towardsintegrating phytomedicine into the primary health care system. As medicinal plants is acomplicated system of mixtures, a rapid and cost-effective evaluation method tocharacterize the chemical fingerprint of the plant without performing laborious samplepreparation procedure is reported. A novel research methodology based on an in-housefabricated multichannel sensor incorporating an array of artificial lipid-polymer membraneas a fingerprinting device for quality evaluation of a highly sought after herbal medicine inthe Asean Region namely Eurycoma longifolia (Tongkat Ali). The sensor array is based onthe principle of the bioelectronic tongue that mimics the human gustatory system throughthe incorporation of artificial lipid material as sensing element. The eight non-specificsensors have partially overlapping selectivity and cross-sensitivity towards the targetedanalyte. Hence, electrical potential response represented by radar plot is used to characterizeextracts from different parts of plant, age, batch-to-batch variation and mode of extraction ofE. longifolia through the obtained potentiometric fingerprint profile. Classification modelwas also developed classifying various E. longifolia extracts with the aid of chemometricpattern recognition tools namely hierarchical cluster analysis (HCA) and principalcomponent analysis (PCA). The sensor seems to be a promising analytical device for qualitycontrol based on potentiometric fingerprint analysis of phytomedicine.
Surface Science Studies of Gas Sensing Materials: SnO2
Authors: Batzill Matthias
Published: October 2008

This review is an attempt to give an overview on how surface science studies cancontribute to a fundamental understanding of metal oxide gas sensors. In here tin dioxide isused as a model system for metal oxide gas sensor materials and we review surface sciencestudies of single crystal SnO2. The composition, structure, electronic and chemicalproperties of the (110) and (101) surfaces is described. The influence of compositionalchanges as a function of the oxygen chemical potential on the electronic surface structureand the chemical properties is emphasized on the example of the (101) surface. The surfacechemical properties are discussed on the example of water adsorption. It is shown thechemical and gas sensing properties depend strongly on the surface composition.
Sensor for Injection Rate Measurements
Authors: Marcic Milan
Published: October 2008

A vast majority of the medium and high speed Diesel engines are equipped withmulti-hole injection nozzles nowadays. Inaccuracies in workmanship and changinghydraulic conditions in the nozzles result in differences in injection rates between individualinjection nozzle holes. The new deformational measuring method described in the paperallows injection rate measurement in each injection nozzle hole. The differences in injectionrates lead to uneven thermal loads of Diesel engine combustion chambers. All today knownmeasuring method, such as Bosch and Zeuch give accurate results of the injection rate indiesel single-hole nozzles. With multihole nozzles they tell us nothing about possibledifferences in injection rates between individual holes of the nozzle. At deformationalmeasuring method, the criterion of the injected fuel is expressed by the deformation ofmembrane occurring due to the collision of the pressure wave against the membrane. Thepressure wave is generated by the injection of the fuel into the measuring space. For eachhole of the nozzle the measuring device must have a measuring space of its own into whichfuel is injected as well as its measuring membrane and its own fuel outlet. Duringmeasurements procedure the measuring space must be filled with fuel to maintain anoverpressure of 5 kPa. Fuel escaping from the measuring device is conducted into thegraduated cylinders for measuring the volumetric flow through each hole of the nozzle.Themembrane deformation is assessed by strain gauges. They are glued to the membrane andforming the full Wheatstone’s bridge. We devoted special attention to the membrane shapeand temperature compensation of the strain gauges.
Recent Electrochemical and Optical Sensors in Flow-Based Analysis
Authors: Chailapakul Orawon , Ngamukot Passapol , Yoosamran Alongkorn , Siangproh Weena , Wangfuengkanagul Nattakarn
Published: October 2008

Some recent analytical sensors based on electrochemical and optical detectioncoupled with different flow techniques have been chosen in this overview. A briefdescription of fundamental concepts and applications of each flow technique, such as flowinjection analysis (FIA), sequential injection analysis (SIA), all injection analysis (AIA),batch injection analysis (BIA), multicommutated FIA (MCFIA), multisyringe FIA(MSFIA), and multipumped FIA (MPFIA) were reviewed.
Photoacoustic Spectroscopy with Quantum Cascade Lasers for Trace Gas Detection
Authors: Elia Angela , Di Franco Cinzia , Lugarà Pietro Mario , Scamarcio Gaetano
Published: October 2008

Various applications, such as pollution monitoring, toxic-gas detection, noninvasive medical diagnostics and industrial process control, require sensitive and selectivedetection of gas traces with concentrations in the parts in 109 (ppb) and sub-ppb range.The recent development of quantum-cascade lasers (QCLs) has given a new aspect toinfrared laser-based trace gas sensors. In particular, single mode distributed feedback QCLsare attractive spectroscopic sources because of their excellent properties in terms of narrowlinewidth, average power and room temperature operation. In combination with these lasersources, photoacoustic spectroscopy offers the advantage of high sensitivity and selectivity,compact sensor platform, fast time-response and user friendly operation. This paper reportsrecent developments on quantum cascade laser-based photoacoustic spectroscopy for tracegas detection. In particular, different applications of a photoacoustic trace gas sensoremploying a longitudinal resonant cell with a detection limit on the order of hundred ppb ofozone and ammonia are discussed. We also report two QC laser-based photoacousticsensors for the detection of nitric oxide, for environmental pollution monitoring andmedical diagnostics, and hexamethyldisilazane, for applications in semiconductormanufacturing process.
ZnO:Al Thin Film Gas Sensor for Detection of Ethanol Vapor
Authors: Chou Shih Min , Teoh Lay Gaik , Lai Wei Hao , Su Yen Hsun , Hon Min Hsiung
Published: October 2008

The ZnO:Al thin films were prepared by RF magnetron sputtering on Si substrateusing Pt as interdigitated electrodes. The structure was characterized by XRD and SEManalyses, and the ethanol vapor gas sensing as well as electrical properties have beeninvestigated and discussed. The gas sensing results show that the sensitivity for detecting400 ppm ethanol vapor was ~20 at an operating temperature of 250°C. The high sensitivity,fast recovery, and reliability suggest that ZnO:Al thin film prepared by RF magnetronsputtering can be used for ethanol vapor gas sensing.
Application of Electronic Noses for Disease Diagnosis and Food Spoilage Detection
Authors: Casalinuovo Ida A. , Di Pierro Donato , Coletta Massimiliano , Di Francesco Paolo
Published: October 2008

Over the last twenty years, newly developed chemical sensor systems (socalled“electronic noses") have odour analyses made possible. This paper describes theapplications of these systems for microbial detection in different fields such as medicineand the food industry, where fast detection methods are essential for appropriatemanagement of health care. Several groups have employed different electronic noses forclassification and quantification of bacteria and fungi to obtain accurate medicaldiagnosis and food quality control. So far, detection and identification of bacterial andfungal volatiles have been achieved by use of e-noses offering different correctclassification percentages. The present review includes examples of bacterial and fungalspecies producing volatile compounds and correlated to infectious diseases or fooddeterioration. The results suggest the possibility of using this new technology both inmedical diagnostics and in food control management.
Volatile Organic Compound Optical Fiber Sensors: A Review
Authors: Elosua Cesar , Matias Ignacio R. , Bariain Candido , Arregui Francisco J.
Published: October 2008

Volatile organic compound (VOC) detection is a topic of growing interest withapplications in diverse fields, ranging from environmental uses to the food or chemicalindustries. Optical fiber VOC sensors offering new and interesting properties whichovercame some of the inconveniences found on traditional gas sensors appeared over twodecades ago. Thanks to its minimum invasive nature and the advantages that optical fiberoffers such as light weight, passive nature, low attenuation and the possibility ofmultiplexing, among others, these sensors are a real alternative to electronic ones inelectrically noisy environments where electronic sensors cannot operate correctly. In thepresent work, a classification of these devices has been made according to the sensingmechanism and taking also into account the sensing materials or the different methods offabrication. In addition, some solutions already implemented for the detection of VOCsusing optical fiber sensors will be described with detail.
Flow Injection Analysis Coupled with Carbon Electrodes as the Tool for Analysis of Naphthoquinones with Respect to Their Content and Functions in Biological Samples
Authors: Babula Petr , Huska Dalibor , Hanustiak Pavel , Baloun Jiri , Krizkova Sona , Adam Vojtech , Hubalek Jaromir , Havel Ladislav , Zemlicka Milan , Horna Ales , Beklova Miroslava , Kizek Rene
Published: October 2008

Naphthoquinones are one of the groups of secondary metabolites widespread innature, where they mostly appear as chromatic pigments. They embody broad-range ofbiological actions from phytotoxic to fungicidal. An anticancer effect of naphthoquinonesstimulates an interest in determination and characterization of single derivatives of 1,2- and1,4-quinones in biological samples. The main aim of this work was to suggest a techniquesuitable to determine lawsone, juglone and/or plumbagin in biological samples and to studyof their influence on BY-2 tobacco cells. The BY-2 tobacco cells were cultivated in thepresence of the naphthoquinones of interest (500 μg.l-1) for 24 h and then the morphologicalchanges were observed. We found out that naphthoquinones triggered the programmed celldeath at BY-2 cells, which can be confirmed by the apoptotic bodies in nucleus. After thatwe suggested and optimized different electrochemical techniques such differential pulsevoltammetry (DPV) coupled with hanging mercury drop (HMDE) and carbon pasteelectrode, micro flow device coupled with carbon screen printed electrodes and flowinjection analysis coupled with Coulochem III detector to determine them. The detectionlimits of naphthoquinones of interest were expressed as 3S/N and varied from units tohundreds of ng per millilitres according to methods used. Moreover, we utilized DPVcoupled with HMDE and micro flow device to determine content of juglone in leavesPersian walnut (Juglans regia). We determined that the leaves contained juglone tenths of gper 100 g of fresh weight. The results obtained show the convincing possibilities of using ofthese methods in analysis of plant secondary metabolites.
Electrochemical Sensors for Detection of Acetylsalicylic Acid
Authors: Supalkova Veronika , Petrek Jiri , Havel Ladislav , Krizkova Sona , Petrlova Jitka , Adam Vojtech , Potesil David , Babula Petr , Beklova Miroslava , Horna Ales , Kizek Rene
Published: October 2008

Acetylsalicylic acid (AcSA), or aspirin, was introduced in the late 1890s and hasbeen used to treat a variety of inflammatory conditions. The aim of this work was to suggestelectrochemical sensor for acetylsalicylic detection. Primarily, we utilized square wavevoltammetry (SWV) using both carbon paste electrode (CPE) and of graphite pencilelectrode (GPE) as working ones to indirect determination of AcSA. The principle ofindirect determination of AcSA bases in its hydrolysis on salicylic acid (SA), which isconsequently detected. Thus, we optimized both determination of SA and conditions forAcSA hydrolysis and found out that the most suitable frequency, amplitude, step potentialand the composition and pH of the supporting electrolyte for the determination of SA was260 Hz, 50 mV, 10 mV and Britton-Robinson buffer (pH 1.81), respectively. The detectionlimit (S/N = 3) of the SA was 1.3 ng/ml. After that, we aimed on indirect determination ofAcSA by SWV CPE. We tested the influence of pH of Britton-Robinson buffer andtemperature on yield of hydrolysis, and found out that 100% hydrolysis of AcSA wasreached after 80 minutes at pH 1.81 and 90°C. The method for indirect determination ofAcSA has been utilized to analyse pharmaceutical drug. The determined amount of AcSA in the pharmaceutical drug was in good agreement with the declared amounts. Moreover, weused GPE for determination of AcSA in a pharmaceutical drug. Base of the results obtainedfrom stationary electrochemical instrument we used flow injection analysis withelectrochemical detection to determine of salicylates (SA, AcSA, thiosalicylic acid, 3,5-dinitrosalicylic acid and 5-sulfosalicylic acid – SuSA). We found out that we are able todetermine all of detected salicylates directly without any pre-treatment, hydrolysis and so onat units of femtomoles per injection (5 μl).
New Hydrodynamic Electrochemical Arrangement for Cadmium Ions Detection Using Thick-Film Chemical Sensor Electrodes
Authors: Prasek Jan , Adamek Martin , Hubalek Jaromir , Adam Vojtech , Trnkova Libuse , Kizek Rene
Published: October 2008

Miniaturization and integration of chemical devices into modules that aredimensionally comparable with electronic chips (Lab on Chip) is nowadays developingworldwide. The aim of our work was to suggest and optimize the best conditions forfabrication of TFT sensor due to its sensitivity and low experimental deviations. Newelectrochemical analytical device was developed to ensure certain known mass transport toelectrodes, which is the most limiting process that influencing the response quality of thesensor. The device consists from rotating conic vessel for measured sample and stick-inthick-film sensor. The sensors responses were tested under trace analysis of cadmium.Measurements were done also with the others electrochemical arrangements to comparewith the new one. The sensor output current response dependence on the liquid velocity andgeometrical arrangement within using standard electrochemical couple of potassiumferrocyanide-ferricyanide is presented. We found out that the new device with controlledflow of electrolyte to sensor worked properly and gave satisfactory results.
Modelling of Amperometric Biosensors in the Case of Substrate Inhibition
Authors: Kulys Juozas , Baronas Romas
Published: October 2008

The response of an amperometric biosensor at mixed enzyme kinetics anddiffusion limitations was modelled digitally in the case of substrate inhibition. Digitalsimulations were carried out using a finite difference technique. Calculations showedcomplex kinetics of biosensor response. At low enzyme activity and substrate concentration(S0), the response of the sensor looks like it is limited by a simple substrate diffusion. Atsubstrate concentration comparable to the Michaelis-Menten constant (KM), the responsechange shows a maximal value. A sharp response change was indicated at high enzymeactivity and high (4.9 > S0/KM > 4.5) substrate concentration. This was explained by multiconcentrationof substrate generation inside the enzyme layer. This conclusion wasconfirmed by the analytical solution of the simplified biosensor model with externaldiffusion limitation at steady-state conditions. The complex kinetics of response changeproduces different calibration graphs for biosensor response at transition and steady state.
Voltammetric Determination of Dopamine in Human Serum with Amphiphilic Chitosan Modified Glassy Carbon Electrode
Authors: Wang Cheng Yin , Wang Zhi Xian , Zhu Ai Ping , Hu Xiao Ya
Published: October 2008

An improvement of selectivity for electrochemical detection of dopamine (DA)with differential pulse voltammetry is achieved by covalently modifying a glassy carbonelectrode (GCE) with O-carboxymethylchitosan (OCMCS). The amphiphilic chitosanprovides electrostatic accumulation of DA onto the electrode surface. In a phosphate buffersolution (pH 6.0), a pair of well-defined reversible redox waves of DA was observed at theOCMCS/GCE with a δEp of 52 mV. The anodic peak current obtained from thedifferential pulse voltammetry of dopamine was linearly dependent on its concentration inthe range of 6.0 × 10-8 to 7.0 × 10-6 M, with a correlation coefficient of 0.998. Thedetection limit (S/N = 3) was found to be 1.5 × 10-9 M. The modified electrode had beenapplied to the determination of DA in human serum samples with satisfactory results.
Tracking Dynamic Source Direction with a Novel Stationary Electronic Nose System
Authors: Cai Jie , Levy David  C.
Published: October 2008

Arrays of chemical sensors, usually called electronic noses (ENose), are widelyused in industry for classifying and identifying odours. They may also be used to locate theposition and detect the direction of an emission source. Usually this task is performed by anENose cooperating with a mobile vehicle, but when a source is instantaneous, or thesurrounding terrain is hard for vehicles to traverse, an alternative approach is needed. Thus athree-step method for a stationary ENose with a novel structure to detect the direction of adynamic source is presented in this paper. The method uses the ratio of measuredconcentration from different sensors (Cn /C1 where n=2, 4) as a discriminator. In addition,this method could easily be adapted to robotics as an optimized algorithm for path trackingto a source location. The paper presents the results of a simulation of the method.
Design of a Flow-through Polarographic Sensor Based on Metal Films for Determining N-nitrosodiethanolamine Levels in Rabbit Biological Fluids
Authors: Wang Lai-Hao , Hsia Hung-Chang , Lan Yuan-Zhi
Published: October 2008

The construction and characterization of a flow-through polarographic detectorfor catalyzing the electroreduction of N-nitrosodiethanolamine (NDELA), is discussed. Theflow-through cell is equipped with a gold wire electrode (a thin mercury film deposited on agold substance). The response is evaluated with respect to substance diameter, length,concentration of modifying film, operating potential, supporting electrolyte and pH, andflow rate in the DC mode. The system allows the determination of N-nitrosodiethanolaminein rabbit biological fluids with relatively inexpensive equipment.
Wet Chemical Synthesis and Screening of Thick Porous Oxide Films for Resistive Gas Sensing Applications
Authors: Frenzer Gerald , Frantzen Andreas , Sanders Daniel , Simon Ulrich , Maier Wilhelm F.
Published: October 2008

A method of wet chemical synthesis suitable for high throughput and combinatorial applications has been developed for the synthesis of porous resistive thick-film gas sensors. This method is based on the robot-controlled application of unstable metal oxide suspensions on an array of 64 inter-digital electrodes positioned on an Al2O3 substrate. SnO2, WO3, ZrO2, TiO2, CeO2, In2O3 and Bi2O3 were chosen as base oxides, and were optimised by doping or mixed oxide formation. The parallel synthesis of mixed oxide sensors is illustrated by representative examples. The electrical characteristics and the sensor performance of the films were measured by high-throughput impedance spectroscopy while supplying various test gases (H2, CO, NO, NO2, propene). Data collection, data mining techniques applied and the best potential sensor materials discovered are presented.