Showing papers in "Sensors in 2005"
TL;DR: In this article, the needs associated with environmental monitoring and long-term environmental stewardship are surveyed, and emerging sensor technologies are reviewed to identify compatible technologies for various environmental monitoring applications.
Abstract: This paper surveys the needs associated with environmental monitoring and long-term environmental stewardship. Emerging sensor technologies are reviewed to identify compatible technologies for various environmental monitoring applications. The contaminants that are considered in this report are grouped into the following categories: (1) metals, (2) radioisotopes, (3) volatile organic compounds, and (4) biological contaminants. United States regulatory drivers are evaluated for different applications (e.g., drinking water, storm water, pretreatment, and air emissions), and sensor requirements are derived from these regulatory metrics. Sensor capabilities are then summarized according to contaminant type, and the applicability of the different sensors to various environmental monitoring applications is discussed.
213 citations
TL;DR: Current directions and strategies in the development and applications of electrochemical DNA sensors for the detection of DNA damage are reviewed.
Abstract: Electrochemical devices have received particular attention due to their rapid detection and great sensitivity for the evaluation of DNA-hazard compounds interaction mechanisms. Several types of bioanalytical method use nucleic acids probes to detect DNA damage. This article reviews current directions and strategies in the development and applications of electrochemical DNA sensors for the detection of DNA damage.
112 citations
TL;DR: In this paper, a survey on different types of semiconductor-based field effect structures that have been recently developed in our laboratory is presented, and a detailed analysis of the fabrication techniques of such silicon-based chemical sensors and biosensors is given.
Abstract: Microfabricated semiconductor devices are becoming increasingly relevant, also for the detection of biological and chemical quantities. Especially, the “marriage” of biomolecules and silicon technology often yields successful new sensor concepts. The fabrication techniques of such silicon-based chemical sensors and biosensors, respectively, will have a distinct impact in different fields of application such as medicine, food technology, environment, chemistry and biotechnology as well as information processing. Moreover, scientists and engineers are interested in the analytical benefits of miniaturised and microfabricated sensor devices. This paper gives a survey on different types of semiconductor-based field-effect structures that have been recently developed in our laboratory.
90 citations
TL;DR: Not only current progress in the Sensor Web technology, but also its recent application to problems in hydrology are examined to illustrate the general concepts involved.
Abstract: In 1997, the Sensor Web was conceived at the NASA/Jet Propulsion Laboratory (JPL) to take advantage of the increasingly inexpensive, yet sophisticated, mass consumer-market chips for the computer and telecommunication industries and use them to create platforms that share information among themselves and act in concert as a single instrument. This instrument would be embedded into an environment to monitor and even control it. The Sensor Web's purpose is to extract knowledge from the data it collects and use this information to intelligently react and adapt to its surroundings. It links a remote end-user's cognizance with the observed environment. Here, we examine not only current progress in the Sensor Web technology, but also its recent application to problems in hydrology to illustrate the general concepts involved.
88 citations
TL;DR: In this paper, a cyclic voltammetric results indicated that the redox protein and enzyme underwent effective and stable direct electron transfer reaction with a pair of nearly symmetrical redox peaks.
Abstract: The redox protein and enzyme, such as hemoglobin (Hb), horseradish peroxidase (HRP) and glucose oxidase (GOx), was immobilized on the surface of the carbon nanotube modified glassy carbon (CNT/GC) electrode, respectively. The cyclic voltammetric results indicated that the redox protein and enzyme underwent effective and stable direct electron transfer reaction with a pair of nearly symmetrical redox peaks. The formal redox potential, E0′, was almost independent on the scan rates, the average value of E0′ for Hb, HRP and GOx was –0.343 ± 0.001, –0.319 ± 0.002 and –0.456 ± 0.0008 V (vs. SCE, pH 6.9), respectively. The dependence of E0′ on the pH solution indicated that the direct electron transfer of Hb and HRP was a one-electron-transfer reaction process coupled with one-proton-transfer, while the GOx was a two-electron-transfer coupled with two-proton-transfer. The apparent heterogeneous electron transfer rate constant (ks) was 1.25 ± 0.25, 2.07 ± 0.69 and 1.74 ± 0.42 s-1 for Hb, HRP and GOx, respectively. The method presented here can be easily extended to immobilize other redox enzymes or proteins and obtain their direct electrochemistry.
65 citations
TL;DR: In this article, an amperometric biosensor for hydrogen peroxide (H2O2) was developed via an easy and effective enzyme immobilization method with the "sandwich" configuration.
Abstract: An amperometric biosensor for hydrogen peroxide (H2O2) was developed via an easy and effective enzyme immobilization method with the “sandwich” configuration: ferrocene-chitosan: HRP: chitosan-glyoxal using a glassy carbon electrode as the basic electrode. In order to prevent the loss of immobilized HRP under optimized conditions, the biosensor surface was cross-linked with glyoxal. Ferrocene was selected and immobilized on the glassy carbon electrode surface as a mediator. The fabrication procedure was systematically optimized to improve the biosensor performance. The biosensor had a fast response of less than 10 s to H2O2, with a linear range of 3.5×10-5 to 1.1×10-3 M, and a detection limit of 8.0×10-6 M based on S/N = 3.
65 citations
TL;DR: In this paper, a new heavy metal biosensor based on interaction of heavy metalions (Cd2+ and Zn2+ ) with phytochelatin, which was adsorbed on the surface of the hangingmercury drop electrode, using adsorptive transfer stripping differential pulse voltammetry.
Abstract: Electrochemical biosensors have superior properties over other existingmeasurement systems because they can provide rapid, simple and low-cost on-fielddetermination of many biological active species and a number of dangerous pollutants Inour work, we suggested a new heavy metal biosensor based on interaction of heavy metalions (Cd2+ and Zn2+ ) with phytochelatin, which was adsorbed on the surface of the hangingmercury drop electrode, using adsorptive transfer stripping differential pulse voltammetryIn addition, we applied the suggested technique for the determination of heavy metals in abiological sample – human urine and platinum in a pharmaceutical drug The detectionlimits (3 S/N) of Cd(II), Zn(II) and cis-platin were about 10, 133 and 19 pmole in 5 μl,respectively On the basis of the obtained results, we propose that the suggested techniqueoffers simple, rapid, and low-cost detection of heavy metals in environmental, biologicaland medical samples
60 citations
TL;DR: In this paper, the use of the planar type sensing system has been extended for the evaluation of near surface material properties such as conductivity, permittivity, permeability etc and can also be used for the inspection of defects in the near surface of materials.
Abstract: High performance planar electromagnetic sensors, their modeling and a few applications have been reported in this paper. The researches employing planar type electromagnetic sensors have started quite a few years back with the initial emphasis on the inspection of defects on printed circuit board. The use of the planar type sensing system has been extended for the evaluation of near-surface material properties such as conductivity, permittivity, permeability etc and can also be used for the inspection of defects in the near-surface of materials. Recently the sensor has been used for the inspection of quality of saxophone reeds and dairy products. The electromagnetic responses of planar interdigital sensors with pork meats have been investigated.
51 citations
TL;DR: A modified nonlinear least-squares based algorithm developed to analyze data taken by the ENose is described, and its performance for the identification and quantification of single gases and binary mixtures of twelve target analytes in clean air is described.
Abstract: The Jet Propulsion Laboratory has recently developed and built an electronic nose (ENose) using a polymer-carbon composite sensing array. This ENose is designed to be used for air quality monitoring in an enclosed space, and is designed to detect, identify and quantify common contaminants at concentrations in the parts-per-million range. Its capabilities were demonstrated in an experiment aboard the National Aeronautics and Space Administration's Space Shuttle Flight STS-95. This paper describes a modified nonlinear least-squares based algorithm developed to analyze data taken by the ENose, and its performance for the identification and quantification of single gases and binary mixtures of twelve target analytes in clean air. Results from laboratory-controlled events demonstrate the effectiveness of the algorithm to identify and quantify a gas event if concentration exceeds the ENose detection threshold. Results from the flight test demonstrate that the algorithm correctly identifies and quantifies all registered events (planned or unplanned, as singles or mixtures) with no false positives and no inconsistencies with the logged events and the independent analysis of air samples.
50 citations
TL;DR: The calibration of pH meters including the pH glass electrode, ISE electrodes, buffers, and the general background for calibration are reviewed in this paper, where basic concepts of pH, pOH, and electrode mechanism are emphasized.
Abstract: The calibration of pH meters including the pH glass electrode, ISE electrodes, buffers, and the general background for calibration are reviewed. Understanding of basic concepts of pH, pOH, and electrode mechanism is emphasized. New concepts of pH, pOH, as well as critical examination of activity, and activity coefficients are given. The emergence of new solid state pH electrodes and replacement of the salt bridge with a conducting wire have opened up a new horizon for pH measurements. A pH buffer solution with a conducting wire may be used as a stable reference electrode. The misleading unlimited linear Nernstian slope should be discarded. Calibration curves with 3 nonlinear portions for the entire 0—14 pH range due to the isoelectric point change effect are explained. The potential measurement with stirring or unstirring and effects by double layer (DL) and triple layer (TL) will be discussed.
46 citations
TL;DR: In this article, a template-free electrochemical method based on graphite electrode was developed for detecting nitrate in polypyrrole(PPy) nanowire modified electrodes, and the experimental results show that the electrochemical preparation parameters of the modified electrodes such as scan rate, polymerization potential, temperature of polymerization solution and polymerization time have significantly effects on the morphology of PPy nanowires.
Abstract: Polypyrrole(PPy) nanowire modified electrodes were developed by template-free electrochemical method based on graphite electrode. The modified electrode was characterized by their amperometric response towards nitrate ions. Before reduction of nitrate ions, electrochemical solid-phase extraction (EC-SPE) of nitrate in/on modified electrodes was conducted. It is found that the unusual nanowired structure of polypyrrole layer (instead of well known cauliflower structure) allows us to increase the effective surface area of the electrode and subsequently the sensitivity. And the effects of electrochemical preparation parameters of PPy nanowire modified electrodes on their corresponding characters were evaluated. The experimental results show that the electrochemical preparation parameters of the modified electrodes such as scan rate, polymerization potential, temperature of polymerization solution and polymerization time have significantly effects on the morphology of PPy nanowires and subsequently effective surface area of the electrode and electroreduction current density of nitrate. The determination sensitivity may be varied according to the modification parameters. Under a certain polymerization conditions, the corresponding sensitivity reaches 336.28 mA/M cm2 and the detection limit is 1.52×10-6 M. The proposed method was successfully applied in the detection of nitrate in the real samples.
TL;DR: In this paper, the authors reviewed selected experiments involving the use of carbon paste electrodes (CPEs) to monitor and measure brain tissue O2 levels in awake-freely-moving animals.
Abstract: In this communication we review selected experiments involving the use ofcarbon paste electrodes (CPEs) to monitor and measure brain tissue O2 levels in awakefreely-moving animals. Simultaneous measurements of rCBF were performed using the H2clearance technique. Voltammetric techniques used include both differential pulse (O2) andconstant potential amperometry (rCBF). Mild hypoxia and hyperoxia produced rapidchanges (decrease and increase respectively) in the in vivo O2 signal. Neuronal activation(tail pinch and stimulated grooming) produced similar increases in both O2 and rCBFindicating that CPE O2 currents provide an index of increases in rCBF when such increasesexceed O2 utilization. Saline injection produced a transient increase in the O2 signal whilechloral hydrate produced slower more long-lasting changes that accompanied the behavioralchanges associated with anaesthesia. Acetazolamide increased O2 levels through an increasein rCBF.
TL;DR: In this article, a large area highly uniform and ordered polypyrrole nanowire and nanotube arrays were fabricated by chemical oxidation polymerization with the help of a porous anodic aluminium oxide (AAO) template.
Abstract: Large area highly uniform and ordered polypyrrole nanowire and nanotube arrays were fabricated by chemical oxidation polymerization with the help of a porous anodic aluminium oxide (AAO) template. Under 0.2 moL/L pyrrole (H2O) and 0.2 moL/L FeCl3 (H2O) pattern, polypyrrole nanowire arrays were obtained after 2.0 hours polymerization reaction in a two-compartment reaction cell. When the reaction was stopped after 15 minutes, polypyrrole nanotube arrays have been formed. The diameter, length and density of compositive nanowires and nanotubes could be controlled by parameters of AAO template.
TL;DR: In this article, the authors used the Co(III) complex with 1,10-phenanthroline, [Co(phen) 3 ] 3+, as an electrochemical DNA marker and the Ru(II) complex, with bipyridyne, [Ru(bipy) 3 ], as a DNA oxidation catalyst, to evaluate the portion of original dsDNA which survives an incubation of the biosensor in the cleavage medium.
Abstract: DNA biosensor can serve as a powerfull tool for simple in vitro tests of chemical toxicity. In this paper, damage to DNA attached to the surface of screen-printed carbon electrode by arsenic compounds in solution is described. Using the Co(III) complex with 1,10-phenanthroline, [Co(phen) 3 ] 3+ , as an electrochemical DNA marker and the Ru(II) complex with bipyridyne, [Ru(bipy) 3 ] 2+ , as a DNA oxidation catalyst, the portion of original dsDNA which survives an incubation of the biosensor in the cleavage medium was evaluated. The model cleavage mixture was composed of an arsenic compound at 10 -3 mol/L concentration corresponding to real contaminated water, 2x10 -4 mol/L Fe(II) or Cu(II) ions as the redox catalyst, and 1.5x10 -2 mol/L hydrogen peroxide. DNA damage by arsenite, dimethylarsinic acid as the metabolic product of inorganic arsenic and widely used herbicide, as well as phenylarsonic acid and p-arsanilic acid as the representatives of feed additives was found in difference to arsenate.
TL;DR: In this article, the authors describe successful coupling of adsorptive transfer stripping (AdTS) and linear scan (EVLS) for the resolution of reduction signals of cytosine (C)and adenine (A) residues in hetero-oligodeoxynucleotides (ODNs).
Abstract: The paper describes successful coupling of adsorptive transfer stripping (AdTS) andelimination voltammetry with linear scan (EVLS) for the resolution of reduction signals of cytosine (C)and adenine (A) residues in hetero-oligodeoxynucleotides (ODNs). Short ODNs (9-mers and 20-mers)were adsorbed from a small volume on a hanging mercury drop electrode (HMDE). After washing ofthe ODN-modified electrode by water and its transferring to an electrochemical cell, voltammetric curves were measured. The AdTS EVLS was able to determine of C/A ratio of ODNs through theelimination function conserving the diffusion current component and eliminating kinetic and chargingcurrent components. This function, which provides the elimination signal in a peak-counterpeak form,increased the current sensitivity for A and C resolution, and for the recognition of bases sequences inODN chains. Optimal conditions of elimination experiments such as pH, time of adsorption, and scanrate were found. The combination of EVLS with AdTS procedure can be considered as a newdetection method in a DNA sensor.
TL;DR: Using averaged segmenting periodical graph and improved histogram estimation methods, the relationship between typical circuit structures of gas sensor circuits and their output noise is analyzed and their noise power spectra and optimal probability distribution functions are estimated.
Abstract: In this paper, the relationship between typical circuit structures of gas sensor circuits and their output noise is analyzed. By using averaged segmenting periodical graph and improved histogram estimation methods, we estimated their noise power spectra and optimal probability distribution functions (pdf). The results were confirmed through experiment studies.
TL;DR: In this article, robust and optimal multivariable estimation techniques are used to estimate the response of both a wheel speed sensor and an accelerometer placed in a car under performance tests, and the experimental results demonstrate the importance of the fusion of several intelligent sensor design techniques when designing the intelligent sensors that today's cars need.
Abstract: In the present paper, in order to estimate the response of both a wheel speed sensor and an accelerometer placed in a car under performance tests, robust and optimal multivariable estimation techniques are used. In this case, the disturbances and noises corrupting the relevant information coming from the sensors' outputs are so dangerous that their negative influence on the electrical systems impoverish the general performance of the car. In short, the solution to this problem is a safety related problem that deserves our full attention. Therefore, in order to diminish the negative effects of the disturbances and noises on the car's electrical and electromechanical systems, an optimum observer is used. The experimental results show a satisfactory improvement in the signal-to-noise ratio of the relevant signals and demonstrate the importance of the fusion of several intelligent sensor design techniques when designing the intelligent sensors that today's cars need.
TL;DR: Novel DNA-sensor with enzymatic amplification of the signal has been developed on the base of glassy carbon electrode modified with ds-DNA and horseradish peroxidase (HRP) for the detection of sulfonamide and anthracycline preparations able to interact with DNA.
Abstract: Novel DNA-sensor with enzymatic amplification of the signal has beendeveloped on the base of glassy carbon electrode modified with ds-DNA and horseradishperoxidase (HRP). Phenothiazine dyes Methylene Blue and Methylene Green were used aselectrochemical markers for the detection of sulfonamide and anthracycline preparationsable to interact with DNA. The biosensor signal related to HRP oxidation of the markersdepends on the relation between their bonded and readily oxidized forms which depends onthe nature and concentration of pharmaceuticals. Sulfonamides diminish surfaceconcentration of MB accessible for HRP reaction whereas anthracyclines releaseintercalated marker and increase the signal. The DNA-HRP sensor developed makes itpossible to detect down to 0.002 nmol L-1 of sulfamethoxazole, 0.1 nmol L-1 of sulfadiazine,0.01 nmol L-1 of sulfamethazine, 0.1 nmol L-1 of sulfaguanine, 0.05 μmol L-1 of rubomycinand 0.08 μmol L-1 of doxorubicin.
TL;DR: In this paper, a cylindrical metal cell is used to obtain complex permittivity and tanδ data of highly insulating High Voltage (HV) transformer oil samples at a wide range of frequencies and operation temperatures to demonstrate the polarization phenomena and the thermally stimulated effects.
Abstract: This work investigates the use of a specially designed cylindrical metal cell, in order to obtain complex permittivity and tanδ data of highly insulating High Voltage (HV) transformer oil samples. The data are obtained at a wide range of frequencies and operation temperatures to demonstrate the polarization phenomena and the thermally stimulated effects. Such complex permittivity measurements may be utilized as a criterion for the service life prediction of oil field electrical equipment (OFEE). Therefore, by one set of measurements on a small oil volume, data may be provided on the impending termination, or continuation of the transformer oil service life. The oil incorporating cell, attached to the appropriate measuring units, could be described as a complex permittivity sensor. In this work, the acquired dielectric data from a great number of operating distribution network power transformers were correlated to corresponding physicochemical ones to demonstrate the future potential employment of the proposed measuring technique.
TL;DR: Combining imprinted titanates with surface transverse wave resonators (STW) leads to a powerful tool for detecting engine oil degradation, which is an excellent example for oxidative deterioration processes in a highly complex matrix.
Abstract: Imprinting is a flexible and straightforward technique to generate selective sensor materials e.g. for mass-sensitive detection. Inherently, the strategy suits both molecular analytes and entire micro organisms or cells. Imprinted polyurethanes e.g. are capable of distinguishing the different xylene isomers with very appreciable selectivity factors. Combining imprinted titanates with surface transverse wave resonators (STW) leads to a powerful tool for detecting engine oil degradation, which is an excellent example for oxidative deterioration processes in a highly complex matrix. Surface imprints with geometrically equal cavities exhibit clear chemical selectivity, as can e.g. be seen through the example of different human rhinovirus (HRV) serotypes. Another example is a blood group-selective sensor prepared by templating with erythrocyte ghosts. Both the blood-group A and B imprinted material selectively distinguish between blood groups A, B and O, whereas no difference in sensor signal has been observed for AB, where both blood group antigen types are present on the cell surface.
TL;DR: An electrochemical DNA biosensor based on recognition of double or single stranded DNA (ds-DNA/ss-DNA) immobilised on a self-assembled modified gold electrode is presented for denaturalization and hybridisation detection as discussed by the authors.
Abstract: An electrochemical DNA biosensor based on recognition of double or single stranded DNA (ds-DNA/ss-DNA) immobilised on a self-assembled modified gold electrode is presented for denaturalisation and hybridisation detection. DNA is covalently bond on a self assembled 3-mercaptopropionic acid monolayer by using water soluble N-3-(dimethylaminopropyl)-N prime;ethylcarbodiimide hydrochloride (EDC) and N-hydroxisulfosuccinimide (NHSS) as linkers. The interaction between the immobilised DNA and methylene blue (MB) is investigated using square wave voltammetry (SWV). The increase or diminution of peak currents of the MB upon the hybridisation or denaturalisation event at the modified electrode surface is studied.
TL;DR: In this article, Li+ ion conducting Li3PO4 thin film electrolytes with thickness 300nm, 650nm and 1.2μm were deposited on Al2O3 substrate at room temperature by thermal evaporation method.
Abstract: Li+ ion conducting Li3PO4 thin film electrolytes with thickness 300nm, 650nm and 1.2μm were deposited on Al2O3 substrate at room temperature by thermal evaporation method. Reference and sensing electrodes were printed on Au interfaces by conventional screen printing technique. The overall dimension of the sensor was 3 × 3 mm and of electrodes were 1 × 1.5 mm each. The fabricated solid state potentiometric CO2 sensors of type: CO2, O2, Au, Li2TiO3-TiO2| Li3PO4 |Li2CO3, Au, CO2, O2 have been investigated for CO2 sensing properties. The electromotive force (emf) and Δemf/dec values of the sensors are dependent on the thickness of the electrolyte film. 1.2μm thickness deposited sensor has shown good sensing behavior than the sensors with less thickness. The Δemf values of the sensor are linearly increased up to 460°C operating temperature and became stable above 460°C. Between 460-500°C temperatures region the sensor has reached an equilibrium state and the experimentally obtained Δemf values are about 80% of the theoretically calculated values. A Nernst's slope of -61mV/decade has been obtained between 250 to 5000 ppm of CO2 concentration at 500°C temperature. The sensor is suitable for ease of mass production in view of its miniaturization and cost effectiveness after some further improvement.
TL;DR: Although a number of factors limit the time resolution for monitoring brain HVA concentration dynamics, the stability of CPEs allows investigations of long-term effects of drugs, as well as behavioral studies, not possible using other in-vivo monitoring techniques.
Abstract: This review focuses on the stability of voltammetric signals recorded overperiods of months with carbon paste electrodes (CPEs) implanted in the brain. The keyinteraction underlying this stability is between the pasting oil and brain lipids that arecapable of inhibiting the fouling caused by proteins. In brain regions receiving a significantdopaminergic input, a peak due to the methylated metabolites of dopamine, principallyhomovanillic acid (HVA), is clearly resolved using slow sweep voltammetry. Although anumber of factors limit the time resolution for monitoring brain HVA concentrationdynamics, the stability of CPEs allows investigations of long-term effects of drugs, as wellas behavioral studies, not possible using other in-vivo monitoring techniques.
TL;DR: The design, construction, and applications of an electronic tongue based on an array of potentiometric sensors employing the Sequential Injection Analysis technique operated as a Virtual Instrument implemented in LabVIEW6.1™ are reported.
Abstract: In this work we report the design, construction, and applications of an electronictongue (abbreviated e-tongue) based on an array of potentiometric sensors employing theSequential Injection Analysis technique (SIA) operated as a Virtual Instrument implementedin LabVIEW6.1TM. The system can use transient and stationary responses as the measuredinput information for e-tongues. The new concepts applied, lead to different advantages tobe obtained, such as complete automation, easy handling, saving time, reliability andmodularity.
TL;DR: In this article, an adaptive filter is used to improve the performance of the rollover sensor by carrying out an optimal prediction of the relevant signal coming from the sensor, which is buried in a broad-band noise background where we have little knowledge of the noise characteristics.
Abstract: In this paper, a sensor to measure the rollover angle of a car under performance tests is presented. Basically, the sensor consists of a dual-axis accelerometer, analog-electronic instrumentation stages, a data acquisition system and an adaptive filter based on a recursive least-squares (RLS) lattice algorithm. In short, the adaptive filter is used to improve the performance of the rollover sensor by carrying out an optimal prediction of the relevant signal coming from the sensor, which is buried in a broad-band noise background where we have little knowledge of the noise characteristics. The experimental results are satisfactory and show a significant improvement in the signal-to-noise ratio at the system output.
TL;DR: In this paper, a critical study of the nucleic acid layer immobilized at glassy carbon electrodes was presented, where different studies were performed in order to assess the nature of the interaction between DNA and the electrode surface.
Abstract: In this work we present a critical study of the nucleic acid layer immobilized at glassy carbon electrodes. Different studies were performed in order to assess the nature of the interaction between DNA and the electrode surface. The adsorption and electrooxidation of DNA demonstrated to be highly dependent on the surface and nature of the glassy carbon electrode. The DNA layer immobilized at a freshly polished glassy carbon electrode was very stable even after applying highly negative potentials. The electron transfer of potassium ferricyanide, catechol and dopamine at glassy carbon surfaces modified with thin (obtained by adsorption under controlled potential conditions) and thick (obtained by casting the glassy carbon surface with highly concentrated DNA solutions) DNA layers was slower than that at the bare glassy carbon electrode, although this effect was dependent on the thickness of the layer and was not charge selective. Raman experiments showed an important decrease of the vibrational modes assigned to the nucleobases residues, suggesting a strong interaction of these residues with the electrode surface. The hybridization of oligo(dG)
TL;DR: In this paper, Tannic acid-doped polypyrrole (PPY/TA) films have been grown on gold electrodes for selective electrochemical detection of dopamine (DA).
Abstract: Tannic acid-doped polypyrrole (PPY/TA) films have been grown on goldelectrodes for selective electrochemical detection of dopamine (DA) Electrochemicalquartz crystal microbalance (EQCM) studies revealed that, in vivid contrast toperchlorate-doped polypyrrole films (PPY/ClO4-), the redox switching of PPY/TA filmsin aqueous solutions involved only cation transport if the solution pH was greater than3~4 The PPY/TA Au electrodes also exhibited attractive permselectivity forelectroactive cations, namely, effectively blocking the electrochemical reactions ofanionic ferricyanide and ascorbic acid (AA) while well retaining the electrochemicalactivities of hexaammineruthenium (III) and dopamine as cationic species A 500 HzPPY/TA film could effectively block the redox current of up to 50 mM AA Thecoexistence of ascorbic acid in the measurement solution notably enhanced the currentsignal for dopamine oxidation, due probably to the chemical regeneration of dopaminethrough an ascorbic acid-catalyzed reduction of the electro-oxidation product ofdopamine (EC’ mechanism), and the greatest amplification was found at an ascorbic acidconcentration of 10 mM The differential pulse voltammetry peak current for DAoxidation was linear with DA concentration in the range of 0 to 10 μM, with sensitivityof 0125 and 0268 μA/μM, as well as lower detection limit of 20 and 03 μM in a PBSsolution without AA and with 10 mM coexisting AA, respectively
TL;DR: Electrochemical DNA-based biosensors represent a new, easy and fast way of analysis of polluted sites, therefore they can be used as early warnings devices in areas with ecological risk as in situ measurement.
Abstract: An electrochemical DNA-based biosensor is proposed as a fast and easy screening method for the detection of genotoxic compounds in soil samples. The biosensor was assembled by immobilising double stranded Calf thymus DNA on screen-printed electrodes. The interactions between DNA and environmental pollutants can cause variations of the electrochemical proprieties of DNA when they cause a DNA damage. Preliminary studies were performed using benzene, naphthalene and anthracene derivatives as model compounds. The effect of these compounds on the surface-confined DNA was found to be linearly related to their concentration in solution. On the other hand, the objective was to optimise the ultrasonic extraction conditions of these compounds from artificially spiked soil samples. Then, the applicability of such a biosensor was evaluated by analysing soil samples from an Italian region with ecological risk (ACNA of Cengio, SV). DNA biosensor for qualitative analysis of soil presented a good correlation with a semi-quantitative method for aromatic ring systems determination as fixed wavelength fluorescence and interestingly, according results were found also with other bioassays.
TL;DR: In this paper, a sensitive method for the determination of trace antimony based on the antimony-pyrogallol red (PGR) adsorption at a carbon paste electrode (CPE) was presented.
Abstract: This work presents a sensitive method for the determination of trace antimonybased on the antimony-pyrogallol red (PGR) adsorption at a carbon paste electrode (CPE).The optimal conditions were to use an electrode containing 25% paraffin oil and 75%high purity graphite powder as working electrode, a 0.10 mol/L HCl solution containing3.0×10-5 mol/L PGR as accumulation medium and a 0.20 mol/L HCl solution aselectrolyte with an accumulation time of 150 s and a reduction time of 60 s at -0.50 Vfollowed with a sweep from -0.50 V to 0.20 V. The mechanism of the electrode reactionwas discussed. Interferences of other metal ions were studied as well. The detection limitwas 1×10-9 mol/L. The linear range was from 2.0×10-9 mol/L to 5.0×10-7 mol/L.Application of the proposed method to the determination of antimony in water andhuman hair samples gave good results.
TL;DR: The linear range of the microsensor for NO was from 10-6 to 10-9 mol/l and the detection limit was 4.2×10-10 mol/L(S/N=2).
Abstract: Amperometric detection of nitric oxide with ISO-NOPMC NO microsensors (WPI) is systemically studied in the six media including seawater. The linear range of the microsensor for NO was from 10-6 to 10-9 mol/l and the detection limit was 4.2×10-10 mol/L(S/N=2). With this method, we provide preliminary evidence that NO production could be a general attribute of marine alga (Haeterosigma akashiwo). Experiment conducted with inhibitor of uncoupler 2,4-DNP (2,4-dinitropheno) revealed that NR (nitrate reductase) activity is responsible for NO formation.