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Sensors, Volume 6, Issue 11 (November 2006), Pages 1428-1720

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Research

Jump to: Review

Open AccessArticle Flow Injection Analysis Coupled with Carbon Electrodes as the Tool for Analysis of Naphthoquinones with Respect to Their Content and Functions in Biological Samples
Sensors 2006, 6(11), 1466-1482; doi:10.3390/s6111466
Received: 16 October 2006 / Accepted: 27 October 2006 / Published: 6 November 2006
Cited by 26 | PDF Full-text (145 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessArticle Electrochemical Sensors for Detection of Acetylsalicylic Acid
Sensors 2006, 6(11), 1483-1497; doi:10.3390/s6111483
Received: 16 October 2006 / Accepted: 27 November 2006 / Published: 6 November 2006
Cited by 31 | PDF Full-text (240 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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). Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessArticle New Hydrodynamic Electrochemical Arrangement for Cadmium Ions Detection Using Thick-Film Chemical Sensor Electrodes
Sensors 2006, 6(11), 1498-1512; doi:10.3390/s6111498
Received: 16 October 2006 / Accepted: 27 October 2006 / Published: 6 November 2006
Cited by 32 | PDF Full-text (175 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessArticle Modelling of Amperometric Biosensors in the Case of Substrate Inhibition
Sensors 2006, 6(11), 1513-1522; doi:10.3390/s6111513
Received: 15 September 2006 / Accepted: 6 November 2006 / Published: 7 November 2006
Cited by 10 | PDF Full-text (122 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle Voltammetric Determination of Dopamine in Human Serum with Amphiphilic Chitosan Modified Glassy Carbon Electrode
Sensors 2006, 6(11), 1523-1536; doi:10.3390/s6111523
Received: 14 August 2006 / Accepted: 3 November 2006 / Published: 8 November 2006
Cited by 12 | PDF Full-text (137 KB) | HTML Full-text | XML Full-text
Abstract
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), [...] Read more.
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. Full article
(This article belongs to the Special Issue Amperometric Sensors and Techniques for Neurochemical Monitoring)
Open AccessArticle Tracking Dynamic Source Direction with a Novel Stationary Electronic Nose System
Sensors 2006, 6(11), 1537-1554; doi:10.3390/s6111537
Received: 15 September 2006 / Accepted: 6 November 2006 / Published: 8 November 2006
Cited by 5 | PDF Full-text (205 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
Open AccessArticle Design of a Flow-through Polarographic Sensor Based on Metal Films for Determining N-nitrosodiethanolamine Levels in Rabbit Biological Fluids
Sensors 2006, 6(11), 1555-1567; doi:10.3390/s6111555
Received: 25 February 2006 / Revised: 5 October 2006 / Accepted: 10 November 2006 / Published: 11 November 2006
Cited by 6 | PDF Full-text (596 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Sensors in Flow Analysis)
Open AccessArticle Wet Chemical Synthesis and Screening of Thick Porous Oxide Films for Resistive Gas Sensing Applications
Sensors 2006, 6(11), 1568-1586; doi:10.3390/s6111568
Received: 26 September 2006 / Accepted: 14 November 2006 / Published: 15 November 2006
Cited by 14 | PDF Full-text (451 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessArticle Characterizing Clutter in the Context of Detecting Weak Gaseous Plumes in Hyperspectral Imagery
Sensors 2006, 6(11), 1587-1615; doi:10.3390/s6111587
Received: 29 September 2006 / Accepted: 17 November 2006 / Published: 23 November 2006
Cited by 9 | PDF Full-text (1204 KB) | HTML Full-text | XML Full-text
Abstract
Weak gaseous plume detection in hyperspectral imagery requires thatbackground clutter consisting of a mixture of components such as water, grass, and asphaltbe well characterized. The appropriate characterization depends on analysis goals.Although we almost never see clutter as a single-component multivariate Gaussian(SCMG), alternatives [...] Read more.
Weak gaseous plume detection in hyperspectral imagery requires thatbackground clutter consisting of a mixture of components such as water, grass, and asphaltbe well characterized. The appropriate characterization depends on analysis goals.Although we almost never see clutter as a single-component multivariate Gaussian(SCMG), alternatives such as various mixture distributions that have been proposed mightnot be necessary for modeling clutter in the context of plume detection when the chemicaltargets that could be present are known at least approximately. Our goal is to show to whatextent the generalized least squares (GLS) approach applied to real data to look for evidenceof known chemical targets leads to chemical concentration estimates and to chemicalprobability estimates (arising from repeated application of the GLS approach) that aresimilar to corresponding estimates arising from simulated SCMG data. In some cases,approximations to decision thresholds or confidence estimates based on assuming the clutterhas a SCMG distribution will not be sufficiently accurate. Therefore, we also describe astrategy that uses a scene-specific reference distribution to estimate decision thresholds forplume detection and associated confidence measures. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessArticle A Portable Sensing System for Electronic Tongue Operations
Sensors 2006, 6(11), 1679-1696; doi:10.3390/s6111679
Received: 22 September 2006 / Accepted: 17 November 2006 / Published: 23 November 2006
Cited by 11 | PDF Full-text (227 KB) | HTML Full-text | XML Full-text
Abstract
A portable, low cost sensing system is described which interfaces to an electronictongue sensor. The sensor used is a voltammetric sensor which monitors electrochemicalreactions that occur in solutions. The sensor is able to test a range of liquids with differentelectrochemical properties without [...] Read more.
A portable, low cost sensing system is described which interfaces to an electronictongue sensor. The sensor used is a voltammetric sensor which monitors electrochemicalreactions that occur in solutions. The sensor is able to test a range of liquids with differentelectrochemical properties without any hardware adjustments to the system. The system canautomatically adjust for the change in solution properties by performing a routine whichuses an auto-ranging feature to determine a current-to-voltage conversion of the sensor databy using a binary search strategy. This eliminates the intervention of the user to modify thesystem each time a new solution is tested. The effectiveness of the calibration routine wastested by carrying out cyclic voltammetry in two different solutions, 0.1M sulfuric acidsolution and the phosphate buffered solution of pH3. The sensor system was able toaccurately acquire the sensor data for each solution. Full article
Open AccessArticle Thermal Stability of Aqueous Polyurethanes Depending on the Applied Catalysts
Sensors 2006, 6(11), 1697-1707; doi:10.3390/s6111697
Received: 25 September 2006 / Accepted: 12 November 2006 / Published: 23 November 2006
Cited by 1 | PDF Full-text (157 KB) | HTML Full-text | XML Full-text
Abstract
The thermal stability of aqueous polyurethanes has been measured applying thethermogravimetric analysis. The aqueous polyurethanes (aqPUR) with catalysts of differentselectivity have been studied by use of the dynamic method. To obtain degradations of 0.025,0.05, and 0.10, employing the dynamic method, the heating [...] Read more.
The thermal stability of aqueous polyurethanes has been measured applying thethermogravimetric analysis. The aqueous polyurethanes (aqPUR) with catalysts of differentselectivity have been studied by use of the dynamic method. To obtain degradations of 0.025,0.05, and 0.10, employing the dynamic method, the heating rates of 0.5, 1, 2, 5, and 10 °Cmin-1 have been used in the range of 30-500 ºC. Using the more selective catalysts in theaqueous polyurethanes, the total resulting time of the decompositon has been on the increaseat all degrees of the degradation and at the particular starting temperature. This paper showsthat the dynamic method based on the thermogravimetric analysis can be used to assess thethermal stability of the aqueous polyurethanes using the catalysts of different selectivity. Full article
Open AccessArticle Spectroscopic Characteristics of Highly Selective Manganese Catalysis in Acqueous Polyurethane Systems
Sensors 2006, 6(11), 1708-1720; doi:10.3390/s6111708
Received: 25 September 2006 / Accepted: 12 November 2006 / Published: 20 November 2006
Cited by 7 | PDF Full-text (264 KB) | HTML Full-text | XML Full-text
Abstract
The latest investigations on producing more efficient catalytic aqueouspolyurethane systems are in the domain of metal complexes with mixed ligands. In ourprevious research works, the high selectivity for the isocyanate-hydroxyl reaction inaqueous polyurethane systems has been shown by the manganese(III) mixed-ligandcomplexes. The [...] Read more.
The latest investigations on producing more efficient catalytic aqueouspolyurethane systems are in the domain of metal complexes with mixed ligands. In ourprevious research works, the high selectivity for the isocyanate-hydroxyl reaction inaqueous polyurethane systems has been shown by the manganese(III) mixed-ligandcomplexes. The two new complexes have been prepared with two acetylacetonate (acac)ligands and one maleate ligand and its hydroxylamine derivative of the general formula[Mn(C5H7O2)2L]. Their structures have been established by using the fundamental analyses,the FTIR and UV/VIS spectroscopic methods, as well as the magnetic measurements. Inorder to explain the different selectivity of the manganese(III) mixed-ligand complexes, theUV and ESR spectroscopy have been employed to determine the kinetics of the complexes’decomposition. The thermal stability of the complexes has been determined by way of thedynamic TG method at the heating rate of 5°C⋅min-1 and at the temperature ranged 20-550°C. It suggests the decomposition of the complexes by loss of acid ligand. The main factor in the selective catalysis control in theaqueous polyurethane systems is the nature of the acid ligands and their impact on themanganese(II)/manganese(III) equilibrium. Full article

Review

Jump to: Research

Open AccessReview Application of Electronic Noses for Disease Diagnosis and Food Spoilage Detection
Sensors 2006, 6(11), 1428-1439; doi:10.3390/s6111428
Received: 22 September 2006 / Revised: 28 October 2006 / Accepted: 30 October 2006 / Published: 1 November 2006
Cited by 51 | PDF Full-text (49 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessReview Volatile Organic Compound Optical Fiber Sensors: A Review
Sensors 2006, 6(11), 1440-1465; doi:10.3390/s6111440
Received: 7 October 2006 / Revised: 31 October 2006 / Accepted: 31 October 2006 / Published: 1 November 2006
Cited by 58 | PDF Full-text (1151 KB) | HTML Full-text | XML Full-text
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Gas Sensors)
Open AccessReview Airborne Chemical Sensing with Mobile Robots
Sensors 2006, 6(11), 1616-1678; doi:10.3390/s6111616
Received: 1 October 2006 / Accepted: 8 November 2006 / Published: 20 November 2006
Cited by 50 | PDF Full-text (10884 KB) | HTML Full-text | XML Full-text
Abstract
Airborne chemical sensing with mobile robots has been an active research areasince the beginning of the 1990s. This article presents a review of research work in this field,including gas distribution mapping, trail guidance, and the different subtasks of gas sourcelocalisation. Due to [...] Read more.
Airborne chemical sensing with mobile robots has been an active research areasince the beginning of the 1990s. This article presents a review of research work in this field,including gas distribution mapping, trail guidance, and the different subtasks of gas sourcelocalisation. Due to the difficulty of modelling gas distribution in a real world environmentwith currently available simulation techniques, we focus largely on experimental work and donot consider publications that are purely based on simulations. Full article
(This article belongs to the Special Issue Gas Sensors)

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