Sample records for potentiometric sensor based

  1. Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring.

    PubMed

    Bandodkar, Amay J; Hung, Vinci W S; Jia, Wenzhao; Valdés-Ramírez, Gabriela; Windmiller, Joshua R; Martinez, Alexandra G; Ramírez, Julian; Chan, Garrett; Kerman, Kagan; Wang, Joseph

    2013-01-07

    This article presents the fabrication and characterization of novel tattoo-based solid-contact ion-selective electrodes (ISEs) for non-invasive potentiometric monitoring of epidermal pH levels. The new fabrication approach combines commercially available temporary transfer tattoo paper with conventional screen printing and solid-contact polymer ISE methodologies. The resulting tattoo-based potentiometric sensors exhibit rapid and sensitive response to a wide range of pH changes with no carry-over effects. Furthermore, the tattoo ISE sensors endure repetitive mechanical deformation, which is a key requirement of wearable and epidermal sensors. The flexible and conformal nature of the tattoo sensors enable them to be mounted on nearly any exposed skin surface for real-time pH monitoring of the human perspiration, as illustrated from the response during a strenuous physical activity. The resulting tattoo-based ISE sensors offer considerable promise as wearable potentiometric sensors suitable for diverse applications.

  2. Schiff's Bases and Crown Ethers as Supramolecular Sensing Materials in the Construction of Potentiometric Membrane Sensors

    PubMed Central

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz; Riahi, Siavash

    2008-01-01

    Ionophore incorporated PVC membrane sensors are well-established analytical tools routinely used for the selective and direct measurement of a wide variety of different ions in complex biological and environmental samples. Potentiometric sensors have some outstanding advantages including simple design and operation, wide linear dynamic range, relatively fast response and rational selectivity. The vital component of such plasticized PVC members is the ionophore involved, defining the selectivity of the electrodes' complex formation. Molecular recognition causes the formation of many different supramolecules. Different types of supramolecules, like calixarenes, cyclodextrins and podands, have been used as a sensing material in the construction of ion selective sensors. Schiff's bases and crown ethers, which feature prominently in supramolecular chemistry, can be used as sensing materials in the construction of potentiometric ion selective electrodes. Up to now, more than 200 potentiometric membrane sensors for cations and anions based on Schiff's bases and crown ethers have been reported. In this review cation binding and anion complexes will be described. Liquid membrane sensors based on Schiff's bases and crown ethers will then be discussed. PMID:27879786

  3. Potentiometric sensors for the selective determination of sulbutiamine.

    PubMed

    Ahmed, M A; Elbeshlawy, M M

    1999-11-01

    Five novel polyvinyl chloride (PVC) matrix membrane sensors for the selective determination of sulbutiamine (SBA) cation are described. These sensors are based on molybdate, tetraphenylborate, reineckate, phosphotun gestate and phosphomolybdate, as possible ion-pairing agents. These sensors display rapid near-Nernstian stable response over a relatively wide concentration range 1x10(-2)-1x10(-6) M of sulbutiamine, with calibration slopes 28 32.6 mV decade(-1) over a reasonable pH range 2-6. The proposed sensors proved to have a good selectivity for SBA over some inorganic and organic cations. The five potentiometric sensors were applied successfully in the determination of SBA in a pharmaceutical preparation (arcalion-200) using both direct potentiometry and potentiometric titration. Direct potentiometric determination of microgram quantities of SBA gave average recoveries of 99.4 and 99.3 with mean standard deviation of 0.7 and 0.3 for pure SBA and arcalion-200 formulation respectively. Potentiometric titration of milligram quantities of SBA gave average recoveries of 99.3 and 98.7% with mean standard deviation of 0.7 and 1.2 for pure SBA and arcalion-200 formulation, respectively.

  4. Potentiometric Zinc Ion Sensor Based on Honeycomb-Like NiO Nanostructures

    PubMed Central

    Abbasi, Mazhar Ali; Ibupoto, Zafar Hussain; Hussain, Mushtaque; Khan, Yaqoob; Khan, Azam; Nur, Omer; Willander, Magnus

    2012-01-01

    In this study honeycomb-like NiO nanostructures were grown on nickel foam by a simple hydrothermal growth method. The NiO nanostructures were characterized by field emission electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) techniques. The characterized NiO nanostructures were uniform, dense and polycrystalline in the crystal phase. In addition to this, the NiO nanostructures were used in the development of a zinc ion sensor electrode by functionalization with the highly selective zinc ion ionophore 12-crown-4. The developed zinc ion sensor electrode has shown a good linear potentiometric response for a wide range of zinc ion concentrations, ranging from 0.001 mM to 100 mM, with sensitivity of 36 mV/decade. The detection limit of the present zinc ion sensor was found to be 0.0005 mM and it also displays a fast response time of less than 10 s. The proposed zinc ion sensor electrode has also shown good reproducibility, repeatability, storage stability and selectivity. The zinc ion sensor based on the functionalized NiO nanostructures was also used as indicator electrode in potentiometric titrations and it has demonstrated an acceptable stoichiometric relationship for the determination of zinc ion in unknown samples. The NiO nanostructures-based zinc ion sensor has potential for analysing zinc ion in various industrial, clinical and other real samples. PMID:23202217

  5. New potentiometric sensor based on molecularly imprinted nanoparticles for cocaine detection.

    PubMed

    Smolinska-Kempisty, K; Ahmad, O Sheej; Guerreiro, A; Karim, K; Piletska, E; Piletsky, S

    2017-10-15

    Here we present a potentiometric sensor for cocaine detection based on molecularly imprinted polymer nanoparticles (nanoMIPs) produced by the solid-phase imprinting method. The composition of polymers with high affinity for cocaine was optimised using molecular modelling. Four compositions were selected and polymers prepared using two protocols: chemical polymerisation in water and UV-initiated polymerisation in organic solvent. All synthesised nanoparticles had very good affinity to cocaine with dissociation constants between 0.6nM and 5.3nM. Imprinted polymers produced in organic solvent using acrylamide as a functional monomer demonstrated the highest yield and affinity, and so were selected for further sensor development. For this, nanoparticles were incorporated within a PVC matrix which was then used to prepare an ion-selective membrane integrated with a potentiometric transducer. It was demonstrated that the sensor was able to quantify cocaine in blood serum samples in the range of concentrations between 1nM and 1mM. Copyright © 2017 Elsevier B.V. All rights reserved.

  6. Paper-based potentiometric pH sensor using carbon electrode drawn by pencil

    NASA Astrophysics Data System (ADS)

    Kawahara, Ryotaro; Sahatiya, Parikshit; Badhulika, Sushmee; Uno, Shigeyasu

    2018-04-01

    A flexible and disposable paper-based pH sensor fabricated with a pencil-drawn working electrode and a Ag/AgCl paste reference electrode is demonstrated for the first time to show pH response by the potentiometric principle. The sensor substrate is made of chromatography paper with a wax-printed hydrophobic area, and various types of carbon pencils are tested as working electrodes. The pH sensitivities of the electrodes drawn by carbon pencils with different hardnesses range from 16.5 to 26.9 mV/pH. The proposed sensor is expected to be more robust against shape change in electrodes on a flexible substrate than other types of chemiresistive/amperometric pH sensors.

  7. Potentiometric chemical sensors from lignin-poly(propylene oxide) copolymers doped by carbon nanotubes.

    PubMed

    Rudnitskaya, Alisa; Evtuguin, Dmitry V; Costa, Luis C; Graça, M Pedro F; Fernandes, António J S; Correia, M Rosario P; Gomes, M Teresa S R; Oliveira, J A B P

    2013-01-21

    Hardwood and softwood lignins obtained from industrial sulphite and kraft and laboratory oxygen-organosolv pulping processes were employed in co-polymerization with tolylene 2,4-diisocyanate terminated poly(propylene glycol). The obtained lignin-based polyurethanes were doped with 0.72 w/w% of multiwall carbon nanotubes (MWCNTs) with the aim of increasing their electrical conductivity to the levels suitable for sensor applications. Effects of the polymer doping with MWCNTs were assessed using electrical impedance (EIS) and UV-Resonance Raman (UV-RR) spectroscopy. Potentiometric sensors were prepared by drop casting of liquid polymer on the surface of carbon glass or platinum electrodes. Lignin-based sensors displayed a very low or no sensitivity to all alkali, alkali-earth and transition metal cations ions except Cr(VI) at pH 2. Response to Cr(VI) values of 39, 50 and 53 mV pX(-1) for the sensors based on kraft, organosolv and lignosulphonate lignins, respectively, were observed. Redox sensitivity values close to the theoretical values of 20 and 21 mV pX(-1) for organosolv and lignosulphonate based sensors respectively were detected in the Cr(III)/Cr(VI) solutions while a very low response was observed in the solutions containing Fe(CN)(6)(3-/4-). Conducting composite lignin-based polyurethanes doped with MWCNTs were suggested as being promising materials for Cr(VI)-sensitive potentiometric sensors.

  8. Potentiometric sensors using cotton yarns, carbon nanotubes and polymeric membranes.

    PubMed

    Guinovart, Tomàs; Parrilla, Marc; Crespo, Gastón A; Rius, F Xavier; Andrade, Francisco J

    2013-09-21

    A simple and generalized approach to build electrochemical sensors for wearable devices is presented. Commercial cotton yarns are first turned into electrical conductors through a simple dyeing process using a carbon nanotube ink. These conductive yarns are then partially coated with a suitable polymeric membrane to build ion-selective electrodes. Potentiometric measurements using these yarn-potentiometric sensors are demonstrated. Examples of yarns that can sense pH, K(+) and NH4(+) are presented. In all cases, these sensing yarns show limits of detection and linear ranges that are similar to those obtained with lab-made solid-state ion-selective electrodes. Through the immobilization of these sensors in a band-aid, it is shown that this approach could be easily implemented in a wearable device. Factors affecting the performance of the sensors and future potential applications are discussed.

  9. A Printed Organic Amplification System for Wearable Potentiometric Electrochemical Sensors.

    PubMed

    Shiwaku, Rei; Matsui, Hiroyuki; Nagamine, Kuniaki; Uematsu, Mayu; Mano, Taisei; Maruyama, Yuki; Nomura, Ayako; Tsuchiya, Kazuhiko; Hayasaka, Kazuma; Takeda, Yasunori; Fukuda, Takashi; Kumaki, Daisuke; Tokito, Shizuo

    2018-03-02

    Electrochemical sensor systems with integrated amplifier circuits play an important role in measuring physiological signals via in situ human perspiration analysis. Signal processing circuitry based on organic thin-film transistors (OTFTs) have significant potential in realizing wearable sensor devices due to their superior mechanical flexibility and biocompatibility. Here, we demonstrate a novel potentiometric electrochemical sensing system comprised of a potassium ion (K + ) sensor and amplifier circuits employing OTFT-based pseudo-CMOS inverters, which have a highly controllable switching voltage and closed-loop gain. The ion concentration sensitivity of the fabricated K + sensor was 34 mV/dec, which was amplified to 160 mV/dec (by a factor of 4.6) with high linearity. The developed system is expected to help further the realization of ultra-thin and flexible wearable sensor devices for healthcare applications.

  10. Epidermal tattoo potentiometric sodium sensors with wireless signal transduction for continuous non-invasive sweat monitoring.

    PubMed

    Bandodkar, Amay J; Molinnus, Denise; Mirza, Omar; Guinovart, Tomás; Windmiller, Joshua R; Valdés-Ramírez, Gabriela; Andrade, Francisco J; Schöning, Michael J; Wang, Joseph

    2014-04-15

    This article describes the fabrication, characterization and application of an epidermal temporary-transfer tattoo-based potentiometric sensor, coupled with a miniaturized wearable wireless transceiver, for real-time monitoring of sodium in the human perspiration. Sodium excreted during perspiration is an excellent marker for electrolyte imbalance and provides valuable information regarding an individual's physical and mental wellbeing. The realization of the new skin-worn non-invasive tattoo-like sensing device has been realized by amalgamating several state-of-the-art thick film, laser printing, solid-state potentiometry, fluidics and wireless technologies. The resulting tattoo-based potentiometric sodium sensor displays a rapid near-Nernstian response with negligible carryover effects, and good resiliency against various mechanical deformations experienced by the human epidermis. On-body testing of the tattoo sensor coupled to a wireless transceiver during exercise activity demonstrated its ability to continuously monitor sweat sodium dynamics. The real-time sweat sodium concentration was transmitted wirelessly via a body-worn transceiver from the sodium tattoo sensor to a notebook while the subjects perspired on a stationary cycle. The favorable analytical performance along with the wearable nature of the wireless transceiver makes the new epidermal potentiometric sensing system attractive for continuous monitoring the sodium dynamics in human perspiration during diverse activities relevant to the healthcare, fitness, military, healthcare and skin-care domains. © 2013 Published by Elsevier B.V.

  11. Integrated potentiometric detector for use in chip-based flow cells

    PubMed

    Tantra; Manz

    2000-07-01

    A new kind of potentiometric chip sensor for ion-selective electrodes (ISE) based on a solvent polymeric membrane is described. The chip sensor is designed to trap the organic cocktail inside the chip and to permit sample solution to flow past the membrane. The design allows the sensor to overcome technical problems of ruggedness and would therefore be ideal for industrial processes. The sensor performance for a Ba2+-ISE membrane based on a Vogtle ionophore showed electrochemical behavior similar to that observed in conventional electrodes and microelectrode arrangements.

  12. A selective potentiometric copper (II) ion sensor based on the functionalized ZnO nanorods.

    PubMed

    Khun, K; Ibupoto, Z H; Liu, X; Nur, O; Willander, M; Danielsson, B

    2014-09-01

    In this work, ZnO nanorods were hydrothermally grown on the gold-coated glass substrate and characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) techniques. The ZnO nanorods were functionalized by two different approaches and performance of the sensor electrode was monitored. Fourier transform infrared spectroscopy (FTIR) was carried out for the confirmation of interaction between the ionophore molecules and ZnO nanorods. In addition to this, the surface of the electrode was characterized by X-ray photoelectron spectroscopy (XPS) showing the chemical and electronic state of the ionophore and ZnO nanorod components. The ionophore solution was prepared in the stabilizer, poly vinyl chloride (PVC) and additives, and then functionalized on the ZnO nanorods that have shown the Nernstian response with the slope of 31 mV/decade. However, the Cu2+ ion sensor was fabricated only by immobilizing the selective copper ion ionophore membrane without the use of PVC, plasticizers, additives and stabilizers and the sensor electrode showed a linear potentiometric response with a slope of 56.4 mV/decade within a large dynamic concentration range (from 1.0 x 10(-6) to 1.0 x 10(-1) M) of copper (II) nitrate solutions. The sensor showed excellent repeatability and reproducibility with response time of less than 10 s. The negligible response to potentially interfering metal ions such as calcium (Ca2+), magnesium (Mg2+), potassium (K+), iron (Fe3+), zinc (Zn2+), and sodium (Na+) allows this sensor to be used in biological studies. It may also be used as an indicator electrode in the potentiometric titration.

  13. Automated electronic tongue based on potentiometric sensors for the determination of a trinary anionic surfactant mixture.

    PubMed

    Cortina, Montserrat; Ecker, Christina; Calvo, Daniel; del Valle, Manuel

    2008-01-22

    An automated electronic tongue consisting of an array of potentiometric sensors and an artificial neural network (ANN) has been developed to resolve mixtures of anionic surfactants. The sensor array was formed by five different flow-through sensors for anionic surfactants, based on poly(vinyl chloride) membranes having cross-sensitivity features. Feedforward multilayer neural networks were used to predict surfactant concentrations. As a great amount of information is required for the correct modelling of the sensors response, a sequential injection analysis (SIA) system was used to automatically provide it. Dodecylsulfate (DS(-)), dodecylbenzenesulfonate (DBS(-)) and alpha-alkene sulfonate (ALF(-)) formed the three-analyte study case resolved in this work. Their concentrations varied from 0.2 to 4mM for ALF(-) and DBS(-) and from 0.2 to 5mM for DS(-). Good prediction ability was obtained with correlation coefficients better than 0.933 when the obtained values were compared with those expected for a set of 16 external test samples not used for training.

  14. Potentiometric determination of pantoprazole using an ion-selective sensor based on polypyrrole doped films.

    PubMed

    Noronha, Bárbara V; Bindewald, Eduardo H; de Oliveira, Michelle C; Papi, Maurício A P; Bergamini, Márcio F; Marcolino, Luiz H

    2014-10-01

    The present work reports for the first time the use of polypyrrole (PPy) doped film for development of a potentiometric disposable sensor for determination of pantoprazole (PTZ), a drug used for ulcer treatment. Selective potentiometric response has been found by using a membrane of PPy doped with PTZ anions prepared under galvanostatic conditions at graphite pencil electrode (GPEM/PPy-PTZ) surface. Potentiometric response has been influenced for conditions adopted in polymerization and measurement step. After optimization of experimental (e.g. pH and time of conditioning) and instrumental parameters (e.g. current density and electrical charge) a linear analytical curve from 1.0 × 10(-5) to 1.1 × 10(-2) mol L(-1) with a slope of calibration of the 57.6 mV dec(-1) and limit of detection (LOD) of 6.9 × 10(-6) mol L(-1) was obtained. The determination of the PTZ content in pharmaceutical samples using the proposed methodology and official method recommended by Brazilian Pharmacopeia are in agreement at the 95% confidence level and within an acceptable range of error. Copyright © 2014 Elsevier B.V. All rights reserved.

  15. Combinatorial screening of potentiometric Pb(II) sensors from polysulfoaminoanthraquinone solid ionophore.

    PubMed

    Huang, Mei-Rong; Ding, Yong-Bo; Li, Xin-Gui

    2014-03-10

    A potentiometric Pb(II)-selective sensor was fabricated by a combinatorial screening of electrically conducting polysulfoaminoanthraquinone (PSA) nanoparticles as a solid ionophore, ion exchangers (oleic acid (OA) and NaTPB), plasticizers in a polyvinyl chloride (PVC) matrix, membrane thickness, inner filling ion species, and concentration. The membrane sensor with the composition of PSA/PVC/DOP (dioctyl phthalate)/OA (1.0:33:61:5.0) exhibited the best performance, including a slope of 29.3 mV decade(-1) in the concentration range 10(-6.3)-10(-1.6) M, detection limit of 1.6 × 10(-7) M, response time of 16 s, lifetime of five months, and good response reversibility. The proposed sensor has demonstrated good selectivity for Pb(II) over other monovalent, divalent and trivalent interfering ions, and could be used in a pH range of 3.62-5.22. The Pb(II) sensor has been successfully applied for the determination of Pb(II) concentration in real-world samples and also as an indicator electrode for potentiometric titration of lead ions.

  16. A potentiometric non-enzymatic glucose sensor using a molecularly imprinted layer bonded on a conducting polymer.

    PubMed

    Kim, Dong-Min; Moon, Jong-Min; Lee, Won-Chul; Yoon, Jang-Hee; Choi, Cheol Soo; Shim, Yoon-Bo

    2017-05-15

    A non-enzymatic potentiometric glucose sensor for the determination of glucose in the micomolar level in saliva was developed based on a molecularly imprinted polymer (MIP) binding on a conducting polymer layer. A MIP containing acrylamide, and aminophenyl boronic acid, as a host molecule to glucose, was immobilized on benzoic acid-functionalized poly(terthiophene) (pTBA) by the amide bond formation onto a gold nanoparticles deposited-screen printed carbon electrode (pTBA/AuNPs/SPCE). Aromatic boronic acid was incorporated into the MIP layer to stably capture glucose and create a potentiometric signal through the changed pKa value of polymer film by the formation of boronate anion-glucose complex with generation of H + ions by the cis-diol reaction. Reversible binding and extraction of glucose on the sensor surface was observed using a quartz crystal microbalance. Each layer of the sensor probe was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The potentiometric response at the optimized conditions exhibited a wide linear dynamic range of 3.2×10 -7 to 1.0×10 -3 M, with a detection limit of 1.9 (±0.15)×10 -7 M. The sensor probe revealed an excellent selectivity and sensitivity for glucose compared to other saccharides. In addition, the reliability of the proposed glucose sensor was evaluated in physiological fluid samples of saliva and finger prick blood. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Strontium (II)-Selective Potentiometric Sensor Based on Ester Derivative of 4-tert-butylcalix(8)arene in PVC Matrix

    PubMed Central

    Jain, Ajay K.; Gupta, Vinod K.; Raisoni, Jitendra R.

    2004-01-01

    Membranes of 4-tert-butylcalix(8)arene-octaacetic acid octaethyl ester (I) as an electroactive material, sodium tetraphenyl borate (NaTPB) as an anion excluder, and tri-n-butyl phosphate (TBP) as a solvent mediator in poly(vinyl chloride) (PVC) matrix have been tried for a strontium-selective sensor. The best performance was exhibited by the membrane having a composition 5:100:150:2 (I: PVC: TBP: NaTPB (w/w)). This sensor exhibits a good potentiometric response to Sr2+ over a wide concentration range (3.2 × 10 –5 –1.0 × 10 –1 M) with a Nernstian slope (30 mV/ decade). The response time of the sensor is 10 s and it has been used for a period of four months without any drift in potentials. The selectivity coefficient values are in the order of 0.01 for mono-, bi-, and trivalent cations which indicate a good selectivity for Sr2+ over a large number of cations. The useful pH range for the sensor was found to be 3-10 and it works well in mixtures with non-aqueous content up to 25 % (v/v). The sensor has been used as an indicator electrode in the potentiometric titration of Sr2+ against EDTA.

  18. Developments in the Field of Conducting and Non-conducting Polymer Based Potentiometric Membrane Sensors for Ions Over the Past Decade

    PubMed Central

    Faridbod, Farnoush; Ganjali, Mohammad Reza; Dinarvand, Rassoul; Norouzi, Parviz

    2008-01-01

    Many research studies have been conducted on the use of conjugated polymers in the construction of chemical sensors including potentiometric, conductometric and amperometric sensors or biosensors over the last decade. The induction of conductivity on conjugated polymers by treating them with suitable oxidizing agents won Heeger, MacDiarmid and Shirakawa the 2000 Nobel Prize in Chemistry. Common conjugated polymers are poly(acetylene)s, poly(pyrrole)s, poly(thiophene)s, poly(terthiophene)s, poly(aniline)s, poly(fluorine)s, poly(3-alkylthiophene)s, polytetrathiafulvalenes, poly-napthalenes, poly(p-phenylene sulfide), poly(p-phenylenevinylene)s, poly(3,4-ethylene-dioxythiophene), polyparaphenylene, polyazulene, polyparaphenylene sulfide, poly-carbazole and polydiaminonaphthalene. More than 60 sensors for inorganic cations and anions with different characteristics based on conducting polymers have been reported. There have also been reports on the application of non-conducting polymers (nCPs), i.e. PVC, in the construction of potentiometric membrane sensors for determination of more than 60 inorganic cations and anions. However, the leakage of ionophores from the membranes based on these polymers leads to relatively lower life times. In this article, we try to give an overview of Solid-Contact ISE (SCISE), Single-Piece ISE (SPISE), Conducting Polymer (CP)-Based, and also non-conducting polymer PVC-based ISEs for various ions which their difference is in the way of the polymer used with selective\\ membrane. In SCISEs and SPISEs, the plasticized PVC containing the ionophore and ionic additives govern the selectivity behavior of the electrode and the conducting polymer is responsible of ion-to-electron transducer. However, in CPISEs, the conducting polymer layer is doped with a suitable ionophore which enhances the ion selectivity of the CP while its redox response has to be suppressed. PMID:27879825

  19. Modern Directions for Potentiometric Sensors

    PubMed Central

    Bakker, Eric; Chumbimuni-Torres, Karin

    2009-01-01

    This paper gives an overview of the newest developments of polymeric membrane ion-selective electrodes. A short essence of the underlying theory is given, emphasizing how the electromotive force may be used to assess binding constants of the ionophore, and how the selectivity and detection limit are related to the underlying membrane processes. The recent developments in lowering the detection limits of ISEs are described, including recent approaches of developing all solid state ISEs, and breakthroughs in detecting ultra-small quantities of ions at low concentrations. These developments have paved the way to use potentiometric sensors as in ultra-sensitive affinity bioanalysis in conjunction with nanoparticle labels. Recent results establish that potentiometry compares favorably to electrochemical stripping analysis. Other new developments with ion-selective electrodes are also described, including the concept of backside calibration potentiometry, controlled current coulometry, pulsed chronopotentiometry, and localized flash titration with ion-selective membranes to design sensors for the direct detection of total acidity without net sample perturbation. These developments have further opened the field for exciting new possibilities and applications. PMID:19890473

  20. Planar Zeolite Film-Based Potentiometric Gas Sensors Manufactured by a Combined Thick-Film and Electroplating Technique

    PubMed Central

    Marr, Isabella; Reiß, Sebastian; Hagen, Gunter; Moos, Ralf

    2011-01-01

    Zeolites are promising materials in the field of gas sensors. In this technology-oriented paper, a planar setup for potentiometric hydrocarbon and hydrogen gas sensors using zeolites as ionic sodium conductors is presented, in which the Pt-loaded Na-ZSM-5 zeolite is applied using a thick-film technique between two interdigitated gold electrodes and one of them is selectively covered for the first time by an electroplated chromium oxide film. The influence of the sensor temperature, the type of hydrocarbons, the zeolite film thickness, and the chromium oxide film thickness is investigated. The influence of the zeolite on the sensor response is briefly discussed in the light of studies dealing with zeolites as selectivity-enhancing cover layers. PMID:22164042

  1. Molecular dynamics simulation of potentiometric sensor response: the effect of biomolecules, surface morphology and surface charge.

    PubMed

    Lowe, B M; Skylaris, C-K; Green, N G; Shibuta, Y; Sakata, T

    2018-05-10

    The silica-water interface is critical to many modern technologies in chemical engineering and biosensing. One technology used commonly in biosensors, the potentiometric sensor, operates by measuring the changes in electric potential due to changes in the interfacial electric field. Predictive modelling of this response caused by surface binding of biomolecules remains highly challenging. In this work, through the most extensive molecular dynamics simulation of the silica-water interfacial potential and electric field to date, we report a novel prediction and explanation of the effects of nano-morphology on sensor response. Amorphous silica demonstrated a larger potentiometric response than an equivalent crystalline silica model due to increased sodium adsorption, in agreement with experiments showing improved sensor response with nano-texturing. We provide proof-of-concept that molecular dynamics can be used as a complementary tool for potentiometric biosensor response prediction. Effects that are conventionally neglected, such as surface morphology, water polarisation, biomolecule dynamics and finite-size effects, are explicitly modelled.

  2. Light-Addressable Potentiometric Sensors for Quantitative Spatial Imaging of Chemical Species.

    PubMed

    Yoshinobu, Tatsuo; Miyamoto, Ko-Ichiro; Werner, Carl Frederik; Poghossian, Arshak; Wagner, Torsten; Schöning, Michael J

    2017-06-12

    A light-addressable potentiometric sensor (LAPS) is a semiconductor-based chemical sensor, in which a measurement site on the sensing surface is defined by illumination. This light addressability can be applied to visualize the spatial distribution of pH or the concentration of a specific chemical species, with potential applications in the fields of chemistry, materials science, biology, and medicine. In this review, the features of this chemical imaging sensor technology are compared with those of other technologies. Instrumentation, principles of operation, and various measurement modes of chemical imaging sensor systems are described. The review discusses and summarizes state-of-the-art technologies, especially with regard to the spatial resolution and measurement speed; for example, a high spatial resolution in a submicron range and a readout speed in the range of several tens of thousands of pixels per second have been achieved with the LAPS. The possibility of combining this technology with microfluidic devices and other potential future developments are discussed.

  3. PVC Membrane Sensors for Potentiometric Determination of Acebutolol

    PubMed Central

    Mostafa, Gamal Abdel-Hafiz; Hefnawy, Mohamed Mahmoud; Al-Majed, Abdulrahman

    2007-01-01

    The construction and general performance characteristics of two novel potentiometric membrane sensors responsive to the acebutolol are described. The sensors are based on the use of ion-association complexes of acebutolol (AC) with tetraphenylborate(TPB) (I) and phosphomolybdate(PM) (II) as exchange sites in a PVC matrix. The sensors show a fast, stable and near- Nernstian for the mono charge cation of AC over the concentration range 1×10-3 - ∼10-6 M at 25 °C over the pH range 2.0 - 6.0 with cationic slope of 51.5 ± 0.5 and 53.0 ± 0.5 per concentration decade for AC-I and AC-II sensors respectively. The lower detection limit is 6×10-6 M and 4×0-6 M with the response time 20-30 s in the same order of both sensors. Selectivity coefficients of AC related to a number of interfering cation and some organic compounds were investigated. There are negligible interferences are caused by most of the investigated species. The direct determination of 3 - 370 μg/ml of AC shows an average recovery of 99.4 and 99.5% and a mean relative standard deviation of 1.5% at 100.0 μg/ml for sensor I and II respectively. The results obtained by determination of AC in tablets using the proposed sensors which comparable favorably with those obtained by the British pharmacopoeia method. In the present investigation the electrodes have been utilized as end point indicator for some precipitation titration reactions. PMID:28903293

  4. Real-time telemetry system for amperometric and potentiometric electrochemical sensors.

    PubMed

    Wang, Wei-Song; Huang, Hong-Yi; Chen, Shu-Chun; Ho, Kuo-Chuan; Lin, Chia-Yu; Chou, Tse-Chuan; Hu, Chih-Hsien; Wang, Wen-Fong; Wu, Cheng-Feng; Luo, Ching-Hsing

    2011-01-01

    A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC), a microcontroller unit (MCU), a graphical user interface (GUI), and a radio frequency (RF) transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA) to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA). The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR) greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment), a small size of 5.6 cm × 8.7 cm, high portability, and high integration.

  5. Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors

    PubMed Central

    Wang, Wei-Song; Huang, Hong-Yi; Chen, Shu-Chun; Ho, Kuo-Chuan; Lin, Chia-Yu; Chou, Tse-Chuan; Hu, Chih-Hsien; Wang, Wen-Fong; Wu, Cheng-Feng; Luo, Ching-Hsing

    2011-01-01

    A real-time telemetry system, which consists of readout circuits, an analog-to-digital converter (ADC), a microcontroller unit (MCU), a graphical user interface (GUI), and a radio frequency (RF) transceiver, is proposed for amperometric and potentiometric electrochemical sensors. By integrating the proposed system with the electrochemical sensors, analyte detection can be conveniently performed. The data is displayed in real-time on a GUI and optionally uploaded to a database via the Internet, allowing it to be accessed remotely. An MCU was implemented using a field programmable gate array (FPGA) to filter noise, transmit data, and provide control over peripheral devices to reduce power consumption, which in sleep mode is 70 mW lower than in operating mode. The readout circuits, which were implemented in the TSMC 0.18-μm CMOS process, include a potentiostat and an instrumentation amplifier (IA). The measurement results show that the proposed potentiostat has a detectable current range of 1 nA to 100 μA, and linearity with an R2 value of 0.99998 in each measured current range. The proposed IA has a common-mode rejection ratio (CMRR) greater than 90 dB. The proposed system was integrated with a potentiometric pH sensor and an amperometric nitrite sensor for in vitro experiments. The proposed system has high linearity (an R2 value greater than 0.99 was obtained in each experiment), a small size of 5.6 cm × 8.7 cm, high portability, and high integration. PMID:22164093

  6. Micromechanical potentiometric sensors

    DOEpatents

    Thundat, Thomas G.

    2000-01-01

    A microcantilever potentiometric sensor utilized for detecting and measuring physical and chemical parameters in a sample of media is described. The microcantilevered spring element includes at least one chemical coating on a coated region, that accumulates a surface charge in response to hydrogen ions, redox potential, or ion concentrations in a sample of the media being monitored. The accumulation of surface charge on one surface of the microcantilever, with a differing surface charge on an opposing surface, creates a mechanical stress and a deflection of the spring element. One of a multitude of deflection detection methods may include the use of a laser light source focused on the microcantilever, with a photo-sensitive detector receiving reflected laser impulses. The microcantilevered spring element is approximately 1 to 100 .mu.m long, approximately 1 to 50 .mu.m wide, and approximately 0.3 to 3.0 .mu.m thick. An accuracy of detection of deflections of the cantilever is provided in the range of 0.01 nanometers of deflection. The microcantilever apparatus and a method of detection of parameters require only microliters of a sample to be placed on, or near the spring element surface. The method is extremely sensitive to the detection of the parameters to be measured.

  7. Functionalized β-cyclodextrin based potentiometric sensor for naproxen determination.

    PubMed

    Lenik, Joanna; Łyszczek, Renata

    2016-04-01

    Potentiometric sensors based on neutral β-cyclodextrins: (2-hydroxypropyl)-β-cyclodextrin, heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin and anionic β-cyclodextrin: (2-hydroxy-3-N,N,N-trimethylamino)propyl-β-cyclodextrin chloride for naproxen are described. Inclusion complexes of naproxen with the above-mentioned cyclodextrins were studied using IR spectroscopy. The electrode surface was made from PVC membranes doped with the appropriate β-cyclodextrin as ionophores and quaternary ammonium chlorides as positive charge additives that were dispersed in plasticizers. The optimum membrane contains heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin, o-nitrophenyloctyl ether and tetraoctyl ammonium chloride as a lipophilic salt. The electrode is characterized by a Nernstian response slope of -59.0 ± 0.5 mV decade(-1) over the linear range of 5.0 × 10(-5)-1.0 × 10(-2) mol L(-1) and the detection limit 1.0 × 10(-5) mol L(-1), as well as the response time 10s. It can be used in the pH range 6.2-8.5 for 10 months without any considerable deterioration. Incorporation of β-cyclodextrins improved the electrode selectivity towards naproxen ions from several inorganic and organic interferents and some common drug excipients due to concovalent interactions (host molecule-guest molecule). The notable advantages of the naproxen-selective electrode include its high sensitivity, high selectivity, cost-effectiveness as well as accurate and comfortable application in drug analysis and milk samples. Copyright © 2015. Published by Elsevier B.V.

  8. Detecting Levels of Polyquaternium-10 (PQ-10) via Potentiometric Titration with Dextran Sulphate and Monitoring the Equivalence Point with a Polymeric Membrane-Based Polyion Sensor.

    PubMed

    Ferguson, Stephen A; Wang, Xuewei; Meyerhoff, Mark E

    2016-08-07

    Polymeric quaternary ammonium salts (polyquaterniums) have found increasing use in industrial and cosmetic applications in recent years. More specifically, polyquaternium-10 (PQ-10) is routinely used in cosmetic applications as a conditioner in personal care product formulations. Herein, we demonstrate the use of potentiometric polyion-sensitive polymeric membrane-based electrodes to quantify PQ-10 levels. Mixtures containing both PQ-10 and sodium lauryl sulfate (SLS) are used as model samples to illustrate this new method. SLS is often present in cosmetic samples that contain PQ-10 (e.g., shampoos, etc.) and this surfactant species interferes with the polyion sensor detection chemistry. However, it is shown here that SLS can be readily separated from the PQ-10/SLS mixture by use of an anion-exchange resin and that the PQ-10 can then be titrated with dextran sulphate (DS). This titration is monitored by potentiometric polyanion sensors to provide equivalence points that are directly proportional to PQ-10 concentrations.

  9. Biomaterial based sulphur di oxide gas sensor

    NASA Astrophysics Data System (ADS)

    Ghosh, P. K.; Sarkar, A.

    2013-06-01

    Biomaterials are getting importance in the present research field of sensors. In this present paper performance of biomaterial based gas sensor made of gum Arabica and garlic extract had been studied. Extract of garlic clove with multiple medicinal and chemical utility can be proved to be useful in sensing Sulphur di Oxide gas. On exposure to Sulphur di Oxide gas the material under observation suffers some temporary structural change, which can be observed in form of amplified potentiometric change through simple electronic circuitry. Exploiting this very property a potentiometric gas sensor of faster response and recovery time can be designed. In this work sensing property of the said material has been studied through DC conductance, FTIR spectrum etc.

  10. Urea potentiometric enzymatic biosensor based on charged biopolymers and electrodeposited polyaniline.

    PubMed

    Lakard, Boris; Magnin, Delphine; Deschaume, Olivier; Vanlancker, Guilhem; Glinel, Karine; Demoustier-Champagne, Sophie; Nysten, Bernard; Jonas, Alain M; Bertrand, Patrick; Yunus, Sami

    2011-06-15

    A potentiometric biosensor based on urease was developed for the quantitative determination of urea concentration in aqueous solutions for biomedical applications. The urease was either physisorbed onto an electrodeposited polyaniline film (PANI), or immobilized on a layer-by-layer film (LbL) assembled over the PANI film, that was obtained by the alternate deposition of charged polysaccharides (carboxymethylpullulan (CMP) and chitosan (CHI)). In the latter case, the urease (Urs) enzyme was either physically adsorbed or covalently grafted to the LbL film using carbodiimide coupling reaction. Potentiometric responses of the enzymatic biosensors were measured as a function of the urea concentration in aqueous solutions (from 10(-6) to 10(-1) mol L(-1) urea). Very high sensitivity and short response time were observed for the present biosensor. Moreover, a stability study showed a higher stability over time for the potentiometric response of the sensor with the enzyme-grafted LbL film, testifying for the protective nature of the polysaccharide coating and the interest of covalent grafting. Copyright © 2011 Elsevier B.V. All rights reserved.

  11. A Ho(III) potentiometric polymeric membrane sensor based on a new four dentate neutral ion carrier.

    PubMed

    Zamani, Hassan Ali; Zanganeh-Asadabadi, Abbas; Rohani, Mitra; Zabihi, Mohammad Saleh; Fadaee, Javad; Ganjali, Mohammad Reza; Faridbod, Farnoush; Meghdadi, Soraia

    2013-03-01

    In this research, we report a new Ho(3+)-PVC membrane electrode based on N-(4,5-dimethyl-2-(picolinamido)phenyl)picolinamide (H(2)Me(2)bpb) as a suitable ion carrier. Poly vinylchloride (PVC)-based membrane composed of H(2)Me(2)bpb with oleic acid (OA) as anionic additives, and o-nitrophenyloctyl ether (NPOE) as plasticized solvent mediator. The sensor exhibits a Nernstian slope of 20.1 ± 0.2 mV decade(-1) over the concentration range of 1.0 × 10(-6) to 1.0 × 1(-2) mol L(-1), and a detection limit of 5.0 × 10(-7) mol L(-1) of Ho(3+) ions. The potentiometric response of the sensor is independent of the solution pH in the range of 3.5-9.4. It has a very short response time, in the whole concentration range (<10s), and can be used for at least eight weeks. The proposed electrode shows a good selectivity towards Ho(3+) ions over a wide variety of cations, including alkali, alkaline earth, transition and heavy metal ions. To assess its analytical applicability the proposed Ho(3+) sensor was successfully applied as an indicator electrode in the titration of Ho(3+) ion solutions in certified reference materials, alloy samples and for the determination of the fluoride ion in two mouthwash preparations. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Unlabeled multi tumor marker detection system based on bioinitiated light addressable potentiometric sensor.

    PubMed

    Jia, Yun-Fang; Gao, Chun-Ying; He, Jia; Feng, Dao-Fu; Xing, Ke-Li; Wu, Ming; Liu, Yang; Cai, Wen-Sheng; Feng, Xi-Zeng

    2012-08-21

    Multi biomarkers' assays are of great significance in clinical diagnosis. A label-free multi tumor markers' parallel detection system was proposed based on a light addressable potentiometric sensor (LAPS). Arrayed LAPS chips with basic structure of Si(3)N(4)-SiO(2)-Si were prepared on silicon wafers, and the label-free parallel detection system for this component was developed with user friendly controlling interfaces. Then the l-3,4-dihydroxyphenyl-alanine (L-Dopa) hydrochloric solution was used to initiate the surface of LAPS. The L-Dopa immobilization state was investigated by the theoretical calculation. L-Dopa initiated LAPS' chip was biofunctionalized respectively by the antigens and antibodies of four tumor markers, α-fetoprotein (AFP), carcinoembryonic antigen (CEA), cancer antigen 19-9 (CA19-9) and Ferritin. Then unlabeled antibodies and antigens of these four biomarkers were detected by the proposed detection systems. Furthermore physical and measuring principles in this system were described, and qualitative understanding for experimental data were given. The measured response ranges were compared with their clinical cutoff values, and sensitivities were calculated by OriginLab. The results indicate that this bioinitiated LAPS based label-free detection system may offer a new choice for the realization of unlabeled multi tumor markers' clinical assay.

  13. Determination of vanadium(V) by direct automatic potentiometric titration with EDTA using a chemically modified electrode as a potentiometric sensor.

    PubMed

    Quintar, S E; Santagata, J P; Cortinez, V A

    2005-10-15

    A chemically modified electrode (CME) was prepared and studied as a potentiometric sensor for the end-point detection in the automatic titration of vanadium(V) with EDTA. The CME was constructed with a paste prepared by mixing spectral-grade graphite powder, Nujol oil and N-2-naphthoyl-N-p-tolylhydroxamic acid (NTHA). Buffer systems, pH effects and the concentration range were studied. Interference ions were separated by applying a liquid-liquid extraction procedure. The CME did not require any special conditioning before using. The electrode was constructed with very inexpensive materials and was easily made. It could be continuously used, at least two months without removing the paste. Automatic potentiometric titration curves were obtained for V(V) within 5 x 10(-5) to 2 x 10(-3)M with acceptable accuracy and precision. The developed method was applied to V(V) determination in alloys for hip prosthesis.

  14. Solid-contact potentiometric sensors and multisensors based on polyaniline and thiacalixarene receptors for the analysis of some beverages and alcoholic drinks

    NASA Astrophysics Data System (ADS)

    Sorvin, Michail; Belyakova, Svetlana; Stoikov, Ivan; Shamagsumova, Rezeda; Evtugyn, Gennady

    2018-04-01

    Electronic tongue is a sensor array that aims to discriminate and analyze complex media like food and beverages on the base of chemometrics approaches for data mining and pattern recognition. In this review, the concept of electronic tongue comprising of solid-contact potentiometric sensors with polyaniline and thacalix[4]arene derivatives is described. The electrochemical reactions of polyaniline as a background of solid-contact sensors and the characteristics of thiacalixarenes and pillararenes as neutral ionophores are briefly considered. The electronic tongue systems described were successfully applied for assessment of fruit juices, green tea, beer and alcoholic drinks They were classified in accordance with the origination, brands and styles. Variation of the sensor response resulted from the reactions between Fe(III) ions added and sample components, i.e., antioxidants and complexing agents. The use of principal component analysis and discriminant analysis is shown for multisensor signal treatment and visualization. The discrimination conditions can be optimized by variation of the ionophores, Fe(III) concentration and sample dilution. The results obtained were compared with other electronic tongue systems reported for the same subjects.

  15. Solid-Contact Potentiometric Sensors and Multisensors Based on Polyaniline and Thiacalixarene Receptors for the Analysis of Some Beverages and Alcoholic Drinks.

    PubMed

    Sorvin, Michail; Belyakova, Svetlana; Stoikov, Ivan; Shamagsumova, Rezeda; Evtugyn, Gennady

    2018-01-01

    Electronic tongue is a sensor array that aims to discriminate and analyze complex media like food and beverages on the base of chemometrics approaches for data mining and pattern recognition. In this review, the concept of electronic tongue comprising of solid-contact potentiometric sensors with polyaniline and thacalix[4]arene derivatives is described. The electrochemical reactions of polyaniline as a background of solid-contact sensors and the characteristics of thiacalixarenes and pillararenes as neutral ionophores are briefly considered. The electronic tongue systems described were successfully applied for assessment of fruit juices, green tea, beer, and alcoholic drinks They were classified in accordance with the origination, brands and styles. Variation of the sensor response resulted from the reactions between Fe(III) ions added and sample components, i.e., antioxidants and complexing agents. The use of principal component analysis and discriminant analysis is shown for multisensor signal treatment and visualization. The discrimination conditions can be optimized by variation of the ionophores, Fe(III) concentration, and sample dilution. The results obtained were compared with other electronic tongue systems reported for the same subjects.

  16. Solid-Contact Potentiometric Sensors and Multisensors Based on Polyaniline and Thiacalixarene Receptors for the Analysis of Some Beverages and Alcoholic Drinks

    PubMed Central

    Sorvin, Michail; Belyakova, Svetlana; Stoikov, Ivan; Shamagsumova, Rezeda; Evtugyn, Gennady

    2018-01-01

    Electronic tongue is a sensor array that aims to discriminate and analyze complex media like food and beverages on the base of chemometrics approaches for data mining and pattern recognition. In this review, the concept of electronic tongue comprising of solid-contact potentiometric sensors with polyaniline and thacalix[4]arene derivatives is described. The electrochemical reactions of polyaniline as a background of solid-contact sensors and the characteristics of thiacalixarenes and pillararenes as neutral ionophores are briefly considered. The electronic tongue systems described were successfully applied for assessment of fruit juices, green tea, beer, and alcoholic drinks They were classified in accordance with the origination, brands and styles. Variation of the sensor response resulted from the reactions between Fe(III) ions added and sample components, i.e., antioxidants and complexing agents. The use of principal component analysis and discriminant analysis is shown for multisensor signal treatment and visualization. The discrimination conditions can be optimized by variation of the ionophores, Fe(III) concentration, and sample dilution. The results obtained were compared with other electronic tongue systems reported for the same subjects. PMID:29740577

  17. Ionophore-Based Potentiometric Sensors for the Flow-Injection Determination of Promethazine Hydrochloride in Pharmaceutical Formulations and Human Urine

    PubMed Central

    Hassan, Ahmed Khudhair; Saad, Bahruddin; Ghani, Sulaiman Ab; Adnan, Rohana; Rahim, Afidah Abdul; Ahmad, Norariza; Mokhtar, Marina; Ameen, Suham Tawfiq; Al-Araji, Suad Mustafa

    2011-01-01

    Plasticised poly(vinyl chloride)-based membranes containing the ionophores (α-, β- and γ-cyclodextrins (CD), dibenzo-18-crown-6 (DB18C6) and dibenzo-30-crown-10 (DB30C10) were evaluated for their potentiometric response towards promethazine (PM) in a flow injection analysis (FIA) set-up. Good responses were obtained when β- and γ-CDs, and DB30C10 were used. The performance characteristics were further improved when tetrakis(4-chlorophenyl) borate (KTPB) was added to the membrane. The sensor based on β-CD, bis(2-ethylhexyl) adipate (BEHA) and KTPB exhibited the best performance among the eighteen sensor compositions that were tested. The response was linear from 1 × 10−5 to 1 × 10−2 M, slope was 61.3 mV decade−1, the pH independent region ranged from 4.5 to 7.0, a limit of detection of 5.3 × 10−6 M was possible and a lifetime of more than a month was observed when used in the FIA system. Other plasticisers such as dioctyl phenylphosphonate and tributyl phosphate do not show significant improvements in the quality of the sensors. The promising sensors were further tested for the effects of foreign ions (Li+, Na+, K+, Mg2+, Ca2+, Co2+, Cu2+, Cr3+, Fe3+, glucose, fructose). FIA conditions (e.g., effects of flow rate, injection volume, pH of the carrier stream) were also studied when the best sensor was used (based on β-CD). The sensor was applied to the determination of PM in four pharmaceutical preparations and human urine that were spiked with different levels of PM. Good agreement between the sensor and the manufacturer’s claimed values (for pharmaceutical preparations) was obtained, while mean recoveries of 98.6% were obtained for spiked urine samples. The molecular recognition features of the sensors as revealed by molecular modelling were rationalised by the nature of the interactions and complexation energies between the host and guest molecules. PMID:22346617

  18. Potentiometric Biosensor for Studying Hydroquinone Cytotoxicity in vitro

    PubMed Central

    Wang, Yanyan; Chen, Qiang; Zeng, Xiangqun

    2009-01-01

    Many processes in living cells have electrochemical characteristics that are suitable for measurement by potentiometric biosensors. Potentiometric biosensors allow non invasive, real-time monitoring of the extracellular environment changes by measuring the potential at cell/sensor interface. This can be used as an indicator for overall cell cytotoxicity. The present work employs a potentiometric sensor array to investigate the cytotoxicity of hydroquinone to cultured mammalian V79 cells. Various electrode substrates (Au, PPy-HQ and PPy-PS) used for cell growth were designed and characterized. The controllable release of hydroquinone from PPy substrates was studied. Our results showed that hydroquinone exposure affected cell proliferation and delayed cell growth and attachment in a dose-dependent manner. Additionally, we have shown that exposure of V79 cells to hydroquinone at low doses (i.e 5μM) for more than 15 hours allows V79 cells to gain enhanced adaptability to survive exposure to high toxic HQ doses afterwards. Compared with traditional methods, the potentiometric biosensor not only provides non-invasive and real time monitoring of the cellular reactions but also is more sensitive for in vitro cytotoxicity study. By real time and non-invasive monitoring of the extracellular potential in vitro, the potentiometric sensor system represents a promising biosensor system for drug discovery. PMID:19926470

  19. Potentiometric sensors with carbon black supporting platinum nanoparticles.

    PubMed

    Paczosa-Bator, Beata; Cabaj, Leszek; Piech, Robert; Skupień, Krzysztof

    2013-11-05

    For the first time, a single-piece, all-solid-state ion-selective electrode was fabricated with carbon black supporting platinum nanoparticles (PtNPs-CB) and a polymeric membrane. The PtNPs-CB, as an intermediate layer, was drop-casted directly on the solid substrate, and then an ionophore-doped solvent polymeric membrane was added in order to form a sensor. The performance of the newly developed electrodes was evaluated on the basis of potassium and nitrate ions. The stability of the electrical potential for the electrodes was examined by performing current-reversal chronopotentiometry, and the influence of the interfacial water film was assessed by the potentiometric aqueous-layer test. Fabricated potassium- and nitrate-selective electrodes displayed a Nernstian slope and several outstanding properties such as high long-term potential stability, potential repeatability, and reproducibility.

  20. A novel, fast responding, low noise potentiometric sensor containing a carbon-based polymeric membrane for measuring surfactants in industrial and environmental applications.

    PubMed

    Samardžić, Mirela; Galović, Olivera; Hajduković, Mateja; Sak-Bosnar, Milan

    2017-01-01

    A new high-sensitivity potentiometric sensor for anionic surfactants was fabricated using the dimethyldioctadecylammonium-tetraphenylborate (DDA-TPB) ion associate as an ionophore that was incorporated into a liquid PVC membrane. Carbon powder was used for immobilization of the ionophore in the membrane, thus significantly reducing its ohmic resistance and reducing its signal drift. The sensor exhibits a sub-Nernstian response for both dodecylbenzenesulfonate (DBS) and dodecyl sulfate (DS) in H 2 O (55.3 and 58.5mV/decade of activity, respectively) in a range between 3.2×10 -7 and 4.6×10 -3 M for DS and 2.5×10 -7 and 1.2×10 -3 M for DBS. The sensor also exhibited a sub-Nernstian response for DS and DBS in 10mM Na 2 SO 4 (55.4 and 57.7mV/decade of activity, respectively) between 2.5×10 -7 and 4.6×10 -3 M for DS and 1.5×10 -7 and 8.8×10 -4 M for DBS. The detection limits for DS and DBS in H 2 O were 2.5×10 -7 and 2.0×10 -7 M and in 10mM Na 2 SO 4 the detection limits were 2.5×10 -7 and 1.2×10 -7 M, respectively. The response time of the sensor was less than 5s for changes at higher concentration levels (above 1×10 -4 M) in both water and 10mM Na 2 SO 4. At lower concentrations (below 1×10 -5 M) the response times were 8 and 6s in water and 10mM Na 2 SO 4 , respectively. The signal drift of the sensor was 1.2mV/hour. The new carbon-based sensor exhibited excellent selectivity performance for DS over almost all of the anions commonly present in commercial formulations and it was successfully employed as an end-point detector in potentiometric titrations of anionic surfactants in a pH range from 3 to 12. Three-component mixtures containing sodium alkanesulfonate (C 10 , C 12 and C 14 ) were successfully differentially titrated. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Potentiometric Sensors Based on Surface Molecular Imprinting: Detection of Cancer Biomarkers and Viruses

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Y.; Zhang, Z; Jain, V

    2010-01-01

    The continuing discovery of cancer biomarkers necessitates improved methods for their detection. Molecular imprinting using artificial materials provides an alternative to the detection of a wide range of substances. We applied surface molecular imprinting using self-assembled monolayers to design sensing elements for the detection of cancer biomarkers and other proteins. These elements consist of a gold-coated silicon chip onto which hydroxyl-terminated alkanethiol molecules and template biomolecule are co-adsorbed, where the thiol molecules are chemically bound to the metal substrate and self-assembled into highly ordered monolayers, the biomolecules can be removed, creating the foot-print cavities in the monolayer matrix for thismore » kind of template molecules. Re-adsorption of the biomolecules to the sensing chip changes its potential, which can be measured potentiometrically. We applied this method to the detection of carcinoembryonic antigen (CEA) in both solutions of purified CEA and in the culture medium of a CEA-producing human colon cancer cell line. The CEA assay, validated also against a standard immunoassay, was both sensitive (detection range 2.5-250 ng/mL) and specific (no cross-reactivity with hemoglobin; no response by a non-imprinted sensor). Similar results were obtained for human amylase. In addition, we detected virions of poliovirus in a specific manner (no cross-reactivity to adenovirus, no response by a non-imprinted sensor). Our findings demonstrate the application of the principles of molecular imprinting to the development of a new method for the detection of protein cancer biomarkers and to protein-based macromolecular structures such as the capsid of a virion. This approach has the potential of generating a general assay methodology that could be highly sensitive, specific, simple and likely inexpensive.« less

  2. Potentiometric chemical sensors for the detection of paralytic shellfish toxins.

    PubMed

    Ferreira, Nádia S; Cruz, Marco G N; Gomes, Maria Teresa S R; Rudnitskaya, Alisa

    2018-05-01

    Potentiometric chemical sensors for the detection of paralytic shellfish toxins have been developed. Four toxins typically encountered in Portuguese waters, namely saxitoxin, decarbamoyl saxitoxin, gonyautoxin GTX5 and C1&C2, were selected for the study. A series of miniaturized sensors with solid inner contact and plasticized polyvinylchloride membranes containing ionophores, nine compositions in total, were prepared and their characteristics evaluated. Sensors displayed cross-sensitivity to four studied toxins, i.e. response to several toxins together with low selectivity. High selectivity towards paralytic shellfish toxins was observed in the presence of inorganic cations with selectivity coefficients ranging from 0.04 to 0.001 for Na + and K + and 3.6*10 -4 to 3.4*10 -5 for Ca 2+ . Detection limits were in the range from 0.25 to 0.9 μmolL -1 for saxitoxin and decarbamoyl saxitoxin, and from 0.08 to 1.8 μmolL -1 for GTX5 and C1&C2, which allows toxin detection at the concentration levels corresponding to the legal limits. Characteristics of the developed sensors allow their use in the electronic tongue multisensor system for simultaneous quantification of paralytic shellfish toxins. Copyright © 2018 Elsevier B.V. All rights reserved.

  3. New potentiometric transducer based on a Mn(II) [2-formylquinoline thiosemicarbazone] complex for static and hydrodynamic assessment of azides.

    PubMed

    Kamel, Ayman H

    2015-11-01

    A new potentiometric transducer for selective recognition of azide is characterized and developed. The PVC plasticized based sensor incorporates Mn(II) [2-formylquinoline thiosemicarbazone] complex in the presence of tri dodecyl methyl ammonium chloride (TDMAC) as a lipophilic cationic additive. The sensor displayed a near-Nernstian response for azide over 1.0×10(-2)-1.0×10(-5) mol L(-1), with an anionic slope of -55.8±0.6 mV decade(-1) and lower limit of detection 0.34 µg mL(-1). The sensor was pH independent in the range 5.5-9 and presented good selectivity features towards several inorganic anions, and it is easily used in a flow injection system and compared with a tubular detector. The intrinsic characteristics of the detector in a low dispersion manifold were determined and compared with data obtained under a hydrodynamic mode of operation. This simple and inexpensive automation, with a good potentiometric detector, enabled the analysis of ~33 samples h(-1) without requiring pre-treatment procedures. The proposed method is also applied to the analysis of trace levels of azide in primer mixtures. Significantly improved accuracy, precision, response time, stability and selectivity were offered by these simple and cost-effective potentiometric sensor compared with other standard techniques. The method has the requisite accuracy, sensitivity and precision to determine azide ions. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Influences of Probe’s Morphology for Metal Ion Detection Based on Light-Addressable Potentiometric Sensors

    PubMed Central

    Shao, Chen; Zhou, Shuang; Yin, Xuebo; Gu, Yajun; Jia, Yunfang

    2016-01-01

    The sensing mechanism of binding Hg2+ into thymine-thymine (T-T) mismatched base pairs was introduced into a light-addressable potentiometric sensor (LAPS) with anti-Hg2+ aptamer as the sensing units. Three kinds of T-rich single-strand DNA (ssDNA) chains with different spacer lengths, from 0 to 12 –CH2 groups, were designed to investigate surface charge and morphological effects on the LAPS’ output. First, by comparing the responding of LAPS modified with three kinds of ssDNA, it was found that the best performance for Hg2+ sensing was exhibited by the probe without –CH2 groups. The detection limit of Hg2+ ion was 1 ppt under the optimal condition. Second, the cooperative effects of surface charge and morphology on the output were observed by the controlled experiments. The two effects were the negative charge balanced by metal cations and the morphological changing caused by the formation of T-Hg2+-T structure. In conclusion, not only the influences of the aptamer probe’s morphology and surface charge was investigated on the platform of LAPS, but also sensing Hg2+ ions was achieved for the first time by the presented aptamer LAPS. PMID:27187412

  5. Comparative study of ZnO nanorods and thin films for chemical and biosensing applications and the development of ZnO nanorods based potentiometric strontium ion sensor

    NASA Astrophysics Data System (ADS)

    Khun, K.; Ibupoto, Z. H.; Chey, C. O.; Lu, Jun.; Nur, O.; Willander, M.

    2013-03-01

    In this study, the comparative study of ZnO nanorods and ZnO thin films were performed regarding the chemical and biosensing properties and also ZnO nanorods based strontium ion sensor is proposed. ZnO nanorods were grown on gold coated glass substrates by the hydrothermal growth method and the ZnO thin films were deposited by electro deposition technique. ZnO nanorods and thin films were characterised by field emission electron microscopy [FESEM] and X-ray diffraction [XRD] techniques and this study has shown that the grown nanostructures are highly dense, uniform and exhibited good crystal quality. Moreover, transmission electron microscopy [TEM] was used to investigate the quality of ZnO thin film and we observed that ZnO thin film was comprised of nano clusters. ZnO nanorods and thin films were functionalised with selective strontium ionophore salicylaldehyde thiosemicarbazone [ST] membrane, galactose oxidase, and lactate oxidase for the detection of strontium ion, galactose and L-lactic acid, respectively. The electrochemical response of both ZnO nanorods and thin films sensor devices was measured by using the potentiometric method. The strontium ion sensor has exhibited good characteristics with a sensitivity of 28.65 ± 0.52 mV/decade, for a wide range of concentrations from 1.00 × 10-6 to 5.00 × 10-2 M, selectivity, reproducibility, stability and fast response time of 10.00 s. The proposed strontium ion sensor was used as indicator electrode in the potentiometric titration of strontium ion versus ethylenediamine tetra acetic acid [EDTA]. This comparative study has shown that ZnO nanorods possessed better performance with high sensitivity and low limit of detection due to high surface area to volume ratio as compared to the flat surface of ZnO thin films.

  6. Potentiometric Sensor for Real-Time Remote Surveillance of Actinides in Molten Salts

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Natalie J. Gese; Jan-Fong Jue; Brenda E. Serrano

    2012-07-01

    A potentiometric sensor is being developed at the Idaho National Laboratory for real-time remote surveillance of actinides during electrorefining of spent nuclear fuel. During electrorefining, fuel in metallic form is oxidized at the anode while refined uranium metal is reduced at the cathode in a high temperature electrochemical cell containing LiCl-KCl-UCl3 electrolyte. Actinides present in the fuel chemically react with UCl3 and form stable metal chlorides that accumulate in the electrolyte. This sensor will be used for process control and safeguarding of activities in the electrorefiner by monitoring the concentrations of actinides in the electrolyte. The work presented focuses onmore » developing a solid-state cation conducting ceramic sensor for detecting varying concentrations of trivalent actinide metal cations in eutectic LiCl-KCl molten salt. To understand the basic mechanisms for actinide sensor applications in molten salts, gadolinium was used as a surrogate for actinides. The ß?-Al2O3 was selected as the solid-state electrolyte for sensor fabrication based on cationic conductivity and other factors. In the present work Gd3+-ß?-Al2O3 was prepared by ion exchange reactions between trivalent Gd3+ from GdCl3 and K+-, Na+-, and Sr2+-ß?-Al2O3 precursors. Scanning electron microscopy (SEM) was used for characterization of Gd3+-ß?-Al2O3 samples. Microfocus X-ray Diffraction (µ-XRD) was used in conjunction with SEM energy dispersive X-ray spectroscopy (EDS) to identify phase content and elemental composition. The Gd3+-ß?-Al2O3 materials were tested for mechanical and chemical stability by exposing them to molten LiCl-KCl based salts. The effect of annealing on the exchanged material was studied to determine improvements in material integrity post ion exchange. The stability of the ß?-Al2O3 phase after annealing was verified by µ-XRD. Preliminary sensor tests with different assembly designs will also be presented.« less

  7. Review on State-of-the-art in Polymer Based pH Sensors

    PubMed Central

    Korostynska, Olga; Arshak, Khalil; Gill, Edric; Arshak, Arousian

    2007-01-01

    This paper reviews current state-of-the-art methods of measuring pH levels that are based on polymer materials. These include polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory approach for ion concentration monitoring. PMID:28903277

  8. Potentiometric determination of moxifloxacin in some pharmaceutical formulation using PVC membrane sensors.

    PubMed

    Hefnawy, Mohammed M; Homoda, Atef M; Abounassif, Mohammed A; Alanazi, Amer M; Al-Majed, Abdulrahaman; Mostafa, Gamal A

    2014-01-01

    The construction and electrochemical response characteristics of Poly (vinyl chloride) membrane sensors for moxifloxacin HCl (MOX) are described. The sensing membranes incorporate ion association complexes of moxifloxacin cation and sodium tetraphenyl borate (NaTPB) (sensor 1), phosphomolybdic acid (PMA) (sensor 2) or phosphotungstic acid (PTA) (sensor 3) as electroactive materials. The sensors display a fast, stable and near-Nernstian response over a relative wide moxifloxacin concentration range (1 × 10(-2) - 4.0 × 10(-6), 1 × 10(-2) - 5.0 × 10(-6), 1 × 10(-2) - 5.0 × 10(-6) M), with detection limits of 3 × 10(-6), 4 × 10(-6) and 4.0 × 10(-6) M for sensor 1, 2 and 3, respectively over a pH range of 6.0 - 9.0. The sensors show good discrimination of moxifloxacin from several inorganic and organic compounds. The direct determination of 400 μg/ml of moxifloxacin show an average recovery of 98.5, 99.1 and 98.6% and a mean relative standard deviation of 1.8, 1.6 and 1.8% for sensors 1, 2 and 3 respectively. The proposed sensors have been applied for direct determination of moxifloxacin in some pharmaceutical preparations. The results obtained by determination of moxifloxacin in tablets using the proposed sensors are comparable favorably with those obtained using the US Pharmacopeia method. The sensors have been used as indicator electrodes for potentiometric titration of moxifloxacin.

  9. Micellar and analytical implications of a new potentiometric PVC sensor based on neutral ion-pair complexes of dodecylmethylimidazolium bromide-sodium dodecylsulfate.

    PubMed

    Sanan, Reshu; Mahajan, Rakesh Kumar

    2013-03-15

    With an aim to characterize the micellar aggregates of imidazolium based ionic liquids, a new potentiometric PVC sensor based on neutral ion-pair complexes of dodecylmethylimidazolium bromide-sodium dodecylsulfate (C12MeIm(+)DS(-)) has been developed. The electrode exhibited a linear response for the concentration range of 7.9×10(-5)-9.8×10(-3) M with a super-Nernstian slope of 92.94 mV/decade, a response time of 5 s and critical micellar concentration (cmc) of 10.09 mM for C12MeImBr. The performance of the electrode in investigating the cmc of C12MeImBr in the presence of two drugs [promazine hydrochloride (PMZ) and promethazine hydrochloride (PMT)] and three triblock copolymers (P123, L64 and F68) has been found to be satisfactory on comparison with conductivity measurements. Various micellar parameters have been evaluated for the binary mixtures of C12MeImBr with drugs and triblock copolymers using Clint's, Rubingh's, and Motomura's approach. Thus the electrode offers a simple, straightforward and relatively fast technique for the characterization of micellar aggregates of C12MeImBr, complementing existing conventional techniques. Further, the analytical importance of proposed C12MeIm(+)-ISE as end point indicator in potentiometric titrations and for direct determination of cationic surfactants [cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), benzalkonium chloride (BC)] in some commercial products was judged by comparing statistically with classical two-phase titration methods. Copyright © 2013 Elsevier Inc. All rights reserved.

  10. Development of Novel Potentiometric Sensors for Determination of Lidocaine Hydrochloride in Pharmaceutical Preparations, Serum and Urine Samples

    PubMed Central

    Ali, Tamer Awad; Mohamed, Gehad Genidy; Yahya, Ghada A.

    2017-01-01

    This article is focused on the determination of lidocaine hydrochloride as a local anaesthetic drug. A potentiometric method based on modified screen-printed and modified carbon paste ion-selective electrodes was described for the determination of lidocaine hydrochloride in different pharmaceutical preparations and biological fluids (urine and serum). It was based on potentiometric titration of lidocaine hydrochloride using modified screen-printed and carbon paste electrodes as end point indicator sensors. The influences of the paste composition, different conditioning parameters and foreign ions on the electrodes performance were investigated and response times of the electrodes were studied. The electrodes showed Nernstian response of 58.9 and 57.5 mV decade-1 in the concentration range of 1×10-7–1×10-2 and 6.2×10-7–1×10-2 mol L-1 for modified screen-printed and carbon paste electrodes, respectively. The electrodes were found to be usable within the pH range of 2.0–8.0 and 2.0-7.5, exhibited a fast response time (about 6 and 4) low detection limit (1×10-7 and 6.2×10-7 mol L-1), long lifetime (6 and 4 months) and good stability for modified screen-printed (Electrode VII) and carbon paste electrodes (Electrode III), respectively. The electrodes were successfully applied for the determination of lidocaine hydrochloride in pure solutions, pharmaceutical preparation and biological fluids (urine and serum) samples. The results obtained applying these potentiometric electrodes were comparable with British pharmacopeia. The method validation parameters were optimized and the method can be applied for routine analysis of lidocaine hydrochloride drug. PMID:28979305

  11. Development of Novel Potentiometric Sensors for Determination of Lidocaine Hydrochloride in Pharmaceutical Preparations, Serum and Urine Samples.

    PubMed

    Ali, Tamer Awad; Mohamed, Gehad Genidy; Yahya, Ghada A

    2017-01-01

    This article is focused on the determination of lidocaine hydrochloride as a local anaesthetic drug. A potentiometric method based on modified screen-printed and modified carbon paste ion-selective electrodes was described for the determination of lidocaine hydrochloride in different pharmaceutical preparations and biological fluids (urine and serum). It was based on potentiometric titration of lidocaine hydrochloride using modified screen-printed and carbon paste electrodes as end point indicator sensors. The influences of the paste composition, different conditioning parameters and foreign ions on the electrodes performance were investigated and response times of the electrodes were studied. The electrodes showed Nernstian response of 58.9 and 57.5 mV decade -1 in the concentration range of 1×10 -7 -1×10 -2 and 6.2×10 -7 -1×10 -2 mol L -1 for modified screen-printed and carbon paste electrodes, respectively. The electrodes were found to be usable within the pH range of 2.0-8.0 and 2.0-7.5, exhibited a fast response time (about 6 and 4) low detection limit (1×10 -7 and 6.2×10 -7 mol L -1 ), long lifetime (6 and 4 months) and good stability for modified screen-printed (Electrode VII) and carbon paste electrodes (Electrode III), respectively. The electrodes were successfully applied for the determination of lidocaine hydrochloride in pure solutions, pharmaceutical preparation and biological fluids (urine and serum) samples. The results obtained applying these potentiometric electrodes were comparable with British pharmacopeia. The method validation parameters were optimized and the method can be applied for routine analysis of lidocaine hydrochloride drug.

  12. Potentiometric detection of chemical vapors using molecularly imprinted polymers as receptors

    PubMed Central

    Liang, Rongning; Chen, Lusi; Qin, Wei

    2015-01-01

    Ion-selective electrode (ISE) based potentiometric gas sensors have shown to be promising analytical tools for detection of chemical vapors. However, such sensors are only capable of detecting those vapors which can be converted into ionic species in solution. This paper describes for the first time a polymer membrane ISE based potentiometric sensing system for sensitive and selective determination of neutral vapors in the gas phase. A molecularly imprinted polymer (MIP) is incorporated into the ISE membrane and used as the receptor for selective adsorption of the analyte vapor from the gas phase into the sensing membrane phase. An indicator ion with a structure similar to that of the vapor molecule is employed to indicate the change in the MIP binding sites in the membrane induced by the molecular recognition of the vapor. The toluene vapor is used as a model and benzoic acid is chosen as its indicator. Coupled to an apparatus manifold for preparation of vapor samples, the proposed ISE can be utilized to determine volatile toluene in the gas phase and allows potentiometric detection down to parts per million levels. This work demonstrates the possibility of developing a general sensing principle for detection of neutral vapors using ISEs. PMID:26215887

  13. Two Analyte Calibration From The Transient Response Of Potentiometric Sensors Employed With The SIA Technique

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Cartas, Raul; Mimendia, Aitor; Valle, Manel del

    2009-05-23

    Calibration models for multi-analyte electronic tongues have been commonly built using a set of sensors, at least one per analyte under study. Complex signals recorded with these systems are formed by the sensors' responses to the analytes of interest plus interferents, from which a multivariate response model is then developed. This work describes a data treatment method for the simultaneous quantification of two species in solution employing the signal from a single sensor. The approach used here takes advantage of the complex information recorded with one electrode's transient after insertion of sample for building the calibration models for both analytes.more » The departure information from the electrode was firstly processed by discrete wavelet for transforming the signals to extract useful information and reduce its length, and then by artificial neural networks for fitting a model. Two different potentiometric sensors were used as study case for simultaneously corroborating the effectiveness of the approach.« less

  14. Novel potentiometric sensors for the determination of the dinotefuran insecticide residue levels in cucumber and soil samples.

    PubMed

    Abdel-Ghany, Maha F; Hussein, Lobna A; El Azab, Noha F

    2017-03-01

    Five new potentiometric membrane sensors for the determination of the dinotefuran levels in cucumber and soil samples have been developed. Four of these sensors were based on a newly designed molecularly imprinted polymer (MIP) material consisting of acrylamide or methacrylic acid as a functional monomer in a plasticized PVC (polyvinyl chloride) membrane before and after elution of the template. A fifth sensor, a carboxylated PVC-based sensor plasticized with dioctyl phthalate, was also prepared and tested. Sensor 1 (acrylamide washed) and sensor 3 (methacrylic acid washed) exhibited significantly enhanced responses towards dinotefuran over the concentration range of 10 -7 -10 -2 molL -1 . The limit of detection (LOD) for both sensors was 0.35µgL -1 . The response was near-Nernstian, with average slopes of 66.3 and 50.8mV/decade for sensors 1 and 3 respectively. Sensors 2 (acrylamide non-washed), 4 (methacrylic acid non-washed) and 5 (carboxylated-PVC) exhibited non-Nernstian responses over the concentration range of 10 -7 -10 -3 molL -1 , with LODs of 10.07, 6.90, and 4.30µgL -1 , respectively, as well as average slopes of 39.1, 27.2 and 33mV/decade, respectively. The application of the proposed sensors to the determination of the dinotefuran levels in spiked soil and cucumber samples was demonstrated. The average recoveries from the cucumber samples were from 7.93% to 106.43%, with a standard deviation of less than 13.73%, and recoveries from soil samples were from 97.46% to 108.71%, with a standard deviation of less than 10.66%. The sensors were applied successfully to the determination of the dinotefuran residue, its rate of disappearance and its half-life in cucumbers in soil in which a safety pre-harvest interval for dinotefuran was suggested. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Design and evaluation of potentiometric principles for bladder volume monitoring: a preliminary study.

    PubMed

    Chen, Shih-Ching; Hsieh, Tsung-Hsun; Fan, Wen-Jia; Lai, Chien-Hung; Chen, Chun-Lung; Wei, Wei-Feng; Peng, Chih-Wei

    2015-06-01

    Recent advances in microelectronics and wireless transmission technology have led to the development of various implantable sensors for real-time monitoring of bladder conditions. Although various sensing approaches for monitoring bladder conditions were reported, most such sensors have remained at the laboratory stage due to the existence of vital drawbacks. In the present study, we explored a new concept for monitoring the bladder capacity on the basis of potentiometric principles. A prototype of a potentiometer module was designed and fabricated and integrated with a commercial wireless transmission module and power unit. A series of in vitro pig bladder experiments was conducted to determine the best design parameters for implementing the prototype potentiometric device and to prove its feasibility. We successfully implemented the potentiometric module in a pig bladder model in vitro, and the error of the accuracy of bladder volume detection was <±3%. Although the proposed potentiometric device was built using a commercial wireless module, the design principles and animal experience gathered from this research can serve as a basis for developing new implantable bladder sensors in the future.

  16. Fluorinated tripodal receptors for potentiometric chloride detection in biological fluids.

    PubMed

    Pankratova, Nadezda; Cuartero, Maria; Jowett, Laura A; Howe, Ethan N W; Gale, Philip A; Bakker, Eric; Crespo, Gastón A

    2018-01-15

    Fluorinated tripodal compounds were recently reported to be efficient transmembrane transporters for a series of inorganic anions. In particular, this class of receptors has been shown to be suitable for the effective complexation of chloride, nitrate, bicarbonate and sulfate anions via hydrogen bonding. The potentiometric properties of urea and thiourea-based fluorinated tripodal receptors are explored here for the first time, in light of the need for reliable sensors for chloride monitoring in undiluted biological fluids. The ion selective electrode (ISE) membranes with tren-based tris-urea bis(CF 3 ) tripodal compound (ionophore I) were found to exhibit the best selectivity for chloride over major lipophilic anions such as salicylate ( [Formula: see text] ) and thiocyanate ( [Formula: see text] ). Ionophore I-based ISEs were successfully applied for chloride determination in undiluted human serum as well as artificial serum sample, the slope of the linear calibration at the relevant background of interfering ions being close to Nernstian (49.8±1.7mV). The results of potentiometric measurements were confirmed by argentometric titration. Moreover, the ionophore I-based ISE membrane was shown to exhibit a very good long-term stability of potentiometric performance over the period of 10 weeks. Nuclear magnetic resonance (NMR) titrations, potentiometric sandwich membrane experiments and density functional theory (DFT) computational studies were performed to determine the binding constants and suggest 1:1 complexation stoichiometry for the ionophore I with chloride as well as salicylate. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Eyeglasses based wireless electrolyte and metabolite sensor platform.

    PubMed

    Sempionatto, Juliane R; Nakagawa, Tatsuo; Pavinatto, Adriana; Mensah, Samantha T; Imani, Somayeh; Mercier, Patrick; Wang, Joseph

    2017-05-16

    The demand for wearable sensors has grown rapidly in recent years, with increasing attention being given to epidermal chemical sensing. Here, we present the first example of a fully integrated eyeglasses wireless multiplexed chemical sensing platform capable of real-time monitoring of sweat electrolytes and metabolites. The new concept has been realized by integrating an amperometric lactate biosensor and a potentiometric potassium ion-selective electrode into the two nose-bridge pads of the glasses and interfacing them with a wireless electronic backbone placed on the glasses' arms. Simultaneous real-time monitoring of sweat lactate and potassium levels with no apparent cross-talk is demonstrated along with wireless signal transduction. The electrochemical sensors were screen-printed on polyethylene terephthalate (PET) stickers and placed on each side of the glasses' nose pads in order to monitor sweat metabolites and electrolytes. The electronic backbone on the arms of the glasses' frame offers control of the amperometric and potentiometric transducers and enables Bluetooth wireless data transmission to the host device. The new eyeglasses system offers an interchangeable-sensor feature in connection with a variety of different nose-bridge amperometric and potentiometric sensor stickers. For example, the lactate bridge-pad sensor was replaced with a glucose one to offer convenient monitoring of sweat glucose. Such a fully integrated wireless "Lab-on-a-Glass" multiplexed biosensor platform can be readily expanded for the simultaneous monitoring of additional sweat electrolytes and metabolites.

  18. A High-Sensitivity Potentiometric 65-nm CMOS ISFET Sensor for Rapid E. coli Screening.

    PubMed

    Jiang, Yu; Liu, Xu; Dang, Tran Chien; Huang, Xiwei; Feng, Hao; Zhang, Qing; Yu, Hao

    2018-04-01

    Foodborne bacteria, inducing outbreaks of infection or poisoning, have posed great threats to food safety. Potentiometric sensors can identify bacteria levels in food by measuring medium's pH changes. However, most of these sensors face the limitation of low sensitivity and high cost. In this paper, we developed a high-sensitivity ion-sensitive field-effect transistor sensor. It is small sized, cost-efficient, and can be massively fabricated in a standard 65-nm complementary metal-oxide-semiconductor process. A subthreshold pH-to-time-to-voltage conversion scheme was proposed to improve the sensitivity. Furthermore, design parameters, such as chemical sensing area, transistor size, and discharging time, were optimized to enhance the performance. The intrinsic sensitivity of passivation membrane was calculated as 33.2 mV/pH. It was amplified to 123.8 mV/pH with a 0.01-pH resolution, which greatly exceeded 6.3 mV/pH observed in a traditional source-follower based readout structure. The sensing system was applied to Escherichia coli (E. coli) detection with densities ranging from 14 to 140 cfu/mL. Compared to the conventional direct plate counting method (24 h), more efficient sixfold smaller screening time (4 h) was achieved to differentiate samples' E. coli levels. The demonstrated portable, time-saving, and low-cost prescreen system has great potential for food safety detection.

  19. Potentiometric perchlorate determination at nanomolar concentrations in vegetables.

    PubMed

    Leoterio, Dilmo M S; Paim, Ana Paula S; Belian, Mônica F; Galembeck, André; Lavorante, André F; Pinto, Edgar; Amorim, Célia G; Araújo, Alberto N; Montenegro, Maria C B S M

    2017-07-15

    In this work, an expeditious method based on the multi-commutated flow-analysis concept with potentiometric detection is proposed to perform determinations of the emergent contaminant perchlorate in vegetable matrices down to nanomolar concentration. To accomplish the task, a tubular shaped potentiometric sensor selective to perchlorate ion was constructed with a PVC membrane containing 12mmol/kg of the polyamine bisnaphthalimidopropyl-4,4'-diaminodiphenylmethane and 2-nitrophenyl phenyl ether 68% (w/w) as plasticizer casted on a conductive epoxy resin. Under optimal flow conditions, the sensor responded linearly in the concentration range of 6.3×10 -7 -1.0×10 -3 mol/L perchlorate. In order to extend the determinations to lower concentrations (4.6(±1.3)×10 -10 mol/L perchlorate), a column packed with 70mg of sodium 2,5,8,11,14-pentaoxa-1-silacyclotetradecane-polymer was coupled to the flow-system thus enabling prior pre-concentration of the perchlorate. The proposed procedure provides a simpler alternative for the determination of perchlorate in foods, nowadays only allowed by sophisticated and expensive equipment and laborious methods. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Design of a Selective and Sensitive PVC-Membrane Potentiometric Sensor for Strontium Ion Based on 1,10-Diaza-5,6-benzo-4,7-dioxacyclohexadecane-2,9-dione as a Neutral Ionophore

    PubMed Central

    Shamsipur, Mojtaba; Kazemi, Sayed Yahya; Sharghi, Hashem

    2007-01-01

    A novel PVC membrane sensor for the Sr2+ ion based on 1,10-diaza-5,6-benzo-4,7-dioxacyclohexadecane-2,9-dione has been prepared. The sensor possesses a Nernstian slope of 30.0 ± 0.6 mV decade-1 over a wide linear concentration range of 1.6 × 10-6-3.0 ×10-3 M with a detection limit of 6.3 ×10-7 M. It has a fast response time of <15 s and can be used for at least two months without any considerable divergence in potential. The potentiometric response is independent of the pH of test solution in the pH range 4.3-9.4. The proposed electrode shows good selectivities over a variety of alkali, alkaline earth, and transition metal ions.

  1. Integrated, paper-based potentiometric electronic tongue for the analysis of beer and wine.

    PubMed

    Nery, Emilia Witkowska; Kubota, Lauro T

    2016-04-28

    The following manuscript details the stages of construction of a novel paper-based electronic tongue with an integrated Ag/AgCl reference, which can operate using a minimal amount of sample (40 μL). First, we optimized the fabrication procedure of silver electrodes, testing a set of different methodologies (electroless plating, use of silver nanoparticles and commercial silver paints). Later a novel, integrated electronic tongue system was assembled with the use of readily available materials such as paper, wax, lamination sheets, bleach etc. New system was thoroughly characterized and the ion-selective potentiometric sensors presented performance close to theoretical. An electronic tongue, composed of electrodes sensitive to sodium, calcium, ammonia and a cross-sensitive, anion-selective electrode was used to analyze 34 beer samples (12 types, 19 brands). This system was able to discriminate beers from different brands, and types, indicate presence of stabilizers and antioxidants, dyes or even unmalted cereals and carbohydrates added to the fermentation wort. Samples could be classified by type of fermentation (low, high) and system was able to predict pH and in part also alcohol content of tested beers. In the next step sample volume was minimalized by the use of paper sample pads and measurement in flow conditions. In order to test the impact of this advancement a four electrode system, with cross-sensitive (anion-selective, cation-selective, Ca(2+)/Mg(2+), K(+)/Na(+)) electrodes was applied for the analysis of 11 types of wine (4 types of grapes, red/white, 3 countries). Proposed matrix was able to group wines produced from different varieties of grapes (Chardonnay, Americanas, Malbec, Merlot) using only 40 μL of sample. Apart from that, storage stability studies were performed using a multimeter, therefore showing that not only fabrication but also detection can be accomplished by means of off-the-shelf components. This manuscript not only describes new

  2. Light-Addressable Potentiometric Sensors using ZnO Nanorods as the Sensor Substrate for Bioanalytical Applications.

    PubMed

    Tu, Ying; Ahmad, Norlaily; Briscoe, Joe; Zhang, De-Wen; Krause, Steffi

    2018-06-22

    Light-addressable potentiometric sensors (LAPS) are of great interest in bioimaging applications such as the monitoring of concentrations in microfluidic channels or the investigation of metabolic and signaling events in living cells. By measuring the photocurrents at electrolyte-insulator-semiconductor (EIS) and electrolyte-semiconductor structures, LAPS can produce spatiotemporal images of chemical or biological analytes, electrical potentials and impedance. However, its commercial applications are often restricted by their limited AC photocurrents and resolution of LAPS images. Herein, for the first time, the use of 1D semiconducting oxides in the form of ZnO nanorods for LAPS imaging is explored to solve this issue. A significantly increased AC photocurrent with enhanced image resolution has been achieved based on ZnO nanorods, with a photocurrent of 45.7 ± 0.1 nA at a light intensity of 0.05 mW, a lateral resolution as low as 3.0 μm as demonstrated by images of a PMMA dot on ZnO nanorods and a pH sensitivity of 53 mV/pH. The suitability of the device for bioanalysis and bioimaging was demonstrated by monitoring the degradation of a thin poly(ester amide) film with the enzyme α-chymotrypsin using LAPS. This simple and robust route to fabricate LAPS substrates with excellent performance would provide tremendous opportunities for bioimaging.

  3. Aptamer-based potentiometric measurements of proteins using ion-selective microelectrodes.

    PubMed

    Numnuam, Apon; Chumbimuni-Torres, Karin Y; Xiang, Yun; Bash, Ralph; Thavarungkul, Panote; Kanatharana, Proespichaya; Pretsch, Ernö; Wang, Joseph; Bakker, Eric

    2008-02-01

    We here report on the first example of an aptamer-based potentiometric sandwich assay of proteins. The measurements are based on CdS quantum dot labels of the secondary aptamer, which were determined with a novel solid-contact Cd2+-selective polymer membrane electrode after dissolution with hydrogen peroxide. The electrode exhibited cadmium ion detection limits of 100 pM in 100 mL samples and of 1 nM in 200 microL microwells, using a calcium-selective electrode as a pseudoreference electrode. As a prototype example, thrombin was measured in 200 microL samples with a lower detection limit of 0.14 nM corresponding to 28 fmol of analyte. The results show great promise for the potentiometric determination of proteins at very low concentrations in microliter samples.

  4. Recent Trends on Electrochemical Sensors Based on Ordered Mesoporous Carbon

    PubMed Central

    Walcarius, Alain

    2017-01-01

    The past decade has seen an increasing number of extensive studies devoted to the exploitation of ordered mesoporous carbon (OMC) materials in electrochemistry, notably in the fields of energy and sensing. The present review summarizes the recent achievements made in field of electroanalysis using electrodes modified with such nanomaterials. On the basis of comprehensive tables, the interest in OMC for designing electrochemical sensors is illustrated through the various applications developed to date. They include voltammetric detection after preconcentration, electrocatalysis (intrinsically due to OMC or based on suitable catalysts deposited onto OMC), electrochemical biosensors, as well as electrochemiluminescence and potentiometric sensors. PMID:28800106

  5. A Gas-Sensor-Based Urea Enzyme Electrode: Its Construction and Use in the Undergraduate Laboratory.

    ERIC Educational Resources Information Center

    Riechel, Thomas L.

    1984-01-01

    Describes an undergraduate experiment for the potentiometric determination of urea based on the physical entrapment of urease on the tip of an ammonia gas sensor. An advantage of this technique is the ease with which the ammonia electrode can be converted to a urea electrode. (JN)

  6. Linear air-fuel sensor development

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Garzon, F.; Miller, C.

    1996-12-14

    The electrochemical zirconia solid electrolyte oxygen sensor, is extensively used for monitoring oxygen concentrations in various fields. They are currently utilized in automobiles to monitor the exhaust gas composition and control the air-to-fuel ratio, thus reducing harmful emission components and improving fuel economy. Zirconia oxygen sensors, are divided into two classes of devices: (1) potentiometric or logarithmic air/fuel sensors; and (2) amperometric or linear air/fuel sensors. The potentiometric sensors are ideally suited to monitor the air-to-fuel ratio close to the complete combustion stoichiometry; a value of about 14.8 to 1 parts by volume. This occurs because the oxygen concentration changesmore » by many orders of magnitude as the air/fuel ratio is varied through the stoichiometric value. However, the potentiometric sensor is not very sensitive to changes in oxygen partial pressure away from the stoichiometric point due to the logarithmic dependence of the output voltage signal on the oxygen partial pressure. It is often advantageous to operate gasoline power piston engines with excess combustion air; this improves fuel economy and reduces hydrocarbon emissions. To maintain stable combustion away from stoichiometry, and enable engines to operate in the excess oxygen (lean burn) region several limiting-current amperometric sensors have been reported. These sensors are based on the electrochemical oxygen ion pumping of a zirconia electrolyte. They typically show reproducible limiting current plateaus with an applied voltage caused by the gas diffusion overpotential at the cathode.« less

  7. Rapid determination of cadmium in rice using an all-solid RGO-enhanced light addressable potentiometric sensor.

    PubMed

    Zhang, Wen; Xu, Yiwei; Zou, Xiaobo

    2018-09-30

    Herein, an all-solid light addressable potentiometric sensor (LAPS) is presented for determination of cadmium (Cd) in rice. On the working surface of the LAPS, reduced graphene oxide (RGO) is introduced as a part of ion-to-electron transducer to improve ionophore behaviors. The composite modification of RGO and ionophore is validated with scanning electron microscopy. The as-fabricated sensor presents a rapid response in less than 10 s to target Cd. Meanwhile, it shows lower noise (0.23 mV) and better limit of detection (0.002 mg L -1 ) than LAPS (control) without RGO modification (0.37 mV; 0.008 mg L -1 ). With the proposed method, satisfactory precision, accuracy and selectivity are also established. This method is adopted in an extensive survey for 25 rice samples from 5 regions in China. The results are in very good agreement with those obtained using inductively-coupled plasma-mass spectrometry. Copyright © 2018 Elsevier Ltd. All rights reserved.

  8. Potential transducers based man-tailored biomimetic sensors for selective recognition of dextromethorphan as an antitussive drug.

    PubMed

    El-Naby, Eman H; Kamel, Ayman H

    2015-09-01

    A biomimetic potentiometric sensor for specific recognition of dextromethorphan (DXM), a drug classified according to the Drug Enforcement Administration (DEA) as a "drug of concern", is designed and characterized. A molecularly imprinted polymer (MIP), with special molecular recognition properties of DXM, was prepared by thermal polymerization in which DXM acted as template molecule, methacrylic acid (MAA) and acrylonitrile (AN) acted as functional monomers in the presence of ethylene glycol dimethacrylate (EGDMA) as crosslinker. The sensors showed a high selectivity and a sensitive response to the template in aqueous system. Electrochemical evaluation of these sensors revealed near-Nernstian response with slopes of 49.6±0.5 and 53.4±0.5 mV decade(-1) with a detection limit of 1.9×10(-6), and 1.0×10(-6) mol L(-1) DXM with MIP/MAA and MIP/AN membrane based sensors, respectively. Significantly improved accuracy, precision, response time, stability, selectivity and sensitivity were offered by these simple and cost-effective potentiometric sensors compared with other standard techniques. The method has the requisite accuracy, sensitivity and precision to assay DXM in pharmaceutical products. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. Determination of the total acidity in soft drinks using potentiometric sequential injection titration.

    PubMed

    van Staden, J Koos F; Mashamba, M Mulalo G; Stefan, R Raluca I

    2002-12-06

    A potentiometric SI titration system for the determination of total acidity in soft drinks is proposed. The concept is based on the aspiration of the acid soft drink sample between two base zones into a holding coil with the volume of the first base zone twice to that of the second one and channelled by flow reversal through a reaction coil to a potentiometric sensor. A solution of 0.1 mol l(-1) sodium chloride is used as ionic strength adjustment buffer in the carrier stream. The system has been applied to the analysis of some South African soft drinks having a total acidity level of about 0.2-0.3% (w/v). The method has a sample frequency of 45 samples per h with a linear range of 0.1 and 0.6% (w/v). It is easy to use, fully computerised, and gives the results that are comparable to both automated batch titration and manual titration.

  10. YSZ-based sensor using Cr-Fe-based spinel-oxide electrodes for selective detection of CO.

    PubMed

    Anggraini, Sri Ayu; Fujio, Yuki; Ikeda, Hiroshi; Miura, Norio

    2017-08-22

    A selective carbon monoxide (CO) sensor was developed by the use of both of CuCrFeO 4 and CoCrFeO 4 as the sensing electrode (SE) for yttria-stabilized zirconia (YSZ)-based potentiometric sensor. The sensing-characteristic examinations of the YSZ-based sensors using each of spinel oxides as the single-SE sensor showed that CuCrFeO 4 -SE had the ability to detect CO, hydrocarbons and NO x gases, while CoCrFeO 4 -SE was sensitive to hydrocarbons and NO x gases. Thus, when both SEs were paired as a combined-SEs sensor, the resulting sensor could generate a selective response to CO at 450 °C under humid conditions. The sensor was also capable of detecting CO in the concentration range of 20-700 ppm. Its sensing mechanism that was examined via polarization-curve measurements was confirmed to be based on mixed-potential model. The CO response generated by the combined-SEs sensor was unaffected by the change of water vapor concentration in the range of 1.3-11.5 vol% H 2 O. Additionally, the sensing performance was stable during 13 days tested. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Label-free and substrate-free potentiometric aptasensing using polycation-sensitive membrane electrodes.

    PubMed

    Ding, Jiawang; Chen, Yan; Wang, Xuewei; Qin, Wei

    2012-02-21

    A potentiometric label-free and substrate-free (LFSF) aptasensing strategy which eliminates the labeling, separation, and immobilization steps is described in this paper. An aptamer binds specifically to a target molecule via reaction incubation, which could induce a change in the aptamer conformation from a random coil-like configuration to a rigid folded structure. Such a target binding-induced aptamer conformational change effectively prevents the aptamer from electrostatically interacting with the protamine binding domain. This could either shift the response curve for the potentiometric titration of the aptamer with protamine as monitored by a conventional polycation-sensitive membrane electrode or change the current-dependent potential detected by a protamine-conditioned polycation-sensitive electrode with the pulsed current-driven ion fluxes of protamine across the polymeric membrane. Using adenosine triphosphate (ATP) as a model analyte, the proposed concept offers potentiometric detection of ATP down to the submicromolar concentration range and has been applied to the determination of ATP in HeLa cells. In contrast to the current LFSF aptasensors based on optical detection, the proposed strategy allows the LFSF biosensing of aptamer/target binding events in a homogeneous solution via electrochemical transduction. It is anticipated that the proposed strategy will lay a foundation for development of potentiometric sensors for LFSF aptasensing of a variety of analytes where target binding-induced conformational changes such as the formation of folded structures and the opening of DNA hairpin loops are involved.

  12. New potentiometric and spectrophotometric methods for the determination of dextromethorphan in pharmaceutical preparations.

    PubMed

    Elmosallamy, Mohamed A F; Amin, Alaa S

    2014-01-01

    New, simple and convenient potentiometric and spectrophotometric methods are described for the determination of dextromethorphan hydrobromide (DXM) in pharmaceutical preparations. The potentiometric technique is based on developing a potentiometric sensor incorporating the dextromethorphan tetrakis(p-chlorophenyl)borate ion-pair complex as an electroactive species in a plasticized PVC matrix membrane with o-nitophenyl octyl ether or dioctyl phthalate. The sensor shows a rapid near Nernstian response of over 1 × 10(-5) - 1 × 10(-2) mol L(-1) dextromethorphan in the pH range of 3.0 - 9.0. The detection limit is 2 × 10(-6) mol L(-1) DXM and the response time is instantaneous (2 s). The proposed spectrophotometric technique involves the reaction of DXM with eriochrom black T (EBT) to form an ion-associate complex. Solvent extraction is used to improve the selectivity of the method. The optimal extraction and reaction conditions have been studied, and the analytical characteristics of the method have been obtained. Linearity is obeyed in the range of 7.37 - 73.7 × 10(-5) mol L(-1) DXM, and the detection limit of the method is 1.29 × 10(-5) mol L(-1). The relative standard deviation (RSD) and relative error for six replicate measurements of 3.685 × 10(-4) mol L(-1) are 0.672 and 0.855%, respectively. The interference effect of some excepients has also been tested. The drug contents in pharmaceutical preparations were successfully determined by the proposed methods by applying the standard-addition technique.

  13. Going Beyond, Going Further: Knives, Forks, and Beer Cans as Potentiometric Sensors.

    ERIC Educational Resources Information Center

    Selig, Walter S.

    1985-01-01

    Background information, materials needed, and procedures used are provided for potentiometric fluoride, halide, orthophosphate, and sulfate titrations. Typical results obtained are also provided for each type of titration. (JN)

  14. The Evolution of High Temperature Gas Sensors.

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Garzon, F. H.; Brosha, E. L.; Mukundan, R.

    2001-01-01

    Gas sensor technology based on high temperature solid electrolytes is maturing rapidly. Recent advances in metal oxide catalysis and thin film materials science has enabled the design of new electrochemical sensors. We have demonstrated prototype amperometric oxygen sensors, nernstian potentiometric oxygen sensors that operate in high sulfur environments, and hydrocarbon and carbon monoxide sensing mixed potentials sensors. Many of these devices exhibit part per million sensitivities, response times on the order of seconds and excellent long-term stability.

  15. Electrochemical sample matrix elimination for trace-level potentiometric detection with polymeric membrane ion-selective electrodes.

    PubMed

    Chumbimuni-Torres, Karin Y; Calvo-Marzal, Percy; Wang, Joseph; Bakker, Eric

    2008-08-01

    Potentiometric sensors are today sufficiently well understood and optimized to reach ultratrace level (subnanomolar) detection limits for numerous ions. In many cases of practical relevance, however, a high electrolyte background hampers the attainable detection limits. A particularly difficult sample matrix for potentiometric detection is seawater, where the high saline concentration forms a major interfering background and reduces the activity of most trace metals by complexation. This paper describes for the first time a hyphenated system for the online electrochemically modulated preconcentration and matrix elimination of trace metals, combined with a downstream potentiometric detection with solid contact polymeric membrane ion-selective microelectrodes. Following the preconcentration at the bismuth-coated electrode, the deposited metals are oxidized and released to a medium favorable to potentiometric detection, in this case calcium nitrate. Matrix interferences arising from the saline sample medium are thus circumvented. This concept is successfully evaluated with cadmium as a model trace element and offers potentiometric detection down to low parts per billion levels in samples containing 0.5 M NaCl background electrolyte.

  16. Electrochemical Sample Matrix Elimination for Trace Level Potentiometric Detection with Polymeric Membrane Ion-Selective Electrodes

    PubMed Central

    Chumbimuni-Torres, Karin Y.; Calvo-Marzal, Percy; Wang, Joseph; Bakker, Eric

    2008-01-01

    Potentiometric sensors are today sufficiently well understood and optimized to reach ultra-trace level (sub-nanomolar) detection limits for numerous ions. In many cases of practical relevance, however, a high electrolyte background hampers the attainable detection limits. A particularly difficult sample matrix for potentiometric detection is seawater, where the high saline concentration forms a major interfering background and reduces the activity of most trace metals by complexation. This paper describes for the first time a hyphenated system for the online electrochemically modulated preconcentration and matrix elimination (EMPM) of trace metals, combined with a downstream potentiometric detection with solid contact polymeric membrane ion-selective microelectrodes. Following the preconcentration at the bismuth coated electrodes, the deposited metals are oxidized and released to a medium favorable to potentiometric detection, in this case calcium nitrate. Matrix interferences arising from the saline sample medium are thus circumvented. This concept is successfully evaluated with cadmium as a model trace element and offers potentiometric detection down to low parts per billion levels in samples containing 0.5 M NaCl background electrolyte. PMID:18570385

  17. A Potentiometric Indirect Uric Acid Sensor Based on ZnO Nanoflakes and Immobilized Uricase

    PubMed Central

    Usman Ali, Syed M.; Ibupoto, Zafar Hussain; Kashif, Muhammad; Hashim, Uda; Willander, Magnus

    2012-01-01

    In the present work zinc oxide nanoflakes (ZnO-NF) structures with a wall thickness around 50 to 100 nm were synthesized on a gold coated glass substrate using a low temperature hydrothermal method. The enzyme uricase was electrostatically immobilized in conjunction with Nafion membrane on the surface of well oriented ZnO-NFs, resulting in a sensitive, selective, stable and reproducible uric acid sensor. The electrochemical response of the ZnO-NF-based sensor vs. a Ag/AgCl reference electrode was found to be linear over a relatively wide logarithmic concentration range (500 nM to 1.5 mM). In addition, the ZnO-NF structures demonstrate vast surface area that allow high enzyme loading which results provided a higher sensitivity. The proposed ZnO-NF array-based sensor exhibited a high sensitivity of ∼66 mV/ decade in test electrolyte solutions of uric acid, with fast response time. The sensor response was unaffected by normal concentrations of common interferents such as ascorbic acid, glucose, and urea. PMID:22736977

  18. Metabolic Study of Cancer Cells Using a pH Sensitive Hydrogel Nanofiber Light Addressable Potentiometric Sensor.

    PubMed

    Shaibani, Parmiss Mojir; Etayash, Hashem; Naicker, Selvaraj; Kaur, Kamaljit; Thundat, Thomas

    2017-01-27

    We report a simple, fast, and cost-effective approach that measures cancer cell metabolism and their response to anticancer drugs in real time. Using a Light Addressable Potentiometric Sensor integrated with pH sensitive hydrogel nanofibers (NF-LAPS), we detect localized changes in pH of the media as cancer cells consume glucose and release lactate. NF-LAPS shows a sensitivity response of 74 mV/pH for cancer cells. Cancer cells (MDA MB231) showed a response of ∼0.4 unit change in pH compared to virtually no change observed for normal cells (MCF10A). We also observed a drop in pH for the multidrug-resistant cancer cells (MDA-MB-435MDR) in the presence of doxorubicin. However, inhibition of the metabolic enzymes such as hexokinase and lactate dehydrogenase-A suggested an improvement in the efficacy of doxorubicin by decreasing the level of acidification. This approach, based on extracellular acidification, enhances our understanding of cancer cell metabolic modes and their response to chemotherapies, which will help in the development of better treatments, including choice of drugs and dosages.

  19. Solute transport in streams of varying morphology inferred from a high resolution network of potentiometric wireless chloride sensors

    NASA Astrophysics Data System (ADS)

    Klaus, Julian; Smettem, Keith; Pfister, Laurent; Harris, Nick

    2017-04-01

    There is ongoing interest in understanding and quantifying the travel times and dispersion of solutes moving through stream environments, including the hyporheic zone and/or in-channel dead zones where retention affects biogeochemical cycling processes that are critical to stream ecosystem functioning. Modelling these transport and retention processes requires acquisition of tracer data from injection experiments where the concentrations are recorded downstream. Such experiments are often time consuming and costly, which may be the reason many modelling studies of chemical transport have tended to rely on relatively few well documented field case studies. This leads to the need of fast and cheap distributed sensor arrays that respond instantly and record chemical transport at points of interest on timescales of seconds at various locations in the stream environment. To tackle this challenge we present data from several tracer experiments carried out in the Attert river catchment in Luxembourg employing low-cost (in the order of a euro per sensor) potentiometric chloride sensors in a distributed array. We injected NaCl under various baseflow conditions in streams of different morphologies and observed solute transport at various distances and locations. This data is used to benchmark the sensors to data obtained from more expensive electrical conductivity meters. Furthermore, the data allowed spatial resolution of hydrodynamic mixing processes and identification of chemical 'dead zones' in the study reaches.

  20. An on-line potentiometric sequential injection titration process analyser for the determination of acetic acid.

    PubMed

    van Staden, J F; Mashamba, Mulalo G; Stefan, Raluca I

    2002-09-01

    An on-line potentiometric sequential injection titration process analyser for the determination of acetic acid is proposed. A solution of 0.1 mol L(-1) sodium chloride is used as carrier. Titration is achieved by aspirating acetic acid samples between two strong base-zone volumes into a holding coil and by channelling the stack of well-defined zones with flow reversal through a reaction coil to a potentiometric sensor where the peak widths were measured. A linear relationship between peak width and logarithm of the acid concentration was obtained in the range 1-9 g/100 mL. Vinegar samples were analysed without any sample pre-treatment. The method has a relative standard deviation of 0.4% with a sample frequency of 28 samples per hour. The results revealed good agreement between the proposed sequential injection and an automated batch titration method.

  1. Perception of olive oils sensory defects using a potentiometric taste device.

    PubMed

    Veloso, Ana C A; Silva, Lucas M; Rodrigues, Nuno; Rebello, Ligia P G; Dias, Luís G; Pereira, José A; Peres, António M

    2018-01-01

    The capability of perceiving olive oils sensory defects and intensities plays a key role on olive oils quality grade classification since olive oils can only be classified as extra-virgin if no defect can be perceived by a human trained sensory panel. Otherwise, olive oils may be classified as virgin or lampante depending on the median intensity of the defect predominantly perceived and on the physicochemical levels. However, sensory analysis is time-consuming and requires an official sensory panel, which can only evaluate a low number of samples per day. In this work, the potential use of an electronic tongue as a taste sensor device to identify the defect predominantly perceived in olive oils was evaluated. The potentiometric profiles recorded showed that intra- and inter-day signal drifts could be neglected (i.e., relative standard deviations lower than 25%), being not statistically significant the effect of the analysis day on the overall recorded E-tongue sensor fingerprints (P-value = 0.5715, for multivariate analysis of variance using Pillai's trace test), which significantly differ according to the olive oils' sensory defect (P-value = 0.0084, for multivariate analysis of variance using Pillai's trace test). Thus, a linear discriminant model based on 19 potentiometric signal sensors, selected by the simulated annealing algorithm, could be established to correctly predict the olive oil main sensory defect (fusty, rancid, wet-wood or winey-vinegary) with average sensitivity of 75 ± 3% and specificity of 73 ± 4% (repeated K-fold cross-validation variant: 4 folds×10 repeats). Similarly, a linear discriminant model, based on 24 selected sensors, correctly classified 92 ± 3% of the olive oils as virgin or lampante, being an average specificity of 93 ± 3% achieved. The overall satisfactory predictive performances strengthen the feasibility of the developed taste sensor device as a complementary methodology for olive oils' defects analysis and subsequent

  2. Ground-water-level monitoring, basin boundaries, and potentiometric surfaces of the aquifer system at Edwards Air Force Base, California, 1992

    USGS Publications Warehouse

    Rewis, D.L.

    1995-01-01

    A ground-water-level monitoring program was implemented at Edwards Air Force Base, California, from January through December 1992 to monitor spatial and temporal changes in poten-tiometric surfaces that largely are affected by ground-water pumping. Potentiometric-surface maps are needed to determine the correlation between declining ground- water levels and the distribution of land subsidence. The monitoring program focused on areas of the base where pumping has occurred, especially near Rogers Lake, and involved three phases of data collection: (1) well canvassing and selection, (2) geodetic surveys, and (3) monthly ground-water-level measurements. Construction and historical water- level data were compiled for 118 wells and pi-ezometers on or near the base, and monthly ground-water-level measurements were made in 82 wells and piezometers on the base. The compiled water-level data were used in conjunction with previously collected geologic data to identify three types of no-flow boundaries in the aquifer system: structural boundaries, a principal-aquifer boundary, and ground-water divides. Heads were computed from ground-water-level measurements and land-surface altitudes and then were used to map seasonal potentiometric surfaces for the principal and deep aquifers underlying the base. Pumping has created a regional depression in the potentiometric surface of the deep aquifer in the South Track, South Base, and Branch Park well-field area. A 15-foot decline in the potentiometric surface from April to September 1992 and 20- to 30-foot drawdowns in the three production wells in the South Track well field caused locally unconfined conditions in the deep aquifer.

  3. Potentiometric NO2 Sensors Based on Thin Stabilized Zirconia Electrolytes and Asymmetric (La0.8Sr0.2)0.95MnO3 Electrodes

    PubMed Central

    Zou, Jie; Zheng, Yangong; Li, Junliang; Zhan, Zhongliang; Jian, Jiawen

    2015-01-01

    Here we report on a new architecture for potentiometric NO2 sensors that features thin 8YSZ electrolytes sandwiched between two porous (La0.8Sr0.2)0.95MnO3 (LSM95) layers—one thick and the other thin—fabricated by the tape casting and co-firing techniques. Measurements of their sensing characteristics show that reducing the porosity of the supporting LSM95 reference electrodes can increase the response voltages. In the meanwhile, thin LSM95 layers perform better than Pt as the sensing electrode since the former can provide higher response voltages and better linear relationship between the sensitivities and the NO2 concentrations over 40–1000 ppm. The best linear coefficient can be as high as 0.99 with a sensitivity value of 52 mV/decade as obtained at 500 °C. Analysis of the sensing mechanism suggests that the gas phase reactions within the porous LSM95 layers are critically important in determining the response voltages. PMID:26205270

  4. Fusion of Potentiometric & Voltammetric Electronic Tongue for Classification of Black Tea Taste based on Theaflavins (TF) Content

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Nabarun; Legin, Andrey; Papieva, Irina; Sarkar, Subrata; Kirsanov, Dmitry; Kartsova, Anna; Ghosh, Arunangshu; Bandyopadhyay, Rajib

    2011-09-01

    Black tea is an extensively consumed beverage worldwide with an expanding market. The final quality of black tea depends upon number of chemical compounds present in the tea. Out of these compounds, theaflavins (TF), which is responsible for astringency in black tea, plays an important role in determining the final taste of the finished black tea. The present paper reports our effort to correlate the theaflavins contents with the voltammetric and potentiometric electronic tongue (e-tongue) data. Noble metal-based electrode array has been used for collecting data though voltammetric electronic tongue where as liquid filled membrane based electrodes have been used for potentiometric electronic tongue. Black tea samples with tea taster score and biochemical results have been collected from Tea Research Association, Tocklai, India for the analysis purpose. In this paper, voltammetric and potentiometric e-tongue responses are combined to demonstrate improvement of cluster formation among tea samples with different ranges of TF values.

  5. Zinc Oxide-Based Self-Powered Potentiometric Chemical Sensors for Biomolecules and Metal Ions.

    PubMed

    Israr-Qadir, Muhammad; Jamil-Rana, Sadaf; Nur, Omer; Willander, Magnus

    2017-07-19

    Advances in the miniaturization and portability of the chemical sensing devices have always been hindered by the external power supply problem, which has focused new interest in the fabrication of self-powered sensing devices for disease diagnosis and the monitoring of analytes. This review describes the fabrication of ZnO nanomaterial-based sensors synthesized on different conducting substrates for extracellular detection, and the use of a sharp borosilicate glass capillary (diameter, d = 700 nm) to grow ZnO nanostructures for intracellular detection purposes in individual human and frog cells. The electrocatalytic activity and fast electron transfer properties of the ZnO materials provide the necessary energy to operate as well as a quick sensing device output response, where the role of the nanomorphology utilized for the fabrication of the sensor is crucial for the production of the operational energy. Simplicity, design, cost, sensitivity, selectivity and a quick and stable response are the most important features of a reliable sensor for routine applications. The review details the extra- and intra-cellular applications of the biosensors for the detection and monitoring of different metallic ions present in biological matrices, along with the biomolecules glucose and cholesterol.

  6. Zinc Oxide-Based Self-Powered Potentiometric Chemical Sensors for Biomolecules and Metal Ions

    PubMed Central

    Israr-Qadir, Muhammad; Jamil-Rana, Sadaf; Nur, Omer; Willander, Magnus

    2017-01-01

    Advances in the miniaturization and portability of the chemical sensing devices have always been hindered by the external power supply problem, which has focused new interest in the fabrication of self-powered sensing devices for disease diagnosis and the monitoring of analytes. This review describes the fabrication of ZnO nanomaterial-based sensors synthesized on different conducting substrates for extracellular detection, and the use of a sharp borosilicate glass capillary (diameter, d = 700 nm) to grow ZnO nanostructures for intracellular detection purposes in individual human and frog cells. The electrocatalytic activity and fast electron transfer properties of the ZnO materials provide the necessary energy to operate as well as a quick sensing device output response, where the role of the nanomorphology utilized for the fabrication of the sensor is crucial for the production of the operational energy. Simplicity, design, cost, sensitivity, selectivity and a quick and stable response are the most important features of a reliable sensor for routine applications. The review details the extra- and intra-cellular applications of the biosensors for the detection and monitoring of different metallic ions present in biological matrices, along with the biomolecules glucose and cholesterol. PMID:28753916

  7. Kinetic Modulation of Pulsed Chrono-potentiometric Polymeric Membrane Ion Sensors by Polyelectrolyte Multilayers

    PubMed Central

    Xu, Yida; Xu, Chao; Shvarev, Alexey; Becker, Thomas; De Marco, Roland

    2010-01-01

    Polymeric membrane ion selective electrodes are normally interrogated by zero current potentiometry, and their selectivity is understood to be primarily dependent on an extraction/ion-exchange equilibrium between the aqueous sample and polymeric membrane. If concentration gradients in the contacting diffusion layers are insubstantial, the membrane response is thought to be rather independent of kinetic processes such as surface blocking effects. In this work, the surface of calcium-selective polymeric ion-selective electrodes is coated with polyelectrolyte multilayers as evidenced by zeta potential measurements, atomic force microscopy and electrochemical impedance spectroscopy. Indeed, such multilayers have no effect on their potentiometric response if the membranes are formulated in a traditional manner, containing a lipophilic ion-exchanger and a calcium-selective ionophore. However, drastic changes in the potential response are observed if the membranes are operated in a recently introduced kinetic mode using pulsed chronopotentiometry. The results suggest that the assembled nanostructured multilayers drastically alter the kinetics of ion transport to the sensing membrane, making use of the effect that polyelectrolyte multilayers have different permeabilities toward ions with different valences. The results have implications to the design of chemically selective ion sensors since surface localized kinetic limitations can now be used as an additional dimension to tune the operational ion selectivity. PMID:17711298

  8. Pulsating potentiometric titration technique for assay of dissolved oxygen in water at trace level.

    PubMed

    Sahoo, P; Ananthanarayanan, R; Malathi, N; Rajiniganth, M P; Murali, N; Swaminathan, P

    2010-06-11

    A simple but high performance potentiometric titration technique using pulsating sensors has been developed for assay of dissolved oxygen (DO) in water samples down to 10.0 microg L(-1) levels. The technique involves Winkler titration chemistry, commonly used for determination of dissolved oxygen in water at mg L(-1) levels, with modification in methodology for accurate detection of end point even at 10.0 microg L(-1) levels DO present in the sample. An indigenously built sampling cum pretreatment vessel has been deployed for collection and chemical fixing of dissolved oxygen in water samples from flowing water line without exposure to air. A potentiometric titration facility using pulsating sensors developed in-house is used to carry out titration. The power of the titration technique has been realised in estimation of very dilute solution of iodine equivalent to 10 microg L(-1) O(2). Finally, several water samples containing dissolved oxygen from mg L(-1) to microg L(-1) levels were successfully analysed with excellent reproducibility using this new technique. The precision in measurement of DO in water at 10 microg L(-1) O(2) level is 0.14 (n=5), RSD: 1.4%. Probably for the first time a potentiometric titration technique has been successfully deployed for assay of dissolved oxygen in water samples at 10 microg L(-1) levels. Copyright 2010 Elsevier B.V. All rights reserved.

  9. A novel approach for high precision rapid potentiometric titrations: application to hydrazine assay.

    PubMed

    Sahoo, P; Malathi, N; Ananthanarayanan, R; Praveen, K; Murali, N

    2011-11-01

    We propose a high precision rapid personal computer (PC) based potentiometric titration technique using a specially designed mini-cell to carry out redox titrations for assay of chemicals in quality control laboratories attached to industrial, R&D, and nuclear establishments. Using this technique a few microlitre of sample (50-100 μl) in a total volume of ~2 ml solution can be titrated and the waste generated after titration is extremely low comparing to that obtained from the conventional titration technique. The entire titration including online data acquisition followed by immediate offline analysis of data to get information about concentration of unknown sample is completed within a couple of minutes (about 2 min). This facility has been created using a new class of sensors, viz., pulsating sensors developed in-house. The basic concept in designing such instrument and the salient features of the titration device are presented in this paper. The performance of the titration facility was examined by conducting some of the high resolution redox titrations using dilute solutions--hydrazine against KIO(3) in HCl medium, Fe(II) against Ce(IV) and uranium using Davies-Gray method. The precision of titrations using this innovative approach lies between 0.048% and 1.0% relative standard deviation in different redox titrations. With the evolution of this rapid PC based titrator it was possible to develop a simple but high precision potentiometric titration technique for quick determination of hydrazine in nuclear fuel dissolver solution in the context of reprocessing of spent nuclear fuel in fast breeder reactors. © 2011 American Institute of Physics

  10. A novel approach for high precision rapid potentiometric titrations: Application to hydrazine assay

    NASA Astrophysics Data System (ADS)

    Sahoo, P.; Malathi, N.; Ananthanarayanan, R.; Praveen, K.; Murali, N.

    2011-11-01

    We propose a high precision rapid personal computer (PC) based potentiometric titration technique using a specially designed mini-cell to carry out redox titrations for assay of chemicals in quality control laboratories attached to industrial, R&D, and nuclear establishments. Using this technique a few microlitre of sample (50-100 μl) in a total volume of ˜2 ml solution can be titrated and the waste generated after titration is extremely low comparing to that obtained from the conventional titration technique. The entire titration including online data acquisition followed by immediate offline analysis of data to get information about concentration of unknown sample is completed within a couple of minutes (about 2 min). This facility has been created using a new class of sensors, viz., pulsating sensors developed in-house. The basic concept in designing such instrument and the salient features of the titration device are presented in this paper. The performance of the titration facility was examined by conducting some of the high resolution redox titrations using dilute solutions--hydrazine against KIO3 in HCl medium, Fe(II) against Ce(IV) and uranium using Davies-Gray method. The precision of titrations using this innovative approach lies between 0.048% and 1.0% relative standard deviation in different redox titrations. With the evolution of this rapid PC based titrator it was possible to develop a simple but high precision potentiometric titration technique for quick determination of hydrazine in nuclear fuel dissolver solution in the context of reprocessing of spent nuclear fuel in fast breeder reactors.

  11. A selective iodide ion sensor electrode based on functionalized ZnO nanotubes.

    PubMed

    Ibupoto, Zafar Hussain; Khun, Kimleang; Willander, Magnus

    2013-02-04

    In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the electromotive force (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concentrations (1 × 10-6 to 1 × 10-1 M) and excellent sensitivity of -62 ± 1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10-7 M. The effects of pH, temperature, additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of less than 5 s and high selectivity against common organic and the inorganic anions. All the obtained results revealed that the iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of iodide ion in environmental water samples, pharmaceutical products and other real samples.

  12. A Selective Iodide Ion Sensor Electrode Based on Functionalized ZnO Nanotubes

    PubMed Central

    Ibupoto, Zafar Hussain; Khun, Kimleang; Willander, Magnus

    2013-01-01

    In this research work, ZnO nanotubes were fabricated on a gold coated glass substrate through chemical etching by the aqueous chemical growth method. For the first time a nanostructure-based iodide ion selective electrode was developed. The ZnO nanotubes were functionalized with miconazole ion exchanger and the electromotive force (EMF) was measured by the potentiometric method. The iodide ion sensor exhibited a linear response over a wide range of concentrations (1 × 10−6 to 1 × 10−1 M) and excellent sensitivity of −62 ± 1 mV/decade. The detection limit of the proposed sensor was found to be 5 × 10−7 M. The effects of pH, temperature, additive, plasticizer and stabilizer on the potential response of iodide ion selective electrode were also studied. The proposed iodide ion sensor demonstrated a fast response time of less than 5 s and high selectivity against common organic and the inorganic anions. All the obtained results revealed that the iodide ion sensor based on functionalized ZnO nanotubes may be used for the detection of iodide ion in environmental water samples, pharmaceutical products and other real samples. PMID:23385412

  13. Multiwalled carbon nanotube based molecular imprinted polymer for trace determination of 2,4-dichlorophenoxyaceticacid in natural water samples using a potentiometric method

    NASA Astrophysics Data System (ADS)

    Anirudhan, Thayyath S.; Alexander, Sheeba

    2014-06-01

    A novel potentiometric sensor based on ion imprinted polymer inclusion membrane (IPIM) was prepared from the modification of multiwalled carbon nanotube (MWCNT) based molecularly imprinted polymer for the trace determination of the pesticide 2,4-D (2,4-dichlorophenoxyacetic acid) in natural water samples. MWCNTs are initially functionalized with vinyl groups through nitric acid oxidation along with reacting by allylamine. MWCNT based imprinted polymer (MWCNT-MIP) was synthesized by means of methacrylic acid (MAA) as the monomer, trimethylol propane trimethacrylate (TRIM) as the cross linker, α,α‧-azobisisobutyronitrile (AIBN) as the initiator and 2,4-D an organochlorine pesticide molecule as the template. Organized material was characterized by means of FTIR, XRD and SEM analyses. The sensing membrane was developed by the inclusion of 2,4-D imprinted polymer materials in the polyvinyl chloride (PVC) matrix. The optimization of operational parameters normally used such as amount and nature of plasticizers sensing material, pH and response time was conducted. From the non-imprinted (NIPIM) and imprinted polymer inclusion membrane (IPIM) sensors the response behavior of 2,4-D was compared under optimum conditions. The IPIM sensor responds in the range of 1 × 10-9-1 × 10-5 M and the detection limit was found to be 1.2 × 10-9 M. The stability of MWCNT-IPIM sensor was checked by various methods and it is found to be 3 months and it can be reused many times without losing its sensitivity. For the application of sensor experiments with ground and tap water samples were performed.

  14. Ionophore-based potentiometric PVC membrane sensors for determination of phenobarbitone in pharmaceutical formulations.

    PubMed

    Alrabiah, Haitham; Al-Majed, Abdulrahman; Abounassif, Mohammed; Mostafa, Gamal A E

    2016-12-01

    The fabrication and development of two polyvinyl chloride (PVC) membrane sensors for assaying phenobarbitone sodium are described. Sensors 1 and 2 were fabricated utilizing β- or γ-cyclodextrin as ionophore in the presence of tridodecylmethylammonium chloride as a membrane additive, and PVC and dioctyl phthalate as plasticizer. The analytical parameters of both sensors were evaluated according to the IUPAC guidelines. The proposed sensors showed rapid, stable anionic response (-59.1 and -62.0 mV per decade) over a relatively wide phenobarbitone concentration range (5.0 × 10-6-1 × 10-2 and 8 × 10-6-1 × 10-2 mol L-1) in the pH range of 9-11. The limit of detection was 3.5 × 10-6 and 7.0 × 10-6 mol L-1 for sensors 1 and 2, respectively. The fabricated sensors showed high selectivity for phenobarbitone over the investigated foreign species. An average recovery of 2.54 μg mL-1 phenobarbitone sodium was 97.4 and 101.1 %, while the mean relative standard deviation was 3.0 and 2.1 %, for sensors 1 and 2, respectively. The results acquired for determination of phenobarbitone in its dosage forms utilizing the proposed sensors are in good agreement with those obtained by the British Pharmacopoeial method.

  15. Solution and fluorescence properties of symmetric dipicolylamine-containing dichlorofluorescein-based Zn2+ sensors.

    PubMed

    Wong, Brian A; Friedle, Simone; Lippard, Stephen J

    2009-05-27

    The mechanism by which dipicolylamine (DPA) chelate-appended fluorophores respond to zinc was investigated by the synthesis and study of five new analogues of the 2',7'-dichlorofluorescein-based Zn(2+) sensor Zinpyr-1 (ZP1). With the use of absorption and emission spectroscopy in combination with potentiometric titrations, a detailed molecular picture has emerged of the Zn(2+) and H(+) binding properties of the ZP1 family of sensors. The two separate N(3)O donor atom sets on ZP1 converge to form binding pockets in which all four heteroatoms participate in coordination to either Zn(2+) or protons. The position of the pyridyl group nitrogen atom, 2-pyridyl or 4-pyridyl, has a large impact on the fluorescence response of the dyes to protons despite relatively small changes in pK(a) values. The fluorescence quenching effects of such multifunctional electron-donating units are often taken as a whole. Despite the structural complexity of ZP1, however, we provide evidence that the pyridyl arms of the DPA appendages participate in the quenching process, in addition to the contribution from the tertiary nitrogen amine atom. Potentiometric titrations reveal ZP1 dissociation constants (K(d)) for Zn(2+) of 0.04 pM and 1.2 nM for binding to the first and second binding pockets of the ligand, respectively, the second of which correlates with the value observed by fluorescence titration. This result demonstrates that both binding pockets of this symmetric, ditopic sensor need to be occupied in order for full fluorescence turn-on to be achieved. These results have significant implications for the design and implementation of fluorescent sensors for studies of mobile zinc ions in biology.

  16. Label-free detection of DNA using a light-addressable potentiometric sensor modified with a positively charged polyelectrolyte layer

    NASA Astrophysics Data System (ADS)

    Wu, Chunsheng; Bronder, Thomas; Poghossian, Arshak; Werner, Carl Frederik; Schöning, Michael J.

    2015-03-01

    A multi-spot (16 spots) light-addressable potentiometric sensor (MLAPS) consisting of an Al-p-Si-SiO2 structure modified with a weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was applied for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization and hybridization by the intrinsic molecular charge for the first time. To achieve a preferentially flat orientation of DNA strands and thus, to reduce the distance between the DNA charge and MLAPS surface, the negatively charged probe single-stranded DNAs (ssDNA) were electrostatically adsorbed onto the positively charged PAH layer using a simple layer-by-layer (LbL) technique. In this way, more DNA charge can be positioned within the Debye length, yielding a higher sensor signal. The surface potential changes in each spot induced due to the surface modification steps (PAH adsorption, probe ssDNA immobilization, hybridization with complementary target DNA (cDNA), non-specific adsorption of mismatched ssDNA) were determined from the shifts of photocurrent-voltage curves along the voltage axis. A high sensor signal of 83 mV was registered after immobilization of probe ssDNA onto the PAH layer. The hybridization signal increases from 5 mV to 32 mV with increasing the concentration of cDNA from 0.1 nM to 5 μM. In contrast, a small signal of 5 mV was recorded in the case of non-specific adsorption of fully mismatched ssDNA (5 μM). The obtained results demonstrate the potential of the MLAPS in combination with the simple and rapid LbL immobilization technique as a promising platform for the future development of multi-spot light-addressable label-free DNA chips with direct electrical readout.A multi-spot (16 spots) light-addressable potentiometric sensor (MLAPS) consisting of an Al-p-Si-SiO2 structure modified with a weak polyelectrolyte layer of PAH (poly(allylamine hydrochloride)) was applied for the label-free electrical detection of DNA (deoxyribonucleic acid) immobilization

  17. Rapid and Automated Analytical Methods for Redox Species Based on Potentiometric Flow Injection Analysis Using Potential Buffers

    PubMed Central

    Ohura, Hiroki; Imato, Toshihiko

    2011-01-01

    Two analytical methods, which prove the utility of a potentiometric flow injection technique for determining various redox species, based on the use of some redox potential buffers, are reviewed. The first is a potentiometric flow injection method in which a redox couple such as Fe(III)-Fe(II), Fe(CN)6 3−-Fe(CN)(CN)6 4−, and bromide-bromine and a redox electrode or a combined platinum-bromide ion selective electrode are used. The analytical principle and advantages of the method are discussed, and several examples of its application are reported. Another example is a highly sensitive potentiometric flow injection method, in which a large transient potential change due to bromine or chlorine as an intermediate, generated during the reaction of the oxidative species with an Fe(III)-Fe(II) potential buffer containing bromide or chloride, is utilized. The analytical principle and details of the proposed method are described, and examples of several applications are described. The determination of trace amounts of hydrazine, based on the detection of a transient change in potential caused by the reaction with a Ce(IV)-Ce(III) potential buffer, is also described. PMID:21584280

  18. Dual functional extracellular recording using a light-addressable potentiometric sensor for bitter signal transduction.

    PubMed

    Du, Liping; Wang, Jian; Chen, Wei; Zhao, Luhang; Wu, Chunsheng; Wang, Ping

    2018-08-31

    This paper presents a dual functional extracellular recording biosensor based on a light-addressable potentiometric sensor (LAPS). The design and fabrication of this biosensor make it possible to record both extracellular membrane potential changes and ATP release from a single taste bud cell for the first time. For detecting ATP release, LAPS chip was functionalized with ATP-sensitive DNA aptamer by covalent immobilization. Taste bud cells isolated from rat were cultured on LAPS surface. When the desired single taste bud cell was illuminated by modulated light, ATP release from single taste bud cells can be measured by recording the shifts of bias voltage-photocurrent curves (I-V curves) when the LAPS chip is working in discrete mode. On the other hand, extracellular membrane potential changes can be monitored by recording the fluctuation of LAPS photocurrent when the LAPS chip is working in continuous mode. The results show this biosensor can effectively record the enhancive effect of the bitter substance and inhibitory effect of the carbenoxolone (CBX) on the extracellular membrane potential changes and ATP release of single taste bud cells. In addition, the inhibitory effect of CBX also confirms LAPS extracellular recordings are originated from bitter signal transduction. It is proved this biosensor is suitable for extracellular recording of ATP release and membrane potential changes of single taste bud cells. It is suggested this biosensor could be applied to investigating taste signal transduction at the single-cell level as well as applied to other types of cells which have similar functions to taste bud cells. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Determination of sulfur compounds in hydrotreated transformer base oil by potentiometric titration.

    PubMed

    Chao, Qiu; Sheng, Han; Cheng, Xingguo; Ren, Tianhui

    2005-06-01

    A method was developed to analyze the distribution of sulfur compounds in model sulfur compounds by potentiometric titration, and applied to analyze hydrotreated transformer base oil. Model thioethers were oxidized to corresponding sulfoxides by tetrabutylammonium periodate and sodium metaperiodate, respectively, and the sulfoxides were titrated by perchloric acid titrant in acetic anhydride. The contents of aliphatic thioethers and total thioethers were then determined from that of sulfoxides in solution. The method was applied to determine the organic sulfur compounds in hydrotreated transformer base oil.

  20. A New Electrochemical Sensor Based on Task-Specific Ionic Liquids-Modified Palm Shell Activated Carbon for the Determination of Mercury in Water Samples

    PubMed Central

    Ismaiel, Ahmed Abu; Aroua, Mohamed Kheireddine; Yusoff, Rozita

    2014-01-01

    In this study, a potentiometric sensor composed of palm shell activated carbon modified with trioctylmethylammonium thiosalicylate (TOMATS) was used for the potentiometric determination of mercury ions in water samples. The proposed potentiometric sensor has good operating characteristics towards Hg (II), including a relatively high selectivity; a Nernstian response to Hg (II) ions in a concentration range of 1.0 × 10−9 to 1.0 × 10−2 M, with a detection limit of 1 × 10−10 M and a slope of 44.08 ± 1.0 mV/decade; and a fast response time (∼5 s). No significant changes in electrode potential were observed when the pH was varied over the range of 3–9. Additionally, the proposed electrode was characterized by good selectivity towards Hg (II) and no significant interferences from other cationic or anionic species. PMID:25051034

  1. Development of a novel MWCNTs-triazene-modified carbon paste electrode for potentiometric assessment of Hg(II) in the aquatic environments.

    PubMed

    Mashhadizadeh, Mohammad Hossein; Ramezani, Soleyman; Rofouei, Mohammad Kazem

    2015-02-01

    In this approach, a new chemically modified carbon paste electrode was assembled for potentiometric assay of mercury(II) ion in the aqueous environments. Hereby, MWCNTs were used in the carbon paste composition to meliorate the electrical conductivity and sensitivity of the carbon paste owing to its exceptional physicochemical characteristics. Likewise, participation of the BEPT as a super-selective ionophore in the carbon paste composition boosted significantly the selectivity of the modified electrode towards Hg(II) ions over a wide concentration range of 4.0 × 10(-9)-2.2 × 10(-3) mol L(-1) with a lower detection limit of 3.1 × 10(-9) mol L(-1). Besides, Nernstian slope of the proposed sensor was 28.9(± 0.4)mV/decade over a pH range of 3.0-5.2 with potentiometric short response time of 10s. In the interim, by storing in the dark and cool dry place during non-usage period, the electrode can be used for at least 30 days without any momentous divergence of the potentiometric response. Eventually, to judge about its practical efficiency, the arranged sensor was utilized successfully as an indicator electrode for potentiometric titration of mercury(II) with standard solution of EDTA. As well, the quantitative analysis of mercury(II) ions in some aqueous samples with sensible accuracy and precision was satisfactorily performed. Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Use of the sulfide mineral pyrite as electrochemical sensor in non-aqueous solutions: potentiometric titration of weak acids in acetonitrile, propionitrile and benzonitrile.

    PubMed

    Mihajlović, Ljiljana; Nikolić-Mandić, Snezana; Vukanović, Branislav; Mihajlović, Randel

    2009-03-01

    Natural monocrystalline pyrite as a new indicator electrode for the potentiometric titration of weak acids in acetonitrile, propionitrile and benzonitrile was studied. The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 74 mV per decade. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be very suitable titrating agent for this titration. The response time was less than (11 s) and the lifetime of the electrode is long. The advantages of the electrode are log-term stability, fast response, and reproducibility, while the sensor is easy to prepare and of low cost.

  3. Characterization of a hybrid-smectite nanomaterial formed by immobilizing of N-pyridin-2-ylmethylsuccinamic acid onto (3-aminopropyl)triethoxysilane modified smectite and its potentiometric sensor application

    NASA Astrophysics Data System (ADS)

    Topcu, Cihan; Caglar, Sema; Caglar, Bulent; Coldur, Fatih; Cubuk, Osman; Sarp, Gokhan; Gedik, Kubra; Bozkurt Cirak, Burcu; Tabak, Ahmet

    2016-09-01

    A novel N-pyridin-2-ylmethylsuccinamic acid-functionalized smectite nanomaterial was synthesized by immobilizing of N-pyridin-2-ylmethylsuccinamic acid through chemical bonding onto (3-aminopropyl)triethoxysilane modified smectite. The structural, thermal, morphological and surface properties of raw, silane-grafted and the N-pyridin-2-ylmethylsuccinamic acid-functionalized smectites were investigated by various characterization techniques. The thermal analysis data showed the presence of peaks in the temperature range from 200 °C to 600 °C due to the presence of physically adsorbed silanes, intercalated silanes, surface grafted silanes and chemically grafted silane molecules between the smectite layers. The powder x-ray diffraction patterns clearly indicated that the aminopropyl molecules also intercalated into the smectite interlayers as bilayer arrangement whereas N-pyridin-2-ylmethylsuccinamic acid molecules were only attached to 3-aminopropyltriethoxysilane molecules on the external surface and edges of clay and they did not intercalate. Fourier transform infrared spectroscopy confirms N-pyridin-2-ylmethylsuccinamic acid molecules bonding through the amide bond between the amine group of aminopropyltriethoxysilane molecules and a carboxylic acid functional group of N-pyridin-2-ylmethylsuccinamic acid molecules. The guest molecules functionalized onto the smectite caused significant alterations in the textural and morphological parameters of the raw smectite. The anchoring of N-pyridin-2-ylmethylsuccinamic acid molecules led to positive electrophoretic mobility values when compared to starting materials. N-pyridin-2-ylmethylsuccinamic acid-functionalized smectite was employed as an electroactive ingredient in the structure of potentiometric PVC-membrane sensor. The sensor exhibited more selective potentiometric response towards chlorate ions compared to the other common anionic species.

  4. Galvanic Cell Type Sensor for Soil Moisture Analysis.

    PubMed

    Gaikwad, Pramod; Devendrachari, Mruthyunjayachari Chattanahalli; Thimmappa, Ravikumar; Paswan, Bhuneshwar; Raja Kottaichamy, Alagar; Makri Nimbegondi Kotresh, Harish; Thotiyl, Musthafa Ottakam

    2015-07-21

    Here we report the first potentiometric sensor for soil moisture analysis by bringing in the concept of Galvanic cells wherein the redox energies of Al and conducting polyaniline are exploited to design a battery type sensor. The sensor consists of only simple architectural components, and as such they are inexpensive and lightweight, making it suitable for on-site analysis. The sensing mechanism is proved to be identical to a battery type discharge reaction wherein polyaniline redox energy changes from the conducting to the nonconducting state with a resulting voltage shift in the presence of soil moisture. Unlike the state of the art soil moisture sensors, a signal derived from the proposed moisture sensor is probe size independent, as it is potentiometric in nature and, hence, can be fabricated in any shape or size and can provide a consistent output signal under the strong aberration conditions often encountered in soil moisture analysis. The sensor is regenerable by treating with 1 M HCl and can be used for multiple analysis with little read out hysteresis. Further, a portable sensor is fabricated which can provide warning signals to the end user when the moisture levels in the soil go below critically low levels, thereby functioning as a smart device. As the sensor is inexpensive, portable, and potentiometric, it opens up avenues for developing effective and energy efficient irrigation strategies, understanding the heat and water transfer at the atmosphere-land interface, understanding soil mechanics, forecasting the risk of natural calamities, and so on.

  5. Sulfadiazine-selective determination in aquaculture environment: selective potentiometric transduction by neutral or charged ionophores.

    PubMed

    Almeida, S A A; Heitor, A M; Montenegro, M C B S M; Sales, M G F

    2011-09-15

    Solid-contact sensors for the selective screening of sulfadiazine (SDZ) in aquaculture waters are reported. Sensor surfaces were made from PVC membranes doped with tetraphenylporphyrin-manganese(III) chloride, α-cyclodextrin, β-cyclodextrin, or γ-cyclodextrin ionophores that were dispersed in plasticizer. Some membranes also presented a positive or a negatively charged additive. Phorphyrin-based sensors relied on a charged carrier mechanism. They exhibited a near-Nernstian response with slopes of 52 mV decade(-1) and detection limits of 3.91×10(-5) mol L(-1). The addition of cationic lipophilic compounds to the membrane originated Nernstian behaviours, with slopes ranging 59.7-62.0 mV decade(-1) and wider linear ranges. Cyclodextrin-based sensors acted as neutral carriers. In general, sensors with positively charged additives showed an improved potentiometric performance when compared to those without additive. Some SDZ selective membranes displayed higher slopes and extended linear concentration ranges with an increasing amount of additive (always <100% ionophore). The sensors were independent from the pH of test solutions within 2-7. The sensors displayed fast response, always <15s. In general, a good discriminating ability was found in real sample environment. The sensors were successfully applied to the fast screening of SDZ in real waters samples from aquaculture fish farms. The method offered the advantages of simplicity, accuracy, and automation feasibility. The sensing membrane may contribute to the development of small devices allowing in locus measurements of sulfadiazine or parent-drugs. Copyright © 2011 Elsevier B.V. All rights reserved.

  6. Development of Hybrid pH sensor for long-term seawater pH monitoring.

    NASA Astrophysics Data System (ADS)

    Nakano, Y.; Egashira, T.; Miwa, T.; Kimoto, H.

    2016-02-01

    We have been developing the in situ pH sensor (Hybrid pH sensor: HpHS) for the long-term seawater pH monitoring. We are planning to provide the HpHS for researchers and environmental consultants for observation of the CCS (Carbon dioxide Capture and Storage) monitoring system, the coastal environment monitoring system (e.g. Blue Carbon) and ocean acidification. The HpHS has two types of pH sensors (i.e. potentiometric pH sensor and spectrophotometric pH sensor). The spectrophotometric pH sensor can measure pH correctly and stably, however it needs large power consumption and a lot of reagents in a long period of observation. The pH sensor used m-cresol purple (mCP) as an indicator of pH (Clayton and Byrne, 1993 and Liu et al., 2011). We can choose both coefficients before deployment. On the other hand, although the potentiometric pH sensor is low power consumption and high-speed response (within 10 seconds), drifts in the pH of the potentiometric measurements may possibly occur for a long-term observation. The HpHS can measure in situ pH correctly and stably combining advantage of both pH sensors. The HpHS consists of an aluminum pressure housing with optical cell (main unit) and an aluminum silicon-oil filled, pressure-compensated vessel containing pumps and valves (diaphragm pump and valve unit) and pressure-compensated reagents bags (pH indicator, pure water and Tris buffer or certified reference material: CRM) with an ability to resist water pressure to 3000m depth. The main unit holds system control boards, pump drivers, data storage (micro SD card), LED right source, photodiode, optical cell and pressure proof windows. The HpHS also has an aluminum pressure housing that holds a rechargeable lithium-ion battery or a lithium battery for the power supply (DC 24 V). The HpHS is correcting the value of the potentiometric pH sensor (measuring frequently) by the value of the spectrophotometric pH sensor (measuring less frequently). It is possible to calibrate in

  7. Design and construction of new potentiometric sensors for determination of Al3+ ion based on (Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine.

    PubMed

    Mizani, F; Salmanzadeh Ardabili, S; Ganjaliab, M R; Faridbod, F; Payehghadr, M; Azmoodeh, M

    2015-04-01

    (Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine (L) was used as an active component of PVC membrane electrode (PME), coated graphite electrode (CGE) and coated silver wire electrode (CWE) for sensing Al(3+) ion. The electrodes exhibited linear Nernstian responses to Al(3+) ion in the concentration range of 1.0×10(-6) to 1.0×10(-1)M (for PME, LOD=8.8×10(-7)M), 5.5×10(-7) to 2.0×10(-1)M (for CWE, LOD=3.3×10(-7)M) and 1.5×10(-7) to 1.0×10(-1)M (for CGE, LOD=9.2×10(-8)M). The best performances were observed with the membranes having the composition of L:PVC:NPOE:NaTPB in the ratio of 5:35:57:3 (w/w; mg). The electrodes have a response time of 6s and an applicable pH range of 3.5-9.1. The sensors have a lifetime of about 15weeks and exhibited excellent selectivity over a number of mono-, bi-, and tri-valent cations including alkali, alkaline earth metal, heavy and transition metal ions. Analytical utility of the proposed sensor has been further tested by using it as an indicator electrode in the potentiometric titration of Al(3+) with EDTA. The electrode was also successfully applied for the determination of Al(3+) ion in real and pharmaceutical samples. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Potentiometric surface in the Central Oklahoma (Garber-Wellington) aquifer, Oklahoma, 2009

    USGS Publications Warehouse

    Mashburn, Shana L.; Magers, Jessica

    2011-01-01

    A study of the hydrogeology of the Central Oklahoma aquifer was started in 2008 to provide the Oklahoma Water Resources Board (OWRB) hydrogeologic data and a groundwater flow model that can be used as a tool to help manage the aquifer. The 1973 Oklahoma water law requires the OWRB to do hydrologic investigations of Oklahoma's aquifers (termed 'groundwater basins') and to determine amounts of water that may be withdrawn by permitted water users. 'Maximum annual yield' is a term used by OWRB to describe the total amount of water that can be withdrawn from a specific aquifer in any year while allowing a minimum 20-year life of the basin (Oklahoma Water Resources Board, 2010). Currently (2010), the maximum annual yield has not been determined for the Central Oklahoma aquifer. Until the maximum annual yield determination is made, water users are issued a temporary permit by the OWRB for 2 acre-feet/acre per year. The objective of the study, in cooperation with the Oklahoma Water Resources Board, was to study the hydrogeology of the Central Oklahoma aquifer to provide information that will enable the OWRB to determine the maximum annual yield of the aquifer based on different proposed management plans. Groundwater flow models are typically used by the OWRB as a tool to help determine the maximum annual yield. This report presents the potentiometric surface of the Central Oklahoma aquifer based on water-level data collected in 2009 as part of the current (2010) hydrologic study. The U.S. Geological Survey (USGS) Hydrologic Investigations Atlas HA-724 by Christenson and others (1992) presents the 1986-87 potentiometric-surface map. This 1986-87 potentiometric-surface map was made as part of the USGS National Water-Quality Assessment pilot project for the Central Oklahoma aquifer that examined the geochemical and hydrogeological processes operating in the aquifer. An attempt was made to obtain water-level measurements for the 2009 potentiometric-surface map from the wells

  9. Integration of reconfigurable potentiometric electrochemical sensors into a digital microfluidic platform.

    PubMed

    Farzbod, Ali; Moon, Hyejin

    2018-05-30

    This paper presents the demonstration of on-chip fabrication of a potassium-selective sensor array enabled by electrowetting on dielectric digital microfluidics for the first time. This demonstration proves the concept that electrochemical sensors can be seamlessly integrated with sample preparation units in a digital microfluidic platform. More significantly, the successful on-chip fabrication of a sensor array indicates that sensors become reconfigurable and have longer lifetime in a digital microfluidic platform. The on-chip fabrication of ion-selective electrodes includes electroplating Ag followed by forming AgCl layer by chemical oxidation and depositing a thin layer of desired polymer-based ion selective membrane on one of the sensor electrodes. In this study, potassium ionophores work as potassium ion channels and make the membrane selective to potassium ions. This selectiveness results in the voltage difference across the membrane layer, which is correlated with potassium ion concentration. The calibration curve of the fabricated potassium-selective electrode demonstrates the slope of 58 mV/dec for potassium concentration in KCl sample solutions and shows good agreement with the ideal Nernstian response. The proposed sensor platform is an outstanding candidate for a portable home-use for continuous monitoring of ions thanks to its advantages such as easy automation of sample preparation and detection processes, elongated sensor lifetime, minimal membrane and sample consumption, and user-definable/reconfigurable sensor array. Copyright © 2018 Elsevier B.V. All rights reserved.

  10. Direct correlation between potentiometric and impedance biosensing of antibody-antigen interactions using an integrated system

    NASA Astrophysics Data System (ADS)

    Tsai, Meng-Yen; Creedon, Niamh; Brightbill, Eleanor; Pavlidis, Spyridon; Brown, Billyde; Gray, Darren W.; Shields, Niall; Sayers, Ríona; Mooney, Mark H.; O'Riordan, Alan; Vogel, Eric M.

    2017-08-01

    A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (ΔZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using electrochemical kinetics and the Butler-Volmer equation, we unveil that the surface potential and charge transfer resistance, measured by potentiometric and impedance biosensors, respectively, are, in fact, intrinsically linked. This observation suggests that there is no significant gain in using the FET/EIS integrated system and leads to the demonstration that low-cost EGFET biosensors are sufficient as a detection tool to resolve the charge information of biomolecules for practical sensing applications.

  11. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2005

    USGS Publications Warehouse

    Kinnaman, Sandra L.

    2006-01-01

    INTRODUCTION This map depicts the potentiometric surface of the upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2005. Potentiometric contours are based on water level measurements collected at 598 wens during the period May 5 - 31, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate upper Floridan aquifer responds mainly to rainfall, and more locally, to ground water withdrawals. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground water withdrawals locally have lowered the potentiometric surface. Ground water in the upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  12. Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, Florida, September, 2004

    USGS Publications Warehouse

    Kinnaman, Sandra L.

    2005-01-01

    Introduction: This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity in September 2004. Potentiometric contours are based on water-level measurements collected at 608 wells during the period September 14-October 1, near the end of the wet season. The shapes of some contours have been inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  13. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May, 2004

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Knowles, Leel

    2004-01-01

    INTRODUCTION This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity in May 2001. Potentiometric contours are based on water-level measurements collected at 684 wells during the period May 2 - 30, near the end of the dry season. The shapes of some contours have been inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  14. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2009

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Dixon, Joann F.

    2009-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2009. Potentiometric contours are based on water-level measurements collected at 625 wells during the period May 14 - May 29, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to groundwater withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Groundwater withdrawals locally have lowered the potentiometric surface. Groundwater in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  15. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2006

    USGS Publications Warehouse

    Kinnaman, Sandra L.

    2006-01-01

    Introduction: This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2006. Potentiometric contours are based on water-level measurements collected at 599 wells during the period May 14-31, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and springflow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  16. Potentiometric surface of the Upper Floridan aquifer in the St. Johns River water management district and vicinity, Florida, September 2005

    USGS Publications Warehouse

    Kinnaman, Sandra L.

    2006-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2005. Potentiometric contours are based on water-level measurements collected at 643 wells during the period September 12-28, near the end of the wet season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and springflow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  17. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2008

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Dixon, Joann F.

    2009-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2008. Potentiometric contours are based on water-level measurements collected at 589 wells during the period September 15-25, near the end of the wet season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  18. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2007

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Dixon, Joann F.

    2008-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2007. Potentiometric contours are based on water-level measurements collected at 554 wells during the period September 15-27, near the end of the wet season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  19. Potentiometric determination of ketotifen fumarate in pharmaceutical preparations and urine using carbon paste and PVC membrane selective electrodes.

    PubMed

    Frag, Eman Y Z; Mohamed, Gehad G; Khalil, Mohamed M; Hwehy, Mohammad M A

    2011-01-01

    This study compares between unmodified carbon paste (CPE; the paste has no ion pair) and polyvinyl chloride (PVC) membrane selective electrodes that were used in potentiometric determination of ketotifen fumarate (KTF), where sodium tetraphenylborate (NaTPB) was used as titrant. The performance characteristics of these sensors were evaluated according to IUPAC recommendations which reveal a fast, stable, and linear response for KTF over the concentration range of 10(-7) to 10(-2) mol L(-1). The electrodes show Nernstian slope value of 52.51 ± 0.20 and 51.51 ± 0.25 mV decade(-1) for CPE and PVC membrane electrodes at 30°C, respectively. The potential is nearly stable over the pH range 3.0-6.0 and 2.0-7.0 for CPE and PVC membrane electrodes, respectively. Selectivity coefficient values towards different inorganic cations, sugars, and amino acids reflect high selectivity of the prepared electrodes. The electrodes responses at different temperatures were also studied, and long operational lifetime of 12 and 5 weeks for CPE and PVC membrane electrodes, respectively, were found. These are used for determination of ketotifen fumarate using potentiometric titration, calibration, and standard addition methods in pure samples, its pharmaceutical preparations (Zaditen tablets), and biological fluid (urine). The direct potentiometric determination of KTF using the proposed sensors gave recoveries % of 98.97 ± 0.53 and 98.62 ± 0.74 with RSD 1.42 and 0.63% for CPE and PVC membrane selective electrodes, respectively. Validation of the method shows suitability of the proposed sensors for use in quality control assessment of KTF. The obtained results were in a good agreement with those obtained using the reported spectrophotometric method.

  20. Potentiometric Determination of Ketotifen Fumarate in Pharmaceutical Preparations and Urine Using Carbon Paste and PVC Membrane Selective Electrodes

    PubMed Central

    Frag, Eman Y. Z.; Mohamed, Gehad G.; Khalil, Mohamed M.; Hwehy, Mohammad M. A.

    2011-01-01

    This study compares between unmodified carbon paste (CPE; the paste has no ion pair) and polyvinyl chloride (PVC) membrane selective electrodes that were used in potentiometric determination of ketotifen fumarate (KTF), where sodium tetraphenylborate (NaTPB) was used as titrant. The performance characteristics of these sensors were evaluated according to IUPAC recommendations which reveal a fast, stable, and linear response for KTF over the concentration range of 10−7 to 10−2 mol L−1. The electrodes show Nernstian slope value of 52.51 ± 0.20 and 51.51 ± 0.25 mV decade−1 for CPE and PVC membrane electrodes at 30°C, respectively. The potential is nearly stable over the pH range 3.0–6.0 and 2.0–7.0 for CPE and PVC membrane electrodes, respectively. Selectivity coefficient values towards different inorganic cations, sugars, and amino acids reflect high selectivity of the prepared electrodes. The electrodes responses at different temperatures were also studied, and long operational lifetime of 12 and 5 weeks for CPE and PVC membrane electrodes, respectively, were found. These are used for determination of ketotifen fumarate using potentiometric titration, calibration, and standard addition methods in pure samples, its pharmaceutical preparations (Zaditen tablets), and biological fluid (urine). The direct potentiometric determination of KTF using the proposed sensors gave recoveries % of 98.97 ± 0.53 and 98.62 ± 0.74 with RSD 1.42 and 0.63% for CPE and PVC membrane selective electrodes, respectively. Validation of the method shows suitability of the proposed sensors for use in quality control assessment of KTF. The obtained results were in a good agreement with those obtained using the reported spectrophotometric method. PMID:22013443

  1. Reporter-free potentiometric sensing of boronic acids and their reactions by using quaternary ammonium salt-functionalized polymeric liquid membranes.

    PubMed

    Wang, Xuewei; Yue, Dengfeng; Lv, Enguang; Wu, Lei; Qin, Wei

    2014-02-18

    The tremendous applications of boronic acids (BAs) in chemical sensing, medical chemistry, molecular assembly, and organic synthesis lead to an urgent demand for developing effective sensing methods for BAs. This paper reports a facile and sensitive potentiometric sensor scheme for heterogeneous detection of BAs based on their unexpected potential responses on quaternary ammonium salt-doped polymeric liquid membranes. (11)B NMR data reveal that a quaternary ammonium chloride can trigger the hydrolysis of an electrically neutral BA in an aprotic solvent. Using the quaternary ammonium salt as the receptor, the BA molecules can be extracted from the sample solution into the polymeric membrane phase and undergo the concomitant hydrolysis. Such salt-triggered hydrolysis generates H(+) ions, which can be coejected into the aqueous phase with the counterions (e.g., Cl(-)) owing to their high hydrophilicities. The perturbation on the ionic partition at the sample-membrane interface changes the phase boundary potential and thus enables the potentiometric sensing of BAs. In contrast to other transduction methods for BAs, for which labeled or separate reporters are exclusively required, the present heterogeneous sensing scheme allows the direct detection of BAs without using any reporter molecules. This technique shows superior detection limits for BAs (e.g., 1.0 × 10(-6) M for phenylboronic acid) as compared to previously reported methods based on colorimetry, fluorimetry, and mass spectrometry. The proposed sensing strategy has also been successfully applied to potentiometric indication of the BA reactions with hydrogen peroxide and saccharides, which allows indirect and sensitive detection of these important species.

  2. Resistive Oxygen Gas Sensors for Harsh Environments

    PubMed Central

    Moos, Ralf; Izu, Noriya; Rettig, Frank; Reiß, Sebastian; Shin, Woosuck; Matsubara, Ichiro

    2011-01-01

    Resistive oxygen sensors are an inexpensive alternative to the classical potentiometric zirconia oxygen sensor, especially for use in harsh environments and at temperatures of several hundred °C or even higher. This device-oriented paper gives a historical overview on the development of these sensor materials. It focuses especially on approaches to obtain a temperature independent behavior. It is shown that although in the past 40 years there have always been several research groups working concurrently with resistive oxygen sensors, novel ideas continue to emerge today with respect to improvements of the sensor response time, the temperature dependence, the long-term stability or the manufacture of the devices themselves using novel techniques for the sensitive films. Materials that are the focus of this review are metal oxides; especially titania, titanates, and ceria-based formulations. PMID:22163805

  3. Septonex-tetraphenylborate screen-printed ion selective electrode for the potentiometric determination of Septonex in pharmaceutical preparations.

    PubMed

    Mohamed, Gehad G; El-Shahat, M F; Al-Sabagh, A M; Migahed, M A; Ali, Tamer Awad

    2011-04-07

    A screen-printed electrode (SPE) was fabricated for the determination of 1-(ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex) based on the use of Septonex-tetraphenylborate as the electroactive substance, and o-nitrophenyloctylether (o-NPOE) as the plasticizing agent. The electrode passes a near-Nernstian cationic slope of 59.33 ± 0.85 mV from activity between pH values of 2 to 9 with a lower detection limit of 9×10(-7) M and response time of about 5 s and exhibits an adequate shelf-life of 6 months. The method was applied for the determination of Septonex in pharmaceutical preparations. A percentage recovery of 99.88% was obtained with RSD=1.24%. The electrode was successfully applied in the determination of Septonex in laboratory-prepared samples by direct potentiometric, calibration curve and standard addition methods. Potentiometric titration of Septonex with sodium tetraphenylborate and phosphotungstic acid as a titrant was monitored with the modified screen-printed electrode as an end-point indicator electrode. Selectivity coefficients for Septonex relative to a number of potential interfering substances were determined. The sensor was highly selective for Septonex over a large number of compounds. Selectivity coefficient data for some common ions show negligible interference; however, cetyltrimethylammonium bromide and iodide ions interfere significantly. The analytical usefulness of the proposed electrode was evaluated by its application in the determination of Septonex in laboratory-prepared pharmaceutical samples with satisfactory results. The results obtained with the fabricated sensor are comparable with those obtained by the British Pharmacopeia method. © The Royal Society of Chemistry 2011

  4. Highly Stretchable Fully-Printed CNT-Based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-Induced Stretchability.

    PubMed

    Bandodkar, Amay J; Jeerapan, Itthipon; You, Jung-Min; Nuñez-Flores, Rogelio; Wang, Joseph

    2016-01-13

    We present the first example of an all-printed, inexpensive, highly stretchable CNT-based electrochemical sensor and biofuel cell array. The synergistic effect of utilizing specially tailored screen printable stretchable inks that combine the attractive electrical and mechanical properties of CNTs with the elastomeric properties of polyurethane as a binder along with a judiciously designed free-standing serpentine pattern enables the printed device to possess two degrees of stretchability. Owing to these synergistic design and nanomaterial-based ink effects, the device withstands extremely large levels of strains (up to 500% strain) with negligible effect on its structural integrity and performance. This represents the highest stretchability offered by a printed device reported to date. Extensive electrochemical characterization of the printed device reveal that repeated stretching, torsional twisting, and indenting stress has negligible impact on its electrochemical properties. The wide-range applicability of this platform to realize highly stretchable CNT-based electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium sensor, amperometric enzyme-based glucose sensor, enzymatic glucose biofuel cell, and self-powered biosensor. Highly stretchable printable multianalyte sensor, multifuel biofuel cell, or any combination thereof can thus be realized using the printed CNT array. Such combination of intrinsically stretchable printed nanomaterial-based electrodes and strain-enduring design patterns holds considerable promise for creating an attractive class of inexpensive multifunctional, highly stretchable printed devices that satisfy the requirements of diverse healthcare and energy fields wherein resilience toward extreme mechanical deformations is mandatory.

  5. Determination of Diffusion Parameters of CO2 Through Microporous PTFE Using a Potentiometric Method

    NASA Astrophysics Data System (ADS)

    Tarsiche, I.; Ciurchea, D.

    Dk values at the diffusion of CO2 through microporous PTFE of 1 to 7 × 10- 7 cm2 s- 1 in the concentration range from 4 × 10- 4 to 0.22 g/l CO2 are determined using a simple, fast and reliable potentiometric method. The method is based on the least-squares fitting of the potential versus time response of a self made CO2 sensitive Severinghaus type sensor with PTFE as a gas-permeable membrane. The obtained results are in good agreement with other reported literature data, both experimental or calculated ones using molecular dynamics simulations. The proposed technique is very sensitive especially at low concentrations of gas and may be used for the study of other polymeric membranes too.

  6. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2006

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Dixon, Joann F.

    2007-01-01

    Introduction This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2006. Potentiometric contours are based on water-level measurements collected at 571 wells during the period September 11-29, near the end of the wet season. Some contours are inferred from previouspotentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  7. A Portable Low-Power Acquisition System with a Urease Bioelectrochemical Sensor for Potentiometric Detection of Urea Concentrations.

    PubMed

    Ma, Wei-Jhe; Luo, Ching-Hsing; Lin, Jiun-Ling; Chou, Sin-Houng; Chen, Ping-Hung; Syu, Mei-Jywan; Kuo, Shin-Hung; Lai, Shin-Chi

    2016-04-02

    This paper presents a portable low-power battery-driven bioelectrochemical signal acquisition system for urea detection. The proposed design has several advantages, including high performance, low cost, low-power consumption, and high portability. A LT1789-1 low-supply-voltage instrumentation amplifier (IA) was used to measure and amplify the open-circuit potential (OCP) between the working and reference electrodes. An MSP430 micro-controller was programmed to process and transduce the signals to the custom-developed software by ZigBee RF module in wireless mode and UART in able mode. The immobilized urease sensor was prepared by embedding urease into the polymer (aniline-co-o-phenylenediamine) polymeric matrix and then coating/depositing it onto a MEMS-fabricated Au working electrode. The linear correlation established between the urea concentration and the potentiometric change is in the urea concentrations range of 3.16 × 10(-4) to 3.16 × 10(-2) M with a sensitivity of 31.12 mV/log [M] and a precision of 0.995 (R² = 0.995). This portable device not only detects urea concentrations, but can also operate continuously with a 3.7 V rechargeab-le lithium-ion battery (500 mA·h) for at least four days. Accordingly, its use is feasible and even promising for home-care applications.

  8. A novel inhibition based biosensor using urease nanoconjugate entrapped biocomposite membrane for potentiometric glyphosate detection.

    PubMed

    Vaghela, Chetana; Kulkarni, Mohan; Haram, Santosh; Aiyer, Rohini; Karve, Meena

    2018-03-01

    A potentiometric biosensor based on agarose-guar gum (A-G) entrapped bio-nanoconjugate of urease with gold nanoparticles (AUNps), has been reported for the first time for glyphosate detection. The biosensor is based on inhibition of urease activity by glyphosate, which was measured by direct potentiometry using ammonium ion selective electrode covered with A-G-urease nanoconjugate membrane. TEM and FTIR analysis revealed nanoconjugate formation and its immobilization in A-G matrix respectively. The composite biopolymer employed for immobilization yields thin, transparent, flexible membrane having superior mechanical strength and stability. It retains the maximum activity (92%) of urease with negligible leaching. The conjugation of urease with AUNps allows improvement in response characteristics for potentiometric measurement. The biosensor shows a linear response in the glyphosate concentration range from 0.5ppm-50ppm, with limit of detection at 0.5ppm, which covers maximum residual limit set by WHO for drinking water. The inhibition of catalytic activity of urease nanoconjugate by gyphosate was confirmed by FTIR analysis. The response of fabricated biosensor is selective towards glyphosate as against various other pesticides. The biosensor exhibits good performance in terms of reproducibility and prolonged storage stability of 180days. Thus, the present biosensor provides an alternative method for simple, selective and cost effective detection of glyphosate based on urease inhibition. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Determination of urine ionic composition with potentiometric multisensor system.

    PubMed

    Yaroshenko, Irina; Kirsanov, Dmitry; Kartsova, Lyudmila; Sidorova, Alla; Borisova, Irina; Legin, Andrey

    2015-01-01

    The ionic composition of urine is a good indicator of patient's general condition and allows for diagnostics of certain medical problems such as e.g., urolithiasis. Due to environmental factors and malnutrition the number of registered urinary tract cases continuously increases. Most of the methods currently used for urine analysis are expensive, quite laborious and require skilled personnel. The present work deals with feasibility study of potentiometric multisensor system of 18 ion-selective and cross-sensitive sensors as an analytical tool for determination of urine ionic composition. In total 136 samples from patients of Urolithiasis Laboratory and healthy people were analyzed by the multisensor system as well as by capillary electrophoresis as a reference method. Various chemometric approaches were implemented to relate the data from electrochemical measurements with the reference data. Logistic regression (LR) was applied for classification of samples into healthy and unhealthy producing reasonable misclassification rates. Projection on Latent Structures (PLS) regression was applied for quantitative analysis of ionic composition from potentiometric data. Mean relative errors of simultaneous prediction of sodium, potassium, ammonium, calcium, magnesium, chloride, sulfate, phosphate, urate and creatinine from multisensor system response were in the range 3-13% for independent test sets. This shows a good promise for development of a fast and inexpensive alternative method for urine analysis. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Potentiometric Surface of the Magothy Aquifer in Southern Maryland, September 2001

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2002-01-01

    This report presents a map showing the change in the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland for September 1982 and September 2001. The map, based on water level measurements in 58 wells, shows that the potentiometric surface during the 19-year period declined from zero in the northernmost part of the study area, which is the outcrop of the aquifer, to 120 feet at Lexington Park. Lexington Park is near the southeasternmost part of the study area and approaches the downdip boundary of the aquifer.

  11. Potentiometric surface of the Magothy aquifer in southern Maryland, September 1999

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2001-01-01

    This report presents a map showing the change in the potentiometric surface of the Lower Patapsco aquifer in the Lower Patapsco Formation of Cretaceous age in Southern Maryland for September 1990 and September 1999. The map, based on water?level measurements in 52 wells, shows that the change of the potentiometric surface during the 9- year period ranged from a rise of 13 feet at Indian Head and 6 feet near the outcrop area in Glen Burnie, to declines of 34 feet at Arnold, 30 feet at Waldorf, and 24 feet at Morgantown.

  12. Potentiometric titration and equivalent weight of humic acid

    USGS Publications Warehouse

    Pommer, A.M.; Breger, I.A.

    1960-01-01

    The "acid nature" of humic acid has been controversial for many years. Some investigators claim that humic acid is a true weak acid, while others feel that its behaviour during potentiometric titration can be accounted for by colloidal adsorption of hydrogen ions. The acid character of humic acid has been reinvestigated using newly-derived relationships for the titration of weak acids with strong base. Re-interpreting the potentiometric titration data published by Thiele and Kettner in 1953, it was found that Merck humic acid behaves as a weak polyelectrolytic acid having an equivalent weight of 150, a pKa of 6.8 to 7.0, and a titration exponent of about 4.8. Interdretation of similar data pertaining to the titration of phenol-formaldehyde and pyrogallol-formaldehyde resins, considered to be analogs for humic acid by Thiele and Kettner, leads to the conclusion that it is not possible to differentiate between adsorption and acid-base reaction for these substances. ?? 1960.

  13. The Potentiometric Titration of Filtrates from the Bachmann Process

    DTIC Science & Technology

    1942-06-23

    SCIENTIFIC RESEARCH AND DEVELOP11ENT The Potentiometric Titration of Filtrates from the Bachmann Process (OD-12) by F. C. Whitmore OSRD No. 654... Potentiometric Titration of Synthetic Mixtures. A? Nitric Acid-Acetic Acid. A sample of 60 ml. glacial acetic acid war diluted to 200 ml. with distilled...i4flinflr?fj3 TADLE 1 CO) |S?lDBnTl» POTENTIOMETRIC TITRATION OF SYNTHETIC t’.IXTURES WITH CONCENTRATED AJKDNIUM HYDROXIDE A; unonium HNO-j- AcOfi Ky

  14. Diurnal and seasonal variations of pH for a year in the western subarctic North Pacific observed by using a hybrid pH sensor

    NASA Astrophysics Data System (ADS)

    Nakano, Yoshiyuki; Fujiki, Tetsuichi; Kimoto, Katsunori; Miwa, Tetsuya

    2017-04-01

    Ocean acidification has many far reaching impacts on plankton community in the ocean. There is great need of quality instrumentation to assess and monitor the changing seawater pH. To meet the need, we have developed the in situ high accurate pH sensor (Hybrid pH sensor: HpHS) for the long-term seawater pH monitoring to participate the Wendy Schmidt Ocean health XPRIZE. The HpHS has two types of pH sensors (i.e. potentiometric pH sensor and spectrophotometric pH sensor). The spectrophotometric pH sensor can measure pH correctly and stably, however it needs large power consumption and a lot of reagents in a long period of observation. The pH sensor used m-cresol purple (mCP) as an indicator of pH. On the other hand, although the potentiometric pH sensor is low power consumption and high-speed response (within 10 seconds), drifts in the pH of the potentiometric measurements may possibly occur for a long-term observation. The HpHS can measure in situ pH correctly and stably combining advantage of both pH sensors. The HpHS is correcting the value of the potentiometric pH (measuring frequently) by the value of the spectrophotometric pH (measuring less frequently). It is possible to calibrate in situ with Tris buffer or CRM on the spectrophotometric pH sensor. Therefore, the drifts in the value of potentiometric pH measurements can be compensated using the pH value obtained from the spectrophotometric pH measurements. Thereby, the HpHS can measure accurately the value of pH over a long period of time with low power consumption. In order to understand the seasonal and inter-annual variabilities of biogeochemical cycles and ecosystems, ship-based studies have been carried out since 1997 at time-series station K2 (47oN, 160oE) in the subarctic western North Pacific, which is a region with progression of ocean acidification. However, the ship-based studies of the open ocean have been limited in their ability to conduct high-frequency observations for understanding the

  15. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, May 2007

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Dixon, Joann F.

    2007-01-01

    Introduction This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2007. Potentiometric contours are based on water-level measurements collected at 566 wells during the period May 4-June 11 near the end of the dry season, however most of the water level data for this map were collected by the U.S. Geological Survey during the period May 21-25, 2007. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

  16. Potentiometric Titrations for Measuring the Capacitance of Colloidal Photodoped ZnO Nanocrystals.

    PubMed

    Brozek, Carl K; Hartstein, Kimberly H; Gamelin, Daniel R

    2016-08-24

    Colloidal semiconductor nanocrystals offer a unique opportunity to bridge molecular and bulk semiconductor redox phenomena. Here, potentiometric titration is demonstrated as a method for quantifying the Fermi levels and charging potentials of free-standing colloidal n-type ZnO nanocrystals possessing between 0 and 20 conduction-band electrons per nanocrystal, corresponding to carrier densities between 0 and 1.2 × 10(20) cm(-3). Potentiometric titration of colloidal semiconductor nanocrystals has not been described previously, and little precedent exists for analogous potentiometric titration of any soluble reductants involving so many electrons. Linear changes in Fermi level vs charge-carrier density are observed for each ensemble of nanocrystals, with slopes that depend on the nanocrystal size. Analysis indicates that the ensemble nanocrystal capacitance is governed by classical surface electrical double layers, showing no evidence of quantum contributions. Systematic shifts in the Fermi level are also observed with specific changes in the identity of the charge-compensating countercation. As a simple and contactless alternative to more common thin-film-based voltammetric techniques, potentiometric titration offers a powerful new approach for quantifying the redox properties of colloidal semiconductor nanocrystals.

  17. Solid state oxygen sensor

    DOEpatents

    Garzon, Fernando H.; Brosha, Eric L.

    1997-01-01

    A potentiometric oxygen sensor is formed having a logarithmic response to a differential oxygen concentration while operating as a Nernstian-type sensor. Very thin films of mixed conducting oxide materials form electrode services while permitting diffusional oxygen access to the interface between the zirconia electrolyte and the electrode. Diffusion of oxygen through the mixed oxide is not rate-limiting. Metal electrodes are not used so that morphological changes in the electrode structure do not occur during extended operation at elevated temperatures.

  18. Solid state oxygen sensor

    DOEpatents

    Garzon, F.H.; Brosha, E.L.

    1997-12-09

    A potentiometric oxygen sensor is formed having a logarithmic response to a differential oxygen concentration while operating as a Nernstian-type sensor. Very thin films of mixed conducting oxide materials form electrode services while permitting diffusional oxygen access to the interface between the zirconia electrolyte and the electrode. Diffusion of oxygen through the mixed oxide is not rate-limiting. Metal electrodes are not used so that morphological changes in the electrode structure do not occur during extended operation at elevated temperatures. 6 figs.

  19. Determining a Solubility Product Constant by Potentiometric Titration to Increase Students' Conceptual Understanding of Potentiometry and Titrations

    ERIC Educational Resources Information Center

    Grabowski, Lauren E.; Goode, Scott R.

    2017-01-01

    Potentiometric titrations are widely taught in first-year undergraduate courses to connect electrochemistry, stoichiometry, and equilibria and to reinforce acid-base titrations. Students perform a potentiometric titration that is then analyzed to determine analyte concentrations and the solubility product constant of the solid species.

  20. Calixarene-based potentiometric ion-selective electrodes for silver.

    PubMed

    O'Connor, K M; Svehla, G; Harris, S J; McKervey, M A

    1992-11-01

    Four lipophilic sulphur and/or nitrogen containing calixarene derivatives have been tested as ionophores in Ag(I)-selective poly (vinyl chloride) membrane electrodes. All gave acceptable linear responses with one giving a response of 50 mV/dec in the Ag(I) ion activity range 10(-4)-10(-1)M and high selectivity towards other transition metals and sodium and potassium ions. This ionophore was also tested as a membrane coated glassy-carbon electrode where the sensitivity and selectivity of the conventional membrane electrode was found to be repeated. The latter electrode was then used in potentiometric titrations of halide ions with silver nitrate.

  1. Monitoring of beer fermentation based on hybrid electronic tongue.

    PubMed

    Kutyła-Olesiuk, Anna; Zaborowski, Michał; Prokaryn, Piotr; Ciosek, Patrycja

    2012-10-01

    Monitoring of biotechnological processes, including fermentation is extremely important because of the rapidly occurring changes in the composition of the samples during the production. In the case of beer, the analysis of physicochemical parameters allows for the determination of the stage of fermentation process and the control of its possible perturbations. As a tool to control the beer production process a sensor array can be used, composed of potentiometric and voltammetric sensors (so-called hybrid Electronic Tongue, h-ET). The aim of this study is to apply electronic tongue system to distinguish samples obtained during alcoholic fermentation. The samples originate from batch of homemade beer fermentation and from two stages of the process: fermentation reaction and maturation of beer. The applied sensor array consists of 10 miniaturized ion-selective electrodes (potentiometric ET) and silicon based 3-electrode voltammetric transducers (voltammetric ET). The obtained results were processed using Partial Least Squares (PLS) and Partial Least Squares-Discriminant Analysis (PLS-DA). For potentiometric data, voltammetric data, and combined potentiometric and voltammetric data, comparison of the classification ability was conducted based on Root Mean Squared Error (RMSE), sensitivity, specificity, and coefficient F calculation. It is shown, that in the contrast to the separately used techniques, the developed hybrid system allowed for a better characterization of the beer samples. Data fusion in hybrid ET enables to obtain better results both in qualitative analysis (RMSE, specificity, sensitivity) and in quantitative analysis (RMSE, R(2), a, b). Copyright © 2012 Elsevier B.V. All rights reserved.

  2. Highly selective potentiometric and colorimetric determinations of cobalt (II) ion using thiazole based ligands.

    PubMed

    Singhal, Divya; Singh, Ashok Kumar; Upadhyay, Anjali

    2014-12-01

    New PVC-membrane electrodes were prepared by using 2-((thiazol-2-ylimino)methyl)phenol (L1) and 2-((thiazol-2-ylamino)methyl)phenol (L2) and explored as Co(II) selective electrodes. The effect of various plasticizers and anion excluder was studied in detail and improved performance was observed. It was found that the electrode based on L1 shows better response characteristics in comparison to L2. Optimum performance was observed for the membrane electrode having a composition of L1:NaTPB:DBP:PVC≡2:8:78:62 (w/w, mg). The performance of PME based on L1 was compared with that of CGE. The electrodes exhibit Nernstian slope for Co(II) ions with a limit of detection of 6.91×10(-7) mol L(-1) for PME and 7.94×10(-8) mol L(-1) for CGE. The response time for PME and CGE was found to be 15s and 12 s respectively. The potentiometric responses are independent in the pH range 3.0-9.0 for CGE. The CGE could be used for a period of 90 days. The CGE was used as an indicator electrode in potentiometric titration of EDTA with Co(2+) ion. Further the selectivity of the L1 and L2 was also confirmed by the UV-vis and colorimetric studies and found that L1 is more selective for Co(II) ion. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Potentiometric Aptasensing of Vibrio alginolyticus Based on DNA Nanostructure-Modified Magnetic Beads.

    PubMed

    Zhao, Guangtao; Ding, Jiawang; Yu, Han; Yin, Tanji; Qin, Wei

    2016-12-02

    A potentiometric aptasensing assay that couples the DNA nanostructure-modified magnetic beads with a solid-contact polycation-sensitive membrane electrode for the detection of Vibrio alginolyticus is herein described. The DNA nanostructure-modified magnetic beads are used for amplification of the potential response and elimination of the interfering effect from a complex sample matrix. The solid-contact polycation-sensitive membrane electrode using protamine as an indicator is employed to chronopotentiometrically detect the change in the charge or DNA concentration on the magnetic beads, which is induced by the interaction between Vibrio alginolyticus and the aptamer on the DNA nanostructures. The present potentiometric aptasensing method shows a linear range of 10-100 CFU mL -1 with a detection limit of 10 CFU mL -1 , and a good specificity for the detection of Vibrio alginolyticus . This proposed strategy can be used for the detection of other microorganisms by changing the aptamers in the DNA nanostructures.

  4. Potentiometric Aptasensing of Vibrio alginolyticus Based on DNA Nanostructure-Modified Magnetic Beads

    PubMed Central

    Zhao, Guangtao; Ding, Jiawang; Yu, Han; Yin, Tanji; Qin, Wei

    2016-01-01

    A potentiometric aptasensing assay that couples the DNA nanostructure-modified magnetic beads with a solid-contact polycation-sensitive membrane electrode for the detection of Vibrio alginolyticus is herein described. The DNA nanostructure-modified magnetic beads are used for amplification of the potential response and elimination of the interfering effect from a complex sample matrix. The solid-contact polycation-sensitive membrane electrode using protamine as an indicator is employed to chronopotentiometrically detect the change in the charge or DNA concentration on the magnetic beads, which is induced by the interaction between Vibrio alginolyticus and the aptamer on the DNA nanostructures. The present potentiometric aptasensing method shows a linear range of 10–100 CFU mL−1 with a detection limit of 10 CFU mL−1, and a good specificity for the detection of Vibrio alginolyticus. This proposed strategy can be used for the detection of other microorganisms by changing the aptamers in the DNA nanostructures. PMID:27918423

  5. Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique.

    PubMed

    Khan, Md Rajibur Rahaman; Kang, Shin-Won

    2016-11-09

    In this study, we propose a highly sensitive multichannel pH sensor that is based on an optical-fiber pulse width modulation (PWM) technique. According to the optical-fiber PWM method, the received sensing signal's pulse width changes when the optical-fiber pH sensing-element of the array comes into contact with pH buffer solutions. The proposed optical-fiber PWM pH-sensing system offers a linear sensing response over a wide range of pH values from 2 to 12, with a high pH-sensing ability. The sensitivity of the proposed pH sensor is 0.46 µs/pH, and the correlation coefficient R² is approximately 0.997. Additional advantages of the proposed optical-fiber PWM pH sensor include a short/fast response-time of about 8 s, good reproducibility properties with a relative standard deviation (RSD) of about 0.019, easy fabrication, low cost, small size, reusability of the optical-fiber sensing-element, and the capability of remote sensing. Finally, the performance of the proposed PWM pH sensor was compared with that of potentiometric, optical-fiber modal interferometer, and optical-fiber Fabry-Perot interferometer pH sensors with respect to dynamic range width, linearity as well as response and recovery times. We observed that the proposed sensing systems have better sensing abilities than the above-mentioned pH sensors.

  6. Highly Sensitive and Wide-Dynamic-Range Multichannel Optical-Fiber pH Sensor Based on PWM Technique

    PubMed Central

    Khan, Md. Rajibur Rahaman; Kang, Shin-Won

    2016-01-01

    In this study, we propose a highly sensitive multichannel pH sensor that is based on an optical-fiber pulse width modulation (PWM) technique. According to the optical-fiber PWM method, the received sensing signal’s pulse width changes when the optical-fiber pH sensing-element of the array comes into contact with pH buffer solutions. The proposed optical-fiber PWM pH-sensing system offers a linear sensing response over a wide range of pH values from 2 to 12, with a high pH-sensing ability. The sensitivity of the proposed pH sensor is 0.46 µs/pH, and the correlation coefficient R2 is approximately 0.997. Additional advantages of the proposed optical-fiber PWM pH sensor include a short/fast response-time of about 8 s, good reproducibility properties with a relative standard deviation (RSD) of about 0.019, easy fabrication, low cost, small size, reusability of the optical-fiber sensing-element, and the capability of remote sensing. Finally, the performance of the proposed PWM pH sensor was compared with that of potentiometric, optical-fiber modal interferometer, and optical-fiber Fabry–Perot interferometer pH sensors with respect to dynamic range width, linearity as well as response and recovery times. We observed that the proposed sensing systems have better sensing abilities than the above-mentioned pH sensors. PMID:27834865

  7. A Portable Low-Power Acquisition System with a Urease Bioelectrochemical Sensor for Potentiometric Detection of Urea Concentrations

    PubMed Central

    Ma, Wei-Jhe; Luo, Ching-Hsing; Lin, Jiun-Ling; Chou, Sin-Houng; Chen, Ping-Hung; Syu, Mei-Jywan; Kuo, Shin-Hung; Lai, Shin-Chi

    2016-01-01

    This paper presents a portable low-power battery-driven bioelectrochemical signal acquisition system for urea detection. The proposed design has several advantages, including high performance, low cost, low-power consumption, and high portability. A LT1789-1 low-supply-voltage instrumentation amplifier (IA) was used to measure and amplify the open-circuit potential (OCP) between the working and reference electrodes. An MSP430 micro-controller was programmed to process and transduce the signals to the custom-developed software by ZigBee RF module in wireless mode and UART in able mode. The immobilized urease sensor was prepared by embedding urease into the polymer (aniline-co-o-phenylenediamine) polymeric matrix and then coating/depositing it onto a MEMS-fabricated Au working electrode. The linear correlation established between the urea concentration and the potentiometric change is in the urea concentrations range of 3.16 × 10−4 to 3.16 × 10−2 M with a sensitivity of 31.12 mV/log [M] and a precision of 0.995 (R2 = 0.995). This portable device not only detects urea concentrations, but can also operate continuously with a 3.7 V rechargeab-le lithium-ion battery (500 mA·h) for at least four days. Accordingly, its use is feasible and even promising for home-care applications. PMID:27049390

  8. Fabrication and Performance of All-Solid-State Chloride Sensors in Synthetic Concrete Pore Solutions

    PubMed Central

    Gao, Xiaojian; Zhang, Jian; Yang, Yingzi; Deng, Hongwei

    2010-01-01

    One type of all-solid-state chloride sensor was fabricated using a MnO2 electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show a good linear relationship between the potential reading of the sensor and the logarithm of chloride activity (concentration ranges from 0.05 to 5.0 M), and the potential value remains stable with increasing immersion time. The existence of K+, Ca2+, Na+ and SO42− ions have little influence on the potentiometric response of the sensor to chloride, but the pH has a significant influence on the potential value of the sensor at low chloride concentration. The potential reading of the sensor increases linearly with the solution temperature over the range from 5 to 45 °C. Meanwhile, an excellent polarization behavior is proven by galvanostatic and potentiodynamic tests. All of the results reveal that the developed sensor has a great potential for monitoring chloride ions in concrete environments. PMID:22163467

  9. Fabrication and performance of all-solid-state chloride sensors in synthetic concrete pore solutions.

    PubMed

    Gao, Xiaojian; Zhang, Jian; Yang, Yingzi; Deng, Hongwei

    2010-01-01

    One type of all-solid-state chloride sensor was fabricated using a MnO(2) electrode and a Ag/AgCl electrode. The potentiometric response of the sensor to chloride in synthetic concrete pore solutions was systematically studied, and the polarization performance was also evaluated. The results show a good linear relationship between the potential reading of the sensor and the logarithm of chloride activity (concentration ranges from 0.05 to 5.0 M), and the potential value remains stable with increasing immersion time. The existence of K(+), Ca(2+), Na(+) and SO(4) (2-) ions have little influence on the potentiometric response of the sensor to chloride, but the pH has a significant influence on the potential value of the sensor at low chloride concentration. The potential reading of the sensor increases linearly with the solution temperature over the range from 5 to 45 °C. Meanwhile, an excellent polarization behavior is proven by galvanostatic and potentiodynamic tests. All of the results reveal that the developed sensor has a great potential for monitoring chloride ions in concrete environments.

  10. Real-time potentiometric sensor; an innovative tool for monitoring hydrolysis of chemo/bio-degradable drugs in pharmaceutical sciences.

    PubMed

    Ma'mun, Ahmed; Abd El-Rahman, Mohamed K; Abd El-Kawy, Mohamed

    2018-05-30

    In recent years, the whole field of ion-selective electrodes(ISEs) in pharmaceutical sciences has expanded far beyond its original roots. The diverse range of opportunities offered by ISEs was broadly used in a number of pharmaceutical applications, with topics presented ranging from bioanalysis of drugs and metabolites, to protein binding studies, green analytical chemistry, impurity profiling, and drug dissolution in biorelevant media. Inspired from these advances and with the aim of extending the functional capabilities of ISEs, the primary focus of the present paper is the utilization of ISE as a tool in personalized medicine. Given the opportunity to explore biological events in real-time (such as drug metabolism) could be central to personalized medicine. (ATR) is a chemo-degradable and bio-degradable pharmaceutically active drug. Laudanosine (LDS) is the major degradation product and metabolite of ATR and is potentially toxic and reported to possess epileptogenic activity which increases the risk of convulsive effects. In this work, ATR have been subjected to both chemical and biological hydrolysis, and the course of the reactions is monitored by means of a ISE. In this study, we have designed an efficient real-time tracking strategy which substantially resolve the challenges of the ATR chemical and biological degradation kinetics. By utilizing a potentiometric sensor, tracking of ATR chemical and biological degradation kinetics can be performed in a very short time with excellent accuracy. The LOD was calculated to be 0.23 μmol L -1 , the potential drift was investigated over a period of 60 min and the value was 0.25 mV h -1 . Real serum samples for measurement the rate of in vitro metabolism of ATR was performed. Furthermore, a full description of the fabricated screen-printed sensor was presented. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Map showing the potentiometric surface of the Magothy Aquifer in southern Maryland, September 1982

    USGS Publications Warehouse

    Mack, Frederick K.; Wheeler, Judith C.; Curtin, Stephen E.

    1982-01-01

    A map was prepared that shows the potentiometric surface of the Magothy aquifer in southern Maryland in September 1982. The map is based on measurements from a network of 83 observation wells. The highest levels of the potentiometric surface, 57 and 58 feet above sea level, were measured near the outcrop-subcrop of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties. The potentiometric surface slopes to the southeast to about sea level along much of the western shore of the Chesapeake Bay. Three distinct and extensive cones of depression have developed in the potentiometric surface around the well fields of the Annapolis area, Waldorf area, and Chalk Point. Several square miles of each cone are below sea level, and in some areas at Chalk Point and Waldorf, the cone is more than 50 feet below sea level. The network of wells was developed as part of the cooperative program between the U.S. Geological Survey, the Maryland Geological Survey, and the Maryland Energy Administration. (USGS)

  12. Single-cultivar extra virgin olive oil classification using a potentiometric electronic tongue.

    PubMed

    Dias, Luís G; Fernandes, Andreia; Veloso, Ana C A; Machado, Adélio A S C; Pereira, José A; Peres, António M

    2014-10-01

    Label authentication of monovarietal extra virgin olive oils is of great importance. A novel approach based on a potentiometric electronic tongue is proposed to classify oils obtained from single olive cultivars (Portuguese cvs. Cobrançosa, Madural, Verdeal Transmontana; Spanish cvs. Arbequina, Hojiblanca, Picual). A meta-heuristic simulated annealing algorithm was applied to select the most informative sets of sensors to establish predictive linear discriminant models. Olive oils were correctly classified according to olive cultivar (sensitivities greater than 97%) and each Spanish olive oil was satisfactorily discriminated from the Portuguese ones with the exception of cv. Arbequina (sensitivities from 61% to 98%). Also, the discriminant ability was related to the polar compounds contents of olive oils and so, indirectly, with organoleptic properties like bitterness, astringency or pungency. Therefore the proposed E-tongue can be foreseen as a useful auxiliary tool for trained sensory panels for the classification of monovarietal extra virgin olive oils. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Potentiometric surface of the Ozark aquifer in northern Arkansas, 2004

    USGS Publications Warehouse

    Schrader, T.P.

    2005-01-01

    The Ozark aquifer in northern Arkansas comprises dolomites, limestones, sandstones, and shales of Late Cambrian to Middle Devonian age, and ranges in thickness from approximately 1,100 feet to more than 4,000 feet. Hydrologically, the aquifer is complex, characterized by discrete and discontinuous flow components with large variations in permeability. The potentiometric-surface map, based on 59 well and 5 spring water-level measurements collected in 2004 in Arkansas and Missouri, indicates maximum water-level altitudes of about 1,188 feet in Benton County and minimum water-level altitudes of about 116 feet in Randolph County. Regionally, the flow within the aquifer is to the south and southeast in the eastern and central part of the study area and to the northwest and north in the western part of the study area. Comparing the 2004 potentiometric- surface map with a predevelopment potentiometricsurface map indicates general agreement between the two surfaces. Potentiometric-surface differences could be attributed to differences in pumping related to changing population from 1990 to 2000, change in source for public supplies, processes or water use outside the study area, or differences in data-collection or map-construction methods.

  14. Indirect potentiometric titration of ascorbic acid in pharmaceutical preparations using copper based mercury film electrode.

    PubMed

    Abdul Kamal Nazer, Meeran Mohideen; Hameed, Abdul Rahman Shahul; Riyazuddin, Patel

    2004-01-01

    A simple and rapid potentiometric method for the estimation of ascorbic acid in pharmaceutical dosage forms has been developed. The method is based on treating ascorbic acid with iodine and titration of the iodide produced equivalent to ascorbic acid with silver nitrate using Copper Based Mercury Film Electrode (CBMFE) as an indicator electrode. Interference study was carried to check possible interference of usual excipients and other vitamins. The precision and accuracy of the method was assessed by the application of lack-of-fit test and other statistical methods. The results of the proposed method and British Pharmacopoeia method were compared using F and t-statistical tests of significance.

  15. Natural monocrystalline pyrite as a sensor in non-aqueous solution Part I: Potentiometric titration of weak acids in, N,N-dimethylformamide, methylpyrrolidone and pyridine.

    PubMed

    Mihajlović, Lj V; Mihajlović, R P; Antonijević, M M; Vukanović, B V

    2004-11-15

    The possibility of applying natural monocrystaline pyrite as a sensor for the potentiometric titration of weak acids in N,N-dimethylformamide, methylpyrrolidone and pyridine was investigated. The potential of this electrode in N,N-dimethylformamide, methylpyrrolidone and pyridine exhibits a sub-Nernst dependence. In N,N-dimethylformamide the slope (mV/pH) is 39.0 and in methylpyrrolidone it is 45.0. The potential jumps at the titration end-point obtained in the titration of weak acids are higher than those obtained by the application of a glass electrode as the indicator electrode The potential in the course of the titration and at the titration end-point (TEP) are rapidly established. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be very suitable titrating agents for these titrations. The results obtained in the determination of the investigated weak acids deviate by 0.1-0.35% with respect to those obtained by using a glass electrode as the indicator electrode.

  16. Dynamic potential and surface morphology study of sertraline membrane sensors

    PubMed Central

    Khater, M.M.; Issa, Y.M.; Hassib, H.B.; Mohammed, S.H.

    2014-01-01

    New rapid, sensitive and simple electrometric method was developed to determine sertraline hydrochloride (Ser-Cl) in its pure raw material and pharmaceutical formulations. Membrane sensors based on heteropolyacids as ion associating material were prepared. Silicomolybdic acid (SMA), silicotungstic acid (STA) and phosphomolybdic acid (PMA) were used. The slope and limit of detection are 50.00, 60.00 and 53.24 mV/decade and 2.51, 5.62 and 4.85 μmol L−1 for Ser-ST, Ser-PM and Ser-SM membrane sensors, respectively. Linear range is 0.01–10.00 for the three sensors. These new sensors were used for the potentiometric titration of Ser-Cl using sodium tetraphenylborate as titrant. The surface morphologies of the prepared membranes with and without the modifier (ion-associate) were studied using scanning and atomic force microscopes. PMID:26257944

  17. Potentiometric Surface of the Magothy Aquifer in Southern Maryland, September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Late Cretaceous age in Southern Maryland during September 2007. The map is based on water-level measurements in 69 wells. The highest measured water level was 85 feet above sea level near the northern boundary and outcrop area of the aquifer in the north-central part of Anne Arundel County. The potentiometric surface declined towards the south. Local gradients were directed toward the center of a cone of depression in the Waldorf area that developed in response to pumping. Measured ground-water levels were as low as 90 feet below sea level in the Waldorf area.

  18. Potentiometric chip-based multipumping flow system for the simultaneous determination of fluoride, chloride, pH, and redox potential in water samples.

    PubMed

    Chango, Gabriela; Palacio, Edwin; Cerdà, Víctor

    2018-08-15

    A simple potentiometric chip-based multipumping flow system (MPFS) has been developed for the simultaneous determination of fluoride, chloride, pH, and redox potential in water samples. The proposed system was developed by using a poly(methyl methacrylate) chip microfluidic-conductor using the advantages of flow techniques with potentiometric detection. For this purpose, an automatic system has been designed and built by optimizing the variables involved in the process, such as: pH, ionic strength, stirring and sample volume. This system was applied successfully to water samples getting a versatile system with an analysis frequency of 12 samples per hour. Good correlation between chloride and fluoride concentration measured with ISE and ionic chromatography technique suggests satisfactory reliability of the system. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Yeast Based Sensors

    NASA Astrophysics Data System (ADS)

    Shimomura-Shimizu, Mifumi; Karube, Isao

    Since the first microbial cell sensor was studied by Karube et al. in 1977, many types of yeast based sensors have been developed as analytical tools. Yeasts are known as facultative anaerobes. Facultative anaerobes can survive in both aerobic and anaerobic conditions. The yeast based sensor consisted of a DO electrode and an immobilized omnivorous yeast. In yeast based sensor development, many kinds of yeast have been employed by applying their characteristics to adapt to the analyte. For example, Trichosporon cutaneum was used to estimate organic pollution in industrial wastewater. Yeast based sensors are suitable for online control of biochemical processes and for environmental monitoring. In this review, principles and applications of yeast based sensors are summarized.

  20. Sensor Access to the Cellular Microenvironment Using the Sensing Cell Culture Flask.

    PubMed

    Kieninger, Jochen; Tamari, Yaara; Enderle, Barbara; Jobst, Gerhard; Sandvik, Joe A; Pettersen, Erik O; Urban, Gerald A

    2018-04-26

    The Sensing Cell Culture Flask (SCCF) is a cell culture monitoring system accessing the cellular microenvironment in 2D cell culture using electrochemical microsensors. The system is based on microfabricated sensor chips embedded in standard cell culture flasks. Ideally, the sensor chips could be equipped with any electrochemical sensor. Its transparency allows optical inspection of the cells during measurement. The surface of the sensor chip is in-plane with the flask surface allowing undisturbed cell growth on the sensor chip. A custom developed rack system allows easy usage of multiple flasks in parallel within an incubator. The presented data demonstrates the application of the SCCF with brain tumor (T98G) and breast cancer (T-47D) cells. Amperometric oxygen sensors were used to monitor cellular respiration with different incubation conditions. Cellular acidification was accessed with potentiometric pH sensors using electrodeposited iridium oxide films. The system itself provides the foundation for electrochemical monitoring systems in 3D cell culture.

  1. Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, May 2008

    USGS Publications Warehouse

    Kinnaman, Sandra L.; Dixon, Joann F.

    2008-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 2008. Potentiometric contours are based on water-level measurements collected at 567 wells during the period May 6-May 27, near the end of the dry season. Some contours are inferred from previous potentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours. Measured values of the potentiometric surface ranged from 7 feet below NGVD29 near Fernandina Beach, Florida, to 124 feet above NGVD29 in Polk County, Florida. The average water level of the network in May 2008 was about 1 foot lower than the average in September 2007 following below-average rainfall during the dry season of 2007-08. Seasonal differences in network average water levels generally range from 4 to 6 feet. For 457 wells with previous measurements, May 2008 levels ranged from about 19 feet below to about 11 feet above September 2007 water levels. The average water level of the network in May 2008 was about 1 foot higher than the average in May 2007. For 544 wells with previous measurements, May 2008 levels ranged from about 8 feet below to about 13 feet above May 2007 water levels. Long-term hydrographs of ground-water levels for continuous and periodic wells are available

  2. Potentiometric urea biosensor based on an immobilised fullerene-urease bio-conjugate.

    PubMed

    Saeedfar, Kasra; Heng, Lee Yook; Ling, Tan Ling; Rezayi, Majid

    2013-12-06

    A novel method for the rapid modification of fullerene for subsequent enzyme attachment to create a potentiometric biosensor is presented. Urease was immobilized onto the modified fullerene nanomaterial. The modified fullerene-immobilized urease (C60-urease) bioconjugate has been confirmed to catalyze the hydrolysis of urea in solution. The biomaterial was then deposited on a screen-printed electrode containing a non-plasticized poly(n-butyl acrylate) (PnBA) membrane entrapped with a hydrogen ionophore. This pH-selective membrane is intended to function as a potentiometric urea biosensor with the deposition of C60-urease on the PnBA membrane. Various parameters for fullerene modification and urease immobilization were investigated. The optimal pH and concentration of the phosphate buffer for the urea biosensor were 7.0 and 0.5 mM, respectively. The linear response range of the biosensor was from 2.31 × 10-3 M to 8.28 × 10-5 M. The biosensor's sensitivity was 59.67 ± 0.91 mV/decade, which is close to the theoretical value. Common cations such as Na+, K+, Ca2+, Mg2+ and NH4+ showed no obvious interference with the urea biosensor's response. The use of a fullerene-urease bio-conjugate and an acrylic membrane with good adhesion prevented the leaching of urease enzyme and thus increased the stability of the urea biosensor for up to 140 days.

  3. Potentiometric Surface of the Ozark Aquifer in Northern Arkansas, 2007

    USGS Publications Warehouse

    Pugh, Aaron L.

    2008-01-01

    The Ozark aquifer in northern Arkansas is composed of dolomite, limestone, sandstone, and shale of Late Cambrian to Middle Devonian age, and ranges in thickness from approximately 1,100 feet to more than 4,000 feet. Hydrologically, the aquifer is complex, characterized by discrete and discontinuous flow components with large variations in permeability. The potentiometric-surface map, based on 58 well and 5 spring water-level measurements collected in 2007 in Arkansas and Missouri, has a maximum water-level altitude measurement of 1,169 feet in Carroll County and a minimum water-level altitude measurement of 118 feet in Randolph County. Regionally, the flow within the aquifer is to the south and southeast in the eastern and central part of the study area and to the west, northwest, and north in the western part of the study area. Comparing the 2007 potentiometric-surface map with a predevelopment potentiometric-surface map indicates general agreement between the two surfaces except in the northwestern part of the study area. Potentiometric-surface differences can be attributed to withdrawals related to increasing population, changes in public-supply sources, processes or water withdrawals outside the study area, or differences in data-collection or map-construction methods. The rapidly increasing population within the study area appears to have some effect on ground-water levels. Although, the effect appears to have been minimized by the development and use of surface-water distribution infrastructure, suggesting most of the incoming populations are fulfilling their water needs from surface-water sources. The conversion of some users from ground water to surface water may be allowing water levels in wells to recover (rise) or decline at a slower rate, such as in Benton, Carroll, and Washington Counties.

  4. Ferroelectric Dispersed Composite Solid Electrolyte for CO2 Gas Sensor

    NASA Astrophysics Data System (ADS)

    Singh, K.; Ambekar, P.; Bhoga, S. S.

    2002-12-01

    The Li2CO3:LiNbO3 composite system was investigated for the application in electrochemical gas sensor. The conductivity maximum is observed for 50Li2CO3+50LiNbO3. An enhancement in conductivity is understood to be due to the percolation threshold. The composite is also seen less sensitive to moisture. Potentiometric sensors are obtained using optimized composition. At the reference electrode, the activity of Li+ is fixed by using open reference electrode material. Good reversibility of cell emf was observed for PCO2 ranging from 200 ppm to 20% at 400°C. The cell response was Nernstian, following nearly two-electron reaction. The sensor showed negligible cross-sensitivity to moisture. Developed solid electrolyte not only exhibit shorter response time but also improves over all performance relative to the sensor based on pure carbonate.

  5. Highly selective direct determination of chlorate ions by using a newly developed potentiometric electrode based on modified smectite.

    PubMed

    Topcu, Cihan

    2016-12-01

    A novel polyvinyl chloride membrane chlorate (ClO 3 - ) selective electrode based on modified smectite was developed for the direct determination of chlorate ions and the potentiometric performance characteristics of its were examined. The best selectivity and sensitivity for chlorate ions were obtained for the electrode membrane containing ionophore/polyvinylchloride/o-nitrophenyloctylether in composition of 12/28/60 (w/w%). The proposed electrode showed a Nernstian response toward chlorate ions at pH=7 in the concentration range of 1×10 -7 -1×10 -1 M and the limit of detection was calculated as 9×10 -8 M from the constructed response plot. The linear slope of the electrode was -61±1mVdecade -1 for chlorate activity in the mentioned linear working range. The selectivity coefficients were calculated according to both the matched potential method and the separate solution method. The calculated selectivity coefficients showed that the electrode performed excellent selectivity for chlorate ions. The potentiometric response of electrode toward chlorate ions was found to be highly reproducible. The electrode potential was stable between pH=4-10 and it had a dynamic response time of <5s. The potentiometric behavior of the electrode in partial non-aqueous medium was also investigated and the obtained results (up to 5% (v/v) alcohol) were satisfactory. The proposed electrode was used during 15 weeks without any significant change in its potential response. Additionally, the electrode was very useful in water analysis studies such as dam water, river water, tap water, and swimming pool water where the direct determination of chlorate ions was required. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Potentiometric map of the Sparta aquifer system in Mississippi, fall, 1980

    USGS Publications Warehouse

    Wasson, B.E.

    1980-01-01

    This potentiometric map of the Sparta aquifer system is the tenth in a series of maps, prepared by the U.S. Geological Survey in cooperation with the Mississippi Department of Natural Resources, Bureau of Land and Water Resources, delineating the potentiometric surfaces of the major aquifers in Mississippi. In the outcrop area of the Sparta, the potentiometric surface is strongly affected by recharge from precipitation, by topography, and by drainage of the aquifer into streams. The potentiometric surface slopes downward generally to the west away from the area of outcrop and is strongly affected by large ground-water withdrawals in the Jackson, Yazoo City, Cleveland, Clarksdale, and Memphis areas. Historically, water levels in or near the outcrop of the Sparta have shown little or no long-term changes, but during the past 20 years, in much of the confined part of the aquifer, water levels have declined from 1 to 3 feet per year. (USGS)

  7. Chemical sensors for space applications

    NASA Technical Reports Server (NTRS)

    Bonting, Sjoerd L.

    1992-01-01

    The payload of the Space Station Freedom will include sensors for frequent monitoring of the water recycling process and for measuring the many biochemical parameters related to onboard experiments. This paper describes the sensor technologies and the types of transducers and selectors considered for these sensors. Particular attention is given to such aspects of monitoring of the water recycling process as the types of water use, the sources of water and their hazards, the sensor systems for monitoring, microbial monitoring, and monitoring toxic metals and organics. An approach for monitoring water recycling is suggested, which includes microbial testing with a potentiometric device (which should be in first line of tests), the use of an ion-selective electrode for inorganic ion determinations, and the use of optic fiber techniques for the determination of total organic carbon.

  8. Potentiometric Surface of the Magothy Aquifer in Southern Maryland, September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Late Cretaceous age in Southern Maryland during September 2009. The map is based on water-level measurements in 66 wells. The highest measured water level was 85 feet above sea level near the northern boundary and outcrop area of the aquifer in the north-central part of Anne Arundel County. The potentiometric surface declined towards the south. Local hydraulic gradients were directed toward the center of a cone of depression in the Waldorf area that developed in response to pumping. Measured groundwater levels were as low as 71 feet below sea level in the Waldorf area. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  9. Potentiometric map of the Winona-Tallahatta Aquifer in northwestern Mississippi, fall 1979

    USGS Publications Warehouse

    Wasson, B.E.

    1980-01-01

    The potentiometric map of the Winona-Tallahatta aquifer is one of a series of maps, prepared by the U.S. Geological Survey in cooperation with the Mississippi Department of Natural Resources , Bureau of Land and Water Resources, delineating the potentiometric surfaces of the major aquifers in Mississippi. In the outcrop area of the Winona-Tallahatta aquifer the potentiometric surface is strongly affected by recharge from precipitation, by topography, and by drainage of the aquifer by streams. The potentiometric surface slopes downward generally to the west away from the area of outcrop and is strongly affected by recharge from precipitation, by topography, and by drainage of the aquifer by streams. The potentiometric surface slopes downward generally to the west away from the area of outcrop and is strongly affected by pumpage from wells in Leflore, Sunflower , and Bolivar Counties, Historically, water levels in or near the outcrop of the Winona-Tallahatta have shown little or no long-term changes, but the heavy withdrawals in the confined part of the aquifer have caused long-term water-level declines of 1 to 2 feet per year. (USGS)

  10. Potentiometric Urea Biosensor Based on an Immobilised Fullerene-Urease Bio-Conjugate

    PubMed Central

    Saeedfar, Kasra; Heng, Lee Yook; Ling, Tan Ling; Rezayi, Majid

    2013-01-01

    A novel method for the rapid modification of fullerene for subsequent enzyme attachment to create a potentiometric biosensor is presented. Urease was immobilized onto the modified fullerene nanomaterial. The modified fullerene-immobilized urease (C60-urease) bioconjugate has been confirmed to catalyze the hydrolysis of urea in solution. The biomaterial was then deposited on a screen-printed electrode containing a non-plasticized poly(n-butyl acrylate) (PnBA) membrane entrapped with a hydrogen ionophore. This pH-selective membrane is intended to function as a potentiometric urea biosensor with the deposition of C60-urease on the PnBA membrane. Various parameters for fullerene modification and urease immobilization were investigated. The optimal pH and concentration of the phosphate buffer for the urea biosensor were 7.0 and 0.5 mM, respectively. The linear response range of the biosensor was from 2.31 × 10−3 M to 8.28 × 10−5 M. The biosensor's sensitivity was 59.67 ± 0.91 mV/decade, which is close to the theoretical value. Common cations such as Na+, K+, Ca2+, Mg2+ and NH4+ showed no obvious interference with the urea biosensor's response. The use of a fullerene-urease bio-conjugate and an acrylic membrane with good adhesion prevented the leaching of urease enzyme and thus increased the stability of the urea biosensor for up to 140 days. PMID:24322561

  11. ISFET-based sensor signal processor chip design for environment monitoring applications

    NASA Astrophysics Data System (ADS)

    Chung, Wen-Yaw; Yang, Chung-Huang; Wang, Ming-Ga

    2004-12-01

    In recent years Ion-Sensitive Field Effect Transistor (ISFET) based transducers create valuable applications in physiological data acquisition and environment monitoring. This paper presents a mixed-mode ASIC design for potentiometric ISFET-based bio-chemical sensor applications including H+ sensing and hand-held pH meter. For battery power consideration, the proposed system consists of low voltage (3V) analog front-end readout circuits and digital processor has been developed and fabricated in a 0.5mm double-poly double-metal CMOS technology. To assure that the correct pH value can be measured, the two-point calibration circuitry based on the response of standard pH4 and pH7 buffer solution has been implemented by using algorithmic state machine hardware algorithms. The measurement accuracy of the chip is 10 bits and the measured range between pH 2 to pH 12 compared to ideal values is within the accuracy of 0.1pH. For homeland environmental applications, the system provide rapid, easy to use, and cost-effective on-site testing on the quality of water, such as drinking water, ground water and river water. The processor has a potential usage in battery-operated and portable devices in environmental monitoring applications compared to commercial hand-held pH meter.

  12. Concentration-related response potentiometric titrations to study the interaction of small molecules with large biomolecules.

    PubMed

    Hamidi-Asl, Ezat; Daems, Devin; De Wael, Karolien; Van Camp, Guy; Nagels, Luc J

    2014-12-16

    In the present paper, the utility of a special potentiometric titration approach for recognition and calculation of biomolecule/small-molecule interactions is reported. This approach is fast, sensitive, reproducible, and inexpensive in comparison to the other methods for the determination of the association constant values (Ka) and the interaction energies (ΔG). The potentiometric titration measurement is based on the use of a classical polymeric membrane indicator electrode in a solution of the small-molecule ligand. The biomolecule is used as a titrant. The potential is measured versus a reference electrode and transformed into a concentration-related signal over the entire concentration interval, also at low concentrations, where the millivolt (y-axis) versus log canalyte (x-axis) potentiometric calibration curve is not linear. In the procedure, Ka is calculated for the interaction of cocaine with a cocaine binding aptamer and with an anticocaine antibody. To study the selectivity and cross-reactivity, other oligonucleotides and aptamers are tested, as well as other small ligand molecules such as tetrakis(4-chlorophenyl)borate, metergoline, lidocaine, and bromhexine. The calculated Ka compared favorably to the value reported in the literature using surface plasmon resonance. The potentiometric titration approach called "concentration-related response potentiometry" is used to study molecular interaction for seven macromolecular target molecules and four small-molecule ligands.

  13. Map showing how the potentiometric surface of the Magothy Aquifer of August 1980 differed from the potentiometric surface of September 1977, in southern Maryland

    USGS Publications Warehouse

    Mack, Frederick K.; Wheeler, J.C.; Curtin, Stephen E.

    1982-01-01

    The map is based on the differences between two sets of water-level measurements made in 65 observation wells. One set was made in 1977, a relatively dry year, and the other set was made in 1980, another relatively dry year. The map shows that the potentiometric surface was higher in 1980, by as much as 9 feet, than it was in 1977, in a band a few miles wide near the outcrop and subcrop areas of the aquifer in northern Prince Georges County and central Anne Arundel County. In the remainder of the map area, the 1980 potentiometric surface was lower than it had been in 1977, with declines as great as 20 feet measured in well fields at Waldorf and Chalk Point. The network of observation wells was developed and is operated and maintained as part of the cooperative program between the U.S. Geological Survey and agencies of the Maryland Department of Natural Resources. (USGS)

  14. Solid State Gas Sensor Research in Germany – a Status Report

    PubMed Central

    Moos, Ralf; Sahner, Kathy; Fleischer, Maximilian; Guth, Ulrich; Barsan, Nicolae; Weimar, Udo

    2009-01-01

    This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor. PMID:22408529

  15. Potentiometric determination of trypsin using a polymeric membrane polycation-sensitive electrode based on current-controlled reagent delivery.

    PubMed

    Chen, Yan; Ding, Jiawang; Qin, Wei

    2012-12-01

    A potentiometric biosensor for the determination of trypsin is described based on current-controlled reagent delivery. A polymeric membrane protamine-sensitive electrode with dinonylnaphthalene sulfonate as cation exchanger is used for in situ generation of protamine. Diffusion of protamine across the polymeric membrane can be controlled precisely by applying an external current. The hydrolysis catalyzed with trypsin in sample solution decreases the concentration of free protamine released at the sample-membrane interface and facilitates the stripping of protamine out of the membrane surface via the ion-exchange process with sodium ions from the sample solution, thus decreasing the membrane potential, by which the protease can be sensed potentiometrically. The influences of anodic current amplitude, current pulse duration and protamine concentration in the inner filling solution on the membrane potential response have been studied. Under optimum conditions, the proposed protamine-sensitive electrode is useful for continuous and reversible detection of trypsin over the concentration range of 0.5-5UmL(-1) with a detection limit of 0.3UmL(-1). The proposed detection strategy provides a rapid and reagentless way for the detection of protease activities and offers great potential in the homogeneous immunoassays using proteases as labels. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Ionic effect investigation of a potentiometric sensor for urea and surface morphology observation of entrapped urease/polypyrrole matrix.

    PubMed

    Syu, Mei-Jywan; Chang, Yu-Sung

    2009-04-15

    Potentio-dynamic polymerization of buffered urease and pyrrole monomer onto carbon papers was conducted to fabricate an immobilized urease electrode for measuring the urea concentration. To use carbon paper as the substrate for the electro-growth of polypyrrole matrix not only created sufficient adhesion of the conducting polymer layer but also provided superior entrapment of urease enzymes. The potentiometric response corresponding to ammonia, the product formed from the urease catalyzed urea reaction, was employed for the urea concentration measurement. Scanning electron microscopic photographs showed that the polypyrrole matrix deposited on the carbon papers appeared to be of a cylindrical nanotube shape. The charge density applied in the polymerization was found to affect the potentiometric response while the potential-scanning rate showed minor influence. The composite electrodes had high sensitivity in urea detection, showing a response linear to the logarithm of the urea concentration in the range of 10(-3) to 10 mM. The detection of urea solution prepared in water and buffer was also compared. Ionic effect on the sensing of urea solution was investigated. By comparing the data reported in literature, the urease/polypyrrole/carbon paper electrode developed in this work showed superior long-term stability and reusability. The detection of urea in serum was also well performed.

  17. Potentiometric Surface of the Magothy Aquifer in Southern Maryland, September 2002

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2003-01-01

    This report presents a map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Upper Cretaceous age in Southern Maryland during September 2002. The map is based on water-level measurements in 79 wells. The highest measured water level was 83 feet above sea level near the northern boundary and outcrop area of the aquifer in the north-central part of Anne Arundel County. The potentiometric surface declined towards the south and east. Local gradients were directed toward the centers of two cones of depression that developed in response to pumping. These cones of depression were centered around well fields in the Waldorf area and at the Chalk Point power plant. Measured ground-water levels were as low as 81 feet below sea level in the Waldorf area and 75 feet below sea level at Chalk Point.

  18. Potentiometric Surface of the Patuxent Aquifer in Southern Maryland, September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the potentiometric surface of the Patuxent aquifer in the Patuxent Formation of Early Cretaceous age in Southern Maryland during September 2007. The map is based on water-level measurements in 41 wells. The highest measured water level was 165 feet above sea level near the northwestern boundary and in the outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined south towards well fields at Glen Burnie, Bryans Road, the Morgantown power plant, and the Chalk Point power plant. The measured ground-water levels were 81 feet below sea level at Glen Burnie, 47 feet below sea level southwest of Bryans Road, 27 feet below sea level at the Morgantown power plant, and 24 feet below sea level at the Chalk Point power plant.

  19. Determination of pKa values of alendronate sodium in aqueous solution by piecewise linear regression based on acid-base potentiometric titration.

    PubMed

    Ke, Jing; Dou, Hanfei; Zhang, Ximin; Uhagaze, Dushimabararezi Serge; Ding, Xiali; Dong, Yuming

    2016-12-01

    As a mono-sodium salt form of alendronic acid, alendronate sodium presents multi-level ionization for the dissociation of its four hydroxyl groups. The dissociation constants of alendronate sodium were determined in this work by studying the piecewise linear relationship between volume of titrant and pH value based on acid-base potentiometric titration reaction. The distribution curves of alendronate sodium were drawn according to the determined pKa values. There were 4 dissociation constants (pKa 1 =2.43, pKa 2 =7.55, pKa 3 =10.80, pKa 4 =11.99, respectively) of alendronate sodium, and 12 existing forms, of which 4 could be ignored, existing in different pH environments.

  20. Graphene-based potentiometric biosensor for the immediate detection of living bacteria.

    PubMed

    Hernández, Rafael; Vallés, Cristina; Benito, Ana M; Maser, Wolfgang K; Rius, F Xavier; Riu, Jordi

    2014-04-15

    In this communication we present a potentiometric aptasensor based on chemically modified graphene (transducer layer of the aptasensor) and aptamers (sensing layer). Graphene oxide (GO) and reduced graphene oxide (RGO) are the basis for the construction of two versions of the aptasensor for the detection of a challenging living organism such as Staphylococcus aureus. In these two versions, DNA aptamers are either covalently (in the GO case) or non-covalently (in the RGO case) attached to the transducer layer. In both cases we are able to selectively detect a single CFU/mL of S. aureus in an assay close to real time, although the noise level associated to the aptasensors made with RGO is lower than the ones made with GO. These new aptasensors, that show a high selectivity, are characterized by the simplicity of the technique and the materials used for their construction while offering ultra-low detection limits in very short time responses in the detection of microorganisms. © 2013 Published by Elsevier B.V.

  1. High-temperature potentiometric oxygen sensor with internal reference

    DOEpatents

    Routbort, Jules L [Hinsdale, IL; Singh, Dileep [Naperville, IL; Dutta, Prabir K [Worthington, OH; Ramasamy, Ramamoorthy [North Royalton, OH; Spirig, John V [Columbus, OH; Akbar, Sheikh [Hilliard, OH

    2011-11-15

    A compact oxygen sensor is provided, comprising a mixture of metal and metal oxide an enclosure containing said mixture, said enclosure capable of isolating said mixture from an environment external of said enclosure, and a first wire having a first end residing within the enclosure and having a second end exposed to the environment. Also provided is a method for the fabrication of an oxygen sensor, the method comprising confining a metal-metal oxide solid mixture to a container which consists of a single material permeable to oxygen ions, supplying an electrical conductor having a first end and a second end, whereby the first end resides inside the container as a reference (PO.sub.2).sup.ref, and the second end resides outside the container in the atmosphere where oxygen partial pressure (PO.sub.2).sup.ext is to be measured, and sealing the container with additional single material such that grain boundary sliding occurs between grains of the single material and grains of the additional single material.

  2. Anion recognition using newly synthesized hydrogen bonding disubstituted phenylhydrazone-based receptors: poly(vinyl chloride)-based sensor for acetate.

    PubMed

    Gupta, Vinod K; Goyal, Rajendra N; Sharma, Ram A

    2008-08-15

    A potentiometric acetate-selective sensor, based on the use of butane-2,3-dione,bis[(2,4-dinitrophenyl)hydrazone] (BDH) as a neutral carrier in poly(vinyl chloride) (PVC) matrix, is reported. Effect of various plasticizers and cation excluder, cetryaltrimethylammonium bromide (CTAB) was studied. The best performance was obtained with a membrane composition of PVC:BDH:CTAB ratio (w/w; mg) of 160:8:8. The sensor exhibits significantly enhanced selectivity toward acetate ions over a wide concentration range 5.0 x 10(-6) to 1.0 x 10(-1)M with a lower detection limit of 1.2 x 10(-6)M within pH range 6.5-7.5 with a response time of <15s and a Nernstian slope of 60.3+/-0.3 mV decade(-1) of activity. Influences of the membrane composition, and possible interfering anions were investigated on the response properties of the electrode. Fast and stable response, good reproducibility and long-term stability are demonstrated. The sensor has a response time of 15s and can be used for at least 65 days without any considerable divergence in their potential response. Selectivity coefficients determined with the separate solution method (SSM) and fixed interference method (FIM) indicate that high selectivity for acetate ion. The proposed electrode shows fairly good discrimination of acetate from several inorganic and organic anions. It was successfully applied to direct determination of acetate within food preservatives. Total concentration of acetic acid in vinegar samples were determined by direct potentiometry and the values agreed with those mentioned by the manufacturers.

  3. Fabrication and Evaluation of a Micro(Bio)Sensor Array Chip for Multiple Parallel Measurements of Important Cell Biomarkers

    PubMed Central

    Pemberton, Roy M.; Cox, Timothy; Tuffin, Rachel; Drago, Guido A.; Griffiths, John; Pittson, Robin; Johnson, Graham; Xu, Jinsheng; Sage, Ian C.; Davies, Rhodri; Jackson, Simon K.; Kenna, Gerry; Luxton, Richard; Hart, John P.

    2014-01-01

    This report describes the design and development of an integrated electrochemical cell culture monitoring system, based on enzyme-biosensors and chemical sensors, for monitoring indicators of mammalian cell metabolic status. MEMS technology was used to fabricate a microwell-format silicon platform including a thermometer, onto which chemical sensors (pH, O2) and screen-printed biosensors (glucose, lactate), were grafted/deposited. Microwells were formed over the fabricated sensors to give 5-well sensor strips which were interfaced with a multipotentiostat via a bespoke connector box interface. The operation of each sensor/biosensor type was examined individually, and examples of operating devices in five microwells in parallel, in either potentiometric (pH sensing) or amperometric (glucose biosensing) mode are shown. The performance characteristics of the sensors/biosensors indicate that the system could readily be applied to cell culture/toxicity studies. PMID:25360580

  4. Potentiometric surface of the upper Patapsco Aquifer in southern Maryland, September 1991

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, D.C.; Mack, Frederick K.

    1993-01-01

    A map showing the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Cretaceous age in southern Maryland during September 1991 was prepared from water levels measured in wells. The potentiometric surface was at least 70 feet above sea level near the northwestern boundary and outcrop area of the aquifer in a topographically high area of Anne Arundel County, and at least 56 feet above sea level in a similar setting in Prince Georges County. From these high areas, the potentiometric surface declined to the south and southeast toward large well fields in the Annapolis and Waldorf areas and at the Chalk Point powerplant.

  5. Potentiometric titration of metal ions in ethanol.

    PubMed

    Gibson, Graham T T; Mohamed, Mark F; Neverov, Alexei A; Brown, R S

    2006-09-18

    The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented.

  6. Potentiometric surface of the Floridan Aquifer and its use in management of water resources, St. Johns River Water Management District, Florida

    USGS Publications Warehouse

    Rodis, Harry George; Munch, D.A.

    1983-01-01

    The Floridan aquifer supplies most of the fresh groundwater for municipal, industrial, and agricultural uses within the 12,400 sq mi St. Johns River Water Management District. Because of the growing demand for water and the variation in rainfall, resource managers need timely information on short-term and long-term changes in the availability of fresh water. The purpose of this report is to explain potentiometric surface maps and their value in assessing the resource, particularly during drought conditions. The Floridan aquifer is recharged by rainfall falling directly on the outcrop of the aquifer, and, where the aquifer is overlain by the surficial aquifer with the water table above the potentiometric surface of the Floridan, by water infiltrating downward from the overlying surficial aquifer. Water is discharged by pumping and free-flowing wells, springflow, and upward leakage into overlying formations, streams, and lakes or into the ocean. Fluctuations in the potentiometric surface reflect net gains (recharge) or losses (discharge) of water stored in the aquifer. Net gains occur during the wet season (June through September) when recharge exceeds discharge and causes the potentiometric surface to rise in most places. Net losses in storage, and declines in the potentiometric surface, follow during the dry season (October through May) when discharge exceeds recharge. Seasonal changes in the potentiometric surface, based on a 2-yr average of water level measurements during May and September 1977, and May and September 1978, are illustrated. Two of the greater long-term declines in the potentiometric surface have occurred in the growing metropolitan areas of Jacksonville and Orlando-Winter Park, the two largest public suppliers of water in the Water Management District. Municipal pumpage increased in Jacksonville from 37 million gallons per day (mgd) in 1961 to 56 mgd in 1980. The increased pumpage and a deficiency in rainfall of 15.8 inches contributed to a

  7. Potentiometric Surface of the Patuxent Aquifer in Southern Maryland, September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the potentiometric surface of the Patuxent aquifer in the Patuxent Formation of Early Cretaceous age in Southern Maryland during September 2009. The map is based on water-level measurements in 42 wells. The highest measured water level was 169 feet above sea level in the outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined south towards well fields at Glen Burnie, Bryans Road, the Morgantown power plant, and the Chalk Point power plant. The measured groundwater levels were 78 feet below sea level at Glen Burnie, 56 feet below sea level at Bryans Road, 29 feet below sea level at the Morgantown power plant, and 28 feet below sea level at the Chalk Point power plant. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  8. Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 2001

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2002-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2001. The map is based on water-level measurements in 76 wells. The potentiometric surface was highest at 40 feet above sea level near the northern boundary and outcrop area of the aquifer in the central part of Anne Arundel County, and was below sea level in the remainder of the study area. The hydraulic gradient was directed southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. A cone of depression formed in northern Calvert County due to pumpage at Chesapeake Beach and North Beach. The water level has declined to 44 feet below sea level in this area. The lowest measurement was 160 feet below sea level at the center of a cone of depression at Lexington Park.

  9. Potentiometric surface of the middle Potomac Aquifer in Virginia 1993

    USGS Publications Warehouse

    Hammond, E.C.; McFarland, E.R.; Focazio, M.J.

    1994-01-01

    Ground-water level measurements from 50 wells in the middle Potomac aquifer in the Coastal Plain Physiographic Province of Virginia in 1993 were used to prepare a map of the potentiometric surface of the aquifer. The map shows the potentiometric surface of the middle Potomac aquifer sharply declining eastward from nearly 100 feet above sear level near the western boundary of the aquifer to 20 feet below sea level, and continues declining gradually toward the Chesapeake Bay and Atlantic Ocean. A cone of depression is apparent around well fields in Franklin, Virginia. The potentiometric surface also appears to be affected by pumping in the area of Henrico County and Hanover County, Virginia. The highest ground-water-level measurement was 89 feet above sea level in Chesterfield County near Richmond, and the lowest ground-water-level measurement was 179 feet below sea level in southeastern Isle of Wight County, Virginia.

  10. Open-Source Low-Cost Wireless Potentiometric Instrument for pH Determination Experiments

    ERIC Educational Resources Information Center

    Jin, Hao; Qin, Yiheng; Pan, Si; Alam, Arif U.; Dong, Shurong; Ghosh, Raja; Deen, M. Jamal

    2018-01-01

    pH determination is an essential experiment in many chemistry laboratories. It requires a potentiometric instrument with extremely low input bias current to accurately measure the voltage between a pH sensing electrode and a reference electrode. In this technology report, we propose an open-source potentiometric instrument for pH determination…

  11. Cyclodextrins Based Electrochemical Sensors for Biomedical and Pharmaceutical Analysis.

    PubMed

    Lenik, Joanna

    2017-01-01

    Electrochemical sensors are very convenient devices, as they may be used in a lot of fields starting from the food industry to environmental monitoring and medical diagnostics. They offer the values of simple design, reversible and reproducible measurements, as well as ensuring precise and accurate analytical information. Compared with other methods, electrochemical sensors are relatively simple as well as having low costs, which has led to intensive development, especially in the field of medicine and pharmaceuticals within the last decade. Recently, the number of publications covering the determination of aminoacids, dopamine, cholesterol, uric acid, biomarkers, vitamins and other pharmaceutical and biological compounds has significantly increased. Many possible types of such sensors and biosensors have been proposed: owing to the kind of the detection-potentiometric voltametric, amperometry, and the materials that can be used for, e.g. designing molecular architecture of the electrode/solution interface, carbon paste, carbon nanotubes, glass carbon, graphite, graphene, PVC, conductive polymers and/or nanoparticles. The active compounds which provide the complex formation with analyte (in the case of non-current techniques) or activate biomolecules electrochemically by particle recognition and selective preconcentration of analyte on the electrode surface (in the case of current techniques) are the most recently used cyclodextrins. These macrocyclic compounds have the ability to interact with a large diversity of guest particles to form complexes of the type of guest host, for example, with particles from drugs, biomolecules, through their hydrophilic outer surface and lipophilic inner cavities. Cyclodextrins have been the subject of frequent electrochemical studies that focused mostly on both their interactions in a solid state and in solution. The process of preparing of CDs modified electrodes would, consequently, open new avenues for new electrochemical

  12. Potentiometric-surface map of the Wyodak-Anderson Coal Bed, Powder River Structural Basin, Wyoming, 1973-84

    USGS Publications Warehouse

    Daddow, Pamela B.

    1986-01-01

    Previous water level maps of shallow aquifers in the Powder River structural basin in Wyoming were based on water levels from wells completed in different stratigraphic intervals within thick sequences of sedimentary rocks. A potentiometric surface using water levels from a single aquifer had never been mapped throughout the basin. The sandstone aquifers in the Fort Union Formation of Paleocene age and the Wasatch Formation of Eocene age are discontinuous and lenticular, and do not extend even short distances. Coal aquifers are more continuous and the Wyodak-Anderson coal bed, in the Fort Union Formation, has been mapped in much of the Powder River structural basin in Wyoming. Water level altitudes in the Wyodak-Anderson coal bed and other stratigraphically equivalent coal beds were mapped to determine if they represent a continuous potentiometric surface in the Powder River structural basin. The potentiometric surface, except in the vicinity of the Wyodak mine east of Gillette, represents a premining condition as it was based on water level measurements made during 1973-84 that were not significantly affected by mining. The map was prepared in cooperation with the U.S. Bureau of Land Management. (Lantz-PTT)

  13. Low-voltage analog front-end processor design for ISFET-based sensor and H+ sensing applications

    NASA Astrophysics Data System (ADS)

    Chung, Wen-Yaw; Yang, Chung-Huang; Peng, Kang-Chu; Yeh, M. H.

    2003-04-01

    This paper presents a modular-based low-voltage analog-front-end processor design in a 0.5mm double-poly double-metal CMOS technology for Ion Sensitive Field Effect Transistor (ISFET)-based sensor and H+ sensing applications. To meet the potentiometric response of the ISFET that is proportional to various H+ concentrations, the constant-voltage and constant current (CVCS) testing configuration has been used. Low-voltage design skills such as bulk-driven input pair, folded-cascode amplifier, bootstrap switch control circuits have been designed and integrated for 1.5V supply and nearly rail-to-rail analog to digital signal processing. Core modules consist of an 8-bit two-step analog-digital converter and bulk-driven pre-amplifiers have been developed in this research. The experimental results show that the proposed circuitry has an acceptable linearity to 0.1 pH-H+ sensing conversions with the buffer solution in the range of pH2 to pH12. The processor has a potential usage in battery-operated and portable healthcare devices and environmental monitoring applications.

  14. Potentiometric surface map of the Magothy aquifer in southern Maryland, September, 2003

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2005-01-01

    This report presents a map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Upper Cretaceous age in Southern Maryland during September 2002. The map is based on water-level measurements in 79 wells. The highest measured water level was 83 feet above sea level near the northern boundary and outcrop area of the aquifer in the north-central part of Anne Arundel County. The potentiometric surface declined towards the south and east. Local gradients were directed toward the centers of two cones of depression that developed in response to pumping. These cones of depression were centered around well fields in the Waldorf area and at the Chalk Point power plant. Measured ground-water levels were as low as 81 feet below sea level in the Waldorf area and 75 feet below sea level at Chalk Point.

  15. Potentiometric analytical microsystem based on the integration of a gas-diffusion step for on-line ammonium determination in water recycling processes in manned space missions.

    PubMed

    Calvo-López, Antonio; Ymbern, Oriol; Puyol, Mar; Casalta, Joan Manel; Alonso-Chamarro, Julián

    2015-05-18

    The design, construction and evaluation of a versatile cyclic olefin copolymer (COC)-based continuous flow potentiometric microanalyzer to monitor the presence of ammonium ion in recycling water processes for future manned space missions is presented. The microsystem integrates microfluidics, a gas-diffusion module and a detection system in a single substrate. The gas-diffusion module was integrated by a hydrophobic polyvinylidene fluoride (PVDF) membrane. The potentiometric detection system is based on an all-solid state ammonium selective electrode and a screen-printed Ag/AgCl reference electrode. The analytical features provided by the analytical microsystem after the optimization process were a linear range from 0.15 to 500 mg L(-1) and a detection limit of 0.07 ± 0.01 mg L(-1). Nevertheless, the operational features can be easily adapted to other applications through the modification of the hydrodynamic variables of the microfluidic platform. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Potentiometric surface of the Magothy Aquifer in southern Maryland, September 1991

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, D.C.; Mack, Frederick K.

    1993-01-01

    A map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in southern Maryland during September 1991 was prepared from water levels measured in 89 wells. The potentiometric surface was highest near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties. Regionally, the potentiometric surface sloped gently downward toward the southeast, and the local gradients were directed toward the centers of 3 cones of depression that have developed in response to pumping. These cones were centered around well fields in the Annapolis, Waldorf, and Chalk Point areas. Groundwater levels were more than 50 feet below sea level in the Waldorf area, nearly 50 feet below sea level at Chalk Point, and greater than 10 feet below sea level near Annapolis.

  17. Potentiometric surface of the Magothy Aquifer in southern Maryland, September 1994

    USGS Publications Warehouse

    Curtin, Stephen E.; Mack, Frederick K.; Andreasen, David C.

    1995-01-01

    A map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in southern Maryland during September 1994 was prepared from water levels measured in 85 wells. The potentiometric surface was highest near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties. Regionally, the potentiometric surface sloped gently downward toward the southeast, and the local gradients were directed toward the centers of three cones of depression that have developed in response to pumping. These cones were centered around well fields in the Annapolis, Waldorf, and Chalk Point areas. Ground-water levels were as low as 60 feet below sea level in the Waldorf area, more than 45 feet below sea level at Chalk Point, and almost 15 feet below sea level near Annapolis.

  18. Potentiometric Surface of the Magothy Aquifer in Southern Maryland, September 1995

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Mack, Frederick K.

    1996-01-01

    A map showing the potentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in southern Maryland during September 1995 was prepared from water-level measurements in 92 wells. The potentiometric surface was highest near the northwestern boundaryand outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties. Regionally, the potentiometric surface sloped gently downward towards the southeast and the local gradients were directed toward the centers of three cones of depression that have developed in response to pumping. These cones were centeredaround well fields in the Annapolis, Waldorf, and Chalk Point areas. Ground-water levels were as low as 63 feet below sea level in the Waldorf area, more than 50 feet below sea level at Chalk Point, and almost 20 feet below sea level near Annapolis.

  19. Information-based self-organization of sensor nodes of a sensor network

    DOEpatents

    Ko, Teresa H [Castro Valley, CA; Berry, Nina M [Tracy, CA

    2011-09-20

    A sensor node detects a plurality of information-based events. The sensor node determines whether at least one other sensor node is an information neighbor of the sensor node based on at least a portion of the plurality of information-based events. The information neighbor has an overlapping field of view with the sensor node. The sensor node sends at least one communication to the at least one other sensor node that is an information neighbor of the sensor node in response to at least one information-based event of the plurality of information-based events.

  20. Potentiometric surface of the Magothy Aquifer in southern Maryland during September 1988

    USGS Publications Warehouse

    Mack, Frederick K.; Andreasen, David C.; Curtin, Stephen E.; Wheeler, Judith C.

    1990-01-01

    A map showing the potentiometric surface of the Magothy aquifer in southern Maryland during the fall of 1988 was prepared from water-level measurements in 83 observation wells. The potentiometric surface was highest near the northwest boundary and outcrop area of the aquifer in topographically high locations of Anne Arundel and Prince Georges Counties. The hydraulic gradient in the study area was generally southeastward or toward the centers of three cones of depression that have developed in response to pumping stresses. These cones formed around well fields in the Annapolis, Waldorf, and Chalk Point areas. The potentiometric surface of the Magothy aquifer was more than 40 ft below sea level in parts of the Waldorf and Chalk Point areas. (USGS)

  1. Synthesis of nano-sized hydrogen phosphate-imprinted polymer in acetonitrile/water mixture and its use as a recognition element of hydrogen phosphate selective all-solid state potentiometric electrode.

    PubMed

    Alizadeh, Taher; Atayi, Khalil

    2018-02-01

    Herein, a new recipe is introduced for the preparation of hydrogen phosphate ion-imprinted polymer nanoparticles (nano-IIP) in acetonitrile/water (63.5:36.5) using phosphoric acid as the template. The nano-IIP obtained was used as the recognition element of a carbon paste potentiometric sensor. The IIP electrode showed a Nernstian response to hydrogen phosphate anion; whereas, the non-imprinted polymer (NIP)-based electrode had no considerable sensitivity to the anion. The presence of both methacrylic acid and vinyl pyridine in the IIP structure, as well as optimization of the functional monomers-template proportion, was found to be important to observe the sensing capability of the IIP electrode. The nano-IIP electrode showed a dynamic linear range of 1 × 10 -5 -1 × 10 -1  mol L-1, Nernstian slope of 30.6 ± (0.5) mV decade -1 , response time of 25 seconds, and detection limit of 4.0 × 10 -6  mol L -1 . The utility of the electrodes was checked by potentiometric titration of hydrogen phosphate with La 3+ solution. Copyright © 2017 John Wiley & Sons, Ltd.

  2. The difference between the potentiometric surfaces of the Aquia Aquifer of September 1982 and September 1995 in Southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Mack, Frederick K.

    1996-01-01

    A map showing the net change in the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in southern Maryland was based on water levels measured in 66 wells from September 1982 to September 1995 and shows that the decline of the potentiometric surface during the 13-year period was 20 to 30 feet in most of the area. The decline was more than 50 feet in the Lexington Park area and more than 60 feet at Solomons Island.

  3. The difference between the potentiometric surfaces of the Magothy aquifer, September 1975 and September 2003 in southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2005-01-01

    This report presents a map showing the change in the potentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in Southern Maryland for September 1975 and September 2003. The map, based on water level measurements in 51 wells, shows that during the 28-year period, the potentiometric surface had no change at the outcrop area, which is in the northernmost part of the study area, but declined 71 feet at Waldorf. Waldorf is located near the southwesternmost part of the study area, and approaches the downdip boundary of the aquifer.

  4. The Difference Between the Potentiometric Surfaces of the Magothy Aquifer in Southern Maryland, September 1975 and September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the change in the potentiometric surface of the Magothy aquifer in the Magothy Formation of Late Cretaceous age in Southern Maryland for September 1975 and September 2007. The map, based on water-level measurements in 51 wells, shows that during the 32-year period, the potentiometric surface had no change at the outcrop area, which is in the northernmost part of the study area, but declined 90 feet at Waldorf. Waldorf is located near the southwesternmost part of the study area, and approaches the downdip boundary of the aquifer.

  5. Potentiometric surfaces of the Arnold Engineering Development Complex Area, Arnold Air Force Base, Tennessee, May and September 2011

    USGS Publications Warehouse

    Haugh, Connor J.; Robinson, John A.

    2016-01-29

    During May 2011, when water levels were near seasonal highs, water-level data were collected from 374 monitoring wells; and during September 2011, when water levels were near seasonal lows, water-level data were collected from 376 monitoring wells. Potentiometric surfaces were mapped by contouring altitudes of water levels measured in wells completed in the shallow aquifer, the upper and lower parts of the Manchester aquifer, and the Fort Payne aquifer. Water levels are generally 2 to 14 feet lower in September compared to May. The potentiometric-surface maps for all aquifers indicate a groundwater depression at the J4 test cell. Similar groundwater depressions in the shallow and upper parts of the Manchester aquifer are within the main testing area at the Arnold Engineering Development Complex at dewatering facilities.

  6. Construction and performance characterization of screen printed and carbon paste ion selective electrodes for potentiometric determination of naphazoline hydrochloride in pharmaceutical preparations.

    PubMed

    Frag, Eman Y Z; Mohamed, Gehad G; El-Dien, F A Nour; Mohamed, Marwa E

    2011-01-21

    This paper describes the development of screen-printed (SPE) and carbon paste (CPE) sensors for the rapid and sensitive quantification of naphazoline hydrochloride (NPZ) in pharmaceutical formulations. This work compares the electroactivity of conventional carbon paste and screen-printed carbon paste electrodes towards potentiometric titration of NPZ. The repeatability and accuracy of measurements performed in the analysis of these pharmaceutical matrices using new screen printed sensors were evaluated. The influence of the electrode composition, conditioning time of the electrode and pH of the test solution, on the electrode performance were investigated. The drug electrode showed Nernstain responses in the concentration range from 1 × 10(-6) to 1 × 10(-2) mol L(-1) with slopes of 57.5 ± 1.3 and 55.9 ± 1.6 mV per decade for SPE and CPE, respectively, and was found to be very precise and usable within the pH range 3-8. These sensors exhibited a fast response time (about 3 s for both SPE and CPE, respectively), a low detection limit (3.5 × 10(-6) and 1.5 × 10(-6) M for SPE and CPE, respectively), a long lifetime (3 and 2 months for SPE and CPE, respectively) and good stability. The selectivity of the electrode toward a large number of inorganic cations, sugars and amino acids was tested. It was applied to potentiometric determination of NPZ in pure state and pharmaceutical preparation under batch conditions. The percentage recovery values for the assay of NPZ in tablets (relative standard deviations ≤0.3% for n = 4) were compared well with those obtained by the official method.

  7. Current-biased potentiometric NOx sensor for vehicle emissions

    DOEpatents

    Martin, Louis Peter [Castro Valley, CA; Pham, Ai Quoc [San Jose, CA

    2006-12-26

    A nitrogen oxide sensor system for measuring the amount of nitrogen oxide in a gas. A first electrode is exposed to the gas. An electrolyte is positioned in contact with the first electrode. A second electrode is positioned in contact with the electrolyte. A means for applying a fixed current between the first electrode and the second electrode and monitoring the voltage required to maintain the fixed current provides a measurement of the amount of nitrogen oxide in the gas.

  8. Simple Potentiometric Determination of Reducing Sugars

    ERIC Educational Resources Information Center

    Moresco, Henry; Sanson, Pedro; Seoane, Gustavo

    2008-01-01

    In this article a potentiometric method for reducing sugar quantification is described. Copper(II) ion reacts with the reducing sugar (glucose, fructose, and others), and the excess is quantified using a copper wire indicator electrode. In order to accelerate the kinetics of the reaction, working conditions such as pH and temperature must be…

  9. Multifunctional potentiometric gas sensor array with an integrated temperature control and temperature sensors

    DOEpatents

    Blackburn, Bryan M; Wachsman, Eric D

    2015-05-12

    Embodiments of the subject invention relate to a gas sensor and method for sensing one or more gases. An embodiment incorporates an array of sensing electrodes maintained at similar or different temperatures, such that the sensitivity and species selectivity of the device can be fine tuned between different pairs of sensing electrodes. A specific embodiment pertains to a gas sensor array for monitoring combustion exhausts and/or chemical reaction byproducts. An embodiment of the subject device related to this invention operates at high temperatures and can withstand harsh chemical environments. Embodiments of the device are made on a single substrate. The devices can also be made on individual substrates and monitored individually as if they were part of an array on a single substrate. The device can incorporate sensing electrodes in the same environment, which allows the electrodes to be coplanar and, thus, keep manufacturing costs low. Embodiments of the device can provide improvements to sensitivity, selectivity, and signal interference via surface temperature control.

  10. Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, Florida, May 1994

    USGS Publications Warehouse

    Schiffer, D.M.; O'Reilly, A. M.; Phelps, G.G.; Bradner, L.A.; Halford, K.J.; Spechler, R.M.

    1994-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1994. The map is based on water-level measurements made at approximately 1,000 wells and several springs. Data on the map were contoured using 5-foot contour intervals in most areas. The potentiometric surface of this karstic aquifer generally reflects land surface topography. Potentiometric surface highs often correspond to topographic highs, which are areas of surficial recharge to the Upper Floridan aquifer. Springs within topographic lows along with areas of more diffuse upward leakage are natural zones of discharge. Municipal, agricultural, and industrial withdrawals have lowered the potentiometric surface in some areas. The potentiometric surface ranged from 125 feet above sea level in Polk County to 32 feet below sea level in Nassau County. Water levels in May 1994 generally were 0 to 3 feet lower than those measured in May 1993. Water levels in May 1994 in northeast Florida generally were 0 to 3 feet higher than in September 1993, except in the lower St. Johns River basin, where water levels were 0 to 4 feet lower than in September 1993. In the rest of the mapped area, water levels in May 1994 generally were 0 to 4 feet lower than those measured in September 1993.

  11. Reputation-Based Secure Sensor Localization in Wireless Sensor Networks

    PubMed Central

    He, Jingsha; Xu, Jing; Zhu, Xingye; Zhang, Yuqiang; Zhang, Ting; Fu, Wanqing

    2014-01-01

    Location information of sensor nodes in wireless sensor networks (WSNs) is very important, for it makes information that is collected and reported by the sensor nodes spatially meaningful for applications. Since most current sensor localization schemes rely on location information that is provided by beacon nodes for the regular sensor nodes to locate themselves, the accuracy of localization depends on the accuracy of location information from the beacon nodes. Therefore, the security and reliability of the beacon nodes become critical in the localization of regular sensor nodes. In this paper, we propose a reputation-based security scheme for sensor localization to improve the security and the accuracy of sensor localization in hostile or untrusted environments. In our proposed scheme, the reputation of each beacon node is evaluated based on a reputation evaluation model so that regular sensor nodes can get credible location information from highly reputable beacon nodes to accomplish localization. We also perform a set of simulation experiments to demonstrate the effectiveness of the proposed reputation-based security scheme. And our simulation results show that the proposed security scheme can enhance the security and, hence, improve the accuracy of sensor localization in hostile or untrusted environments. PMID:24982940

  12. Potentiometric map of the Coffee Sand Aquifer in northeastern Mississippi, October and November 1978

    USGS Publications Warehouse

    Wasson, B.E.

    1980-01-01

    This potentiometric map of the Coffee Sand aquifer in northeastern Mississippi is the fourth in a series of maps, prepared by the U.S. Geological Survey in cooperation with the Mississippi Department of Natural Resources, Bureau of Land and Water Resources, delineating the potentiometric surfaces of the major aquifers in Mississippi. In the outcrop areas the potentiometric surface is strongly affected by recharge from precipitation, topography, and drainage of the aquifer by streams. The potentiometric surface slopes generally to the west away from the area of outcrop and is mildly affected by moderate ground-water withdrawals by wells in Tippah and Union County. Historically, water levels in or near the outcrop of the Coffee Sand have shown little or no long-term changes as shown by a hydrograph of one well in Alcorn County. In the downdip part of the aquifer water-level declines of 2 feet per year are common. (USGS)

  13. NOx Sensor Development

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Woo, L Y; Glass, R S

    NO{sub x} compounds, specifically NO and NO{sub 2}, are pollutants and potent greenhouse gases. Compact and inexpensive NO{sub x} sensors are necessary in the next generation of diesel (CIDI) automobiles to meet government emission requirements and enable the more rapid introduction of more efficient, higher fuel economy CIDI vehicles. Because the need for a NO{sub x} sensor is recent and the performance requirements are extremely challenging, most are still in the development phase. Currently, there is only one type of NO{sub x} sensor that is sold commercially, and it seems unlikely to meet more stringent future emission requirements. Automotive exhaustmore » sensor development has focused on solid-state electrochemical technology, which has proven to be robust for in-situ operation in harsh, high-temperature environments (e.g., the oxygen stoichiometric sensor). Solid-state sensors typically rely on yttria-stabilized zirconia (YSZ) as the oxygen-ion conducting electrolyte and then target different types of metal or metal-oxide electrodes to optimize the response. Electrochemical sensors can be operated in different modes, including amperometric (a current is measured) and potentiometric (a voltage is measured), both of which employ direct current (dc) measurements. Amperometric operation is costly due to the electronics necessary to measure the small sensor signal (nanoampere current at ppm NO{sub x} levels), and cannot be easily improved to meet the future technical performance requirements. Potentiometric operation has not demonstrated enough promise in meeting long-term stability requirements, where the voltage signal drift is thought to be due to aging effects associated with electrically driven changes, both morphological and compositional, in the sensor. Our approach involves impedancemetric operation, which uses alternating current (ac) measurements at a specified frequency. The approach is described in detail in previous reports and several

  14. A potentiometric chiral sensor for L-Phenylalanine based on crosslinked polymethylacrylic acid-polycarbazole hybrid molecularly imprinted polymer.

    PubMed

    Chen, Yu; Chen, Lei; Bi, Ruilin; Xu, Lan; Liu, Yan

    2012-11-19

    A novel chiral molecularly imprinted polymer (MIP) sensor for L-Phenylalanine has been developed, which is constructed by electrochemically driven cross-linking a pendant polymer precursor, poly[2-(N-carbazolyl)ethyl methacrylate-co-meth-acrylic acid]s (PCEMMAs). In this MIP sensing material, the recognition sites, the insulating polymethylacrylic acid (PMAA), were covalently bonded to the conducting polycarbazole which could be used as signal transfer interface between recognition layer and electrode. The mole ratio of copolymerizing monomers, 2-(N-carbazolyl) ethyl methacrylate:methylacrylic acid (CE:MAA), and the scanning cycles of electropolymerization were adjusted during the preparation of MIP sensing material. The optimized conditions, CE:MAA=3:2 and 20 scanning cycles, were obtained. And then the properties of MIP films were characterized by atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle. Open circuit potential-time technique was used to estimate the enantioselectivity of the MIP sensor. The results indicate that the promising sensor preferentially responses L-Phenylalanine (L-Phe) over D-Phenylalanine (D-Phe) with a selectivity coefficient K(D)(L)=5.75×10(-4) and the limit of detection (LOD) is 1.37μM, which reveals its good enantioselectivity and sensitivity. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

  15. Potentiometric surface of the Upper Patapsco aquifer in southern Maryland, September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2009. The map is based on water-level measurements in 65 wells. The highest measured water level was 118 feet above sea level near the northern boundary and outcrop area of the aquifer in northern Anne Arundel County. From this area, the potentiometric surface declined to the south toward a well field in the Annapolis-Arnold area, and from all directions toward three additional cones of depression. These cones are located in the Waldorf-La Plata area, Chalk Point, and the Leonardtown-Lexington Park area. The lowest measured groundwater levels were 26 feet below sea level at Annapolis, 108 feet below sea level south of Waldorf, 60 feet below sea level at Chalk Point, and 83 feet below sea level at Leonardtown. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  16. Label-free potentiometric biosensor based on solid-contact for determination of total phenols in honey and propolis.

    PubMed

    Draghi, Patrícia Ferrante; Fernandes, Julio Cesar Bastos

    2017-03-01

    We developed a label-free potentiometric biosensor using tyrosinase extracted from Musa acuminata and immobilized by covalent bond on a surface of a solid-contact transducer. The transducer was manufactured containing two layers. The first layer contained a blend of poly(vinyl) chloride carboxylated (PVC-COOH), graphite and potassium permanganate. On this layer, we deposited a second layer containing just a mixture of poly(vinyl chloride) carboxylated and graphite. On the last layer of the transducer, we immobilized the tyrosinase enzyme by reaction with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride. The solid-contact potentiometric biosensor presented at low detection limit of 7.3×10 -7 M and a linear range to catechol concentration between 9.3×10 -7 M and 8.3×10 -2 M. This biosensor was applied to determine the amount of total phenols in different samples of honey and propolis. The results agreed with the Folin-Ciocalteu method. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Potentiometric surface of the upper Patapsco Aquifer in southern Maryland, September 1994

    USGS Publications Warehouse

    Curtin, Stephen E.; Mack, Frederick K.; Andreasen, David C.

    1995-01-01

    A map showing the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Cretaceous age in southern Maryland during September 1994 was prepared from water levels measured in 43 wells. The potentiometric surface was at least 70 feet above sea level near the northwestern boundary and outcrop area of the aquifer in a topographically high area of Anne Arundel County, and nearly 60 feet above sea level in a similar setting in Prince Georges County. From these high areas, the potentiometric surface declined to the south and southeast toward large well fields in the Annapolis and Waldorf areas and at the Chalk Point powerplant. Ground-water levels reached nearly 30 feet below sea level in the Annapolis area, nearly 110 feet below sea level southwest of Waldorf, and more than 25 feet below sea level at the Chalk Point powerplant.

  18. Comparison of methods for accurate end-point detection of potentiometric titrations

    NASA Astrophysics Data System (ADS)

    Villela, R. L. A.; Borges, P. P.; Vyskočil, L.

    2015-01-01

    Detection of the end point in potentiometric titrations has wide application on experiments that demand very low measurement uncertainties mainly for certifying reference materials. Simulations of experimental coulometric titration data and consequential error analysis of the end-point values were conducted using a programming code. These simulations revealed that the Levenberg-Marquardt method is in general more accurate than the traditional second derivative technique used currently as end-point detection for potentiometric titrations. Performance of the methods will be compared and presented in this paper.

  19. The difference between the potentiometric surfaces of the Upper Patasco Aquifer, September 1990 and September 2003 in southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2005-01-01

    This report presents a map showing the change in the potentiometric surface of the Upper Patapsco aquifer in the Upper Patapsco Formation of Cretaceous age in Southern Maryland for September 1990 and September 2003. The map, based on water level measurements in 32 wells, shows that during the 13-year period, the potentiometric surface changed from an increase of 6 feet at Arnold, which is located just north of Annapolis, to a decline of 25 feet at Waldorf and Lexington Park and 20 feet at LaPlata and the Chalk Point powerplant.

  20. The Difference Between the Potentiometric Surfaces of the Upper Patapsco Aquifer, September 1982 and September 2001 in Southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2002-01-01

    This report presents a map showing the change in the potentiometric surface of the Upper Patapsco aquifer in the Upper Patapsco Formation of Cretaceous age in Southern Maryland for September 1990 and September 2001. The map, based on water level measurements in 35 wells, shows that during the 11-year period, the potentiometric surface ranged from an increase of 3 feet at Arnold, which is located just north of Annapolis, to a decline of 24 feet 5 miles south of LaPlata and 20 feet at both Waldorf and LaPlata.

  1. Calculating Equilibrium Constants in the SnCl2-H2O-NaOH System According to Potentiometric Titration Data

    NASA Astrophysics Data System (ADS)

    Maskaeva, L. N.; Fedorova, E. A.; Yusupov, R. A.; Markov, V. F.

    2018-05-01

    The potentiometric titration of tin chloride SnCl2 is performed in the concentration range of 0.00009-1.1 mol/L with a solution of sodium hydroxide NaOH. According to potentiometric titration data based on modeling equilibria in the SnCl2-H2O-NaOH system, basic equations are generated for the main processes, and instability constants are calculated for the resulting hydroxo complexes and equilibrium constants of low-soluble tin(II) compounds. The data will be of interest for specialists in the field of theory of solutions.

  2. Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 1999

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2001-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 1999. The map is based on water-level measurements in 85 wells. The potentiometric surface was above sea level near the northern boundary and outcrop area of the aquifer in a topographically high area of Anne Arundel County, and was below sea level in the remainder of the study area. The hydraulic gradient was directed southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. Ground-water levels were more than 80 feet below sea level in a 100-square-mile area surrounding the deepest part of the cone of depression. A cone of depression formed in northern Calvert County due to pumpage at Chesapeake Beach and North Beach. The water level has declined to 43 feet below sea level in this area. The lowest measurement was 164 feet below sea level in a well near the center of the cone of depression at Lexington Park.

  3. The difference between the potentiometric surfaces of the Magothy aquifer, September 1975 and September 1999 in southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2001-01-01

    This report presents a map showing the change in the potentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in Southern Maryland for September 1975 and September 1999. The map, based on water level measurements in 61 wells, shows that the potentiometric surface during the 24-year period ranged from zero at the outcrop area, which is in the northernmost part of the study area, to a decline of 76 feet in Waldorf. Waldorf is located near the southwesternmost part of the study area, and approaches the downdip boundary of the aquifer.

  4. The Difference Between the Potentiometric Surfaces of the Magothy Aquifer, September 1975 and September 2001 in Southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2002-01-01

    This report presents a map showing the change in the potentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in Southern Maryland for September 1975 and September 2001. The map, based on water level measurements in 54 wells, shows that during the 26-year period, the potentiometric surface ranged from zero at the outcrop area, which is in the northernmost part of the study area, to a decline of 75 feet at Waldorf. Waldorf is located near the southwesternmost part of the study area, and approaches the downdip boundary of the aquifer.

  5. New approach in the treatment of data from an acid-base potentiometric titrationI. Monocomponent systems of monofunctional acids and bases.

    PubMed

    Maslarska, Vania; Tencheva, Jasmina; Budevsky, Omortag

    2003-01-01

    Based on precise analysis of the acid-base equilibrium, a new approach in the treatment of experimental data from a potentiometric titration is proposed. A new general formula giving explicitly the relation V=f([H(+)]) is derived, valid for every acid-base titration, which includes mono- and polyfunctional protolytes and their mixtures. The present study is the first practical application of this formula for the simplest case, the analysis of one monofunctional protolyte. The collected mV data during the titration are converted into pH-values by means of an auto pH-calibration procedure, thus avoiding preliminary preparation of the measuring system. The mentioned pH-calibration method is applicable also in water-organic mixtures and allows the quantitative determination of sparingly soluble substances (particularly pharmaceuticals). The treatment of the data is performed by means of ready-to-use software products, which makes the proposed approach accessible for a wide range of applications.

  6. Novel choline esterase based sensor for monitoring of organophosphorus pollutants

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wilkins, E.S.; Ghindilis, A.L.; Atanasov, P.

    1996-12-31

    Organophosphorus compounds are significant major environmental pollutants due to their intensive use as pesticides. The modern techniques based on inhibition of choline esterase enzyme activity are discussed. Potentiometric electrodes based on detection of choline esterase inhibition by analytes has been developed. The detection of choline esterase activity is based on the novel principle of molecular transduction. Immobilized peroxidase acting as the molecular transducer, catalyzes the electroreduction of hydrogen peroxide by direct (mediatorless) electron transfer. The sensing element consists of a carbon based electrode containing an assembly of co-immobilized enzymes: choline esterase, choline oxidase and peroxidase.

  7. Bluetooth-based wireless sensor networks

    NASA Astrophysics Data System (ADS)

    You, Ke; Liu, Rui Qiang

    2007-11-01

    In this work a Bluetooth-based wireless sensor network is proposed. In this bluetooth-based wireless sensor networks, information-driven star topology and energy-saved mode are used, through which a blue master node can control more than seven slave node, the energy of each sensor node is reduced and secure management of each sensor node is improved.

  8. Light addressable potentiometric sensor with an array of sensing regions

    NASA Astrophysics Data System (ADS)

    Liang, Weiguo; Han, JingHong; Zhang, Hong; Chen, Deyong

    2001-09-01

    This paper describes the mechanism of light addressable poteniometric sensors (LAPS) from the viewpoints of Semiconductor Physics, and introduces the fabrication of a multi-parameter LAPS chip. The MEMS technology is applied to produce a matrix of sensing regions on the wafer. By doing that, the cross talk among these regions is reduced, and the precision of the LAPS is increased. An IR-LED matrix is used as the light source, and the flow-injection method is used to input samples. The sensor system is compact and highly integrated. The measure and control system is composed of a personal computer, a lock-in amplifier, a potentiostat, a singlechip system, and an addressing circuit. Some experiments have been done with this device. The results show that this device is very promising for practical use.

  9. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, September 2010

    USGS Publications Warehouse

    Ortiz, A.G.

    2011-01-01

    This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when groundwater levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 53.17 inches for west-central Florida (from October 2009 through September 2010) was 0.41 inches above the historical cumulative average of 52.76 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District.

  10. Graphene oxide-DNA based sensors.

    PubMed

    Gao, Li; Lian, Chaoqun; Zhou, Yang; Yan, Lirong; Li, Qin; Zhang, Chunxia; Chen, Liang; Chen, Keping

    2014-10-15

    Since graphene oxide (GO) is readily available and exhibits exceptional optical, electrical, mechanical and chemical properties, it has attracted increasing interests for use in GO-DNA based sensors. This paper reviews the advances in GO-DNA based sensors using DNA as recognition elements. In solution, GO is as an excellent acceptor of fluorescence resonance energy transfer (FRET) to quench the fluorescence in dye labeled DNA sequences. This review discusses the emerging GO-DNA based sensors related to FRET for use in the detection of DNA, proteins, metal ions, cysteine (Cys), and others. The application of the electrochemical GO-DNA based sensors is also summarized because GO possesses exceptional electrochemical properties. The detection mechanisms and the advantages of GO are also revealed and discussed. GO-DNA based sensors perform well at low cost, and high sensitivity, and provide low detection limits. Additionally, GO-DNA based sensors should appear in the near future as scientists explore their usefulness and properties. Finally, future perspectives and possible challenges in this area are outlined. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. The difference between the potentiometric surfaces of the Magothy Aquifer of September 1986 and September 1988 in southern Maryland

    USGS Publications Warehouse

    Mack, Frederick K.; Andreasen, David C.; Curtin, Stephen E.; Wheeler, Judith C.

    1990-01-01

    A map was prepared that shows the net change in the potentiometric surface of the Magothy aquifer (in the Cretaceous Magothy Formation) in southern Maryland from the fall of 1986 to the fall of 1988. The map, based on water level measurements from 79 observation wells, shows that during the 2 year period the potentiometric surface declined less than 5 ft in most of the northern part of the study area and more than 10 ft in a 4-sq-mi area in northern Charles County. Net water-level rises of as much as 2 ft were measured in central Charles County. (USGS)

  12. The Difference Between the Potentiometric Surfaces of the Upper Patapsco Aquifer in Southern Maryland, September 1990 and September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the change in the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland for September 1990 and September 2007. The map, based on water-level measurements in 33 wells, shows that during the 17-year period, the change in the potentiometric surface ranged from zero at the edge of the outcrop area in northern Anne Arundel County to a decline of 28 feet at Crofton Meadows, 38 feet at Arnold, 36 feet at Waldorf, 35 feet at the Chalk Point power plant, and 40 feet at Lexington Park.

  13. Potentiometric surface of the Magothy Aquifer in southern Maryland during the fall of 1987

    USGS Publications Warehouse

    Mack, Frederick K.; Andreasen, David C.; Curtin, Stephen E.; Wheeler, Judith C.

    1989-01-01

    A map showing the potentiometric surface of the Magothy aquifer in the Cretaceous Magothy Formation in southern Maryland during the fall of 1987 was prepared by using water level measurements in 85 observation wells. The potentiometric surface was highest near the northwestern boundary and outcrop area of the aquifer in topographically high locations of Anne Arundel and Prince Georges Counties. The hydraulic gradient in the study area was generally southeastward or toward the centers of three cones of depression which have developed in response to pumping stresses. These cones formed around well fields in the Annapolis, Waldorf, and Chalk Point areas. The potentiometric surface of the Magothy aquifer was more than 40 ft below sea level in parts of the Waldorf and Chalk Point areas. (USGS)

  14. Galvanostatic Entrapment of Penicillinase into Polytyramine Films and its Utilization for the Potentiometric Determination of Penicillin

    PubMed Central

    Ismail, Fatma; Adeloju, Samuel B.

    2010-01-01

    A sensitive and reliable potentiometric biosensor for determination of penicillin has been developed by exploiting the self-limiting growth of the non-conducting polymer, polytyramine. Optimum polytyramine-penicillinase (PTy-PNCnase) films for potentiometric detection of penicillin were accomplished with monomer solutions which contained 0.03 M tyramine, 37 U/mL penicillinase, 0.01 M KNO3, and 3 mM penicillin with an applied current density of 0.8 mA/cm2 and an electropolymerisation time of 40 seconds. The potentiometric biosensor gave a linear concentration range of 3–283 μM for penicillin and achieved a minimum detectable concentration of 0.3 μM. The biosensor was successfully utilized for the detection of Amoxycillin and gave an average percentage recovery of 102 ± 6%. Satisfactory recoveries of penicillin G were also achieved in milk samples with the potentiometric biosensor when concentrations are ≥20 ppm. PMID:22319276

  15. Potentiometric Surface of the Lower Patapsco Aquifer in Southern Maryland, September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the potentiometric surface of the lower Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2007. The map is based on water-level measurements in 65 wells. The highest measured water level was 111 feet above sea level near the northwestern boundary and outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined towards well fields at Severndale and Arnold. The measured ground-water levels were 87 feet below sea level at Severndale, and 42 feet below sea level at Arnold. There was also a cone of depression covering a large area in Charles County that includes Waldorf, La Plata, Indian Head, and the Morgantown power plant. The ground-water levels measured were as low as 219 feet below sea level at Waldorf, 187 feet below sea level at La Plata, 106 feet below sea level at Indian Head, and 89 feet below sea level at the Morgantown power plant.

  16. Potentiometric Surface of the Upper Patapsco Aquifer in Southern Maryland, September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2007. The map is based on water-level measurements in 50 wells. The highest measured water level was 120 feet above sea level near the northern boundary and outcrop area of the aquifer in northern Anne Arundel County. From this area, the potentiometric surface declined to the south toward a well field in the Annapolis-Arnold area, and from all directions toward four cones of depression. These cones are located in the Waldorf-La Plata area, Chalk Point-Prince Frederick area, Swan Point subdivision in southern Charles County, and the Lexington Park-St. Inigoes area. The lowest measured ground-water level was 44 feet below sea level at Arnold, 106 feet below sea level south of Waldorf, 54 feet below sea level at Swan Point, 59 feet below sea level at Chalk Point, and 58 feet below sea level at Lexington Park.

  17. PVC membrane, coated-wire, and carbon-paste ion-selective electrodes for potentiometric determination of galantamine hydrobromide in physiological fluids.

    PubMed

    Abdel-Haleem, Fatehy M; Saad, Mohamed; Barhoum, Ahmed; Bechelany, Mikhael; Rizk, Mahmoud S

    2018-08-01

    We report on highly-sensitive ion-selective electrodes (ISEs) for potentiometric determining of galantamine hydrobromide (GB) in physiological fluids. Galantamine hydrobromide (GB) was selected for this study due to its previous medical importance for treating Alzheimer's disease. Three different types of ISEs were investigated: PVC membrane electrode (PVCE), carbon-paste electrode (CPE), and coated-wire electrode (CWE). In the construction of these electrodes, galantaminium-reineckate (GR) ion-pair was used as a sensing species for GB in solutions. The modified carbon-paste electrode (MCPE) was prepared using graphene oxide (MCPE-GO) and sodium tetrakis (trifluoromethyl) phenyl borate (MCPE-STFPB) as ion-exchanger. The potentiometric modified CPEs (MCPE-GO and MCPE-STFPB) show an improved performance in term of Nernstian slope, selectivity, response time, and response stability compared to the unmodified CPE. The prepared electrodes PVCE, CWE, CPE, MCPE-GO and MCPE-STFPB show Nernstian slopes of 59.9, 59.5, 58.1, 58.3 and 57.0 mV/conc. decade, and detection limits of 5.0 × 10 -6 , 6.3 × 10 -6 , 8.0 × 10 -6 , 6.0 × 10 -6 and 8.0 × 10 -6  mol L -1 , respectively. The prepared ISEs also show high selectivity against cations (i.e. Na + , K + , NH 4 + , Ca 2+ , Al 3+ , Fe 3+ ), amino acids (i.e. glycine, L-alanine alanine), and sugars (i.e. fructose, glucose, maltose, lactose). The prepared ISEs are applicable for determining GB in spiked serums, urines, and pharmaceutical preparations, using a standard addition and a direct potentiometric method. The fast response time (<10 s), long lifetime (1-5 weeks), reversibility and stability of the measured signals facilitate the application of these sensors for routine analysis of the real samples. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Polymeric Optical Sensors for Selective and Sensitive Nitrite Detection Using Cobalt(III) Corrole and Rh(III) Porphyrin as Ionophores

    PubMed Central

    Yang, Si; Wo, Yaqi; Meyerhoff, Mark E.

    2014-01-01

    Cobalt(III) 5, 10, 15-tris(4-tert-butylphenyl) corrole with a triphenylphosphine axial ligand and rhodium(III) 5,10,15,20-tetra(p-tert-butylphenyl)porphyrin are incorporated into plasticized poly(vinyl chloride) films to fabricate nitrite-selective bulk optodes via absorbance measurements. The resulting films yield sensitive, fast and fully reversible response toward nitrite with significantly enhanced nitrite selectivity over other anions including lipophilic anions such as thiocyanate and perchlorate. The selectivity patterns differ greatly from the Hofmeister series based on anion lipophilicity and are consistent with selectivity obtained with potentiometric sensors based on the same ionophores. The optical nitrite sensors are shown to be useful for detecting rates of emission of nitric oxide (NO) from NO releasing polymers containing S-nitroso-N-acetyl-penicillamine. PMID:25150700

  19. Extraction or adsorption? Voltammetric assessment of protamine transfer at ionophore-based polymeric membranes.

    PubMed

    Garada, Mohammed B; Kabagambe, Benjamin; Amemiya, Shigeru

    2015-01-01

    Cation-exchange extraction of polypeptide protamine from water into an ionophore-based polymeric membrane has been hypothesized as the origin of a potentiometric sensor response to this important heparin antidote. Here, we apply ion-transfer voltammetry not only to confirm protamine extraction into ionophore-doped polymeric membranes but also to reveal protamine adsorption at the membrane/water interface. Protamine adsorption is thermodynamically more favorable than protamine extraction as shown by cyclic voltammetry at plasticized poly(vinyl chloride) membranes containing dinonylnaphthalenesulfonate as a protamine-selective ionophore. Reversible adsorption of protamine at low concentrations down to 0.038 μg/mL is demonstrated by stripping voltammetry. Adsorptive preconcentration of protamine at the membrane/water interface is quantitatively modeled by using the Frumkin adsorption isotherm. We apply this model to ensure that stripping voltammograms are based on desorption of all protamine molecules that are transferred across the interface during a preconcentration step. In comparison to adsorption, voltammetric extraction of protamine requires ∼0.2 V more negative potentials, where a potentiometric super-Nernstian response to protamine is also observed. This agreement confirms that the potentiometric protamine response is based on protamine extraction. The voltammetrically reversible protamine extraction results in an apparently irreversible potentiometric response to protamine because back-extraction of protamine from the membrane extremely slows down at the mixed potential based on cation-exchange extraction of protamine. Significantly, this study demonstrates the advantages of ion-transfer voltammetry over potentiometry to quantitatively and mechanistically assess protamine transfer at ionophore-based polymeric membranes as foundation for reversible, selective, and sensitive detection of protamine.

  20. Titanium (III) cation selective electrode based on synthesized tris(2pyridyl) methylamine ionophore and its application in water samples

    NASA Astrophysics Data System (ADS)

    Rezayi, Majid; Karazhian, Reza; Abdollahi, Yadollah; Narimani, Leila; Sany, Seyedeh Belin Tavakoly; Ahmadzadeh, Saeid; Alias, Yatimah

    2014-04-01

    The introduction of low detection limit ion selective electrodes (ISEs) may well pave the way for the determination of trace targets of cationic compounds. This research focuses on the detection of titanium (III) cation using a new PVC-membrane sensor based on synthesized tris(2pyridyl) methylamine (tpm) ionophore. The application and validation of the proposed sensor was done using potentiometric titration, inductively coupled plasma atomic emission spectrometry (ICP-AES), and atomic absorption spectrometry (AAS). The membrane sensor exhibited a Nernstian response to the titanium (III) cation over a concentration range of 1.0 × 10-6-1.0 × 10-2 M and pH range from 1-2.5. The Nernstian slope, the lower of detection (LOD), and the response time (t95%) of the proposed sensor were 29.17 +/- 0.24 mV/dec, 7.9 × 10-7 M, and 20 s, respectively. The direct determination of 4-39 μg/ml of titanium (III) standard solution showed an average recovery of 94.60 and a mean relative standard deviation of 1.8 at 100.0 μg/ml. Finally, the utilization of the electrodes as end-point indicators for potentiometric titration with EDTA solutions for titanium (III) sensor was successfully carried out.

  1. Secured network sensor-based defense system

    NASA Astrophysics Data System (ADS)

    Wei, Sixiao; Shen, Dan; Ge, Linqiang; Yu, Wei; Blasch, Erik P.; Pham, Khanh D.; Chen, Genshe

    2015-05-01

    Network sensor-based defense (NSD) systems have been widely used to defend against cyber threats. Nonetheless, if the adversary finds ways to identify the location of monitor sensors, the effectiveness of NSD systems can be reduced. In this paper, we propose both temporal and spatial perturbation based defense mechanisms to secure NSD systems and make the monitor sensor invisible to the adversary. The temporal-perturbation based defense manipulates the timing information of published data so that the probability of successfully recognizing monitor sensors can be reduced. The spatial-perturbation based defense dynamically redeploys monitor sensors in the network so that the adversary cannot obtain the complete information to recognize all of the monitor sensors. We carried out experiments using real-world traffic traces to evaluate the effectiveness of our proposed defense mechanisms. Our data shows that our proposed defense mechanisms can reduce the attack accuracy of recognizing detection sensors.

  2. Polymethacrylate Polymers with Appended Aluminum(III)-Tetraphenylporphyrins: Synthesis, Characterization and Evaluation as Macromolecular Ionophores for Electrochemical and Optical Fluoride Sensors

    PubMed Central

    Wang, Lin; Meyerhoff, Mark E.

    2008-01-01

    The synthesis and characterization of a novel polymethacylate polymer with covalently linked Al(III)-tetraphenylporphyrin (Al(III)-TPP) groups is reported. The new polymer is examined as a potential macromolecular ionophore for the preparation of polymeric membrane-based potentiometric and optical fluoride selective sensors. To prepare the polymer, an Al(III) porphyrin monomer modified with a methacrylate functionality is synthesized, allowing insertion into a polymethacrylate block copolymer (methyl methacrylate and decyl methacrylate) backbone. The resulting polymer can then be incorporated, along with appropriate additives, into conventional plasticized poly(vinyl chloride) films for testing electrochemical and optical fluoride response properties. The covalent attachment of the Al(III)-TPP ionophore to the copolymer matrix provides potentiometric sensors that exhibit significant selectivity for fluoride ion with extended lifetimes (compared to ion-selective membrane electrodes formulated with conventional free Al(III)-TPP structure). However, quite surprisingly, the attachment of the ionophore to the polymer does not eliminate the interaction of Al(III)-TPP structures to form dimeric species within the membrane phase in the presence of fluoride ion. Such interactions are confirmed by UV/visible spectroscopy of the blended polymeric films. Use of the new polymer-Al(III)-TPP conjugates to prepare optical fluoride sensors by co-incorporating a lipophilic pH indicator (4’,5’-dibromofluorescein octadecyl ester; ETH7075) is also examined and the resulting optical sensing films are shown to exhibit excellent selectivity for fluoride, with the potential for prolonged operational lifetime. PMID:18298973

  3. The Difference Between the Potentiometric Surfaces of the Magothy Aquifer in Southern Maryland, September 1975 and September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the change in the potentiometric surface of the Magothy aquifer in the Magothy Formation of Late Cretaceous age in Southern Maryland between September 1975 and September 2009. The map, based on water level differences obtained from 48 wells, shows that during the 34-year period, the potentiometric surface had little change at the outcrop area, which is in the northernmost part of the study area, but declined 75 feet at Waldorf. Waldorf is located near the southwesternmost part of the study area, and approaches the downdip boundary of the aquifer. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  4. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2009

    USGS Publications Warehouse

    Ortiz, Anita G.

    2009-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2009. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 48.53 inches for west-central Florida (from June 2008 through May 2009) was 4.12 inches below the historical cumulative average of 52.65 inches (Southwest Florida Water Management District, 2009). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  5. Samarium (III) Selective Membrane Sensor Based on Tin (IV) Boratophosphate

    PubMed Central

    Mittal, Susheel K.; Sharma, Harish Kumar; Kumar, Ashok S. K.

    2004-01-01

    A number of Sm (III) selective membranes of varying compositions using tin (IV) boratophosphate as electroactive material were prepared. Polyvinyl chloride, polystyrene and epoxy resin were used as binding materials. Membrane having composition of 40% exchanger and 60% epoxy resin exhibited best performance. This membrane worked well over a wide concentration range of 1×10-5M to 1×10-1 M of samarium ions with a Super-Nernstian slope of 40 mV/decade. It has a fast response time of less than 10 seconds and can be used for at least six months without any considerable divergence in potentials. The proposed sensor revealed good selectivities with respect to alkali, alkaline earth, some transition and rare earth metal ions and can be used in the pH range of 4.0-10.0. It was used as an indicator electrode in the potentiometric titration of Sm (III) ions against EDTA. Effect of internal solution was studied and the electrode was successfully used in non-aqueous media, too.

  6. Metamaterial Absorber Based Multifunctional Sensor Application

    NASA Astrophysics Data System (ADS)

    Ozer, Z.; Mamedov, A. M.; Ozbay, E.

    2017-02-01

    In this study metamaterial based (MA) absorber sensor, integrated with an X-band waveguide, is numerically and experimentally suggested for important application including pressure, density sensing and marble type detecting applications based on rectangular split ring resonator, sensor layer and absorber layer that measures of changing in the dielectric constant and/or the thickness of a sensor layer. Changing of physical, chemical or biological parameters in the sensor layer can be detected by measuring the resonant frequency shifting of metamaterial absorber based sensor. Suggested MA based absorber sensor can be used for medical, biological, agricultural and chemical detecting applications in microwave frequency band. We compare the simulation and experimentally obtained results from the fabricated sample which are good agreement. Simulation results show that the proposed structure can detect the changing of the refractive indexes of different materials via special resonance frequencies, thus it could be said that the MA-based sensors have high sensitivity. Additionally due to the simple and tiny structures it could be adapted to other electronic devices in different sizes.

  7. Map showing the potentiometric surface of the Magothy Aquifer in southern Maryland, September 1981

    USGS Publications Warehouse

    Mack, F.K.; Wheeler, J.C.; Curtin, S.E.

    1982-01-01

    The map is based on measurements from a network of 83 observation wells cased to the Magothy aquifer. Highest levels of the potentiometric surface, 59 to 60 feet above sea level, were measured near the outcrop-subcrop of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties. The surface slopes to the southeast to above sea level along much of the western shore of Chesapeake Bay. Three separate, distinct, and extensive cones of depression have developed in the potentiometric surface around the well fields of the city of Annapolis-Broadneck Peninsula area, town of Waldorf, and Chalk Point. Several square miles of each cone are below sea level, and, in some areas at Chalk Point and Waldorf, the cone is 40 to 50 feet below sea level. The network of wells was developed as part of the cooperative program between the U.S. Geological Survey, the Maryland Geological Survey, and the Maryland Energy and Coastal Zone Administration. (USGS)

  8. Map showing the potentiometric surface of the Magothy Aquifer in southern Maryland, August 1980

    USGS Publications Warehouse

    Mack, Frederick K.; Wheeler, Judith C.; Curtin, Stephen E.

    1981-01-01

    This map is based on measurements made in a network of 77 observation wells. Highest levels of the potentiometric surface, 61 to 64 feet above sea level, were near the outcrop or subcrop of the aquifer in topographically high areas of Anne Arundel and northern Prince Georges Counties. The potentiometric surface slopes toward centers of pumpage near Annapolis, in northern Charles County, and southern Prince Georges County. Two separate , distinct, and extensive cones of depression have developed in the surface around the well fields of Waldorf, in northern Charles County, and the Chalk Point power plant, in southern Prince Georges County. The cone of depression in the Annapolis area has coalesced with a more shallow cone that includes the Broadneck Peninsula. The network of wells was developed and is operated and maintained as part of the cooperative program between the U.S. Geological Survey and agencies of the Maryland Department of Natural Resources. (USGS)

  9. Detection principles of biological and chemical FET sensors.

    PubMed

    Kaisti, Matti

    2017-12-15

    The seminal importance of detecting ions and molecules for point-of-care tests has driven the search for more sensitive, specific, and robust sensors. Electronic detection holds promise for future miniaturized in-situ applications and can be integrated into existing electronic manufacturing processes and technology. The resulting small devices will be inherently well suited for multiplexed and parallel detection. In this review, different field-effect transistor (FET) structures and detection principles are discussed, including label-free and indirect detection mechanisms. The fundamental detection principle governing every potentiometric sensor is introduced, and different state-of-the-art FET sensor structures are reviewed. This is followed by an analysis of electrolyte interfaces and their influence on sensor operation. Finally, the fundamentals of different detection mechanisms are reviewed and some detection schemes are discussed. In the conclusion, current commercial efforts are briefly considered. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

  10. Novel miniaturized sensors for potentiometric batch and flow-injection analysis (FIA) of perchlorate in fireworks and propellants.

    PubMed

    Almeer, Saeed H M A; Zogby, Ibrahim A; Hassan, Saad S M

    2014-11-01

    Three planar miniaturized perchlorate membrane sensors (3×5 mm(2)) are prepared using a flexible Kaptan substrate coated with nitron-perchlorate (NT-ClO4) [sensor 1], methylene blue-perchlorate (MB-ClO4) [sensor II] and indium-porphyrin (In-Por) [sensor III] as electroactive materials in PVC membranes plasticized with 2-NPPE. Sensors I, II and III display near-Nernstian response for 1.0×10(-5)-1.0×10(-2), 3.1×10(-5)-1.0×10(-2) and 3.1×10(-6)-1.0×10(-2) mol L(-1) ClO4(-) with lower detection limits of 6.1×10(-6), 6.9×10(-6) and 1.2×10(-6) mol L(-1), and anionic calibration slopes of 50.9±0.4, 48.4±0.4 and 57.7±0.3 mV decade(-1), respectively. Methods for determining perchlorate using these sensors offer many attractive advantages including simplicity, flexibility, cost effectiveness, wide linear dynamic response range (0.1-1000 ppm), low detection limit (<1.2×10(-6) mol L(-1)≡0.1 ppm), small sample test volume (100 μL), safety, short response time (<20 s), long life span (~8 weeks), and extended wide working pH range (4.5-8.0). The sensors show high selectivity in the presence of some inorganic ions (e.g., PO4(3-), SO4(2-), S2O3(2-), NO2(-), NO3(-), N3(-), CN(-), Cl(-), Br(-), I(-)) and automation feasibility. Indium-porphyrin based membrane sensor (sensor III) is used as a detector in a wall-jet flow injection set-up to enable accurate flow injection analysis (FIA) of perchlorate in some fireworks without interferences from the associated reducing agents (sulfur and charcoal), binders (dextrin, lactose), coloring agents (calcium, strontium, copper, iron, sodium), color brighten (linseed oil) and regulators (aluminum flakes) which are commonly used in the formulations. The sensor is also used for perchlorate assessment in some propellant powders. The results fairly agree with data obtained by ion-chromatography. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Nanoparticles based fiber optic SPR sensor

    NASA Astrophysics Data System (ADS)

    Shah, Kruti; Sharma, Navneet K.

    2018-05-01

    Localized surface plasmon resonance based fiber optic sensor using platinum nanoparticles is proposed and theoretically analyzed. Increase in thickness of nanoparticles layer increases the sensitivity of sensor. 50 nm thick platinum nanoparticles layer based sensor reveals highest sensitivity.

  12. Potentiometric sensing of nuclease activities and oxidative damage of single-stranded DNA using a polycation-sensitive membrane electrode.

    PubMed

    Ding, Jiawang; Qin, Wei

    2013-09-15

    A simple, general and label-free potentiometric method to measure nuclease activities and oxidative DNA damage in a homogeneous solution using a polycation-sensitive membrane electrode is reported. Protamine, a linear polyionic species, is used as an indicator to report the cleavage of DNA by nucleases such as restriction and nonspecific nucleases, and the damage of DNA induced by hydroxyl radicals. Measurements can be done with a titration mode or a direct detection mode. For the potentiometric titration mode, the enzymatic cleavage dramatically affects the electrostatical interaction between DNA and protamine and thus shifts the response curve for the potentiometric titration of the DNA with protamine. Under the optimized conditions, the enzyme activities can be sensed potentiometrically with detection limits of 2.7×10(-4)U/µL for S1 nuclease, and of 3.9×10(-4)U/µL for DNase I. For the direct detection mode, a biocomplex between protamine and DNA is used as a substrate. The nuclease of interest cleaves the DNA from the protamine/DNA complex into smaller fragments, so that free protamine is generated and can be detected potentiometrically via the polycation-sensitive membrane electrode. Using a direct measurement, the nuclease activities could be rapidly detected with detection limits of 3.2×10(-4)U/µL for S1 nuclease, and of 4.5×10(-4)U/µL for DNase I. Moreover, the proposed potentiometric assays demonstrate the potential applications in the detection of hydroxyl radicals. It is anticipated that the present potentiometric strategy will provide a promising platform for high-throughput screening of nucleases, reactive oxygen species and the drugs with potential inhibition abilities. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. CMOS image sensor-based implantable glucose sensor using glucose-responsive fluorescent hydrogel.

    PubMed

    Tokuda, Takashi; Takahashi, Masayuki; Uejima, Kazuhiro; Masuda, Keita; Kawamura, Toshikazu; Ohta, Yasumi; Motoyama, Mayumi; Noda, Toshihiko; Sasagawa, Kiyotaka; Okitsu, Teru; Takeuchi, Shoji; Ohta, Jun

    2014-11-01

    A CMOS image sensor-based implantable glucose sensor based on an optical-sensing scheme is proposed and experimentally verified. A glucose-responsive fluorescent hydrogel is used as the mediator in the measurement scheme. The wired implantable glucose sensor was realized by integrating a CMOS image sensor, hydrogel, UV light emitting diodes, and an optical filter on a flexible polyimide substrate. Feasibility of the glucose sensor was verified by both in vitro and in vivo experiments.

  14. Potentiometric Surface of the Lower Patapsco Aquifer in Southern Maryland, September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasin, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the potentiometric surface of the lower Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland during September 2009. The map is based on water-level measurements in 64 wells. The highest measured water level was 110 feet above sea level near the northwestern boundary and outcrop area of the aquifer in northern Prince George's County. From this area, the potentiometric surface declined towards well fields at Severndale, Broad Creek, and Arnold. The measured groundwater levels were 99 feet below sea level at Severndale, 50 feet below sea level at Broad Creek, and 36 feet below sea level at Arnold. There was also a cone of depression in Charles County that includes Waldorf, La Plata, Indian Head, and the Morgantown power plant. The groundwater levels measured were as low as 215 feet below sea level at Waldorf, 149 feet below sea level at La Plata, 121 feet below sea level at Indian Head, and 96 feet below sea level at the Morgantown power plant. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  15. Potentiometric map of the Gordo Aquifer in northeastern Mississippi, September, October, and November 1978

    USGS Publications Warehouse

    Wasson, B.E.

    1979-01-01

    This potentiometric map of the Gordo aquifer in northeastern Mississippi is the second in a series of maps, prepared by the U.S. Geological Survey in cooperation with the Mississippi Department of Natural Resources, Bureau of Land and Water Resources, delineating the potentiometric surfaces of the major aquifers in Mississippi. The potentiometric surface of the Gordo aquifer slopes generally to the west away from the outcrop area and it is depressed generally by large ground-water withdrawals in the Tupelo and Columbus areas. Historically, water levels in or near the outcrop of the Gordo aquifer have shown little or no long-term changes. Heavy withdrawals from the downdip area have caused long-term water-level declines of 1 to 2 feet per year in much of the confined part of the aquifer. Water-level decline in one observation well in Tupelo has averaged about 5 feet per year since 1966. (USGS)

  16. Recent Advances in Paper-Based Sensors

    PubMed Central

    Liana, Devi D.; Raguse, Burkhard; Gooding, J. Justin; Chow, Edith

    2012-01-01

    Paper-based sensors are a new alternative technology for fabricating simple, low-cost, portable and disposable analytical devices for many application areas including clinical diagnosis, food quality control and environmental monitoring. The unique properties of paper which allow passive liquid transport and compatibility with chemicals/biochemicals are the main advantages of using paper as a sensing platform. Depending on the main goal to be achieved in paper-based sensors, the fabrication methods and the analysis techniques can be tuned to fulfill the needs of the end-user. Current paper-based sensors are focused on microfluidic delivery of solution to the detection site whereas more advanced designs involve complex 3-D geometries based on the same microfluidic principles. Although paper-based sensors are very promising, they still suffer from certain limitations such as accuracy and sensitivity. However, it is anticipated that in the future, with advances in fabrication and analytical techniques, that there will be more new and innovative developments in paper-based sensors. These sensors could better meet the current objectives of a viable low-cost and portable device in addition to offering high sensitivity and selectivity, and multiple analyte discrimination. This paper is a review of recent advances in paper-based sensors and covers the following topics: existing fabrication techniques, analytical methods and application areas. Finally, the present challenges and future outlooks are discussed. PMID:23112667

  17. The difference between the potentiometric surfaces of the lower Patapsco aquifer in southern Maryland, September 1990 and September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the change in the potentiometric surface of the lower Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland for September 1990 and September 2007. The map, based on water-level measurements in 45 wells, shows that the change of the potentiometric surface during the 17-year period ranged from increases of 19 feet at Indian Head and 6 feet near the outcrop area in Glen Burnie, to declines of 41 feet at Arnold, 45 feet at Severndale, 68 feet at Crofton Meadows, 77 feet at Waldorf, 76 feet at La Plata, 28 feet at the Morgantown power plant, and 35 feet at the Swan Point subdivision south of Morgantown.

  18. Carbon Nanotube-Based Chemiresistive Sensors

    PubMed Central

    Tang, Ruixian; Shi, Yongji; Hou, Zhongyu; Wei, Liangming

    2017-01-01

    The development of simple and low-cost chemical sensors is critically important for improving human life. Many types of chemical sensors have been developed. Among them, the chemiresistive sensors receive particular attention because of their simple structure, the ease of high precise measurement and the low cost. This review mainly focuses on carbon nanotube (CNT)-based chemiresistive sensors. We first describe the properties of CNTs and the structure of CNT chemiresistive sensors. Next, the sensing mechanism and the performance parameters of the sensors are discussed. Then, we detail the status of the CNT chemiresistive sensors for detection of different analytes. Lastly, we put forward the remaining challenges for CNT chemiresistive sensors and outlook the possible opportunity for CNT chemiresistive sensors in the future. PMID:28420195

  19. Carbon Nanotube-Based Chemiresistive Sensors.

    PubMed

    Tang, Ruixian; Shi, Yongji; Hou, Zhongyu; Wei, Liangming

    2017-04-18

    The development of simple and low-cost chemical sensors is critically important for improving human life. Many types of chemical sensors have been developed. Among them, the chemiresistive sensors receive particular attention because of their simple structure, the ease of high precise measurement and the low cost. This review mainly focuses on carbon nanotube (CNT)-based chemiresistive sensors. We first describe the properties of CNTs and the structure of CNT chemiresistive sensors. Next, the sensing mechanism and the performance parameters of the sensors are discussed. Then, we detail the status of the CNT chemiresistive sensors for detection of different analytes. Lastly, we put forward the remaining challenges for CNT chemiresistive sensors and outlook the possible opportunity for CNT chemiresistive sensors in the future.

  20. Passive Sensor Materials Based on Liquid Crystals

    DTIC Science & Technology

    2011-03-12

    REPORT Passive Sensor Materials based on Liquid Crystals 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Research supported by this grant entitled “Passive...Sensor Materials Based on Liquid Crystals” revolved around an investigation of liquid crystalline materials for use in passive sensors for chemical... based on Liquid Crystals Report Title ABSTRACT Research supported by this grant entitled “Passive Sensor Materials Based on Liquid Crystals” revolved

  1. Potentiometric measurement of polymer-membrane electrodes based on lanthanum

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saefurohman, Asep, E-mail: saefurohman.asep78@Gmail.com; Buchari,, E-mail: saefurohman.asep78@Gmail.com; Noviandri, Indra, E-mail: saefurohman.asep78@Gmail.com

    2014-03-24

    Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no reportmore » previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm{sup −1}, 1031 cm{sup −1} and 794.7 cm{sup −1} for P=O stretching and stretching POC from group −OP =O. The result showed shift wave number for P =O stretching of the cluster (−OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm{sup −1} indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R{sub 3}P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10{sup −3} M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10{sup −5} and 10{sup −1} M.« less

  2. CMOS image sensor-based implantable glucose sensor using glucose-responsive fluorescent hydrogel

    PubMed Central

    Tokuda, Takashi; Takahashi, Masayuki; Uejima, Kazuhiro; Masuda, Keita; Kawamura, Toshikazu; Ohta, Yasumi; Motoyama, Mayumi; Noda, Toshihiko; Sasagawa, Kiyotaka; Okitsu, Teru; Takeuchi, Shoji; Ohta, Jun

    2014-01-01

    A CMOS image sensor-based implantable glucose sensor based on an optical-sensing scheme is proposed and experimentally verified. A glucose-responsive fluorescent hydrogel is used as the mediator in the measurement scheme. The wired implantable glucose sensor was realized by integrating a CMOS image sensor, hydrogel, UV light emitting diodes, and an optical filter on a flexible polyimide substrate. Feasibility of the glucose sensor was verified by both in vitro and in vivo experiments. PMID:25426316

  3. Titanium (III) cation selective electrode based on synthesized tris(2pyridyl) methylamine ionophore and its application in water samples

    PubMed Central

    Rezayi, Majid; Karazhian, Reza; Abdollahi, Yadollah; Narimani, Leila; Sany, Seyedeh Belin Tavakoly; Ahmadzadeh, Saeid; Alias, Yatimah

    2014-01-01

    The introduction of low detection limit ion selective electrodes (ISEs) may well pave the way for the determination of trace targets of cationic compounds. This research focuses on the detection of titanium (III) cation using a new PVC-membrane sensor based on synthesized tris(2pyridyl) methylamine (tpm) ionophore. The application and validation of the proposed sensor was done using potentiometric titration, inductively coupled plasma atomic emission spectrometry (ICP-AES), and atomic absorption spectrometry (AAS). The membrane sensor exhibited a Nernstian response to the titanium (III) cation over a concentration range of 1.0 × 10−6–1.0 × 10−2 M and pH range from 1–2.5. The Nernstian slope, the lower of detection (LOD), and the response time (t95%) of the proposed sensor were 29.17 ± 0.24 mV/dec, 7.9 × 10−7 M, and 20 s, respectively. The direct determination of 4–39 μg/ml of titanium (III) standard solution showed an average recovery of 94.60 and a mean relative standard deviation of 1.8 at 100.0 μg/ml. Finally, the utilization of the electrodes as end-point indicators for potentiometric titration with EDTA solutions for titanium (III) sensor was successfully carried out. PMID:24722576

  4. Model-Based Method for Sensor Validation

    NASA Technical Reports Server (NTRS)

    Vatan, Farrokh

    2012-01-01

    Fault detection, diagnosis, and prognosis are essential tasks in the operation of autonomous spacecraft, instruments, and in situ platforms. One of NASA s key mission requirements is robust state estimation. Sensing, using a wide range of sensors and sensor fusion approaches, plays a central role in robust state estimation, and there is a need to diagnose sensor failure as well as component failure. Sensor validation can be considered to be part of the larger effort of improving reliability and safety. The standard methods for solving the sensor validation problem are based on probabilistic analysis of the system, from which the method based on Bayesian networks is most popular. Therefore, these methods can only predict the most probable faulty sensors, which are subject to the initial probabilities defined for the failures. The method developed in this work is based on a model-based approach and provides the faulty sensors (if any), which can be logically inferred from the model of the system and the sensor readings (observations). The method is also more suitable for the systems when it is hard, or even impossible, to find the probability functions of the system. The method starts by a new mathematical description of the problem and develops a very efficient and systematic algorithm for its solution. The method builds on the concepts of analytical redundant relations (ARRs).

  5. Potentiometric map of the Eutaw-McShan Aquifer in northeastern Mississippi, September, October, and November 1978

    USGS Publications Warehouse

    Wasson, B.E.

    1980-01-01

    This potentiometric map of the Eutaw-McShan aquifer in northeastern Mississippi is the third in a series of maps, prepared by the U.S. Geological Survey in cooperation with the Mississippi Department of Natural Resources, Bureau of Land and Water Resources, delineating the potentiometric surfaces of the major aquifers in Mississippi. From its outcrop area the Eutaw-McShan aquifer dips about 30 feet per mile to the west and southwest. Thickness of the aquifer commonly is between 200 and 300 feet in most of the area, and commonly about one-half this thickness consists of sand. In the outcrop area the potentiometric surface is strongly affected by recharge from precipitation, topography, and drainage of the aquifer by streams. The potentiometric surface of the aquifer slopes generally to the west away from the area of outcrop and it is strongly affected by large ground-water withdrawals at or near Tupelo, Aberdeen, and West Point. Historically, water levels in or near the outcrop of the Eutaw-McShan aquifer have shown little or no long-term changes. Withdrawals of water by wells from the downdip area have caused long-term water-level declines of 1 to 2 feet per year in much of the confined part of the aquifer. Water-level declines during recent years in several observation wells in Lee County ranged from 2 to 9 feet per year. One hydrograph in Clay County that is near the center of the depression in the potentiometric surface at West Point shows about 5 feet per year of water-level decline since 1972. (USGS)

  6. The difference between the potentiometric surfaces of the Upper Patapsco aquifer in southern Maryland, September 1990 and September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the change in the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Early Cretaceous age in Southern Maryland between September 1990 and September 2009. The map, based on water level differences obtained from 33 wells, shows that during the 19-year period, the change in the potentiometric surface ranged from zero at the edge of the outcrop area in northern Anne Arundel County to a decline of 20 feet at Broad Creek, 16 feet near Arnold, 32 feet at Waldorf, 37 feet at the Chalk Point power plant, and 43 feet at Lexington Park. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  7. Sensitivity Enhancement of FBG-Based Strain Sensor.

    PubMed

    Li, Ruiya; Chen, Yiyang; Tan, Yuegang; Zhou, Zude; Li, Tianliang; Mao, Jian

    2018-05-17

    A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments.

  8. Sensitivity Enhancement of FBG-Based Strain Sensor

    PubMed Central

    Chen, Yiyang; Tan, Yuegang; Zhou, Zude; Mao, Jian

    2018-01-01

    A novel fiber Bragg grating (FBG)-based strain sensor with a high-sensitivity is presented in this paper. The proposed FBG-based strain sensor enhances sensitivity by pasting the FBG on a substrate with a lever structure. This typical mechanical configuration mechanically amplifies the strain of the FBG to enhance overall sensitivity. As this mechanical configuration has a high stiffness, the proposed sensor can achieve a high resonant frequency and a wide dynamic working range. The sensing principle is presented, and the corresponding theoretical model is derived and validated. Experimental results demonstrate that the developed FBG-based strain sensor achieves an enhanced strain sensitivity of 6.2 pm/με, which is consistent with the theoretical analysis result. The strain sensitivity of the developed sensor is 5.2 times of the strain sensitivity of a bare fiber Bragg grating strain sensor. The dynamic characteristics of this sensor are investigated through the finite element method (FEM) and experimental tests. The developed sensor exhibits an excellent strain-sensitivity-enhancing property in a wide frequency range. The proposed high-sensitivity FBG-based strain sensor can be used for small-amplitude micro-strain measurement in harsh industrial environments. PMID:29772826

  9. Electrochemical l-Lactic Acid Sensor Based on Immobilized ZnO Nanorods with Lactate Oxidase

    PubMed Central

    Ibupoto, Zafar Hussain; Ali Shah, Syed Muhammad Usman; Khun, Kimleang; Willander, Magnus

    2012-01-01

    In this work, fabrication of gold coated glass substrate, growth of ZnO nanorods and potentiometric response of lactic acid are explained. The biosensor was developed by immobilizing the lactate oxidase on the ZnO nanorods in combination with glutaraldehyde as a cross linker for lactate oxidase enzyme. The potentiometric technique was applied for the measuring the output (EMF) response of l-lactic acid biosensor. We noticed that the present biosensor has wide linear detection range of concentration from 1 × 10−4–1 × 100 mM with acceptable sensitivity about 41.33 ± 1.58 mV/decade. In addition, the proposed biosensor showed fast response time less than 10 s, a good selectivity towards l-lactic acid in presence of common interfering substances such as ascorbic acid, urea, glucose, galactose, magnesium ions and calcium ions. The present biosensor based on immobilized ZnO nanorods with lactate oxidase sustained its stability for more than three weeks. PMID:22736960

  10. Electrochemical L-lactic acid sensor based on immobilized ZnO nanorods with lactate oxidase.

    PubMed

    Ibupoto, Zafar Hussain; Shah, Syed Muhammad Usman Ali; Khun, Kimleang; Willander, Magnus

    2012-01-01

    In this work, fabrication of gold coated glass substrate, growth of ZnO nanorods and potentiometric response of lactic acid are explained. The biosensor was developed by immobilizing the lactate oxidase on the ZnO nanorods in combination with glutaraldehyde as a cross linker for lactate oxidase enzyme. The potentiometric technique was applied for the measuring the output (EMF) response of l-lactic acid biosensor. We noticed that the present biosensor has wide linear detection range of concentration from 1 × 10(-4)-1 × 10(0) mM with acceptable sensitivity about 41.33 ± 1.58 mV/decade. In addition, the proposed biosensor showed fast response time less than 10 s, a good selectivity towards l-lactic acid in presence of common interfering substances such as ascorbic acid, urea, glucose, galactose, magnesium ions and calcium ions. The present biosensor based on immobilized ZnO nanorods with lactate oxidase sustained its stability for more than three weeks.

  11. Potentiometric surface of the lower Cape Fear Aquifer in the central coastal plain of North Carolina, December 1986

    USGS Publications Warehouse

    Winner, M.D.; Lyke, William L.; Brockman, Allen R.

    1989-01-01

    Water level measurements were made in four wells open to the lower Cape Fear aquifer at the end of 1986 to determine the configuration of its potentiometric surface over an area of approximately 4,100 sq mi. Because of the scarcity of data, five earlier measurements were also used to help estimate the position of the potentiometric contours. These were one-time measurements in temporary observation wells. A broad cone of depression has formed in the area between Kinston and New Bern where the potentiometric surface is below sea level and seems likely related to large groundwater withdrawals from the aquifers overlying the lower Cape Fear in that area.

  12. Determination of the titratable acidity and the pH of wine based on potentiometric flow injection analysis.

    PubMed

    Vahl, Katja; Kahlert, Heike; von Mühlen, Lisandro; Albrecht, Anja; Meyer, Gabriele; Behnert, Jürgen

    2013-07-15

    A FIA system using a pH-sensitive detector based on a graphite/quinhydrone/silicone composite electrode was applied to determine sequentially the titratable acidity and the pH of wine, as well as the sum of calcium and magnesium ions. For all measurements the same FIA configuration was used employing different carrier solutions. The results for the determination of acidity and pH are in good agreement with those obtained by classical potentiometric titrations and by pH measurements using a conventional glass electrode. The standard deviation was less than 1.5% for both kinds of measurements and the sample volume was 150 μL. The method allows about 40 determinations of titratable acidity per hour and 30 pH measurements per hour. The titration method can be adjusted to the legal requirements in USA and Europe. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. A Large Area Tactile Sensor Patch Based on Commercial Force Sensors

    PubMed Central

    Vidal-Verdú, Fernando; Barquero, Maria Jose; Castellanos-Ramos, Julián; Navas-González, Rafael; Sánchez, Jose Antonio; Serón, Javier; García-Cerezo, Alfonso

    2011-01-01

    This paper reports the design of a tactile sensor patch to cover large areas of robots and machines that interact with human beings. Many devices have been proposed to meet such a demand. These realizations are mostly custom-built or developed in the lab. The sensor of this paper is implemented with commercial force sensors. This has the benefit of a more foreseeable response of the sensor if its behavior is understood as the aggregation of readings from all the individual force sensors in the array. A few reported large area tactile sensors are also based on commercial sensors. However, the one in this paper is the first of this kind based on the use of polymeric commercial force sensing resistors (FSR) as unit elements of the array or tactels, which results in a robust sensor. The paper discusses design issues related to some necessary modifications of the force sensor, its assembly in an array, and the signal conditioning. The patch has 16 × 9 force sensors mounted on a flexible printed circuit board with a spatial resolution of 18.5 mm. The force range of a tactel is 6 N and its sensitivity is 0.6 V/N. The array is read at a rate of 78 frames per second. Finally, two simple application examples are also carried out with the sensor mounted on the forearm of a rescue robot that communicates with the sensor through a CAN bus. PMID:22163910

  14. Signal processing with a summing operational amplifier in multicomponent potentiometric titrations.

    PubMed

    Parczewski, A

    1987-06-01

    It has been proved that application of two indicator electrodes connected to the ordinary titration apparatus through an auxiliary electronic device (a summing operational amplifier) significantly extends the scope of multicomponent potentiometric titrations in which the analytes are determined simultaneously from a single titration curve. For each analyte there is a corresponding potential jump on the titration curve. By application of the proposed auxiliary device, the sum of the electrode potentials is measured. The device also enables the relative sizes of the potential jumps at the end-points on the titration curve to be varied. The advantages of the proposed signal processing are exemplified by complexometric potentiometric titrations of Fe(III) and Cu(II) in mixtures, with a platinum electrode and a copper ion-selective electrode as the indicator electrodes.

  15. Potentiometric Response Characteristics of Membrane-Based Cs + -Selective Electrodes Containing Ionophore-Functionalized Polymeric Microspheres

    DOE PAGES

    Peper, Shane; Gonczy, Chad

    2011-01-01

    Csmore » + -selective solvent polymeric membrane-based ion-selective electrodes (ISEs) were developed by doping ethylene glycol-functionalized cross-linked polystyrene microspheres (P-EG) into a plasticized poly(vinyl chloride) (PVC) matrix containing sodium tetrakis-(3,5-bis(trifluoromethyl)phenyl) borate (TFPB) as the ion exchanger. A systematic study examining the effects of the membrane plasticizers bis(2-ethylhexyl) sebacate (DOS), 2-nitrophenyl octyl ether (NPOE), and 2-fluorophenyl nitrophenyl ether (FPNPE) on the potentiometric response and selectivity of the corresponding electrodes was performed. Under certain conditions, P-EG-based ion-selective electrodes (ISEs) containing TFPB and plasticized with NPOE exhibited a super-Nernstian response between 1 × 10 − 3 and 1 × 10 − 4  M + , a response characteristic not observed in analogous membranes plasticized with either DOS or FPNPE. Additionally, the performance of P-EG-based ISEs was compared to electrodes based on two mobile ionophores, a neutral lipophilic ethylene glycol derivative (ethylene glycol monooctadecyl ether (U-EG)) and a charged metallacarborane ionophore, sodium bis(dicarbollyl)cobaltate(III) (CC). In general, P-EG-based electrodes plasticized with FPNPE yielded the best performance, with a linear range from 10 -1 –10 -5  M + , a conventional lower detection limit of 8.1 × 10 − 6  M + , and a response slope of 57.7 mV/decade. The pH response of P-EG ISEs containing TFPB was evaluated for membranes plasticized with either NPOE or FPNPE. In both cases, the electrodes remained stable throughout the pH range 3–12, with only slight proton interference observed below pH 3.« less

  16. Polyimide-Based Capacitive Humidity Sensor

    PubMed Central

    Steinmaßl, Matthias; Endres, Hanns-Erik; Drost, Andreas; Eisele, Ignaz; Kutter, Christoph; Müller-Buschbaum, Peter

    2018-01-01

    The development of humidity sensors with simple transduction principles attracts considerable interest by both scientific researchers and industrial companies. Capacitive humidity sensors, based on polyimide sensing material with different thickness and surface morphologies, are prepared. The surface morphology of the sensing layer is varied from flat to rough and then to nanostructure called nanograss by using an oxygen plasma etch process. The relative humidity (RH) sensor selectively responds to the presence of water vapor by a capacitance change. The interaction between polyimide and water molecules is studied by FTIR spectroscopy. The complete characterization of the prepared capacitive humidity sensor performance is realized using a gas mixing setup and an evaluation kit. A linear correlation is found between the measured capacitance and the RH level in the range of 5 to 85%. The morphology of the humidity sensing layer is revealed as an important parameter influencing the sensor performance. It is proved that a nanograss-like structure is the most effective for detecting RH, due to its rapid response and recovery times, which are comparable to or even better than the ones of commercial polymer-based sensors. This work demonstrates the readiness of the developed RH sensor technology for industrialization. PMID:29751632

  17. Small-volume potentiometric titrations: EPR investigations of Fe-S cluster N2 in mitochondrial complex I.

    PubMed

    Wright, John J; Salvadori, Enrico; Bridges, Hannah R; Hirst, Judy; Roessler, Maxie M

    2016-09-01

    EPR-based potentiometric titrations are a well-established method for determining the reduction potentials of cofactors in large and complex proteins with at least one EPR-active state. However, such titrations require large amounts of protein. Here, we report a new method that requires an order of magnitude less protein than previously described methods, and that provides EPR samples suitable for measurements at both X- and Q-band microwave frequencies. We demonstrate our method by determining the reduction potential of the terminal [4Fe-4S] cluster (N2) in the intramolecular electron-transfer relay in mammalian respiratory complex I. The value determined by our method, E m7 =-158mV, is precise, reproducible, and consistent with previously reported values. Our small-volume potentiometric titration method will facilitate detailed investigations of EPR-active centres in non-abundant and refractory proteins that can only be prepared in small quantities. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  18. Chemically modified carbon paste and membrane sensors for the determination of benzethonium chloride and some anionic surfactants (SLES, SDS, and LABSA): Characterization using SEM and AFM.

    PubMed

    Issa, Yousry M; Mohamed, Sabrein H; Baset, Mohamed Abd-El

    2016-08-01

    Chemically modified carbon-paste (CMCP) and membrane- sensors based on incorporating benzothonium-tetraphenylborate (BT-TPB) were constructed for the analysis of benzethonium chloride, and some other surfactants such as sodium lauryl ether sulphate (SLES), sodium dodecyl sulphate (SDS), and linear alkylbenzene sulphonic acid (LABSA). All sensors showed good sensitivity and reverse wide linearity over a concentration range of 5.97×10(-7) to 1.00×10(-3) and 5.96×10(-7) to 3.03×10(-3)molL(-1) with limit of detection of 3.92×10(-7)and 3.40×10(-7)molL(-1) for membrane and chemically modified carbon paste sensors, respectively, with respect to benzethonium chloride (BT.Cl). They could be used over a wide pH range of 2.0-10.0. The thermal coefficients of membrane and CMCP sensors are 5.40×10(-4), 1.17×10(-4)V/°C, respectively. The sensors indicated a wide selectivity over different inorganic cations. The effect of soaking on the surface morphology of the membrane sensor was studied using EDX-SEM and AFM techniques. The response time was <10s The freshly prepared, exhausted membrane, and CMCP sensors were successfully applied for the potentiometric determination of the pure BT.Cl solution. They were also used for the determination of its pharmaceutical formulation Dermoplast(®) antibacterial spray (20% benzocaine+0.2% benzethonium chloride) with recovery values ranging from 97.54±1.70 to 101.25±1.12 and from 96.32±2.49 to 101.23±2.15%. The second goal of these sensors is the potentiometric determination of different surfactants such as SLES, SDS, and LABSA with good recovery values using BT.Cl as a titrant in their pure forms, and in samples containing one of them (shampoo, Touri(®) dishwashing liquid, and waste water). The statistical analysis of the obtained data was studied. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Force/torque and tactile sensors for sensor-based manipulator control

    NASA Technical Reports Server (NTRS)

    Vanbrussel, H.; Belieen, H.; Bao, Chao-Ying

    1989-01-01

    The autonomy of manipulators, in space and in industrial environments, can be dramatically enhanced by the use of force/torque and tactile sensors. The development and future use of a six-component force/torque sensor for the Hermes Robot Arm (HERA) Basic End-Effector (BEE) is discussed. Then a multifunctional gripper system based on tactile sensors is described. The basic transducing element of the sensor is a sheet of pressure-sensitive polymer. Tactile image processing algorithms for slip detection, object position estimation, and object recognition are described.

  20. Optical fiber-based sensors: application to chemical biology.

    PubMed

    Brogan, Kathryn L; Walt, David R

    2005-10-01

    Optical fibers have been used to develop sensors based on nucleic acids and cells. Sensors employing DNA probes have been developed for various genomics applications and microbial pathogen detection. Live cell-based sensors have enabled the monitoring of environmental toxins, and have been used for fundamental studies on populations of individual cells. Both single-core optical fiber sensors and optical fiber sensor arrays have been used for sensing based on nucleic acids and live cells.

  1. Creating potentiometric surfaces from combined water well and oil well data in the midcontinent of the United States

    USGS Publications Warehouse

    Gianoutsos, Nicholas J.; Nelson, Philip H.

    2013-01-01

    For years, hydrologists have defined potentiometric surfaces using measured hydraulic-head values in water wells from aquifers. Down-dip, the oil and gas industry is also interested in the formation pressures of many of the same geologic formations for the purpose of hydrocarbon recovery. In oil and gas exploration, drillstem tests (DSTs) provide the formation pressure for a given depth interval in a well. These DST measurements can be used to calculate hydraulic-head values in deep hydrocarbon-bearing formations in areas where water wells do not exist. Unlike hydraulic-head measurements in water wells, which have a low number of problematic data points (outliers), only a small subset of the DST data measure true formation pressures. Using 3D imaging capabilities to view and clean the data, we have developed a process to estimate potentiometric surfaces from erratic DST data sets of hydrocarbon-bearing formations in the midcontinent of the U.S. The analysis indicates that the potentiometric surface is more readily defined through human interpretation of the chaotic DST data sets rather than through the application of filtering and geostatistical analysis. The data are viewed as a series of narrow, 400-mile-long swaths and a 2D viewer is used to select a subset of hydraulic-head values that represent the potentiometric surface. The user-selected subsets for each swath are then combined into one data set for each formation. These data are then joined with the hydraulic-head values from water wells to define the 3D potentiometric surfaces. The final product is an interactive, 3D digital display containing: (1) the subsurface structure of the formation, (2) the cluster of DST-derived hydraulic head values, (3) the user-selected subset of hydraulic-head values that define the potentiometric surface, (4) the hydraulic-head measurements from the corresponding shallow aquifer, (5) the resulting potentiometric surface encompassing both oil and gas and water wells, and (6

  2. A Comprehensive Review of Glucose Biosensors Based on Nanostructured Metal-Oxides

    PubMed Central

    Rahman, Md. Mahbubur; Saleh Ahammad, A. J.; Jin, Joon-Hyung; Ahn, Sang Jung; Lee, Jae-Joon

    2010-01-01

    Nanotechnology has opened new and exhilarating opportunities for exploring glucose biosensing applications of the newly prepared nanostructured materials. Nanostructured metal-oxides have been extensively explored to develop biosensors with high sensitivity, fast response times, and stability for the determination of glucose by electrochemical oxidation. This article concentrates mainly on the development of different nanostructured metal-oxide [such as ZnO, Cu(I)/(II) oxides, MnO2, TiO2, CeO2, SiO2, ZrO2, and other metal-oxides] based glucose biosensors. Additionally, we devote our attention to the operating principles (i.e., potentiometric, amperometric, impedimetric and conductometric) of these nanostructured metal-oxide based glucose sensors. Finally, this review concludes with a personal prospective and some challenges of these nanoscaled sensors. PMID:22399911

  3. Detection of copper, lead, cadmium and iron in wine using electronic tongue sensor system.

    PubMed

    Simões da Costa, A M; Delgadillo, I; Rudnitskaya, A

    2014-11-01

    An array of 10 potentiometric chemical sensors has been applied to the detection of total Fe, Cu, Pb and Cd content in digested wine. As digestion of organic matter of wine is necessary prior to the trace metal detection using potentiometric sensors, sample preparation procedures have been optimized. Different variants of wet and microwave digestion and dry ashing, 14 conditions in total, have been tested. Decomposition of organic matter was assessed using Fourier transform mid-infrared spectroscopy and total phenolic content. Dry ashing was found to be the most effective method of wine digestion. Measurements with sensors in individual solutions of Fe(III), Cu(II), Pb(II) and Cd(II) prepared on different backgrounds have shown that their detection limits were below typical concentration levels of these metals in wines and, in the case of Cu, Pb and Cd below maximum allowed concentrations. Detection of Fe in digested wine samples was possible using discrete iron-sensitive sensors with chalcogenide glass membranes with RMSEP of 0.05 mmol L(-1) in the concentration range from 0.0786 to 0.472 mmol L(-1). Low concentration levels of Cu, Pb and Cd in wine and cross-sensitivity of respective sensors resulted in the non-linearity of their responses, requiring back-propagation neural network for the calibration. Calibration models have been calculated using measurements in the model mixed solutions containing all three metals and a set of digested wine sample. RMSEP values for Cu, Pb and Cd were 3.9, 39 and 1.2 μmol L(-1) in model solutions and 2, 150 and 1 μmol L(-1) in digested wine samples. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Analysis of Mathematical Modelling on Potentiometric Biosensors

    PubMed Central

    Mehala, N.; Rajendran, L.

    2014-01-01

    A mathematical model of potentiometric enzyme electrodes for a nonsteady condition has been developed. The model is based on the system of two coupled nonlinear time-dependent reaction diffusion equations for Michaelis-Menten formalism that describes the concentrations of substrate and product within the enzymatic layer. Analytical expressions for the concentration of substrate and product and the corresponding flux response have been derived for all values of parameters using the new homotopy perturbation method. Furthermore, the complex inversion formula is employed in this work to solve the boundary value problem. The analytical solutions obtained allow a full description of the response curves for only two kinetic parameters (unsaturation/saturation parameter and reaction/diffusion parameter). Theoretical descriptions are given for the two limiting cases (zero and first order kinetics) and relatively simple approaches for general cases are presented. All the analytical results are compared with simulation results using Scilab/Matlab program. The numerical results agree with the appropriate theories. PMID:25969765

  5. Analysis of mathematical modelling on potentiometric biosensors.

    PubMed

    Mehala, N; Rajendran, L

    2014-01-01

    A mathematical model of potentiometric enzyme electrodes for a nonsteady condition has been developed. The model is based on the system of two coupled nonlinear time-dependent reaction diffusion equations for Michaelis-Menten formalism that describes the concentrations of substrate and product within the enzymatic layer. Analytical expressions for the concentration of substrate and product and the corresponding flux response have been derived for all values of parameters using the new homotopy perturbation method. Furthermore, the complex inversion formula is employed in this work to solve the boundary value problem. The analytical solutions obtained allow a full description of the response curves for only two kinetic parameters (unsaturation/saturation parameter and reaction/diffusion parameter). Theoretical descriptions are given for the two limiting cases (zero and first order kinetics) and relatively simple approaches for general cases are presented. All the analytical results are compared with simulation results using Scilab/Matlab program. The numerical results agree with the appropriate theories.

  6. Graphene-based biomimetic materials targeting urine metabolite as potential cancer biomarker: application over different conductive materials for potentiometric transduction.

    PubMed

    Truta, Liliana A A N A; Ferreira, Nádia S; Sales, M Goreti F

    2014-12-20

    This works presents a novel surface Smart Polymer Antibody Material (SPAM) for Carnitine (CRT, a potential biomarker of ovarian cancer), tested for the first time as ionophore in potentiometric electrodes of unconventional configuration. The SPAM material consisted of a 3D polymeric network created by surface imprinting on graphene layers. The polymer was obtained by radical polymerization of (vinylbenzyl)trimethylammonium chloride and 4-styrenesulfonic acid (signaling the binding sites), and vinyl pivalate and ethylene glycol dimethacrylate (surroundings). Non-imprinted material (NIM) was prepared as control, by excluding the template from the procedure. These materials were then used to produce several plasticized PVC membranes, testing the relevance of including the SPAM as ionophore, and the need for a charged lipophilic additive. The membranes were casted over solid conductive supports of graphite or ITO/FTO. The effect of pH upon the potentiometric response was evaluated for different pHs (2-9) with different buffer compositions. Overall, the best performance was achieved for membranes with SPAM ionophore, having a cationic lipophilic additive and tested in HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer, pH 5.1. Better slopes were achieved when the membrane was casted on conductive glass (-57.4mV/decade), while the best detection limits were obtained for graphite-based conductive supports (3.6×10 -5 mol/L). Good selectivity was observed against BSA, ascorbic acid, glucose, creatinine and urea, tested for concentrations up to their normal physiologic levels in urine. The application of the devices to the analysis of spiked samples showed recoveries ranging from 91% (± 6.8%) to 118% (± 11.2%). Overall, the combination of the SPAM sensory material with a suitable selective membrane composition and electrode design has lead to a promising tool for point-of-care applications.

  7. Graphene-based biomimetic materials targeting urine metabolite as potential cancer biomarker: application over different conductive materials for potentiometric transduction

    PubMed Central

    Truta, Liliana A.A.N.A.; Ferreira, Nádia S.; Sales, M. Goreti F.

    2015-01-01

    This works presents a novel surface Smart Polymer Antibody Material (SPAM) for Carnitine (CRT, a potential biomarker of ovarian cancer), tested for the first time as ionophore in potentiometric electrodes of unconventional configuration. The SPAM material consisted of a 3D polymeric network created by surface imprinting on graphene layers. The polymer was obtained by radical polymerization of (vinylbenzyl)trimethylammonium chloride and 4-styrenesulfonic acid (signaling the binding sites), and vinyl pivalate and ethylene glycol dimethacrylate (surroundings). Non-imprinted material (NIM) was prepared as control, by excluding the template from the procedure. These materials were then used to produce several plasticized PVC membranes, testing the relevance of including the SPAM as ionophore, and the need for a charged lipophilic additive. The membranes were casted over solid conductive supports of graphite or ITO/FTO. The effect of pH upon the potentiometric response was evaluated for different pHs (2-9) with different buffer compositions. Overall, the best performance was achieved for membranes with SPAM ionophore, having a cationic lipophilic additive and tested in HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid) buffer, pH 5.1. Better slopes were achieved when the membrane was casted on conductive glass (−57.4mV/decade), while the best detection limits were obtained for graphite-based conductive supports (3.6×10−5mol/L). Good selectivity was observed against BSA, ascorbic acid, glucose, creatinine and urea, tested for concentrations up to their normal physiologic levels in urine. The application of the devices to the analysis of spiked samples showed recoveries ranging from 91% (± 6.8%) to 118% (± 11.2%). Overall, the combination of the SPAM sensory material with a suitable selective membrane composition and electrode design has lead to a promising tool for point-of-care applications. PMID:26456975

  8. Modeling the acid-base properties of bacterial surfaces: A combined spectroscopic and potentiometric study of the gram-positive bacterium Bacillus subtilis.

    PubMed

    Leone, Laura; Ferri, Diego; Manfredi, Carla; Persson, Per; Shchukarev, Andrei; Sjöberg, Staffan; Loring, John

    2007-09-15

    In this study, macroscopic and spectroscopic data were combined to develop a surface complexation model that describes the acid-base properties of Bacillus subtilis. The bacteria were freeze-dried and then resuspended in 0.1 M NaCl ionic medium. Macroscopic measurements included potentiometric acid-base titrations and electrophoretic mobility measurements. In addition, ATR-FTIR spectra of wet pastes from suspensions of Bacillus subtilis at different pH values were collected. The least-squares program MAGPIE was used to generate a surface complexation model that takes into account the presence of three acid-base sites on the surface: tripple bond COOH, tripple bond NH+, and tripple bond PO-, which were identified previously by XPS measurements. Both potentiometric titration data and ATR-FTIR spectra were used quantitatively, and electrostatic effects at the charged bacterial surface were accounted for using the constant capacitance model. The model was calculated using two different approaches: in the first one XPS data were used to constrain the ratio of the total concentrations of all three surface sites. The capacitance of the double layer, the total buffer capacity, and the deprotonation constants of the tripple bond NH+, tripple bond POH, and tripple bond COOH species were determined in the fit. A second approach is presented in which the ratio determined by XPS of the total concentrations of tripple bond NH+ to tripple bond PO- sites is relaxed. The total concentration of tripple bond PO- sites was determined in the fit, while the deprotonation constant for tripple bond POH was manually varied until the minimization led to a model which predicted an isoelectric point that resulted in consistency with electrophoretic mobility data. The model explains well the buffering capacity of Bacillus subtilis suspensions in a wide pH range (between pH=3 and pH=9) which is of considerable environmental interest. In particular, a similar quantitative use of the IR data

  9. Potentiometric surfaces of the intermediate aquifer system, west-central Florida, May, 1993

    USGS Publications Warehouse

    Mularoni, R.A.

    1994-01-01

    The intermediate aquifer system underlies a 5000-sq-mi area including De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, and Polk Counties, Florida. It is overlain by the surf@cial aquifer system and underlain by the Floridan aquifer system. The potentiometric surface of the intermediate aquifer system was mapped by determining the altitude of water levels in a network of wells and represented on a map by contours that connect points of equal altitude. This map represents water-level conditions near the end of the spring dry season when ground- water withdrawals for agricultural use were high. The cumulative rainfall for the study area was 4.84 inches above normal for the period from June 1992 to May 1993. Hydrographs for selected wells indicated that the annual and seasonal fluctuations of the water levels were generally large (greater than 15 feet) in the central interior region where water demand for irrigation is high during the fall and spring. Seasonal fluctuations were smaller in the northern recharge area where water use is predominantly for public supply. Water levels measured in May 1993 for the composite intermediate aquifer potentiometric surface were lower than those measured in May or September 1992. A cone of depression exists in the potentiometric surface for the composite aquifer system at Warm Mineral Springs, which is a natural discharge point from this system.

  10. Indium oxide based fiber optic SPR sensor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shukla, Sarika; Sharma, Navneet K., E-mail: navneetk.sharma@jiit.ac.in

    2016-05-06

    Surface plasmon resonance based fiber optic sensor using indium oxide layer is presented and theoretically studied. It has been found that with increase in thickness of indium oxide layer beyond 170 nm, the sensitivity of SPR sensor decreases. 170 nm thick indium oxide layer based SPR sensor holds maximum sensitivity.

  11. Relationship between potentiometric measurements, sensorial analysis, and some substances responsible for aroma degradation of white wines.

    PubMed

    Silva Ferreira, A C; Oliveira, Carla; Hogg, T; Guedes de Pinho, P

    2003-07-30

    Oxidative degradation of white wines can be described sensorially as developing from a loss at positive aroma characteristics, through the development of negative aromas to a linel stage of chromatic alterations. This work attempts to relate the oxidation "status" evaluate by potentiometric titrations, with sensorial degradation and the levels of substances responsible for "off-flavors", such as methional and phenylacetaldehyde. The potentiometric titration employed measures the most powerful antioxidants of white wines (e.g., those which more rapidly consume oxygen). Considering that aromatic precedes chromatic degradation, resistance to oxidation (ROX) constitutes a useful indicator of resistance to oxidation. Sensorial degradation (ID), potentiometric measures, and volatiles were determined both in samples submitted to a "forced aging" protocol and normal aged white wines. High correlation values were observed between ROX and the ID, in both sets (r > 0.87). ID is better explained by ROX values than by the indicated wine age or by the "degree of browning" (Abs = 420 nm). It was also observed that in samples with ROX values higher than 10, the concentration of methional and phenylacetaldehyde were above their respective odor threshold. Finally, it was observed that there is a relationship between oxygen consumption and the respective ROX. Although these results seem very promising, they needed to be further complemented in order to estimate the shelf life of a white wine using potentiometric titrations.

  12. Reagentless, Structure-Switching, Electrochemical Aptamer-Based Sensors

    NASA Astrophysics Data System (ADS)

    Schoukroun-Barnes, Lauren R.; Macazo, Florika C.; Gutierrez, Brenda; Lottermoser, Justine; Liu, Juan; White, Ryan J.

    2016-06-01

    The development of structure-switching, electrochemical, aptamer-based sensors over the past ˜10 years has led to a variety of reagentless sensors capable of analytical detection in a range of sample matrices. The crux of this methodology is the coupling of target-induced conformation changes of a redox-labeled aptamer with electrochemical detection of the resulting altered charge transfer rate between the redox molecule and electrode surface. Using aptamer recognition expands the highly sensitive detection ability of electrochemistry to a range of previously inaccessible analytes. In this review, we focus on the methods of sensor fabrication and how sensor signaling is affected by fabrication parameters. We then discuss recent studies addressing the fundamentals of sensor signaling as well as quantitative characterization of the analytical performance of electrochemical aptamer-based sensors. Although the limits of detection of reported electrochemical aptamer-based sensors do not often reach that of gold-standard methods such as enzyme-linked immunosorbent assays, the operational convenience of the sensor platform enables exciting analytical applications that we address. Using illustrative examples, we highlight recent advances in the field that impact important areas of analytical chemistry. Finally, we discuss the challenges and prospects for this class of sensors.

  13. LWT Based Sensor Node Signal Processing in Vehicle Surveillance Distributed Sensor Network

    NASA Astrophysics Data System (ADS)

    Cha, Daehyun; Hwang, Chansik

    Previous vehicle surveillance researches on distributed sensor network focused on overcoming power limitation and communication bandwidth constraints in sensor node. In spite of this constraints, vehicle surveillance sensor node must have signal compression, feature extraction, target localization, noise cancellation and collaborative signal processing with low computation and communication energy dissipation. In this paper, we introduce an algorithm for light-weight wireless sensor node signal processing based on lifting scheme wavelet analysis feature extraction in distributed sensor network.

  14. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2006

    USGS Publications Warehouse

    Ortiz, A.G.

    2007-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2006. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 46.06 inches for west-central Florida (from October 2005 through September 2006) was 6.91 inches below the historical cumulative average of 52.97 inches (Southwest Florida Water Management District, 2006). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each

  15. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, September 2005

    USGS Publications Warehouse

    Ortiz, A.G.

    2006-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public-supply, domestic use, irrigation, and brackish-water desalination in coastal communities (Southwest Florida Water Management District, 2000).This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2005. The potentiometric surface is an imaginary surface, connecting points of equal altitude to which water will rise in tightly cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 55.19 inches for west-central Florida (from October 2004 through September 2005) was 2.00 inches above the historical cumulative average of 53.19 inches (Southwest Florida Water Management District, 2005). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District.This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year

  16. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2007

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 39.50 inches for west-central Florida (from October 2006 through September 2007) was 13.42 inches below the historical cumulative average of 52.92 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each

  17. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, September 2008

    USGS Publications Warehouse

    Ortiz, Anita G.

    2009-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2008. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 50.63 inches for west-central Florida (from October 2007 through September 2008) was 2.26 inches below the historical cumulative average of 52.89 inches (Southwest Florida Water Management District, 2008). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each

  18. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2008

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2008. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 46.95 inches for west-central Florida (from June 2007 through May 2008) was 5.83 inches below the historical cumulative average of 52.78 inches (Southwest Florida Water Management District, 2008). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  19. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2007

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 41.21 inches for west-central Florida (from June 2006 through May 2007) was 11.63 inches below the historical cumulative average of 52.84 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  20. Comparison between amperometric and true potentiometric end-point detection in the determination of water by the Karl Fischer method.

    PubMed

    Cedergren, A

    1974-06-01

    A rapid and sensitive method using true potentiometric end-point detection has been developed and compared with the conventional amperometric method for Karl Fischer determination of water. The effect of the sulphur dioxide concentration on the shape of the titration curve is shown. By using kinetic data it was possible to calculate the course of titrations and make comparisons with those found experimentally. The results prove that the main reaction is the slow step, both in the amperometric and the potentiometric method. Results obtained in the standardization of the Karl Fischer reagent showed that the potentiometric method, including titration to a preselected potential, gave a standard deviation of 0.001(1) mg of water per ml, the amperometric method using extrapolation 0.002(4) mg of water per ml and the amperometric titration to a pre-selected diffusion current 0.004(7) mg of water per ml. Theories and results dealing with dilution effects are presented. The time of analysis was 1-1.5 min for the potentiometric and 4-5 min for the amperometric method using extrapolation.

  1. Potentiometric surface of the Floridan Aquifer, St. Johns River Water Management District and vicinity, Florida, May 1981

    USGS Publications Warehouse

    Schiner, George R.; Hayes, Eugene C.

    1981-01-01

    This map presents the potentiometric surface of the Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1981. The Floridan aquifer is the principal source of potable water in the area. Water-level measurements were made in approximately 1,000 wells and at several springs. The potentiometric surface is shown mostly by 5-foot contour intervals. In the Fernandina Beach area 20 and 40-foot intervals are used to show a deep cone of depression. The potentiometric surface ranged from 122 feet above NGVD (National Geodetic Vertical Datum of 1929) in Polk County to 125 feet below NGVD in Nassau County. Water levels were at record lows in many counties due to lack of rainfall. Declines were as much as 10 feet and commonly 5 feet from the May 1980 levels. (USGS)

  2. Accurate potentiometric determination of lipid membrane-water partition coefficients and apparent dissociation constants of ionizable drugs: electrostatic corrections.

    PubMed

    Elsayed, Mustafa M A; Vierl, Ulrich; Cevc, Gregor

    2009-06-01

    Potentiometric lipid membrane-water partition coefficient studies neglect electrostatic interactions to date; this leads to incorrect results. We herein show how to account properly for such interactions in potentiometric data analysis. We conducted potentiometric titration experiments to determine lipid membrane-water partition coefficients of four illustrative drugs, bupivacaine, diclofenac, ketoprofen and terbinafine. We then analyzed the results conventionally and with an improved analytical approach that considers Coulombic electrostatic interactions. The new analytical approach delivers robust partition coefficient values. In contrast, the conventional data analysis yields apparent partition coefficients of the ionized drug forms that depend on experimental conditions (mainly the lipid-drug ratio and the bulk ionic strength). This is due to changing electrostatic effects originating either from bound drug and/or lipid charges. A membrane comprising 10 mol-% mono-charged molecules in a 150 mM (monovalent) electrolyte solution yields results that differ by a factor of 4 from uncharged membranes results. Allowance for the Coulombic electrostatic interactions is a prerequisite for accurate and reliable determination of lipid membrane-water partition coefficients of ionizable drugs from potentiometric titration data. The same conclusion applies to all analytical methods involving drug binding to a surface.

  3. Inorganic Thin-film Sensor Membranes with PLD-prepared Chalcogenide Glasses: Challenges and Implementation

    PubMed Central

    Kloock, Joachim P.; Mourzina, Youlia G.; Ermolenko, Yuri; Doll, Theodor; Schubert, Jürgen; Schöning, Michael J.

    2004-01-01

    Chalcogenide glasses offer an excellent “challenge” for their use and implementation in sensor arrays due to their good sensor-specific advantages in comparison to their crystalline counterparts. This paper will give an introduction on the preparation of chalcogenide glasses in the thin-film state. First, single microsensors have been prepared with the methods of semiconductor technology. In a next step, three microsensors are implemented onto one single silicon substrate to an “one chip” sensor array. Different ionselective chalcogenide glass membranes (PbSAgIAs2S3, CdSAgIAs2S3, CuAgAsSeTe and TlAgAsIS) were prepared by means of the pulsed laser deposition (PLD) process. The different sensor membranes and structures have been physically characterized by means of Rutherford backscattering spectrometry, scanning electron microscopy and video microscopy. The electrochemical behavior has been investigated by potentiometric measurements.

  4. Application of cause-and-effect analysis to potentiometric titration.

    PubMed

    Kufelnicki, A; Lis, S; Meinrath, G

    2005-08-01

    A first attempt has been made to interpret physicochemical data from potentiometric titration analysis in accordance with the complete measurement-uncertainty budget approach (bottom-up) of ISO and Eurachem. A cause-and-effect diagram is established and discussed. Titration data for arsenazo III are used as a basis for this discussion. The commercial software Superquad is used and applied within a computer-intensive resampling framework. The cause-and-effect diagram is applied to evaluation of seven protonation constants of arsenazo III in the pH range 2-10.7. The data interpretation is based on empirical probability distributions and their analysis by second-order correct confidence estimates. The evaluated data are applied in the calculation of a speciation diagram including uncertainty estimates using the probabilistic speciation software Ljungskile.

  5. Observability-Based Guidance and Sensor Placement

    NASA Astrophysics Data System (ADS)

    Hinson, Brian T.

    Control system performance is highly dependent on the quality of sensor information available. In a growing number of applications, however, the control task must be accomplished with limited sensing capabilities. This thesis addresses these types of problems from a control-theoretic point-of-view, leveraging system nonlinearities to improve sensing performance. Using measures of observability as an information quality metric, guidance trajectories and sensor distributions are designed to improve the quality of sensor information. An observability-based sensor placement algorithm is developed to compute optimal sensor configurations for a general nonlinear system. The algorithm utilizes a simulation of the nonlinear system as the source of input data, and convex optimization provides a scalable solution method. The sensor placement algorithm is applied to a study of gyroscopic sensing in insect wings. The sensor placement algorithm reveals information-rich areas on flexible insect wings, and a comparison to biological data suggests that insect wings are capable of acting as gyroscopic sensors. An observability-based guidance framework is developed for robotic navigation with limited inertial sensing. Guidance trajectories and algorithms are developed for range-only and bearing-only navigation that improve navigation accuracy. Simulations and experiments with an underwater vehicle demonstrate that the observability measure allows tuning of the navigation uncertainty.

  6. Potentiometric surface of the upper Floridan aquifer in Florida and in parts of Georgia, South Carolina, and Alabama, May 1985

    USGS Publications Warehouse

    Bush, Peter W.; Barr, G. Lynn; Clarke, John S.; Johnston, Richard H.

    1987-01-01

    A map, constructed as a part of the Floridan Regional Aquifer-System Analysis (RASA), shows the potentiometric surface of the Upper Floridan aquifer for May 1985. It is based on measurements of water level or artesian pressure made in about 2 ,500 wells during the period May 13 to 24, 1985. Only measurements from tightly cased wells open exclusively to the Upper Floridan aquifer were used to make the map. These included 1,425 wells in Florida, 924 in Georgia, 133 in South Carolina, and 21 in Alabama. The potentiometric surface of the Upper Floridan aquifer changed little between 1980 and 1985. Significant water level declines were observed only in southwest Georgia and west-central Florida. Low rainfall during early 1985 and associated pumping for irrigation caused the declines in both areas. (Lantz-PTT)

  7. A fluidics-based impact sensor

    PubMed Central

    Takahashi, Daigo; Hara, Keisuke; Okano, Taiji

    2018-01-01

    Microelectromechanical systems (MEMS)-based high-performance accelerometers are ubiquitously used in various electronic devices. However, there is an existing need to detect physical impacts using low-cost devices with no electronic circuits or a battery. We designed and fabricated an impact sensor prototype using a commercial stereolithography apparatus that only consists of a plastic housing and working fluids. The sensor device responds to the instantaneous acceleration (impact) by deformation and pinch off of a water droplet that is suspended in oil in a sensor cavity. We tested the various geometrical and physical parameters of the impact sensor to identify their relations to threshold acceleration values. We show that the state diagram that is plotted against the dimensionless Archimedes and Bond numbers adequately describes the response of the proposed sensor. PMID:29634750

  8. Recent progress in graphene-material-based optical sensors.

    PubMed

    Deng, Xianghua; Tang, Hao; Jiang, Jianhui

    2014-11-01

    Graphene material has been widely used for optical sensors owing to its excellent properties, including high-energy transfer efficiency, large surface area, and great biocompatibility. Different analytes such as nucleic acids, proteins, and small molecules can be detected by graphene-material-based optical sensors. This review provides a comprehensive discussion of graphene-material-based optical sensors focusing on detection mechanisms and biosensor designs. Challenges and future perspectives for graphene-material-based optical sensors are also presented.

  9. Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District, May 1981

    USGS Publications Warehouse

    Yobbi, D.K.; Woodham, W.M.; Schiner, George R.

    1981-01-01

    A May 1981 potentiometric-surface map of the Southwest Florida Water Management District depicts the annual low water-level period. Potentiometric levels decreased 10 to 45 feet between September 1980 and May 1981 in the citrus and farming sections of southern Hillsborough, northern Hardee, southwestern Polk, northwestern DeSoto, and Manatee Counties. Water levels in these areas are widely affected by pumping for irrigation and have the greatest range in fluctuations. Water-level decreases ranged from 0 to 1 feet in coastal, northern, and southern areas of the Water Management District. Water levels in all of the approximate 700 wells measured in May 1981 are lower than May 1980 because of the virtual absence of rainfall in April and May. (USGS)

  10. Potentiometric Surface of the Upper Patapsco Aquifer in Southern Maryland, September 1995

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Mack, Frederick K.

    1996-01-01

    A map showing the potentiometric surface of the upper Patapsco aquifer in the Patapsco Formation of Cretaceous age in southern Maryland during September 1995 was prepared from water-level measurements in 42 wells. The potentiometric surface was nearly 120 feet above sea level near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel County, and 55 feet above sea level in a similar setting in Prince Georges County. From these high areas, the potentiometic surface declined to the south and southeast toward large well fields in the Annapolis and Waldorf areas and at the Chalk Point powerplant. Ground-water levels reached nearly 30 feet below sea level in the Annapolis area, 113 feet below sea level southwest of Waldorf, and more than 30 feet below sea level at the Chalk Point powerplant.

  11. Transmission-grating-based wavefront tilt sensor.

    PubMed

    Iwata, Koichi; Fukuda, Hiroki; Moriwaki, Kousuke

    2009-07-10

    We propose a new type of tilt sensor. It consists of a grating and an image sensor. It detects the tilt of the collimated wavefront reflected from a plane mirror. Its principle is described and analyzed based on wave optics. Experimental results show its validity. Simulations of the ordinary autocollimator and the proposed tilt sensor show that the effect of noise on the measured angle is smaller for the latter. These results show a possibility of making a smaller and simpler tilt sensor.

  12. Voltammetric Thin-Layer Ionophore-Based Films: Part 2. Semi-Empirical Treatment.

    PubMed

    Yuan, Dajing; Cuartero, Maria; Crespo, Gaston A; Bakker, Eric

    2017-01-03

    This work reports on a semiempirical treatment that allows one to rationalize and predict experimental conditions for thin-layer ionophore-based films with cation-exchange capacity read out with cyclic voltammetry. The transition between diffusional mass transport and thin-layer regime is described with a parameter (α), which depends on membrane composition, diffusion coefficient, scan rate, and electrode rotating speed. Once the thin-layer regime is fulfilled (α = 1), the membrane behaves in some analogy to a potentiometric sensor with a second discrimination variable (the applied potential) that allows one to operate such electrodes in a multianalyte detection mode owing to the variable applied ion-transfer potentials. The limit of detection of this regime is defined with a second parameter (β = 2) and is chosen in analogy to the definition of the detection limit for potentiometric sensors provided by the IUPAC. The analytical equations were validated through the simulation of the respective cyclic voltammograms under the same experimental conditions. While simulations of high complexity and better accuracy satisfactorily reproduced the experimental voltammograms during the forward and backward potential sweeps (companion paper 1), the semiempirical treatment here, while less accurate, is of low complexity and allows one to quite easily predict relevant experimental conditions for this emergent methodology.

  13. Physiological sensor signals classification for healthcare using sensor data fusion and case-based reasoning.

    PubMed

    Begum, Shahina; Barua, Shaibal; Ahmed, Mobyen Uddin

    2014-07-03

    Today, clinicians often do diagnosis and classification of diseases based on information collected from several physiological sensor signals. However, sensor signal could easily be vulnerable to uncertain noises or interferences and due to large individual variations sensitivity to different physiological sensors could also vary. Therefore, multiple sensor signal fusion is valuable to provide more robust and reliable decision. This paper demonstrates a physiological sensor signal classification approach using sensor signal fusion and case-based reasoning. The proposed approach has been evaluated to classify Stressed or Relaxed individuals using sensor data fusion. Physiological sensor signals i.e., Heart Rate (HR), Finger Temperature (FT), Respiration Rate (RR), Carbon dioxide (CO2) and Oxygen Saturation (SpO2) are collected during the data collection phase. Here, sensor fusion has been done in two different ways: (i) decision-level fusion using features extracted through traditional approaches; and (ii) data-level fusion using features extracted by means of Multivariate Multiscale Entropy (MMSE). Case-Based Reasoning (CBR) is applied for the classification of the signals. The experimental result shows that the proposed system could classify Stressed or Relaxed individual 87.5% accurately compare to an expert in the domain. So, it shows promising result in the psychophysiological domain and could be possible to adapt this approach to other relevant healthcare systems.

  14. Standards-based sensor interoperability and networking SensorWeb: an overview

    NASA Astrophysics Data System (ADS)

    Bolling, Sam

    2012-06-01

    The War fighter lacks a unified Intelligence, Surveillance, and Reconnaissance (ISR) environment to conduct mission planning, command and control (C2), tasking, collection, exploitation, processing, and data discovery of disparate sensor data across the ISR Enterprise. Legacy sensors and applications are not standardized or integrated for assured, universal access. Existing tasking and collection capabilities are not unified across the enterprise, inhibiting robust C2 of ISR including near-real time, cross-cueing operations. To address these critical needs, the National Measurement and Signature Intelligence (MASINT) Office (NMO), and partnering Combatant Commands and Intelligence Agencies are developing SensorWeb, an architecture that harmonizes heterogeneous sensor data to a common standard for users to discover, access, observe, subscribe to and task sensors. The SensorWeb initiative long term goal is to establish an open commercial standards-based, service-oriented framework to facilitate plug and play sensors. The current development effort will produce non-proprietary deliverables, intended as a Government off the Shelf (GOTS) solution to address the U.S. and Coalition nations' inability to quickly and reliably detect, identify, map, track, and fully understand security threats and operational activities.

  15. MEMS-based thermoelectric infrared sensors: A review

    NASA Astrophysics Data System (ADS)

    Xu, Dehui; Wang, Yuelin; Xiong, Bin; Li, Tie

    2017-12-01

    In the past decade, micro-electromechanical systems (MEMS)-based thermoelectric infrared (IR) sensors have received considerable attention because of the advances in micromachining technology. This paper presents a review of MEMS-based thermoelectric IR sensors. The first part describes the physics of the device and discusses the figures of merit. The second part discusses the sensing materials, thermal isolation microstructures, absorber designs, and packaging methods for these sensors and provides examples. Moreover, the status of sensor implementation technology is examined from a historical perspective by presenting findings from the early years to the most recent findings.

  16. Recent Advances in Silicon Nanomaterial-Based Fluorescent Sensors.

    PubMed

    Wang, Houyu; He, Yao

    2017-02-03

    During the past decades, owing to silicon nanomaterials' unique optical properties, benign biocompatibility, and abundant surface chemistry, different dimensional silicon nanostructures have been widely employed for rationally designing and fabricating high-performance fluorescent sensors for the detection of various chemical and biological species. Among of these, zero-dimensional silicon nanoparticles (SiNPs) and one-dimensional silicon nanowires (SiNWs) are of particular interest. Herein, we focus on reviewing recent advances in silicon nanomaterials-based fluorescent sensors from a broad perspective and discuss possible future directions. Firstly, we introduce the latest achievement of zero-dimensional SiNP-based fluorescent sensors. Next, we present recent advances of one-dimensional SiNW-based fluorescent sensors. Finally, we discuss the major challenges and prospects for the development of silicon-based fluorescent sensors.

  17. Recent Advances in Silicon Nanomaterial-Based Fluorescent Sensors

    PubMed Central

    Wang, Houyu; He, Yao

    2017-01-01

    During the past decades, owing to silicon nanomaterials’ unique optical properties, benign biocompatibility, and abundant surface chemistry, different dimensional silicon nanostructures have been widely employed for rationally designing and fabricating high-performance fluorescent sensors for the detection of various chemical and biological species. Among of these, zero-dimensional silicon nanoparticles (SiNPs) and one-dimensional silicon nanowires (SiNWs) are of particular interest. Herein, we focus on reviewing recent advances in silicon nanomaterials-based fluorescent sensors from a broad perspective and discuss possible future directions. Firstly, we introduce the latest achievement of zero-dimensional SiNP-based fluorescent sensors. Next, we present recent advances of one-dimensional SiNW-based fluorescent sensors. Finally, we discuss the major challenges and prospects for the development of silicon-based fluorescent sensors. PMID:28165357

  18. Automated potentiometric electrolyte analysis system. [for use in weightlessness

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The feasibility is demonstrated of utilizing chemical sensing electrode technology as the basis for an automatically-controlled system for blood gas and electrolyte analyses under weightlessness conditions. The specific measurements required were pH, pCO2, sodium, chloride, potassium ions, and ionized calcium. The general electrode theory, and ion activity measurements are described along with the fluid transport package, electronics unit, and controller for the automated potentiometric analysis system.

  19. Potentiometric detection in UPLC as an easy alternative to determine cocaine in biological samples.

    PubMed

    Daems, Devin; van Nuijs, Alexander L N; Covaci, Adrian; Hamidi-Asl, Ezat; Van Camp, Guy; Nagels, Luc J

    2015-07-01

    The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra-high-pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3 ng mL(-1) were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25 ng mL(-1). A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost-effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable. Copyright © 2014 John Wiley & Sons, Ltd.

  20. Bioanalytical and chemical sensors using living taste, olfactory, and neural cells and tissues: a short review.

    PubMed

    Wu, Chunsheng; Lillehoj, Peter B; Wang, Ping

    2015-11-07

    Biosensors utilizing living tissues and cells have recently gained significant attention as functional devices for chemical sensing and biochemical analysis. These devices integrate biological components (i.e. single cells, cell networks, tissues) with micro-electro-mechanical systems (MEMS)-based sensors and transducers. Various types of cells and tissues derived from natural and bioengineered sources have been used as recognition and sensing elements, which are generally characterized by high sensitivity and specificity. This review summarizes the state of the art in tissue- and cell-based biosensing platforms with an emphasis on those using taste, olfactory, and neural cells and tissues. Many of these devices employ unique integration strategies and sensing schemes based on sensitive transducers including microelectrode arrays (MEAs), field effect transistors (FETs), and light-addressable potentiometric sensors (LAPSs). Several groups have coupled these hybrid biosensors with microfluidics which offers added benefits of small sample volumes and enhanced automation. While this technology is currently limited to lab settings due to the limited stability of living biological components, further research to enhance their robustness will enable these devices to be employed in field and clinical settings.

  1. Potentiometric Surfaces and Changes in Groundwater Levels in Selected Bedrock Aquifers in the Twin Cities Metropolitan Area, March-August 2008 and 1988-2008

    USGS Publications Warehouse

    Sanocki, Christopher A.; Langer, Susan K.; Menard, Jason C.

    2008-01-01

    This report depicts potentiometric surfaces and groundwater- level changes in three aquifers that underlie the seven-county Twin Cities Metropolitan Area. Approximately 350 groundwater levels were measured in wells from the three aquifers-the Prairie du Chien-Jordan, the Franconia-Ironton-Galesville, and the Mount Simon-Hinckley aquifers-in March and August of 2008. The report presents maps, associated data tables, and 22 geographic information system datasets. The maps presented in this report show the potentiometric surfaces in March and August of 2008 for all three aquifers, groundwater-level changes from March to August 2008 for each aquifer, and revised potentiometric-surface contours for the winter of 1988-89 for the Prairie du Chien-Jordan and the Mount Simon-Hinckley aquifers, and the estimated long-term (winter of 1988-89 to March 2008) groundwater-level changes for the Prairie du Chien-Jordan and Mount Simon-Hinckley aquifers. This report documents the methods used to construct the maps and provides a context for the period of the measurements. Although withdrawal demand is increasing in the Twin Cities Metropolitan area, particularly in the Prairie du Chien-Jordan aquifer, year-to-year changes in withdrawals can be substantial, and the relation between potentiometric surfaces in the major aquifers and year-to-year withdrawals is not well established. The estimated long-term (19-year) groundwater-level changes for the Prairie du Chien-Jordan and Mount Simon-Hinckley aquifers have not been large based on data and maps produced during this study, despite the large seasonal fluctuations shown by the March and August 2008 synoptic measurements.

  2. Novel cell-based odorant sensor elements based on insect odorant receptors.

    PubMed

    Mitsuno, Hidefumi; Sakurai, Takeshi; Namiki, Shigehiro; Mitsuhashi, Hiroyuki; Kanzaki, Ryohei

    2015-03-15

    Development of cell-based odorant sensor elements combined not only high degree of sensitivity and selectivity but also long-term stability is crucial for their practical applications. Here we report the development of a novel cell-based odorant sensor element that sensitively and selectively detects odorants and displays increased fluorescent intensities over a long period of time. Our odorant sensor elements, based on Sf21 cell lines expressing insect odorant receptors, are sensitive to the level of several tens of parts per billion in solution, can selectively distinguish between different types of odorants based on the odorant selectivity intrinsic to the expressed receptors, and have response times of approximately 13s. Specifically, with the use of Sf21 cells and insect odorant receptors, we demonstrated that the established cell lines stably expressing insect odorant receptors are able to detect odorants with consistent responsiveness for at least 2 months, thus exceeding the short life-span normally associated with cell-based sensors. We also demonstrated the development of a compact odorant sensor chip by integrating the established insect cell lines into a microfluidic chip. The methodology we established in this study, in conjunction with the large repertoire of insect odorant receptors, will aid in the development of practical cell-based odorant sensors for various applications, including food administration and health management. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Design of Inkjet-Printed RFID-Based Sensor on Paper: Single- and Dual-Tag Sensor Topologies.

    PubMed

    Kim, Sangkil; Georgiadis, Apostolos; Tentzeris, Manos M

    2018-06-17

    The detailed design considerations for the printed RFID-based sensor system is presented in this paper. Starting from material selection and metallization method, this paper discusses types of RFID-based sensors (single- & dual-tag sensor topologies), design procedures, and performance evaluation methods for the wireless sensor system. The electrical properties of the paper substrates (cellulose-based and synthetic papers) and the silver nano-particle-based conductive film are thoroughly characterized for RF applications up to 8 GHz. The reported technology could potentially set the foundation for truly “green”, low-cost, scalable wireless topologies for autonomous Internet-of-Things (IoT), bio-monitoring, and “smart skin” applications.

  4. Textile-Based Weft Knitted Strain Sensors: Effect of Fabric Parameters on Sensor Properties

    PubMed Central

    Atalay, Ozgur; Kennon, William Richard; Husain, Muhammad Dawood

    2013-01-01

    The design and development of textile-based strain sensors has been a focus of research and many investigators have studied this subject. This paper presents a new textile-based strain sensor design and shows the effect of base fabric parameters on its sensing properties. Sensing fabric could be used to measure articulations of the human body in the real environment. The strain sensing fabric was produced by using electronic flat-bed knitting technology; the base fabric was produced with elastomeric yarns in an interlock arrangement and a conductive yarn was embedded in this substrate to create a series of single loop structures. Experimental results show that there is a strong relationship between base fabric parameters and sensor properties. PMID:23966199

  5. Potentiometric surface map of the Floridan Aquifer in the St Johns River Water Management District and vicinity, Florida, September, 1977

    USGS Publications Warehouse

    Watkins, F.A.; Laughlin, C.P.; Hayes, E.C.

    1977-01-01

    This map presents the potentiometric surface of the Floridan aquifer in the St. Johns River Water Management District and vicinity for September 1977. The Floridan aquifer is the principal source of potable water in the area. Water-level measurements were made on approximately 900 wells and springs. The potentiometric surface is shown by 5-foot contours except in the Fernandina Beach area where 10- and 20-foot contours are used to show the deep cone of depression. This is the first map covering the entire St. Johns River Water Management District and vicinity for September, a high water-level period. The potentiometric surface ranged from 130 feet above mean sea level in Polk County to 131 feet below sea level in Nassau County. (Woodard-USGS)

  6. Creating a monthly time series of the potentiometric surface in the Upper Floridan aquifer, Northern Tampa Bay area, Florida, January 2000-December 2009

    USGS Publications Warehouse

    Lee, Terrie M.; Fouad, Geoffrey G.

    2014-01-01

    In Florida’s karst terrain, where groundwater and surface waters interact, a mapping time series of the potentiometric surface in the Upper Floridan aquifer offers a versatile metric for assessing the hydrologic condition of both the aquifer and overlying streams and wetlands. Long-term groundwater monitoring data were used to generate a monthly time series of potentiometric surfaces in the Upper Floridan aquifer over a 573-square-mile area of west-central Florida between January 2000 and December 2009. Recorded groundwater elevations were collated for 260 groundwater monitoring wells in the Northern Tampa Bay area, and a continuous time series of daily observations was created for 197 of the wells by estimating missing daily values through regression relations with other monitoring wells. Kriging was used to interpolate the monthly average potentiometric-surface elevation in the Upper Floridan aquifer over a decade. The mapping time series gives spatial and temporal coherence to groundwater monitoring data collected continuously over the decade by three different organizations, but at various frequencies. Further, the mapping time series describes the potentiometric surface beneath parts of six regionally important stream watersheds and 11 municipal well fields that collectively withdraw about 90 million gallons per day from the Upper Floridan aquifer. Monthly semivariogram models were developed using monthly average groundwater levels at wells. Kriging was used to interpolate the monthly average potentiometric-surface elevations and to quantify the uncertainty in the interpolated elevations. Drawdown of the potentiometric surface within well fields was likely the cause of a characteristic decrease and then increase in the observed semivariance with increasing lag distance. This characteristic made use of the hole effect model appropriate for describing the monthly semivariograms and the interpolated surfaces. Spatial variance reflected in the monthly

  7. Aptamer-based SERRS Sensor for Thrombin Detection

    PubMed Central

    Cho, Hansang; Baker, Brian R.; Wachsmann-Hogiu, Sebastian; Pagba, Cynthia V.; Laurence, Ted A.; Lane, Stephen M.; Lee, Luke P.; Tok, Jeffrey B.-H.

    2012-01-01

    We describe an aptamer-based Surface Enhanced Resonance Raman Scattering (SERRS) sensor with high sensitivity, specificity, and stability for the detection of a coagulation protein, human α-thrombin. The sensor achieves high sensitivity and a limit of detection of 100 pM by monitoring the SERRS signal change upon the single step of thrombin binding to immobilized thrombin binding aptamer. The selectivity of the sensor is demonstrated by the specific discrimination of thrombin from other protein analytes. The specific recognition and binding of thrombin by the thrombin binding aptamer is essential to the mechanism of the aptamer-based sensor, as shown through measurements using negative control oligonucleotides. In addition, the sensor can detect 1 nM thrombin in the presence of complex biofluids, such as 10% fetal calf serum, demonstrating that the immobilized, 5'-capped, 3'-capped aptamer is sufficiently robust for clinical diagnostic applications. Furthermore, the proposed sensor may be implemented for multiplexed detection using different aptamer-Raman probe complexes. PMID:19367849

  8. Direct evidence of ionic fluxes across ion-selective membranes: a scanning electrochemical microscopic and potentiometric study.

    PubMed

    Gyurcsányi, R E; Pergel, E; Nagy, R; Kapui, I; Lan, B T; Tóth, K; Bitter, I; Lindner, E

    2001-05-01

    Scanning electrochemical microscopy (SECM) supplemented with potentiometric measurements was used to follow the time-dependent buildup of a steady-state diffusion layer at the aqueous-phase boundary of lead ion-selective electrodes (ISEs). Differential pulse voltammetry is adapted to SECM for probing the local concentration profiles at the sample side of solvent polymeric membranes. Major factors affecting the membrane transport-related surface concentrations were identified from SECM data and the potentiometric transients obtained under different experimental conditions (inner filling solution composition, membrane thickness, surface pretreatment). The amperometrically determined surface concentrations correlated well with the lower detection limits of the lead ion-selective electrodes.

  9. Potentiometric Surfaces in the Springfield Plateau and Ozark Aquifers of Northwestern Arkansas, Southeastern Kansas, Southwestern Missouri, and Northeastern Oklahoma, 2006

    USGS Publications Warehouse

    Gillip, Jonathan A.; Czarnecki, John B.; Mugel, Douglas N.

    2008-01-01

    generally flows to the west in the study area, and to surface features (lakes, rivers, and springs) particularly in the south and east of the study area where the Springfield Plateau aquifer is closest to land surface. The potentiometric-surface map of the Ozark aquifer indicates a maximum measured water-level altitude of 1,303 feet in the study area at a well in Washington County, Arkansas, and a minimum measured water-level altitude of 390 feet in Ottawa County, Oklahoma. The water in the Ozark aquifer generally flows to the northwest in the northern part of the study area and to the west in the remaining study area. Cones of depression occur in Barry, Barton, Cedar, Jasper, Lawrence, McDonald, Newton, and Vernon Counties in Missouri, Cherokee and Crawford Counties in Kansas, and Craig and Ottawa Counties in Oklahoma. These cones of depression are associated with municipal supply wells. The flow directions, based on both potentiometric-surface maps, generally agree with flow directions indicated by previous studies.

  10. Novel LTCC-potentiometric microfluidic device for biparametric analysis of organic compounds carrying plastic antibodies as ionophores: application to sulfamethoxazole and trimethoprim.

    PubMed

    Almeida, S A A; Arasa, E; Puyol, M; Martinez-Cisneros, C S; Alonso-Chamarro, J; Montenegro, M C B S M; Sales, M G F

    2011-12-15

    Monitoring organic environmental contaminants is of crucial importance to ensure public health. This requires simple, portable and robust devices to carry out on-site analysis. For this purpose, a low-temperature co-fired ceramics (LTCC) microfluidic potentiometric device (LTCC/μPOT) was developed for the first time for an organic compound: sulfamethoxazole (SMX). Sensory materials relied on newly designed plastic antibodies. Sol-gel, self-assembling monolayer and molecular-imprinting techniques were merged for this purpose. Silica beads were amine-modified and linked to SMX via glutaraldehyde modification. Condensation polymerization was conducted around SMX to fill the vacant spaces. SMX was removed after, leaving behind imprinted sites of complementary shape. The obtained particles were used as ionophores in plasticized PVC membranes. The most suitable membrane composition was selected in steady-state assays. Its suitability to flow analysis was verified in flow-injection studies with regular tubular electrodes. The LTCC/μPOT device integrated a bidimensional mixer, an embedded reference electrode based on Ag/AgCl and an Ag-based contact screen-printed under a micromachined cavity of 600 μm depth. The sensing membranes were deposited over this contact and acted as indicating electrodes. Under optimum conditions, the SMX sensor displayed slopes of about -58.7 mV/decade in a range from 12.7 to 250 μg/mL, providing a detection limit of 3.85 μg/mL and a sampling throughput of 36 samples/h with a reagent consumption of 3.3 mL per sample. The system was adjusted later to multiple analyte detection by including a second potentiometric cell on the LTCC/μPOT device. No additional reference electrode was required. This concept was applied to Trimethoprim (TMP), always administered concomitantly with sulphonamide drugs, and tested in fish-farming waters. The biparametric microanalyzer displayed Nernstian behaviour, with average slopes -54.7 (SMX) and +57.8 (TMP) m

  11. Inertial Sensor-Based Gait Recognition: A Review

    PubMed Central

    Sprager, Sebastijan; Juric, Matjaz B.

    2015-01-01

    With the recent development of microelectromechanical systems (MEMS), inertial sensors have become widely used in the research of wearable gait analysis due to several factors, such as being easy-to-use and low-cost. Considering the fact that each individual has a unique way of walking, inertial sensors can be applied to the problem of gait recognition where assessed gait can be interpreted as a biometric trait. Thus, inertial sensor-based gait recognition has a great potential to play an important role in many security-related applications. Since inertial sensors are included in smart devices that are nowadays present at every step, inertial sensor-based gait recognition has become very attractive and emerging field of research that has provided many interesting discoveries recently. This paper provides a thorough and systematic review of current state-of-the-art in this field of research. Review procedure has revealed that the latest advanced inertial sensor-based gait recognition approaches are able to sufficiently recognise the users when relying on inertial data obtained during gait by single commercially available smart device in controlled circumstances, including fixed placement and small variations in gait. Furthermore, these approaches have also revealed considerable breakthrough by realistic use in uncontrolled circumstances, showing great potential for their further development and wide applicability. PMID:26340634

  12. Determination of quaternary ammonium compounds by potentiometric titration with an ionic surfactant electrode: single-laboratory validation.

    PubMed

    Price, Randi; Wan, Ping

    2010-01-01

    A potentiometric titration for determining the quaternary ammonium compounds (QAC) commonly found in antimicrobial products was validated by a single laboratory. Traditionally, QACs were determined by using a biphasic (chloroform and water) manual titration procedure. Because of safety considerations regarding chloroform, as well as the subjectivity of color indicator-based manual titration determinations, an automatic potentiometric titration procedure was tested with quaternary nitrogen product formulations. By using the Metrohm Titrando system coupled with an ionic surfactant electrode and an Ag/AgCl reference electrode, titrations were performed with various QAC-containing formulation products/matrixes; a standard sodium lauryl sulfate solution was used as the titrant. Results for the products tested are sufficiently reproducible and accurate for the purpose of regulatory product enforcement. The robustness of the method was measured by varying pH levels, as well as by comparing buffered versus unbuffered titration systems. A quantitation range of 1-1000 ppm quaternary nitrogen was established. Eight commercially available antimicrobial products covering a variety of matrixes were assayed; the results obtained were comparable to those obtained by the manual titration method. Recoveries of 94 to 104% were obtained for spiked samples.

  13. Composite-cavity-based Fabry-Perot interferometric strain sensors.

    PubMed

    Zhang, Jianzhong; Peng, G D; Yuan, Libo; Sun, Weimin

    2007-07-01

    A composite-cavity-based Fabry-Perot interferometric strain sensor system is proposed to gain the minimum cross sensitivity to temperature and a high multiplexing capability at the same time. The interrogation of the sensor system is based on a white-light interferometric technology, and the demodulation is achieved by analyzing the coherence spectra. A demonstration system with two sensors is presented and tested.

  14. Semi-automated potentiometric titration method for uranium characterization.

    PubMed

    Cristiano, B F G; Delgado, J U; da Silva, J W S; de Barros, P D; de Araújo, R M S; Lopes, R T

    2012-07-01

    The manual version of the potentiometric titration method has been used for certification and characterization of uranium compounds. In order to reduce the analysis time and the influence of the analyst, a semi-automatic version of the method was developed in the Brazilian Nuclear Energy Commission. The method was applied with traceability assured by using a potassium dichromate primary standard. The combined standard uncertainty in determining the total concentration of uranium was around 0.01%, which is suitable for uranium characterization. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Chemical Sensors Based on Metal Oxide Nanostructures

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Evans, Laura J.; VanderWal, Randy L.; Berger, Gordon M.; Kulis, Mike J.; Liu, Chung-Chiun

    2006-01-01

    This paper is an overview of sensor development based on metal oxide nanostructures. While nanostructures such as nanorods show significan t potential as enabling materials for chemical sensors, a number of s ignificant technical challenges remain. The major issues addressed in this work revolve around the ability to make workable sensors. This paper discusses efforts to address three technical barriers related t o the application of nanostructures into sensor systems: 1) Improving contact of the nanostructured materials with electrodes in a microse nsor structure; 2) Controling nanostructure crystallinity to allow co ntrol of the detection mechanism; and 3) Widening the range of gases that can be detected by using different nanostructured materials. It is concluded that while this work demonstrates useful tools for furt her development, these are just the beginning steps towards realizati on of repeatable, controlled sensor systems using oxide based nanostr uctures.

  16. Wearable PPG sensor based alertness scoring system.

    PubMed

    Dey, Jishnu; Bhowmik, Tanmoy; Sahoo, Saswata; Tiwari, Vijay Narayan

    2017-07-01

    Quantifying mental alertness in today's world is important as it enables the person to adopt lifestyle changes for better work efficiency. Miniaturized sensors in wearable devices have facilitated detection/monitoring of mental alertness. Photoplethysmography (PPG) sensors through Heart Rate Variability (HRV) offer one such opportunity by providing information about one's daily alertness levels without requiring any manual interference from the user. In this paper, a smartwatch based alertness estimation system is proposed. Data collected from PPG sensor of smartwatch is processed and fed to machine learning based model to get a continuous alertness score. Utility functions are designed based on statistical analysis to give a quality score on different stages of alertness such as awake, long sleep and short duration power nap. An intelligent data collection approach is proposed in collaboration with the motion sensor in the smartwatch to reduce battery drainage. Overall, our proposed wearable based system provides a detailed analysis of alertness over a period in a systematic and optimized manner. We were able to achieve an accuracy of 80.1% for sleep/awake classification along with alertness score. This opens up the possibility for quantifying alertness levels using a single PPG sensor for better management of health related activities including sleep.

  17. Building SDN-Based Agricultural Vehicular Sensor Networks Based on Extended Open vSwitch

    PubMed Central

    Huang, Tao; Yan, Siyu; Yang, Fan; Pan, Tian; Liu, Jiang

    2016-01-01

    Software-defined vehicular sensor networks in agriculture, such as autonomous vehicle navigation based on wireless multi-sensor networks, can lead to more efficient precision agriculture. In SDN-based vehicle sensor networks, the data plane is simplified and becomes more efficient by introducing a centralized controller. However, in a wireless environment, the main controller node may leave the sensor network due to the dynamic topology change or the unstable wireless signal, leaving the rest of network devices without control, e.g., a sensor node as a switch may forward packets according to stale rules until the controller updates the flow table entries. To solve this problem, this paper proposes a novel SDN-based vehicular sensor networks architecture which can minimize the performance penalty of controller connection loss. We achieve this by designing a connection state detection and self-learning mechanism. We build prototypes based on extended Open vSwitch and Ryu. The experimental results show that the recovery time from controller connection loss is under 100 ms and it keeps rule updating in real time with a stable throughput. This architecture enhances the survivability and stability of SDN-based vehicular sensor networks in precision agriculture. PMID:26797616

  18. Building SDN-Based Agricultural Vehicular Sensor Networks Based on Extended Open vSwitch.

    PubMed

    Huang, Tao; Yan, Siyu; Yang, Fan; Pan, Tian; Liu, Jiang

    2016-01-19

    Software-defined vehicular sensor networks in agriculture, such as autonomous vehicle navigation based on wireless multi-sensor networks, can lead to more efficient precision agriculture. In SDN-based vehicle sensor networks, the data plane is simplified and becomes more efficient by introducing a centralized controller. However, in a wireless environment, the main controller node may leave the sensor network due to the dynamic topology change or the unstable wireless signal, leaving the rest of network devices without control, e.g., a sensor node as a switch may forward packets according to stale rules until the controller updates the flow table entries. To solve this problem, this paper proposes a novel SDN-based vehicular sensor networks architecture which can minimize the performance penalty of controller connection loss. We achieve this by designing a connection state detection and self-learning mechanism. We build prototypes based on extended Open vSwitch and Ryu. The experimental results show that the recovery time from controller connection loss is under 100 ms and it keeps rule updating in real time with a stable throughput. This architecture enhances the survivability and stability of SDN-based vehicular sensor networks in precision agriculture.

  19. Open ISEmeter: An open hardware high-impedance interface for potentiometric detection.

    PubMed

    Salvador, C; Mesa, M S; Durán, E; Alvarez, J L; Carbajo, J; Mozo, J D

    2016-05-01

    In this work, a new open hardware interface based on Arduino to read electromotive force (emf) from potentiometric detectors is presented. The interface has been fully designed with the open code philosophy and all documentation will be accessible on web. The paper describes a comprehensive project including the electronic design, the firmware loaded on Arduino, and the Java-coded graphical user interface to load data in a computer (PC or Mac) for processing. The prototype was tested by measuring the calibration curve of a detector. As detection element, an active poly(vinyl chloride)-based membrane was used, doped with cetyltrimethylammonium dodecylsulphate (CTA(+)-DS(-)). The experimental measures of emf indicate Nernstian behaviour with the CTA(+) content of test solutions, as it was described in the literature, proving the validity of the developed prototype. A comparative analysis of performance was made by using the same chemical detector but changing the measurement instrumentation.

  20. Disposable screen-printed sensors for determination of duloxetine hydrochloride

    PubMed Central

    2012-01-01

    A screen-printed disposable electrode system for the determination of duloxetine hydrochloride (DL) was developed using screen-printing technology. Homemade printing has been characterized and optimized on the basis of effects of the modifier and plasticizers. The fabricated bi-electrode potentiometric strip containing both working and reference electrodes was used as duloxetine hydrochloride sensor. The proposed sensors worked satisfactorily in the concentration range from 1.0 × 10-6-1.0 × 10-2 mol L-1 with detection limit reaching 5.0 × 10-7 mol L-1 and adequate shelf life of 6 months. The method is accurate, precise and economical. The proposed method has been applied successfully for the analysis of the drug in pure and in its dosage forms. In this method, there is no interference from any common pharmaceutical additives and diluents. Results of the analysis were validated statistically by recovery studies. PMID:22264225

  1. Toward sensor-based context aware systems.

    PubMed

    Sakurai, Yoshitaka; Takada, Kouhei; Anisetti, Marco; Bellandi, Valerio; Ceravolo, Paolo; Damiani, Ernesto; Tsuruta, Setsuo

    2012-01-01

    This paper proposes a methodology for sensor data interpretation that can combine sensor outputs with contexts represented as sets of annotated business rules. Sensor readings are interpreted to generate events labeled with the appropriate type and level of uncertainty. Then, the appropriate context is selected. Reconciliation of different uncertainty types is achieved by a simple technique that moves uncertainty from events to business rules by generating combs of standard Boolean predicates. Finally, context rules are evaluated together with the events to take a decision. The feasibility of our idea is demonstrated via a case study where a context-reasoning engine has been connected to simulated heartbeat sensors using prerecorded experimental data. We use sensor outputs to identify the proper context of operation of a system and trigger decision-making based on context information.

  2. Multi-parametric polymer-based potentiometric analytical microsystem for future manned space missions.

    PubMed

    Calvo-López, Antonio; Puyol, Mar; Casalta, Joan Manel; Alonso-Chamarro, Julián

    2017-12-01

    The construction and evaluation of a Cyclic Olefin Copolymer (COC)-based continuous flow potentiometric microanalyzer to simultaneously monitor potassium, chloride and nitrate ions in samples from an on-board water recycling process expected to be installed in future manned space missions is presented. The main goals accomplished in this work address the specific required characteristics for a miniaturized on-line monitoring system to control water quality in such missions. To begin with, the integration of three ion-selective electrodes (ISEs) and a reference electrode in a compact microfluidic platform that incorporates a simple automatic autocalibration process allows obtaining information about the concentration of the three ions with optimal analytical response characteristics, but moreover with low reagents consumption and therefore with few waste generation, which is critical for this specific application. By a simple signal processing (signal removal) the chloride ion interference on the nitrate electrode response can be eliminated. Furthermore, all fluidics management is performed by computer-controlled microvalves and micropumps, so no manual intervention of the crew is necessary. The analytical features provided by the microsystem after the optimization process were a linear range from 6.3 to 630 mg L -1 and a detection limit of 0.51 mg L -1 for the potassium electrode, a linear range from 10 to 1000 mg L -1 and a detection limit of 1.58 mg L -1 for the chloride electrode and a linear range from 10 to 1000 mg L -1 and a detection limit of 3.37 mg L -1 for the nitrate electrode with a reproducibility (RSD) of 4%, 2% and 3% respectively. Sample throughput was 12 h -1 with a reagent consumptions lower than 2 mL per analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Potentiometric surface of the upper Floridan Aquifer in the St. Johns Water Management District and vicinity, Florida, May 1984

    USGS Publications Warehouse

    Schiner, George R.; Hayes, Eugene C.

    1984-01-01

    This map shows the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1984. The Upper Floridan aquifer is the principal source of potable water in the area. Water-level measurements were made on approximately 1,000 wells and on several springs. The potentiometric surface is shown mostly by 5-foot contour intervals. In the Fernandina Beach area a 40-foot interval is used to show a deep cone of depression. The potentiometric surface ranged from 126 feet above sea level in Polk County to 84 feet below sea level in Nassau County. Water levels in key wells were mostly above, or less frequently, slightly below averages for May in response to diverse area rainfall patterns. Most levels in the district were about the same, or more commonly, 1 to 2 feet lower than May 1983 levels. (USGS)

  4. Fluorographene based Ultrasensitive Ammonia Sensor

    PubMed Central

    Tadi, Kiran Kumar; Pal, Shubhadeep; Narayanan, Tharangattu N.

    2016-01-01

    Single molecule detection using graphene can be brought by tuning the interactions via specific dopants. Electrostatic interaction between the most electronegative element fluorine (F) and hydrogen (H) is one of the strong interactions in hydrogen bonding, and here we report the selective binding of ammonia/ammonium with F in fluorographene (FG) resulting to a change in the impedance of the system. Very low limit of detection value of ~0.44 pM with linearity over wide range of concentrations (1 pM–0.1 μM) is achieved using the FG based impedance sensor, andthisscreen printed FG sensor works in both ionized (ammonium) and un-ionized ammonia sensing platforms. The interaction energies of FG and NH3/NH4+ are evaluated using density functional theory calculations and the interactions are mapped. Here FGs with two different amounts of fluorinecontents −~5 atomic% (C39H16F2) and ~24 atomic% (C39H16F12) - are theoretically and experimentally studied for selective, high sensitive and ultra-low level detection of ammonia. Fast responding, high sensitive, large area patternable FG based sensor platform demonstrated here can open new avenues for the development of point-of-care devices and clinical sensors. PMID:27142522

  5. Implantable fluorescence-based glucose sensor development

    NASA Astrophysics Data System (ADS)

    Ibey, Bennett L.; Yadavalli, Vamsi K.; Thomas, Hope R.; Rounds, Rebecca M.; Pishko, Michael V.; Cote, Gerard L.

    2005-03-01

    An implantable sensor is being created that allows measurement of blood glucose through fluorescent detection of an embedded chemical assay. The sensor is based on the competitive binding reaction between the protein Concanavalin A and various saccharide molecules, specifically a glycodendrimer and glucose. Previous studies have shown the ability of an embedded chemical assay using Con A and dextran with shorter wavelength dyes to both sense changes in glucose and generate sufficient fluorescent emission to pass through the dermal tissue. However, due to the chemical constituents of the assay, multivalent binding was evident resulting in poor spectral change due to glucose within the biological range. Use of a glycodendrimer and longer wavelength dyes has improved the sensor"s spectral change due to glucose and the overall signal to noise ratio of the sensor. In this work, a description of this sensor and the results obtained from it will be presented showing a large dynamic range of fluorescence with glucose.

  6. Latest developments for low-power infrared laser-based trace gas sensors for sensor networks

    NASA Astrophysics Data System (ADS)

    So, Stephen; Thomazy, David; Wang, Wen; Marchat, Oscar; Wysocki, Gerard

    2011-09-01

    Academic and industrial researchers require ultra-low power, compact laser based trace-gas sensor systems for the most demanding environmental and space-borne applications. Here the latest results from research projects addressing these applications will be discussed: 1) an ultra-compact CO2 sensor based on a continuous wave quantum cascade laser, 2) an ultra-sensitive Faraday rotation spectrometer for O2 detection, 3) a fully ruggedized compact and low-power laser spectrometer, and 4) a novel non-paraxial nonthin multipass cell. Preliminary tests and projection for performance of future sensors based on this technology is presented.

  7. Radar based autonomous sensor module

    NASA Astrophysics Data System (ADS)

    Styles, Tim

    2016-10-01

    Most surveillance systems combine camera sensors with other detection sensors that trigger an alert to a human operator when an object is detected. The detection sensors typically require careful installation and configuration for each application and there is a significant burden on the operator to react to each alert by viewing camera video feeds. A demonstration system known as Sensing for Asset Protection with Integrated Electronic Networked Technology (SAPIENT) has been developed to address these issues using Autonomous Sensor Modules (ASM) and a central High Level Decision Making Module (HLDMM) that can fuse the detections from multiple sensors. This paper describes the 24 GHz radar based ASM, which provides an all-weather, low power and license exempt solution to the problem of wide area surveillance. The radar module autonomously configures itself in response to tasks provided by the HLDMM, steering the transmit beam and setting range resolution and power levels for optimum performance. The results show the detection and classification performance for pedestrians and vehicles in an area of interest, which can be modified by the HLDMM without physical adjustment. The module uses range-Doppler processing for reliable detection of moving objects and combines Radar Cross Section and micro-Doppler characteristics for object classification. Objects are classified as pedestrian or vehicle, with vehicle sub classes based on size. Detections are reported only if the object is detected in a task coverage area and it is classified as an object of interest. The system was shown in a perimeter protection scenario using multiple radar ASMs, laser scanners, thermal cameras and visible band cameras. This combination of sensors enabled the HLDMM to generate reliable alerts with improved discrimination of objects and behaviours of interest.

  8. Simulation of an enzyme-based glucose sensor

    NASA Astrophysics Data System (ADS)

    Sha, Xianzheng; Jablecki, Michael; Gough, David A.

    2001-09-01

    An important biosensor application is the continuous monitoring blood or tissue fluid glucose concentration in people with diabetes. Our research focuses on the development of a glucose sensor based on potentiostatic oxygen electrodes and immobilized glucose oxidase for long- term application as an implant in tissues. As the sensor signal depends on many design variables, a trial-and-error approach to sensor optimization can be time-consuming. Here, the properties of an implantable glucose sensor are optimized by a systematic computational simulation approach.

  9. Development of GaN-based microchemical sensor nodes

    NASA Technical Reports Server (NTRS)

    Prokopuk, Nicholas; Son, Kyung-Ah; George, Thomas; Moon, Jeong S.

    2005-01-01

    Sensors based III-N technology are gaining significant interest due to their potential for monolithic integration of RF transceivers and light sources and the capability of high temperature operations. We are developing a GaN-based micro chemical sensor node for remote detection of chemical toxins, and present electrical responses of AlGaN/GaN HEMT (High Electron Mobility Transistor) sensors to chemical toxins as well as other common gases.

  10. Potentiometric surface of the upper Floridan aquifer, west-central Florida, May 2011

    USGS Publications Warehouse

    Ortiz, Anita G.

    2011-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2011. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 45.74 inches for west-central Florida (from June 2010 through May 2011) was 6.85 inches below the historical cumulative average of 52.59 inches (Southwest Florida Water Management District, 2011). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September from 1975 through 2010. Water-level data are collected in May and September each year to

  11. Potentiometric Surface of the Upper Floridan Aquifer, West-central Florida, May 2010

    USGS Publications Warehouse

    Ortiz, A.G.

    2010-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 55.21 inches for west-central Florida (from June 2009 through May 2010) was 2.55 inches above the historical cumulative average of 52.66 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the

  12. Optical Fiber Sensors Based on Fiber Ring Laser Demodulation Technology.

    PubMed

    Xie, Wen-Ge; Zhang, Ya-Nan; Wang, Peng-Zhao; Wang, Jian-Zhang

    2018-02-08

    A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory background of the sensors has been discussed. Secondly, four different types of sensors are described and compared, which includes Mach-Zehnder interferometer (MZI) typed sensors, Fabry-Perot interferometer (FPI) typed sensors, Sagnac typed sensors, and fiber Bragg grating (FBG) typed sensors. Typical studies and main properties of each type of sensors are presented. Thirdly, a comparison of different types of sensors are made. Finally, the existing problems and future research directions are pointed out and analyzed.

  13. Chemical Sensors Based on Cyclodextrin Derivatives.

    PubMed

    Ogoshi, Tomoki; Harada, Akira

    2008-08-25

    This review focuses on chemical sensors based on cyclodextrin (CD) derivatives. This has been a field of classical interest, and is now of current interest for numerous scientists. First, typical chemical sensors using chromophore appended CDs are mentioned. Various "turn-off" and "turn-on" fluorescent chemical sensors, in which fluorescence intensity was decreased or increased by complexation with guest molecules, respectively, were synthesized. Dye modified CDs and photoactive metal ion-ligand complex appended CDs, metallocyclodextrins, were also applied for chemical sensors. Furthermore, recent novel approaches to chemical sensing systems using supramolecular structures such as CD dimers, trimers and cooperative binding systems of CDs with the other macrocycle [2]rotaxane and supramolecular polymers consisting of CD units are mentioned. New chemical sensors using hybrids of CDs with p-conjugated polymers, peptides, DNA, nanocarbons and nanoparticles are also described in this review.

  14. Silver(I) ion-selective membrane based on Schiff base-p-tert-butylcalix[4]arene.

    PubMed

    Mahajan, R K; Kumar, M; Sharma, V; Kaur, I

    2001-04-01

    A PVC membrane electrode for silver(I) ion based on Schiff base-p-tert-butylcalix[4]arene is reported. The electrode works well over a wide range of concentration (1.0 x 10(-5)-1.0 x 10(-1) mol dm-3) with a Nernstian slope of 59.7 mV per decade. The electrode shows a fast response time of 20 s and operates in the pH range 1.0-5.6. The sensor can be used for more than 6 months without any divergence in the potential. The selectivity of the electrode was studied and it was found that the electrode exhibits good selectivity for silver ion over some alkali, alkaline earth and transition metal ions. The silver ion-selective electrode was used as an indicator electrode for the potentiometric titration of silver ion in solution using a standard solution of sodium chloride; a sharp potential change occurs at the end-point. The applicability of the sensor to silver(I) ion measurement in water samples spiked with silver nitrate is illustrated.

  15. Computer analysis of potentiometric data of complexes formation in the solution

    NASA Astrophysics Data System (ADS)

    Jastrzab, Renata; Kaczmarek, Małgorzata T.; Tylkowski, Bartosz; Odani, Akira

    2018-02-01

    The determination of equilibrium constants is an important process for many branches of chemistry. In this review we provide the readers with a discussion on computer methods which have been applied for elaboration of potentiometric experimental data generated during complexes formation in solution. The review describes both: general basis of modeling tools and examples of the use of calculated stability constants.

  16. Electrochemical DNA Hybridization Sensors Based on Conducting Polymers

    PubMed Central

    Rahman, Md. Mahbubur; Li, Xiao-Bo; Lopa, Nasrin Siraj; Ahn, Sang Jung; Lee, Jae-Joon

    2015-01-01

    Conducting polymers (CPs) are a group of polymeric materials that have attracted considerable attention because of their unique electronic, chemical, and biochemical properties. This is reflected in their use in a wide range of potential applications, including light-emitting diodes, anti-static coating, electrochromic materials, solar cells, chemical sensors, biosensors, and drug-release systems. Electrochemical DNA sensors based on CPs can be used in numerous areas related to human health. This review summarizes the recent progress made in the development and use of CP-based electrochemical DNA hybridization sensors. We discuss the distinct properties of CPs with respect to their use in the immobilization of probe DNA on electrode surfaces, and we describe the immobilization techniques used for developing DNA hybridization sensors together with the various transduction methods employed. In the concluding part of this review, we present some of the challenges faced in the use of CP-based DNA hybridization sensors, as well as a future perspective. PMID:25664436

  17. Electrochemical DNA hybridization sensors based on conducting polymers.

    PubMed

    Rahman, Md Mahbubur; Li, Xiao-Bo; Lopa, Nasrin Siraj; Ahn, Sang Jung; Lee, Jae-Joon

    2015-02-05

    Conducting polymers (CPs) are a group of polymeric materials that have attracted considerable attention because of their unique electronic, chemical, and biochemical properties. This is reflected in their use in a wide range of potential applications, including light-emitting diodes, anti-static coating, electrochromic materials, solar cells, chemical sensors, biosensors, and drug-release systems. Electrochemical DNA sensors based on CPs can be used in numerous areas related to human health. This review summarizes the recent progress made in the development and use of CP-based electrochemical DNA hybridization sensors. We discuss the distinct properties of CPs with respect to their use in the immobilization of probe DNA on electrode surfaces, and we describe the immobilization techniques used for developing DNA hybridization sensors together with the various transduction methods employed. In the concluding part of this review, we present some of the challenges faced in the use of CP-based DNA hybridization sensors, as well as a future perspective.

  18. Regional potentiometric surface of the Ozark aquifer in Arkansas, Kansas, Missouri, and Oklahoma, November 2014–January 2015

    USGS Publications Warehouse

    Nottmeier, Anna M.

    2015-12-21

    The Ozark aquifer, within the Ozark Plateaus aquifer system (herein referred to as the “Ozark system”), is the primary groundwater source in the Ozark Plateaus physiographic province (herein referred to as the “Ozark Plateaus”) of Arkansas, Kansas, Missouri, and Oklahoma. Groundwater from the Ozark system has historically been an important part of the water resource base, and groundwater availability is a concern in some areas; dependency on the Ozark aquifer as a water supply has caused evolving, localized issues. The construction of a regional potentiometric-surface map of the Ozark aquifer is needed to aid assessment of current and future groundwater use and availability. The regional potentiometric-surface mapping is part of the U.S. Geological Survey (USGS) Groundwater Resources Program initiative (http://water.usgs.gov/ogw/gwrp/activities/regional.html) and the Ozark system groundwater availability project (http://ar.water.usgs.gov/ozarks), which seeks to quantify current groundwater resources, evaluate changes in these resources over time, and provide the information needed to simulate system response to future human-related and environmental stresses.The Ozark groundwater availability project objectives include assessing (1) growing demands for groundwater and associated declines in groundwater levels as agricultural, industrial, and public supply pumping increases to address needs; (2) regional climate variability and pumping effects on groundwater and surface-water flow paths; (3) effects of a gradual shift to a greater surface-water dependence in some areas; and (4) shale-gas production requiring groundwater and surface water for hydraulic fracturing. Data compiled and used to construct the regional Ozark aquifer potentiometric surface will aid in the assessment of those objectives.

  19. Optical Fiber Sensors Based on Fiber Ring Laser Demodulation Technology

    PubMed Central

    Xie, Wen-Ge; Wang, Peng-Zhao; Wang, Jian-Zhang

    2018-01-01

    A review for optical fiber sensors based on fiber ring laser (FRL) demodulation technology is presented. The review focuses on the principles, main structures, and the sensing performances of different kinds of optical fiber sensors based on FRLs. First of all, the theory background of the sensors has been discussed. Secondly, four different types of sensors are described and compared, which includes Mach–Zehnder interferometer (MZI) typed sensors, Fabry–Perot interferometer (FPI) typed sensors, Sagnac typed sensors, and fiber Bragg grating (FBG) typed sensors. Typical studies and main properties of each type of sensors are presented. Thirdly, a comparison of different types of sensors are made. Finally, the existing problems and future research directions are pointed out and analyzed. PMID:29419745

  20. Fluorescent sensors based on boronic acids

    NASA Astrophysics Data System (ADS)

    Cooper, Christopher R.; James, Tony D.

    1999-05-01

    Sensor systems have long been needed for detecting the presence in solution of certain chemically or biologically important species. Sensors are used in a wide range of applications from simple litmus paper that shows a single color change in acidic or basic environments to complex biological assays that use enzymes, antibodies and antigens to display binding events. With this work the use of boronic acids in the design and synthesis of sensors for saccharides (diols) will be presented. The fluorescent sensory systems rely on photoinduced electron transfer (PET) to modulate the observed fluorescence. When saccharides form cyclic boronate esters with boronic acids, the Lewis acidity of the boronic acid is enhanced and therefore the Lewis acid-base interaction between the boronic acid and a neighboring amine is strengthened. The strength of this acid-base interaction modulates the PET from the amine (acting as a quencher) to anthracene (acting as a fluorophore). These compounds show increased fluorescence at neutral pH through suppression of the PET from nitrogen to anthracene on saccharide binding. The general strategy for the development of saccharide selective systems will be discussed. The potential of the boronic acid based systems will be illustrated using the development of glucose and glucosamine selective fluorescent sensors as examples.

  1. Highly Stretchable Potentiometric pH Sensor Fabricated via Laser Carbonization and Machining of Carbon-Polyaniline Composite.

    PubMed

    Rahimi, Rahim; Ochoa, Manuel; Tamayol, Ali; Khalili, Shahla; Khademhosseini, Ali; Ziaie, Babak

    2017-03-15

    The development of stretchable sensors has recently attracted considerable attention. These sensors have been used in wearable and robotics applications, such as personalized health-monitoring, motion detection, and human-machine interfaces. Herein, we report on a highly stretchable electrochemical pH sensor for wearable point-of-care applications that consists of a pH-sensitive working electrode and a liquid-junction-free reference electrode, in which the stretchable conductive interconnections are fabricated by laser carbonizing and micromachining of a polyimide sheet bonded to an Ecoflex substrate. This method produces highly porous carbonized 2D serpentine traces that are subsequently permeated with polyaniline (PANI) as the conductive filler, binding material, and pH-sensitive membrane. The experimental and simulation results demonstrate that the stretchable serpentine PANI/C-PI interconnections with an optimal trace width of 0.3 mm can withstand elongations of up to 135% and are robust to more than 12 000 stretch-and-release cycles at 20% strain without noticeable change in the resistance. The pH sensor displays a linear sensitivity of -53 mV/pH (r 2 = 0.976) with stable performance in the physiological range of pH 4-10. The sensor shows excellent stability to applied longitudinal and transverse strains up to 100% in different pH buffer solutions with a minimal deviation of less than ±4 mV. The material biocompatibility is confirmed with NIH 3T3 fibroblast cells via PrestoBlue assays.

  2. Determination of arsenate and organic arsenic via potentiometric titration of its heteropoly anions.

    PubMed

    Metelka, R; Slavíková, S; Vytras, K

    2002-08-16

    Determination of arsenate based on its conversion to molybdoarsenate heteropoly anions followed by potentiometric titration is described. The titration is realized on the ion-pairing principle using cetylpyridinium chloride (or an analogous titrant containing a lipophilic cation), and is monitored by a carbon paste electrode, although other liquid-polymeric membrane-based electrodes can also be used. Calibration plots of the titrant end-point consumption versus concentration of arsenic were constructed and used to evaluate the content of arsenic in aqueous samples. The method could be applied in the analyses of samples with quite low arsenic content (amounts approximately 10 mug As in 50 cm(3) could be titrated). Organic arsenic was determined analogously after the Schöniger combustion of the sample and conversion of its arsenic to arsenate.

  3. Biological and chemical sensors based on graphene materials.

    PubMed

    Liu, Yuxin; Dong, Xiaochen; Chen, Peng

    2012-03-21

    Owing to their extraordinary electrical, chemical, optical, mechanical and structural properties, graphene and its derivatives have stimulated exploding interests in their sensor applications ever since the first isolation of free-standing graphene sheets in year 2004. This article critically and comprehensively reviews the emerging graphene-based electrochemical sensors, electronic sensors, optical sensors, and nanopore sensors for biological or chemical detection. We emphasize on the underlying detection (or signal transduction) mechanisms, the unique roles and advantages of the used graphene materials. Properties and preparations of different graphene materials, their functionalizations are also comparatively discussed in view of sensor development. Finally, the perspective and current challenges of graphene sensors are outlined (312 references).

  4. Zone-Based Routing Protocol for Wireless Sensor Networks

    PubMed Central

    Venkateswarlu Kumaramangalam, Muni; Adiyapatham, Kandasamy; Kandasamy, Chandrasekaran

    2014-01-01

    Extensive research happening across the globe witnessed the importance of Wireless Sensor Network in the present day application world. In the recent past, various routing algorithms have been proposed to elevate WSN network lifetime. Clustering mechanism is highly successful in conserving energy resources for network activities and has become promising field for researches. However, the problem of unbalanced energy consumption is still open because the cluster head activities are tightly coupled with role and location of a particular node in the network. Several unequal clustering algorithms are proposed to solve this wireless sensor network multihop hot spot problem. Current unequal clustering mechanisms consider only intra- and intercluster communication cost. Proper organization of wireless sensor network into clusters enables efficient utilization of limited resources and enhances lifetime of deployed sensor nodes. This paper considers a novel network organization scheme, energy-efficient edge-based network partitioning scheme, to organize sensor nodes into clusters of equal size. Also, it proposes a cluster-based routing algorithm, called zone-based routing protocol (ZBRP), for elevating sensor network lifetime. Experimental results show that ZBRP out-performs interims of network lifetime and energy conservation with its uniform energy consumption among the cluster heads. PMID:27437455

  5. Zone-Based Routing Protocol for Wireless Sensor Networks.

    PubMed

    Venkateswarlu Kumaramangalam, Muni; Adiyapatham, Kandasamy; Kandasamy, Chandrasekaran

    2014-01-01

    Extensive research happening across the globe witnessed the importance of Wireless Sensor Network in the present day application world. In the recent past, various routing algorithms have been proposed to elevate WSN network lifetime. Clustering mechanism is highly successful in conserving energy resources for network activities and has become promising field for researches. However, the problem of unbalanced energy consumption is still open because the cluster head activities are tightly coupled with role and location of a particular node in the network. Several unequal clustering algorithms are proposed to solve this wireless sensor network multihop hot spot problem. Current unequal clustering mechanisms consider only intra- and intercluster communication cost. Proper organization of wireless sensor network into clusters enables efficient utilization of limited resources and enhances lifetime of deployed sensor nodes. This paper considers a novel network organization scheme, energy-efficient edge-based network partitioning scheme, to organize sensor nodes into clusters of equal size. Also, it proposes a cluster-based routing algorithm, called zone-based routing protocol (ZBRP), for elevating sensor network lifetime. Experimental results show that ZBRP out-performs interims of network lifetime and energy conservation with its uniform energy consumption among the cluster heads.

  6. Open ISEmeter: An open hardware high-impedance interface for potentiometric detection

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Salvador, C.; Carbajo, J.; Mozo, J. D., E-mail: jdaniel.mozo@diq.uhu.es

    In this work, a new open hardware interface based on Arduino to read electromotive force (emf) from potentiometric detectors is presented. The interface has been fully designed with the open code philosophy and all documentation will be accessible on web. The paper describes a comprehensive project including the electronic design, the firmware loaded on Arduino, and the Java-coded graphical user interface to load data in a computer (PC or Mac) for processing. The prototype was tested by measuring the calibration curve of a detector. As detection element, an active poly(vinyl chloride)-based membrane was used, doped with cetyltrimethylammonium dodecylsulphate (CTA{sup +}-DS{supmore » −}). The experimental measures of emf indicate Nernstian behaviour with the CTA{sup +} content of test solutions, as it was described in the literature, proving the validity of the developed prototype. A comparative analysis of performance was made by using the same chemical detector but changing the measurement instrumentation.« less

  7. Characterization of cement-based materials using a reusable piezoelectric impedance-based sensor

    NASA Astrophysics Data System (ADS)

    Tawie, R.; Lee, H. K.

    2011-08-01

    This paper proposes a reusable sensor, which employs a piezoceramic (PZT) plate as an active sensing transducer, for non-destructive monitoring of cement-based materials based on the electromechanical impedance (EMI) sensing technique. The advantage of the sensor design is that the PZT can be easily removed from the set-up and re-used for repetitive tests. The applicability of the sensor was demonstrated for monitoring of the setting of cement mortar. EMI measurements were performed using an impedance analyzer and the transformation of the specimen from the plastic to solid state was monitored by automatically measuring the changes in the PZT conductance spectra with respect to curing time using the root mean square deviation (RMSD) algorithm. In another experiment, drying-induced moisture loss of a hardened mortar specimen at saturated surface dry (SSD) condition was measured, and monitored using the reusable sensor to establish a correlation between the RMSD values and moisture loss rate. The reusable sensor was also demonstrated for detecting progressive damages imparted on a mortar specimen attached with the sensor under several loading levels before allowing it to load to failure. Overall, the reusable sensor is an effective and efficient monitoring device that could possibly be used for field application in characterization of cement-based materials.

  8. Torque Sensor Based on Tunnel-Diode Oscillator

    NASA Technical Reports Server (NTRS)

    Chui, Talso; Young, Joseph

    2008-01-01

    A proposed torque sensor would be capable of operating over the temperature range from 1 to 400 K, whereas a typical commercially available torque sensor is limited to the narrower temperature range of 244 to 338 K. The design of this sensor would exploit the wide temperature range and other desirable attributes of differential transducers based on tunnel-diode oscillators as described in "Multiplexing Transducers Based on Tunnel-Diode Oscillators". The proposed torque sensor would include three flexural springs that would couple torque between a hollow outer drive shaft and a solid inner drive shaft. The torque would be deduced from the torsional relative deflection of the two shafts, which would be sensed via changes in capacitances of two capacitors defined by two electrodes attached to the inner shaft and a common middle electrode attached to the outer shaft.

  9. Potassium sodium chloride integrated microconduits in a potentiometric analytical system.

    PubMed

    Hongbo, C; Junyan, S

    1991-09-01

    The preparation and application of a K(+), Na(+) and Cl(-) integrated microconduit potentiometric analytical system with tubular ion-selective electrodes (ISEs), microvalve, chemfold, electrostatic and pulse inhibitors is described. Electrochemical characteristics of the tubular ISEs and integrated microconduit FIA-ISEs were studied. The contents of K(+), Na(+) and Cl(-) in soil, water and serum were determined with the device. The analytical results agreed well with those obtained by flame photometric and silver nitrate volumetric methods.

  10. Spectrofluorimetric and Potentiometric Determination of Acidity Constants of 4-(4'-Acetyloxy-3'-Methoxybenzylidene)-5-Oxazolone Derivatives.

    PubMed

    Taskiran, Derya Topkaya; Urut, Gulsiye Ozturk; Ayata, Sevda; Alp, Serap

    2017-03-01

    4-(4'-acetyloxy-3'-methoxybenzylidene)-5-oxazolone fluorescent molecules bearing four different aryl groups attached to the 2-position of 5-oxazolone ring have been investigated by spectrophotometric and potentiometric techniques in solution media. The acidity constants (pKa) of the fluorescent molecules were precisely determined in acetone, acetonitrile, dimethylformamide and in 1:1 mixture of toluene-isopropanol. The studied derivatives were titrated with tetrabutylammonium hydroxide and non-aqueous perchloric acid by scanning the basic and acidic region of the pH scale. A computerizable derivative method was used in order to descript precisely the end point and pKa values. The molecules investigated performed well-shaped and stoichiometric potentiometric titration curves.

  11. Optical hydrogen sensors based on metal-hydrides

    NASA Astrophysics Data System (ADS)

    Slaman, M.; Westerwaal, R.; Schreuders, H.; Dam, B.

    2012-06-01

    For many hydrogen related applications it is preferred to use optical hydrogen sensors above electrical systems. Optical sensors reduce the risk of ignition by spark formation and are less sensitive to electrical interference. Currently palladium and palladium alloys are used for most hydrogen sensors since they are well known for their hydrogen dissociation and absorption properties at relatively low temperatures. The disadvantages of palladium in sensors are the low optical response upon hydrogen loading, the cross sensitivity for oxygen and carbon, the limited detection range and the formation of micro-cracks after some hydrogen absorption/desorption cycles. In contrast to Pd, we find that the use of magnesium or rear earth bases metal-hydrides in optical hydrogen sensors allow tuning of the detection levels over a broad pressure range, while maintaining a high optical response. We demonstrate a stable detection layer for detecting hydrogen below 10% of the lower explosion limit in an oxygen rich environment. This detection layer is deposited at the bare end of a glass fiber as a micro-mirror and is covered with a thin layer of palladium. The palladium layer promotes the hydrogen uptake at room temperature and acts as a hydrogen selective membrane. To protect the sensor for a long time in air a final layer of a hydrophobic fluorine based coating is applied. Such a sensor can be used for example as safety detector in automotive applications. We find that this type of fiber optic hydrogen sensor is also suitable for hydrogen detection in liquids. As example we demonstrate a sensor for detecting a broad range of concentrations in transformer oil. Such a sensor can signal a warning when sparks inside a high voltage power transformer decompose the transformer oil over a long period.

  12. Detection of Catechol by Potentiometric-Flow Injection Analysis in the Presence of Interferents

    ERIC Educational Resources Information Center

    Lunsford, Suzanne K.; Widera, Justyna; Zhang, Hong

    2007-01-01

    This article describes an undergraduate analytical chemistry experiment developed to teach instrumental lab skills while incorporating common interferents encountered in the real-world analysis of catechol. The lab technique incorporates potentiometric-flow injection analysis on a dibenzo-18-crown-6 dual platinum electrode to detect catechol in…

  13. A Solar Position Sensor Based on Image Vision.

    PubMed

    Ruelas, Adolfo; Velázquez, Nicolás; Villa-Angulo, Carlos; Acuña, Alexis; Rosales, Pedro; Suastegui, José

    2017-07-29

    Solar collector technologies operate with better performance when the Sun beam direction is normal to the capturing surface, and for that to happen despite the relative movement of the Sun, solar tracking systems are used, therefore, there are rules and standards that need minimum accuracy for these tracking systems to be used in solar collectors' evaluation. Obtaining accuracy is not an easy job, hence in this document the design, construction and characterization of a sensor based on a visual system that finds the relative azimuth error and height of the solar surface of interest, is presented. With these characteristics, the sensor can be used as a reference in control systems and their evaluation. The proposed sensor is based on a microcontroller with a real-time clock, inertial measurement sensors, geolocation and a vision sensor, that obtains the angle of incidence from the sunrays' direction as well as the tilt and sensor position. The sensor's characterization proved how a measurement of a focus error or a Sun position can be made, with an accuracy of 0.0426° and an uncertainty of 0.986%, which can be modified to reach an accuracy under 0.01°. The validation of this sensor was determined showing the focus error on one of the best commercial solar tracking systems, a Kipp & Zonen SOLYS 2. To conclude, the solar tracking sensor based on a vision system meets the Sun detection requirements and components that meet the accuracy conditions to be used in solar tracking systems and their evaluation or, as a tracking and orientation tool, on photovoltaic installations and solar collectors.

  14. Potentiometric surface, 2013, and water-level differences, 1991-2013, of the Carrizo-Wilcox aquifer in northwest Louisiana

    USGS Publications Warehouse

    Fendick, Robert B.; Carter, Kayla

    2015-01-01

    This report presents data and maps that illustrate the potentiometric surface of the Carrizo-Wilcox aquifer during March–May 2013 and water-level differences from 1991 to 2013. The potentiometric surface map can be used for determining the direction of groundwater flow, hydraulic gradients, and effects of withdrawals on the groundwater resource. The rate of groundwater movement also can be estimated from the gradient when the hydraulic conductivity is applied. Water-level data collected for this study are stored in the USGS National Water Information System (NWIS) (http://waterdata.usgs.gov/nwis) and are on file at the USGS office in Baton Rouge, La.

  15. Portable Nanoparticle-Based Sensors for Food Safety Assessment

    PubMed Central

    Bülbül, Gonca; Hayat, Akhtar; Andreescu, Silvana

    2015-01-01

    The use of nanotechnology-derived products in the development of sensors and analytical measurement methodologies has increased significantly over the past decade. Nano-based sensing approaches include the use of nanoparticles (NPs) and nanostructures to enhance sensitivity and selectivity, design new detection schemes, improve sample preparation and increase portability. This review summarizes recent advancements in the design and development of NP-based sensors for assessing food safety. The most common types of NPs used to fabricate sensors for detection of food contaminants are discussed. Selected examples of NP-based detection schemes with colorimetric and electrochemical detection are provided with focus on sensors for the detection of chemical and biological contaminants including pesticides, heavy metals, bacterial pathogens and natural toxins. Current trends in the development of low-cost portable NP-based technology for rapid assessment of food safety as well as challenges for practical implementation and future research directions are discussed. PMID:26690169

  16. Polymer-based sensor array for phytochemical detection

    NASA Astrophysics Data System (ADS)

    Weerakoon, Kanchana A.; Hiremath, Nitilaksha; Chin, Bryan A.

    2012-05-01

    Monitoring for the appearance of volatile organic compounds emitted by plants which correspond to time of first insect attack can be used to detect the early stages of insect infestation. This paper reports a chemical sensor array consisting of polymer based chemiresistor sensors that could detect insect infestation effectively. The sensor array consists of sensors with micro electronically fabricated interdigitated electrodes, and twelve different types of electro active polymer layers. The sensor array was cheap, easy to fabricate, and could be used easily in agricultural fields. The polymer array was found to be sensitive to a variety of volatile organic compounds emitted by plants including γ-terpinene α-pinene, pcymene, farnesene, limonene and cis-hexenyl acetate. The sensor array was not only able to detect but also distinguish between these compounds. The twelve sensors produced a resistance change for each of the analytes detected, and each of these responses together produced a unique fingerprint, enabling to distinguish among these chemicals.

  17. Fully wireless pressure sensor based on endoscopy images

    NASA Astrophysics Data System (ADS)

    Maeda, Yusaku; Mori, Hirohito; Nakagawa, Tomoaki; Takao, Hidekuni

    2018-04-01

    In this paper, the result of developing a fully wireless pressure sensor based on endoscopy images for an endoscopic surgery is reported for the first time. The sensor device has structural color with a nm-scale narrow gap, and the gap is changed by air pressure. The structural color of the sensor is acquired from camera images. Pressure detection can be realized with existing endoscope configurations only. The inner air pressure of the human body should be measured under flexible-endoscope operation using the sensor. Air pressure monitoring, has two important purposes. The first is to quantitatively measure tumor size under a constant air pressure for treatment selection. The second purpose is to prevent the endangerment of a patient due to over transmission of air. The developed sensor was evaluated, and the detection principle based on only endoscopy images has been successfully demonstrated.

  18. Differential potentiometric titration: development of a methodology for determining the point of zero charge of metal (hydr)oxides by one titration curve.

    PubMed

    Bourikas, Kyriakos; Kordulis, Christos; Lycourghiotis, Alexis

    2005-06-01

    A new methodology is presented, called differential potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one potentiometric curve. By performing extensive simulations of potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+(cons,surf) versus pH potentiometric curve (H+(cons,surf): hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+(cons,surf)/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength. It was found that the aforementioned peak also appears in the high-resolution differential potentiometric curves experimentally determined for four oxides (SiO2, TiO2, gamma-Al2O3, and MgO) that are widely used in various environmental and other technological applications. The application of DPT to the above-mentioned oxides provided practically the same pzc values as the corresponding ones achieved by using four different techniques as well as the corresponding isoelectric point (iep) values determined by microelectrophoresis. Differences between the pzc and iep values determined using various techniques in the case of MgO were attributed to the increasing dissolution of this oxide as pH decreases and the adsorption of cations (Mg2+, Na+) on the MgO/electrolytic solution interface.

  19. Differential electrolytic potentiometric titration method for the determination of ciprofloxacin in drug formulations.

    PubMed

    Abulkibash, Abdalla M; Sultan, Salah M; Al-Olyan, Abeer M; Al-Ghannam, Sheikha M

    2003-10-17

    A simple and rapid differential electrolytic potentiometric titration method for the determination of ciprofloxacin was developed. The work is based on the fast complexation reaction between iron(III) and ciprofloxacin in a ratio of 1:3, respectively, in sulfuric acid media of 0.09 mol dm(-3). Among the electrodes tested silver amalgam electrodes were found to be a suitable indicating system. By applying a current density of 0.5 muA cm(-2) to these electrodes and using iron(III) solution of 0.097 mol dm(-3) as a titrant, normal titration curves were obtained. The method was successfully applied for the determination of ciprofloxacin in drug formulations as low as 4.0 ppm.

  20. BIOSENSOR FOR DIRECT DETERMINATION OF ORGANOPHOSPHATE NERVE AGENTS. 1. POTENTIOMETRIC ENZYME ELECTRODE. (R823663)

    EPA Science Inventory

    A potentiometric enzyme electrode for the direct measurement of organophosphate (OP)
    nerve agents was developed. The basic element of this enzyme electrode was a pH electrode
    modified with an immobilized organophosphorus hydrolase (OPH) layer formed by cross-linking
    OPH ...

  1. Using Custom Fiber Bragg Grating-Based Sensors to Monitor Artificial Landslides.

    PubMed

    Zhang, Qinghua; Wang, Yuan; Sun, Yangyang; Gao, Lei; Zhang, Zhenglin; Zhang, Wenyuan; Zhao, Pengchong; Yue, Yin

    2016-09-02

    Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as "hard sensors" (Sensor 1 and Sensor 2), the other two are referred to as "soft sensors" (Sensor 3 and Sensor 4). The two FBGs are fixed on each sensor rod at distances of 50 cm and 100 cm from the top of the rod (an upper FBG and a lower FBG). In the experiment presented in this paper, the sensors are installed on a slope on which an artificial landslide is generated through both machine-based and manual excavation. The fiber sensing system consists of the four custom FBG-based sensors, optical fiber, a static fiber grating demodulation instrument (SM125), and a PC with the necessary software. Experimental data was collected in the presence of an artificial landslide, and the results show that the lower FBGs are more sensitive than the upper FBGs for all four of the custom sensors. It was also found that Sensor 2 and Sensor 4 are more capable of monitoring small-scale landslides than Sensor 1 and Sensor 3, and this is mainly due to their placement location with respect to the landslide. The stronger rods used in the hard sensors make them more adaptable to the harsh environments of large landslides. Thus, hard sensors should be fixed near the landslide, while soft sensors should be placed farther away from the landslide. In addition, a clear tendency of strain variation can be detected by the soft sensors, which can be used to predict landslides and raise a hazard alarm.

  2. Determination of binding constants of cyclodextrin inclusion complexes with amino acids and dipeptides by potentiometric titration.

    PubMed

    Kahle, Claudia; Holzgrabe, Ulrike

    2004-10-01

    Cyclodextrins are well known for their ability to separate enantiomers of drugs, natural products, and other chiral substances using HPLC, GC, or CE. The resolution of the enantiomers is due to the formation of diastereomeric complexes between the cyclodextrin and the pairs of enantiomers. The aim of this study was to determine the binding constants of the complexes between alpha- and beta-cyclodextrin and the enantiomers of a series of aliphatic and aromatic amino acids, and dipeptides, using a potentiometric titration method. The results of this method are compared to other methods, and correlated to findings in cyclodextrin-modified capillary electrophoresis and possible complex structures. Potentiometric titration was found to be an appropriate tool to determine the binding constants of cyclodextrin inclusion complexes.

  3. A MEMS SOI-based piezoresistive fluid flow sensor

    NASA Astrophysics Data System (ADS)

    Tian, B.; Li, H. F.; Yang, H.; Song, D. L.; Bai, X. W.; Zhao, Y. L.

    2018-02-01

    In this paper, a SOI (silicon-on-insulator)-based piezoresistive fluid flow sensor is presented; the presented flow sensor mainly consists of a nylon sensing head, stainless steel cantilever beam, SOI sensor chip, printed circuit board, half-cylinder gasket, and stainless steel shell. The working principle of the sensor and some detailed contrastive analysis about the sensor structure were introduced since the nylon sensing head and stainless steel cantilever beam have distinct influence on the sensor performance; the structure of nylon sensing head and stainless steel cantilever beam is also discussed. The SOI sensor chip was fabricated using micro-electromechanical systems technologies, such as reactive ion etching and low pressure chemical vapor deposition. The designed fluid sensor was packaged and tested; a calibration installation system was purposely designed for the sensor experiment. The testing results indicated that the output voltage of the sensor is proportional to the square of the fluid flow velocity, which is coincident with the theoretical derivation. The tested sensitivity of the sensor is 3.91 × 10-4 V ms2/kg.

  4. Nano-level monitoring of Mn(2+) ion by fabrication of coated pyrolytic graphite electrode based on isonicotinohydrazide derivatives.

    PubMed

    Sahani, Manoj Kumar; Singh, A K; Jain, A K

    2015-05-01

    The two ionophores N'(N',N‴E,N',N‴E)-N',N‴-((((oxybis(ethane-2,1-diyl))bis(oxy)) bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I1) and (N',N‴E,N',N‴E)-N',N‴-(((propane-1,3-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))di(isonicotinohydrazide) (I2) were synthesised and investigated as neutral carrier in the fabrication of Mn(2+) ion selective sensor. Several membranes were prepared by incorporating different plasticizers and anionic excluders and their effect on potentiometric response was studied. The best analytical performance was obtained with the electrode having a membrane of composition of I2: PVC: o-NPOE: NaTPB in the ratio of 6:34:58:2 (w/w, mg). Comparative studies of coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE) based on I2 reveal the superiority of CPGE. The CPGE exhibits wide working concentration range of 1.23×10(-8)-1.0×10(-1) mol L(-1) and a detection limit down to 4.78×10(-9) mol L(-1) with a Nernstian slope of 29.5±0.4 mV decade(-1) of activity. The sensor performs satisfactorily over a wide pH range (3.5-9.0) and exhibited a quick response time (9s). The sensor can work satisfactorily in water-acetonitrile and water-methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor could be used for a period of four months without any significant divergence in performance. The sensor reflects its utility in the quantification of Mn(2+) ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Mn(2+) ion with ethylenediaminetetraacetic acid (EDTA). Copyright © 2015 Elsevier B.V. All rights reserved.

  5. A Solar Position Sensor Based on Image Vision

    PubMed Central

    Ruelas, Adolfo; Velázquez, Nicolás; Villa-Angulo, Carlos; Rosales, Pedro; Suastegui, José

    2017-01-01

    Solar collector technologies operate with better performance when the Sun beam direction is normal to the capturing surface, and for that to happen despite the relative movement of the Sun, solar tracking systems are used, therefore, there are rules and standards that need minimum accuracy for these tracking systems to be used in solar collectors’ evaluation. Obtaining accuracy is not an easy job, hence in this document the design, construction and characterization of a sensor based on a visual system that finds the relative azimuth error and height of the solar surface of interest, is presented. With these characteristics, the sensor can be used as a reference in control systems and their evaluation. The proposed sensor is based on a microcontroller with a real-time clock, inertial measurement sensors, geolocation and a vision sensor, that obtains the angle of incidence from the sunrays’ direction as well as the tilt and sensor position. The sensor’s characterization proved how a measurement of a focus error or a Sun position can be made, with an accuracy of 0.0426° and an uncertainty of 0.986%, which can be modified to reach an accuracy under 0.01°. The validation of this sensor was determined showing the focus error on one of the best commercial solar tracking systems, a Kipp & Zonen SOLYS 2. To conclude, the solar tracking sensor based on a vision system meets the Sun detection requirements and components that meet the accuracy conditions to be used in solar tracking systems and their evaluation or, as a tracking and orientation tool, on photovoltaic installations and solar collectors. PMID:28758935

  6. Factors influencing the performance of G-quadruplex DNAzyme-based sensors.

    PubMed

    Kong, De-Ming

    2013-12-15

    G-quadruplex DNAzymes are peroxidase-like complexes formed by nucleic acid G-quadruplexes and hemin. Compared with natural enzymes, G-quadruplex DNAzyme offers many advantages, thus making it a promising tool in the design of biosensors and chemical sensors. Many biosensors and chemical sensors based on G-quadruplex DNAzymes have been reported. A number of factors may affect the performance of G-quadruplex DNAzyme-based sensors. Here we focus on some aspects to be taken into account when designing a G-quadruplex DNAzyme-based sensor. These include the G-quadruplex-forming G-rich sequence, solution components, the reaction substrate, and enrichment strategy for G-quadruplex DNAzyme. We also provide an outlook for further research on G-quadruplex DNAzyme-based sensors. Copyright © 2013 Elsevier Inc. All rights reserved.

  7. Development of a Waterproof Crack-Based Stretchable Strain Sensor Based on PDMS Shielding.

    PubMed

    Hong, Seong Kyung; Yang, Seongjin; Cho, Seong J; Jeon, Hyungkook; Lim, Geunbae

    2018-04-12

    This paper details the design of a poly(dimethylsiloxane) (PDMS)-shielded waterproof crack-based stretchable strain sensor, in which the electrical characteristics and sensing performance are not influenced by changes in humidity. This results in a higher number of potential applications for the sensor. A previously developed omni-purpose stretchable strain (OPSS) sensor was used as the basis for this work, which utilizes a metal cracking structure and provides a wide sensing range and high sensitivity. Changes in the conductivity of the OPSS sensor, based on humidity conditions, were investigated along with the potential possibility of using the design as a humidity sensor. However, to prevent conductivity variation, which can decrease the reliability and sensing ability of the OPSS sensor, PDMS was utilized as a shielding layer over the OPSS sensor. The PDMS-shielded OPSS sensor showed approximately the same electrical characteristics as previous designs, including in a high humidity environment, while maintaining its strain sensing capabilities. The developed sensor shows promise for use under high humidity conditions and in underwater applications. Therefore, considering its unique features and reliable sensing performance, the developed PDMS-shielded waterproof OPSS sensor has potential utility in a wide range of applications, such as motion monitoring, medical robotics and wearable healthcare devices.

  8. Using Custom Fiber Bragg Grating-Based Sensors to Monitor Artificial Landslides

    PubMed Central

    Zhang, Qinghua; Wang, Yuan; Sun, Yangyang; Gao, Lei; Zhang, Zhenglin; Zhang, Wenyuan; Zhao, Pengchong; Yue, Yin

    2016-01-01

    Four custom fiber Bragg grating (FBG)-based sensors are developed to monitor an artificial landslide located in Nanjing, China. The sensors are composed of a rod and two FBGs. Based on the strength of the rods, two sensors are referred to as “hard sensors” (Sensor 1 and Sensor 2), the other two are referred to as “soft sensors” (Sensor 3 and Sensor 4). The two FBGs are fixed on each sensor rod at distances of 50 cm and 100 cm from the top of the rod (an upper FBG and a lower FBG). In the experiment presented in this paper, the sensors are installed on a slope on which an artificial landslide is generated through both machine-based and manual excavation. The fiber sensing system consists of the four custom FBG-based sensors, optical fiber, a static fiber grating demodulation instrument (SM125), and a PC with the necessary software. Experimental data was collected in the presence of an artificial landslide, and the results show that the lower FBGs are more sensitive than the upper FBGs for all four of the custom sensors. It was also found that Sensor 2 and Sensor 4 are more capable of monitoring small-scale landslides than Sensor 1 and Sensor 3, and this is mainly due to their placement location with respect to the landslide. The stronger rods used in the hard sensors make them more adaptable to the harsh environments of large landslides. Thus, hard sensors should be fixed near the landslide, while soft sensors should be placed farther away from the landslide. In addition, a clear tendency of strain variation can be detected by the soft sensors, which can be used to predict landslides and raise a hazard alarm. PMID:27598163

  9. Microbial BOD sensors based on Zr (IV)-loaded collagen fiber.

    PubMed

    Zhao, Lei; He, Li; Chen, Shujuan; Zou, Likou; Zhou, Kang; Ao, Xiaolin; Liu, Shuliang; Hu, Xinjie; Han, Guoquan

    2017-03-01

    Biochemical oxygen demand (BOD) sensors based on Zr (IV)-loaded collagen fiber (ZrCF), a novel material with great porous structure, were developed. This novel material shows adsorbability by microorganisms. Saccharomyces cerevisiae and Escherichia coli were used for the construction of BOD sensors. Factors affecting BOD sensor performance were examined. The ZrCF-based BOD sensor showed different sensitivities and linear response ranges with different biofilm densities. The amount of microorganisms strongly affected the performance of the BOD sensor. Poor permeability of previously reported immobilization carriers were greatly circumvented by ZrCF. The service life of the ZrCF-based BOD sensor was more than 42 days. The immobilized microorganisms can be stored for more than 6 months under 4°C in PB solution. There was good correlation between the results of the sensor method and the standard 5-day BOD method in the determination of pure organic substrates and real water samples. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process.

    PubMed

    Naja, Ghinwa; Mustin, Christian; Volesky, Bohumil; Berthelin, Jacques

    2006-01-01

    An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations. The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity. The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared. The resin stabilized the initial electrochemical potential to -405+/-5 mV corresponding to 2 micro gl(-1) of lead concentration in solution. The amounts of lead sorbed by R. arrhizus biomass and diatomite were 0.9 mmol g(-1) (C(e)=5.16 x 10(-2)mM) and 0.052 mmol g(-1) (C(e)=5.97 x 10(-2) mM), respectively. Lead sorption by the fungal biomass was pinpointed to at least two types of chemical active sites. The first type was distinguished by high reactivity and a low number of sites whereas the other was characterized by their higher number and lower reactivity.

  11. Flexible Graphene-Based Wearable Gas and Chemical Sensors.

    PubMed

    Singh, Eric; Meyyappan, M; Nalwa, Hari Singh

    2017-10-11

    Wearable electronics is expected to be one of the most active research areas in the next decade; therefore, nanomaterials possessing high carrier mobility, optical transparency, mechanical robustness and flexibility, lightweight, and environmental stability will be in immense demand. Graphene is one of the nanomaterials that fulfill all these requirements, along with other inherently unique properties and convenience to fabricate into different morphological nanostructures, from atomically thin single layers to nanoribbons. Graphene-based materials have also been investigated in sensor technologies, from chemical sensing to detection of cancer biomarkers. The progress of graphene-based flexible gas and chemical sensors in terms of material preparation, sensor fabrication, and their performance are reviewed here. The article provides a brief introduction to graphene-based materials and their potential applications in flexible and stretchable wearable electronic devices. The role of graphene in fabricating flexible gas sensors for the detection of various hazardous gases, including nitrogen dioxide (NO 2 ), ammonia (NH 3 ), hydrogen (H 2 ), hydrogen sulfide (H 2 S), carbon dioxide (CO 2 ), sulfur dioxide (SO 2 ), and humidity in wearable technology, is discussed. In addition, applications of graphene-based materials are also summarized in detecting toxic heavy metal ions (Cd, Hg, Pb, Cr, Fe, Ni, Co, Cu, Ag), and volatile organic compounds (VOCs) including nitrobenzene, toluene, acetone, formaldehyde, amines, phenols, bisphenol A (BPA), explosives, chemical warfare agents, and environmental pollutants. The sensitivity, selectivity and strategies for excluding interferents are also discussed for graphene-based gas and chemical sensors. The challenges for developing future generation of flexible and stretchable sensors for wearable technology that would be usable for the Internet of Things (IoT) are also highlighted.

  12. Neural Network-Based Sensor Validation for Turboshaft Engines

    NASA Technical Reports Server (NTRS)

    Moller, James C.; Litt, Jonathan S.; Guo, Ten-Huei

    1998-01-01

    Sensor failure detection, isolation, and accommodation using a neural network approach is described. An auto-associative neural network is configured to perform dimensionality reduction on the sensor measurement vector and provide estimated sensor values. The sensor validation scheme is applied in a simulation of the T700 turboshaft engine in closed loop operation. Performance is evaluated based on the ability to detect faults correctly and maintain stable and responsive engine operation. The set of sensor outputs used for engine control forms the network input vector. Analytical redundancy is verified by training networks of successively smaller bottleneck layer sizes. Training data generation and strategy are discussed. The engine maintained stable behavior in the presence of sensor hard failures. With proper selection of fault determination thresholds, stability was maintained in the presence of sensor soft failures.

  13. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, May 2005

    USGS Publications Warehouse

    Ortiz, A.G.; Blanchard, R.A.

    2006-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is a highly productive aquifer and supplies more than 10 times the amount of water pumped from either the surficial aquifer system or the intermediate aquifer system in most of the study area (Duerr and others, 1988). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2005. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in a tightly cased well that taps a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 67.27 inches for west-central Florida (from June 2004 through May 2005) was 14.20 inches above the historical cumulative average of 53.07 inches (Southwest Florida Water Management District (SWFWMD), 2005). The above average precipitation is attributed to the active hurrican season for Florida in 2004. Historical cumulative averages are calculated from regional rainfall summary reports (1915 to the most recent completed calendar year) and are updated monthly by the SWFWMD. This report, prepared by the U.S. Geological Survey (USGS) in cooperation with the SWFWMD, is part of a semiannual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to

  14. Higher-order mode photonic crystal based nanofluidic sensor

    NASA Astrophysics Data System (ADS)

    Peng, Wang; Chen, Youping; Ai, Wu

    2017-01-01

    A higher-order photonic crystal (PC) based nanofluidic sensor, which worked at 532 nm, was designed and demonstrated. A systematical and detailed method for sculpturing a PC sensor for a given peak wavelength value (PWV) and specified materials was illuminated. It was the first time that the higher order mode was used to design PC based nanofluidic sensor, and the refractive index (RI) sensitivity of this sensor had been verified with FDTD simulation software from Lumerical. The enhanced electrical field of higher order mode structure was mostly confined in the channel area, where the enhance field is wholly interacting with the analytes in the channels. The comparison of RI sensitivity between fundamental mode and higher order mode shows the RI variation of higher order mode is 124.5 nm/RIU which is much larger than the fundamental mode. The proposed PC based nanofluidic structure pioneering a novel style for future optofluidic design.

  15. Applying Sensor-Based Technology to Improve Construction Safety Management.

    PubMed

    Zhang, Mingyuan; Cao, Tianzhuo; Zhao, Xuefeng

    2017-08-11

    Construction sites are dynamic and complicated systems. The movement and interaction of people, goods and energy make construction safety management extremely difficult. Due to the ever-increasing amount of information, traditional construction safety management has operated under difficult circumstances. As an effective way to collect, identify and process information, sensor-based technology is deemed to provide new generation of methods for advancing construction safety management. It makes the real-time construction safety management with high efficiency and accuracy a reality and provides a solid foundation for facilitating its modernization, and informatization. Nowadays, various sensor-based technologies have been adopted for construction safety management, including locating sensor-based technology, vision-based sensing and wireless sensor networks. This paper provides a systematic and comprehensive review of previous studies in this field to acknowledge useful findings, identify the research gaps and point out future research directions.

  16. Fully-Polymeric pH Sensor Realized by Means of a Single-Step Soft Embossing Technique

    PubMed Central

    Fanzio, Paola; Chang, Chi-Tung; Skolimowski, Maciej; Tanzi, Simone; Sasso, Luigi

    2017-01-01

    We present here an electrochemical sensor microsystem for the monitoring of pH. The all-polymeric device is comprised of a cyclic olefin copolymer substrate, a 200 nm-thin patterned layer of conductive polymer (PEDOT), and a 70 nm electropolymerized layer of a pH sensitive conductive polymer (polyaniline). The patterning of the fluidic (microfluidic channels) and conductive (wiring and electrodes) functional elements was achieved with a single soft PDMS mold via a single embossing step process. A post-processing treatment with ethylene glycol assured the functional enhancement of the electrodes, as demonstrated via an electrical and electrochemical characterization. A surface modification of the electrodes was carried out, based on voltammetric electropolymerization, to obtain a thin layer of polyaniline. The mechanism for pH sensing is based on the redox reactions of the polyaniline layer caused by protonation. The sensing performance of the microsystem was finally validated by monitoring its potentiometric response upon exposure to a relevant range of pH. PMID:28531106

  17. Fully-Polymeric pH Sensor Realized by Means of a Single-Step Soft Embossing Technique.

    PubMed

    Fanzio, Paola; Chang, Chi-Tung; Skolimowski, Maciej; Tanzi, Simone; Sasso, Luigi

    2017-05-20

    We present here an electrochemical sensor microsystem for the monitoring of pH. The all-polymeric device is comprised of a cyclic olefin copolymer substrate, a 200 nm-thin patterned layer of conductive polymer (PEDOT), and a 70 nm electropolymerized layer of a pH sensitive conductive polymer (polyaniline). The patterning of the fluidic (microfluidic channels) and conductive (wiring and electrodes) functional elements was achieved with a single soft PDMS mold via a single embossing step process. A post-processing treatment with ethylene glycol assured the functional enhancement of the electrodes, as demonstrated via an electrical and electrochemical characterization. A surface modification of the electrodes was carried out, based on voltammetric electropolymerization, to obtain a thin layer of polyaniline. The mechanism for pH sensing is based on the redox reactions of the polyaniline layer caused by protonation. The sensing performance of the microsystem was finally validated by monitoring its potentiometric response upon exposure to a relevant range of pH.

  18. Potentiometric assessment of iron release during ferritin reduction by exogenous agents.

    PubMed

    Vladimirova, Lilia S; Kochev, Valery K

    2010-09-01

    This work studied the possibilities for quantitative determination of iron mobilization in connection with ferritin reduction by ascorbic acid (vitamin C) and sodium dithionite in vitro. The iron storage protein was incubated with an excess of reductant in aerobic conditions in the absence of complexing agents in the medium. The release of Fe(2+) was let to go to completion, and the overall content of Fe(2+) in the solution was evaluated with the aid of potentiometric titration using Ce(4+) as an oxidizing titrant. Results suggest a moderate iron efflux under the influence of the chosen reducing agents. Although such a reduction of the protein mineral core by dihydroxyfumarate contributes greatly to the iron mobilization, ferritin behavior with vitamin C and dithionite seems to be different. Although redox properties of dihydroxyfumarate are determined by hydroxyl groups similar to those of ascorbic acid, the two compounds differ significantly in structure, and this could be the basis for an explanation of the specificities in their interaction with ferritin. As revealed by the study, potentiometric titration promises to be a reliable tool for evaluation of the amount of Fe(2+) present in the solution as a result of the reduction of the ferritin's mineral core. 2010 Elsevier Inc. All rights reserved.

  19. Scalable Multicast Protocols for Overlapped Groups in Broker-Based Sensor Networks

    NASA Astrophysics Data System (ADS)

    Kim, Chayoung; Ahn, Jinho

    In sensor networks, there are lots of overlapped multicast groups because of many subscribers, associated with their potentially varying specific interests, querying every event to sensors/publishers. And gossip based communication protocols are promising as one of potential solutions providing scalability in P(Publish)/ S(Subscribe) paradigm in sensor networks. Moreover, despite the importance of both guaranteeing message delivery order and supporting overlapped multicast groups in sensor or P2P networks, there exist little research works on development of gossip-based protocols to satisfy all these requirements. In this paper, we present two versions of causally ordered delivery guaranteeing protocols for overlapped multicast groups. The one is based on sensor-broker as delegates and the other is based on local views and delegates representing subscriber subgroups. In the sensor-broker based protocol, sensor-broker might lead to make overlapped multicast networks organized by subscriber's interests. The message delivery order has been guaranteed consistently and all multicast messages are delivered to overlapped subscribers using gossip based protocols by sensor-broker. Therefore, these features of the sensor-broker based protocol might be significantly scalable rather than those of the protocols by hierarchical membership list of dedicated groups like traditional committee protocols. And the subscriber-delegate based protocol is much stronger rather than fully decentralized protocols guaranteeing causally ordered delivery based on only local views because the message delivery order has been guaranteed consistently by all corresponding members of the groups including delegates. Therefore, this feature of the subscriber-delegate protocol is a hybrid approach improving the inherent scalability of multicast nature by gossip-based technique in all communications.

  20. Development of GaN-based micro chemical sensor nodes

    NASA Technical Reports Server (NTRS)

    Son, Kyung-ah; Prokopuk, Nicholas; George, Thomas; Moon, Jeong S.

    2005-01-01

    Sensors based on III-N technology are gaining significant interest due to their potential for monolithic integration of RF transceivers and light sources and the capability of high temperature operations. We are developing a GaN-based micro chemical sensor node for remote detection of chemical toxins, and present electrical responses of AlGaN/GaN HEMT (High Electron Mobility Transistor) sensors to chemical toxins as well as other common gases.

  1. pH sensor based on boron nitride nanotubes.

    PubMed

    Huang, Q; Bando, Y; Zhao, L; Zhi, C Y; Golberg, D

    2009-10-14

    A submicrometer-sized pH sensor based on biotin-fluorescein-functionalized multiwalled BN nanotubes with anchored Ag nanoparticles is designed. Intrinsic pH-dependent photoluminescence and Raman signals in attached fluorescein molecules enhanced by Ag nanoparticles allow this novel nanohybrid to perform as a practical pH sensor. It is able to work in a submicrometer-sized space. For example, the sensor may determine the environmental pH of sub-units in living cells where a traditional optical fiber sensor fails because of spatial limitations.

  2. pH sensor based on boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Q.; Bando, Y.; Zhao, L.; Zhi, C. Y.; Golberg, D.

    2009-10-01

    A submicrometer-sized pH sensor based on biotin-fluorescein-functionalized multiwalled BN nanotubes with anchored Ag nanoparticles is designed. Intrinsic pH-dependent photoluminescence and Raman signals in attached fluorescein molecules enhanced by Ag nanoparticles allow this novel nanohybrid to perform as a practical pH sensor. It is able to work in a submicrometer-sized space. For example, the sensor may determine the environmental pH of sub-units in living cells where a traditional optical fiber sensor fails because of spatial limitations.

  3. Development of paper-based electrochemical sensors for water quality monitoring

    NASA Astrophysics Data System (ADS)

    Smith, Suzanne; Bezuidenhout, Petroné; Mbanjwa, Mesuli; Zheng, Haitao; Conning, Mariette; Palaniyandy, Nithyadharseni; Ozoemena, Kenneth; Land, Kevin

    2016-02-01

    We present a method for the development of paper-based electrochemical sensors for detection of heavy metals in water samples. Contaminated water leads to serious health problems and environmental issues. Paper is ideally suited for point-of-care testing, as it is low cost, disposable, and multi-functional. Initial sensor designs were manufactured on paper substrates using combinations of inkjet printing and screen printing technologies using silver and carbon inks. Bismuth onion-like carbon nanoparticle ink was manufactured and used as the active material of the sensor for both commercial and paper-based sensors, which were compared using standard electrochemical analysis techniques. The results highlight the potential of paper-based sensors to be used effectively for rapid water quality monitoring at the point-of-need.

  4. Potentiometric surfaces, summer 2013 and winter 2015, and select hydrographs for the Southern High Plains aquifer, Cannon Air Force Base, Curry County, New Mexico

    USGS Publications Warehouse

    Collison, Jake

    2016-04-07

    Cannon Air Force Base (Cannon AFB) is located in the High Plains physiographic region of east-central New Mexico, about 5 miles west of Clovis, New Mexico. The area surrounding Cannon AFB is primarily used for agriculture, including irrigated cropland and dairies. The Southern High Plains aquifer is the principal source of water for Cannon AFB, for the nearby town of Clovis, and for local agriculture and dairies. The Southern High Plains aquifer in the vicinity of Cannon AFB consists of three subsurface geological formations: the Chinle Formation of Triassic age, the Ogallala Formation of Tertiary age, and the Blackwater Draw Formation of Quaternary age. The Ogallala Formation is the main water-yielding formation of the Southern High Plains aquifer. Groundwater-supplied, center-pivot irrigation dominates pumping from the Southern High Plains aquifer in the area surrounding Cannon AFB, where the irrigation season typically extends from early March through October. The U.S. Geological Survey has been monitoring groundwater levels in the vicinity of Cannon AFB since 1954 and has developed general potentiometric-surface maps that show groundwater flow from northwest to southeast in the study area. While previous potentiometric-surface maps show the general direction of groundwater flow, a denser well network is needed to show details of groundwater flow at a local scale. Groundwater levels were measured in 93 wells during summer 2013 and 100 wells during winter 2015.The summer and winter potentiometric-surface maps display the presence of what is interpreted to be a groundwater trough trending from the northwest to the southeast through the study area. This groundwater trough may be the hydraulic expression of a Tertiary-age paleochannel. Groundwater north of the trough flows in a southerly direction into the trough, and groundwater south of the trough flows in an easterly direction into the trough.During the 18-month period between summer 2013 and winter 2015, changes

  5. Conductive fiber-based ultrasensitive textile pressure sensor for wearable electronics.

    PubMed

    Lee, Jaehong; Kwon, Hyukho; Seo, Jungmok; Shin, Sera; Koo, Ja Hoon; Pang, Changhyun; Son, Seungbae; Kim, Jae Hyung; Jang, Yong Hoon; Kim, Dae Eun; Lee, Taeyoon

    2015-04-17

    A flexible and sensitive textile-based pressure sensor is developed using highly conductive fibers coated with dielectric rubber materials. The pressure sensor exhibits superior sensitivity, very fast response time, and high stability, compared with previous textile-based pressure sensors. By using a weaving method, the pressure sensor can be applied to make smart gloves and clothes that can control machines wirelessly as human-machine interfaces. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Lead in Hair and in Red Wine by Potentiometric Stripping Analysis: The University Students' Design.

    ERIC Educational Resources Information Center

    Josephsen, Jens

    1985-01-01

    A new program for training upper secondary school chemistry teachers (SE 537 693) depends heavily on student project work. A project in which lead in hair and in red wine was examined by potentiometric stripping analysis is described and evaluated. (JN)

  7. Augmenting the senses: a review on sensor-based learning support.

    PubMed

    Schneider, Jan; Börner, Dirk; van Rosmalen, Peter; Specht, Marcus

    2015-02-11

    In recent years sensor components have been extending classical computer-based support systems in a variety of applications domains (sports, health, etc.). In this article we review the use of sensors for the application domain of learning. For that we analyzed 82 sensor-based prototypes exploring their learning support. To study this learning support we classified the prototypes according to the Bloom's taxonomy of learning domains and explored how they can be used to assist on the implementation of formative assessment, paying special attention to their use as feedback tools. The analysis leads to current research foci and gaps in the development of sensor-based learning support systems and concludes with a research agenda based on the findings.

  8. Evaluation of accelerometer based multi-sensor versus single-sensor activity recognition systems.

    PubMed

    Gao, Lei; Bourke, A K; Nelson, John

    2014-06-01

    Physical activity has a positive impact on people's well-being and it had been shown to decrease the occurrence of chronic diseases in the older adult population. To date, a substantial amount of research studies exist, which focus on activity recognition using inertial sensors. Many of these studies adopt a single sensor approach and focus on proposing novel features combined with complex classifiers to improve the overall recognition accuracy. In addition, the implementation of the advanced feature extraction algorithms and the complex classifiers exceed the computing ability of most current wearable sensor platforms. This paper proposes a method to adopt multiple sensors on distributed body locations to overcome this problem. The objective of the proposed system is to achieve higher recognition accuracy with "light-weight" signal processing algorithms, which run on a distributed computing based sensor system comprised of computationally efficient nodes. For analysing and evaluating the multi-sensor system, eight subjects were recruited to perform eight normal scripted activities in different life scenarios, each repeated three times. Thus a total of 192 activities were recorded resulting in 864 separate annotated activity states. The methods for designing such a multi-sensor system required consideration of the following: signal pre-processing algorithms, sampling rate, feature selection and classifier selection. Each has been investigated and the most appropriate approach is selected to achieve a trade-off between recognition accuracy and computing execution time. A comparison of six different systems, which employ single or multiple sensors, is presented. The experimental results illustrate that the proposed multi-sensor system can achieve an overall recognition accuracy of 96.4% by adopting the mean and variance features, using the Decision Tree classifier. The results demonstrate that elaborate classifiers and feature sets are not required to achieve high

  9. Electrochemical sensors and biosensors based on less aggregated graphene.

    PubMed

    Bo, Xiangjie; Zhou, Ming; Guo, Liping

    2017-03-15

    As a novel single-atom-thick sheet of sp 2 hybridized carbon atoms, graphene (GR) has attracted extensive attention in recent years because of its unique and remarkable properties, such as excellent electrical conductivity, large theoretical specific surface area, and strong mechanical strength. However, due to the π-π interaction, GR sheets are inclined to stack together, which may seriously degrade the performance of GR with the unique single-atom layer. In recent years, an increasing number of GR-based electrochemical sensors and biosensors are reported, which may reflect that GR has been considered as a kind of hot and promising electrode material for electrochemical sensor and biosensor construction. However, the active sites on GR surface induced by the irreversible GR aggregations would be deeply secluded inside the stacked GR sheets and therefore are not available for the electrocatalysis. So the alleviation or the minimization of the aggregation level for GR sheets would facilitate the exposure of active sites on GR and effectively upgrade the performance of GR-based electrochemical sensors and biosensors. Less aggregated GR with low aggregation and high dispersed structure can be used in improving the electrochemical activity of GR-based electrochemical sensors or biosensors. In this review, we summarize recent advances and new progress for the development of electrochemical sensors based on less aggregated GR. To achieve such goal, many strategies (such as the intercalation of carbon materials, surface modification, and structural engineering) have been applied to alleviate the aggregation level of GR in order to enhance the performance of GR-based electrochemical sensors and biosensors. Finally, the challenges associated with less aggregated GR-based electrochemical sensors and biosensors as well as related future research directions are discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. A market-based optimization approach to sensor and resource management

    NASA Astrophysics Data System (ADS)

    Schrage, Dan; Farnham, Christopher; Gonsalves, Paul G.

    2006-05-01

    Dynamic resource allocation for sensor management is a problem that demands solutions beyond traditional approaches to optimization. Market-based optimization applies solutions from economic theory, particularly game theory, to the resource allocation problem by creating an artificial market for sensor information and computational resources. Intelligent agents are the buyers and sellers in this market, and they represent all the elements of the sensor network, from sensors to sensor platforms to computational resources. These agents interact based on a negotiation mechanism that determines their bidding strategies. This negotiation mechanism and the agents' bidding strategies are based on game theory, and they are designed so that the aggregate result of the multi-agent negotiation process is a market in competitive equilibrium, which guarantees an optimal allocation of resources throughout the sensor network. This paper makes two contributions to the field of market-based optimization: First, we develop a market protocol to handle heterogeneous goods in a dynamic setting. Second, we develop arbitrage agents to improve the efficiency in the market in light of its dynamic nature.

  11. Applying Sensor-Based Technology to Improve Construction Safety Management

    PubMed Central

    Zhang, Mingyuan; Cao, Tianzhuo; Zhao, Xuefeng

    2017-01-01

    Construction sites are dynamic and complicated systems. The movement and interaction of people, goods and energy make construction safety management extremely difficult. Due to the ever-increasing amount of information, traditional construction safety management has operated under difficult circumstances. As an effective way to collect, identify and process information, sensor-based technology is deemed to provide new generation of methods for advancing construction safety management. It makes the real-time construction safety management with high efficiency and accuracy a reality and provides a solid foundation for facilitating its modernization, and informatization. Nowadays, various sensor-based technologies have been adopted for construction safety management, including locating sensor-based technology, vision-based sensing and wireless sensor networks. This paper provides a systematic and comprehensive review of previous studies in this field to acknowledge useful findings, identify the research gaps and point out future research directions. PMID:28800061

  12. Validation of Underwater Sensor Package Using Feature Based SLAM

    PubMed Central

    Cain, Christopher; Leonessa, Alexander

    2016-01-01

    Robotic vehicles working in new, unexplored environments must be able to locate themselves in the environment while constructing a picture of the objects in the environment that could act as obstacles that would prevent the vehicles from completing their desired tasks. In enclosed environments, underwater range sensors based off of acoustics suffer performance issues due to reflections. Additionally, their relatively high cost make them less than ideal for usage on low cost vehicles designed to be used underwater. In this paper we propose a sensor package composed of a downward facing camera, which is used to perform feature tracking based visual odometry, and a custom vision-based two dimensional rangefinder that can be used on low cost underwater unmanned vehicles. In order to examine the performance of this sensor package in a SLAM framework, experimental tests are performed using an unmanned ground vehicle and two feature based SLAM algorithms, the extended Kalman filter based approach and the Rao-Blackwellized, particle filter based approach, to validate the sensor package. PMID:26999142

  13. Potentiometric maps of the Sparta Sand, northern Louisiana and southern Arkansas, 1900, 1965, 1975, and 1980

    USGS Publications Warehouse

    Ryals, G.N.

    1980-01-01

    The potentiometric surface of the Sparta Sand in northern Louisiana is shown by contours on four maps. Maps for 1900, 1965 , and spring 1975 are generalized, small-scale maps from previously published reports. The spring 1980 map (1:500,000) is based on measurements in 144 wells and includes the southern tier of counties in southern Arkansas. The map shows regional effects of pumping from the Sparta Sand and effects of local pumping centers at Magnolia and El Dorado, Ark., and at Minden, Ruston, Jonesboro-Hodge, Winnfield, Bastrop, and in the Monroe area of Louisiana. (USGS)

  14. EDITORIAL: Sensors based on interfaces

    NASA Astrophysics Data System (ADS)

    Camassel, Jean; Soukiassian, Patrick G.

    2007-12-01

    of Physics D: Applied Physics describe some recent advances in this field and the very different approaches and/or techniques that can be used for the sensors' implementation. They include the use of molecularly modified metal nanoparticles in or as chemical sensors, especially for high sensitivity hydrogen sensors. Hydrogen sensing can also be achieved by performing galvanic measurements on a thin layer of perovskite oxide covered with platinum. In this case, one mixes an ionic (proton) transport in the oxide with an electronic one in the metal. Another focus is on optical and electrical read-out techniques, like surface-plasmon resonance (SPR), such as for immuno-sensor applications or piezo-electrical and electro-chemical detection. Toward this end, the preparation, structure and application of functional interfacial surfaces are described and discussed. A totally different approach based on the use of Hall effect measurements performed on a granular metal-oxide-semiconductor layer and different experimental solutions is also presented. Finally, optical sensors are addressed through the photonic modulation of surface properties or transmission interferometric absorption sensors. Mixed electrical and optical chemical sensors are also examined.

  15. Toward wearable sensors: optical sensor for detection of ammonium nitrate-based explosives, ANFO and ANNM.

    PubMed

    Sheykhi, Sara; Mosca, Lorenzo; Anzenbacher, Pavel

    2017-05-04

    Increasing security needs require compact and portable detection tools for the rapid and reliable identification of explosives used in improvised explosive devices (IEDs). We report of an easy-to-use optical sensor for both vapour-phase and solution-phase identification of explosive mixtures that uses a cross-reactive fluorimetric sensor array comprising chemically responsive fluorimetric indicators composed of aromatic aldehydes and polyethyleneimine. Ammonium nitrate-nitromethane (ANNM) was analyzed by paper microzone arrays and nanofiber sensor mats. Progress toward wearable sensors based on electrospun nanofiber mats is outlined.

  16. Load monitoring using a calibrated piezo diaphragm based impedance strain sensor and wireless sensor network in real time

    NASA Astrophysics Data System (ADS)

    Gopal Madhav Annamdas, Venu; Kiong Soh, Chee

    2017-04-01

    The last decade has seen the use of various wired-wireless and contact-contactless sensors in several structural health monitoring (SHM) techniques. Most SHM sensors that are predominantly used for strain measurements may be ineffective for damage detection and vice versa, indicating the uniapplicability of these sensors. However, piezoelectric (PE)-based macro fiber composite (MFC) and lead zirconium titanate (PZT) sensors have been on the rise in SHM, vibration and damping control, etc, due to their superior actuation and sensing abilities. These PE sensors have created much interest for their multi-applicability in various technologies such as electromechanical impedance (EMI)-based SHM. This research employs piezo diaphragms, a cheaper alternative to several expensive types of PZT/MFC sensors for the EMI technique. These piezo diaphragms were validated last year for their applicability in damage detection using the frequency domain. Here we further validate their applicability in strain monitoring using the real time domain. Hence, these piezo diaphragms can now be classified as PE sensors and used with PZT and MFC sensors in the EMI technique for monitoring damage and loading. However, no single technique or single type of sensor will be sufficient for large SHM, thus requiring the necessary deployment of more than one technique with different types of sensors such as a piezoresistive strain gauge based wireless sensor network for strain measurements to complement the EMI technique. Furthermore, we present a novel procedure of converting a regular PE sensor in the ‘frequency domain’ to ‘real time domain’ for strain applications.

  17. Potentiometric surface of the Catahoula aquifer in central Louisiana, 2013

    USGS Publications Warehouse

    Fendick, Jr., Robert B.; Carter, Kayla

    2015-12-09

    The potentiometric surface of the Catahoula aquifer was constructed by using the altitude of water levels measured at 29 wells during the period May through September 2013. The altitude of water levels ranged from 0.02 ft above the National Geodetic Vertical Datum of 1929 (NGVD 29) in well Co-51 to 238 ft above NGVD 29 in well Na-317. Groundwater movement in the Catahoula aquifer is generally to the southeast and towards discharge areas beneath the Sabine, Red, Little, and Tensas River Valleys.

  18. Potentiometric pH Measurements of Acidity Are Approximations, Some More Useful than Others

    ERIC Educational Resources Information Center

    de Levie, Robert

    2010-01-01

    A recent article by McCarty and Vitz "demonstrating that it is not true that pH = -log[H+]" is examined critically. Then, the focus shifts to underlying problems with the IUPAC definition of pH. It is shown how the potentiometric method can provide "estimates" of both the IUPAC-defined hydrogen activity "and" the hydrogen ion concentration, using…

  19. IBE-Lite: a lightweight identity-based cryptography for body sensor networks.

    PubMed

    Tan, Chiu C; Wang, Haodong; Zhong, Sheng; Li, Qun

    2009-11-01

    A body sensor network (BSN) is a network of sensors deployed on a person's body for health care monitoring. Since the sensors collect personal medical data, security and privacy are important components in a BSN. In this paper, we developed IBE-Lite, a lightweight identity-based encryption suitable for sensors in a BSN. We present protocols based on IBE-Lite that balance security and privacy with accessibility and perform evaluation using experiments conducted on commercially available sensors.

  20. Basement Membrane-Based Glucose Sensor Coatings Enhance Continuous Glucose Monitoring in Vivo

    PubMed Central

    Klueh, Ulrike; Qiao, Yi; Czajkowski, Caroline; Ludzinska, Izabela; Antar, Omar; Kreutzer, Donald L.

    2015-01-01

    Background: Implantable glucose sensors demonstrate a rapid decline in function that is likely due to biofouling of the sensor. Previous efforts directed at overcoming this issue has generally focused on the use of synthetic polymer coatings, with little apparent effect in vivo, clearly a novel approach is required. We believe that the key to extending sensor life span in vivo is the development of biocompatible basement membrane (BM) based bio-hydrogels as coatings for glucose sensors. Method: BM based bio-hydrogel sensor coatings were developed using purified BM preparations (ie, Cultrex from Trevigen Inc). Modified Abbott sensors were coated with Cultrex BM extracts. Sensor performance was evaluated for the impact of these coatings in vitro and in vivo in a continuous glucose monitoring (CGM) mouse model. In vivo sensor function was assessed over a 28-day time period expressed as mean absolute relative difference (MARD) values. Tissue reactivity of both Cultrex coated and uncoated glucose sensors was evaluated at 7, 14, 21 and 28 days post–sensor implantation with standard histological techniques. Results: The data demonstrate that Cultrex-based sensor coatings had no effect on glucose sensor function in vitro. In vivo glucose sensor performance was enhanced following BM coating as determined by MARD analysis, particularly in weeks 2 and 3. In vivo studies also demonstrated that Cultrex coatings significantly decreased sensor-induced tissue reactions at the sensor implantation sites. Conclusion: Basement-membrane-based sensor coatings enhance glucose sensor function in vivo, by minimizing or preventing sensor-induced tissues reactions. PMID:26306494

  1. Basement Membrane-Based Glucose Sensor Coatings Enhance Continuous Glucose Monitoring in Vivo.

    PubMed

    Klueh, Ulrike; Qiao, Yi; Czajkowski, Caroline; Ludzinska, Izabela; Antar, Omar; Kreutzer, Donald L

    2015-08-25

    Implantable glucose sensors demonstrate a rapid decline in function that is likely due to biofouling of the sensor. Previous efforts directed at overcoming this issue has generally focused on the use of synthetic polymer coatings, with little apparent effect in vivo, clearly a novel approach is required. We believe that the key to extending sensor life span in vivo is the development of biocompatible basement membrane (BM) based bio-hydrogels as coatings for glucose sensors. BM based bio-hydrogel sensor coatings were developed using purified BM preparations (ie, Cultrex from Trevigen Inc). Modified Abbott sensors were coated with Cultrex BM extracts. Sensor performance was evaluated for the impact of these coatings in vitro and in vivo in a continuous glucose monitoring (CGM) mouse model. In vivo sensor function was assessed over a 28-day time period expressed as mean absolute relative difference (MARD) values. Tissue reactivity of both Cultrex coated and uncoated glucose sensors was evaluated at 7, 14, 21 and 28 days post-sensor implantation with standard histological techniques. The data demonstrate that Cultrex-based sensor coatings had no effect on glucose sensor function in vitro. In vivo glucose sensor performance was enhanced following BM coating as determined by MARD analysis, particularly in weeks 2 and 3. In vivo studies also demonstrated that Cultrex coatings significantly decreased sensor-induced tissue reactions at the sensor implantation sites. Basement-membrane-based sensor coatings enhance glucose sensor function in vivo, by minimizing or preventing sensor-induced tissues reactions. © 2015 Diabetes Technology Society.

  2. Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 2007

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2009-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2007. The map is based on water-level measurements in 85 wells. The highest measured water level was 50 feet above sea level near the northern boundary and outcrop area of the aquifer in the central part of Anne Arundel County, and was below sea level just south of this area and in the remainder of the study area. The hydraulic gradient increased southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. A water level measured west of the Cheasapeake Beach area has declined to 57 feet below sea level due to increased withdrawals. The lowest water level measured was 162 feet below sea level at the center of a cone of depression at Lexington Park.

  3. A Bionic Camera-Based Polarization Navigation Sensor

    PubMed Central

    Wang, Daobin; Liang, Huawei; Zhu, Hui; Zhang, Shuai

    2014-01-01

    Navigation and positioning technology is closely related to our routine life activities, from travel to aerospace. Recently it has been found that Cataglyphis (a kind of desert ant) is able to detect the polarization direction of skylight and navigate according to this information. This paper presents a real-time bionic camera-based polarization navigation sensor. This sensor has two work modes: one is a single-point measurement mode and the other is a multi-point measurement mode. An indoor calibration experiment of the sensor has been done under a beam of standard polarized light. The experiment results show that after noise reduction the accuracy of the sensor can reach up to 0.3256°. It is also compared with GPS and INS (Inertial Navigation System) in the single-point measurement mode through an outdoor experiment. Through time compensation and location compensation, the sensor can be a useful alternative to GPS and INS. In addition, the sensor also can measure the polarization distribution pattern when it works in multi-point measurement mode. PMID:25051029

  4. Pseudo-indicator behaviour of platinum electrode explored for the potentiometric estimation of non-redox systems.

    PubMed

    Raashid, Syed; Chat, Oyais Ahmad; Rizvi, Masood A; Bhat, Mohsin Ahmad; Khan, Badruddin

    2012-11-15

    A pseudo-indicator electrode based potentiometric method for estimation of non-redox metal ions is presented. In the proposed method, nature and concentration specific impact of analyte over the redox potential of ideally polarisable Pt/pregenerated-redox-couple interface forms the basis of quantification. Utility of the method in estimation of six non-redox metal ions viz. Zn(2+), Cu(2+), Ni(2+), Cd(2+), Pb(2+), Al(3+) in the concentration range of 10(-1)-10(-3) moldm(-3), individually and as binary mixtures is also presented. Three types of potentiometric behaviours, which we ascribe to the nature specific thermodynamic and kinetic aspects of metal-EDTA binding, were observed. While Cu(2+), Ni(2+), Pb(2+) and Al(3+) were found to bind EDTA efficiently, without exchanging Fe(3+); Zn(2+) and Cd(2+) were observed to replace Fe(3+) from EDTA. In contrast, Ca(2+) and Mg(2+) were found to show no binding affinity to EDTA in the pH range employed in the present work. The proposed method was also used to explore the reversibility and the Nernestian behaviour of ferricyanide/ferrocyanide redox couple through spectroelectrochemical titration of Zn(2+) with ferrocyanide. The presented method is presaged to be a reliable and low cost future replacement for costly and delicate ion selective electrodes (ISE) in the estimation of non-redox species like Zn(2+), Cu(2+), etc. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. An Electronic-Nose Sensor Node Based on a Polymer-Coated Surface Acoustic Wave Array for Wireless Sensor Network Applications

    PubMed Central

    Tang, Kea-Tiong; Li, Cheng-Han; Chiu, Shih-Wen

    2011-01-01

    This study developed an electronic-nose sensor node based on a polymer-coated surface acoustic wave (SAW) sensor array. The sensor node comprised an SAW sensor array, a frequency readout circuit, and an Octopus II wireless module. The sensor array was fabricated on a large K2 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT) was produced with a Cr/Au film as its metallic structure. A mixed-mode frequency readout application specific integrated circuit (ASIC) was fabricated using a TSMC 0.18 μm process. The ASIC output was connected to a wireless module to transmit sensor data to a base station for data storage and analysis. This sensor node is applicable for wireless sensor network (WSN) applications. PMID:22163865

  6. An electronic-nose sensor node based on a polymer-coated surface acoustic wave array for wireless sensor network applications.

    PubMed

    Tang, Kea-Tiong; Li, Cheng-Han; Chiu, Shih-Wen

    2011-01-01

    This study developed an electronic-nose sensor node based on a polymer-coated surface acoustic wave (SAW) sensor array. The sensor node comprised an SAW sensor array, a frequency readout circuit, and an Octopus II wireless module. The sensor array was fabricated on a large K(2) 128° YX LiNbO3 sensing substrate. On the surface of this substrate, an interdigital transducer (IDT) was produced with a Cr/Au film as its metallic structure. A mixed-mode frequency readout application specific integrated circuit (ASIC) was fabricated using a TSMC 0.18 μm process. The ASIC output was connected to a wireless module to transmit sensor data to a base station for data storage and analysis. This sensor node is applicable for wireless sensor network (WSN) applications.

  7. Potentiometric flow injection system for determination of reductants using a polymeric membrane permanganate ion-selective electrode based on current-controlled reagent delivery.

    PubMed

    Song, Wenjing; Ding, Jiawang; Liang, Rongning; Qin, Wei

    2011-10-17

    A polymeric membrane permanganate-selective electrode has been developed as a current-controlled reagent release system for potentiometric detection of reductants in flow injection analysis. By applying an external current, diffusion of permanganate ions across the polymeric membrane can be controlled precisely. The permanganate ions released at the sample-membrane interface from the inner filling solution of the electrode are consumed by reaction with a reductant in the sample solution thus changing the measured membrane potential, by which the reductant can be sensed potentiometrically. Ascorbate, dopamine and norepinephrine have been employed as the model reductants. Under the optimized conditions, the potential peak heights are proportional to the reductant concentrations in the ranges of 1.0×10(-5) to 2.5×10(-7)M for ascorbate, of 1.0×10(-5) to 5.0×10(-7)M for dopamine, and of 1.0×10(-5) to 5.0×10(-7)M for norepinephrine, respectively with the corresponding detection limits of 7.8×10(-8), 1.0×10(-7) and 1.0×10(-7)M. The proposed system has been successfully applied to the determination of reductants in pharmaceutical preparations and vegetables, and the results agree well with those of iodimetric analysis. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. Augmenting the Senses: A Review on Sensor-Based Learning Support

    PubMed Central

    Schneider, Jan; Börner, Dirk; van Rosmalen, Peter; Specht, Marcus

    2015-01-01

    In recent years sensor components have been extending classical computer-based support systems in a variety of applications domains (sports, health, etc.). In this article we review the use of sensors for the application domain of learning. For that we analyzed 82 sensor-based prototypes exploring their learning support. To study this learning support we classified the prototypes according to the Bloom's taxonomy of learning domains and explored how they can be used to assist on the implementation of formative assessment, paying special attention to their use as feedback tools. The analysis leads to current research foci and gaps in the development of sensor-based learning support systems and concludes with a research agenda based on the findings. PMID:25679313

  9. Folding- and Dynamics-Based Electrochemical DNA Sensors.

    PubMed

    Lai, Rebecca Y

    2017-01-01

    A number of electrochemical DNA sensors based on the target-induced change in the conformation and/or flexibility of surface-bound oligonucleotides have been developed in recent years. These sensors, which are often termed E-DNA sensors, are comprised of an oligonucleotide probe modified with a redox label (e.g., methylene blue) at one terminus and attached to a gold electrode via a thiol-gold bond at the other. Binding of the target to the DNA probe changes its structure and dynamics, which, in turn, influences the efficiency of electron transfer to the interrogating electrode. Since electrochemically active contaminants are less common, these sensors are resistant to false-positive signals arising from the nonspecific adsorption of contaminants and perform well even when employed directly in serum, whole blood, and other realistically complex sample matrices. Moreover, because all of the sensor components are chemisorbed to the electrode, the E-DNA sensors are essentially label-free and readily reusable. To date, these sensors have achieved state-of-the-art sensitivity, while offering the unprecedented selectivity, reusability, and the operational convenience of direct electrochemical detection. This chapter reviews the recent advances in the development of both "signal-off" and "signal-on" E-DNA sensors. Critical aspects that dictate the stability and performance of these sensors are also addressed so as to provide a realistic overview of this oligonucleotide detection platform. © 2017 Elsevier Inc. All rights reserved.

  10. Wireless Sensor Network Based Subsurface Contaminant Plume Monitoring

    DTIC Science & Technology

    2012-04-16

    Sensor Network (WSN) to monitor contaminant plume movement in naturally heterogeneous subsurface formations to advance the sensor networking based...time to assess the source and predict future plume behavior. This proof-of-concept research aimed at demonstrating the use of an intelligent Wireless

  11. Research of marine sensor web based on SOA and EDA

    NASA Astrophysics Data System (ADS)

    Jiang, Yongguo; Dou, Jinfeng; Guo, Zhongwen; Hu, Keyong

    2015-04-01

    A great deal of ocean sensor observation data exists, for a wide range of marine disciplines, derived from in situ and remote observing platforms, in real-time, near-real-time and delayed mode. Ocean monitoring is routinely completed using sensors and instruments. Standardization is the key requirement for exchanging information about ocean sensors and sensor data and for comparing and combining information from different sensor networks. One or more sensors are often physically integrated into a single ocean `instrument' device, which often brings in many challenges related to diverse sensor data formats, parameters units, different spatiotemporal resolution, application domains, data quality and sensors protocols. To face these challenges requires the standardization efforts aiming at facilitating the so-called Sensor Web, which making it easy to provide public access to sensor data and metadata information. In this paper, a Marine Sensor Web, based on SOA and EDA and integrating the MBARI's PUCK protocol, IEEE 1451 and OGC SWE 2.0, is illustrated with a five-layer architecture. The Web Service layer and Event Process layer are illustrated in detail with an actual example. The demo study has demonstrated that a standard-based system can be built to access sensors and marine instruments distributed globally using common Web browsers for monitoring the environment and oceanic conditions besides marine sensor data on the Web, this framework of Marine Sensor Web can also play an important role in many other domains' information integration.

  12. A Bluetooth-Based Device Management Platform for Smart Sensor Environment

    NASA Astrophysics Data System (ADS)

    Lim, Ivan Boon-Kiat; Yow, Kin Choong

    In this paper, we propose the use of Bluetooth as the device management platform for the various embedded sensors and actuators in an ambient intelligent environment. We demonstrate the ease of adding Bluetooth capability to common sensor circuits (e.g. motion sensor circuit based on a pyroelectric infrared (PIR) sensor). A central logic application is proposed which controls the operation of controller devices, based on values returned by sensors via Bluetooth. The operation of devices depends on rules that are learnt from user behavior using an Elman recurrent neural network. Overall, Bluetooth has shown its potential in being used as a device management platform in an ambient intelligent environment, which allows sensors and controllers to be deployed even in locations where power sources are not readily available, by using battery power.

  13. Elements for successful sensor-based process control {Integrated Metrology}

    NASA Astrophysics Data System (ADS)

    Butler, Stephanie Watts

    1998-11-01

    Current productivity needs have stimulated development of alternative metrology, control, and equipment maintenance methods. Specifically, sensor applications provide the opportunity to increase productivity, tighten control, reduce scrap, and improve maintenance schedules and procedures. Past experience indicates a complete integrated solution must be provided for sensor-based control to be used successfully in production. In this paper, Integrated Metrology is proposed as the term for an integrated solution that will result in a successful application of sensors for process control. This paper defines and explores the perceived four elements of successful sensor applications: business needs, integration, components, and form. Based upon analysis of existing successful commercially available controllers, the necessary business factors have been determined to be strong, measurable industry-wide business needs whose solution is profitable and feasible. This paper examines why the key aspect of integration is the decision making process. A detailed discussion is provided of the components of most importance to sensor based control: decision-making methods, the 3R's of sensors, and connectivity. A metric for one of the R's (resolution) is proposed to allow focus on this important aspect of measurement. A form for these integrated components which synergistically partitions various aspects of control at the equipment and MES levels to efficiently achieve desired benefits is recommended.

  14. Ultrasensitive displacement sensor based on tunable horn-shaped resonators

    NASA Astrophysics Data System (ADS)

    Tian, Ying; Wu, Jiong; Yu, Le; Yang, Helin; Huang, Xiaojun

    2018-04-01

    In this paper, we proposed a novel double-deck displacement sensor with a high linearity based on tunable horn-shaped resonators. The designed sensor included two substrate layers etched with copper metallization in various shapes. When the upper trip-type resonator layer has a relative displacement to the bottom horn-shaped resonator layer, the resonance frequency of the sensor is redshift. High sensitivity of the sensor is around 207.2 MHz mm-1 with 4 mm linear dynamic range. We fabricate the sample of the proposed displacement sensor, in addition the simulated results are verified by experiment. The proposed displacement sensor is appropriate for using MEMS technology in further miniaturization.

  15. Plasmonic hydrogen sensor based on integrated microring resonator

    NASA Astrophysics Data System (ADS)

    Yi, Ya Sha; Wu, Da Chuan

    2017-12-01

    We have proposed and demonstrated numerically an ultrasmall and highly sensitive plasmonic hydrogen sensor based on an integrated microring resonator, with a footprint size as small as 4×4 μm2. With a palladium (Pd) or platinum (Pt) hydrogen-sensitive layer coated on the inner surface of the microring resonator and the excitation of surface plasmon modes at the interface from the microring resonator waveguide, the device is highly sensitive to low hydrogen concentration variation, and the sensitivity is at least one order of magnitude larger than that of the optical fiber-based hydrogen sensor. We have also investigated the tradeoff between the portion coverage of the Pd/Pt layer and the sensitivity, as well as the width of the hydrogen-sensitive layer. This ultrasmall plasmonic hydrogen sensor holds promise for the realization of a highly compact sensor with integration capability for applications in hydrogen fuel economy.

  16. SERS-based pesticide detection by using nanofinger sensors

    NASA Astrophysics Data System (ADS)

    Kim, Ansoon; Barcelo, Steven J.; Li, Zhiyong

    2015-01-01

    Simple, sensitive, and rapid detection of trace levels of extensively used and highly toxic pesticides are in urgent demand for public health. Surface-enhanced Raman scattering (SERS)-based sensor was designed to achieve ultrasensitive and simple pesticide sensing. We developed a portable sensor system composed of high performance and reliable gold nanofinger sensor strips and a custom-built portable Raman spectrometer. Compared to the general procedure and previously reported studies that are limited to laboratory settings, our analytical method is simple, sensitive, rapid, and cost-effective. Based on the SERS results, the chemical interaction of two pesticides, chlorpyrifos (CPF) and thiabendazole (TBZ), with gold nanofingers was studied to determine a fingerprint for each pesticide. The portable SERS-sensor system was successfully demonstrated to detect CPF and TBZ pesticides within 15 min with a detection limit of 35 ppt in drinking water and 7 ppb on apple skin, respectively.

  17. Hydrogeology, groundwater levels, and generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system, 2010–14, in the northern Green River structural basin

    USGS Publications Warehouse

    Bartos, Timothy T.; Hallberg, Laura L.; Eddy-Miller, Cheryl

    2015-07-14

    The groundwater-level measurements were used to construct a generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system. Groundwater-level altitudes measured in nonflowing and flowing wells used to construct the potentiometric-surface map ranged from 6,451 to 7,307 feet (excluding four unmeasured flowing wells used for contour construction purposes). The potentiometric-surface map indicates that groundwater in the study area generally moves from north to south, but this pattern of flow is altered locally by groundwater divides, groundwater discharge to the Green River, and possibly to a tributary river (Big Sandy River) and two reservoirs (Fontenelle and Big Sandy Reservoirs).

  18. Microcantilever sensor platform for UGV-based detection

    NASA Astrophysics Data System (ADS)

    Lawrence, Tyson T.; Halleck, A. E.; Schuler, Peter S.; Mahmud, K. K.; Hicks, David R.

    2010-04-01

    The increased use of Unmanned Ground Vehicles (UGVs) drives the need for new lightweight, low cost sensors. Microelectromechanical System (MEMS) based microcantilever sensors are a promising technology to meet this need, because they can be manufactured at low cost on a mass scale, and are easily integrated into a UGV platform for detection of explosives and other threat agents. While the technology is extremely sensitive, selectivity is a major challenge and the response modes are not well understood. This work summarizes advances in characterizing ultrasensitive microcantilever responses, sampling considerations, and sensor design and cantilever coating methodologies consistent with UGV point detector needs.

  19. Concentration determination of methyl magnesium chloride and other Grignard reagents by potentiometric titration with in-line characterization of reaction species by FTIR spectroscopy.

    PubMed

    Chen, Yadan; Wang, Tao; Helmy, Roy; Zhou, George X; LoBrutto, Rosario

    2002-07-01

    A potentiometric titration method for methyl magnesium chloride and other Grignard reagents based on the reaction with 2-butanol in THF has been developed and validated. The method employs a commercially available platinum electrode, using an electrolyte compatible with non-aqueous solvents. Well-defined titration curves were obtained, along with excellent method precision. The endpoint was precisely determined based on the first derivative of the titration curve. Different solvents such as THF, diethyl ether and methylene chloride provided similar results with regard to sharpness of the endpoint and method precision. The method was applied to a wide array of Grignard reagents including methyl magnesium bromide, ethyl magnesium chloride, propyl magnesium chloride, vinyl magnesium chloride, phenyl magnesium chloride, and benzyl magnesium chloride with similar precision and accuracy. Application of in-line FTIR was demonstrated for in situ monitoring of the titration reaction, allowing characterization of the reaction species. An authentic spectrum of the MeMgCl-THF complex was obtained using spectral subtraction and the vibrational absorbance bands were identified. FTIR also provided an alternative for detecting the titration endpoint, and the titration results so obtained, provided a cross-validation of the accuracy of the potentiometric titration.

  20. Plastic optical fiber level measurement sensor based on side holes

    NASA Astrophysics Data System (ADS)

    Park, Young June; Shin, Jong-Dug; Park, Jaehee

    2014-10-01

    Plastic optical fiber level measurement sensor based on in-line side holes is investigated theoretically and experimentally. The sensor consists of a plastic optical fiber with in-line side holes spaced about 5 cm apart. The 0.9 diameter in-line side holes were fabricated by micro-drilling. An analytical expression of the sensor transmittance was obtained using a simple ray optics approach. The measurements of the sensor transmittance were performed with a 55 cm height Mass cylinder. Both results show that the sensor transmittance increases as the number of side holes filled with water increases. The research results indicate that the plastic optical fiber based on in-line side holes can be used for water level measurement.

  1. Semiconductor nanomembrane-based sensors for high frequency pressure measurements

    NASA Astrophysics Data System (ADS)

    Ruan, Hang; Kang, Yuhong; Homer, Michelle; Claus, Richard O.; Mayo, David; Sibold, Ridge; Jones, Tyler; Ng, Wing

    2017-04-01

    This paper demonstrates improvements on semiconductor nanomembrane based high frequency pressure sensors that utilize silicon on insulator techniques in combination with nanocomposite materials. The low-modulus, conformal nanomembrane sensor skins with integrated interconnect elements and electronic devices could be applied to vehicles or wind tunnel models for full spectrum pressure analysis. Experimental data demonstrates that: 1) silicon nanomembrane may be used as single pressure sensor transducers and elements in sensor arrays, 2) the arrays may be instrumented to map pressure over the surfaces of test articles over a range of Reynolds numbers, temperature and other environmental conditions, 3) in the high frequency range, the sensor is comparable to the commercial high frequency sensor, and 4) in the low frequency range, the sensor is much better than the commercial sensor. This supports the claim that nanomembrane pressure sensors may be used for wide bandwidth flow analysis.

  2. A portable gas sensor based on cataluminescence.

    PubMed

    Kang, C; Tang, F; Liu, Y; Wu, Y; Wang, X

    2013-01-01

    We describe a portable gas sensor based on cataluminescence. Miniaturization of the gas sensor was achieved by using a miniature photomultiplier tube, a miniature gas pump and a simple light seal. The signal to noise ratio (SNR) was considered as the evaluation criteria for the design and testing of the sensor. The main source of noise was from thermal background. Optimal working temperature and flow rate were determined experimentally from the viewpoint of improvement in SNR. A series of parameters related to analytical performance was estimated. The limitation of detection of the sensor was 7 ppm (SNR = 3) for ethanol and 10 ppm (SNR = 3) for hydrogen sulphide. Zirconia and barium carbonate were respectively selected as nano-sized catalysts for ethanol and hydrogen sulphide. Copyright © 2012 John Wiley & Sons, Ltd.

  3. Wheel-Based Ice Sensors for Road Vehicles

    NASA Technical Reports Server (NTRS)

    Arndt, G. Dickey; Fink, Patrick W.; Ngo, Phong H.; Carl, James R.

    2011-01-01

    Wheel-based sensors for detection of ice on roads and approximate measurement of the thickness of the ice are under development. These sensors could be used to alert drivers to hazardous local icing conditions in real time. In addition, local ice-thickness measurements by these sensors could serve as guidance for the minimum amount of sand and salt required to be dispensed locally onto road surfaces to ensure safety, thereby helping road crews to utilize their total supplies of sand and salt more efficiently. Like some aircraft wing-surface ice sensors described in a number of previous NASA Tech Briefs articles, the wheelbased ice sensors are based, variously, on measurements of changes in capacitance and/or in radio-frequency impedance as affected by ice on surfaces. In the case of ice on road surfaces, the measurable changes in capacitance and/or impedance are attributable to differences among the electric permittivities of air, ice, water, concrete, and soil. In addition, a related phenomenon that can be useful for distinguishing between ice and water is a specific transition in the permittivity of ice at a temperature- dependent frequency. This feature also provides a continuous calibration of the sensor to allow for changing road conditions. Several configurations of wheel-based ice sensors are under consideration. For example, in a simple two-electrode capacitor configuration, one of the electrodes would be a circumferential electrode within a tire, and the ground would be used as the second electrode. Optionally, the steel belts that are already standard parts of many tires could be used as the circumferential electrodes. In another example (see figure), multiple electrodes would be embedded in rubber between the steel belt and the outer tire surface. These electrodes would be excited in alternating polarities at one or more suitable audio or radio frequencies to provide nearly continuous monitoring of the road surface under the tire. In still another

  4. Potentiometric surfaces of aquifers in the Cockfield Formation in southeastern Arkansas and the Wilcox Group in southern and northeastern Arkansas, 2000

    USGS Publications Warehouse

    Schrader, Tony P.; Joseph, Robert L.

    2000-01-01

    The Cockfield and lower Wilcox aquifers are sources of water for local use in southern and northeastern Arkansas, where in 1995 more than 51 million gallons per day of water was withdrawn. During January through April 2000, 54 water-level measurements were made in wells completed in the Cockfield aquifer, 13 water-level measurements were made in wells completed in the lower Wilcox aquifer in southern Arkansas, and 43 water-level measurements were made in wells completed in the lower Wilcox aquifer in northeastern Arkansas. The potentiometric surface data reveal spatial trends in both aquifers across the study areas. The regional direction of ground-water flow of the Cockfield aquifer is generally toward the east and south, away from the outcrop area, except in areas of intense ground-water withdrawals. The configuration of the potentiometric surface indicates that heavy pumpage has probably altered or reversed the natural direction of flow in these areas. A potentiometric low caused by the pumpage near Greenville, Mississippi, extends into Chicot, Desha, and Drew Counties. Water levels in five wells showed average declines between 0.5 and 0.8 foot per year. The regional direction of ground-water flow in the lower Wilcox aquifers is generally east and south, away from the outcrop, except in areas of intense ground-water withdrawals. Potentiometric depressions, where flow is toward centers of pumping, indicate that heavy pumpage has probably altered or reversed the natural direction of flow. Two potentiometric depressions are centered in the vicinity of Paragould and West Memphis, Arkansas, where ground-water withdrawals probably have altered the natural direction of flow. Long-term hydrographs of seven wells show water-level declines in the lower Wilcox aquifer in northeastern Arkansas. The average water-level decline in two wells was between 0.8 and 1.0 foot per year and in five wells was between 1.2 and 1.8 foot per year.

  5. Potentiometric glucose biosensor based on core-shell Fe3O4-enzyme-polypyrrole nanoparticles.

    PubMed

    Yang, Zhengpeng; Zhang, Chunjing; Zhang, Jianxin; Bai, Wanbei

    2014-01-15

    Core-shell Fe3O4-enzyme-polypyrrole (Ppy) nanoparticles with excellent magnetism and conductivity were successfully prepared via the surface modification and enzyme self-encapsulation within Ppy. A novel potentiometric glucose biosensor has been constructed by effectively attaching the proposed Fe3O4-enzyme-Ppy nanoparticles to the surface of the magnetic glassy carbon electrode (MGCE). The optimum biosensing conditions could be provided with polymerization time of pyrrole for 6h and 0.42 mg immobilization amount of Fe3O4-enzyme-Ppy nanoparticles on MGCE. The performance of the developed glucose biosensor was evaluated and the results indicated that a sensitive glucose biosensor could be fabricated. The obtained glucose biosensor presents shorter response time (6 s), wider linear range (0.5 μM to 34 mM), lower limit of detection (LOD, 0.3 μM), high-selectivity monitoring of glucose and good stability (with about 98.1% of the initial response signal retained after 20 days). The analytical application of the glucose biosensor confirms the feasibility of glucose detection in serum sample. © 2013 Elsevier B.V. All rights reserved.

  6. Pressure sensor based on the fiber-optic extrinsic Fabry-Perot interferometer

    NASA Astrophysics Data System (ADS)

    Yu, Qingxu; Zhou, Xinlei

    2011-03-01

    Pressure sensors based on fiber-optic extrinsic Fabry-Perot interferometer (EFPI) have been extensively applied in various industrial and biomedical fields. In this paper, some key improvements of EFPI-based pressure sensors such as the controlled thermal bonding technique, diaphragm-based EFPI sensors, and white light interference technology have been reviewed. Recent progress on signal demodulation method and applications of EFPI-based pressure sensors has been introduced. Signal demodulation algorithms based on the cross correlation and mean square error (MSE) estimation have been proposed for retrieving the cavity length of EFPI. Absolute measurement with a resolution of 0.08 nm over large dynamic range has been carried out. For downhole monitoring, an EFPI and a fiber Bragg grating (FBG) cascade multiplexing fiber-optic sensor system has been developed, which can operate in temperature 300 °C with a good long-term stability and extremely low temperature cross-sensitivity. Diaphragm-based EFPI pressure sensors have been successfully used for low pressure and acoustic wave detection. Experimental results show that a sensitivity of 31 mV/Pa in the frequency range of 100 Hz to 12.7 kHz for aeroacoustic wave detection has been obtained.

  7. A novel vibration sensor based on phase grating interferometry

    NASA Astrophysics Data System (ADS)

    Li, Qian; Liu, Xiaojun; Zhao, Li; Lei, Zili; Lu, Zhen; Guo, Lei

    2017-05-01

    Vibration sensors with high accuracy and reliability are needed urgently for vibration measurement. In this paper a vibration sensor with nanometer resolution is developed. This sensor is based on the principle of phase grating interference for displacement measurement and spatial polarization phase-shift interference technology, and photoelectric counting and A/D signal subdivision are adopted for vibration data output. A vibration measurement system consisting of vibration actuator and displacement adjusting device has been designed to test the vibration sensor. The high resolution and high reliability of the sensor are verified through a series of comparison experiments with Doppler interferometer.

  8. A carbon nanotube based ammonia sensor on cotton textile

    NASA Astrophysics Data System (ADS)

    Han, Jin-Woo; Kim, Beomseok; Li, Jing; Meyyappan, M.

    2013-05-01

    A single-wall carbon nanotube (CNT) based ammonia (NH3) sensor was implemented on a cotton yarn. Two types of sensors were fabricated: Au/sensing CNT/Au and conducting/sensing/conducting all CNT structures. Two perpendicular Au wires were designed to contact CNT-cotton yarn for metal-CNT sensor, whereas nanotubes were used for the electrode as well as sensing material for the all CNT sensor. The resistance shift of the CNT network upon NH3 was monitored in a chemiresistor approach. The CNT-cotton yarn sensors exhibited uniformity and repeatability. Furthermore, the sensors displayed good mechanical robustness against bending. The present approach can be utilized for low-cost smart textile applications.

  9. A model-based reasoning approach to sensor placement for monitorability

    NASA Technical Reports Server (NTRS)

    Chien, Steve; Doyle, Richard; Homemdemello, Luiz

    1992-01-01

    An approach is presented to evaluating sensor placements to maximize monitorability of the target system while minimizing the number of sensors. The approach uses a model of the monitored system to score potential sensor placements on the basis of four monitorability criteria. The scores can then be analyzed to produce a recommended sensor set. An example from our NASA application domain is used to illustrate our model-based approach to sensor placement.

  10. Triple-helix molecular switch-based aptasensors and DNA sensors.

    PubMed

    Bagheri, Elnaz; Abnous, Khalil; Alibolandi, Mona; Ramezani, Mohammad; Taghdisi, Seyed Mohammad

    2018-07-15

    Utilization of traditional analytical techniques is limited because they are generally time-consuming and require high consumption of reagents, complicated sample preparation and expensive equipment. Therefore, it is of great interest to achieve sensitive, rapid and simple detection methods. It is believed that nucleic acids assays, especially aptamers, are very important in modern life sciences for target detection and biological analysis. Aptamers and DNA-based sensors have been widely used for the design of various sensors owing to their unique features. In recent years, triple-helix molecular switch (THMS)-based aptasensors and DNA sensors have been broadly utilized for the detection and analysis of different targets. The THMS relies on the formation of DNA triplex via Watson-Crick and Hoogsteen base pairings under optimal conditions. This review focuses on recent progresses in the development and applications of electrochemical, colorimetric, fluorescence and SERS aptasensors and DNA sensors, which are based on THMS. Also, the advantages and drawbacks of these methods are discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Gas Sensors Based on Semiconducting Metal Oxide One-Dimensional Nanostructures

    PubMed Central

    Huang, Jin; Wan, Qing

    2009-01-01

    This article provides a comprehensive review of recent (2008 and 2009) progress in gas sensors based on semiconducting metal oxide one-dimensional (1D) nanostructures. During last few years, gas sensors based on semiconducting oxide 1D nanostructures have been widely investigated. Additionally, modified or doped oxide nanowires/nanobelts have also been synthesized and used for gas sensor applications. Moreover, novel device structures such as electronic noses and low power consumption self-heated gas sensors have been invented and their gas sensing performance has also been evaluated. Finally, we also point out some challenges for future investigation and practical application. PMID:22303154

  12. Illumination-based synchronization of high-speed vision sensors.

    PubMed

    Hou, Lei; Kagami, Shingo; Hashimoto, Koichi

    2010-01-01

    To acquire images of dynamic scenes from multiple points of view simultaneously, the acquisition time of vision sensors should be synchronized. This paper describes an illumination-based synchronization method derived from the phase-locked loop (PLL) algorithm. Incident light to a vision sensor from an intensity-modulated illumination source serves as the reference signal for synchronization. Analog and digital computation within the vision sensor forms a PLL to regulate the output signal, which corresponds to the vision frame timing, to be synchronized with the reference. Simulated and experimental results show that a 1,000 Hz frame rate vision sensor was successfully synchronized with 32 μs jitters.

  13. Space-based sensor management and geostationary satellites tracking

    NASA Astrophysics Data System (ADS)

    El-Fallah, A.; Zatezalo, A.; Mahler, R.; Mehra, R. K.; Donatelli, D.

    2007-04-01

    Sensor management for space situational awareness presents a daunting theoretical and practical challenge as it requires the use of multiple types of sensors on a variety of platforms to ensure that the space environment is continuously monitored. We demonstrate a new approach utilizing the Posterior Expected Number of Targets (PENT) as the sensor management objective function, an observation model for a space-based EO/IR sensor platform, and a Probability Hypothesis Density Particle Filter (PHD-PF) tracker. Simulation and results using actual Geostationary Satellites are presented. We also demonstrate enhanced performance by applying the ProgressiveWeighting Correction (PWC) method for regularization in the implementation of the PHD-PF tracker.

  14. Potentiometric surface and specific conductance of the Sparta and Memphis aquifers in eastern Arkansas, 1995

    USGS Publications Warehouse

    Stanton, Gregory P.

    1997-01-01

    The Sparta and Memphis aquifers in eastern and south-central Arkansas are a major source of water for industrial, public supply, and agricultural uses. An estimated 240 million gallons per day was withdrawn from the Sparta and Memphis aquifers in 1995, an increase of about 17 million gallons per day from 1990. During the spring and early summer of 1995, the water level in the Sparta and Memphis aquifers was measured in 145 wells, the specific conductance of 101 ground-water samples collected from those aquifers was measured. Maps of areal distribution of potentiometric surface and specific conductance generated from these data reveal spatial trends in these parameters across the eastern and south-central Arkansas study area. The altitude of the potentiometric surface ranged from about 206 feet below sea level in Union County to about 307 feet above sea level in Saline County. The potentiometric surface of the Sparta and Memphis aquifers contains cones of depression descending below sea level in the central and southern portions of the study area, and a potentiometric high along the western study area boundary. Major recharge areas exhibit potentiometric highs greater than 200 feet above sea level and specific conductance values less than 200 microsiemens per centimeter, and generally are located in the outcrop/subcrop areas on the southern one-third of the western boundary and the northern portion of the study area. The regional direction of ground-water flow is from the north and west to the south and east, away from the outcrop and subcrop and northern regions, except near areas affected by intense ground-water withdrawals; such areas are manifested by large cones of depression centered in Columbia, Jefferson, and Union Counties. The cones of depression in adjoining Columbia and Union Counties are coalescing at or near sea level. The lowest water level measured was about 206 feet below sea level in Union County. Increased specific conductance values were measured

  15. Estimated 2012 groundwater potentiometric surface and drawdown from predevelopment to 2012 in the Santa Fe Group aquifer system in the Albuquerque metropolitan area, central New Mexico

    USGS Publications Warehouse

    Powell, Rachel I.; McKean, Sarah E.

    2014-01-01

    Historically, the water-supply requirements of the Albuquerque metropolitan area of central New Mexico were met almost exclusively by groundwater withdrawal from the Santa Fe Group aquifer system. In response to water-level declines, the Albuquerque Bernalillo County Water Utility Authority (ABCWUA) began diverting water from the San Juan-Chama Drinking Water Project in December 2008 to reduce the use of groundwater to meet municipal demand. Modifications in the demand for water and the source of the supply of water for the Albuquerque metropolitan area have resulted in a variable response in the potentiometric surface of the production zone (the interval of the aquifer, from within about 200 feet below the water table to 900 feet or more, in which supply wells generally are screened) of the Santa Fe Group aquifer system. Analysis of the magnitude and spatial distribution of water-level change can help improve the understanding of how the groundwater system responds to withdrawals and variations in the management of the water supply and can support water-management agencies’ efforts to minimize future water-level declines and improve sustainability. The U.S. Geological Survey (USGS), in cooperation with the ABCWUA, has developed an estimate of the 2012 potentiometric surface of the production zone of the Santa Fe Group aquifer system in the Albuquerque metropolitan area. This potentiometric surface is the latest in a series of reports depicting the potentiometric surface of the area. This report presents the estimated potentiometric surface during winter (from December to March) of water year 2012 and the estimated changes in potentiometric surface between predevelopment (pre-1961) and water year 2012 for the production zone of the Santa Fe Group aquifer system in the Albuquerque metropolitan area. Hydrographs from selected piezometers are included to provide details of historical water-level changes. In general, water-level measurements used for this report were

  16. SiC-Based Schottky Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Neudeck, Philip G.; Chen, Liang-Yu; Knight, Dak; Liu, Chung-Chiun; Wu, Quing-Hai

    1997-01-01

    Silicon carbide based Schottky diode gas sensors are being developed for high temperature applications such as emission measurements. Two different types of gas sensitive diodes will be discussed in this paper. By varying the structure of the diode, one can affect the diode stability as well as the diode sensitivity to various gases. It is concluded that the ability of SiC to operate as a high temperature semiconductor significantly enhances the versatility of the Schottky diode gas sensing structure and will potentially allow the fabrication of a SiC-based gas sensor arrays for versatile high temperature gas sensing applications.

  17. Pheromone-based coordination strategy to static sensors on the ground and unmanned aerial vehicles carried sensors

    NASA Astrophysics Data System (ADS)

    Pignaton de Freitas, Edison; Heimfarth, Tales; Pereira, Carlos Eduardo; Morado Ferreira, Armando; Rech Wagner, Flávio; Larsson, Tony

    2010-04-01

    A current trend that is gaining strength in the wireless sensor network area is the use of heterogeneous sensor nodes in one coordinated overall network, needed to fulfill the requirements of sophisticated emerging applications, such as area surveillance systems. One of the main concerns when developing such sensor networks is how to provide coordination among the heterogeneous nodes, in order to enable them to efficiently respond the user needs. This study presents an investigation of strategies to coordinate a set of static sensor nodes on the ground cooperating with wirelessly connected Unmanned Aerial Vehicles (UAVs) carrying a variety of sensors, in order to provide efficient surveillance over an area of interest. The sensor nodes on the ground are set to issue alarms on the occurrence of a given event of interest, e.g. entrance of a non-authorized vehicle in the area, while the UAVs receive the issued alarms and have to decide which of them is the most suitable to handle the issued alarm. A bio-inspired coordination strategy based on the concept of pheromones is presented. As a complement of this strategy, a utility-based decision making approach is proposed.

  18. Standards-Based Wireless Sensor Networking Protocols for Spaceflight Applications

    NASA Technical Reports Server (NTRS)

    Wagner, Raymond S.

    2010-01-01

    Wireless sensor networks (WSNs) have the capacity to revolutionize data gathering in both spaceflight and terrestrial applications. WSNs provide a huge advantage over traditional, wired instrumentation since they do not require wiring trunks to connect sensors to a central hub. This allows for easy sensor installation in hard to reach locations, easy expansion of the number of sensors or sensing modalities, and reduction in both system cost and weight. While this technology offers unprecedented flexibility and adaptability, implementing it in practice is not without its difficulties. Recent advances in standards-based WSN protocols for industrial control applications have come a long way to solving many of the challenges facing practical WSN deployments. In this paper, we will overview two of the more promising candidates - WirelessHART from the HART Communication Foundation and ISA100.11a from the International Society of Automation - and present the architecture for a new standards-based sensor node for networking and applications research.

  19. CMOS image sensor-based immunodetection by refractive-index change.

    PubMed

    Devadhasan, Jasmine P; Kim, Sanghyo

    2012-01-01

    A complementary metal oxide semiconductor (CMOS) image sensor is an intriguing technology for the development of a novel biosensor. Indeed, the CMOS image sensor mechanism concerning the detection of the antigen-antibody (Ag-Ab) interaction at the nanoscale has been ambiguous so far. To understand the mechanism, more extensive research has been necessary to achieve point-of-care diagnostic devices. This research has demonstrated a CMOS image sensor-based analysis of cardiovascular disease markers, such as C-reactive protein (CRP) and troponin I, Ag-Ab interactions on indium nanoparticle (InNP) substrates by simple photon count variation. The developed sensor is feasible to detect proteins even at a fg/mL concentration under ordinary room light. Possible mechanisms, such as dielectric constant and refractive-index changes, have been studied and proposed. A dramatic change in the refractive index after protein adsorption on an InNP substrate was observed to be a predominant factor involved in CMOS image sensor-based immunoassay.

  20. Synthesis, spectral characterization, molecular modeling, biological activity and potentiometric studies of 4-amino-5-mercapto-3-methyl-S-triazole Schiff's base complexes

    NASA Astrophysics Data System (ADS)

    Alaghaz, Abdel-Nasser M. A.; Zayed, Mohamed E.; Alharbi, Suliman A.

    2015-03-01

    The Schiff's base derived from condensation of s-triazole (4-amino-5-mercapto-3-methyl-S-triazole) with pyridine-2-aldehyde and their corresponding Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes have been synthesized. The isolated solid complexes were characterized by elemental analyses, molar conductance, spectral (IR, UV-Vis, 1H NMR, mass), magnetic moment and thermal measurements. The IR spectral data suggest that the ligand coordinate in a tridentate manner (SNN) via the one thiol (SH), one pyridine ring and the azomethine (Cdbnd N) groups. The data show that the complexes have composition of ML2 type. The activation of thermodynamic parameters are calculated using Coats-Redfern, Horowitz-Metzger (HM), and Piloyan-Novikova (PN). The octahedral geometry of the complexes is confirmed using DFT method from DMOL3 calculations and ligand field parameters. Protonation constants of Schiff base and stability constants of their binary metal complexes have been determined potentiometrically in 50% DMSO-water media at 25 °C and ionic strength 0.10 M potassium nitrate. The biological activity of these compounds against various fungi has been investigated.

  1. Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 2002

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Wheeler, Judith C.

    2003-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2002. The map is based on water-level measurements in 94 wells. The highest measured water level was 38 feet above sea level near the northern boundary and outcrop area of the aquifer in the central part of Anne Arundel County, and was below sea level just south of this area and in the remainder of the study area. The hydraulic gradient increased southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. Another cone of depression occurred in northern Calvert County due to pumpage at and near Chesapeake Beach and North Beach. The water level measured in this area has declined to 55 feet below sea level. The lowest water level measured was 169 feet below sea level at the center of a cone of depression at Lexington Park.

  2. Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 2009

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W.

    2010-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2009. The map is based on water-level measurements in 82 wells. The highest measured water level was 48 feet above sea level near the northern boundary and in the outcrop area of the aquifer in the central part of Anne Arundel County. Water levels also were above sea level in Kent County and northern Queen Anne's County. Water levels were below sea level south and east of these areas and in the remainder of the study area. The hydraulic gradient increased southeastward toward a cone of depression around well fields at Lexington Park and Solomons Island. The lowest measured water level was 145 feet below sea level at the center of a cone of depression at Lexington Park. The map also shows well yield in gallons per day for 2008 at wells or well fields.

  3. Potentiometric surface of the Aquia Aquifer in southern Maryland, September 2003

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreason, David C.; Wheeler, Judith C.

    2005-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2003. The map is based on water-level measurements in 91 wells. The highest measured water level was 40 feet above sea level near the northern boundary and outcrop area of the aquifer in the central part of Anne Arundel County, and was below sea level just south of this area and in the remainder of the study area. The hydraulic gradient increased southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. Another cone of depression occurred in northern Calvert County due to pumpage at and near North Beach and Chesapeake Beach. The water level measured in this area has declined to 48 feet below sea level. The lowest water level measured was 156 feet below sea level at the center of a cone of depression at Lexington Park.

  4. An immunity-based anomaly detection system with sensor agents.

    PubMed

    Okamoto, Takeshi; Ishida, Yoshiteru

    2009-01-01

    This paper proposes an immunity-based anomaly detection system with sensor agents based on the specificity and diversity of the immune system. Each agent is specialized to react to the behavior of a specific user. Multiple diverse agents decide whether the behavior is normal or abnormal. Conventional systems have used only a single sensor to detect anomalies, while the immunity-based system makes use of multiple sensors, which leads to improvements in detection accuracy. In addition, we propose an evaluation framework for the anomaly detection system, which is capable of evaluating the differences in detection accuracy between internal and external anomalies. This paper focuses on anomaly detection in user's command sequences on UNIX-like systems. In experiments, the immunity-based system outperformed some of the best conventional systems.

  5. Novel ammonia sensor based on polyaniline/polylactic acid composite films

    NASA Astrophysics Data System (ADS)

    Sotirov, S.; Bodurov, I.; Marudova, M.

    2017-01-01

    We propose a new type of ammonia sensor based on composite film between polyaniline (emeraldine base) dissolved in dimethylformamide, and poly(DL-lactic) acid dissolved in chloroform. The two solutions were mixed in weight ratio of the components 1:1 and cast on Al2O3 substrate, on which silver electrodes were deposited previously. The active layer structure and morphology were examined by atomic force microscopy. The sensor resistance at constant humidity and different ammonia concentrations was measured. It was found that an increase in the ammonia concentration leads to resistance increase. This result is explained in the terms of ionic interactions between the polyaniline and the ammonia, which change the permittivity of the sensor active media. A response between 2% and 590% was shown depending on the ammonia concentration. The sensor is reversible and possesses response time of typically 100 s. Based on the changes of the sensor resistance, ammonia concentration from 10 ppm to 1000 ppm could be detected.

  6. Highly sensitive wearable strain sensor based on silver nanowires and nanoparticles.

    PubMed

    Shengbo, Sang; Lihua, Liu; Aoqun, Jian; Qianqian, Duan; Jianlong, Ji; Qiang, Zhang; Wendong, Zhang

    2018-06-22

    Here, we propose a highly sensitive and stretchable strain sensor based on silver nanoparticles and nanowires (Ag NPs and NWs), advancing the rapid development of electronic skin. To improve the sensitivity of strain sensors based on silver nanowires (Ag NWs), Ag NPs and NWs were added to polydimethylsiloxane (PDMS) as an aid filler. Silver nanoparticles (Ag NPs) increase the conductive paths for electrons, leading to the low resistance of the resulting sensor (14.9 Ω). The strain sensor based on Ag NPs and NWs showed strong piezoresistivity with a tunable gauge factor (GF) at 3766, and a change in resistance as the strain linearly increased from 0% to 28.1%. The high GF demonstrates the irreplaceable role of Ag NPs in the sensor. Moreover, the applicability of our high-performance strain sensor has been demonstrated by its ability to sense movements caused by human talking, finger bending, wrist raising and walking.

  7. The Coverage Problem in Video-Based Wireless Sensor Networks: A Survey

    PubMed Central

    Costa, Daniel G.; Guedes, Luiz Affonso

    2010-01-01

    Wireless sensor networks typically consist of a great number of tiny low-cost electronic devices with limited sensing and computing capabilities which cooperatively communicate to collect some kind of information from an area of interest. When wireless nodes of such networks are equipped with a low-power camera, visual data can be retrieved, facilitating a new set of novel applications. The nature of video-based wireless sensor networks demands new algorithms and solutions, since traditional wireless sensor networks approaches are not feasible or even efficient for that specialized communication scenario. The coverage problem is a crucial issue of wireless sensor networks, requiring specific solutions when video-based sensors are employed. In this paper, it is surveyed the state of the art of this particular issue, regarding strategies, algorithms and general computational solutions. Open research areas are also discussed, envisaging promising investigation considering coverage in video-based wireless sensor networks. PMID:22163651

  8. Highly sensitive wearable strain sensor based on silver nanowires and nanoparticles

    NASA Astrophysics Data System (ADS)

    Shengbo, Sang; Lihua, Liu; Aoqun, Jian; Qianqian, Duan; Jianlong, Ji; Qiang, Zhang; Wendong, Zhang

    2018-06-01

    Here, we propose a highly sensitive and stretchable strain sensor based on silver nanoparticles and nanowires (Ag NPs and NWs), advancing the rapid development of electronic skin. To improve the sensitivity of strain sensors based on silver nanowires (Ag NWs), Ag NPs and NWs were added to polydimethylsiloxane (PDMS) as an aid filler. Silver nanoparticles (Ag NPs) increase the conductive paths for electrons, leading to the low resistance of the resulting sensor (14.9 Ω). The strain sensor based on Ag NPs and NWs showed strong piezoresistivity with a tunable gauge factor (GF) at 3766, and a change in resistance as the strain linearly increased from 0% to 28.1%. The high GF demonstrates the irreplaceable role of Ag NPs in the sensor. Moreover, the applicability of our high-performance strain sensor has been demonstrated by its ability to sense movements caused by human talking, finger bending, wrist raising and walking.

  9. Towards the development of tamper-resistant, ground-based mobile sensor nodes

    NASA Astrophysics Data System (ADS)

    Mascarenas, David; Stull, Christopher; Farrar, Charles

    2011-11-01

    Mobile sensor nodes hold great potential for collecting field data using fewer resources than human operators would require and potentially requiring fewer sensors than a fixed-position sensor array. It would be very beneficial to allow these mobile sensor nodes to operate unattended with a minimum of human intervention. In order to allow mobile sensor nodes to operate unattended in a field environment, it is imperative that they be capable of identifying and responding to external agents that may attempt to tamper with, damage or steal the mobile sensor nodes, while still performing their data collection mission. Potentially hostile external agents could include animals, other mobile sensor nodes, or humans. This work will focus on developing control policies to help enable a mobile sensor node to identify and avoid capture by a hostile un-mounted human. The work is developed in a simulation environment, and demonstrated using a non-holonomic, ground-based mobile sensor node. This work will be a preliminary step toward ensuring the cyber-physical security of ground-based mobile sensor nodes that operate unattended in potentially unfriendly environments.

  10. Aptamer based electrochemical sensors for emerging environmental pollutants

    NASA Astrophysics Data System (ADS)

    Hayat, Akhtar; Marty, Jean Louis

    2014-06-01

    Environmental contaminants monitoring is one of the key issues in understanding and managing hazards to human health and ecosystems. In this context, aptamer based electrochemical sensors have achieved intense significance because of their capability to resolve a potentially large number of problems and challenges in environmental contamination. An aptasensor is a compact analytical device incorporating an aptamer (oligonulceotide) as the sensing element either integrated within or intimately associated with a physiochemical transducer surface. Nucleic acid is well known for the function of carrying and passing genetic information, however, it has found a key role in analytical monitoring during recent years. Aptamer based sensors represent a novelty in environmental analytical science and there are great expectations for their promising performance as alternative to conventional analytical tools. This review paper focuses on the recent advances in the development of aptamer based electrochemical sensors for environmental applications with special emphasis on emerging pollutants.

  11. Sensor fusion for structural tilt estimation using an acceleration-based tilt sensor and a gyroscope

    NASA Astrophysics Data System (ADS)

    Liu, Cheng; Park, Jong-Woong; Spencer, B. F., Jr.; Moon, Do-Soo; Fan, Jiansheng

    2017-10-01

    A tilt sensor can provide useful information regarding the health of structural systems. Most existing tilt sensors are gravity/acceleration based and can provide accurate measurements of static responses. However, for dynamic tilt, acceleration can dramatically affect the measured responses due to crosstalk. Thus, dynamic tilt measurement is still a challenging problem. One option is to integrate the output of a gyroscope sensor, which measures the angular velocity, to obtain the tilt; however, problems arise because the low-frequency sensitivity of the gyroscope is poor. This paper proposes a new approach to dynamic tilt measurements, fusing together information from a MEMS-based gyroscope and an acceleration-based tilt sensor. The gyroscope provides good estimates of the tilt at higher frequencies, whereas the acceleration measurements are used to estimate the tilt at lower frequencies. The Tikhonov regularization approach is employed to fuse these measurements together and overcome the ill-posed nature of the problem. The solution is carried out in the frequency domain and then implemented in the time domain using FIR filters to ensure stability. The proposed method is validated numerically and experimentally to show that it performs well in estimating both the pseudo-static and dynamic tilt measurements.

  12. Electrochemical Sensors and Biosensors Based on Nanomaterials and Nanostructures

    DOE PAGES

    Zhu, Chengzhou; Yang, Guohai; Li, He; ...

    2014-10-29

    We report that considerable attention has been devoted to the integration of recognition elements with electronic elements to develop electrochemical sensors and biosensors.Various electrochemical devices, such as amperometric sensors, electrochemical impedance sensors, and electrochemical luminescence sensors as well as photoelectrochemical sensors, provide wide applications in the detection of chemical and biological targets in terms of electrochemical change of electrode interfaces. Here, this review focuses on recent advances in electrochemical sensors and biosensors based on nanomaterials and nanostructures during 2013 to 2014. The aim of this effort is to provide the reader with a clear and concise view of new advancesmore » in areas ranging from electrode engineering, strategies for electrochemical signal amplification, and novel electroanalytical techniques used in the miniaturization and integration of the sensors. Moreover, the authors have attempted to highlight areas of the latest and significant development of enhanced electrochemical nanosensors and nanobiosensors that inspire broader interests across various disciplines. Electrochemical sensors for small molecules, enzyme-based biosensors, genosensors, immunosensors, and cytosensors are reviewed herein (Figure 1). Such novel advances are important for the development of electrochemical sensors that open up new avenues and methods for future research. In conclusion, we recommend readers interested in the general principles of electrochemical sensors and electrochemical methods to refer to other excellent literature for a broad scope in this area.(3, 4) However, due to the explosion of publications in this active field, we do not claim that this Review includes all of the published works in the past two years and we apologize to the authors of excellent work, which is unintentionally left out.« less

  13. Toward CMOS image sensor based glucose monitoring.

    PubMed

    Devadhasan, Jasmine Pramila; Kim, Sanghyo

    2012-09-07

    Complementary metal oxide semiconductor (CMOS) image sensor is a powerful tool for biosensing applications. In this present study, CMOS image sensor has been exploited for detecting glucose levels by simple photon count variation with high sensitivity. Various concentrations of glucose (100 mg dL(-1) to 1000 mg dL(-1)) were added onto a simple poly-dimethylsiloxane (PDMS) chip and the oxidation of glucose was catalyzed with the aid of an enzymatic reaction. Oxidized glucose produces a brown color with the help of chromogen during enzymatic reaction and the color density varies with the glucose concentration. Photons pass through the PDMS chip with varying color density and hit the sensor surface. Photon count was recognized by CMOS image sensor depending on the color density with respect to the glucose concentration and it was converted into digital form. By correlating the obtained digital results with glucose concentration it is possible to measure a wide range of blood glucose levels with great linearity based on CMOS image sensor and therefore this technique will promote a convenient point-of-care diagnosis.

  14. Towards Scalable Strain Gauge-Based Joint Torque Sensors

    PubMed Central

    D’Imperio, Mariapaola; Cannella, Ferdinando; Caldwell, Darwin G.; Cuschieri, Alfred

    2017-01-01

    During recent decades, strain gauge-based joint torque sensors have been commonly used to provide high-fidelity torque measurements in robotics. Although measurement of joint torque/force is often required in engineering research and development, the gluing and wiring of strain gauges used as torque sensors pose difficulties during integration within the restricted space available in small joints. The problem is compounded by the need for a scalable geometric design to measure joint torque. In this communication, we describe a novel design of a strain gauge-based mono-axial torque sensor referred to as square-cut torque sensor (SCTS), the significant features of which are high degree of linearity, symmetry, and high scalability in terms of both size and measuring range. Most importantly, SCTS provides easy access for gluing and wiring of the strain gauges on sensor surface despite the limited available space. We demonstrated that the SCTS was better in terms of symmetry (clockwise and counterclockwise rotation) and more linear. These capabilities have been shown through finite element modeling (ANSYS) confirmed by observed data obtained by load testing experiments. The high performance of SCTS was confirmed by studies involving changes in size, material and/or wings width and thickness. Finally, we demonstrated that the SCTS can be successfully implementation inside the hip joints of miniaturized hydraulically actuated quadruped robot-MiniHyQ. This communication is based on work presented at the 18th International Conference on Climbing and Walking Robots (CLAWAR). PMID:28820446

  15. Towards Scalable Strain Gauge-Based Joint Torque Sensors.

    PubMed

    Khan, Hamza; D'Imperio, Mariapaola; Cannella, Ferdinando; Caldwell, Darwin G; Cuschieri, Alfred; Semini, Claudio

    2017-08-18

    During recent decades, strain gauge-based joint torque sensors have been commonly used to provide high-fidelity torque measurements in robotics. Although measurement of joint torque/force is often required in engineering research and development, the gluing and wiring of strain gauges used as torque sensors pose difficulties during integration within the restricted space available in small joints. The problem is compounded by the need for a scalable geometric design to measure joint torque. In this communication, we describe a novel design of a strain gauge-based mono-axial torque sensor referred to as square-cut torque sensor (SCTS) , the significant features of which are high degree of linearity, symmetry, and high scalability in terms of both size and measuring range. Most importantly, SCTS provides easy access for gluing and wiring of the strain gauges on sensor surface despite the limited available space. We demonstrated that the SCTS was better in terms of symmetry (clockwise and counterclockwise rotation) and more linear. These capabilities have been shown through finite element modeling (ANSYS) confirmed by observed data obtained by load testing experiments. The high performance of SCTS was confirmed by studies involving changes in size, material and/or wings width and thickness. Finally, we demonstrated that the SCTS can be successfully implementation inside the hip joints of miniaturized hydraulically actuated quadruped robot- MiniHyQ . This communication is based on work presented at the 18th International Conference on Climbing and Walking Robots (CLAWAR).

  16. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2006

    USGS Publications Warehouse

    Ortiz, A.G.

    2007-01-01

    Introduction Hydrologic Conditions in West-Central Florida The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2006. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 50.23 inches for west-central Florida (from June 2005 through May 2006) was 2.82 inches below the historical cumulative average of 53.05 inches (Southwest Florida Water Management District, 2006). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water

  17. Fabrication of strain gauge based sensors for tactile skins

    NASA Astrophysics Data System (ADS)

    Baptist, Joshua R.; Zhang, Ruoshi; Wei, Danming; Saadatzi, Mohammad Nasser; Popa, Dan O.

    2017-05-01

    Fabricating cost effective, reliable and functional sensors for electronic skins has been a challenging undertaking for the last several decades. Application of such skins include haptic interfaces, robotic manipulation, and physical human-robot interaction. Much of our recent work has focused on producing compliant sensors that can be easily formed around objects to sense normal, tension, or shear forces. Our past designs have involved the use of flexible sensors and interconnects fabricated on Kapton substrates, and piezoresistive inks that are 3D printed using Electro Hydro Dynamic (EHD) jetting onto interdigitated electrode (IDE) structures. However, EHD print heads require a specialized nozzle and the application of a high-voltage electric field; for which, tuning process parameters can be difficult based on the choice of inks and substrates. Therefore, in this paper we explore sensor fabrication techniques using a novel wet lift-off photolithographic technique for patterning the base polymer piezoresistive material, specifically Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) or PEDOT:PSS. Fabricated sensors are electrically and thermally characterized, and temperaturecompensated designs are proposed and validated. Packaging techniques for sensors in polymer encapsulants are proposed and demonstrated to produce a tactile interface device for a robot.

  18. Laser-based sensors for oil spill remote sensing

    NASA Astrophysics Data System (ADS)

    Brown, Carl E.; Fingas, Mervin F.; Mullin, Joseph V.

    1997-07-01

    Remote sensing is becoming an increasingly important tool for the effective direction of oil spill countermeasures. Cleanup personnel have recognized that remote sensing can increase spill cleanup efficiency. It has long been recognized that there is no one sensor which is capable of detecting oil and related petroleum products in all environments and spill scenarios. There are sensors which possess a wide field-of- view and can therefore be used to map the overall extent of the spill. These sensors, however lack the capability to positively identify oil and related products, especially along complicated beach and shoreline environments where several substrates are present. The laser-based sensors under development by the Emergencies Science Division of Environment Canada are designed to fill specific roles in oil spill response. The scanning laser environmental airborne fluorosensor (SLEAF) is being developed to detect and map oil and related petroleum products in complex marine and shoreline environments where other non-specific sensors experience difficulty. The role of the SLEAF would be to confirm or reject suspected oil contamination sites that have been targeted by the non-specific sensors. This confirmation will release response crews from the time-consuming task of physically inspecting each site, and direct crews to sites that require remediation. The laser ultrasonic remote sensing of oil thickness (LURSOT) sensor will provide an absolute measurement of oil thickness from an airborne platform. There are presently no sensors available, either airborne or in the laboratory which can provide an absolute measurement of oil thickness. This information is necessary for the effective direction of spill countermeasures such as dispersant application and in-situ burning. This paper describes the development of laser-based airborne oil spill remote sensing instrumentation at Environment Canada and identifies the anticipated benefits of the use of this technology

  19. Potential use of ground-based sensor technologies for weed detection.

    PubMed

    Peteinatos, Gerassimos G; Weis, Martin; Andújar, Dionisio; Rueda Ayala, Victor; Gerhards, Roland

    2014-02-01

    Site-specific weed management is the part of precision agriculture (PA) that tries to effectively control weed infestations with the least economical and environmental burdens. This can be achieved with the aid of ground-based or near-range sensors in combination with decision rules and precise application technologies. Near-range sensor technologies, developed for mounting on a vehicle, have been emerging for PA applications during the last three decades. These technologies focus on identifying plants and measuring their physiological status with the aid of their spectral and morphological characteristics. Cameras, spectrometers, fluorometers and distance sensors are the most prominent sensors for PA applications. The objective of this article is to describe-ground based sensors that have the potential to be used for weed detection and measurement of weed infestation level. An overview of current sensor systems is presented, describing their concepts, results that have been achieved, already utilized commercial systems and problems that persist. A perspective for the development of these sensors is given. © 2013 Society of Chemical Industry.

  20. Image-Based Environmental Monitoring Sensor Application Using an Embedded Wireless Sensor Network

    PubMed Central

    Paek, Jeongyeup; Hicks, John; Coe, Sharon; Govindan, Ramesh

    2014-01-01

    This article discusses the experiences from the development and deployment of two image-based environmental monitoring sensor applications using an embedded wireless sensor network. Our system uses low-power image sensors and the Tenet general purpose sensing system for tiered embedded wireless sensor networks. It leverages Tenet's built-in support for reliable delivery of high rate sensing data, scalability and its flexible scripting language, which enables mote-side image compression and the ease of deployment. Our first deployment of a pitfall trap monitoring application at the James San Jacinto Mountain Reserve provided us with insights and lessons learned into the deployment of and compression schemes for these embedded wireless imaging systems. Our three month-long deployment of a bird nest monitoring application resulted in over 100,000 images collected from a 19-camera node network deployed over an area of 0.05 square miles, despite highly variable environmental conditions. Our biologists found the on-line, near-real-time access to images to be useful for obtaining data on answering their biological questions. PMID:25171121

  1. Image-based environmental monitoring sensor application using an embedded wireless sensor network.

    PubMed

    Paek, Jeongyeup; Hicks, John; Coe, Sharon; Govindan, Ramesh

    2014-08-28

    This article discusses the experiences from the development and deployment of two image-based environmental monitoring sensor applications using an embedded wireless sensor network. Our system uses low-power image sensors and the Tenet general purpose sensing system for tiered embedded wireless sensor networks. It leverages Tenet's built-in support for reliable delivery of high rate sensing data, scalability and its flexible scripting language, which enables mote-side image compression and the ease of deployment. Our first deployment of a pitfall trap monitoring application at the James San Cannot Mountain Reserve provided us with insights and lessons learned into the deployment of and compression schemes for these embedded wireless imaging systems. Our three month-long deployment of a bird nest monitoring application resulted in over 100,000 images collected from a 19-camera node network deployed over an area of 0.05 square miles, despite highly variable environmental conditions. Our biologists found the on-line, near-real-time access to images to be useful for obtaining data on answering their biological questions.

  2. Understanding the Potential of WO₃ Based Sensors for Breath Analysis.

    PubMed

    Staerz, Anna; Weimar, Udo; Barsan, Nicolae

    2016-10-29

    Tungsten trioxide is the second most commonly used semiconducting metal oxide in gas sensors. Semiconducting metal oxide (SMOX)-based sensors are small, robust, inexpensive and sensitive, making them highly attractive for handheld portable medical diagnostic detectors. WO₃ is reported to show high sensor responses to several biomarkers found in breath, e.g., acetone, ammonia, carbon monoxide, hydrogen sulfide, toluene, and nitric oxide. Modern material science allows WO₃ samples to be tailored to address certain sensing needs. Utilizing recent advances in breath sampling it will be possible in the future to test WO₃-based sensors in application conditions and to compare the sensing results to those obtained using more expensive analytical methods.

  3. A general framework for sensor-based human activity recognition.

    PubMed

    Köping, Lukas; Shirahama, Kimiaki; Grzegorzek, Marcin

    2018-04-01

    Today's wearable devices like smartphones, smartwatches and intelligent glasses collect a large amount of data from their built-in sensors like accelerometers and gyroscopes. These data can be used to identify a person's current activity and in turn can be utilised for applications in the field of personal fitness assistants or elderly care. However, developing such systems is subject to certain restrictions: (i) since more and more new sensors will be available in the future, activity recognition systems should be able to integrate these new sensors with a small amount of manual effort and (ii) such systems should avoid high acquisition costs for computational power. We propose a general framework that achieves an effective data integration based on the following two characteristics: Firstly, a smartphone is used to gather and temporally store data from different sensors and transfer these data to a central server. Thus, various sensors can be integrated into the system as long as they have programming interfaces to communicate with the smartphone. The second characteristic is a codebook-based feature learning approach that can encode data from each sensor into an effective feature vector only by tuning a few intuitive parameters. In the experiments, the framework is realised as a real-time activity recognition system that integrates eight sensors from a smartphone, smartwatch and smartglasses, and its effectiveness is validated from different perspectives such as accuracies, sensor combinations and sampling rates. Copyright © 2018 Elsevier Ltd. All rights reserved.

  4. Pristine carbon nanotubes based resistive temperature sensor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Alam, Md Bayazeed, E-mail: bayazeed786@gmail.com; Jamia Millia Islamia; Saini, Sudhir Kumar, E-mail: sudhirsaini1310@gmail.com

    A good sensor must be highly sensitive, faster in response, of low cost cum easily producible, and highly reliable. Incorporation of nano-dimensional particles/ wires makes conventional sensors more effective in terms of fulfilling the above requirements. For example, Carbon Nanotubes (CNTs) are promising sensing element because of its large aspect ratio, unique electronic and thermal properties. In addition to their use for widely reported chemical sensing, it has also been explored for temperature sensing. This paper presents the fabrication of CNTs based temperature sensor, prepared on silicon substrate using low cost spray coating method, which is reliable and reproducible methodmore » to prepare uniform CNTs thin films on any substrate. Besides this, simple and inexpensive method of preparation of dispersion of single walled CNTs (SWNTs) in 1,2 dichlorobenzene by using probe type ultrasonicator for debundling the CNTs for improving sensor response were used. The electrical contacts over the dispersed SWNTs were taken using silver paste electrodes. Fabricated sensors clearly show immediate change in resistance as a response to change in temperature of SWNTs. The measured sensitivity (change in resistance with temperature) of the sensor was found ∼ 0.29%/°C in the 25°C to 60°C temperature range.« less

  5. A comprehensive review of lossy mode resonance-based fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Zhao, Wan-Ming

    2018-01-01

    This review paper presents the achievements and present developments in lossy mode resonances-based optical fiber sensors in different sensing field, such as physical, chemical and biological, and briefly look forward to its future development trend in the eyes of the author. Lossy mode resonances (LMR) is a relatively new physical optics phenomenon put forward in recent years. Fiber sensors utilizing LMR offered a new way to improve the sensing capability. LMR fiber sensors have diverse structures such as D-shaped, cladding-off, fiber tip, U-shaped and tapered fiber structures. Major applications of LMR sensors include refraction sensors and biosensors. LMR-based fiber sensors have attracted considerable research and development interest, because of their distinct advantages such as high sensitivity and label-free measurement. This kind of sensor is also of academic interest and many novel and great ideas are continuously developed.

  6. A Simulation Environment for Benchmarking Sensor Fusion-Based Pose Estimators.

    PubMed

    Ligorio, Gabriele; Sabatini, Angelo Maria

    2015-12-19

    In-depth analysis and performance evaluation of sensor fusion-based estimators may be critical when performed using real-world sensor data. For this reason, simulation is widely recognized as one of the most powerful tools for algorithm benchmarking. In this paper, we present a simulation framework suitable for assessing the performance of sensor fusion-based pose estimators. The systems used for implementing the framework were magnetic/inertial measurement units (MIMUs) and a camera, although the addition of further sensing modalities is straightforward. Typical nuisance factors were also included for each sensor. The proposed simulation environment was validated using real-life sensor data employed for motion tracking. The higher mismatch between real and simulated sensors was about 5% of the measured quantity (for the camera simulation), whereas a lower correlation was found for an axis of the gyroscope (0.90). In addition, a real benchmarking example of an extended Kalman filter for pose estimation from MIMU and camera data is presented.

  7. Water-Table and Potentiometric-Surface Altitudes in the Upper Glacial, Magothy, and Lloyd Aquifers beneath Long Island, New York, March-April 2006

    USGS Publications Warehouse

    Monti, Jack; Busciolano, Ronald J.

    2009-01-01

    The U.S. Geological Survey (USGS), in cooperation with State and local agencies, systematically collects ground-water data at varying measurement frequencies to monitor the hydrologic situation on Long Island, New York. Each year during March and April, the USGS conducts a synoptic survey of hydrologic conditions to define the spatial distribution of the water table and potentiometric surfaces within the three main water-bearing units underlying Long Island - the upper glacial, Magothy, and Lloyd aquifers. These data and the maps constructed from them are commonly used in studies of Long Island's hydrology, and by water managers and suppliers for aquifer management and planning purposes. Water-level measurements made in 502 wells across Long Island during March-April 2006, were used to prepare the maps in this report. Measurements were made by the wetted-tape method to the nearest hundredth of a foot. Water-table and potentiometric-surface altitudes in these aquifers were contoured using these measurements. The water-table contours were interpreted using water-level data collected from 341 wells screened in the upper glacial aquifer and (or) shallow Magothy aquifer; the Magothy aquifer's potentiometric-surface contours were interpreted from measurements at 102 wells screened in the middle to deep Magothy aquifer and (or) contiguous and hydraulically connected Jameco aquifer; and the Lloyd aquifer's potentiometric-surface contours were interpreted from measurements at 59 wells screened in the Lloyd aquifer or contiguous and hydraulically connected North Shore aquifer. Many of the supply wells are in continuous operation and, therefore, were turned off for a minimum of 24 hours before measurements were made so that the water levels in the wells could recover to the level of the potentiometric head in the surrounding aquifer. Full recovery time at some of these supply wells can exceed 24 hours; therefore, water levels measured at these wells are assumed to be less

  8. Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites

    NASA Astrophysics Data System (ADS)

    Gao, Yang; Fang, Xiaoliang; Tan, Jianping; Lu, Ting; Pan, Likun; Xuan, Fuzhen

    2018-06-01

    Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human–machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF < 1). The enhanced sensitivity of the strain sensors is ascribed to the sliding of individual fragmentized-CNT/PDMS-composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

  9. Highly sensitive strain sensors based on fragmentized carbon nanotube/polydimethylsiloxane composites.

    PubMed

    Gao, Yang; Fang, Xiaoliang; Tan, Jianping; Lu, Ting; Pan, Likun; Xuan, Fuzhen

    2018-06-08

    Wearable strain sensors based on nanomaterial/elastomer composites have potential applications in flexible electronic skin, human motion detection, human-machine interfaces, etc. In this research, a type of high performance strain sensors has been developed using fragmentized carbon nanotube/polydimethylsiloxane (CNT/PDMS) composites. The CNT/PDMS composites were ground into fragments, and a liquid-induced densification method was used to fabricate the strain sensors. The strain sensors showed high sensitivity with gauge factors (GFs) larger than 200 and a broad strain detection range up to 80%, much higher than those strain sensors based on unfragmentized CNT/PDMS composites (GF < 1). The enhanced sensitivity of the strain sensors is ascribed to the sliding of individual fragmentized-CNT/PDMS-composite particles during mechanical deformation, which causes significant resistance change in the strain sensors. The strain sensors can differentiate mechanical stimuli and monitor various human body motions, such as bending of the fingers, human breathing, and blood pulsing.

  10. Cooperative UAV-Based Communications Backbone for Sensor Networks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roberts, R S

    2001-10-07

    The objective of this project is to investigate the use of unmanned air vehicles (UAVs) as mobile, adaptive communications backbones for ground-based sensor networks. In this type of network, the UAVs provide communication connectivity to sensors that cannot communicate with each other because of terrain, distance, or other geographical constraints. In these situations, UAVs provide a vertical communication path for the sensors, thereby mitigating geographic obstacles often imposed on networks. With the proper use of UAVs, connectivity to a widely disbursed sensor network in rugged terrain is readily achieved. Our investigation has focused on networks where multiple cooperating UAVs aremore » used to form a network backbone. The advantage of using multiple UAVs to form the network backbone is parallelization of sensor connectivity. Many widely spaced or isolated sensors can be connected to the network at once using this approach. In these networks, the UAVs logically partition the sensor network into sub-networks (subnets), with one UAV assigned per subnet. Partitioning the network into subnets allows the UAVs to service sensors in parallel thereby decreasing the sensor-to-network connectivity. A UAV services sensors in its subnet by flying a route (path) through the subnet, uplinking data collected by the sensors, and forwarding the data to a ground station. An additional advantage of using multiple UAVs in the network is that they provide redundancy in the communications backbone, so that the failure of a single UAV does not necessarily imply the loss of the network.« less

  11. Temperature characteristics research of SOI pressure sensor based on asymmetric base region transistor

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaofeng; Li, Dandan; Yu, Yang; Wen, Dianzhong

    2017-07-01

    Based on the asymmetric base region transistor, a pressure sensor with temperature compensation circuit is proposed in this paper. The pressure sensitive structure of the proposed sensor is constructed by a C-type silicon cup and a Wheatstone bridge with four piezoresistors ({R}1, {R}2, {R}3 and {R}4) locating on the edge of a square silicon membrane. The chip was designed and fabricated on a silicon on insulator (SOI) wafer by micro electromechanical system (MEMS) technology and bipolar transistor process. When the supply voltage is 5.0 V, the corresponding temperature coefficient of the sensitivity (TCS) for the sensor before and after temperature compensation are -1862 and -1067 ppm/°C, respectively. Through varying the ratio of the base region resistances {r}1 and {r}2, the TCS for the sensor with the compensation circuit is -127 ppm/°C. It is possible to use this compensation circuit to improve the temperature characteristics of the pressure sensor. Project supported by the National Natural Science Foundation of China (No. 61471159), the Natural Science Foundation of Heilongjiang Province (No. F201433), the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province (No. 2015018), and the Special Funds for Science and Technology Innovation Talents of Harbin in China (No. 2016RAXXJ016).

  12. Cell-Based Odorant Sensor Array for Odor Discrimination Based on Insect Odorant Receptors.

    PubMed

    Termtanasombat, Maneerat; Mitsuno, Hidefumi; Misawa, Nobuo; Yamahira, Shinya; Sakurai, Takeshi; Yamaguchi, Satoshi; Nagamune, Teruyuki; Kanzaki, Ryohei

    2016-07-01

    The olfactory system of living organisms can accurately discriminate numerous odors by recognizing the pattern of activation of several odorant receptors (ORs). Thus, development of an odorant sensor array based on multiple ORs presents the possibility of mimicking biological odor discrimination mechanisms. Recently, we developed novel odorant sensor elements with high sensitivity and selectivity based on insect OR-expressing Sf21 cells that respond to target odorants by displaying increased fluorescence intensity. Here we introduce the development of an odorant sensor array composed of several Sf21 cell lines expressing different ORs. In this study, an array pattern of four cell lines expressing Or13a, Or56a, BmOR1, and BmOR3 was successfully created using a patterned polydimethylsiloxane film template and cell-immobilizing reagents, termed biocompatible anchor for membrane (BAM). We demonstrated that BAM could create a clear pattern of Sf21 sensor cells without impacting their odorant-sensing performance. Our sensor array showed odorant-specific response patterns toward both odorant mixtures and single odorant stimuli, allowing us to visualize the presence of 1-octen-3-ol, geosmin, bombykol, and bombykal as an increased fluorescence intensity in the region of Or13a, Or56a, BmOR1, and BmOR3 cell lines, respectively. Therefore, we successfully developed a new methodology for creating a cell-based odorant sensor array that enables us to discriminate multiple target odorants. Our method might be expanded into the development of an odorant sensor capable of detecting a large range of environmental odorants that might become a promising tool used in various applications including the study of insect semiochemicals and food contamination.

  13. Comparison of HPLC, UV spectrophotometry and potentiometric titration methods for the determination of lumefantrine in pharmaceutical products.

    PubMed

    da Costa César, Isabela; Nogueira, Fernando Henrique Andrade; Pianetti, Gérson Antônio

    2008-09-10

    This paper describes the development and evaluation of a HPLC, UV spectrophotometry and potentiometric titration methods to quantify lumefantrine in raw materials and tablets. HPLC analyses were carried out using a Symmetry C(18) column and a mobile phase composed of methanol and 0.05% trifluoroacetic acid (80:20), with a flow rate of 1.0ml/min and UV detection at 335nm. For the spectrophotometric analyses, methanol was used as solvent and the wavelength of 335nm was selected for the detection. Non-aqueous titration of lumefantrine was carried out using perchloric acid as titrant and glacial acetic acid/acetic anhydride as solvent. The end point was potentiometrically determined. The three evaluated methods showed to be adequate to quantify lumefantrine in raw materials, while HPLC and UV methods presented the most reliable results for the analyses of tablets.

  14. Monitoring Method and Apparatus Using Asynchronous, One-Way Transmission from Sensor to Base Station

    NASA Technical Reports Server (NTRS)

    Drouant, George J. (Inventor); Jensen, Scott L. (Inventor)

    2013-01-01

    A monitoring system is disclosed, which includes a base station and at least one sensor unit that is separate from the base station. The at least one sensor unit resides in a dormant state until it is awakened by the triggering of a vibration-sensitive switch. Once awakened, the sensor may take a measurement, and then transmit to the base station the measurement. Once data is transmitted from the sensor to the base station, the sensor may return to its dormant state. There may be various sensors for each base station and the various sensors may optionally measure different quantities, such as current, voltage, single-axis and/or three-axis magnetic fields.

  15. The difference between the potentiometric surfaces of the Magothy Aquifer of September 1975 and September 1995 in southern Maryland

    USGS Publications Warehouse

    Curtin, Stephen E.; Andreasen, David C.; Mack, Frederick K.

    1996-01-01

    A map showing the net change in the poentiometric surface of the Magothy aquifer in the Magothy Formation of Cretaceous age in southern Maryland from September 1975 to September 1995 was based on water-level measurements in 67 wells. The map shows that the decline of the potentiometric surface during the 20-year period ranged from 2 to 21 feet in the northernmost part of the study area. The decline was greater than 40 feet in parts of southern Prince Georges County, 75 feet at Waldorf, and 28 feet at the Chalk Point powerplant.

  16. Aptamer based electrochemical sensors for emerging environmental pollutants

    PubMed Central

    Hayat, Akhtar; Marty, Jean L.

    2014-01-01

    Environmental contaminants monitoring is one of the key issues in understanding and managing hazards to human health and ecosystems. In this context, aptamer based electrochemical sensors have achieved intense significance because of their capability to resolve a potentially large number of problems and challenges in environmental contamination. An aptasensor is a compact analytical device incorporating an aptamer (oligonulceotide) as the sensing element either integrated within or intimately associated with a physiochemical transducer surface. Nucleic acid is well known for the function of carrying and passing genetic information, however, it has found a key role in analytical monitoring during recent years. Aptamer based sensors represent a novelty in environmental analytical science and there are great expectations for their promising performance as alternative to conventional analytical tools. This review paper focuses on the recent advances in the development of aptamer based electrochemical sensors for environmental applications with special emphasis on emerging pollutants. PMID:25019067

  17. Temperature and pH sensors based on graphenic materials.

    PubMed

    Salvo, P; Calisi, N; Melai, B; Cortigiani, B; Mannini, M; Caneschi, A; Lorenzetti, G; Paoletti, C; Lomonaco, T; Paolicchi, A; Scataglini, I; Dini, V; Romanelli, M; Fuoco, R; Di Francesco, F

    2017-05-15

    Point-of-care applications and patients' real-time monitoring outside a clinical setting would require disposable and durable sensors to provide better therapies and quality of life for patients. This paper describes the fabrication and performances of a temperature and a pH sensor on a biocompatible and wearable board for healthcare applications. The temperature sensor was based on a reduced graphene oxide (rGO) layer that changed its electrical resistivity with the temperature. When tested in a human serum sample between 25 and 43°C, the sensor had a sensitivity of 110±10Ω/°C and an error of 0.4±0.1°C compared with the reference value set in a thermostatic bath. The pH sensor, based on a graphene oxide (GO) sensitive layer, had a sensitivity of 40±4mV/pH in the pH range between 4 and 10. Five sensor prototypes were tested in a human serum sample over one week and the maximum deviation of the average response from reference values obtained by a glass electrode was 0.2pH units. For biological applications, the temperature and pH sensors were successfully tested for in vitro cytotoxicity with human fibroblast cells (MRC-5) over 24h. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Space-based infrared scanning sensor LOS determination and calibration using star observation

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Xu, Zhan; An, Wei; Deng, Xin-Pu; Yang, Jun-Gang

    2015-10-01

    This paper provides a novel methodology for removing sensor bias from a space based infrared (IR) system (SBIRS) through the use of stars detected in the background field of the sensor. Space based IR system uses the LOS (line of sight) of target for target location. LOS determination and calibration is the key precondition of accurate location and tracking of targets in Space based IR system and the LOS calibration of scanning sensor is one of the difficulties. The subsequent changes of sensor bias are not been taking into account in the conventional LOS determination and calibration process. Based on the analysis of the imaging process of scanning sensor, a theoretical model based on the estimation of bias angles using star observation is proposed. By establishing the process model of the bias angles and the observation model of stars, using an extended Kalman filter (EKF) to estimate the bias angles, and then calibrating the sensor LOS. Time domain simulations results indicate that the proposed method has a high precision and smooth performance for sensor LOS determination and calibration. The timeliness and precision of target tracking process in the space based infrared (IR) tracking system could be met with the proposed algorithm.

  19. Highly selective gas sensor arrays based on thermally reduced graphene oxide.

    PubMed

    Lipatov, Alexey; Varezhnikov, Alexey; Wilson, Peter; Sysoev, Victor; Kolmakov, Andrei; Sinitskii, Alexander

    2013-06-21

    The electrical properties of reduced graphene oxide (rGO) have been previously shown to be very sensitive to surface adsorbates, thus making rGO a very promising platform for highly sensitive gas sensors. However, poor selectivity of rGO-based gas sensors remains a major problem for their practical use. In this paper, we address the selectivity problem by employing an array of rGO-based integrated sensors instead of focusing on the performance of a single sensing element. Each rGO-based device in such an array has a unique sensor response due to the irregular structure of rGO films at different levels of organization, ranging from nanoscale to macroscale. The resulting rGO-based gas sensing system could reliably recognize analytes of nearly the same chemical nature. In our experiments rGO-based sensor arrays demonstrated a high selectivity that was sufficient to discriminate between different alcohols, such as methanol, ethanol and isopropanol, at a 100% success rate. We also discuss a possible sensing mechanism that provides the basis for analyte differentiation.

  20. Optical Graphene Gas Sensors Based on Microfibers: A Review

    PubMed Central

    Wu, Yu; Yao, Baicheng; Yu, Caibin; Rao, Yunjiang

    2018-01-01

    Graphene has become a bridge across optoelectronics, mechanics, and bio-chemical sensing due to its unique photoelectric characteristics. Moreover, benefiting from its two-dimensional nature, this atomically thick film with full flexibility has been widely incorporated with optical waveguides such as fibers, realizing novel photonic devices including polarizers, lasers, and sensors. Among the graphene-based optical devices, sensor is one of the most important branch, especially for gas sensing, as rapid progress has been made in both sensing structures and devices in recent years. This article presents a comprehensive and systematic overview of graphene-based microfiber gas sensors regarding many aspects including sensing principles, properties, fabrication, interrogating and implementations. PMID:29565314