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Sample records for potentiometric anion selectivity

  1. Zn(II) complex-based potentiometric sensors for selective determination of nitrate anion.

    PubMed

    Mahajan, Rakesh Kumar; Kaur, Ravneet; Miyake, Hiroyuki; Tsukube, Hiroshi

    2007-02-12

    Polymeric membranes containing new Zn(II) complexes as anion carriers were prepared for determination of nitrate anion present in water samples. Two Zn(II) complexes coordinated by neutral tetradentate ligands, N,N'-ethylene-bis(N-methyl-(S)-alanine methylamide) and N,N'-ethylene-bis(N-methyl-(S)-alanine dimethylamide), worked well as anion-selective carriers, while common phthalocyanine Zn(II) complex rarely responded to any anions. The combination of these new Zn(II) complexes with dioctylsebacate as a plasticizer particularly offered high sensing selectivity for nitrate anion. They exhibited near-Nernstian slopes in the wide linear concentration range of 5.0 x 10(-5) to 1.0 x 10(-1) M, and operated well in the wide pH range from 4 to 11 with the response time of less than 25s. The potentiometric selectivity coefficients were evaluated using the fixed interference method, indicating that the two Zn(II) complexes exhibited better selectivity for nitrate anion with respect to a wide variety of inorganic anions. Although chloride anion worked as an interfering species at a concentration higher than 1.0 x 10(-3) M, the new Zn(II) complex-based sensors were applicable in determination of the nitrate anion after adding silver sulfate to remove the chloride anion.

  2. Dysprosium selective potentiometric membrane sensor.

    PubMed

    Zamani, Hassan Ali; Faridbod, Farnoush; Ganjali, Mohammad Reza

    2013-03-01

    A novel Dy(III) ion-selective PVC membrane sensor was made using a new synthesized organic compound, 3,4-diamino-N'-((pyridin-2-yl)methylene)benzohydrazide (L) as an excellent sensing element. The electrode showed a Nernstian slope of 19.8 ± 0.6 mV per decade in a wide concentration range of 1.0 × 10(-6)-1.0 × 10(-2) mol L(-1), a detection limit of 5.5 × 10(-7) mol L(-1), a short conditioning time, a fast response time (<10s), and high selectivity towards Dy(III) ion in contrast to other cations. The proposed sensor was successfully used as an indicator electrode in the potentiometric titration of Dy(III) ions with EDTA. The membrane sensor was also applied to the F(-) ion indirect determination of some mouth washing solutions and to the Dy(3+) determination in binary mixtures.

  3. Potentiometric Electronic Tongue to Resolve Mixtures of Sulfide and Perchlorate Anions

    PubMed Central

    Wilson, Deivy; Abbas, Mohammed N.; Radwan, Abdel Latief A.; del Valle, Manel

    2011-01-01

    This work describes the use of an array of potentiometric sensors and an artificial neural network response model to determine perchlorate and sulfide ions in polluted waters, by what is known as an electronic tongue. Sensors used have been all-solid-state PVC membrane selective electrodes, where their ionophores were different metal-phtalocyanine complexes with specific and anion generic responses. The study case illustrates the potential use of electronic tongues in the quantification of mixtures when interfering effects need to be counterbalanced: relative errors in determination of individual ions can be decreased typically from 25% to less than 5%, if compared to the use of a single proposed ion-selective electrode. PMID:22163795

  4. Potentiometric electronic tongue to resolve mixtures of sulfide and perchlorate anions.

    PubMed

    Wilson, Deivy; Abbas, Mohammed N; Radwan, Abdel Latief A; del Valle, Manel

    2011-01-01

    This work describes the use of an array of potentiometric sensors and an artificial neural network response model to determine perchlorate and sulfide ions in polluted waters, by what is known as an electronic tongue. Sensors used have been all-solid-state PVC membrane selective electrodes, where their ionophores were different metal-phtalocyanine complexes with specific and anion generic responses. The study case illustrates the potential use of electronic tongues in the quantification of mixtures when interfering effects need to be counterbalanced: relative errors in determination of individual ions can be decreased typically from 25% to less than 5%, if compared to the use of a single proposed ion-selective electrode.

  5. Data acquisition system for ion-selective potentiometric sensors

    NASA Astrophysics Data System (ADS)

    Filipkowski, Andrzej; Ogrodzki, Jan; Opalski, Leszek J.; Rybaniec, Radoslaw; Wieczorek, Piotr Z.

    2009-06-01

    The paper presents an idea and directives on construction of a measurement system for estimation of ions' concentration in water. System presented in paper has been fully designed and manufactured in Warsaw University of Technology in Institute of Electronic Systems. The measurement system works with cheap ion-selective potentiometric sensors. System allows for potentiometric, transient response and voltamperometric measurements. Data fusion method has been implemented in the system to increase the estimation's accuracy. Presented solution contains of many modern electronic elements like 32bit ARM microcontroller, precise operational amplifiers and some hydraulics subsystems essential for chemical measurements.

  6. 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. PMID:10703998

  7. 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-Jr, 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. PMID:25175244

  8. 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-Jr, 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.

  9. Potentiometric sensors based on fluorous membranes doped with highly selective ionophores for carbonate.

    PubMed

    Chen, Li D; Mandal, Debaprasad; Pozzi, Gianluca; Gladysz, John A; Bühlmann, Philippe

    2011-12-28

    Manganese(III) complexes of three fluorophilic salen derivatives were used to prepare ion-selective electrodes (ISEs) with ionophore-doped fluorous sensing membranes. Because of their extremely low polarity and polarizability, fluorous media are not only chemically very inert but also solvate potentially interfering ions poorly, resulting in a much improved discrimination of such ions. Indeed, the new ISEs exhibited selectivities for CO(3)(2-) that exceed those of previously reported ISEs based on nonfluorous membranes by several orders of magnitude. In particular, the interference from chloride and salicylate was reduced by 2 and 6 orders of magnitude, respectively. To achieve this, the selectivities of these ISEs were fine-tuned by addition of noncoordinating hydrophobic ions (i.e., ionic sites) into the sensing membranes. Stability constants of the anion-ionophore complexes were determined from the dependence of the potentiometric selectivities on the charge sign of the ionic sites and the molar ratio of ionic sites and the ionophore. For this purpose, a previously introduced fluorophilic tetraphenylborate and a novel fluorophilic cation with a bis(triphenylphosphoranylidene)ammonium group, (R(f6)(CH(2))(3))(3)PN(+)P(R(f6)(CH(2))(3))(3), were utilized (where R(f6) is C(6)F(13)). The optimum CO(3)(2-) selectivities were found for sensing membranes composed of anionic sites and ionophore in a 1:4 molar ratio, which results in the formation of 2:1 complexes with CO(3)(2-) with stability constants up to 4.1 × 10(15). As predicted by established theory, the site-to-ionophore ratios that provide optimum potentiometric selectivity depend on the stoichiometries of the complexes of both the primary and the interfering ions. However, the ionophores used in this study give examples of charges and stoichiometries previously neither explicitly predicted by theory nor shown by experiment. The exceptional selectivity of fluorous membranes doped with these carbonate ionophores

  10. Simultaneous Analysis of Monovalent Anions and Cations with a Sub-Microliter Dead-Volume Flow-Through Potentiometric Detector for Ion Chromatography.

    PubMed

    Dumanli, Rukiye; Attar, Azade; Erci, Vildan; Isildak, Ibrahim

    2016-04-01

    A microliter dead-volume flow-through cell as a potentiometric detector is described in this article for sensitive, selective and simultaneous detection of common monovalent anions and cations in single column ion chromatography for the first time. The detection cell consisted of less selective anion- and cation-selective composite membrane electrodes together with a solid-state composite matrix reference electrode. The simultaneous separation and sensitive detection of sodium (Na(+)), potassium (K(+)), ammonium (NH4 (+)), chloride (Cl(-)) and nitrate (NO3 (-)) in a single run was achieved by using 98% 1.5 mM MgSO4 and 2% acetonitrile eluent with a mixed-bed ion-exchange separation column without suppressor column system. The separation and simultaneous detection of the anions and cations were completed in 6 min at the eluent flow-rate of 0.8 mL/min. Detection limits, at S/N = 3, were ranged from 0.2 to 1.0 µM for the anions and 0.3 to 3.0 µM for the cations, respectively. The developed method was successfully applied to the simultaneous determination of monovalent anions and cations in several environmental and biological samples.

  11. Simultaneous Analysis of Monovalent Anions and Cations with a Sub-Microliter Dead-Volume Flow-Through Potentiometric Detector for Ion Chromatography.

    PubMed

    Dumanli, Rukiye; Attar, Azade; Erci, Vildan; Isildak, Ibrahim

    2016-04-01

    A microliter dead-volume flow-through cell as a potentiometric detector is described in this article for sensitive, selective and simultaneous detection of common monovalent anions and cations in single column ion chromatography for the first time. The detection cell consisted of less selective anion- and cation-selective composite membrane electrodes together with a solid-state composite matrix reference electrode. The simultaneous separation and sensitive detection of sodium (Na(+)), potassium (K(+)), ammonium (NH4 (+)), chloride (Cl(-)) and nitrate (NO3 (-)) in a single run was achieved by using 98% 1.5 mM MgSO4 and 2% acetonitrile eluent with a mixed-bed ion-exchange separation column without suppressor column system. The separation and simultaneous detection of the anions and cations were completed in 6 min at the eluent flow-rate of 0.8 mL/min. Detection limits, at S/N = 3, were ranged from 0.2 to 1.0 µM for the anions and 0.3 to 3.0 µM for the cations, respectively. The developed method was successfully applied to the simultaneous determination of monovalent anions and cations in several environmental and biological samples. PMID:26786906

  12. Modified screen-printed ion selective electrodes for potentiometric determination of sodium dodecylsulfate in different samples.

    PubMed

    Ali, Tamer Awad; Mohamed, Gehad G

    2015-01-01

    Fabrication and general performance characteristics of novel screen-printed sensors for potentiometric determination of sodium dodecylsulfate (SDS) are described. The sensors are based on the use of ion-association complexes of SDS with cetylpyridinium chloride (electrode I) and cetyltrimethylammonium bromide (electrode II) as exchange sites in a screen-printed electrode matrix. Electrodes (I) and (II) show fast, stable, and near-Nernstian response for the mono-charge anion of SDS over the concentration range of 1×10(-2) - 5.8×10(-7) and 1×10(-2)-6.3×10(-7) mol/L at 25°C and the pH range of 2.0-9.0 and 2.0-8.0 with anionic slope of 57.32±0.81 and 56.58±0.65 mV/decade, respectively. Electrodes (I) and (II) have lower LODs of 5.8×10(-7) and 6.3×10(-7) mol/L and response times of about 8 and 13 s, respectively. Shelf life of 5 months for both electrodes is adequate. Selectivity coefficients of SDS related to a number of interfering cations, and some inorganic compounds were investigated. There were negligible interferences caused by most of the investigated species. The direct determination of 0.10-13.50 mg of SDS by electrodes (I) and (II) shows average recoveries of 99.96 and 99.85%, and mean RSDs of 0.83 and 1.04%, respectively. In the present investigation, both electrodes were used successfully as end point indicators for determination of SDS in pure pharmaceutical preparations and real spiked water samples. The results obtained using the proposed sensors to determine SDS in solution compared favorably with those obtained by the standard addition method.

  13. Selective detection and enumeration of fecal coliforms in water by potentiometric measurement of lipoic acid reduction.

    PubMed

    Jouenne, T; Junter, G A; Charriere, G

    1985-11-01

    Water samples of various origins were inoculated into a specific coliform-selective lactose broth provided with lipoic (thioctic) acid, and the time evolution of the redox potential of the cultures was monitored during incubation at 41 degrees C by use of gold versus reference electrodes. Positive potential-time responses, i.e., 100-mV potential shifts recorded within 20 h of inoculation, were related to the initial number of fecal coliforms in the broth determined by control enumeration techniques, and the organisms responsible were isolated and identified by conventional procedures. A total of 30 samples of wastewater, 38 of surface water, 553 of groundwater, and 110 of drinking water were tested successively. A total of 240 natural water samples, including 172 groundwater samples, and 1 drinking water sample were found to be positive in the potentiometric test. The majority (i.e., 92.5%) of the relevant potentiometric detection times were shorter than 15 h, and 96% of these could be attributed to Escherichia coli. Fifteen hours corresponded to the limit for detecting 1 E. coli cell per 100 ml of water. About 78% of the potentiometric responses occurring after 15 h were induced by fecal coliforms other than E. coli (Enterobacter cloacae, Klebsiella pneumoniae, and Citrobacter freundii). Calibration curves relating detection times shorter than 15 h to fecal coliform (i.e., E. coli) concentrations were constructed for the natural water samples tested. There were minor variations in the average growth rate of the organisms in the relation to the contamination level of the water tested. The number of false-positive samples in the potentiometric test was equivalent to that of false-negative samples (groundwater or drinking water).

  14. Tripodal Receptors for Cation and Anion Sensors

    PubMed Central

    Kuswandi, Bambang; Nuriman; Verboom, Willem; Reinhoudt, David N.

    2006-01-01

    This review discusses different types of artificial tripodal receptors for the selective recognition and sensing of cations and anions. Examples on the relationship between structure and selectivity towards cations and anions are described. Furthermore, their applications as potentiometric ion sensing are emphasised, along with their potential applications in optical sensors or optodes.

  15. Selectivity characteristics of potentiometric carbon dioxide sensors with various gas membrane materials

    SciTech Connect

    Kobos, R.K.; Parks, S.J.; Meyerhoff, M.E.

    1982-10-01

    The selectivity characteristics of potentiometric carbon dioxide sensors with regard to various organic and inorganic acid interferences have been systematically examined. When used in conjunction with a standard silicone rubber CO/sub 2/ permeable membrane, the sensor displays surprisingly large response to several organic acids having low volatility, e.g., benzoic, cinnamic, and salicylic acids. If the outer membrane is changed to a microporous Teflon material, the response to these substances is diminished, but poor selectivity over volatile organics and acidic gases results. The use of a new homogeneous Teflon-like membrane meterial is shown to offer dramatic improvement in selectivity for CO/sub 2/ over all of the compounds tested. The mechanistic reasons for this enhanced selectivity are discussed as are alternate methods for reducing organic acid interferences when using more conventional membrane materials. 4 figures, 1 table.

  16. Highly Sensitive and Fast Anion-Selective InN Quantum Dot Electrochemical Sensors

    NASA Astrophysics Data System (ADS)

    Hassan Alvi, Naveed ul; Rodriguez, Paul E. D. Soto; Gómez, Victor J.; Kumar, Praveen; Willander, Magnus; Nötzel, Richard

    2013-11-01

    Epitaxial InN quantum dots (QDs) are demonstrated as ion-selective electrode for potentiometric anion concentration measurements. The sensor reveals high sensitivity above 90 mV/decade for the detection of chlorine and hydroxyl ions in sodium chloride (NaCl), calcium chloride (CaCl2), and sodium hydroxide (NaOH) solutions. The response time is less than two seconds after which the signal is very stable and repeatable. The sensitivity for the InN QDs is about two times that for a reference InN thin film and the response time is about five times shorter. In pH buffer solutions the sensor reveals no clear response to cations. A model is presented for the high sensitivity, fast response, and ion selectivity based on the unique electronic properties of the InN surface together with the zero-dimensional nature of the QDs.

  17. An Ion-selective Electrode for Anion Perchlorate in Thick-film Technology

    PubMed Central

    Segui, María Jesús; Lizondo-Sabater, Josefa; Martínez-Máñez, Ramon; Sancenon, Félix; Soto, Juan; Garcia-Breijo, Eduardo; Gil, Luis

    2006-01-01

    The ionophore 1,4,7,10,13-penta(n-octyl)-1,4,7,10,13-pentaazacyclopentadecane (L1) was used for the development of miniaturised perchlorate-selective electrodes in thick-film technology. Different PVC membranes containing L1 and the plasticizers o-nitrophenyl octyl ether (NPOE), dibutyl phthalate (DBP), bis(2-ethylhexyl)sebacate (DOS) and dibutyl sebacate (DBS) were prepared and placed on a graphite working electrode manufactured by using thick film serigraphic technology. The perchlorate selective electrode containing DBS as plasticizer showed a potentiometric Nernstian response of -57 mV per decade in a range of perchlorate concentration from 1 × 10-4 to 1 × 10-1 M with a detection limit of 5 × 10-5 M. The ion selective electrodes containing DBP and NPOE as plasticizers exhibit a working range from 6.3 × 10-5 to 1 × 10-1 M and 7.4 × 10-5 to 1 × 10-1 M for perchlorate, respectively, with a detection limit of ca. 2.2 × 10-5 M. For all three electrodes a response time of ca. 5 s was found. The prepared electrodes do not show appreciable decay of the slope for at least 25 days. Potentiometric selectivity coefficients (log KpotClO4-,X-) with respect to the primary anion perchlorate were evaluated using the fixed interference method. These coefficients are of the order of 10-1.7 or smaller, indicating the relatively poor interference of the different anions studied.

  18. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Bowman-James, Kristen

    2004-12-01

    This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and efficient removal of targeted anions. Key findings include: (1) the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. Areas probed during the last funding period include: the design, synthesis, and physical and structural characterization of receptors and investigation of anion and dual ion pair extraction using lipophilic amide receptors for anion binding. A new collaboration has been added to the project in addition to the one with Dr. Bruce Moyer at Oak Ridge National Laboratory, with Professor Jonathan Sessler at the University of Texas at Austin.

  19. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Bowman-James, K.; Wilson, G.; Moyer, B. A.

    2004-12-11

    This project involves the design and synthesis of receptors for oxoanions of environmental importance, including emphasis on high level and low activity waste. Target anions have included primarily oxoanions and a study of the basic concepts behind selective binding of target anions. A primary target has been sulfate because of its deleterious influence on the vitrification of tank wastes

  20. Interaction between biphenols and anions: selective receptor for dihydrogenphosphate.

    PubMed

    Ito, Kazuaki; Nishiki, Makoto; Ohba, Yoshihiro

    2005-10-01

    Biphenol was shown to bind dihydrogenphosphate (H2PO4-) selectively over various other anions (MeCO2-, Cl-, Br-, I-, NO3-, HSO4-). The highly selectivity of biphenol toward dihydrogenphosphate is explained in terms of the basicity and shape of the guest anion. PMID:16205002

  1. 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.

  2. Determination of phosphorous in titanium bearing minerals by potentiometric titration using Pb-ion selective electrode.

    PubMed

    Ramadoss, K; Murty, D S; Mahanta, P L; Gomathy, B; Rangaswamy, R

    2000-01-24

    A method for phosphorous determination in titanium bearing minerals by potentiometric titration using a Pb-ion selective electrode has been developed. Sample decomposition is achieved by means of K(2)CO(3) fusion in a platinum crucible at 800 degrees C for 30 min in a muffle furnace, and subsequent leaching with water of the fused melt. The aqueous leachate is neutralised with HClO(4) and subsequent boiling. The obtained solution is used for titration with Pb(ClO(4))(2), and the Pb-ion selective electrode detects the end point. The lowest concentration determinable is 0.02% P(2)O(5) in a solid sample. The method was applied on in-house titanium bearing mineral samples and on IGS-31 ilmenite sample (British Geological Survey, UK). Synthetic samples were prepared and analysed, and phosphorous recovery is in the range 98-106%. The recovery and accuracy of the present method have been validated by spiking experiments and by comparing with the spectrophotometric values, respectively. The precision of the proposed method in terms of relative standard deviation is 2.0%. PMID:18967837

  3. Selectivity enhancement of anion-responsive electrodes by pulsed chronopotentiometry.

    PubMed

    Gemene, Kebede L; Shvarev, Alexey; Bakker, Eric

    2007-01-30

    A large and robust selectivity improvement of ion-selective electrodes is presented for the measurement of abundant ions. An improvement in selectivity by more than two orders of magnitude has been attained for the hydrophilic chloride ions measured in a dilute background of the lipophilic ions perchlorate and salicylate in a pulsed chronopotentiometric measurement mode. This is attributed to a robust kinetic discrimination of the dilute lipophilic ions in this measuring mode, which is not possible to achieve in classical potentiometry. Maximum tolerable concentrations of the interfering ions are found to be on the order of 30 microM before causing substantial changes in potential. As an example of practical relevance, the robust detection of chloride in 72 microM salicylate (reflecting 1:10 diluted blood) with a detection limit of 0.5 mM chloride is demonstrated. Corresponding potentiometric sensors did not give a useful chloride response under these conditions.

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

    DOE PAGESBeta

    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

  5. Ion-selective electrodes in potentiometric titrations; a new method for processing and evaluating titration data.

    PubMed

    Granholm, Kim; Sokalski, Tomasz; Lewenstam, Andrzej; Ivaska, Ari

    2015-08-12

    A new method to convert the potential of an ion-selective electrode to concentration or activity in potentiometric titration is proposed. The advantage of this method is that the electrode standard potential and the slope of the calibration curve do not have to be known. Instead two activities on the titration curve have to be estimated e.g. the starting activity before the titration begins and the activity at the end of the titration in the presence of large excess of titrant. This new method is beneficial when the analyte is in a complexed matrix or in a harsh environment which affects the properties of the electrode and the traditional calibration procedure with standard solutions cannot be used. The new method was implemented both in a method of linearization based on the Grans's plot and in determination of the stability constant of a complex and the concentration of the complexing ligand in the sample. The new method gave accurate results when using titrations data from experiments with samples of known composition and with real industrial harsh black liquor sample. A complexometric titration model was also developed.

  6. Aluminum(III) selective potentiometric sensor based on morin in poly(vinyl chloride) matrix.

    PubMed

    Gupta, Vinod K; Jain, Ajay K; Maheshwari, Gaurav

    2007-06-15

    Al(3+) selective sensor has been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier morin as ionophore. Best performance was exhibited by the membrane having composition as morin:PVC:sodium tetraphenyl borate:tri-n-butylphosphate in the ratio 5:150:5:150 (w/w, mg). This membrane worked well over a wide activity range of 5.0x10(-7) to 1.0x10(-1)M of Al(3+) with a Nernstian slope of 19.7+/-0.1mV/decade of Al(3+) activity and a limit of detection 3.2x10(-7)M. The response time of the sensor is approximately 5s and membrane could be used over a period of 2 months with good reproducibility. The proposed sensor works well over a pH range (3.5-5.0) and demonstrates good discriminating power over a number of mono-, di- and trivalent cations. The sensor can also be used in partially non-aqueous media having up to 20% (v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working activity range. The sensor has also been used in the potentiometric titration of Al(3+) with EDTA and for its determination in zinc plating mud and red mud.

  7. Anion Separation by Selective Crystallization of Metal-Organic-Frameworks

    SciTech Connect

    Custelcean, Radu

    2006-01-01

    A novel approach for the separation of anions from aqueous mixtures was demonstrated, which involves their selective crystallization with metal-organic frameworks (MOFs) containing urea functional groups. Self-assembly of Zn{sup 2+} with the N,N{prime}-bis(m-pyridyl)urea (BPU) linker results in the formation of one-dimensional MOFs including various anions for charge balance, which interact to different extents with the zinc nodes and the urea hydrogen-bonding groups, depending on their coordinating abilities. Thus, Cl{sup -}, Br{sup -}, I{sup -}, and SO{sub 4}{sup 2-}, in the presence of BPU and Zn{sup 2+}, form MOFs from water, in which the anions coordinate the zinc and are hydrogen-bonded to the urea groups, whereas NO{sub 3}{sup -} and ClO{sub 4}{sup -} anions either do not form MOFs or form water-soluble discrete coordination complexes under the same conditions. X-ray diffraction, FTIR, and elemental analysis of the coordination polymers precipitated from aqueous mixtures containing equivalent amounts of these anions indicated total exclusion of the oxoanions and selective crystallization of the halides in the form of solid solutions with the general composition ZnCl{sub x}Br{sub y}I{sub z} {center_dot} BPU (x + y + z = 2), with an anti-Hofmeister selectivity. The concomitant inclusion of the halides in the same structural frameworks facilitates the rationalization of the observed selectivity on the basis of the diminishing interactions with the zinc and urea acidic centers in the MOFs when going from Cl{sup -} to I{sup -}, which correlates with decreasing anionic charge density in the same order. The overall crystal packing efficiency of the coordination frameworks, which ultimately determines their solubility, also plays an important role in the anion crystallization selectivity under thermodynamic equilibration.

  8. Flexibility of inorganic tennis ball structures inducing anion selectivity.

    PubMed

    Kim, Ki-Hyun; Park, Jung Su; Kang, Tae Yi; Oh, Kyungeun; Seo, Mi-Sook; Sohn, Youn Soo; Jun, Moo-Jin; Nam, Wonwoo; Kim, Kwan Mook

    2006-09-18

    Inorganic tennis balls (ITBs), [[{Pt(betmp)(dach)}(2)Cu](2)(X)][X](3) (in which X=ClO(4) (-) (3), NO(3) (-) (4), Cl(-) (5) and Br(-) (6); dach=trans-1,2-diaminocyclohexane and betmp=bisethylthiomethylidenepropanedioate) and [[{Pt(dteym)(dach)}(2)Cu](2)(PF(6))][PF(6)](3) (7; dteym=1,3-dithiepane-2-ylidenemalonate), were prepared as crystals. Investigation of their X-ray crystal structures revealed that shapes of the cavities in ITBs show significant distortions that depend on the properties of the encapsulated anions. The CuCu* distance was observed to be longest in 7 and shortest in 5, the difference between them being 2.05 A. The flexibility of cavity structures of ITBs makes it possible to encapsulate various anions inside the cavity, while their distortions may be a reason for the difference in the encapsulating ability for anions, that is, anion selectivity. Especially, the distortions observed in 7 are so severe that the encapsulating ability of the cavity for PF(6) (-) is very low compared to other anions. The shapes of ITBs with ClO(4) (-) and BF(4) (-) ions inside their cavities are very similar; however, ClO(4) (-) is encapsulated by the cavity better than BF(4) (-), which is explicable by the difference of metal-anion interactions. This structural study on ITBs gives a clue to the origin of the anion selectivity of the cavity in ITBs previously investigated by (19)F NMR spectroscopy of the ITBs in methanol.

  9. Flexibility of inorganic tennis ball structures inducing anion selectivity.

    PubMed

    Kim, Ki-Hyun; Park, Jung Su; Kang, Tae Yi; Oh, Kyungeun; Seo, Mi-Sook; Sohn, Youn Soo; Jun, Moo-Jin; Nam, Wonwoo; Kim, Kwan Mook

    2006-09-18

    Inorganic tennis balls (ITBs), [[{Pt(betmp)(dach)}(2)Cu](2)(X)][X](3) (in which X=ClO(4) (-) (3), NO(3) (-) (4), Cl(-) (5) and Br(-) (6); dach=trans-1,2-diaminocyclohexane and betmp=bisethylthiomethylidenepropanedioate) and [[{Pt(dteym)(dach)}(2)Cu](2)(PF(6))][PF(6)](3) (7; dteym=1,3-dithiepane-2-ylidenemalonate), were prepared as crystals. Investigation of their X-ray crystal structures revealed that shapes of the cavities in ITBs show significant distortions that depend on the properties of the encapsulated anions. The CuCu* distance was observed to be longest in 7 and shortest in 5, the difference between them being 2.05 A. The flexibility of cavity structures of ITBs makes it possible to encapsulate various anions inside the cavity, while their distortions may be a reason for the difference in the encapsulating ability for anions, that is, anion selectivity. Especially, the distortions observed in 7 are so severe that the encapsulating ability of the cavity for PF(6) (-) is very low compared to other anions. The shapes of ITBs with ClO(4) (-) and BF(4) (-) ions inside their cavities are very similar; however, ClO(4) (-) is encapsulated by the cavity better than BF(4) (-), which is explicable by the difference of metal-anion interactions. This structural study on ITBs gives a clue to the origin of the anion selectivity of the cavity in ITBs previously investigated by (19)F NMR spectroscopy of the ITBs in methanol. PMID:16800019

  10. Phenytoin speciation with potentiometric and chronopotentiometric ion-selective membrane electrodes.

    PubMed

    Jansod, Sutida; Afshar, Majid Ghahraman; Crespo, Gastón A; Bakker, Eric

    2016-05-15

    We report on an electrochemical protocol based on perm-selective membranes to provide valuable information about the speciation of ionizable drugs, with phenytoin as a model example. Membranes containing varying amounts of tetradodecylammonium chloride (TDDA) were read out at zero current (potentiometry) and with applied current techniques (chronopotentiometry). Potentiometry allows one to assess the ionized form of phenytoin (pKa~8.2) that corresponds to a negatively monocharged ion. A careful optimization of the membrane components resulted in a lower limit of detection (~1.6 µM) than previous reports. Once the pH (from 9 to 10) or the concentration of albumin is varied in the sample (from 0 to 30 g L(-1)), the potentiometric signal changes abruptly as a result of reducing/increasing the ionized concentration of phenytoin. Therefore, potentiometry as a single technique is by itself not sufficient to obtain information about the concentration and speciation of the drug in the system. For this reason, a tandem configuration with chronopotentiometry as additional readout principle was used to determine the total and ionized concentration of phenytoin. In samples containing excess albumin the rate-limiting step for the chronopotentiometry readout appears to be the diffusion of ionized phenytoin preceded by comparatively rapid deprotonation and decomplexation reactions. This protocol was applied to measure phenytoin in pharmaceutical tables (100mg per tablet). This tandem approach can likely be extended to more ionizable drugs and may eventually be utilized in view of pharmacological monitoring of drugs during the delivery process.

  11. Development of anion-selective membranes. [for energy storage

    NASA Technical Reports Server (NTRS)

    Lacey, R. E.; Cowsar, D. R.

    1975-01-01

    Methods were studied of preparing anion-exchange membranes that would have low resistance, high selectivity, and physical and chemical stability when used in acidic media in a redox energy storage system. Of the twelve systems selected for study, only the system that was based on crosslinked poly-4-vinylpyridinium chloride produced physically strong membranes when equilibrated in l M HCl. The resistivity of the best membrane was 12 ohm-cm, and the transference number for chloride ions was 0.81.

  12. The Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    SciTech Connect

    Sessler, Jonathan L.

    2005-06-01

    Work at carried out at ORNL since the inception of the project has served to demonstrate that the calix[4]pyrroles from the co-P.I.'s laboratory at the Univ. of Texas strongly enhance the extraction of sulfate by tricaprylmethylammonium nitrate or chloride in the presence of excess nitrate and chloride. Similar results were found in the case of the tetraamide macrocycles synthesized in the Bowman-James laboratory (Univ. of Kansas). Effort at the Univ. of Texas thus focused on generating new pyrrole-amide macrocycles that might combine the most favorable aspects of the calixpyrroles and the tetraamides. This culminated in the synthesis of several new receptors, which provided a ''matched set'' from whence insights into anion recognition could be inferred. As can be inferred from the data summarized in Table 1, small adjustments in the structure allow for a fine-tuning of the anion binding properties in favor of sulfate recognition, or in the case of injudicious modifications, selectivities that favor completely different classes of anionic substrates.

  13. Papaverine PVC membrane ion-selective electrodes based on its ion-exchangers with tetraphenylborate and tetrathiocyanate anions.

    PubMed

    Abbas, Mohammed Noor-Eldeen; Mostafa, Gamal Abdel-Hafiz

    2007-08-01

    The construction and general performance of novel potentiometric membrane ion selective electrodes for determination of papaverine hydrochloride has been described. They are based on the formation of the ion association complexes of papaverine (PA) with tetraphenylborate (TPB)(I) or tetrathiocyanate (TTC)(II) counter anions as electro-active material dispersed in a PVC matrix. The electrodes show fast, stable, near Nernstian response for 1 x 10(-2) to 6 x 10(-5) M and 1 x 10(-2) to 1 x 10(-5) M for PA-TPB and PA-TTC respectively at 25 degrees C over the pH range of 3-5.0 with a cationic slope of approximately 56.5 +/- 0.5 mV/decade for both sensors respectively. The lower detection limit is 4 x 10(-5) and 8 x 10(-6) M for PA- I and PA-II respectively with fast response time ranging from 20-45 sec. Selectivity coefficients for PA relative to a number of interfering substances were investigated. There is a negligible interference from the studied cations, anions, and pharmaceutical excipients. The determination of 4.0- 3000.0 microg/ml of PA in aqueous solutions shows an average recovery of 99.1% and a mean relative standard deviation of 1.4 at 100microg/ml. The direct determination of PA in some formulations (Vasorin injection) gave results that compare favorably with those obtained using the British Pharmacopoeia method. Potentiometric titration of PA with sodium tetraphenylborate and potassium thiocyanate as titrants utilizing the papaverine electrode as an end point indicator electrode has been carried out.

  14. Determination of selected anions in water by ion chromatography

    USGS Publications Warehouse

    Fishman, Marvin J.; Pyen, Grace

    1979-01-01

    Ion chromatography is a rapid, sensitive, precise, and accurate method for the determination of major anions in rainwater and surface waters. Simultaneous analyses of a single sample for bromide, chloride, fluoride, nitrate, nitrite, orthophosphate, and sulfate require approximately 20 minutes to obtain a chromatogram. Minimum detection limits range from 0.01 mg/L for fluoride to 0.20 mg/L for chloride and sulfate. Relative standard deviations were less than 9% for all anions except nitrite in Standard Reference Water Samples. Only one reference sample contained nitrite and its concentration was near the minimum level of detection. Similar precision was found for chloride, nitrate, and sulfate at concentrations less than 5 mg/L in rainfall samples. Precision for fluoride ranged from 12 to 22%, but is attributed to the low concentrations in these samples. The other anions were not detected. To determine accuracy of results, several samples were spiked with known concentrations of fluoride, chloride, nitrate, and sulfate; recoveries ranged from 96 to 103%. Known amounts of bromide and phosphate were added, separately, to several other waters, which contained bromide or phosphate. Recovery of added bromide and phosphate ranged from approximately 95 to 104%. No recovery data were obtained for nitrite. Chloride, nitrate, nitrite, orthophosphate, and sulfate, in several samples, were also determined independently by automated colorimetric procedures. An automated ion-selective electrode method was used to determine fluoride. Results are in agreement with results obtained by ion chromatography. (USGS).

  15. 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

    2011-04-01

    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.

  16. Potentiometric membrane sensor for the selective determination of pethidine in pharmaceutical preparations and biological fluids.

    PubMed

    Shalaby, Abdalla; El-Tohamy, Maha; El-Maamly, Magda; Aboul-Enein, Hassan Y

    2007-10-01

    The construction and general performance characteristics of a novel potentiometric PVC membrane sensor based on pethidine-phosphomolybdate as electroactive material for the determination of pethidine are described. This sensor exhibits fast, stable and near-Nernstain response 55.24 +/- 0.1, over the concentration range 1.10(-2)-1.10(-5)M for pethidine-phosphomolybdate over pH 2-7. No interferences are caused by many organic, inorganic cations, alkaloids and amino acids. The sensor proved useful for determining pethidine in pure forms, pharmaceutical injections and monitoring the content uniformity assay of ampoules. The designed sensor also show good accuracy for the determination of pethidine in biological fluids.

  17. VCA1008: An Anion-Selective Porin of Vibrio Cholerae.

    PubMed

    Goulart, Carolina L; Bisch, Paulo M; von Krüger, Wanda M A; Homblé, Fabrice

    2015-02-01

    A putative porin function has been assigned to VCA1008 of Vibrio cholerae. Its coding gene, vca1008, is expressed upon colonization of the small intestine in infant mice and human volunteers, and is essential for infection. In vitro, vca1008 is expressed under inorganic phosphate limitation and, in this condition, VCA1008 is the major outer membrane protein of the bacterium. Here, we provide the first functional characterization of VCA1008 reconstituted into planar lipid bilayers. Our main findings were: 1) VCA1008 forms an ion channel that, at high voltage (~±100 mV), presents a voltage-dependent activity and displays closures typical of trimeric porins, with a conductance of 4.28±0.04 nS (n=164) in 1M KCl; 2) It has a preferred selectivity for anions over cations; 3) Its conductance saturates with increasing inorganic phosphate concentration, suggesting VCA1008 contains binding site(s) for this anion; 4) Its ion selectivity is controlled by both fixed charged residues within the channel and diffusion along the pore; 5) Partitioning of poly (ethylene glycol)s (PEGs) of different molecular mass suggests that VCA1008 channel has a pore exclusion limit of 0.9 nm.

  18. Selective crystallization of urea-functionalized capsules with tunable anion-binding cavities

    SciTech Connect

    Custelcean, Radu; Remy, Priscilla

    2009-01-01

    Herein we report crystallization of self-assembled capsules functionalized with urea hydrogen-bonding groups as a means for selective separation of sulfate anion. The high complementarity and the rigid environment found in such crystalline systems impart strong discrimination between anions of different shape, like sulfate and sulfite, or anions of the same shape but slightly different size, like sulfate and selenate, with selectivity that exceeds that observed in sulfate-binding protein. Similar to natural receptors, these crystalline capsules completely isolate the anions from the aqueous solvent by encapsulating them inside rigid cavities lined with complementary hydrogen-bonding groups. Furthermore, the capsules are made from flexible building blocks, whose structure and relative orientation in the crystal can be allosterically regulated to fine-tune the anion selectivity. These characteristics suggest that crystallization of such urea-functionalized capsules from simple and flexible components represents a particularly promising approach for selective anion separation from highly competitive aqueous environments.

  19. Determination of arsenate in water by anion selective membrane electrode using polyurethane-silica gel fibrous anion exchanger composite.

    PubMed

    Khan, Asif Ali; Shaheen, Shakeeba

    2014-01-15

    Polyurethane (PU)-silica (Si gel) based fibrous anion exchanger composites were prepared by solid-gel polymerization of polyurethane in the presence of different amounts of silica gel. The formation of PU-Si gel fibrous anion exchanger composite was characterized by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTA), scanning electron microscopy (SEM) and elemental analysis. The membrane having a composition of 5:3 (PU:Si gel) shows best results for water content, porosity, thickness and swelling. Our studies show that the present ion selective membrane electrode is selective for arsenic, having detection limit (1×10(-8)M to 1×10(-1)M), response time (45s) and working pH range (5-8). The selectivity coefficient values for interfering ions indicate good selectivity for arsenate (AsO4(3-)) over interfering anions. The accuracy of the detection limit results was compared by PCA-Arsenomat. PMID:24275475

  20. Determination of arsenate in water by anion selective membrane electrode using polyurethane-silica gel fibrous anion exchanger composite.

    PubMed

    Khan, Asif Ali; Shaheen, Shakeeba

    2014-01-15

    Polyurethane (PU)-silica (Si gel) based fibrous anion exchanger composites were prepared by solid-gel polymerization of polyurethane in the presence of different amounts of silica gel. The formation of PU-Si gel fibrous anion exchanger composite was characterized by Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA-DTA), scanning electron microscopy (SEM) and elemental analysis. The membrane having a composition of 5:3 (PU:Si gel) shows best results for water content, porosity, thickness and swelling. Our studies show that the present ion selective membrane electrode is selective for arsenic, having detection limit (1×10(-8)M to 1×10(-1)M), response time (45s) and working pH range (5-8). The selectivity coefficient values for interfering ions indicate good selectivity for arsenate (AsO4(3-)) over interfering anions. The accuracy of the detection limit results was compared by PCA-Arsenomat.

  1. New potentiometric sensors based on selective recognition sites for determination of ephedrine in some pharmaceuticals and biological fluids.

    PubMed

    Hassan, Saad S M; Kamel, Ayman H; Abd El-Naby, Heba

    2013-01-15

    New cost-effective potentiometric membrane sensors with cylindrical configuration responsive to ephedrine are described. The sensors setup is, based on the use of triacetyl-β-cyclodextrin [(triacetyl-β-CD)] as a neutral ionophore embedded in a plasticized poly (vinyl chloride) (PVC) matrix (sensor I) and carboxylated poly(vinyl chloride) [(PVC-COOH)] as a simultaneous plastic matrix and ion exchanger (sensor II). Both sensors showed significant enhancement of response towards ephedrinium cation (EPD(+)) over a concentration range of 3.0 × 10(-5)-8.0 × 10(-3) mol L(-1) at pH 4-9 and 3-8 with low detection limits of 5.7 × 10(-6) and 6.2 × 10(-6) mol L(-1) for sensors (I) and (II), respectively. The sensors displayed near-Nernstian cationic slope of 57.0 and 55.6 mV decade(-1) for EPD(+) and the effects of lipophilic salts and various foreign common ions were examined. The sensors were also satisfactorily used as tubular detectors in a double channel flow injection system. The intrinsic characteristics of the detectors in a low dispersion manifold under hydrodynamic mode of operation were determined and compared with data obtained under batch mode of operation. Validation of the method revealed good performance characteristics including long life span, good selectivity for EPD(+) over a wide variety of other organic compounds, long term stability, high reproducibility, fast response, low detection limit, wide measurement range, acceptable accuracy and precision. Applications of the sensors to the determination of EPD(+) in pharmaceutical formulations and spiked biological fluid samples were carried out and compared with standard techniques. Notably, the sensors introduced offer several advantages over many of those previously described that are amenable to quality control/quality assurance assessment of the homogeneity, stability and purity of ephedrine drug tablets.

  2. Potentiometric Responses of Ion-Selective Electrodes Doped with Diureidocalix[4]arene towards Un-dissociated Benzoic Acid

    PubMed Central

    Krajewska, Agnieszka; Lhotak, Pavel; Radecka, Hanna

    2007-01-01

    Diureidocalix[4]arene have been applied as new ionophore in liquid membrane electrode (ISE) sensitive towards un-dissociated benzoic acid. The electrode demonstrated response towards benzoic acid with the detection limit 2.0 × 10-4 M which is sufficient for the determination of benzoic acid added to beverages as preservative in milimolar concentration. The selectivity coefficients measured by the matched potential method (MPM) showed its good selectivity against common anions present in drink samples. All measurements were made in presence of 1.0 × 10-2 M NaHSO4 pH 3.0 in order to reduce the influence of OH-. The applicability of diureidocalix[4]arene incorporated ISE has been checked by recovery test of benzoic acid in the presence of artificial drink matrix and by standard addition method.

  3. Highly selective electrode for potentiometric analysis of methadone in biological fluids and pharmaceutical formulations.

    PubMed

    Ardeshiri, Moslem; Jalali, Fahimeh

    2016-06-01

    In order to develop a fast and simple procedure for methadone analysis in biological fluids, a graphite paste electrode (GPE) was modified with the ion-pair of methadone-phosphotungstic acid, and multiwalled carbon nanotubes (MWCNTs). Optimized composition of the electrode with respect to graphite powder:paraffin oil:MWCNTs:ion pair, was 58:30:8:4 (w/w%). The electrode showed a near-Nernstian slope of 58.9 ± 0.3 mV/decade for methadone in a wide linear range of 1.0 × 10(-8)-4.6 × 10(-3)M, with a detection limit of 1.0 × 10(-8)M. The electrode response was independent of pH in the range of 5-11, with a fast response time (~4s) at 25 °C. The sensor showed high selectivity and was successfully applied to the determination of sub-micromolar concentrations of methadone in human blood serum and urine samples, with recoveries in the range of 95-99.8%. The average recovery of methadone from tablets (5 mg/tablet) by using the proposed method was 98%. The life time of the modified electrode was more than 5 months, due to the characteristic of GPE which can be cut off and fresh electrode surface be available. A titration procedure was performed for methadone analysis by using phosphotungstic acid, as titrating agent, which showed an accurate end point and 1:1 stoichiometry for the ion-pair formed (methadone:phosphotungstic acid). The simple and rapid procedure as well as excellent detection limit and selectivity are some of the advantages of the proposed sensor for methadone. PMID:27040192

  4. 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.

  5. Novel anthracene-based fluorescent sensor for selective recognition of acetate anions in protic media

    NASA Astrophysics Data System (ADS)

    Xu, Kuoxi; Kong, Huajie; Li, Qian; Song, Pan; Dai, Yanpeng; Yang, Li

    2015-02-01

    Novel 9-substituted anthracene derivatives were synthesized and characterized by IR, HRMS, 1H and 13C NMR. The fluorescence titration experiments were explored to study the interaction between the compounds and some anions, such as H2PO4-, P2O74-, F-, Cl-, Br-, I-, AcO- in H2O (0.01 M HEPES, pH = 7.4) under imitated physiological conditions. One of these compounds, bearing a phenylalaninol unit, showed specific fluorescence enhancement with acetate anion. The sensor L1 was found to present good selective fluorescence sensing ability to acetate anion through photoinduced electron-transfer mechanism in protic media.

  6. High CO2 Solubility, Permeability and Selectivity in Ionic Liquids with the Tetracyanoborate Anion

    SciTech Connect

    Mahurin, Shannon Mark; Hillesheim, Patrick C; Yeary, Joshua S; Jiang, Deen; Dai, Sheng

    2012-01-01

    Five different ionic liquids containing the tetracyanoborate anion were synthesized and evaluated for CO2 separation performance. Measured CO2 solubility values were exceptionally high compared to analogous ionic liquids with different anions and ranged from 0.128 mol L-1 atm-1 to 0.148 mol L-1 atm-1. In addition, CO2 permeability and CO2/N2 selectivity values were measured using a supported ionic liquid membrane architecture and the separations performance of the ionic liquid membranes exceeded the Robeson upper bound. These results establish the distinct potential of the tetracyanoborate, [B(CN)4], anion for the separation of CO2.

  7. High CO2 solubility, permeability and selectivity in ionic liquids with the tetracyanoborate anion

    SciTech Connect

    Mahurin, SM; Hillesheim, PC; Yeary, JS; Jiang, DE; Dai, S

    2012-01-01

    Five different ionic liquids containing the tetracyanoborate anion were synthesized and evaluated for CO2 separation performance. Measured CO2 solubility values were exceptionally high compared to analogous ionic liquids with different anions and ranged from 0.128 mol L-1 atm(-1) to 0.148 mol L-1 atm(-1). In addition, CO2 permeability and CO2/N-2 selectivity values were measured using a supported ionic liquid membrane architecture and the separations performance of the ionic liquid membranes exceeded the Robeson upper bound. These results establish the distinct potential of ionic liquids with the tetracyanoborate, [B(CN)(4)], anion for the separation of CO2.

  8. 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.

  9. Conductance hysteresis in the voltage dependent anion-selective channel

    PubMed Central

    Hoogerheide, David P.; Rostovtseva, Tatiana K.; Berezhkovskii, Alexander M.; Bezrukov, Sergey M.

    2015-01-01

    When the transmembrane voltage is periodically varied with time, the conductance of voltage-sensitive ion channels shows hysteretic behavior. Although this phenomenon has been used in studies of gating of the voltage-dependent anion channel, VDAC, from the outer mitochondrial membrane for nearly four decades, full hysteresis curves have never been reported, since the focus was only on the channel opening branches of the hysteresis loops. Here we study hysteretic response of a multichannel VDAC system to a triangular voltage ramp whose frequency varies within three orders of magnitude, ranging from 0.5 mHz to 0.2 Hz. We find that in this wide frequency range the area encircled by the hysteresis curves changes by less than a factor of three, thus suggesting a broad distribution of the characteristic times and strongly non-equilibrium behavior. At the same time, hysteresis branches corresponding to VDAC opening show quasi-equilibrium two-state behavior. This allows calculating usual equilibrium gating parameters, the gating charge and voltage of equipartitioning, which turn out to be virtually insensitive to the ramp frequency. To rationalize this peculiarity, we hypothesize that during voltage-induced closure and opening the system explores different regions of the complex free energy landscape, where, in the opening branch, it follows quasi-equilibrium paths. PMID:26094068

  10. Bifunctional anion-exchange resins with improved selectivity and exchange kinetics

    DOEpatents

    Alexandratos, Spiro D.; Brown, Gilbert M.; Bonnesen, Peter V.; Moyer, Bruce A.

    2000-01-01

    Disclosed herein are a class of anion exchange resins containing two different exchange sites with improved selectivity and sorptive capability for chemical species in solution, such as heptavalent technetium (as pertechnetate anion, TcO.sub.4.sup.-). The resins are prepared by first reacting haloalkylated crosslinked copolymer beads with a large tertiary amine in a solvent in which the resin beads can swell, followed by reaction with a second, smaller, tertiary amine to more fully complete the functionalization of the resin. The resins have enhanced selectivity, capacity, and exchange kinetics.

  11. 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.

  12. Highly selective fluorescence sensors for the fluoride anion based on carboxylate-bridged diiron complexes.

    PubMed

    Zhou, Yuhan; Dong, Xiaoliang; Zhang, Yixin; Tong, Peng; Qu, Jingping

    2016-04-28

    A new ligand bearing anthracene and its Fe(III) and Ru(III) derivatives have been synthesized and characterized exactly. The studies show that these dinuclear metal complexes serve as candidates of fluorescence chemosensors for anions. The interactions between these complexes and anions have been investigated by means of UV-Vis absorption spectra, fluorescence spectra, titration studies and (1)H-NMR. The results illustrated that two diiron complexes, [Cp*Fe(μ-SR)2(μ-η(2)-L)FeCp*][PF6] (, R = Me; , R = Et; L = 4-(3-(anthracen-9-ylmethyl)ureido)benzoate), showed rapid and selective recognition for the fluoride ion over other anions with strong enhancement of emission intensities. The sensing mechanisms indicate that the hydrogen bonding interaction has been observed between chemosensors and F(-). PMID:26619793

  13. Novel anthracene-based fluorescent sensor for selective recognition of acetate anions in protic media.

    PubMed

    Xu, Kuoxi; Kong, Huajie; Li, Qian; Song, Pan; Dai, Yanpeng; Yang, Li

    2015-02-25

    Novel 9-substituted anthracene derivatives were synthesized and characterized by IR, HRMS, (1)H and (13)C NMR. The fluorescence titration experiments were explored to study the interaction between the compounds and some anions, such as H2PO4(-), P2O7(4-), F(-), Cl(-), Br(-), I(-), AcO(-) in H2O (0.01 M HEPES, pH=7.4) under imitated physiological conditions. One of these compounds, bearing a phenylalaninol unit, showed specific fluorescence enhancement with acetate anion. The sensor L1 was found to present good selective fluorescence sensing ability to acetate anion through photoinduced electron-transfer mechanism in protic media. PMID:25282025

  14. 1,3-Alternate Tetraamido-Azacalix[4]arenes as Selective Anion Receptors.

    PubMed

    Canard, Gabriel; Edzang, Judicaelle Andeme; Chen, Zhongrui; Chessé, Matthieu; Elhabiri, Mourad; Giorgi, Michel; Siri, Olivier

    2016-04-11

    Six tetraaza[1.1.1.1]cyclophane derivatives bearing peripheral amide groups were prepared according to two distinct synthetic strategies that depend on the connection pattern between the aryl units. NMR experiments combined with the X-ray structures of two tetraamide derivatives 4 b and 10 show that these cavitands adopt a 1,3-alternate conformation both in solution and in the solid state. Consequently, the four amide groups of the aza[1.1.1.1]-m,m,m,m-cyclophane isomer 10 can contribute to the same recognition process towards neutral water molecules or anion guests. NMR experiments, mass spectrometry analyses and single-crystal X-ray structures confirm the anion-binding ability of this receptor. Absorption spectrophotometric titrations in nonpolar solvents provided evidence for the selectivity of 10 to chloride anions in the halide series, with a corresponding association constant Ka reaching 2.5 × 10(6) m(-1). PMID:26938487

  15. A new highly selective fluorescent turn-on chemosensor for cyanide anion.

    PubMed

    Chen, Yabin; Shi, Wei; Hui, Yonghai; Sun, Xinhua; Xu, Linxian; Feng, Lei; Xie, Zhengfeng

    2015-05-01

    A new simple molecule, 2-((2-phenyl-2H-1,2,3-triazol-4-yl)methylene)malononitrile (M1), was synthesized successfully by the Knoevenagel condensation reaction between 2-phenyl-1,2,3-triazole-4-carboxaldehyde and malononitrile. The receptor M1 is highly sensitive and selective to cyanide anion due to the nucleophilic addition of cyanide anion with M1. Distinct changes on UV-vis and fluorescence spectra can be detected with the addition of cyanide anion to the DMSO solution of M1. Optical properties of M1 were scarcely affected by the addition of other common background anions (F(-), Cl(-), Br(-), I(-), SCN(-), OH(-), CO4(2-), H2PO4(-), SO4(2-), HSO4(-), AcO(-), and NO3(-)) under the same condition. The detection limit of CN(-) reaches ~1.43 μM by M1 and the presence of background anions brought very slight interference for the detection of CN(-).

  16. Self-assembled metalla-bowls for selective sensing of multi-carboxylate anions.

    PubMed

    Mishra, Anurag; Vajpayee, Vaishali; Kim, Hyunuk; Lee, Min Hyung; Jung, Hyunji; Wang, Ming; Stang, Peter J; Chi, Ki-Whan

    2012-01-28

    Two new tetranuclear cationic metalla-bowls 4 and 5 were self-assembled from a bis-pyridine amide ligand (H(2)L) (1) and arene-ruthenium acceptors, [(Ru(2)(μ-η(4)-C(2)O(4))(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (2) and [Ru(2)(dhnd)(η(6)-p-cymene)(2)](O(3)SCF(3))(2) (dhnd = 6,11-dihydroxy-5,12-naphthacenedionato) (3), respectively. The metalla-bowls were characterized by multinuclear NMR, ESI-MS, UV-Vis spectroscopy, and single crystal X-ray diffraction study of 4. The crystal structure of 4 reveals unambiguous proof for the molecular shape of the metalla-bowl and the encapsulation of one triflate anion in the cavity through hydrogen bonding. The metalla-bowl 5 has been evaluated for anion binding studies by use of amide ligand as a hydrogen bond donor and arene-Ru acceptor as a signalling unit. UV-Vis titration studies showed that 5 selectively binds with multi-carboxylate anions such as oxalate, tartrate and citrate in a 1 : 1 fashion with high binding constants of 4.0-5.5 × 10(4) M(-1). Furthermore, the addition of multi-carboxylate anions into a solution of 5 gave rise to a large enhancement of fluorescence intensity attributable to the blocking of a photo-induced electron transfer process from the arene-ruthenium moiety to the amidic donor in 5. However, the fluorescence intensity almost remains unchanged upon addition of other anions including F(-), Cl(-), PF(6)(-), MeCOO(-), NO(3)(-) and PhCOO(-), as identically seen in the UV-Vis titration experiments, pointing to the high selectivity of 5 for the sensing of multi-carboxylate anions.

  17. Conformation-Selective Resonant Photoelectron Spectroscopy via Dipole-Bound States of Cold Anions.

    PubMed

    Huang, Dao-Ling; Liu, Hong-Tao; Ning, Chuan-Gang; Wang, Lai-Sheng

    2015-06-18

    Molecular conformation is important in chemistry and biochemistry. Conformers connected by low energy barriers can only be observed at low temperatures and are difficult to be separated. Here we report a new method to obtain conformation-selective spectroscopic information about dipolar molecular radicals via dipole-bound excited states of the corresponding anions cooled in a cryogenic ion trap. We observed two conformers of cold 3-hydroxyphenoxide anions [m-HO(C6H4)O(-)] in high-resolution photoelectron spectroscopy and measured different electron affinities, 18,850(8) and 18,917(5) cm(-1), for the syn and anti 3-hydroxyphenoxy radicals, respectively. We also observed dipole-bound excited states for m-HO(C6H4)O(-) with different binding energies for the two conformers due to the different dipole moments of the corresponding 3-hydroxyphenoxy radicals. Excitations to selected vibrational levels of the dipole-bound states result in conformation-selective photoelectron spectra. This method should be applicable to conformation-selective spectroscopic studies of any anions with dipolar neutral cores.

  18. Simultaneous Deposition of Mass Selected Anions and Cations: Improvements in Ion Delivery for Matrix Isolation Experiments

    NASA Astrophysics Data System (ADS)

    Goodrich, Michael E.; Moore, David T.

    2016-06-01

    A focus of the research in our group has been to develop improved methods for ion delivery in matrix isolation experiments. We have previously reported a method to co-deposit low energy, mass selected metal anions and a rare gas counter cation.a A modification allowing for mass selection of both the anion and cation will be discussed. Results from preliminary experiments of mass selected, low energy Cu- and SF5+ will also be highlighted. To our knowledge, these experiments are the first time two mass selected beams of ions have been simultaneously deposited into a cryogenic matrix. Co-deposition of the ions into an argon matrix doped with 0.02% CO at 20K resulted in the observation of bands assigned to SF5+ and anionic copper carbonyl complexes, Cu(CO)n- (n=1-3). Upon irradiation of the matrix with a narrow band, blue LED, the copper carbonyl complexes are converted to the neutral analogues, while the fate of the photodetached electrons can be directly tracked, as a decrease of the SF5+ band and a growth of the neutral SF5 band are observed. aLudwig, R. M.; Moore, D. T.; J. Chem. Phys. 139, 244202 (2013).

  19. Effect of anions on selective solubilization of zinc and copper in bacterial leaching of sulfide ores.

    PubMed

    Harahuc, L; Lizama, H M; Suzuki, I

    2000-07-20

    Bacterial leaching of sulfide ores using Thiobacillus ferrooxidans, Thiobacillus thiooxidans, or a combination of the two was studied at various concentrations of specific anions. Selective zinc and copper solubilization was obtained by inhibiting iron oxidation without affecting sulfur/sulfide oxidation. Phosphate reduced iron solubilization from a pyrite (FeS(2))-sphalerite (ZnS) mixture without significantly affecting zinc solubilization. Copper leaching from a chalcopyrite (CuFeS(2))-sphalerite mixture was stimulated by phosphate, whereas chloride accelerated zinc extraction. In a complex sulfide ore containing pyrite, chalcopyrite, and sphalerite, both phosphate and chloride reduced iron solubilization and increased copper extraction, whereas only chloride stimulated zinc extraction. Maximum leaching obtained was 100% zinc and 50% copper. Time-course studies of copper and zinc solubilization suggest the possibility of selective metal recovery following treatment with specific anions. PMID:10861398

  20. Structure and selectivity trends in crystalline urea-functionalized anion-binding capsules

    SciTech Connect

    Rajbanshi, Arbin; Custelcean, Radu

    2012-01-01

    A tripodal trisurea receptor (L1) persistently self-assembles with various divalent oxoanion salts M{sub n}X (M = Na, K, Mg, Ca, Cd; X = SO{sub 4}{sup 2-}, SO{sub 3}{sup 2-}, SeO{sub 4}{sup 2-}, CrO{sub 4}{sup 2-}) into isomorphous series of crystalline frameworks in three different compositions: MX(L1){sub 2}(H{sub 2}O){sub 6} (M = Mg, Ca, Cd) (1), Na{sub 2}X(L1){sub 2}(H{sub 2}O){sub 4} (2) and K{sub 2}X(L1){sub 2}(H{sub 2}O){sub 2} (3). Single-crystal X-ray structural analysis revealed that all three series of structures adopt a NaCl-type topology, consisting of alternating anionic X(L1){sub 2}{sup 2-} capsules and M(H{sub 2}O){sub 6}{sup 2+}, Na{sub 2}(H{sub 2}O){sub 4}{sup 2+} or K{sub 2}(H{sub 2}O){sub 2}{sup 2+} hydrated cations. The capsules provide a complementary environment to tetrahedral oxoanions via 12 hydrogen bonds from six urea groups lining the cavities of the capsules. The persistent formation of the capsules facilitated the investigation of structural trends and structure-selectivity relationships across series 1-3. First, it was found that the size of the capsules is relatively unresponsive to the change in the encapsulated anion, resulting in good shape and size recognition in the separation of anions by competitive crystallizations. Second, it was found that the size of the capsules varies linearly with the size of the external cation, which provides a way for tuning the anion encapsulation selectivity. However, no straightforward dependence was found between the size of the capsules and the relative selectivity for different-sized tetrahedral oxoanions in competitive crystallizations.

  1. Interaction of vitamin B1 with bovine serum albumin investigation using vitamin B1-selective electrode: potentiometric and molecular modeling study.

    PubMed

    Hosseinzadeh, Reza; Khorsandi, Khatereh

    2016-09-01

    Vitamin B1 or thiamin is one of the B vitamins. All B vitamins help the body to convert food (carbohydrates) into fuel (glucose), which produces energy. The B vitamins are necessary for healthy skin, eyes, hair, and liver. It also could help the nervous system function properly, and is necessary for brain functions. Drug interactions with protein can affect the distribution of the drug and eliminate the drug in living systems. In this study, the binding of thiamine hydrochloride (vitamin B1) to bovine serum albumin (BSA) was evaluated using a new proposed vitamin B1 (thiamine)-selective membrane electrode under various experimental conditions, such as pH, ionic strength, and protein concentration; in addition molecular modeling was applied as well. The binding isotherms plotted based on potentiometric data and analyzed using the Wyman binding potential concept. The apparent binding constant was determined and used for the calculation of intrinsic Gibbs free energy of binding. According to the electrochemical and molecular docking results, it can be concluded that the hydrophobic interactions and hydrogen binding are major interactions between BSA and vitamin B1.

  2. Interaction of vitamin B1 with bovine serum albumin investigation using vitamin B1-selective electrode: potentiometric and molecular modeling study.

    PubMed

    Hosseinzadeh, Reza; Khorsandi, Khatereh

    2016-09-01

    Vitamin B1 or thiamin is one of the B vitamins. All B vitamins help the body to convert food (carbohydrates) into fuel (glucose), which produces energy. The B vitamins are necessary for healthy skin, eyes, hair, and liver. It also could help the nervous system function properly, and is necessary for brain functions. Drug interactions with protein can affect the distribution of the drug and eliminate the drug in living systems. In this study, the binding of thiamine hydrochloride (vitamin B1) to bovine serum albumin (BSA) was evaluated using a new proposed vitamin B1 (thiamine)-selective membrane electrode under various experimental conditions, such as pH, ionic strength, and protein concentration; in addition molecular modeling was applied as well. The binding isotherms plotted based on potentiometric data and analyzed using the Wyman binding potential concept. The apparent binding constant was determined and used for the calculation of intrinsic Gibbs free energy of binding. According to the electrochemical and molecular docking results, it can be concluded that the hydrophobic interactions and hydrogen binding are major interactions between BSA and vitamin B1. PMID:26372107

  3. Selection and evaluation of adsorbents for the removal of anionic surfactants from laundry rinsing water.

    PubMed

    Schouten, Natasja; van der Ham, Louis G J; Euverink, Gert-Jan W; de Haan, André B

    2007-10-01

    Low-cost adsorbents were tested to remove anionic surfactants from laundry rinsing water to allow re-use of water. Adsorbents were selected corresponding to the different surfactant adsorption mechanisms. Equilibrium adsorption studies of linear alkyl benzene sulfonate (LAS) show that ionic interaction results in a high maximum adsorption capacity on positively charged adsorbents of 0.6-1.7 gLAS/g. Non-ionic interactions, such as hydrophobic interactions of LAS with non-ionic resins or activated carbons, result in a lower adsorption capacity of 0.02-0.6 gLAS/g. Negatively charged materials, such as cation exchange resins or bentonite clay, have negligible adsorption capacities for LAS. Similar results are obtained for alpha olefin sulfonate (AOS). Cost comparison of different adsorbents shows that an inorganic anion exchange material (layered double hydroxide) and activated carbons are the most cost-effective materials in terms of the amount of surfactant adsorbed per dollar worth of adsorbent.

  4. Anion induced azo-hydrazone tautomerism for the selective colorimetric sensing of fluoride ion

    NASA Astrophysics Data System (ADS)

    Satheshkumar, A.; El-Mossalamy, E. H.; Manivannan, R.; Parthiban, C.; Al-Harbi, L. M.; Kosa, S.; Elango, Kuppanagounder P.

    2014-07-01

    The design, synthesis, characterization and their anion sensing properties of two receptors capable of exhibiting azo-hydrazone tautomerism are reported. The anion sensing properties have been investigated using electronic, fluorescence and nuclear magnetic spectral studies in addition to electrochemical and visual detection experiments. Both the receptors selectively bind fluoride ion with >100 nm red-shift in the electronic spectrum and the color changes from yellow to red. The results of the spectral studies revealed that the sensing mechanism involves fluoride ion induced change of chromophore from Cdbnd N (hydrazone form) to Ndbnd N (azo form) in these receptors leading to the visible color change. Density Functional Theory calculations were conducted to rationalize the optical response of the receptors.

  5. Biomimetic ion nanochannels as a highly selective sequential sensor for zinc ions followed by phosphate anions.

    PubMed

    Han, Cuiping; Su, Haiyan; Sun, Zhongyue; Wen, Long; Tian, Demei; Xu, Kai; Hu, Junfeng; Wang, Aming; Li, Haibing; Jiang, Lei

    2013-07-01

    A novel biomimetic ion-responsive multi-nanochannel system is constructed by covalently immobilizing a metal-chelating ligand, 2,2'-dipicolylamine (DPA), in polyporous nanochannels prepared in a polymeric membrane. The DPA-modified multi-nanochannels show specific recognition of zinc ions over other common metal ions, and the zinc-ion-chelated nanochannels can be used as secondary sensors for HPO4(2-) anions. The immobilized DPA molecules act as specific-receptor binding sites for zinc ions, which leads to the highly selective zinc-ion response through monitoring of ionic current signatures. The chelated zinc ions can be used as secondary recognition elements for the capture of HPO4(2-) anions, thereby fabricating a sensing nanodevice for HPO4(2-) anions. The success of the DPA immobilization and ion-responsive events is confirmed by measurement of the X-ray photoelectron spectroscopy (XPS), contact angle (CA), and current-voltage (I-V) characteristics of the systems. The proposed nanochannel sensing devices display remarkable specificity, high sensitivity, and wide dynamic range. In addition, control experiments performed in complex matrices suggest that this sensing system has great potential applications in chemical sensing, biotechnology, and many other fields. PMID:23733212

  6. Acute toxicity and genotoxicity of five selected anionic and nonionic surfactants.

    PubMed

    Liwarska-Bizukojc, Ewa; Miksch, Korneliusz; Malachowska-Jutsz, Anna; Kalka, Joanna

    2005-03-01

    The results of four toxicity bioassays of selected anionic and nonionic surface active agents were presented. Three widely used anionic surfactants that belong to alkyl sulphates (AS), alkylbenzene sulphonates (LAS) and alkylpolyoxyethylene sulphates (AES) as well as nonionic surfactants: polyoxyethylene alkyl ethers (AE) and polyoxylethylene alkylphenyl ethers (APE) were tested. Three different toxicity assays to aquatic organisms: Physa acuta Draparnaud, Artemia salina and Raphidocelis subcapitata were applied. Additionally, the genotoxicity test with Bacillus subtilis M45 Rec- and H17 Rec+ strains was performed. The obtained results showed that none of the surfactants studied was genotoxic at the concentration 1000 mg l(-1). On the basis of toxicity tests to aquatic organisms all tested anionic surfactants were harmful (LC50 between 10 and 100 mg l(-1)), whereas nonionic ones were toxic (LC50 between 1 and 10 mg l(-1)) or even highly toxic (LC50 below 1 mg l(-1)). Moreover, the bigger was the molecular weight of the tested compound, the higher toxicity was observed.

  7. Anion exchange selectivity of surfactant modified clinoptilolite-rich tuff for environmental remediation.

    PubMed

    de Gennaro, Bruno; Catalanotti, Lilia; Bowman, Robert S; Mercurio, Mariano

    2014-09-15

    Lately, the functionalization of industrial minerals with high technological properties, such as natural zeolites, is shaping as a promising approach in environmental sphere. In fact, under the specific conditions, the surface functionalization via adsorption of cationic surfactants reverses the surface charge of the mineral, enabling zeolites to simultaneously interact either with organic contaminants or inorganic anions. This aspect allows zeolites to be used in the remediation of contaminated fluids. The present research shed new light on some still not fully understood aspects concerning exchange kinetics such as anion-exchange mechanisms and selectivity of surface modified minerals. For this purpose the mineralogical characterization and the surface properties evaluation (X Ray Powder Diffraction, chemical analysis, thermal analysis, ECEC and AEC) of a clinoptilolite-rich tuff were performed, and the anion exchange isotherms of the sample, modified with hexadecyltrimethylammonium chloride or bromide (HDTMA-Cl/-Br), were determined. Ion-exchange equilibrium data of uni-uni valent reaction were obtained by solutions containing Br(-), Cl(-), NO3(-) or ClO4(-). Liquid phase was analysed via high performance liquid chromatography. Thermodynamic quantities (Ka and ΔG(0)) were determined and compared with the Hofmeister series. The value of the ECEC, calculated in batch conditions, was about 137 mmol/kg, in good agreement with that evaluated in dynamic conditions, while the AEC data were different for the SMNZ-Br and -Cl samples, amounting to 137 and 106 mmol/kg, respectively, thus indicating a different compactness of the bilayer formed in the two cases. Moreover, the anion isotherm results and the mathematical evaluation of the thermodynamic parameters, demonstrated the good affinity of SMNZ-Br towards chloride, nitrate and perchlorate, and of SMNZ-Cl for nitrate and perchlorate, also endorsing the possibility of using the same thermodynamic approach developed to

  8. Enhanced liquid-liquid anion exchange using macrocyclic anion receptors: effect of receptor structure on sulphate-nitrate exchange selectivity

    SciTech Connect

    Moyer, Bruce A; Sloop Jr, Frederick {Fred} V; Fowler, Christopher J; Haverlock, Tamara; Kang, Hyun Ah; Delmau, Laetitia Helene; Bau, Diadra; Hossain, Alamgir; Bowman-James, Kristin; Shriver, James A.; Gross, Mr. Dustin E.; Bill, Nathan; Marquez, Manuel; Lynch, Vincent M.; Sessler, Jonathan L.

    2010-01-01

    When certain macrocyclic anion receptors are added to a chloroform solution of the nitrate form of a lipophilic quaternary ammonium salt (methyltri-C8,10-ammonium nitrate, Aliquat 336N), the extraction of sulphate from an aqueous sodium nitrate solution via exchange with the organic-phase nitrate is significantly enhanced. Eight macrocycles were surveyed, including two derivatives of a tetraamide macrocycle, five derivatives of calix[4]pyrrole and -decafluorocalix[5]pyrrole. Under the hypothesis that the enhancement originates from sulphate binding by the anion receptors in the chloroform phase, it was possible to obtain reasonable fits to the sulphate distribution survey data based on the formation of 1:1 and 2:1 receptor:sulphate complexes in the chloroform phase. Apparent 1:1 sulphate-binding constants obtained from the model in this system fell in the range . Comparison of the results for the various anion receptors included in this study reveals that sulphate binding is sensitive to the nature of the substituents on the parent macrocycle scaffolds in a way that does not follow straightforwardly from simple chemical expectations, such as electron-withdrawing effects on hydrogen-bond donor strength.

  9. Permian potentiometric analysis

    SciTech Connect

    Devary, J.L.

    1983-09-01

    Pacific Northwest Laboratory (PNL) was requested to analyze potentiometric data from the Wolfcamp Formation of the Permian System to evaluate the recommendations by the University of Texas/Bureau of Economic Geology (UT/BEG) that additional geohydrologic boreholes be drilled into the Wolfcamp. The UT/BEG recommended that two stratigraphic and two geohydrologic borings be drilled into the Permian System during FY83 and that several shallow hydrologic tests be made in the Dockum Formation. A geostatistical technique known as kriging was applied to objectively evaluate these geohydrologic borehole recommendations. The Deaf Smith County location appears to be an excellent choice for a borehole. No high quality potentiometric data are available from Deaf Smith County and a borehole location immediately upgradient from the candidate repository site is needed. Adding this borehole location to the potentiometric data base will significantly reduce field data uncertainty near the location being studied. The Swisher County location does not appear to be the best choice. High quality data values H2206 and H2360 are located immediately upgradient from the proposed repository site. The best placement of additional geohydrological boreholes in the Wolfcamp Formation depends strongly upon the proposed repository location. The variability of the potentiometric data causes estimation errors to rapidly increase away from locations of field measurements. Suggested locations for additional boreholes for the Deaf Smith investigations are in northwest Randall or central Potter Counties. Ideal borehole locations for the Swisher county studies appear to be in southeast Randall and Armstrong Counties.

  10. Direct ion speciation analysis with ion-selective membranes operated in a sequential potentiometric/time resolved chronopotentiometric sensing mode.

    PubMed

    Ghahraman Afshar, Majid; Crespo, Gastón A; Bakker, Eric

    2012-10-16

    Ion-selective membranes based on porous polypropylene membranes doped with an ionophore and a lipophilic cation-exchanger are used here in a new tandem measurement mode that combines dynamic electrochemistry and zero current potentiometry into a single protocol. Open circuit potential measurements yield near-nernstian response slopes in complete analogy to established ion-selective electrode methodology. Such measurements are well established to give direct information on the so-called free ion concentration (strictly, activity) in the sample. The same membrane is here also operated in a constant current mode, in which the localized ion depletion at a transition time is visualized by chronopotentiometry. This dynamic electrochemistry methodology gives information on the labile ion concentration in the sample. The sequential protocol is established on potassium and calcium ion-selective membranes. An increase of the ionophore concentration in the membrane to 180 mM makes it possible to determine calcium concentrations as high as 3 mM by chronopotentiometry, thereby making it possible to directly detect total calcium in undiluted blood samples. Recovery times after current perturbation depend on the current amplitude but can be kept to below 1 min for the polypropylene based ion-selective membranes studied here. Plasticized PVC as membrane material is less suited for this protocol, especially when the measurement at elevated concentrations is desired. An analysis of current amplitudes, transition times, and concentrations shows that the data are described by the Sand equation and that migration effects are insignificant. A numerical model describes the experimental findings with good agreement and gives guidance on the required selectivity in order to observe a well-resolved transition time and on the expected errors due to insufficient selectivity. The simulations suggest that the methodology compares well to that of open circuit potentiometry, despite giving

  11. Potentiometric surface and water-level difference maps of selected confined aquifers in Southern Maryland and Maryland’s Eastern Shore, 1975-2013

    USGS Publications Warehouse

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

    2014-01-01

    The potentiometric surface maps show water levels ranging from 165 feet above sea level to 199 feet below sea level. Water levels have declined by as much as 113 feet in the Aquia aquifer since 1982, 81 feet in the Magothy aquifer since 1975, and 61 and 95 feet in the Upper Patapsco and Lower Patapsco aquifer systems, respectively, since 1990.

  12. A thiolate anion buried within the hydrocarbon ruler perturbs PagP lipid acyl chain selection.

    PubMed

    Khan, M Adil; Moktar, Joel; Mott, Patrick J; Bishop, Russell E

    2010-03-23

    The Escherichia coli outer membrane phospholipid:lipid A palmitoyltransferase PagP exhibits remarkable selectivity because its binding pocket for lipid acyl chains excludes those differing in length from palmitate by a solitary methylene unit. This narrow detergent-binding hydrophobic pocket buried within the eight-strand antiparallel beta-barrel is known as the hydrocarbon ruler. Gly88 lines the acyl chain binding pocket floor, and its substitution can raise the floor to correspondingly shorten the selected acyl chain. An aromatic exciton interaction between Tyr26 and Trp66 provides an intrinsic spectroscopic probe located immediately adjacent to Gly88. The Gly88Cys PagP enzyme was engineered to function as a dedicated myristoyltransferase, but the mutant enzyme instead selected both myristoyl and pentadecanoyl groups, was devoid of the exciton, and displayed a 21 degrees C reduction in thermal stability. We now demonstrate that the structural perturbation results from a buried thiolate anion attributed to suppression of the Cys sulfhydryl group pK(a) from 9.4 in aqueous solvent to 7.5 in the hydrocarbon ruler microenvironment. The Cys thiol is sandwiched at the interface between a nonpolar and a polar beta-barrel interior milieu, suggesting that local electrostatics near the otherwise hydrophobic hydrocarbon ruler pocket serve to perturb the thiol pK(a). Neutralization of the Cys thiolate anion by protonation restores wild-type exciton and thermal stability signatures to Gly88Cys PagP, which then functions as a dedicated myristoyltransferase at pH 7. Gly88Cys PagP assembled in bacterial membranes recapitulates lipid A myristoylation in vivo. Hydrocarbon ruler-exciton coupling in PagP thus reveals a thiol-thiolate ionization mechanism for modulating lipid acyl chain selection.

  13. Data on heavy metals and selected anions in the Persian popular herbal distillates.

    PubMed

    Keshtkar, Mozhgan; Dobaradaran, Sina; Soleimani, Farshid; Karbasdehi, Vahid Noroozi; Mohammadi, Mohammad Javad; Mirahmadi, Roghayeh; Ghasemi, Fatemeh Faraji

    2016-09-01

    In this data article, we determined the concentration levels of heavy metals including Pb, Co, Cd, Mn, Mg, Fe and Cu as well as selected anions including [Formula: see text] , [Formula: see text], [Formula: see text] and [Formula: see text] in the most used and popular herbal distillates in Iran. It is well known that heavy metals may pose a serious health hazard due to their bioaccumulation throughout the trophic chain ("Heavy metals (Cd, Cu, Ni and Pb) content in two fish species of Persian Gulf in Bushehr Port, Iran" (Dobaradaran et al., 2013) [1]; "Comparative investigation of heavy metal, trace, and macro element contents in commercially valuable fish species harvested off from the Persian Gulf" (Abadi et al., 2015) [2]) as well as some other environmental pollutions, "Assessment of sediment quality based on acid-volatile sulfide and simultaneously extracted metals in heavily industrialized area of Asaluyeh, Persian Gulf: concentrations, spatial distributions, and sediment bioavailability/toxicity" (Arfaeinia et al., 2016) [3]. The concentration levels of heavy metals and anions in herbal distillates samples were determined using flame atomic absorption spectrometry (FAAS, Varian AA240, Australia) and a spectrophotometer (M501 Single Beam Scanning UV/VIS, UK) respectively. PMID:27274526

  14. Optimizing mass spectrometric detection for ion chromatographic analysis. I. Common anions and selected organic acids.

    PubMed

    Wang, Jinyuan; Schnute, William C

    2009-11-01

    We describe a systematic method of optimizing mass spectrometric (MS) detection for ion chromatographic (IC) analysis of common anions and three selected organic acids using response surface methodology (RSM). RSM was utilized in this study because it minimized the number of experiments required to achieve the optimum MS response and included the interactions between individual parameters for multivariable optimization. Five MS parameters, including probe temperature, nebulizer gas, assistant makeup flow, needle voltage and cone voltage, were screened and systematically optimized by two steps. Central composite design (CCD) was used to design the experiment points and a quadratic model was applied to fit the experimental data. Analysis of variance (ANOVA) was carried out to evaluate the validity of the statistical model and to determine the most significant parameters for MS response. The optimum MS conditions for each analyte were summarized and the method optimum condition was achieved by applying desirability function. Our observation showed good agreements between statistically predicted optimum response and the responses collected at the predicted optimum condition. Operable range of each parameter (with normalized MS response greater than 0.8 for each analyte) was provided for general anionic IC/MS applications.

  15. Beer classification by means of a potentiometric electronic tongue.

    PubMed

    Cetó, Xavier; Gutiérrez-Capitán, Manuel; Calvo, Daniel; del Valle, Manel

    2013-12-01

    In this work, an electronic tongue (ET) system based on an array of potentiometric ion-selective electrodes (ISEs) for the discrimination of different commercial beer types is presented. The array was formed by 21 ISEs combining both cationic and anionic sensors with others with generic response. For this purpose beer samples were analyzed with the ET without any pretreatment rather than the smooth agitation of the samples with a magnetic stirrer in order to reduce the foaming of samples, which could interfere into the measurements. Then, the obtained responses were evaluated using two different pattern recognition methods, principal component analysis (PCA), which allowed identifying some initial patterns, and linear discriminant analysis (LDA) in order to achieve the correct recognition of sample varieties (81.9% accuracy). In the case of LDA, a stepwise inclusion method for variable selection based on Mahalanobis distance criteria was used to select the most discriminating variables. In this respect, the results showed that the use of supervised pattern recognition methods such as LDA is a good alternative for the resolution of complex identification situations. In addition, in order to show an ET quantitative application, beer alcohol content was predicted from the array data employing an artificial neural network model (root mean square error for testing subset was 0.131 abv).

  16. Potentiometric titrations using pencil and graphite sensors

    SciTech Connect

    Selig, W.S.

    1984-01-01

    The cost of various commercial indicating electrodes ranges from about $40 for pH electrodes to as much as $355 for a potassium ion-selective electrode. This cost can be reduced to less than $1.50, and in some cases to mere pennies by making sensors from graphite rods and pencils for use in potentiometric titrations. The same sensor can be used for many types of these titrations (acid/base, compleximetric, precipitation, and redox). 8 references, 2 tables.

  17. Electricity generation and local ion ordering induced by cation-controlled selective anion transportation through graphene oxide membranes

    NASA Astrophysics Data System (ADS)

    Sun, Pengzhan; Deng, Hui; Zheng, Feng; Wang, Kunlin; Zhong, Minlin; Zhang, Yingjiu; Kang, Feiyu; Zhu, Hongwei

    2014-12-01

    A cation-controlled selective anion transportation through graphene oxide (GO) membranes is demonstrated in this work. The results reveal that the trans-membrane transport of different anions can be modulated by the corresponding cations. The diverse interactions among anions, cations, and the negatively charged GO membranes are responsible for selective anion permeation through GO membranes. During the ion penetration, electrical potential differences can be generated across drain and source as well as across GO membranes; based on this, the ion distributions around GO membranes can be determined. The results indicate that local ion ordering can be achieved by GO membranes. Interestingly, for the cases of KNO3, Ca(NO3)2, and Ba(NO3)2, alternate aggregations of metallic cations and NO3- anions can be formed around GO membranes, demonstrating the fantastic ability of these membranes for ordering the ions locally in solutions. In addition, based on the electrical potential differences generated by different salts, chlorides are demonstrated to be ideal sources for efficient practical electricity production compared to sulfates and nitrates, while the different voltage signals generated can be used to identify different source solutions for liquid sensing applications. These results indicate that GO membranes can find potential applications in membrane separation, energy generation, ion recognition, and local ion organizing.

  18. Selective Anion Exchange Resins for the Removal of Perchlorate [(CIO{sub 4}{sup -})] from Groundwater

    SciTech Connect

    Gu, B.

    1999-05-20

    The primary objective of this project was to evaluate a novel bifunctional anion exchange resin for the cost-effective, in situ treatment of groundwater contaminated with perchlorate (ClO{sub 4}{sup -}). Both laboratory and field studies were performed to determine the selectivity and capacity of the bifunctional synthetic resins to sorb ClO{sub 4}{sup -} from simulated or actual contaminated groundwater. A number of synthetic bifunctional resins, including two commercial versions made by Purolite International and three commercially available, mono-functional resins, were tested. Initial laboratory batch and column breakthrough studies determined the best synthetic resins and the optimal conditions for the field experiment. Laboratory results indicated that the bifunctional synthetic resins, D-3696 and RO-02-119 were highly selective toward ClO{sub 4}{sup -} and performed {approx}5 times better than the best commercial nitrate resin (Purolite{reg_sign} A-520E) and more than an order of magnitude better than some nonselective commercial resins (e.g. Amberlite{reg_sign} IRA-900). The bifunctional resins were particularly effective in removing trace quantities of ClO{sub 4}{sup -} in groundwater to below the detection limit ({approx} 3 {micro}g/L). A field trial demonstrated that the bifunctional resin (D-3696) was able to treat {approx} 110,000 bed volumes of groundwater before a 10% breakthrough of ClO{sub 4}{sup -} occurred under the column flow-through conditions (running at {approx} 2 bed volumes per minute). On the other hand, the Purolite{reg_sign} A-520E resin was able to treat {approx} 23,000 bed volumes of groundwater under the same experimental conditions. No pretreatment was needed to remove either dissolved organic matter or other competing anions (such as SO{sub 4}{sup 2-} or NO{sub 3}{sup -}) in the groundwater, and the treatment process did not alter the water quality by removing or adding secondary by-products because of the high selectivity of the

  19. A microporous anionic metal-organic framework for a highly selective and sensitive electrochemical sensor of Cu(2+) ions.

    PubMed

    Jin, Jun-Cheng; Wu, Ju; Yang, Guo-Ping; Wu, Yun-Long; Wang, Yao-Yu

    2016-06-28

    We first reported an anionic metal-organic framework for electrode material for the electrochemical detection of Cu(2+). The modified electrode shows an excellent selectivity, high stability and sensitivity, wide linear range and lower detection limit. This strategy for generating new electrode materials will be useful for preparing new sensors and reporters for biological systems.

  20. 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

  1. Tris(triazole) tripodal receptors as selective probes for citrate anion recognition and multichannel transition and heavy metal cation sensing.

    PubMed

    González, María del Carmen; Otón, Francisco; Espinosa, Arturo; Tárraga, Alberto; Molina, Pedro

    2015-02-01

    The three-armed pyrenyl-triazole receptor 1 behaves as a highly selective fluorescent molecular sensor for citrate anions over similar carboxylates such as malate or tartrate. In addition, this receptor senses Cu(2+) cations through absorption and emission channels even in the presence of Hg(2+) metal cations. The related three-armed ferrocenyl-triazole receptor 2 behaves as a highly selective dual (redox and chromogenic) chemosensor molecule for Pb(2+) metal cations.

  2. Studies on bis(crown ether)-based ion-selective electrodes for the potentiometric determination of sodium and potassium in serum.

    PubMed

    Moody, G J; Saad, B B; Thomas, J D

    1989-01-01

    Bis(crown ether)-based ion-selective electrodes for sodium and potassium are described, based on the bis[(12-crown-4)-2-ylmethyl]-2-dodecyl-2-methyl malonate sensor(I) for sodium and the bis[(benzo-15-crown-5)-15-ylmethyl] pimelate sensor(II) for potassium. The best results were obtained when the sensors were used in association with 2-nitrophenyl octyl ether as plasticising solvent mediator and potassium tetrakis(4-chlorophenyl)borate as anion excluder in poly(vinyl chloride) matrices. Electrode slopes were near-Nernstian, with detection limits of less than 10(-5) M. The electrode features are compared with those of a sodium glass membrane electrode, for sensor I, and with a valinomycin-based potassium electrode, for sensor II. The electrodes are also discussed in relation to others reported for sensors I and II and are shown to be superior. However, although the electrodes described offer promising alternatives to glass electrodes for sodium and valinomycin electrodes for potassium, data for sodium and potassium measurements in blood serum indicate a need for further research in order to improve the correlation with flame photometric measurements.

  3. Extraction of selected organic bases by bis 1,2-dicarbollylcobaltate anion from water into chloroform

    NASA Astrophysics Data System (ADS)

    Navrátil, O.; Skaličan, Z.; Kobliha, Z.; Halámek, E.

    1999-01-01

    Bis-1,2-dicarbollylcobaltate anion, labelled by 60Co, forms ionic associates with cations of some organic bases and quaternary salts, especially those causing psychic effect on human organism. Their stability and partition between aqueous 0,1 mol. L-1 HCl and chloroform were investigated radiometrically. A method of competitive extraction was proposed for some anions of dyes which were so far used for extraction-spectrophotometric determination of some bases.

  4. Selective detection of multicarboxylate anions based on "turn on" electron transfer by self-assembled molecular rectangles.

    PubMed

    Mishra, Anurag; Lee, Sunmi; Kim, Hyunuk; Cook, Timothy R; Stang, Peter J; Chi, Ki-Whan

    2012-11-01

    Two new large molecular rectangles (4 and 5) were obtained by the reaction of two different dinuclear arene ruthenium complexes [Ru(2)(arene)(2)(OOOO)(2)Cl(2)] (arene = p-cymene; OOOO = 2,5-dihydroxy-1,4-benzoquinonato (2), 6,11-dihydroxy-5,12-naphthacene dionato (3)) with the unsymmetrical amide NN (N-[4-(pyridin-4-ylethynyl)phenyl]isonicotinamide) donor ligand 1 in methanol in the presence of AgO(3)SCF(3), forming tetranuclear cations of the general formula [Ru(4)(arene)(4)(NN)(2)(OOO O)(2)](4+). Both rectangles were isolated in good yields as triflate salts and were characterized by multinuclear NMR, ESI-MS, UV/Vis, and photoluminescence spectroscopy. The crystal structure of 5 was determined by X-ray diffraction. Luminescent rectangle 5 was used for anion sensing with an amide ligand as a hydrogen-bond donor and an arene-ruthenium acceptor as a signaling unit. Rectangle 5 strongly bound multicarboxylate anions, such as oxalate, tartrate, and citrate, in UV/Vis titration experiments in 1:1 ratios, in contrast to monoanions, such as F(-), Cl(-), NO(3)(-), PF(6)(-), CH(3)COO(-), and C(6)H(5)COO(-). The fluorescence titration experiment showed a large fluorescence enhancement of 5 upon binding to multicarboxylate anions, which could be attributed to blocking of the photoinduced electron transfer process from the arene-ruthenium moiety to the amidic donor in 5; this was likely to be a result of hydrogen bonding between the ligand and the anion. On the other hand, rectangle 5 was not selective towards any other anions. To the naked eye, multicarboxylate anions in a solution of 5 in methanol appear greenish upon irradiation with UV light.

  5. Charged residues distribution modulates selectivity of the open state of human isoforms of the voltage dependent anion-selective channel.

    PubMed

    Amodeo, Giuseppe Federico; Scorciapino, Mariano Andrea; Messina, Angela; De Pinto, Vito; Ceccarelli, Matteo

    2014-01-01

    Voltage Dependent Anion-selective Channels (VDACs) are pore-forming proteins located in the outer mitochondrial membrane. They are responsible for the access of ions and energetic metabolites into the inner membrane transport systems. Three VDAC isoforms exist in mammalian, but their specific role is unknown. In this work we have performed extensive (overall ∼5 µs) Molecular Dynamics (MD) simulations of the human VDAC isoforms to detect structural and conformational variations among them, possibly related to specific functional roles of these proteins. Secondary structure analysis of the N-terminal domain shows a high similarity among the three human isoforms of VDAC but with a different plasticity. In particular, the N-terminal domain of the hVDAC1 is characterized by a higher plasticity, with a ∼20% occurrence for the 'unstructured' conformation throughout the folded segment, while hVDAC2, containing a peculiar extension of 11 amino acids at the N-terminal end, presents an additional 310-helical folded portion comprising residues 10' to 3, adhering to the barrel wall. The N-terminal sequences of hVDAC isoforms are predicted to have a low flexibility, with possible consequences in the dynamics of the human VDACs. Clear differences were found between hVDAC1 and hVDAC3 against hVDAC2: a significantly modified dynamics with possible important consequence on the voltage-gating mechanism. Charge distribution inside and at the mouth of the pore is responsible for a different preferential localization of ions with opposite charge and provide a valuable rationale for hVDAC1 and hVDAC3 having a Cl-/K+ selectivity ratio of 1.8, whereas hVDAC2 of 1.4. Our conclusion is that hVDAC isoforms, despite sharing a similar scaffold, have modified working features and a biological work is now requested to give evidence to the described dissimilarities. PMID:25084457

  6. 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

    2016-01-01

    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

  7. 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

  8. Functional comparison of mouse slc26a6 anion exchanger with human SLC26A6 polypeptide variants: differences in anion selectivity, regulation, and electrogenicity.

    PubMed

    Chernova, Marina N; Jiang, Lianwei; Friedman, David J; Darman, Rachel B; Lohi, Hannes; Kere, Juha; Vandorpe, David H; Alper, Seth L

    2005-03-01

    proteins differ in anion selectivity, transport mechanism, and acute regulation, but both mediate electroneutral Cl(-)/HCO(3)(-) exchange. PMID:15548529

  9. Micromechanical potentiometric sensors

    SciTech Connect

    Thundat, T.G.

    2000-01-25

    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.

  10. 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.

  11. Water-Stable Anionic Metal-Organic Framework for Highly Selective Separation of Methane from Natural Gas and Pyrolysis Gas.

    PubMed

    Li, Lan; Wang, Xusheng; Liang, Jun; Huang, Yuanbiao; Li, Hongfang; Lin, Zujin; Cao, Rong

    2016-04-20

    A 3D water-stable anionic metal-organic framework [Zn4(hpdia)2]·[NH2(CH3)2]·3DMF·4H2O (FJI-C4) was constructed based on an elaborate phosphorus-containing ligand 5,5'-(hydroxyphosphoryl)diisophthalic acid (H5hpdia). FJI-C4 with narrow one-dimensional (1D) pore channels exhibits high selectivity of C3H8/CH4 and C2H2/CH4. It is the first time for the MOF which contains phosphorus for selective separation of methane from natural gas and pyrolysis gas.

  12. Chloride-selective electrodes based on "two-wall" aryl-extended calix[4]pyrroles: combining hydrogen bonds and anion-π interactions to achieve optimum performance.

    PubMed

    Sabek, Jad; Adriaenssens, Louis; Guinovart, Tomàs; Parra, Enrique J; Rius, F Xavier; Ballester, Pablo; Blondeau, Pascal

    2015-01-01

    The performance of chloride-selective electrodes based on "two-wall" aryl-extended calix[4]pyrroles and multiwall carbon nanotubes is presented. The calix[4]pyrrole receptors bear two phenyl groups at opposite meso-positions. When the meso-phenyl groups are decorated with strong electron-withdrawing substituents, attractive anion-π interactions may exist between the receptor's aromatic walls and the sandwiched anion. These anion-π interactions are shown to significantly affect the selectivity of the electrodes. Calix[4]pyrrole, bearing a p-nitro withdrawing group on each of the meso-phenyl rings, afforded sensors that display anti-Hofmeister behavior against the lipophilic salicylate and nitrate anions. Based on the experimental data, a series of principles that help in predicting the suitability of synthetic receptors for use as anion-specific ionophores is discussed. Finally, the sensors deliver excellent results in the direct detection of chloride in bodily fluids.

  13. 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. PMID:26838835

  14. Potentiometric surface and water-level difference maps of selected confined aquifers of Southern Maryland and Maryland's Eastern Shore, 1975-2011

    USGS Publications Warehouse

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

    2012-01-01

    Groundwater is the principal source of freshwater supply in most of Southern Maryland and Maryland's Eastern Shore. It is also the source of freshwater supply used in the operation of the Calvert Cliffs, Chalk Point, and Morgantown power plants. Increased groundwater withdrawals over the last several decades have caused groundwater levels to decline. This report presents potentiometric surface maps of the Aquia, Magothy, upper Patapsco, lower Patapsco, and Patuxent aquifers using water levels measured during September 2011. Water-level difference maps also are presented for the first four of these aquifers. The water-level differences in the Aquia aquifer are shown using groundwater-level data from 1982 and 2011, whereas the water-level differences in the Magothy aquifer are presented using data from 1975 and 2011. Water-level difference maps in both the upper Patapsco and lower Patapsco aquifers are presented using data from 1990 and 2011. These maps show cones of depression ranging from 25 to 198 feet (ft) below sea level centered on areas of major withdrawals. Water levels have declined by as much as 112 ft in the Aquia aquifer since 1982, 85 ft in the Magothy aquifer since 1975, and 47 and 71 ft in the upper Patapsco and lower Patapsco aquifers, respectively, since 1990.

  15. A mercury(II) selective sensor based on N,N'-bis(salicylaldehyde)-phenylenediamine as neutral carrier for potentiometric analysis in water samples.

    PubMed

    Abu-Shawish, Hazem M

    2009-08-15

    Mercuric ions in water samples were determined by a new modified carbon paste electrode based on N,N'-bis(salicylaldehyde)-phenylenediamine (salophen) as a chemical modifier. The construction, performance, and applications of mercury carbon paste electrode are described. The electrode displays a linear log[Hg(2+)] versus EMF response over a wide concentration range of 3.2 x 10(-7) to 3.2 x 10(-4) with Nernstian slope of 58.8+/-0.3 mV/decade with limit of detection 1.5 x 10(-7) over the pH range 3.8-7.8; the presence of the complex Hg(OH)(+) ion explains the slope of the response curve. The proposed sensor shows a reasonable discrimination ability towards Hg(II) in comparison to some alkali, alkaline earth transition and heavy metal ions. The modified electrode was applied as indicator electrode in potentiometric titration and successfully used to determine mercury(II) in water samples with satisfactory results.

  16. Selective removal of alkali metal cations from multiply-charged ions via gas-phase ion/ion reactions using weakly coordinating anions.

    PubMed

    Luongo, Carl A; Bu, Jiexun; Burke, Nicole L; Gilbert, Joshua D; Prentice, Boone M; Cummings, Steven; Reed, Christopher A; McLuckey, Scott A

    2015-03-01

    Selective removal of alkali metal cations from mixed cation multiply-charged peptide ions is demonstrated here using gas-phase ion/ion reactions with a series of weakly coordinating anions (WCAs), including hexafluorophosphate (PF6 (-)), tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF), tetrakis(pentafluorophenyl)borate (TPPB), and carborane (CHB11Cl11 (-)). In all cases, a long-lived complex is generated by dication/anion condensation followed by ion activation to compare proton transfer with alkali ion transfer from the peptide to the anion. The carborane anion was the only anion studied to undergo dissociation exclusively through loss of the metallated anion, regardless of the studied metal adduct. All other anions studied yield varying abundances of protonated and metallated peptide depending on the peptide sequence and the metal identity. Density functional theory calculations suggest that for the WCAs studied, metal ion transfer is most strongly favored thermodynamically, which is consistent with the experimental results. The carborane anion is demonstrated to be a robust reagent for the selective removal of alkali metal cations from peptide cations with mixtures of excess protons and metal cations. PMID:25560986

  17. Selective Removal of Alkali Metal Cations from Multiply-Charged Ions via Gas-Phase Ion/Ion Reactions Using Weakly Coordinating Anions

    NASA Astrophysics Data System (ADS)

    Luongo, Carl A.; Bu, Jiexun; Burke, Nicole L.; Gilbert, Joshua D.; Prentice, Boone M.; Cummings, Steven; Reed, Christopher A.; McLuckey, Scott A.

    2015-03-01

    Selective removal of alkali metal cations from mixed cation multiply-charged peptide ions is demonstrated here using gas-phase ion/ion reactions with a series of weakly coordinating anions (WCAs), including hexafluorophosphate (PF6 -), tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BARF), tetrakis(pentafluorophenyl)borate (TPPB), and carborane (CHB11Cl11 -). In all cases, a long-lived complex is generated by dication/anion condensation followed by ion activation to compare proton transfer with alkali ion transfer from the peptide to the anion. The carborane anion was the only anion studied to undergo dissociation exclusively through loss of the metallated anion, regardless of the studied metal adduct. All other anions studied yield varying abundances of protonated and metallated peptide depending on the peptide sequence and the metal identity. Density functional theory calculations suggest that for the WCAs studied, metal ion transfer is most strongly favored thermodynamically, which is consistent with the experimental results. The carborane anion is demonstrated to be a robust reagent for the selective removal of alkali metal cations from peptide cations with mixtures of excess protons and metal cations.

  18. Enhancement of molecular shape selectivity by in situ anion-exchange in poly(octadecylimidazolium) silica column.

    PubMed

    Qiu, Hongdeng; Mallik, Abul K; Takafuji, Makoto; Liu, Xia; Jiang, Shengxiang; Ihara, Hirotaka

    2012-04-01

    This paper demonstrates that in situ anion exchange could be successfully applied as a new method for modifying the surface properties of a poly(octadecylimidazolium)-grafted silica stationary phase to tune and enhance selectivity. Specifically, the original stationary phase was prepared by surface-initiated radical chain-transfer polymerization of 1-vinyl-3-octadecylimidazolium bromide as an ionic liquid monomer; the Br(-) counter anion was then exchanged for methyl orange via an in-column process. As evaluated via the separation of constrained isomers of polycyclic aromatic hydrocarbons (PAHs), the in situ exchange enhanced the molecular shape-selectivity performance. Enhanced selectivity was also confirmed using Standard Reference Material (SRM) 869b (column selectivity test mixture) and SRM 1647e (16 priority pollutant PAHs). The reproducibility of new column was tested via the separation of pyrene, triphenylene, benzo[a]anthracene and chrysene with methanol as eluent at 10 °C and the RSD values (n=12) of the retention factors of them are within 0.27-0.77%. PMID:22099220

  19. A click fluorophore sensor that can distinguish Cu(II) and Hg(II) via selective anion-induced demetallation.

    PubMed

    Lau, Yu Heng; Price, Jason R; Todd, Matthew H; Rutledge, Peter J

    2011-03-01

    A cyclam-based fluorescent sensor featuring a novel triazole pendant arm has been synthesised using click chemistry. The sensor is highly responsive to both Cu(II) and Hg(II) in neutral aqueous solution and displays excellent selectivity in the presence of various competing metal ions in 50-fold excess. The addition of specific anions such as I(-) and S(2)O(3)(2-) causes a complete revival of fluorescence only in the case of Hg(II), providing a simple and effective method for distinguishing solutions containing Cu(II), Hg(II) or a mixture of both ions, even in doped seawater samples. X-ray crystal structures of both the Hg(II) sensor complex and a model Cu(II) complex show that pendant triazole coordination occurs through the central nitrogen atom (N2), providing to the best of our knowledge the first reported examples of this unusual coordination mode in macrocycles. Fluorescence, mass spectrometry and (1)H NMR experiments reveal that the mechanism of anion-induced fluorescence revival involves either displacement of pendant coordination or complete removal of the Hg(II) from the macrocycle, depending on the anion.

  20. Engineering the electrochemical capacitive properties of graphene sheets in ionic-liquid electrolytes by correct selection of anions.

    PubMed

    Shi, Minjie; Kou, Shengzhong; Yan, Xingbin

    2014-11-01

    Graphene sheet (GS)-ionic liquid (IL) supercapacitors are receiving intense interest because their specific energy density far exceeds that of GS-aqueous electrolytes supercapacitors. The electrochemical properties of ILs mainly depend on their diverse ions, especially anions. Therefore, identifying suitable IL electrolytes for GSs is currently one of the most important tasks. The electrochemical behavior of GSs in a series of ILs composed of 1-ethyl-3-methylimidazolium cation (EMIM(+)) with different anions is systematically studied. Combined with the formula derivation and building models, it is shown that the viscosity, ion size, and molecular weight of ILs affect the electrical conductivity of ILs, and thus, determine the electrochemical performances of GSs. Because the EMIM-dicyanamide IL has the lowest viscosity, ion size, and molecular weight, GSs in it exhibit the highest specific capacitance, smallest resistance, and best rate capability. In addition, because the tetrafluoroborate anion (BF4(-)) has the best electrochemical stability, the GS-[EMIM][BF4] supercapacitor has the widest potential window, and thus, displays the largest energy density. These results may provide valuable information for selecting appropriate ILs and designing high-performance GS-IL supercapacitors to meet different needs. PMID:25146489

  1. High-sensitivity microchip electrophoresis determination of inorganic anions and oxalate in atmospheric aerosols with adjustable selectivity and conductivity detection.

    PubMed

    Noblitt, Scott D; Schwandner, Florian M; Hering, Susanne V; Collett, Jeffrey L; Henry, Charles S

    2009-02-27

    A sensitive and selective separation of common anionic constituents of atmospheric aerosols, sulfate, nitrate, chloride, and oxalate, is presented using microchip electrophoresis. The optimized separation is achieved in under 1 min and at low background electrolyte ionic strength (2.9 mM) by combining a metal-binding electrolyte anion (17 mM picolinic acid), a sulfate-binding electrolyte cation (19 mM HEPBS), a zwitterionic surfactant with affinity towards weakly solvated anions (19 mM N-tetradecyl,N,N-dimethyl-3-ammonio-1-propansulfonate), and operation in counter-electroosmotic flow (EOF) mode. The separation is performed at pH 4.7, permitting pH manipulation of oxalate's mobility. The majority of low-concentration organic acids are not observed at these conditions, allowing for rapid subsequent injections without the presence of interfering peaks. Because the mobilities of sulfate, nitrate, and oxalate are independently controlled, other minor constituents of aerosols can be analyzed, including nitrite, fluoride, and formate if desired using similar separation conditions. Contact conductivity detection is utilized, and the limit of detection for oxalate (S/N=3) is 180 nM without stacking. Sensitivity can be increased with field-amplified sample stacking by injecting from dilute electrolyte with a detection limit of 19 nM achieved. The high-sensitivity, counter-EOF operation, and short analysis time make this separation well-suited to continuous online monitoring of aerosol composition.

  2. Manganese(III) porphyrin-based potentiometric sensors for diclofenac assay in pharmaceutical preparations.

    PubMed

    Vlascici, Dana; Pruneanu, Stela; Olenic, Liliana; Pogacean, Florina; Ostafe, Vasile; Chiriac, Vlad; Pica, Elena Maria; Bolundut, Liviu Calin; Nica, Luminita; Fagadar-Cosma, Eugenia

    2010-01-01

    Two manganese(III) porphyrins: manganese(III) tetraphenylporphyrin chloride and manganese(III)-tetrakis(3-hydroxyphenyl)porphyrin chloride were tested as ionophores for the construction of new diclofenac-selective electrodes. The electroactive material was incorporated either in PVC or a sol-gel matrix. The effect of different plasticizers and additives (anionic and cationic) on the potentiometric response was studied. The best results were obtained for the PVC membrane plasticized with dioctylphtalate and having sodium tetraphenylborate as a lipophilic anionic additive incorporated. The sensor response was linear in the concentration range 3 × 10(-6) - 1 × 10(-2) M with a slope of -59.7 mV/dec diclofenac, a detection limit of 1.5 × 10(-6) M and very good selectivity coefficients. It was used for the determination of diclofenac in pharmaceutical preparations, by direct potentiometry. The results were compared with those obtained by the HPLC reference method and a good agreement was found between the two methods.

  3. Simple sensor for potentiometric titrations

    SciTech Connect

    Selig, W.

    1982-01-01

    A sensor for potentiometric titrations was prepared by coating a spectroscopic graphite rod with a solution of poly(vinyl chloride) and dioctylphthalate in tetrahydrofuran. The reference was an Ag/AgCl single-junction electrode. The sensor was used in the following potentiometric titrations: (1) precipitation titrations, (2) acid-base titrations, (3) compleximetric titrations, and (4) redox titrations. A survey of its use in such titrations is presented. Preparation of the coated-graphite sensor is simple and rapid. Moreover, it is quite inexpensive. A limitation is its applicability in aqueous media only, because organic solvents will dissolve the membrane. 5 figures, 4 tables.

  4. Ion-exchange selectivity of tertiary pyridine-type anion-exchange resin for treatment of spent nuclear fuels

    SciTech Connect

    Nogami, Masanobu; Aida, Masao; Fujii, Yasuhiko; Maekawa, Akira; Ohe, Shinobu; Kawai, Hiroomi; Yoneda, Morihiro

    1996-09-01

    The tertiary pyridine-type anion-exchange resin has been synthesized for the treatment of spent nuclear fuels and high-level radioactive waste. This resin, with a uniform diameter of 60 {micro}m, is mechanically strong enough and shows no swelling or shrinking regardless of its chemical forms. Systematic analysis was made of the adsorption selectivities of the resin in HCl solutions for a number of cations that exist in spent fuels, such as uranium and fission product elements. The results indicate that the resin is suitable to be used for the treatment of spent fuels and high-level radioactive waste.

  5. Mechanism of anion selectivity and stoichiometry of the Na+/I- symporter (NIS).

    PubMed

    Paroder-Belenitsky, Monika; Maestas, Matthew J; Dohán, Orsolya; Nicola, Juan Pablo; Reyna-Neyra, Andrea; Follenzi, Antonia; Dadachova, Ekaterina; Eskandari, Sepehr; Amzel, L Mario; Carrasco, Nancy

    2011-11-01

    I(-) uptake in the thyroid, the first step in thyroid hormone biosynthesis, is mediated by the Na(+)/I(-) symporter (NIS) with an electrogenic 2Na(+):1I(-) stoichiometry. We have obtained mechanistic information on NIS by characterizing the congenital I(-) transport defect-causing NIS mutant G93R. This mutant is targeted to the plasma membrane but is inactive. Substitutions at position 93 show that the longer the side chain of the neutral residue at this position, the higher the K(m) for the anion substrates. Unlike WT NIS, which mediates symport of Na(+) and the environmental pollutant perchlorate electroneutrally, G93T/N/Q/E/D NIS, strikingly, do it electrogenically with a 21 stoichiometry. Furthermore, G93E/Q NIS discriminate between anion substrates, a discovery with potential clinical relevance. A 3D homology model of NIS based on the structure of the bacterial Na(+)/galactose transporter identifies G93 as a critical player in the mechanism of the transporter: the changes from an outwardly to an inwardly open conformation during the transport cycle use G93 as a pivot. PMID:22011571

  6. Bordetella pertussis major outer membrane porin protein forms small, anion-selective channels in lipid bilayer membranes.

    PubMed Central

    Armstrong, S K; Parr, T R; Parker, C D; Hancock, R E

    1986-01-01

    The major outer membrane protein of molecular weight 40,000 (the 40K protein) of a virulent isolate of Bordetella pertussis was purified to apparent homogeneity. The purified protein formed an oligomer band (of apparent molecular weight 90,000) on sodium dodecyl sulfate-polyacrylamide gels after solubilization at low temperatures. The porin function of this protein was characterized by the black lipid bilayer method. The 40K protein formed channels smaller than all other constitutive major outer membrane porins studied to date. The average single-channel conductance in 1 M KCl was 0.56 nS. This was less than a third of the conductance previously observed for Escherichia coli porins. Zero-current potential measurements made of the porin to determine its ion selectivity revealed the porin to be more than 100-fold selective for anions over cations. The single-channel conductance was measured as a function of salt concentration. The data could be fitted to a Lineweaver-Burk plot suggesting an anion binding site with a Kd of 1.17 M Cl- and a maximum possible conductance through the channel of 1.28 nS. Images PMID:2420780

  7. Textile-based sampling for potentiometric determination of ions.

    PubMed

    Lisak, Grzegorz; Arnebrant, Thomas; Ruzgas, Tautgirdas; Bobacka, Johan

    2015-06-01

    Potentiometric sensing utilizing textile-based micro-volume sampling was applied and evaluated for the determination of clinically (Na(+), K(+), Cl(-)) and environmentally (Cd(2+), Pb(2+) and pH) relevant analytes. In this technological design, calibration solutions and samples were absorbed into textiles while the potentiometric cells (ion-selective electrodes and reference electrode) were pressed against the textile. Once the liquid, by wicking action, reached the place where the potentiometric cell was pressed onto the textile, hence closing the electric circuit, the potentiometric response was obtained. Cotton, polyamide, polyester and their blends with elastane were applied for micro-volume sampling. The textiles were found to influence the determination of pH in environmental samples with pH close to neutral and Pb(2+) at low analyte concentrations. On the other hand, textile-based micro-volume sampling was successfully applied in measurements of Na(+) using solid-contact sodium-selective electrodes utilizing all the investigated textiles for sampling. It was found that in order to extend the application of textile-based sampling toward environmental analysis of ions it will be necessary to tailor the physio-chemical properties of the textile materials. In general, textile-based sampling opens new possibilities for direct chemical analysis of small-volume samples and provide a simple and low-cost method to screen various textiles for their effects on samples to identify which textiles are the most suitable for on-body sensing.

  8. Anion selective membrane. [ion exchange resins and ion exchange membrane electrolytes for electrolytic cells

    NASA Technical Reports Server (NTRS)

    Alexander, S. S.; Geoffroy, R. R.; Hodgdon, R. B.

    1975-01-01

    Experimental anion permselective membranes were prepared and tested for their suitability as cell separators in a chemical redox power storage system being developed at NASA-Lewis Research Center. The goals of long-term (1000 hr) oxidative and thermal stability at 80 C in FeCl3 and CrCl3 electrolytes were met by most of the weak base and strong base amino exchange groups considered in the program. Good stability is exhibited by several of the membrane substrate resins. These are 'styrene' divinylbenzene copolymer and PVC film. At least four membrane systems produce strong flexible films with electrochemical properties (resistivity, cation transfer) superior to those of the 103QZL, the most promising commercial membrane. The physical and chemical properties of the resins are listed.

  9. Selective removal of toxic anionic dyes using a novel nanocomposite derived from cationically modified guar gum and silica nanoparticles.

    PubMed

    Patra, Abhay Shankar; Ghorai, Soumitra; Ghosh, Shankhamala; Mandal, Barun; Pal, Sagar

    2016-01-15

    A novel nanocomposite derived from cationically modified guar gum and in-situ incorporated SiO2 NP (cat-GG/SiO2) has been developed. The cat-GG has been synthesised by grafting poly(2-(diethylamino)ethyl methacrylate) on GG backbone. Various analyses endorse the suitability of cat-GG as well-organized template for the development of homogeneous SiO2 NPs. Dye adsorption studies predict that cat-GG/SiO2 efficiently and selectively adsorb anionic dyes (reactive blue-RB and Congo red-CR) from mixture of dye solutions. This is because of high surface area, multifunctional chelating H-bonding interactions and electrostatic interactions of cationic adsorbent with anionic dyes. Dyes adsorbed on the composite surface are desorbed reversibly using pH 10 stripping solution. Besides, cat-GG/SiO2 has been recycled efficiently with no prominent loss of dye uptake capacity, even after 4 adsorption-desorption cycles.

  10. Selective removal of toxic anionic dyes using a novel nanocomposite derived from cationically modified guar gum and silica nanoparticles.

    PubMed

    Patra, Abhay Shankar; Ghorai, Soumitra; Ghosh, Shankhamala; Mandal, Barun; Pal, Sagar

    2016-01-15

    A novel nanocomposite derived from cationically modified guar gum and in-situ incorporated SiO2 NP (cat-GG/SiO2) has been developed. The cat-GG has been synthesised by grafting poly(2-(diethylamino)ethyl methacrylate) on GG backbone. Various analyses endorse the suitability of cat-GG as well-organized template for the development of homogeneous SiO2 NPs. Dye adsorption studies predict that cat-GG/SiO2 efficiently and selectively adsorb anionic dyes (reactive blue-RB and Congo red-CR) from mixture of dye solutions. This is because of high surface area, multifunctional chelating H-bonding interactions and electrostatic interactions of cationic adsorbent with anionic dyes. Dyes adsorbed on the composite surface are desorbed reversibly using pH 10 stripping solution. Besides, cat-GG/SiO2 has been recycled efficiently with no prominent loss of dye uptake capacity, even after 4 adsorption-desorption cycles. PMID:26348145

  11. 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

  12. Pitavastatin is a more sensitive and selective organic anion-transporting polypeptide 1B clinical probe than rosuvastatin

    PubMed Central

    Prueksaritanont, Thomayant; Chu, Xiaoyan; Evers, Raymond; Klopfer, Stephanie O; Caro, Luzelena; Kothare, Prajakti A; Dempsey, Cynthia; Rasmussen, Scott; Houle, Robert; Chan, Grace; Cai, Xiaoxin; Valesky, Robert; Fraser, Iain P; Stoch, S Aubrey

    2014-01-01

    Aims Rosuvastatin and pitavastatin have been proposed as probe substrates for the organic anion-transporting polypeptide (OATP) 1B, but clinical data on their relative sensitivity and selectivity to OATP1B inhibitors are lacking. A clinical study was therefore conducted to determine their relative suitability as OATP1B probes using single oral (PO) and intravenous (IV) doses of the OATP1B inhibitor rifampicin, accompanied by a comprehensive in vitro assessment of rifampicin inhibitory potential on statin transporters. Methods The clinical study comprised of two separate panels of eight healthy subjects. In each panel, subjects were randomized to receive a single oral dose of rosuvastatin (5 mg) or pitavastatin (1 mg) administered alone, concomitantly with rifampicin (600 mg) PO or IV. The in vitro transporter studies were performed using hepatocytes and recombinant expression systems. Results Rifampicin markedly increased exposures of both statins, with greater differential increases after PO vs. IV rifampicin only for rosuvastatin. The magnitudes of the increases in area under the plasma concentration–time curve were 5.7- and 7.6-fold for pitavastatin and 4.4- and 3.3-fold for rosuvastatin, after PO and IV rifampicin, respectively. In vitro studies showed that rifampicin was an inhibitor of OATP1B1 and OATP1B3, breast cancer resistance protein and multidrug resistance protein 2, but not of organic anion transporter 3. Conclusions The results indicate that pitavastatin is a more sensitive and selective and thus preferred clinical OATP1B probe substrate than rosuvastatin, and that a single IV dose of rifampicin is a more selective OATP1B inhibitor than a PO dose. PMID:24617605

  13. Selection of magnetic anion exchange resins for the removal of dissolved organic and inorganic matters.

    PubMed

    Wang, Qiongjie; Li, Aimin; Wang, Jinnan; Shuang, Chengdong

    2012-01-01

    Four magnetic anion exchange resins (MAERs) were used as adsorbents to purify drinking water. The effect of water quality (pH, temperature, ionic strength, etc.) on the performance of MAER for the removal of dissolved organic matter (DOM) was also investigated. Among the four studied MAERs, the strong base resin named NDMP-1 with high water content and enhanced exchange capacity exhibited the highest removal rate of dissolved organic carbon (DOC) (48.9% removal rate) and UV-absorbing substances (82.4% removal rate) with a resin dose of 10 mL/L after 30 min of contact time. The MAERs could also effectively remove inorganic matter such as sulfate, nitrate and fluoride. Because of the higher specific UV absorbance (SUVA) value, the DOM in the raw water was found to be removed more effectively than that in the clarified water by NDMP resin. The temperature showed a weak influence on the removal of DOC from 6 to 26 degrees C, while a relatively strong one at 36 degrees C. The removal of DOM by NDMP was also affected to some extent by the pH value. Moreover, increasing the sulfate concentration in the raw water could decrease the removal rates of DOC and UV-absorbing substances.

  14. Polymeric Membrane Electrodes with Improved Fluoride Selectivity and Lifetime Based on Zr(IV)- and Al(III)- Tetraphenylporphyrin Derivatives

    PubMed Central

    Pietrzak, Mariusz; Meyerhoff, Mark E.; Malinowska, Elżbieta

    2007-01-01

    Novel aluminum(III)- and zirconium(IV)-tetraphenylporhyrin (TPP) derivatives are examined as fluoride selective ionophores for preparing polymer membrane-based ion-selective electrodes (ISEs). The influence of t-butyl— or dichloro— phenyl ring substituents as well as the nature of the metal ion center (Al(III) vs. Zr(IV)) on the anion complexation constants of TPP derivative ionophores are reported. The anion binding stability constants of the ionophores are characterized by the so-called “sandwich membrane” method. All of the metalloporphyrins examined form their strongest anion complexes with fluoride. The influence of plasticizer as well as the type of lipophilic ionic site additive and their amounts in the sensing membrane are discussed. It is shown that membrane electrodes formulated with the metalloporphyrin derivatives and appropriate anionic or cationic additives exhibit enhanced potentiometric response toward fluoride over all other anions tested. Since selectivity toward fluoride is enhanced in the presence of both anionic and cationic additives, the metalloporphyrins can function as either charged or neutral carriers within the organic membrane phase. In contrast to previously reported fluoride-selective polymeric membrane electrodes based on metalloporphyrins, nernstian or near-nernstian (−51.2 to −60.1 mV decade−1) as well as rapid (t < 80s) and fully reversible potentiometric fluoride responses are observed. Moreover, use of aluminum(III)—t-butyltetraphenylporphyrin as the ionophore provides fluoride sensors with prolonged (7 months) functional life-time. PMID:17631098

  15. Multi-cycle bioregeneration of spent perchlorate-containing macroporous selective anion-exchange resin.

    PubMed

    Sharbatmaleki, Mohamadali; Batista, Jacimaria R

    2012-01-01

    Ion exchange using perchlorate-selective resin is possibly the most feasible technology for perchlorate removal from water. However, in current water treatment applications, selective resins are used once and then incinerated, making the ion-exchange process economically and environmentally unsustainable. A new concept has been developed involving the biological regeneration of resin-containing perchlorate. This concept involves directly contacting perchlorate-containing resins with a perchlorate-reducing microbial culture. In this research, the feasibility of multi-cycle loading and bioregeneration of a macroporous perchlorate-selective resin was investigated. Loading and bioregeneration cycles were performed, using a bench-scale fermenter and a fluidized bed reactor followed by fouling removal and disinfection of the resin. The results revealed that selective macroporous resin can be employed successfully in a consecutive loading-bioregeneration ion-exchange process. Loss of resin capacity stabilized after a few cycles of bioregeneration, indicating that the number of loading and bioregeneration cycles that can be performed is likely greater than the five cycles tested. The results also revealed that most of the capacity loss in the resin is due to perchlorate buildup from previous regeneration cycles. The results further indicated that as the bioregeneration progresses, clogging of the resin pores results in strong mass transfer limitation in the bioregeneration process.

  16. Highly selective and sensitive detection of metal ions and nitroaromatic compounds by an anionic europium(iii) coordination polymer.

    PubMed

    Feyisa Bogale, Raji; Ye, Junwei; Sun, Yuan; Sun, Tongxin; Zhang, Siqi; Rauf, Abdul; Hang, Cheng; Tian, Peng; Ning, Guiling

    2016-07-01

    A luminescent Eu(iii)-based coordination polymer, {[Eu(H2O)5(BTEC)][H(C5H6N2)]·3H2O} () has been synthesized under hydrothermal conditions using 1,2,4,5-benzenetetracarboxylic acid (H4BTEC) as a linker. Compound possesses an anionic zig-zag chain constructed from the BTEC ligands and [EuO4(H2O)5] nodes. The protonated 4-aminopyridine groups as guests are located between chains. exhibits the characteristic sharp emission bands of Eu(3+) at 578, 593, 615, 652 and 693 nm upon excitation at 290 nm. The strong emission of could be quenched effectively by trace amounts of Fe(3+) ions even in the presence of other metal ions including Al(3+), Ca(2+), Cd(2+), Co(2+), Cr(3+), Cu(2+), Fe(2+), K(+), Mg(2+), Mn(2+), Pd(2+) and Zn(2+). Similarly, also exhibits superior selectivity and sensitivity towards 4-nitrophenol (4-NP) compared with other competing interfering analytes, such as 2,4,6-trinitrophenol, 2,6-dinitrotolune, 4-nitrotoluene, nitrobenzene, 1,3-dinitrobenzene, o-xylene, nitromethane, nitropropane, phenol, 4-bromophenol and bromobenzene, through a fluorescence quenching mechanism. The possible fluorescence quenching mechanisms are discussed. Moreover, could be used as a visual fluorescent test paper for selectively detecting trace amounts of Fe(3+) and 4-NP. PMID:27327158

  17. Highly selective and sensitive detection of metal ions and nitroaromatic compounds by an anionic europium(iii) coordination polymer.

    PubMed

    Feyisa Bogale, Raji; Ye, Junwei; Sun, Yuan; Sun, Tongxin; Zhang, Siqi; Rauf, Abdul; Hang, Cheng; Tian, Peng; Ning, Guiling

    2016-07-01

    A luminescent Eu(iii)-based coordination polymer, {[Eu(H2O)5(BTEC)][H(C5H6N2)]·3H2O} () has been synthesized under hydrothermal conditions using 1,2,4,5-benzenetetracarboxylic acid (H4BTEC) as a linker. Compound possesses an anionic zig-zag chain constructed from the BTEC ligands and [EuO4(H2O)5] nodes. The protonated 4-aminopyridine groups as guests are located between chains. exhibits the characteristic sharp emission bands of Eu(3+) at 578, 593, 615, 652 and 693 nm upon excitation at 290 nm. The strong emission of could be quenched effectively by trace amounts of Fe(3+) ions even in the presence of other metal ions including Al(3+), Ca(2+), Cd(2+), Co(2+), Cr(3+), Cu(2+), Fe(2+), K(+), Mg(2+), Mn(2+), Pd(2+) and Zn(2+). Similarly, also exhibits superior selectivity and sensitivity towards 4-nitrophenol (4-NP) compared with other competing interfering analytes, such as 2,4,6-trinitrophenol, 2,6-dinitrotolune, 4-nitrotoluene, nitrobenzene, 1,3-dinitrobenzene, o-xylene, nitromethane, nitropropane, phenol, 4-bromophenol and bromobenzene, through a fluorescence quenching mechanism. The possible fluorescence quenching mechanisms are discussed. Moreover, could be used as a visual fluorescent test paper for selectively detecting trace amounts of Fe(3+) and 4-NP.

  18. Multidentate europium chelates as luminoionophores for anion recognition: impact of ligand design on sensitivity and selectivity, and applicability to enzymatic assays.

    PubMed

    Schäferling, Michael; Aäritalo, Timo; Soukka, Tero

    2014-04-25

    The design of photoluminescent molecular probes for the selective recognition of anions is a major challenge for the development of optical chemical sensors. The reversible binding of anions to lanthanide centers is one promising option for the realization of anion sensors, because it leads in some cases to a strong luminescence increase by the replacement of quenching water molecules. Yet, it is an open problem to gain control of the sensitivity and selectivity of the luminescence response. Primarily, the selective detection of (poly)phosphate species such as nucleotides has emerged as a demanding task, because they are involved in many biological processes and enzymatic reactions. We designed a series of pyridyl-based multidentate europium complexes (seven-, six-, and five-dentate) including sensitizing chromophores and studied their luminescence intensity and lifetime responses to different (poly)phosphates (adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), cyclic adenosine monophosphate (cAMP), pyrophosphate, and phosphate anions), and carboxyanions (citrate, malate, oxalacetate, succinate, α-ketoglutarate, pyruvate, oxalate, carbonate). The results reveal that the number of free coordination sites has a significant impact on the sensitivity and selectivity of the response. Because of its reversibility, the lanthanide probes can be applied to monitor the activity of ATP-consuming enzymes such ATPases and apyrases, which is demonstrated by means of the five-dentate complex.

  19. Solid-state materials for anion sensing in aqueous solution: highly selective colorimetric and luminescence-based detection of perchlorate using a platinum(II) salt.

    PubMed

    Taylor, Stephen D; Howard, Whitney; Kaval, Necati; Hart, Robert; Krause, Jeanette A; Connick, William B

    2010-02-21

    The PF(6)(-) salt of a platinum(II) complex changes from yellow to red and becomes intensely luminescent upon exposure to aqueous ClO(4)(-). The response is remarkably selective. Spectroscopic changes are consistent with anion exchange resulting in shortening of the intramolecular PtPt distances between the square planar cations.

  20. Highly selective CO2 adsorption accompanied with low-energy regeneration in a two-dimensional Cu(II) porous coordination polymer with inorganic fluorinated PF6(-) anions.

    PubMed

    Noro, Shin-ichiro; Hijikata, Yuh; Inukai, Munehiro; Fukushima, Tomohiro; Horike, Satoshi; Higuchi, Masakazu; Kitagawa, Susumu; Akutagawa, Tomoyuki; Nakamura, Takayoshi

    2013-01-01

    High selectivity and low-energy regeneration for adsorption of CO(2) gas were achieved concurrently in a two-dimensional Cu(II) porous coordination polymer, [Cu(PF(6))(2)(4,4'-bpy)(2)](n) (4,4'-bpy = 4,4'-bipyridine), containing inorganic fluorinated PF(6)(-) anions that can act as moderate interaction sites for CO(2) molecules.

  1. Novel potentiometric sensor for monitoring beryllium based on naphto-9-crown-3.

    PubMed

    Ganjali, Mohammad Reza; Daftari, Azadeh; Faal-Rastegar, Majid; Moghimi, Abolghasem

    2003-03-01

    A novel poly(vinyl chloride) (PVC) membrane electrode based on naphto-9-crown-3 was prepared and tested for the selective detection of beryllium ions. A suitable lipophilicity of the carrier and appropriate coordination ability were found to be essential for designing an electrode with good response characteristics. A PVC membrane with 9% naphtho-9-crown-3 carrier, 58% o-NPOE plasticizer, 3% tetraphenylborate anionic excluder and 30% poly(vinyl chloride) satisfied these requirements. The proposed sensor displayed a linear response to beryllium over a wide concentration range of 1.0 x 10(-1)-8.0 x 10(-6) M with a Nernstian slope of 29.5 mV per decade. The electrode showed very short response time (<15 s) and could be used in the pH range 3.5-9.0. The selectivity coefficient for alkali, alkaline earth, transition and heavy metal ions was smaller than 4.0 x 10(-4). The sensor was successfully used as an indicator electrode in the potentiometric titration of Be2+ with EDTA. The proposed Be(II) sensor was also used for the determination of Be2+ ions in binary mixtures.

  2. Development of anion- and nitric oxide-selective chemical sensors and biosensors

    NASA Astrophysics Data System (ADS)

    Barker, Susan Lynn Ritenour

    1999-11-01

    The biological roles of chloride, nitrite, and nitric oxide create the need for techniques which can provide fast, sensitive, and selective detection of these analytes. Small sensor size is advantageous in biological applications, and the coupling of fluorescence transduction with optical fiber technology has allowed the preparation of micrometer and submicromter sized chemical sensors and biosensors with good selectivity, fast response times, and excellent signal to noise ratios, which are utilized for in vitro and cellular applications. Micrometer and submicrometer size fiber optic nitrite and chloride sensors have been prepared, based on immobilized metalloporphyrins, using the ion correlation principle, and characterized with respect to selectivity, sensitivity, and reproducibility. The chloride sensors were applied in vitro to rat conceptuses. The hemoprotein cytochrome c' and the heme domain of soluble guanylate cyclase (sGC) have been labeled with a fluorescent dye and utilized for intensity and fluorescence lifetime-based nitric oxide sensing. Ratiometric fiber optic sensors have been prepared by attaching the dye-labeled cytochrome c' or heme domain of sGC to the fiber along with reference dye spheres. In addition, the fluorescence lifetime of the dye-labeled cytochrome c' in solution has been monitored. A second class of nitric oxide sensors has also been developed. These are dye-based chemical sensors with a response based on the interaction of nitric oxide with a fluorophore adsorbed on a gold surface. Such chemical sensors have the advantage of commercially available components and long-term stability. The nitric oxide bio- and chemical sensors have excellent signal to noise ratios and linear responses down to low micromolar nitric oxide. The various sensors show minimal interference from numerous other chemicals that are commonly found in the cellular environment. In addition, the sensors have low micromolar limits of detection, subsecond response

  3. Anion Receptor Design: Exploiting Outer-Sphere Coordination Chemistry To Obtain High Selectivity for Chloridometalates over Chloride.

    PubMed

    Carson, Innis; MacRuary, Kirstian J; Doidge, Euan D; Ellis, Ross J; Grant, Richard A; Gordon, Ross J; Love, Jason B; Morrison, Carole A; Nichol, Gary S; Tasker, Peter A; Wilson, A Matthew

    2015-09-01

    High anion selectivity for PtCl6(2-) over Cl(-) is shown by a series of amidoamines, R(1)R(2)NCOCH2CH2NR(3)R(4) (L1 with R(1) = R(4) = benzyl and R(2) = R(3) = phenyl and L3 with R(1) = H, R(2) = 2-ethylhexyl, R(3) = phenyl and R(4) = methyl), and amidoethers, R(1)R(2)NCOCH2CH2OR(3) (L5 with R(1) = H, R(2) = 2-ethylhexyl and R(3) = phenyl), which provide receptor sites which extract PtCl6(2-) preferentially over Cl(-) in extractions from 6 M HCl solutions. The amidoether receptor L5 was found to be a much weaker extractant for PtCl6(2-) than its amidoamine analogues. Density functional theory calculations indicate that this is due to the difficulty in protonating the amidoether to generate a cationic receptor, LH(+), rather than the latter showing weaker binding to PtCl6(2-). The most stable forms of the receptors, LH(+), contain a tautomer in which the added proton forms an intramolecular hydrogen bond to the amide oxygen atom to give a six-membered proton chelate. Dispersion-corrected DFT calculations appear to suggest a switch in ligand conformation for the amidoamine ligands to an open tautomer state in the complex, such that the cationic N-H or O-H groups are also readily available to form hydrogen bonds to the PtCl6(2-) ion, in addition to the array of polarized C-H bonds. The predicted difference in energies between the proton chelate and nonchelated tautomer states for L1 is small, however, and the former is found in the X-ray crystal structure of the assembly [(L1H)2PtCl6]. The DFT calculations and the X-ray structure indicate that all LH(+) receptors present an array of polarized C-H groups to the large, charge diffuse PtCl6(2-) anion resulting in high selectivity of extraction of PtCl6(2-) over the large excess of chloride.

  4. Highly selective and sensitive phosphate anion sensors based on AlGaN/GaN high electron mobility transistors functionalized by ion imprinted polymer.

    PubMed

    Jia, Xiuling; Chen, Dunjun; Bin, Liu; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2016-06-09

    A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L(-1) to 2 mg L(-1), the sensitivity and detection limit of the sensor is 3.191 μA/mg L(-1) and 1.97 μg L(-1), respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection.

  5. Highly selective and sensitive phosphate anion sensors based on AlGaN/GaN high electron mobility transistors functionalized by ion imprinted polymer

    NASA Astrophysics Data System (ADS)

    Jia, Xiuling; Chen, Dunjun; Bin, Liu; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2016-06-01

    A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L-1 to 2 mg L-1, the sensitivity and detection limit of the sensor is 3.191 μA/mg L-1 and 1.97 μg L-1, respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection.

  6. Highly selective and sensitive phosphate anion sensors based on AlGaN/GaN high electron mobility transistors functionalized by ion imprinted polymer.

    PubMed

    Jia, Xiuling; Chen, Dunjun; Bin, Liu; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2016-01-01

    A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L(-1) to 2 mg L(-1), the sensitivity and detection limit of the sensor is 3.191 μA/mg L(-1) and 1.97 μg L(-1), respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection. PMID:27278795

  7. Highly selective and sensitive phosphate anion sensors based on AlGaN/GaN high electron mobility transistors functionalized by ion imprinted polymer

    PubMed Central

    Jia, Xiuling; Chen, Dunjun; Bin, Liu; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2016-01-01

    A novel ion-imprinted electrochemical sensor based on AlGaN/GaN high electron mobility transistors (HEMTs) was developed to detect trace amounts of phosphate anion. This sensor combined the advantages of the ion sensitivity of AlGaN/GaN HEMTs and specific recognition of ion imprinted polymers. The current response showed that the fabricated sensor is highly sensitive and selective to phosphate anions. The current change exhibited approximate linear dependence for phosphate concentration from 0.02 mg L−1 to 2 mg L−1, the sensitivity and detection limit of the sensor is 3.191 μA/mg L−1 and 1.97 μg L−1, respectively. The results indicated that this AlGaN/GaN HEMT-based electrochemical sensor has the potential applications on phosphate anion detection. PMID:27278795

  8. The influence of anionic ligands on stereoisomerism of Ru carbenes and their importance to efficiency and selectivity of catalytic olefin metathesis reactions.

    PubMed

    Torker, Sebastian; Khan, R Kashif M; Hoveyda, Amir H

    2014-03-01

    Investigations detailed herein provide insight regarding the mechanism of stereochemical inversion of stereogenic-at-Ru carbene complexes through a nonolefin metathesis-based polytopal rearrangement pathway. Computational analyses (DFT) reveal that there are two key factors that generate sufficient energy barriers that are responsible for the possibility of isolation and characterization of high-energy, but kinetically stable, intermediates: (1) donor-donor interactions that involve the anionic ligands and the strongly electron donating carbene groups and (2) dipolar effects arising from the syn relationship between the anionic groups (iodide and phenoxide). We demonstrate that a Brønsted acid lowers barriers to facilitate isomerization, and that the positive influence of a proton source is the result of its ability to diminish the repulsive electronic interactions originating from the anionic ligands. The implications of the present studies regarding a more sophisticated knowledge of the role of anionic units on the efficiency of Ru-catalyzed olefin metathesis reactions are discussed. The electronic basis for the increased facility with which allylic alcohols participate in olefin metathesis processes will be presented as well. Finally, we illustrate how a better understanding of the role of anionic ligands has served as the basis for successful design of Ru-based Z-selective catalysts for alkene metathesis. PMID:24533571

  9. The influence of anionic ligands on stereoisomerism of Ru carbenes and their importance to efficiency and selectivity of catalytic olefin metathesis reactions.

    PubMed

    Torker, Sebastian; Khan, R Kashif M; Hoveyda, Amir H

    2014-03-01

    Investigations detailed herein provide insight regarding the mechanism of stereochemical inversion of stereogenic-at-Ru carbene complexes through a nonolefin metathesis-based polytopal rearrangement pathway. Computational analyses (DFT) reveal that there are two key factors that generate sufficient energy barriers that are responsible for the possibility of isolation and characterization of high-energy, but kinetically stable, intermediates: (1) donor-donor interactions that involve the anionic ligands and the strongly electron donating carbene groups and (2) dipolar effects arising from the syn relationship between the anionic groups (iodide and phenoxide). We demonstrate that a Brønsted acid lowers barriers to facilitate isomerization, and that the positive influence of a proton source is the result of its ability to diminish the repulsive electronic interactions originating from the anionic ligands. The implications of the present studies regarding a more sophisticated knowledge of the role of anionic units on the efficiency of Ru-catalyzed olefin metathesis reactions are discussed. The electronic basis for the increased facility with which allylic alcohols participate in olefin metathesis processes will be presented as well. Finally, we illustrate how a better understanding of the role of anionic ligands has served as the basis for successful design of Ru-based Z-selective catalysts for alkene metathesis.

  10. Fabrication of a potentiometric/amperometric bifunctional enzyme microbiosensor.

    PubMed

    Reddy, K Ravi Charan; Turcu, Florin; Schulte, Albert; Kayastha, Arvind M; Schuhmann, Wolfgang

    2005-08-01

    We report the fabrication and functional characterization of a needle-type bifunctional enzyme microbiosensor that has, as technical novelty, simultaneously integrated a potentiometric and amperometric detection of an enzyme-catalyzed reaction at the tip of a pulled glass micropipet. The construction involved immobilizing an enzyme onto the platinized outer tip surface using the precipitation of electrodeposition paint with direct entrapment of the biocomponent in the slowly growing polymer film. Products of enzyme-substrate reaction could then be targeted in a dual-detection mode on one hand with the covered Pt layer at the tip region as amperometric detector and on the other hand with a proton-selective liquid membrane-based potentiometric sensor inside the open pipet tip. Completing and testing bifunctional glucose microsensors demonstrated the functionality of the proposed strategy. Synchronized amperometric and potentiometric detection of the addition of a glucose standard to a buffer solution became evident by observing stepwise increases in the amperometric H2O2 oxidation current and corresponding increases in the potential of the pH-selective sensor, which translates to a local pH decrease around the tip due to hydrolysis of enzymatically formed gluconic acid. PMID:16053323

  11. Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O2 battery capacity.

    PubMed

    Burke, Colin M; Pande, Vikram; Khetan, Abhishek; Viswanathan, Venkatasubramanian; McCloskey, Bryan D

    2015-07-28

    Among the "beyond Li-ion" battery chemistries, nonaqueous Li-O2 batteries have the highest theoretical specific energy and, as a result, have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O2 batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than fourfold) in Li-O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using (7)Li NMR and modeling, we confirm that this improvement is a result of enhanced Li(+) stability in solution, which, in turn, induces solubility of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g., Li-S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation. PMID:26170330

  12. Mitigating arsenic crisis in the developing world: role of robust, reusable and selective hybrid anion exchanger (HAIX).

    PubMed

    German, Michael; Seingheng, Hul; SenGupta, Arup K

    2014-08-01

    In trying to address the public health crisis from the lack of potable water, millions of tube wells have been installed across the world. From these tube wells, natural groundwater contamination from arsenic regularly puts at risk the health of over 100 million people in South and Southeast Asia. Although there have been many research projects, awards and publications, appropriate treatment technology has not been matched to ground level realities and water solutions have not scaled to reach millions of people. For thousands of people from Nepal to India to Cambodia, hybrid anion exchange (HAIX) resins have provided arsenic-safe water for up to nine years. Synthesis of HAIX resins has been commercialized and they are now available globally. Robust, reusable and arsenic-selective, HAIX has been in operation in rural communities over numerous cycles of exhaustion-regeneration. All necessary testing and system maintenance is organized by community-level water staff. Removed arsenic is safely stored in a scientifically and environmentally appropriate manner to prevent future hazards to animals or people. Recent installations have shown the profitability of HAIX-based arsenic treatment, with capital payback periods of only two years in ideal locations. With an appropriate implementation model, HAIX-based treatment can rapidly scale and provide arsenic-safe water to at-risk populations.

  13. Mechanistic Investigation of Solvent Extraction Based on Anion-Functionalized Ionic Liquids for Selective Separation of Rare-Earth Ions

    SciTech Connect

    Sun, Xiaoqi; Luo, Huimin; Dai, Sheng

    2013-01-01

    In this study, solvation has been found to be a dominant mechanism in a comprehensive ionic liquid based extraction system for rare earth elements (REEs). Trioctylmethylammonium di(2-ethylhexyl)phosphate ([TOMA][DEHP]), an ionic-liquid extractant, was used in 1-alkyl-3-methylimidizolium bis[(trifluoromethyl)sulfonyl]imide ([Cnmim][NTf2], n = 4, 6, 8, 10) and 1-alkyl-3-methylimidizolium bis(perfluoroethanesulfonyl)imide ([Cnmim][BETI], n = 4, 6, 8, 10) for the separation of REEs. Surprisingly, a very similar extraction behavior was observed even as the carbon chain length on the ionic-liquid (IL) cation increased from butyl (C4) to hexyl (C6), to octyl (C8), to decyl (C10). This behavior is in sharp contrast to that exhibited by the conventional neutral extractants, whose extraction efficiencies are strongly dependent on the hydrophobicity of IL cations. Furthermore, the addition of IL cations ([Cnmim]+) or IL anions ([NTf2]- or [BETI]-) to the aqueous phase had little effect on the extraction behavior of the above extraction system, ruling out the strong involvement of the ion-exchange mechanism associated with traditional IL-based extraction systems. Results showed that the extractabilities and selectivities of REEs using [TOMA][DEHP] in [C10mim][NTf2]/[BETI] are several orders of magnitude better than those achieved using conventional organic solvent, diisopropylbenzene (DIPB). This study highlights the potential of developing a comprehensive IL-based extraction strategy for REEs separations.

  14. Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li–O2 battery capacity

    PubMed Central

    Burke, Colin M.; Pande, Vikram; Khetan, Abhishek; Viswanathan, Venkatasubramanian; McCloskey, Bryan D.

    2015-01-01

    Among the “beyond Li-ion” battery chemistries, nonaqueous Li–O2 batteries have the highest theoretical specific energy and, as a result, have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li–O2 batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than fourfold) in Li–O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using 7Li NMR and modeling, we confirm that this improvement is a result of enhanced Li+ stability in solution, which, in turn, induces solubility of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g., Li–S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation. PMID:26170330

  15. Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O2 battery capacity.

    PubMed

    Burke, Colin M; Pande, Vikram; Khetan, Abhishek; Viswanathan, Venkatasubramanian; McCloskey, Bryan D

    2015-07-28

    Among the "beyond Li-ion" battery chemistries, nonaqueous Li-O2 batteries have the highest theoretical specific energy and, as a result, have attracted significant research attention over the past decade. A critical scientific challenge facing nonaqueous Li-O2 batteries is the electronically insulating nature of the primary discharge product, lithium peroxide, which passivates the battery cathode as it is formed, leading to low ultimate cell capacities. Recently, strategies to enhance solubility to circumvent this issue have been reported, but rely upon electrolyte formulations that further decrease the overall electrochemical stability of the system, thereby deleteriously affecting battery rechargeability. In this study, we report that a significant enhancement (greater than fourfold) in Li-O2 cell capacity is possible by appropriately selecting the salt anion in the electrolyte solution. Using (7)Li NMR and modeling, we confirm that this improvement is a result of enhanced Li(+) stability in solution, which, in turn, induces solubility of the intermediate to Li2O2 formation. Using this strategy, the challenging task of identifying an electrolyte solvent that possesses the anticorrelated properties of high intermediate solubility and solvent stability is alleviated, potentially providing a pathway to develop an electrolyte that affords both high capacity and rechargeability. We believe the model and strategy presented here will be generally useful to enhance Coulombic efficiency in many electrochemical systems (e.g., Li-S batteries) where improving intermediate stability in solution could induce desired mechanisms of product formation.

  16. Mitigating arsenic crisis in the developing world: role of robust, reusable and selective hybrid anion exchanger (HAIX).

    PubMed

    German, Michael; Seingheng, Hul; SenGupta, Arup K

    2014-08-01

    In trying to address the public health crisis from the lack of potable water, millions of tube wells have been installed across the world. From these tube wells, natural groundwater contamination from arsenic regularly puts at risk the health of over 100 million people in South and Southeast Asia. Although there have been many research projects, awards and publications, appropriate treatment technology has not been matched to ground level realities and water solutions have not scaled to reach millions of people. For thousands of people from Nepal to India to Cambodia, hybrid anion exchange (HAIX) resins have provided arsenic-safe water for up to nine years. Synthesis of HAIX resins has been commercialized and they are now available globally. Robust, reusable and arsenic-selective, HAIX has been in operation in rural communities over numerous cycles of exhaustion-regeneration. All necessary testing and system maintenance is organized by community-level water staff. Removed arsenic is safely stored in a scientifically and environmentally appropriate manner to prevent future hazards to animals or people. Recent installations have shown the profitability of HAIX-based arsenic treatment, with capital payback periods of only two years in ideal locations. With an appropriate implementation model, HAIX-based treatment can rapidly scale and provide arsenic-safe water to at-risk populations. PMID:24321388

  17. Self-assembled arene-ruthenium-based rectangles for the selective sensing of multi-carboxylate anions.

    PubMed

    Vajpayee, Vaishali; Song, Young Ho; Lee, Min Hyung; Kim, Hyunuk; Wang, Ming; Stang, Peter J; Chi, Ki-Whan

    2011-07-01

    Novel arene-ruthenium [2+2] metalla-rectangles 4 and 5 have been synthesized by self-assembly using dipyridyl amide ligand 3 and arene-ruthenium acceptors (arene: benzoquinone (1), naphthacenedione (2)) and characterized by NMR spectroscopy and ESI-MS. The solid-state structure of 5 was determined by X-ray diffraction and shows encapsulated diethyl ether molecule in the rectangular cavity of 5. The luminescent 5 was further used for anion sensing with the amidic linkage serving as a hydrogen-bond donor site for anions and the ruthenium moiety serving as a signaling unit. A UV/Vis titration study demonstrated that although 5 interacts very weakly with common monoanions as well as with flexible dicarboxylate anions such as malonate and succinate, it displays significant binding affinity (K>10(3) in MeOH) for rigid multi-carboxylate anions such as oxalate, citrate, and tartrate, exhibiting a 1:1 stoichiometry. It has been suggested that 1:1 bidentate hydrogen bonding assisted by appropriate geometrical complementarity is mainly responsible for the increased affinity of 5 towards such anions. A fluorescence titration study revealed a large fluorescence enhancement of 5 upon binding to multi-carboxylate anions, which can be attributed to the blocking of the photoinduced electron-transfer process from the arene-Ru moiety to the amidic donor in 5 as a result of hydrogen bonding between the donor and the anion.

  18. Substituent directed selectivity in anion recognition by a new class of simple osmium-pyrazole derived receptors.

    PubMed

    Das, Ankita; Mondal, Prasenjit; Dasgupta, Moumita; Kishore, Nand; Lahiri, Goutam Kumar

    2016-02-14

    The present article deals with the structurally, spectroscopically and electrochemically characterised osmium-bipyridyl derived complexes [(bpy)2Os(II)(HL1)Cl]ClO4 [1]ClO4 and [(bpy)2Os(II)(HL2)Cl]ClO4 [2]ClO4 incorporating neutral and monodentate pyrazole derivatives (HL) with one free NH function (bpy = 2,2'-bipyridine, HL1 = pyrazole, HL2 = 3,5-dimethylpyrazole). The crystal structures of [1]ClO4 and [2]ClO4 reveal intramolecular hydrogen bonding interactions between the free NH proton of HL and the equatorially placed Cl(-) ligand (N-HCl) with donor-acceptor distances of 3.114(7) Å and 3.153(6) Å as well as intermolecular hydrogen bonding interactions between the NH proton and one of the oxygen atoms of ClO4(-) (N-HO) with donor-acceptor distances of 2.870(10) Å and 3.024(8) Å, respectively. The effect of hydrogen bonding interactions has translated into the less acidic nature of the NH proton of the coordinated HL with estimated pKa > 12. 1(+) and 2(+) exhibit reversible Os(II)/(III) and irreversible Os(III)/(IV) processes in CH3CN within ± 2.0 V versus SCE. The effect of 3,5-dimethyl substituted HL2 on 2(+) has been reflected in the appreciable lowering (40 mV) of the Os(II/III) potential, along with the further decrease in the acidity of the NH proton (pKa > 13.0) with regard to HL1 coordinated 1(+) (pKa: ∼ 12.3). The electronic spectral features of Os(ii) (1(+)/2(+)) and electrochemically generated Os(III) (1(2+)/2(2+)) derived complexes have been analysed by TD-DFT calculations. The efficacy of the 1(+) and 2(+) encompassing free NH proton towards the anion recognition process has been evaluated by different experimental investigations using a wide variety of anions. It however establishes that receptor 1(+) can recognise both F(-) and OAc(-) in acetonitrile solution, while 2(+) is exclusively selective for the F(-) ion. PMID:26733437

  19. 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.

  20. OccK Channels from Pseudomonas aeruginosa Exhibit Diverse Single-channel Electrical Signatures, but Conserved Anion Selectivity

    PubMed Central

    Liu, Jiaming; Eren, Elif; Vijayaraghavan, Jagamya; Cheneke, Belete R.; Indic, Mridhu; van den Berg, Bert; Movileanu, Liviu

    2012-01-01

    Pseudomonas aeruginosa is a Gram-negative bacterium that utilizes substrate-specific outer membrane (OM) proteins for the uptake of small, water-soluble nutrients employed in the growth and function of the cell. In this paper, we present for the first time a comprehensive single-channel examination of seven members of the OM carboxylate channel K (OccK) subfamily. Recent biochemical, functional and structural characterization of the OccK proteins revealed their common features, such as a closely related, monomeric, 18-stranded β-barrel conformation with a kidney-shaped transmembrane pore and the presence of a basic ladder within the channel lumen. Here, we report that the OccK proteins exhibited fairly distinct unitary conductance values, in a much broader range than earlier expectations, which includes low (~40–100 pS) and medium (~100–380 pS) conductance. These proteins showed diverse single-channel dynamics of current gating transitions, revealing one (OccK3)-, two (OccK4, OccK5 and OccK6)- and three (OccK1, OccK2 and OccK7)-open sub-state kinetics with functionally distinct conformations. Interestingly, we discovered that anion selectivity is a conserved trait among the members of the OccK subfamily, confirming the presence of a net pool of positively charged residues within their central constriction. Moreover, these results are in accord with an increased specificity and selectivity of these protein channels for negatively charged, carboxylate-containing substrates. Our findings might ignite future functional examinations and full-atomistic computational studies for unraveling a mechanistic understanding of the passage of small molecules across the lumen of substrate-specific, β-barrel OM proteins. PMID:22369314

  1. Development of novel potentiometric sensors for determination of tartrazine dye concentration in foodstuff products.

    PubMed

    Abu Shawish, Hazem M; Ghalwa, Nasser Abu; Saadeh, Salman M; El Harazeen, Heba

    2013-05-01

    Tartrazine dye Na(3)TZ in foodstuff products was determined by a new modified carbon paste electrode, encoded sensor A, and a coated silver wire electrode, encoded sensor B, based on tartrazine TZ- cetryltrimethyl ammoniumbromide CTAB as a chemical modifier TZ-CTA. The electrodes exhibit the following characteristics listed respectively: a Nernstian slope of 17.9±0.5 and 19.4±0.2 mV/decade for tartrazine ion over a wide concentration range from 4.3×10(-7) to 1.0×10(-2) and 1.1×10(-7) to 1.0×10(-2) M. The lower detection limits: 3.2×10(-7) and 5.5×10(-8) M. Short response time (5-8 s) over the pH range 3.8-7.7 and 4.2-8.1. The proposed sensors display significantly high selectivity for TZ ion over a wide variety of sugars, some anions, common organic, inorganic compounds and additives. The developed electrodes were applied to the potentiometric determination of tartrazine ion in different kinds of foodstuffs: solid jelly (strawberry and custard) powder samples and soft drink (orange) samples with satisfactory results.

  2. Protein-salt binding data from potentiometric titrations of lysozyme in aqueous solutions containing KCl

    SciTech Connect

    Engmann, J.; Blanch, H.W.; Prausnitz, J.M. |

    1997-03-01

    An existing method for potentiometric titrations of proteins was improved, tested and applied to titrations of the enzyme hen-egg-white lysozyme in aqueous solutions containing KCl at ionic strengths from 0.1 M to 2.0 M at 25 C. Information about the protein`s net charge dependence on pH and ionic strength were obtained and salt binding numbers for the system were calculated using a linkage concept. For the pH range 2.5--11.5, the net charge slightly but distinctly increases with increasing ionic strength between 0.1 M and 2.0 M. The differences are most distinct in the pH region below 5. Above pH 11.35, the net charge decreases with increasing ionic strength. Preliminary calculation of binding numbers from titration curves at 0.1 M and 1.0 M showed selective association of chloride anions and expulsion of potassium ions at low pH. Ion-binding numbers from this work will be used to evaluate thermodynamic properties and to correlate crystallization or precipitation phase-equilibrium data in terms of a model based on the integral-equation theory of fluids which is currently under development.

  3. Tandem electrochemical desalination-potentiometric nitrate sensing for seawater analysis.

    PubMed

    Cuartero, Maria; Crespo, Gastón A; Bakker, Eric

    2015-08-18

    We report on a methodology for the direct potentiometric determination of nitrate in seawater by in-line coupling to an electrochemical desalination module. A microfluidic custom-fabricated thin layer flat cell allows one to electrochemically reduce the chloride concentration of seawater more than 100-fold, from 600 mM down to ∼2.8 mM. The desalinator operates by the exhaustive electrochemical plating of the halides from the thin layer sample onto a silver element as silver chloride, which is coupled to the transfer of the counter cations across a permselective ion-exchange membrane to an outer solution. As a consequence of suppressing the major interference of an ion-exchanger based membrane, the 80 μL desalinated sample plug is passed to a potentiometric flow cell of 13 μL volume. The potentiometric sensor is composed of an all-solid-state nitrate selective electrode based on lipophilic carbon nanotubes (f-MWCNTs) as an ion-to-electron transducer (slope of -58.9 mV dec(-1), limit of detection of 5 × 10(-7) M, and response time of 5 s in batch mode) and a miniaturized reference electrode. Nitrate is successfully determined in desalinated seawater using ion chromatography as the reference method. It is anticipated that this concept may form an attractive platform for in situ environmental analysis of a variety of ions that normally suffer from interference by the high saline level of seawater. PMID:26201537

  4. Tandem electrochemical desalination-potentiometric nitrate sensing for seawater analysis.

    PubMed

    Cuartero, Maria; Crespo, Gastón A; Bakker, Eric

    2015-08-18

    We report on a methodology for the direct potentiometric determination of nitrate in seawater by in-line coupling to an electrochemical desalination module. A microfluidic custom-fabricated thin layer flat cell allows one to electrochemically reduce the chloride concentration of seawater more than 100-fold, from 600 mM down to ∼2.8 mM. The desalinator operates by the exhaustive electrochemical plating of the halides from the thin layer sample onto a silver element as silver chloride, which is coupled to the transfer of the counter cations across a permselective ion-exchange membrane to an outer solution. As a consequence of suppressing the major interference of an ion-exchanger based membrane, the 80 μL desalinated sample plug is passed to a potentiometric flow cell of 13 μL volume. The potentiometric sensor is composed of an all-solid-state nitrate selective electrode based on lipophilic carbon nanotubes (f-MWCNTs) as an ion-to-electron transducer (slope of -58.9 mV dec(-1), limit of detection of 5 × 10(-7) M, and response time of 5 s in batch mode) and a miniaturized reference electrode. Nitrate is successfully determined in desalinated seawater using ion chromatography as the reference method. It is anticipated that this concept may form an attractive platform for in situ environmental analysis of a variety of ions that normally suffer from interference by the high saline level of seawater.

  5. Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a Benzothiazole-Attached Macrocycle That Correlate with Structural Coordination Modes.

    PubMed

    Ju, Huiyeong; Chang, Duk Jin; Kim, Seulgi; Ryu, Hyunsoo; Lee, Eunji; Park, In-Hyeok; Jung, Jong Hwa; Ikeda, Mari; Habata, Yoichi; Lee, Shim Sung

    2016-08-01

    We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO2S2-macrocycle L was synthesized, and its mercury(II) selectivity (for perchlorate salt) as a dual-probe channel (UV-vis and fluorescence) chemosensor exhibiting the largest blue shift and the fluorescence turn-off was observed. In the mercury(II) sensing with different anions, except ClO4(-) and NO3(-), no responses for mercury(II) were observed with other anions such as Cl(-), Br(-), I(-), SCN(-), OAc(-), and SO4(2-). A crystallographic approach for the mononuclear mercury(II) perchlorate complex [Hg(L)(ClO4)2]·0.67CH2Cl2 (1) and polymeric mercury(II) iodide complex [Hg(L)I2]n (2) revealed that the observed anion-controlled mercury(II) sensing in the fluorescence mainly stems from the endo- and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg-Ntert bond formation or not. The detailed complexation process with mercury(II) perchlorate associated with the cation sensing was also monitored with the titration methods by UV-vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry.

  6. Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a Benzothiazole-Attached Macrocycle That Correlate with Structural Coordination Modes.

    PubMed

    Ju, Huiyeong; Chang, Duk Jin; Kim, Seulgi; Ryu, Hyunsoo; Lee, Eunji; Park, In-Hyeok; Jung, Jong Hwa; Ikeda, Mari; Habata, Yoichi; Lee, Shim Sung

    2016-08-01

    We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO2S2-macrocycle L was synthesized, and its mercury(II) selectivity (for perchlorate salt) as a dual-probe channel (UV-vis and fluorescence) chemosensor exhibiting the largest blue shift and the fluorescence turn-off was observed. In the mercury(II) sensing with different anions, except ClO4(-) and NO3(-), no responses for mercury(II) were observed with other anions such as Cl(-), Br(-), I(-), SCN(-), OAc(-), and SO4(2-). A crystallographic approach for the mononuclear mercury(II) perchlorate complex [Hg(L)(ClO4)2]·0.67CH2Cl2 (1) and polymeric mercury(II) iodide complex [Hg(L)I2]n (2) revealed that the observed anion-controlled mercury(II) sensing in the fluorescence mainly stems from the endo- and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg-Ntert bond formation or not. The detailed complexation process with mercury(II) perchlorate associated with the cation sensing was also monitored with the titration methods by UV-vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry. PMID:27391394

  7. Coordination-induced gelation of an L-glutamic acid Schiff base derivative: the anion effect and cyanide-specific selectivity.

    PubMed

    Sun, Jinguo; Liu, Yucun; Jin, Longyi; Chen, Tie; Yin, Bingzhu

    2016-01-14

    By rational assembly of Zn(2+) and Cu(2+) with G, three metallogels (ZnG, CuG and Zn-CuG) were prepared. The gelation was controlled by the presence of specific anions, with their efficacy linked to the Hofmeister series. Zn-CuG could fluorescently detect CN(-) with specific selectivity over S(2-) and Cys through the competitive coordination of CN(-) and G with Cu(2+).

  8. Anion-π Enzymes

    PubMed Central

    2016-01-01

    In this report, we introduce artificial enzymes that operate with anion-π interactions, an interaction that is essentially new to nature. The possibility to stabilize anionic intermediates and transition states on an π-acidic surface has been recently demonstrated, using the addition of malonate half thioesters to enolate acceptors as a biologically relevant example. The best chiral anion-π catalysts operate with an addition/decarboxylation ratio of 4:1, but without any stereoselectivity. To catalyze this important but intrinsically disfavored reaction stereoselectively, a series of anion-π catalysts was equipped with biotin and screened against a collection of streptavidin mutants. With the best hit, the S112Y mutant, the reaction occurred with 95% ee and complete suppression of the intrinsically favored side product from decarboxylation. This performance of anion-π enzymes rivals, if not exceeds, that of the best conventional organocatalysts. Inhibition of the S112Y mutant by nitrate but not by bulky anions supports that contributions from anion-π interactions exist and matter, also within proteins. In agreement with docking results, K121 is shown to be essential, presumably to lower the pKa of the tertiary amine catalyst to operate at the optimum pH around 3, that is below the pKa of the substrate. Most importantly, increasing enantioselectivity with different mutants always coincides with increasing rates and conversion, i.e., selective transition-state stabilization. PMID:27413782

  9. Anion-π Enzymes.

    PubMed

    Cotelle, Yoann; Lebrun, Vincent; Sakai, Naomi; Ward, Thomas R; Matile, Stefan

    2016-06-22

    In this report, we introduce artificial enzymes that operate with anion-π interactions, an interaction that is essentially new to nature. The possibility to stabilize anionic intermediates and transition states on an π-acidic surface has been recently demonstrated, using the addition of malonate half thioesters to enolate acceptors as a biologically relevant example. The best chiral anion-π catalysts operate with an addition/decarboxylation ratio of 4:1, but without any stereoselectivity. To catalyze this important but intrinsically disfavored reaction stereoselectively, a series of anion-π catalysts was equipped with biotin and screened against a collection of streptavidin mutants. With the best hit, the S112Y mutant, the reaction occurred with 95% ee and complete suppression of the intrinsically favored side product from decarboxylation. This performance of anion-π enzymes rivals, if not exceeds, that of the best conventional organocatalysts. Inhibition of the S112Y mutant by nitrate but not by bulky anions supports that contributions from anion-π interactions exist and matter, also within proteins. In agreement with docking results, K121 is shown to be essential, presumably to lower the pK a of the tertiary amine catalyst to operate at the optimum pH around 3, that is below the pK a of the substrate. Most importantly, increasing enantioselectivity with different mutants always coincides with increasing rates and conversion, i.e., selective transition-state stabilization. PMID:27413782

  10. Aggregation-Induced Emission Active Metal-Free Chemosensing Platform for Highly Selective Turn-On Sensing and Bioimaging of Pyrophosphate Anion.

    PubMed

    Gogoi, Abhijit; Mukherjee, Sandipan; Ramesh, Aiyagari; Das, Gopal

    2015-07-01

    We report the synthesis of a metal-free chemosensor for highly selective sensing of pyrophosphate (PPi) anion in physiological medium. The novel phenylbenzimidazole functionalized imine containing chemosensor (L; [2,6-bis(((4-(1H-benzo[d]imidazol-2-yl)phenyl)imino) methyl)-4 methyl phenol]) could sense PPi anion through "turn-on" colorimetric and fluorimetric responses in a very competitive environment. The overall sensing mechanism is based on the aggregation-induced emission (AIE) phenomenon. Moreover, a real time in-field device application was demonstrated by sensing PPi in paper strips coated with L. Interestingly, detection of intracellular PPi ions in model human cells could also be possible by fluorescence microscopic studies without any toxicity to these cells. PMID:26059015

  11. A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

    PubMed

    Wang, Shaodan; Fei, Xiaoliang; Guo, Jing; Yang, Qingbiao; Li, Yaoxian; Song, Yan

    2016-01-01

    A hybrid carbazole-hemicyanine dye (Cac) has been developed as a novel colorimetric and ratiometric fluorescent sensor for cyanide detection. Upon treatment with cyanide, Cac displayed a remarkable fluorescence ratiometric response, with the emission wavelength displaying a very large emission shift (214 nm). The detection of cyanide was performed via the nucleophilic addition of cyanide anion to the indolium group of the sensor, which resulted in the blocking of the intramolecular charge transfer (ICT) process in the sensor, inducing a ratiometric fluorescence change and simultaneously an obvious color change. Furthermore, competitive anions did not showed any significant changes both in color and emission intensity ratio (I381/I595), indicating the high selectivity of the sensor to CN(-).

  12. Construction of a potentiometric glutamate biosensor for determination of glutamate in some real samples.

    PubMed

    Y Lmaz, Demet; Karaku, Emine

    2011-12-01

    The potentiometric glutamate biosensor based on ammonium-selective poly(vinylchloride) (PVC) membrane electrode was constructed by chemically immobilizing glutamate oxidase. Ammonium ions produced after an enzymatic reaction were determined potentiometrically. We determined the optimum working conditions of the biosensor such as buffer concentration, buffer pH, lifetime, response time, linear working range, kinetic constants (K(m) and V(max)) of glutamate oxidase enzyme used for biosensor construction values, and other response characteristics. Additionally, glutamate assay in some real samples such as chicken bullion, healthy human serum, and commercial multipower amino acid mixture were also successfully carried out. The results showed good agreement with previously reported values.

  13. Potentiometric Electronic Tongues for Foodstuff and Biosample Recognition—An Overview

    PubMed Central

    Ciosek, Patrycja; Wróblewski, Wojciech

    2011-01-01

    Potentiometric sensors are attractive tools for the fabrication of various electronic tongues that can be used in wide area of applications, ranging from foodstuff recognition to environmental monitoring and medical diagnostics. Their main advantages are the ability to modify their selectivity (including cross-sensitivity effects) and the possibility of miniaturization using appropriate construction methods for the transducer part (e.g., with the use of solid-state technology). In this overview various examples of the design, performance, and applications of potentiometric electronic tongues are presented. The results summarize recent research in the field conducted in the Department of Microbioanalytics, Warsaw University of Technology (WUT). PMID:22163870

  14. Potentiometric measurement of glucose concentration with an immobilized glucose oxidase/catalase electrode.

    PubMed

    Wingard, L B; Liu, C C; Wolfson, S K; Yao, S J; Drash, A L

    1982-01-01

    A series of enzyme electrodes for measurement of glucose have been constructed. The electrodes contain glucose oxidase immobilized on platinum, either with or without co-immobilization of catalase. When placed in buffered glucose, the enzyme electrodes show a potentiometric response to glucose with respect to a Ag/AgCl reference electrode. This response is reproducible in the physiologic range of glucose concentrations. The immobilization technique, some of the environmental variables such as oxygen concentration and pH, and several compounds that might interfere with the selectivity of the enzyme electrodes for glucose have received preliminary study. This direct potentiometric approach is undergoing further evaluation to determine the basic electrochemical mechanism responsible for the potentiometric signal and whether it can be adapted for continuous in vivo monitoring of the glucose concentration in body fluids. PMID:7172983

  15. Selective colorimetric determination of TNT partitioned between an alkaline solution and a strongly basic Dowex 1-X8 anion exchanger.

    PubMed

    Uzer, Ayşem; Erçağ, Erol; Apak, Reşat

    2008-01-30

    The Meisenheimer anions formed from TNT in KOH solutions in alcohol or acetone were used in screening tests for TNT among possible nitro-explosives. The same reaction was used for the spectrophotometric assay of TNT in soil by CRREL (Cold Regions Research & Engineering Laboratory of the U.S. Army) method, also known as Jenkins' method, but the color stability was too dependent on the solution composition and the water tolerance was low, necessitating complete drying of soil samples (which may cause partial analyte decomposition) prior to analysis. This study reports the development of a colorimetric method based on the solid phase extraction (SPE) of the Meisenheimer anion formed from TNT and aqueous NaOH into a strongly basic anion exchange resin Dowex 1-X8 (OH(-) form). The orange-red color that developed both in the solid resin and solution phases was persistent for at least 1h. The resin was let to swell in alcohol, washed first with 1M aqueous NaOH, and then with H(2)O before use. To 5 mL of 4-400 ppm TNT solutions in 1:1 (v/v) acetone-water, 0.5 mL of 5% NaOH was added, diluted to 50 mL with 1:1 acetone-water, and the resulting solutions (containing the orange-red Meisenheimer anion of TNT) were agitated at room temperature with 0.9 g resin for < or =50 min. TNT exhibited a reasonably constant distribution coefficient between the resin and aqueous phases. The absorbance of the filtered solutions was measured against a reagent blank at 500nm. The TNT-loaded resins were regenerated with 1M HCl containing sodium sulfite. The calibration line of filtrate absorbance versus analytical concentration was linear over two orders of magnitude between 0.4 and 40 ppm TNT in final solution. Unlike Jenkins' method, the method was tolerant to 100-fold (by mass) of common soil anions like sulfate, nitrate, and chloride. The basic advantages of the developed colorimetric method over the similar CRREL/Jenkins' method may be summarized as color stability, water and common ion

  16. Selective colorimetric determination of TNT partitioned between an alkaline solution and a strongly basic Dowex 1-X8 anion exchanger.

    PubMed

    Uzer, Ayşem; Erçağ, Erol; Apak, Reşat

    2008-01-30

    The Meisenheimer anions formed from TNT in KOH solutions in alcohol or acetone were used in screening tests for TNT among possible nitro-explosives. The same reaction was used for the spectrophotometric assay of TNT in soil by CRREL (Cold Regions Research & Engineering Laboratory of the U.S. Army) method, also known as Jenkins' method, but the color stability was too dependent on the solution composition and the water tolerance was low, necessitating complete drying of soil samples (which may cause partial analyte decomposition) prior to analysis. This study reports the development of a colorimetric method based on the solid phase extraction (SPE) of the Meisenheimer anion formed from TNT and aqueous NaOH into a strongly basic anion exchange resin Dowex 1-X8 (OH(-) form). The orange-red color that developed both in the solid resin and solution phases was persistent for at least 1h. The resin was let to swell in alcohol, washed first with 1M aqueous NaOH, and then with H(2)O before use. To 5 mL of 4-400 ppm TNT solutions in 1:1 (v/v) acetone-water, 0.5 mL of 5% NaOH was added, diluted to 50 mL with 1:1 acetone-water, and the resulting solutions (containing the orange-red Meisenheimer anion of TNT) were agitated at room temperature with 0.9 g resin for < or =50 min. TNT exhibited a reasonably constant distribution coefficient between the resin and aqueous phases. The absorbance of the filtered solutions was measured against a reagent blank at 500nm. The TNT-loaded resins were regenerated with 1M HCl containing sodium sulfite. The calibration line of filtrate absorbance versus analytical concentration was linear over two orders of magnitude between 0.4 and 40 ppm TNT in final solution. Unlike Jenkins' method, the method was tolerant to 100-fold (by mass) of common soil anions like sulfate, nitrate, and chloride. The basic advantages of the developed colorimetric method over the similar CRREL/Jenkins' method may be summarized as color stability, water and common ion

  17. Helicobacter pylori vacuolating toxin forms anion-selective channels in planar lipid bilayers: possible implications for the mechanism of cellular vacuolation.

    PubMed Central

    Tombola, F; Carlesso, C; Szabò, I; de Bernard, M; Reyrat, J M; Telford, J L; Rappuoli, R; Montecucco, C; Papini, E; Zoratti, M

    1999-01-01

    The Helicobacter pylori VacA toxin plays a major role in the gastric pathologies associated with this bacterium. When added to cultured cells, VacA induces vacuolation, an effect potentiated by preexposure of the toxin to low pH. Its mechanism of action is unknown. We report here that VacA forms anion-selective, voltage-dependent pores in artificial membranes. Channel formation was greatly potentiated by acidic conditions or by pretreatment of VacA at low pH. No requirement for particular lipid(s) was identified. Selectivity studies showed that anion selectivity was maintained over the pH range 4.8-12, with the following permeability sequence: Cl- approximately HCO3- > pyruvate > gluconate > K+ approximately Li+ approximately Ba2+ > NH4+. Membrane permeabilization was due to the incorporation of channels with a voltage-dependent conductance in the 10-30 pS range (2 M KCl), displaying a voltage-independent high open probability. Deletion of the NH2 terminus domain (p37) or chemical modification of VacA by diethylpyrocarbonate inhibited both channel activity and vacuolation of HeLa cells without affecting toxin internalization by the cells. Collectively, these observations strongly suggest that VacA channel formation is needed to induce cellular vacuolation, possibly by inducing an osmotic imbalance of intracellular acidic compartments. PMID:10049322

  18. Potentiometric sensor for the high throughput determination of tetramisole hydrochloride.

    PubMed

    Gupta, Vinod Kumar; Singh, Ashok Kumar; Gupta, Barkha

    2007-08-01

    The electrochemical response characteristics of poly(vinyl)chloride (PVC) based membrane sensors for determination of tetramisole hydrochloride (TmCl) is described. The membranes of these electrodes consist of tetramisole-tetraphenyl borate (Tm-TPB), chlorophenyl borate (Tm-ClPB), and phosphotungstate (Tm(3)-PT) ion associations dispersed in a PVC matrix with dibutylpthalate as a plasticizer. The electrodes were fully characterized in terms of composition, life span, usable pH range, and working concentration range and ionic strength. The electrodes showed Nernstian response over the concentration ranges of 7.4 x 10(-7) to 1.0 x 10(-2) M, 1.7 x 10(-6) to 1.0 x 10(-2) M, and 5.6 x 10(-6) to 1.0 x 10(-2) M TmCl, respectively, and were applied to the potentiometric determination of tetramisole ion in pure solutions and pharmaceutical preparations. The potentiometric determination was also used in the determination of tetramisole in pharmaceutical preparations in four batches of different expiration dates. The electrodes exhibited good selectivity for TmCl with respect to a large number of excipients such as inorganic cations, organic cations, amino acids, and sugars. The solubility product of the ion-pair and the formation constant of the precipitation reaction leading to the ion-pair formation were determined conductometrically. The new potentiometric method offers the advantages of high-throughput determination, simplicity, accuracy, automation feasibility, and applicability to turbid and colored sample solutions. PMID:17979641

  19. Development of a new chemically modified carbon paste electrode for selective determination of urinary and serum oxalate concentration.

    PubMed

    Soleymanpour, Ahmad; Shafaatian, Bita; Mirfakhraei, Homeira Sadat; Rezaeifard, Abdolreza

    2013-11-15

    The construction and evaluation of a novel modified carbon paste electrode with high selectivity toward oxalate ion are described. The constructed carbon paste potentiometric sensor for oxalate ion is based on the use of a zirconium salan complex as a good ionophore in the carbon paste matrix. The electrode exhibits a Nernstian slope of 29.1 mV/decade to oxalate ion over a wide concentration range from 1.5×10(-6) to 3.9 ×10(-2) mol L(-1) with a low detection limit of 7.0×10(-7) mol L(-1). The electrode possesses fast response time, satisfactory reproducibility, appropriate lifetime, and most importantly, good selectivity toward C2O4(2-) relative to a variety of common anions. The potentiometric response of the electrode is independent of the pH of the test solution in the pH range 2.5-8.0. The modified carbon paste electrode was successfully applied as an indicator electrode in potentiometric titration and potentiometric determination of oxalate ion in mineral water, blood serum and urine samples.

  20. Dynamic chemistry of anion recognition

    SciTech Connect

    Custelcean, Radu

    2012-01-01

    In the past 40 years, anion recognition by synthetic receptors has grown into a rich and vibrant research topic, developing into a distinct branch of Supramolecular Chemistry. Traditional anion receptors comprise organic scaffolds functionalized with complementary binding groups that are assembled by multistep organic synthesis. Recently, a new approach to anion receptors has emerged, in which the host is dynamically self-assembled in the presence of the anionic guest, via reversible bond formation between functional building units. While coordination bonds were initially employed for the self-assembly of the anion hosts, more recent studies demonstrated that reversible covalent bonds can serve the same purpose. In both cases, due to their labile connections, the molecular constituents have the ability to assemble, dissociate, and recombine continuously, thereby creating a dynamic combinatorial library (DCL) of receptors. The anionic guests, through specific molecular recognition, may then amplify (express) the formation of a particular structure among all possible combinations (real or virtual) by shifting the equilibria involved towards the most optimal receptor. This approach is not limited to solution self-assembly, but is equally applicable to crystallization, where the fittest anion-binding crystal may be selected. Finally, the pros and cons of employing dynamic combinatorial chemistry (DCC) vs molecular design for developing anion receptors, and the implications of both approaches to selective anion separations, will be discussed.

  1. 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

  2. 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…

  3. A novel porous anionic metal-organic framework with pillared double-layer structure for selective adsorption of dyes

    NASA Astrophysics Data System (ADS)

    Sheng, Shu-Nan; Han, Yi; Wang, Bin; Zhao, Cui; Yang, Fan; Zhao, Min-Jian; Xie, Ya-Bo; Li, Jian-Rong

    2016-01-01

    A novel porous anionic metal-organic framework, (Me2NH2)2[Zn2L1.5bpy]·2DMF (BUT-201; H4L=4,8-disulfonaphthalene-2,6-dicarboxylic acid; bpy=4,4-bipyridine; DMF=N,N-dimethylformamide), with pillared double-layer structure has been synthesized through the reaction of a sulfonated carboxylic acid ligand and Zn(NO3)2·6H2O with 4,4-bipyridine as a co-ligand. It is found that BUT-201 can rapidly adsorb cationic dyes with a smaller size such as Methylene Blue (MB) and Acriflavine Hydrochloride (AH) by substitution of guest (CH3)2NH2+, but has no adsorption towards the cationic dyes with a lager size such as Methylene Violet (MV), the anionic dyes like C. I. Acid Yellow 1 (AY1) and neutral dyes like C. I. Solvent Yellow 7 (SY7), respectively. The results show that the adsorption behavior of BUT-201 relates not only to the charge but also to the size/shape of dyes. Furthermore, the adsorbed dyes can be gradually released in the methanol solution of LiNO3.

  4. Reactivity of aluminum cluster anions with ammonia: Selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}

    SciTech Connect

    Grubisic, Andrej; Li Xiang; Gantefoer, Gerd; Bowen, Kit H.; Schnoeckel, Hansgeorg; Tenorio, Francisco J.; Martinez, Ana

    2009-11-14

    Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -} was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al{sub 13}{sup -}, were also observed to deplete. The disappearance of Al{sub 11}{sup -} and Al{sub 12}{sup -} was accompanied by concurrent production of Al{sub 11}NH{sub 3}{sup -} and Al{sub 12}NH{sub 3}{sup -} species, respectively. Theoretical simulations of the photoelectron spectrum of Al{sub 11}NH{sub 3}{sup -} showed conclusively that its ammonia moiety is chemisorbed without dissociation, although in the case of Al{sub 12}NH{sub 3}{sup -}, dissociation of the ammonia moiety could not be excluded. Moreover, since differences in calculated Al{sub n}{sup -}+NH{sub 3} (n=9-12) reaction energies were not able to explain the observed selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}, we concluded that thermodynamics plays only a minor role in determining the observed reactivity pattern, and that kinetics is the more influential factor. In particular, the conversion from the physisorbed Al{sub n}{sup -}(NH{sub 3}) to chemisorbed Al{sub n}NH{sub 3}{sup -} species is proposed as the likely rate-limiting step.

  5. Influence of Inner Transducer Properties on EMF Response and Stability of Solid-Contact Anion Selective Membrane Electrodes Based on Metalloporphyrin Ionophores

    PubMed Central

    Górski, Łukasz; Matusevich, Alexey; Pietrzak, Mariusz; Wang, Lin; Meyerhoff, Mark E.; Malinowska, Elżbieta

    2010-01-01

    The performance of solid-contact/coated wire type electrodes with plasticized PVC membranes containing metalloporphyrins as anion selective ionophores is reported. The membranes are deposited on transducers based on graphite pastes and graphite rods. The hydrophobicity of the underlying conductive transducer surface is found to be a key factor that influences the formation of an aqueous layer beneath the polymer film. Elimination of this ill-defined water layer greatly improves the electrochemical properties of the ion-sensors, such as EMF stability and life-time. Only highly lipophilic electrode substrates, namely graphite paste with mineral oil, were shown to prevent the formation of aqueous layer underneath the ion-sensing membrane. The possibility of employing Co(III)-tetraphenylporphyrin both as NO2− selective ionophore and as electron/ion conducting species to ensure ion-to-electron translation was also discussed based on the results of preliminary experiments. PMID:20357903

  6. Novel simple process for tocopherols selective recovery from vegetable oils by adsorption and desorption with an anion-exchange resin.

    PubMed

    Hiromori, Kousuke; Shibasaki-Kitakawa, Naomi; Nakashima, Kazunori; Yonemoto, Toshikuni

    2016-03-01

    A novel and simple low-temperature process was used to recover tocopherols from a deodorizer distillate, which is a by-product of edible oil refining. The process consists of three operations: the esterification of free fatty acids with a cation-exchange resin catalyst, the adsorption of tocopherols onto an anion-exchange resin, and tocopherol desorption from the resin. No degradation of tocopherols occurred during these processes. In the tocopherol-rich fraction, no impurities such as sterols or glycerides were present. These impurities are commonly found in the product of the conventional process. This novel process improves the overall recovery ratio and the mass fraction of the product (75.9% and 51.0wt%) compared with those in the conventional process (50% and 35wt%).

  7. 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. PMID:25281140

  8. Nickel(II) and copper(II) complexes with humic acid anions and their derivatives

    SciTech Connect

    Ryabova, I.N.

    2008-01-15

    Complexation of Ni(II) and Cu(II) in aqueous solutions with anions of humic acids, extracted from naturally oxidized coal, and with their hydroxymethyl derivatives is studied spectrophotometrically and potentiometrically. The complexation stoichiometry and the stability constants of the complexes are determined.

  9. Formation of anion-selective channels in the cell plasma membrane by the toxin VacA of Helicobacter pylori is required for its biological activity.

    PubMed Central

    Szabò, I; Brutsche, S; Tombola, F; Moschioni, M; Satin, B; Telford, J L; Rappuoli, R; Montecucco, C; Papini, E; Zoratti, M

    1999-01-01

    The vacuolating toxin VacA, a major determinant of Helicobacter pylori-associated gastric diseases, forms anion-selective channels in artificial planar lipid bilayers. Here we show that VacA increases the anion permeability of the HeLa cell plasma membrane and determines membrane depolarization. Electrophysiological and pharmacological approaches indicated that this effect is due to the formation of low-conductance VacA pores in the cell plasma membrane and not to the opening of Ca(2+)- or volume-activated chloride channels. VacA-dependent increase of current conduction both in artificial planar lipid bilayers and in the cellular system was effectively inhibited by the chloride channel blocker 5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB), while2-[(2-cyclopentenyl-6,7dichloro-2, 3-dihydro-2-methyl-1-oxo-1H-inden-5-yl)oxy]acetic acid (IAA-94) was less effective. NPPB inhibited and partially reversed the vacuolation of HeLa cells and the increase of ion conductivity of polarized Madine Darby canine kidney cell monolayers induced by VacA, while IAA-94 had a weaker effect. We conclude that pore formation by VacA accounts for plasma membrane permeabilization and is required for both cell vacuolation and increase of trans-epithelial conductivity. PMID:10523296

  10. 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.

  11. [Semiautomatic potentiometric titration of gastric juice].

    PubMed

    Mnuskina, M M; Meerov, G I; Nadezhina, L S; Semenov, V P; Chekanina, M I; Savchenko, V P; Grinzaĭd, E L

    1990-01-01

    Using commercial equipment manufactured in this country, the authors have assembled a unit for semiautomatic potentiometric titration and developed a method for such titration, permitting a rapid determination of free and bound HCl and the total acidity of the gastric juice. The equipment and method are recommended for wide use at laboratories of therapeutic institutions, of biologic factories manufacturing medicinal commercial gastric juice, and of research institutes.

  12. Potentiometric responses of polymeric liquid membranes based on hydrophobic chelating agents to metal ions.

    PubMed

    Itoh, Y; Ueda, Y; Hirano, A; Sugawara, M; Tohda, K; Akaiwa, H; Umezawa, Y

    2001-05-01

    The effect of hydrophobicity of acidic chelating agents as sensing materials on the potentiometric responses of polymeric liquid membranes was investigated. The chelating agents tested were 8-quinolinol (HOx), dithizone (HDz), 1-(2-pyridylazo)-2-naphthol (PAN) and their alkylated analogues, 5-octyloxymethyl-8-quinolinol (HO8Q), di(phexylphenyl)thiocarbazone (C6HDz), 7-pentadecyloxy-1-(2-pyridylazo)-2-naphthol (C15PAN) and a series of N-alkylcarbonyl-N-phenylhydroxylamines (CnPHA, n = 3, 6, 9, 12). The distribution coefficients between membrane solvent and water were determined to evaluate the hydrophobicity of the agents. The potential-pH profiles of the membranes containing hydrophobic chelating agents demonstrated the generation of potentiometric responses, while less hydrophobic agents gave no response. A possible model for the generation of membrane potential is proposed. The charge separation is attained by the permselective uptake of metal cations by the chelating agent anion at membrane/solution interface, where the high hydrophobicity of the agent enables the anionic or deprotonated form of the agents to remain at the membrane/solution interface.

  13. Selective recognition of sulfate anions in a 95% ethanol solvent with a simple neutral salicylaldehyde dansyl hydrazine Schiff base tuned by Brønsted-Lowry acid-base reaction.

    PubMed

    Wei, Gao-Ning; Zhang, Jing-Li; Jia, Cang; Fan, Wei-Zhen; Lin, Li-Rong

    2014-07-15

    A new Schiff base compound, 5-(dimethylamino)-N'-(2-hydroxybenzylidene)naphthalene-1-sulfonohydrazide (R), has been synthesized, characterized, and employed as a selective fluorescence receptor for the recognition of sulfate anions. UV-vis absorption, fluorescence emission, (1)H NMR spectra and DFT calculation studies on the system have been carried out to determine the nature of the interactions between R and anions. The results reveal that the deprotonation of the phenol without the need of a strong base leads to the formation of a hydrogen-bonding complex with a -SO2-NH- group, which is responsible for the spectra changes. The deprotonation process for the selectivity recognition of sulfate can be tuned by the Brønsted-Lowry acid-base reaction in nonaqueous solutions, revealing that suitable phenolic hydroxyl acidity is the key factor for anion recognition selectivity.

  14. Selective determination of ammonium ions by high-speed ion-exclusion chromatography on a weakly basic anion-exchange resin column.

    PubMed

    Mori, Masanobu; Tanaka, Kazuhiko; Helaleh, Murad I H; Xu, Qun; Ikedo, Mikaru; Ogura, Yutaka; Sato, Shinji; Hu, Wenzhi; Hasebe, Kiyoshi

    2003-05-16

    This paper describes an ion-exclusion chromatographic system for the rapid and selective determination of ammonium ion. The optimized ion-exclusion chromatographic system was established with a polymethacrylate-based weakly basic anion-exchange resin column (TSKgel DEAE-5PW) as the separation column, an aqueous solution containing 0.05 mM tetramethylammonium hydroxide (pH 9.10) as eluent with conductimetric detection for the analyte determination. Under the optimum chromatographic conditions, ammonium ion was determined within 2.3 min with a detection limit (S/N=3) better than 0.125 microM. Ammonium ion in rain and river waters was precisely determined using this ion-exclusion chromatographic system.

  15. Nitrate reduction by mixed iron(II-III) hydroxycarbonate green rust in the presence of phosphate anions: the key parameters influencing the ammonium selectivity.

    PubMed

    Etique, Marjorie; Zegeye, Asfaw; Grégoire, Brian; Carteret, Cédric; Ruby, Christian

    2014-10-01

    The reduction of nitrate anions by a mixed Fe(II)-Fe(III) carbonated green rust (GR) in aqueous medium is studied as a function of the initial pH and the initial concentrations of iron, phosphate and nitrate. The influence of these parameters on the fraction of nitrate removed and the production of ammonium is investigated by the help of statistical experimental designs. The goal is to determine experimental conditions that maximize the fraction of NO3(-) removed and concomitantly minimize the production of NH4(+). Increasing the phosphate concentration relatively to the initial Fe(II) concentration inhibits the reduction of nitrate probably due to a surface saturation of the lateral sites of the GR crystals. The kinetics of the reaction is greatly enhanced by increasing the initial pH at 10.5, however it leads to a global increase of the NH4(+) production. A partial saturation of the surface sites by phosphate leads to a global decrease of selectivity of the reaction towards ammonium. The evolution of the ratio of the NH4(+) concentration to the Fe(II) concentration confirms that the NO3(-) species are only partially transformed into ammonium. Interestingly at an initial pH of 7.5, the selectivity of the reaction towards NH4(+) is often lower than ∼30%. The reduction of nitrate by carbonated GR differs from the behavior of other GRs incorporating Cl(-), F(-) and SO4(2-) anions that fully transform nitrate into ammonium. Finally, if GR is intended to be used during a passive water denitrification process, complementary dephosphatation and ammonium treatments should be considered.

  16. Nitrate reduction by mixed iron(II-III) hydroxycarbonate green rust in the presence of phosphate anions: the key parameters influencing the ammonium selectivity.

    PubMed

    Etique, Marjorie; Zegeye, Asfaw; Grégoire, Brian; Carteret, Cédric; Ruby, Christian

    2014-10-01

    The reduction of nitrate anions by a mixed Fe(II)-Fe(III) carbonated green rust (GR) in aqueous medium is studied as a function of the initial pH and the initial concentrations of iron, phosphate and nitrate. The influence of these parameters on the fraction of nitrate removed and the production of ammonium is investigated by the help of statistical experimental designs. The goal is to determine experimental conditions that maximize the fraction of NO3(-) removed and concomitantly minimize the production of NH4(+). Increasing the phosphate concentration relatively to the initial Fe(II) concentration inhibits the reduction of nitrate probably due to a surface saturation of the lateral sites of the GR crystals. The kinetics of the reaction is greatly enhanced by increasing the initial pH at 10.5, however it leads to a global increase of the NH4(+) production. A partial saturation of the surface sites by phosphate leads to a global decrease of selectivity of the reaction towards ammonium. The evolution of the ratio of the NH4(+) concentration to the Fe(II) concentration confirms that the NO3(-) species are only partially transformed into ammonium. Interestingly at an initial pH of 7.5, the selectivity of the reaction towards NH4(+) is often lower than ∼30%. The reduction of nitrate by carbonated GR differs from the behavior of other GRs incorporating Cl(-), F(-) and SO4(2-) anions that fully transform nitrate into ammonium. Finally, if GR is intended to be used during a passive water denitrification process, complementary dephosphatation and ammonium treatments should be considered. PMID:24934322

  17. Galvanic cell without liquid junction for potentiometric determination of copper.

    PubMed

    Migdalski, Jan; Błaz, Teresa; Zrałka, Barbara; Lewenstam, Andrzej

    2007-07-01

    This paper describes potentiometric measurements in an integrated galvanic cell with both indicator and reference electrodes. Both electrodes are conducting polymer-based. The copper-sensitive indicator electrode is made by using poly(3,4-ethylenedioxythiophene) (PEDOT) doped with 2-(o-arsenophenylazo)-1,8-dihydroxynaphthalene-3,6-disulphonic sodium salt (Arsenazo-I) as the electroactive substance in the film, while the reference electrode is based on PEDOT doped by 2-morpholineoethanesulfonic acid (MES). It is shown that the galvanic cell can be used for determination of copper both in non-aqueous media (where all PVC-based membranes failed) and in the presence of chloride ions, which disturb the signal of conventional copper ion-selective electrodes with solid-state membranes. It is further shown that the titration of copper ions can be successfully monitored using the described electrochemical cell.

  18. Potentiometric detection and removal of copper using porphyrins

    PubMed Central

    2013-01-01

    Background Copper is an essential trace element with a great importance in industry, environment and biological systems. The great advantage of ion-selective sensors in comparison with other proposed techniques is that they are measuring the free metal ion activity which is responsible for their toxicity. Porphyrins are known to be among the best ionophores in formulation of ion-selective sensors. Results A symmetrically substituted meso-porphyrin, namely: 5,10,15,20-tetrakis(4-allyloxyphenyl)porphyrin (TAPP) was used in the construction of a new copper selective-sensor and was also tested for the removal of copper from waste waters. The potentiometric response characteristics (slope and selectivity) of copper-selective electrodes based on TAPP in o-nitrophenyloctylether (o-NPOE), dioctyl phtalate (DOP) and dioctyl sebacate (DOS) plasticized with poly(vinyl chloride) membranes are compared. Conclusions The best results were obtained for the membrane plasticized with DOP. The sensor has linear response in the range 1x10-7 – 1x10-1 M with 28.4 ± 0.4 mV/decade near-Nernstian slope towards copper ions and presents good selectivity. Due to its chelating nature, the same porphyrin was also tested for the retention of copper from synthetic copper samples, showing a maximum adsorption capacity of 280 mg/g. PMID:23829792

  19. Selective recovery of Ag(I) coordination anion from simulate nickel electrolyte using corn stalk based adsorbent modified by ammonia-thiosemicarbazide.

    PubMed

    Xiong, Ying; Wan, Li; Xuan, Jing; Wang, Yongwei; Xing, Zhiqing; Shan, Weijun; Lou, Zhenning

    2016-01-15

    In nickel electrolyte, Ag(I) was present at trace level concentration (10-20 mg L(-1)) and existed in the form of AgCli(1-i) coordination anion, instead of Ag(+) positive ion usually in several sources. In the present study, TSC-NH3-OCS adsorbent based on natural corn stalk modified by ammonia (NH3)-thiosemicarbazide (TSC) was synthesized and characterized using some instrumental techniques. The TSC-NH3-OCS adsorbent could selectively adsorb Ag(I) as AgCl(i)(1-i) coordination anion from the Ag(I)-Cu(II)-Ni(II) simulate nickel electrolyte, especially in the case of the very high levels of Cu(II) and Ni(II), which significantly outperforms the commercial available resins. The adsorption mechanism was believed to be electrostatic interaction of the protonated bands of AgCl4(3-) with protonated thiol form of the thioamide units by FTIR and XPS analysis. The maximum adsorption capacity in the Ag(I) single and Ag(I)-Cu(II)-Ni(II) ternary system were obtained and calculated as 153.54 and 46.69 mg g(-1), respectively. The reasons that the maximum adsorption capacity of AgCl(i)(1-i) from the single and ternary system varied widely could be explained by adsorption kinetic and thermodynamic results. In addition, three successive sorption/desorption cycle runs from ternary system were performed which indicated that the TSC-NH3-OCS adsorbent has a good performance for recovery Ag(I) from simulate nickel electrolyte.

  20. Selectivity issues in targeted metabolomics: Separation of phosphorylated carbohydrate isomers by mixed-mode hydrophilic interaction/weak anion exchange chromatography.

    PubMed

    Hinterwirth, Helmut; Lämmerhofer, Michael; Preinerstorfer, Beatrix; Gargano, Andrea; Reischl, Roland; Bicker, Wolfgang; Trapp, Oliver; Brecker, Lothar; Lindner, Wolfgang

    2010-11-01

    Phosphorylated carbohydrates are important intracellular metabolites and thus of prime interest in metabolomics research. Complications in their analysis arise from the existence of structural isomers that do have similar fragmentation patterns in MS/MS and are hard to resolve chromatographically. Herein, we present selective methods for the liquid chromatographic separation of sugar phosphates, such as hexose and pentose phosphates, 2- and 3-phosphoglycerate, dihydroxyacetone phosphate and glyceraldehyde 3-phosphate, as well as glucosamine 1- and 6-phosphate utilizing mixed-mode chromatography with reversed-phase/weak anion-exchangers and a charged aerosol detector. The best results were obtained when the reversed-phase/weak anion-exchanger column was operated under hydrophilic interaction liquid chromatography elution conditions. The effects of various chromatographic parameters were examined and are discussed on the basis of a simple stoichiometric displacement model for explaining ion-exchange processes. Employed acidic conditions have led to the complete separation of α- and β-anomers of glucose 6-phosphate at low temperature. The anomers coeluted in a single peak at elevated temperatures (>40°C) (peak coalescence), while at intermediate temperatures on-column interconversion with a plateau in-between resolved anomer peaks was observed with apparent reaction rate constants between 0.1 and 27.8×10(-4) s(-1). Dynamic HPLC under specified conditions enabled to investigate mutarotation of phosphorylated carbohydrates, their interconversion kinetics, and energy barriers for interconversion. A complex mixture of six hexose phosphate structural isomers could be resolved almost completely.

  1. Selective recovery of Ag(I) coordination anion from simulate nickel electrolyte using corn stalk based adsorbent modified by ammonia-thiosemicarbazide.

    PubMed

    Xiong, Ying; Wan, Li; Xuan, Jing; Wang, Yongwei; Xing, Zhiqing; Shan, Weijun; Lou, Zhenning

    2016-01-15

    In nickel electrolyte, Ag(I) was present at trace level concentration (10-20 mg L(-1)) and existed in the form of AgCli(1-i) coordination anion, instead of Ag(+) positive ion usually in several sources. In the present study, TSC-NH3-OCS adsorbent based on natural corn stalk modified by ammonia (NH3)-thiosemicarbazide (TSC) was synthesized and characterized using some instrumental techniques. The TSC-NH3-OCS adsorbent could selectively adsorb Ag(I) as AgCl(i)(1-i) coordination anion from the Ag(I)-Cu(II)-Ni(II) simulate nickel electrolyte, especially in the case of the very high levels of Cu(II) and Ni(II), which significantly outperforms the commercial available resins. The adsorption mechanism was believed to be electrostatic interaction of the protonated bands of AgCl4(3-) with protonated thiol form of the thioamide units by FTIR and XPS analysis. The maximum adsorption capacity in the Ag(I) single and Ag(I)-Cu(II)-Ni(II) ternary system were obtained and calculated as 153.54 and 46.69 mg g(-1), respectively. The reasons that the maximum adsorption capacity of AgCl(i)(1-i) from the single and ternary system varied widely could be explained by adsorption kinetic and thermodynamic results. In addition, three successive sorption/desorption cycle runs from ternary system were performed which indicated that the TSC-NH3-OCS adsorbent has a good performance for recovery Ag(I) from simulate nickel electrolyte. PMID:26368801

  2. Treatment of Perchlorate-Contaminated Groundwater Using Highly-Selective, Regenerable Anion-Exchange Resins at Edwards Air Force Base

    SciTech Connect

    Gu, B.

    2003-05-30

    Selective ion exchange is one of the most effective treatment technologies for removing low levels of perchlorate (ClO{sub 4}{sup -}) from contaminated water because of its high efficiency without adverse impacts on the water quality caused by adding or removing any chemicals or nutrients. This report summarizes both the laboratory and a field pilot-scale studies to determine the ability and efficiency of the bifunctional synthetic resins to remove ClO{sub 4}{sup -} from the contaminated groundwater at the Edwards Air Force Base in California. Regeneration of the resins after groundwater treatment was also evaluated using the FeCl{sub 3}-HCl regeneration technique recently developed at Oak Ridge National Laboratory. On the basis of this study, the bifunctional resin, D-3696 was found to be highly selective toward ClO{sub 4}{sup -} and performed much better than one of the best commercial nitrate-selective resins (Purolite A-520E) and more than an order of magnitude better than the Purolite A-500 resin (with a relatively low selectivity). At an influent concentration of {approx} 450 {micro}g/L ClO{sub 4}{sup -} in groundwater, the bifunctional resin bed treated {approx} 40,000 empty bed volumes of groundwater before a significant breakthrough of ClO{sub 4}{sup -} occurred. The presence of relatively high concentrations of chloride and sulfate in site groundwater did not appear to affect the ability of the bifunctional resin to remove ClO{sub 4}{sup -}. However, the presence of high iron or iron oxyhydroxides and/or biomass in groundwater caused a significant fouling of the resin beds and greatly influenced the effectiveness in regenerating the resins sorbed with ClO{sub 4}{sup -}. Under such circumstances, a prefilter ({approx} 0.5-1 {micro}m) was found to be necessary to remove these particulates and to reduce the risk of fouling of the resin beds. Without significant fouling, the resin bed could be effectively regenerated by the FeCl{sub 3} displacement technique

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

    NASA Astrophysics Data System (ADS)

    Liang, Rongning; Chen, Lusi; Qin, Wei

    2015-07-01

    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.

  4. 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

  5. Anion transport with halogen bonds.

    PubMed

    Jentzsch, Andreas Vargas; Matile, Stefan

    2015-01-01

    This review covers the application of halogen bonds to transport anions across lipid bilayer membranes. The introduction provides a brief description of biological and synthetic transport systems. Emphasis is on examples that explore interactions beyond the coordination with lone pairs or hydrogen bonds for the recognition of cations and anions, particularly cation-π and anion-π interactions, and on structural motifs that are relevant for transport studies with halogen bonds. Section 2 summarizes the use of macrocyclic scaffolds to achieve transport with halogen bonds, focusing on cyclic arrays of halogen-bond donors of different strengths on top of calixarene scaffolds. This section also introduces methods to study anion binding in solution and anion transport in fluorogenic vesicles. In Sect. 3, transport studies with monomeric halogen bond-donors are summarized. This includes the smallest possible organic anion transporter, trifluoroiodomethane, a gas that can be bubbled through a suspension of vesicles to turn on transport. Anion transport with a gas nicely illustrates the power of halogen bonds for anion transport. Like hydrogen bonds, they are directional and strong, but compared to hydrogen-bond donors, halogen-bond donors are more lipophilic. Section 3 also offers a concise introduction to the measurement of ion selectivity in fluorogenic vesicles and conductance experiments in planar bilayer membranes. Section 4 introduces the formal unrolling of cyclic scaffolds into linear scaffolds that can span lipid bilayers. As privileged transmembrane scaffolds, the importance of hydrophobically matching fluorescent p-oligophenyl rods is fully confirmed. The first formal synthetic ion channel that operates by cooperative multiion hopping along transmembrane halogen-bonding cascades is described. Compared to homologs for anion-π interactions, transport with halogen bonds is clearly more powerful.

  6. Potentiometric surfaces of the Mississippi River Valley alluvial aquifer in eastern Arkansas, spring 1972 and 1980

    USGS Publications Warehouse

    Ackerman, D.J.

    1989-01-01

    Maps that show contours of the altitude of water levels for wells completed in the Mississippi River Valley alluvial aquifer in eastern Arkansas were prepared using water-level measurements made in the spring of 1972-1980. Hydrographs for selected wells are included to show trends and lack of trends in water-level changes. The aquifer consists of gravel and sand in flood-plain and terrace deposits of Quaternary age. The aquifer supplies much of the water used for irrigation and aquaculture in eastern Arkansas. A large depression in the potentiometric surface caused by pumping for irrigation and aquaculture occurs in Arkansas, Lonoke, and Prairie Counties. A smaller depression in the potentiometric surface occurs north of Brinkley. Significant water-level declines occurred during the period 1972-80 in several counties west of Crowleys Ridge. (USGS)

  7. Mitochondrial Injury after Mechanical Stretch of Cortical Neurons in vitro: Biomarkers of Apoptosis and Selective Peroxidation of Anionic Phospholipids

    PubMed Central

    Ji, Jing; Tang, Minke; Feng, Weihong; Stolz, Donna B.; Clark, Robert S.B.; Meaney, David F.; Kochanek, Patrick M.; Kagan, Valerian E.

    2012-01-01

    Abstract Mechanical injury of neurites accompanied by rupture of mitochondrial membranes may lead to immediate nonspecific release and spreading of pro-apoptotic factors and activation of proteases, that is, execution of apoptotic program. In the current work, we studied the time course of the major biomarkers of apoptosis as they are induced by exposure of rat cortical neurons to mechanical stretch. By using transmission electron microscopy, we found that mitochondria in the neurites were damaged early (1 h) after mechanical stretch injury whereas somal mitochondria were significantly more resistant and demonstrated structural damage and degenerative mitochondrial changes at a later time point after stretch (12 h). We also report that the stretch injury caused immediate activation of reactive oxygen species production followed by selective oxidation of a mitochondria-specific phospholipid, cardiolipin, whose individual peroxidized molecular species have been identified and quantified by electrospray ionization mass spectrometry analysis. Most abundant neuronal phospholipids – phosphatidylcholine, phophatidylethanolamine – did not undergo oxidative modification. Simultaneously, a small-scale release of cytochrome c was observed. Notably, caspase activation and phosphatidylserine externalization – two irreversible apoptotic events designating a point of no return – are substantially delayed and do not occur until 6–12 h after the initial impact. The early onset of reactive oxygen species production and cytochrome c release may be relevant to direct stretch-induced damage to mitochondria. The delayed emergence of apoptotic neuronal death after the immediate mechanical damage to mitochondria suggests a possible window of opportunity for targeted therapies. PMID:21895519

  8. Identification of mud crab reovirus VP12 and its interaction with the voltage-dependent anion-selective channel protein of mud crab Scylla paramamosain.

    PubMed

    Xu, Hai-Dong; Su, Hong-Jun; Zou, Wei-Bin; Liu, Shan-Shan; Yan, Wen-Rui; Wang, Qian-Qian; Yuan, Li-Li; Chan, Siuming Francis; Yu, Xiao-Qiang; He, Jian-Guo; Weng, Shao-Ping

    2015-05-01

    Mud crab reovirus (MCRV) is the causative agent of a severe disease in cultured mud crab (Scylla paramamosain), which has caused huge economic losses in China. MCRV is a double-stranded RNA virus with 12 genomic segments. In this paper, SDS-PAGE, mass spectrometry and Western blot analyses revealed that the VP12 protein encoded by S12 gene is a structural protein of MCRV. Immune electron microscopy assay indicated that MCRV VP12 is a component of MCRV outer shell capsid. Yeast two hybrid cDNA library of mud crab was constructed and mud crab voltage-dependent anion-selective channel (mcVDAC) was obtained by MCRV VP12 screening. The full length of mcVDAC was 1180 bp with an open reading frame (ORF) of 849 bp encoding a 282 amino acid protein. The mcVDAC had a constitutive expression pattern in different tissues of mud crab. The interaction between MCRV VP12 and mcVDAC was determined by co-immunoprecipitation assay. The results of this study have provided an insight on the mechanisms of MCRV infection and the interactions between the virus and mud crab.

  9. Structure and orientation of two voltage-dependent anion-selective channel isoforms. An attenuated total reflection fourier-transform infrared spectroscopy study.

    PubMed

    Abrecht, H; Goormaghtigh, E; Ruysschaert, J M; Homble, F

    2000-12-29

    Two VDAC (voltage-dependent anion-selective channel) isoforms were purified from seed cotyledons of Phaseolus vulgaris by chromatofocusing chromatography. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy was used to study the structural properties of the two isoforms reconstituted in a mixture of asolectin and 5% stigmasterol. The IR spectra of the two VDAC isoforms were highly similar indicating 50 to 53% anti-parallel beta-sheet. The orientation of the beta-strands relative to the barrel axis was calculated from the experimentally obtained dichroic ratios of the amide I beta-sheet component and the amide II band. Comparing the IR spectra of the reconstituted VDAC isoforms with the IR spectra of the bacterial porin OmpF, for which a high resolution structure is available, provided evidence for a general structural organization of the VDAC isoforms similar to that of bacterial porins. Hydrogen-deuterium exchange measurements indicated that the exchange of the amide protons occurs to a higher extent in the two VDAC isoforms than in the OmpF porin.

  10. Kinetics, stoichiometry, and anion selectivity of cAMP-stimulated Cl-HCO/sub 3/ exchange in rabbit cortical collecting tubule (CCT)

    SciTech Connect

    Schuster, V.L.

    1986-03-01

    Cyclic AMP stimulates net HCO/sub 3/ secretion in rabbit CCT (Schuster, JCI 75:2056). Because cAMP induces Cl-independent (electrogenic) HCO/sub 3/ secretion in several epithelia, I studied the anion dependence of the CCT cAMP effect. Tubules were perfused in vitro with lumen amiloride; bath cAMP was continuously present to stimulate HCO/sub 3/ secretion. First, the dependence of HCO/sub 3/ secretion on lumen (Cl) was determined. With bath (Cl)=O mM, perfusate (Cl) was varied (2-150 mM, gluconate substitution). Mean lumen (Cl) was determined either by a silver electrode in the collected fluid (2-12 mM perfusate) or by /sup 36/Cl (12-150 mM). Total bath-to-lumen HCO/sub 3/ flux, J/sup Ib//sub HCO3/, was measured (bath HCO/sub 3/=25 mM, perfusate HCO/sub 3/=O), Passive J/sub HCO3/ was estimated from the GHK equation using a previously-determined HCO/sub 3/ permeability = 1.9 x 10/sup -6/ cm/s. Mediated J/sub HCO3/ vs. mean lumen (Cl) showed saturation kinetics, apparent K/sub m/ = 5.8 mM and V/sub max/ = 8.7 pmol/mm/min. Second, the stoichiometry was estimated. When bath HCO/sub 3/ was replaced by HEPES at various perfusate (Cl) (12-150 mM), ..delta..J/sub HCO3/ varied linearly with ..delta..J/sup Ib/sub Cl/ (slope = .85 +- .27). Third, in anion selectivity studies Br supported HCO/sub 3/ secretion (89% rate with Cl) but I/sup -/ and SO/sub 4//sup =/ did not. In rabbit CCT, as opposed to several other HCO/sub 3/-secreting epithelia, cAMP stimulates 1:1 Cl-HCO/sub 3/ exchange.

  11. Tailoring the Pore Environment of Metal-Organic and Molecular Materials Decorated with Inorganic Anions: Platforms for Highly Selective Carbon Capture

    NASA Astrophysics Data System (ADS)

    Nugent, Patrick S.

    Due to their high surface areas and structural tunability, porous metal-organic materials, MOMs, have attracted wide research interest in areas such as carbon capture, as the judicious choice of molecular building block (MBB) and linker facilitates the design of MOMs with myriad topologies and allows for a systematic variation of the pore environment. Families of MOMs with modular components, i.e. MOM platforms, are eminently suitable for targeting the selective adsorption of guest molecules such as CO2 because their pore size and pore functionality can each be tailored independently. MOMs with saturated metal centers (SMCs) that promote strong yet reversible CO2 binding in conjunction with favorable adsorption kinetics are an attractive alternative to MOMs containing unsaturated metal centers (UMCs) or amines. Whereas MOMs with SMCs and exclusively organic linkers typically have poor CO2 selectivity, it has been shown that a versatile, long known platform with SMCs, pillared square grids with inorganic anion pillars and pcu topology, exhibits high and selective CO 2 uptake, a moderate CO2 binding affinity, and good stability under practical conditions. As detailed herein, the tuning of pore size and pore functionality in this platform has modulated the CO2 adsorption properties and revealed variants with unprecedented selectivity towards CO 2 under industrially relevant conditions, even in the presence of moisture. With the aim of tuning pore chemistry while preserving pore size, we initially explored the effect of pillar substitution upon the carbon capture properties of a pillared square grid, [Cu(bipy)2(SiF6)] (SIFSIX-1-Cu). Room temperature CO2, CH4, and N 2 adsorption isotherms revealed that substitution of the SiF6 2- ("SIFSIX") inorganic pillar with TiF6 2- ("TIFSIX") or SnF62- ("SNIFSIX") modulated CO2 uptake, CO2 affinity (heat of adsorption, Qst), and selectivity vs. CH4 and N2. TIFSIX-1-Cu and SNIFSIX-1-Cu were calculated to exhibit the highest CO2/N 2

  12. A comparison of coulometric titration and potentiometric determination of chloride concentration in rumen fluid.

    PubMed

    Cebra, Christopher K.; Tornquist, Susan J.; Vap, Lomda M.; Dodson, Linda A.

    2001-01-01

    The concentration of chloride ions in rumen fluid is a useful measure of obstructive gastrointestinal disease in ruminants and camelids. However, rumen fluid is very different from other biological fluids in its bacterial populations, consistency, and concentrations of various anions. Two methods of determining the chloride concentration in biological fluids were compared using centrifuged and filtered rumen fluid containing different amounts of sodium chloride. Although coulometric titration and potentiometric electrode analysis yielded results that had a strong linear relationship, the results of potentiometry were consistently and significantly higher, by about 20 mEq/L. This difference was investigated further by analyzing a series of fluids containing different concentrations of sodium acetate. Acetate was detected as chloride (0.21 chloride molecules per acetate molecule) by potentiometry but not by coulometric titration. Therefore, the acetate concentration of rumen fluid was the most likely cause of the discrepancy between tests in the original trial. In conclusion, the coulometric procedure may be more accurate than the potentiometric procedure for measuring rumen chloride when the concentrations of possible confounding ions are unknown.

  13. Injectable gels of anionic collagen:rhamsan composites for plastic correction: preparation, characterization, and rheological properties.

    PubMed

    de Paula, Márcio; Goissis, Gilberto; Martins, Virgínia C A; da Silva Trindade, José Carlos

    2005-11-01

    The present article describes the preparation and characterization of anionic collagen gels obtained from porcine intestinal submucosa after 72 h of alkaline treatment and in the form of rhamsan composites to develop injectable biomaterials for plastic reconstruction. All materials were characterized by SDS/polyacrylamide gel electrophoresis, infrared spectroscopy, thermal stability, potentiometric titration, rheological properties, and fluidity tests. Biocompatibility was appraised after the injection of anionic collagen: rhamsan composites at 2.5% in 60 North Folk rabbits. Independently of processing, the collagen's secondary structure was preserved in all cases, and after 72 h of hydrolysis the collagen was characterized by a carboxyl group content of 346+/-9, which, at physiological pH, corresponds to an increase of 106+/-17 negative charges, in comparison to native collagen, due to the selective hydrolysis of asparagine and glutamine carboxyamide side chain. Rheological studies of composites at pH 7.4 in concentrations of 2, 4, and 6% (in proportions of 75:1 and 50:1) showed a viscoelastic behavior dependent on the frequency, which is independent of concentration and proportion. In both, the concentration of the storage modulus always predominated over the loss modulus (G'>G'' and delta<45 degrees ). The results from creep experiments confirmed this behavior and showed that anionic collagen:rhamsan composites at pH 7.4 in the proportion of 50:1 are less elastic and more susceptible to deformation in comparison to gels in the proportion of 75:1, independent of concentration. This was further confirmed by flow experiments, indicating that the necessary force for the extrusion of anionic collagen:rhamsan composites, in comparison to anionic collagen, was significantly smaller and with a smooth flow. Biocompatibility studies showed that the tissue reaction of anionic collagen:rhamsan composites at 2.5% in the proportion of 75:1 was compatible with the application

  14. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Alexander, S.; Hodgdon, R. B.

    1977-01-01

    The objective of NAS 3-20108 was the development and evaluation of improved anion selective membranes useful as efficient separators in a redox power storage cell system being constructed. The program was divided into three parts, (a) optimization of the selected candidate membrane systems, (b) investigation of alternative membrane/polymer systems, and (c) characterization of candidate membranes. The major synthesis effort was aimed at improving and optimizing as far as possible each candidate system with respect to three critical membrane properties essential for good redox cell performance. Substantial improvements were made in 5 candidate membrane systems. The critical synthesis variables of cross-link density, monomer ratio, and solvent composition were examined over a wide range. In addition, eight alternative polymer systems were investigated, two of which attained candidate status. Three other alternatives showed potential but required further research and development. Each candidate system was optimized for selectivity.

  15. Selective anion sensing by a tris-amide CTV derivative: 1H NMR titration, self-assembled monolayers, and impedance spectroscopy.

    PubMed

    Zhang, Sheng; Echegoyen, Luis

    2005-02-16

    A hydrogen-bond forming tris(amide) receptor based on cyclotriveratrylene (CTV) was prepared. Self-assembled monolayers (SAMs) of the receptor were formed on gold surfaces. Desorption experiments show a surface coverage of 2.26 x 10(-10) mol/cm(2). (1)H NMR and UV measurements confirm that the receptor exhibits the highest affinity for acetate ions among the anions studied. Electrochemical impedance was used to investigate anion sensing by the SAMs and proved to be an efficient and convenient technique for detecting anions in aqueous solutions. Upon binding acetate anions, the monolayer-modified gold electrodes show a drastic increase of the R(ct) values when Fe(CN)(6)(3-/4-) is used as the redox probe. When the probe was changed to a positively charged one, Ru(NH3)(6)(3+/2+), the R(ct) values decreased monotonically as the acetate concentration was increased, thus confirming the accumulation of negative surface charge upon anion binding. H(2)PO(4-) shows some interference when sensing AcO-. Other monovalent anions such as Cl-, Br-, NO3(-) and HSO4(-) do not bind to the CTV receptor either in solution or on the surfaces. PMID:15701037

  16. Potentiometric map of the Cockfield Aquifer in Mississippi, fall, 1980

    USGS Publications Warehouse

    Wasson, B.E.

    1981-01-01

    This potentiometric map of the Cockfield aquifer is the eleventh 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 Cockfield quifer 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 large ground-water withdrawals in the Jackson and Greenville areas. Historically, water levels in or near the outcrop of the Cockfield aquifer have shown little or no long-term changes, but in much of the confined part of the aquifer during the past 20 years, water levels have declined from 1 to 2 feet per year. (USGS)

  17. A simple-potentiometric method for determination of acid and alkaline phosphatase enzymes in biological fluids and dairy products using a nitrophenylphosphate plastic membrane sensor.

    PubMed

    Hassan, Saad S M; Sayour, Hossam E M; Kamel, Ayman H

    2009-04-27

    A novel poly(vinyl chloride) matrix membrane sensor responsive to 4-nitrophenylphosphate (4-NPP) substrate is described, characterized and used for the potentiometric assay of acid (ACP) and alkaline (ALP) phosphatase enzymes. The sensor is based on the use of the ion-association complex of 4-NPP anion with nickel(II)-bathophenanthroline cation as an electroactive material and nitrophenyloctyl ether (NPOE) as a solvent mediator. The sensor displays good selectivity and stability and demonstrates a near-Nernstian response for 4-NPP over the concentration range 9.6x10(-6) to 1.0x10(-2) M with an anionic slope of 28.6+/-0.3 mV decade(-1) and a detection limit of 6.3x10(-6) M over the pH range 4.5-10. The sensor is used to measure the decrease of a fixed concentration of 4-NPP substrate as a function of acid and alkaline phosphatase enzyme activities at optimized conditions of pH and temperature. A linear relationship between the initial rate of 4-NPP substrate hydrolysis and enzyme activity holds over 0.05-3.0 and 0.03-3.4 IU L(-1) of ACP and ALP enzymes, respectively. Validation of the method by measuring the lower detection limit, range, accuracy, precision, within-day repeatability and between-day-variability reveals good performance characteristics of the proposed sensor. The sensor is used for the determination of acid and alkaline phosphatase enzyme activities in biological fluids of some patients suffering from alcoholic cirrhosis, acute myelocytic leukemia, pre-eclampsia and prostatic cancer. The sensor is also utilized for assessment of alkaline phosphatase enzyme in milk and dairy products. The results obtained agree fairly well with data obtained by the standard spectrophotometric methods.

  18. 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

  19. New reversed phase-high performance liquid chromatographic method for selective separation of yttrium from all rare earth elements employing nitrilotriacetate complexes in anion exchange mode.

    PubMed

    Dybczyński, Rajmund S; Kulisa, Krzysztof; Pyszynska, Marta; Bojanowska-Czajka, Anna

    2015-03-20

    Separation of Y from other rare earth elements (REE) is difficult because of similarity of its ionic radius to ionic radii of Tb, Dy and Ho. In the new RP-HPLC system with C18 column, tetra-n-butyl ammonium hydroxide (TBAOH) as an ion interaction reagent (IIR), nitrilotriacetic acid (NTA) as a complexing agent at pH=2.8-3.5, and post column derivatization with Arsenazo III, yttrium is eluted in the region of light REE, between Nd and Sm and is base line separated from Nd and Sm and even from promethium. Simple model employing literature data on complex formation of REE with NTA and based on anion exchange mechanism was developed to foresee the order of elution of individual REE. The model correctly predicted that lanthanides up to Tb will be eluted in the order of increasing Atomic Number (At.No.) but all heavier REE will show smaller retention factors than Tb. Concurrent UV/VIS detection at 658nm and the use of radioactive tracers together with γ-ray spectrometric measurements made possible to establish an unique elution order of elution of REE: La, Ce, Pr, Nd, Pm, Y, Sm, Er, Ho, Tm, Yb, Eu, Lu, Dy+Gd, Tb, Sc. The real place of Y however, in this elution series differs from that predicted by the model (Y between Sm and Eu). The method described in this work enables selective separation of Y from La, Ce, Pr, Nd, Pm, Sm and all heavier REE treated as a group.

  20. Potentiometric and spectrophotometric determination of calcium in the wet end of paper machines by flow injection analysis.

    PubMed

    Nyman, J; Ivasca, A

    1993-01-01

    A spectrophotometric and a potentiometric FIA method were used to determine calcium in samples of back water from paper mills. The spectrophotometric method used the complexation reaction between calcium and o-cresolphthalein complexon. Optimum pH for the method was calculated theoretically. An ion-selective calcium electrode based on neutral carrier was used in the potentiometric method. The spectrophotometric method had a linear range between 10 and 250 ppm calcium and the potentiometric method between 10 and 300 ppm. Samples were acidified to pH 4 either before or after filtration. Total calcium was determined by a d.c. plasma emission method. Significant amounts of calcium were found to be bound both to the solid matter and to soluble complexes in the samples. The spectrophotometric method gave higher values than the potentiometric method but both of them gave lower values than the d.c. plasma emission method. Calcium concentrations in the range 30-250 ppm were found in the samples.

  1. Differential Recognition of Anions with Selectivity towards F(-) by a Calix[6]arene-Thiourea Conjugate Investigated by Spectroscopy, Microscopy, and Computational Modeling by DFT.

    PubMed

    Nehra, Anita; Bandaru, Sateesh; Yarramala, Deepthi S; Rao, Chebrolu Pulla

    2016-06-20

    Anion recognition studies were performed with triazole-appended thiourea conjugates of calix[6]arene (i.e., compound (6) L) by absorption and (1) H NMR spectroscopy by using nineteen different anions. The composition of the species of recognition was derived from ESI mass spectrometry. The absorption spectra of compound (6) L showed a new band at λ=455 nm in the presence of F(-) due to a charge transfer from the anion to the thiourea moiety and the absorbance increases almost linearly in the concentration range 5 to 200 μm. This is associated with a strong visual color change of the solution. Other anions, such as H2 PO4 (-) and HSO4 (-) , exhibit a redshift of the λ=345 nm band and the spectral changes are associated with the formation of an isosbestic point at λ=343 nm. (1) H NMR studies further confirm the binding of F(-) efficiently to the thiourea group among the halides by shifting the thiourea proton signals downfield followed by their disappearance after the addition of more than one equivalent of F(-) . The other anions also showed interactions with compound (6) L, however, their binding strength follows the order F(-) >CO3 (2-) >H2 PO4 (-) ≈CH3 COO(-) >HSO4 (-) . The NMR spectral changes clearly revealed the anion-binding region of the arms in case of all these anions. The anion binding to compound (6) L indeed stabilizes a flattened-cone conformation as deduced based on the calix-aromatic proton signals and was further confirmed by VT (1) H NMR experiments. The stabilization of the flattened-cone conformation was further augmented by the interaction of the butyl moiety of the nBu4 N(+) counterion. The structural features of the anion-bound species were demonstrated by DFT computations and the resultant structures carried the features that were predicted based on the (1) H NMR spectroscopic measurements. In addition, SEM images showed a marigold flower-type morphology for compound (6) L and this has been transformed into a chain

  2. Differential Recognition of Anions with Selectivity towards F(-) by a Calix[6]arene-Thiourea Conjugate Investigated by Spectroscopy, Microscopy, and Computational Modeling by DFT.

    PubMed

    Nehra, Anita; Bandaru, Sateesh; Yarramala, Deepthi S; Rao, Chebrolu Pulla

    2016-06-20

    Anion recognition studies were performed with triazole-appended thiourea conjugates of calix[6]arene (i.e., compound (6) L) by absorption and (1) H NMR spectroscopy by using nineteen different anions. The composition of the species of recognition was derived from ESI mass spectrometry. The absorption spectra of compound (6) L showed a new band at λ=455 nm in the presence of F(-) due to a charge transfer from the anion to the thiourea moiety and the absorbance increases almost linearly in the concentration range 5 to 200 μm. This is associated with a strong visual color change of the solution. Other anions, such as H2 PO4 (-) and HSO4 (-) , exhibit a redshift of the λ=345 nm band and the spectral changes are associated with the formation of an isosbestic point at λ=343 nm. (1) H NMR studies further confirm the binding of F(-) efficiently to the thiourea group among the halides by shifting the thiourea proton signals downfield followed by their disappearance after the addition of more than one equivalent of F(-) . The other anions also showed interactions with compound (6) L, however, their binding strength follows the order F(-) >CO3 (2-) >H2 PO4 (-) ≈CH3 COO(-) >HSO4 (-) . The NMR spectral changes clearly revealed the anion-binding region of the arms in case of all these anions. The anion binding to compound (6) L indeed stabilizes a flattened-cone conformation as deduced based on the calix-aromatic proton signals and was further confirmed by VT (1) H NMR experiments. The stabilization of the flattened-cone conformation was further augmented by the interaction of the butyl moiety of the nBu4 N(+) counterion. The structural features of the anion-bound species were demonstrated by DFT computations and the resultant structures carried the features that were predicted based on the (1) H NMR spectroscopic measurements. In addition, SEM images showed a marigold flower-type morphology for compound (6) L and this has been transformed into a chain

  3. Real-time potentiometric detection of bacteria in complex samples.

    PubMed

    Zelada-Guillén, Gustavo A; Bhosale, Suryakant V; Riu, Jordi; Rius, F Xavier

    2010-11-15

    Detecting and identifying pathogen bacteria is essential to ensure quality at all stages of the food chain and to diagnose and control microbial infections. Traditional detection methods, including those based on cell culturing, are tedious and time-consuming, and their further application in real samples generally implies more complex pretreatment steps. Even though state-of-the-art techniques for detecting microorganisms enable the quantification of very low concentrations of bacteria, to date it has been difficult to obtain successful results in real samples in a simple, reliable, and rapid manner. In this Article, we demonstrate that the label-free detection and identification of living bacteria in real samples can be carried out in a couple of minutes and in a direct, simple, and selective way at concentration levels as low as 6 colony forming units/mL (CFU) in complex matrices such as milk or 26 CFU/mL in apple juice where the pretreatment step of samples is extremely easy. We chose Escherichia coli ( E. coli ) CECT 675 cells as a model organism as a nonpathogenic surrogate for pathogenic E. coli O157:H7 to test the effectiveness of a potentiometric aptamer-based biosensor. This biosensor uses single-walled carbon nanotubes (SWCNT) as excellent ion-to-electron transducers and covalently immobilized aptamers as biorecognition elements. The selective aptamer-target interaction significantly changes the electrical potential, thus allowing for both interspecies and interstrain selectivity and enabling the direct detection of the target. This technique is therefore a powerful tool for the immediate identification and detection of microorganisms. We demonstrate the highly selective detection of living bacteria with an immediate linear response of up to 10(4) CFU/mL. The biosensor can be easily built and used, is regenerated without difficulty, and can be used at least five times with no loss in the minimum amount of detected bacteria.

  4. A quantitative electrochemical theory of the electrolyte permeability of mosaic membranes composed of selectively anion-permeable and selectively cation-permeable parts, and its experimental verification. II. A quantitative test of the theory in model systems which do not involve the use of auxiliary electrodes.

    PubMed

    NEIHOF, R; SOLLNER, K

    1955-05-20

    The theory of the electrolyte permeability of mosaic membranes composed of ideally anion-selective and ideally cation-selective parts in juxtaposition is tested in a model which consists of an all-electrolytic cyclic arrangement of four component parts: dilute solution/anion-selective membrane/concentrated solution/cation-selective membrane/dilute solution. In this system cations move from the concentrated to the dilute solution across the cation-selective membrane and an equivalent number of anions move through the anion-selective membrane. This movement of ions corresponds to a flow of current in the system. According to the theory, the number of equivalents of electrolyte which penetrate in any given time across the membranes must be identical with the number of faradays of electricity which flow during the same period. The system is essentially a combination of two menbrane-concentration cells arranged in series in a short-circuited state without the presence of electrodes. Experimentally the magnitude of the current was determined by measuring with probe electrodes the potential across an element of the circuit whose resistance was known and constant. The number of faradays of electricity (determined from time-current data) flowing in the system during a measured time was compared with the analytically determined number of equivalents of electrolyte which moved across the membranes during the same period. In a variety of experimental systems the two values show a 1:1 ratio with a mean deviation of +/- 1.8 per cent.

  5. A potentiometric biosensor for rapid on-site disease diagnostics.

    PubMed

    Tarasov, Alexey; Gray, Darren W; Tsai, Meng-Yen; Shields, Niall; Montrose, Armelle; Creedon, Niamh; Lovera, Pierre; O'Riordan, Alan; Mooney, Mark H; Vogel, Eric M

    2016-05-15

    Quantitative point-of-care (POC) devices are the next generation for serological disease diagnosis. Whilst pathogen serology is typically performed by centralized laboratories using Enzyme-Linked ImmunoSorbent Assay (ELISA), faster on-site diagnosis would infer improved disease management and treatment decisions. Using the model pathogen Bovine Herpes Virus-1 (BHV-1) this study employs an extended-gate field-effect transistor (FET) for direct potentiometric serological diagnosis. BHV-1 is a major viral pathogen of Bovine Respiratory Disease (BRD), the leading cause of economic loss ($2 billion annually in the US only) to the cattle and dairy industry. To demonstrate the sensor capabilities as a diagnostic tool, BHV-1 viral protein gE was expressed and immobilized on the sensor surface to serve as a capture antigen for a BHV-1-specific antibody (anti-gE), produced in cattle in response to viral infection. The gE-coated immunosensor was shown to be highly sensitive and selective to anti-gE present in commercially available anti-BHV-1 antiserum and in real serum samples from cattle with results being in excellent agreement with Surface Plasmon Resonance (SPR) and ELISA. The FET sensor is significantly faster than ELISA (<10 min), a crucial factor for successful disease intervention. This sensor technology is versatile, amenable to multiplexing, easily integrated to POC devices, and has the potential to impact a wide range of human and animal diseases.

  6. A potentiometric biosensor for rapid on-site disease diagnostics.

    PubMed

    Tarasov, Alexey; Gray, Darren W; Tsai, Meng-Yen; Shields, Niall; Montrose, Armelle; Creedon, Niamh; Lovera, Pierre; O'Riordan, Alan; Mooney, Mark H; Vogel, Eric M

    2016-05-15

    Quantitative point-of-care (POC) devices are the next generation for serological disease diagnosis. Whilst pathogen serology is typically performed by centralized laboratories using Enzyme-Linked ImmunoSorbent Assay (ELISA), faster on-site diagnosis would infer improved disease management and treatment decisions. Using the model pathogen Bovine Herpes Virus-1 (BHV-1) this study employs an extended-gate field-effect transistor (FET) for direct potentiometric serological diagnosis. BHV-1 is a major viral pathogen of Bovine Respiratory Disease (BRD), the leading cause of economic loss ($2 billion annually in the US only) to the cattle and dairy industry. To demonstrate the sensor capabilities as a diagnostic tool, BHV-1 viral protein gE was expressed and immobilized on the sensor surface to serve as a capture antigen for a BHV-1-specific antibody (anti-gE), produced in cattle in response to viral infection. The gE-coated immunosensor was shown to be highly sensitive and selective to anti-gE present in commercially available anti-BHV-1 antiserum and in real serum samples from cattle with results being in excellent agreement with Surface Plasmon Resonance (SPR) and ELISA. The FET sensor is significantly faster than ELISA (<10 min), a crucial factor for successful disease intervention. This sensor technology is versatile, amenable to multiplexing, easily integrated to POC devices, and has the potential to impact a wide range of human and animal diseases. PMID:26765531

  7. Tailoring the Pore Environment of Metal-Organic and Molecular Materials Decorated with Inorganic Anions: Platforms for Highly Selective Carbon Capture

    NASA Astrophysics Data System (ADS)

    Nugent, Patrick S.

    Due to their high surface areas and structural tunability, porous metal-organic materials, MOMs, have attracted wide research interest in areas such as carbon capture, as the judicious choice of molecular building block (MBB) and linker facilitates the design of MOMs with myriad topologies and allows for a systematic variation of the pore environment. Families of MOMs with modular components, i.e. MOM platforms, are eminently suitable for targeting the selective adsorption of guest molecules such as CO2 because their pore size and pore functionality can each be tailored independently. MOMs with saturated metal centers (SMCs) that promote strong yet reversible CO2 binding in conjunction with favorable adsorption kinetics are an attractive alternative to MOMs containing unsaturated metal centers (UMCs) or amines. Whereas MOMs with SMCs and exclusively organic linkers typically have poor CO2 selectivity, it has been shown that a versatile, long known platform with SMCs, pillared square grids with inorganic anion pillars and pcu topology, exhibits high and selective CO 2 uptake, a moderate CO2 binding affinity, and good stability under practical conditions. As detailed herein, the tuning of pore size and pore functionality in this platform has modulated the CO2 adsorption properties and revealed variants with unprecedented selectivity towards CO 2 under industrially relevant conditions, even in the presence of moisture. With the aim of tuning pore chemistry while preserving pore size, we initially explored the effect of pillar substitution upon the carbon capture properties of a pillared square grid, [Cu(bipy)2(SiF6)] (SIFSIX-1-Cu). Room temperature CO2, CH4, and N 2 adsorption isotherms revealed that substitution of the SiF6 2- ("SIFSIX") inorganic pillar with TiF6 2- ("TIFSIX") or SnF62- ("SNIFSIX") modulated CO2 uptake, CO2 affinity (heat of adsorption, Qst), and selectivity vs. CH4 and N2. TIFSIX-1-Cu and SNIFSIX-1-Cu were calculated to exhibit the highest CO2/N 2

  8. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.

    1982-01-01

    The synthesis and fabrication of polymeric anion permselective membranes for redox systems are discussed. Variations of the prime candidate anion membrane formulation to achieve better resistance and/or lower permeability were explored. Processing parameters were evaluated to lower cost and fabricate larger sizes. The processing techniques to produce more membranes per batch were successfully integrated with the fabrication of larger membranes. Membranes of about 107 cm x 51 cm were made in excellent yield. Several measurements were made on the larger sample membranes. Among the data developed were water transport and transference numbers for these prime candidate membranes at 20 C. Other work done on this system included characterization of a number of specimens of candidate membranes which had been returned after service lives of up to sixteen months. Work with new polymer constituents, with new N.P.'s, catalysts and backing fabrics is discussed. Some work was also done to evaluate other proportions of the ingredients of the prime candidate system. The adoption of a flow selectivity test at elevated temperature was explored.

  9. 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.

  10. Anion exchange membrane

    DOEpatents

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  11. Influence of Ionic Liquids on the Selectivity of Ion Exchange-Based Polymer Membrane Sensing Layers.

    PubMed

    Mendecki, Lukasz; Callan, Nicole; Ahern, Meghan; Schazmann, Benjamin; Radu, Aleksandar

    2016-01-01

    The applicability of ion exchange membranes is mainly defined by their permselectivity towards specific ions. For instance, the needed selectivity can be sought by modifying some of the components required for the preparation of such membranes. In this study, a new class of materials -trihexyl(tetradecyl)phosphonium based ionic liquids (ILs) were used to modify the properties of ion exchange membranes. We determined selectivity coefficients for iodide as model ion utilizing six phosphonium-based ILs and compared the selectivity with two classical plasticizers. The dielectric properties of membranes plasticized with ionic liquids and their response characteristics towards ten different anions were investigated using potentiometric and impedance measurements. In this large set of data, deviations of obtained selectivity coefficients from the well-established Hofmeister series were observed on many occasions thus indicating a multitude of applications for these ion-exchanging systems. PMID:27438837

  12. Influence of Ionic Liquids on the Selectivity of Ion Exchange-Based Polymer Membrane Sensing Layers.

    PubMed

    Mendecki, Lukasz; Callan, Nicole; Ahern, Meghan; Schazmann, Benjamin; Radu, Aleksandar

    2016-01-01

    The applicability of ion exchange membranes is mainly defined by their permselectivity towards specific ions. For instance, the needed selectivity can be sought by modifying some of the components required for the preparation of such membranes. In this study, a new class of materials -trihexyl(tetradecyl)phosphonium based ionic liquids (ILs) were used to modify the properties of ion exchange membranes. We determined selectivity coefficients for iodide as model ion utilizing six phosphonium-based ILs and compared the selectivity with two classical plasticizers. The dielectric properties of membranes plasticized with ionic liquids and their response characteristics towards ten different anions were investigated using potentiometric and impedance measurements. In this large set of data, deviations of obtained selectivity coefficients from the well-established Hofmeister series were observed on many occasions thus indicating a multitude of applications for these ion-exchanging systems.

  13. Influence of Ionic Liquids on the Selectivity of Ion Exchange-Based Polymer Membrane Sensing Layers

    PubMed Central

    Mendecki, Lukasz; Callan, Nicole; Ahern, Meghan; Schazmann, Benjamin; Radu, Aleksandar

    2016-01-01

    The applicability of ion exchange membranes is mainly defined by their permselectivity towards specific ions. For instance, the needed selectivity can be sought by modifying some of the components required for the preparation of such membranes. In this study, a new class of materials –trihexyl(tetradecyl)phosphonium based ionic liquids (ILs) were used to modify the properties of ion exchange membranes. We determined selectivity coefficients for iodide as model ion utilizing six phosphonium-based ILs and compared the selectivity with two classical plasticizers. The dielectric properties of membranes plasticized with ionic liquids and their response characteristics towards ten different anions were investigated using potentiometric and impedance measurements. In this large set of data, deviations of obtained selectivity coefficients from the well-established Hofmeister series were observed on many occasions thus indicating a multitude of applications for these ion-exchanging systems. PMID:27438837

  14. 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

  15. Polypyrrole-calcion film as a membrane and solid-contact in an indicator electrode for potentiometric titrations.

    PubMed

    Blaz, T; Migdalski, J; Lewenstam, A

    2000-06-21

    This paper shows the application of conducting polymers (CPs) for constructing potentiometric indicator electrodes. Two types of polypyrrole (PPy)-based calcium sensors are presented, one sensor with PPy-calcion film as the active part and the other sensor with PPy-calcion as a solid-state contact coated with a conventional membrane selective towards calcium ions. It is shown that the PPy-calcion film, due to the complexing properties of calcion ensuring high loading of the film with calcium, is sufficiently selective to be used as the active part or as a mediating layer of the indicator electrode. The electrode, with PPy-calcion film as the active part, was used as the indicator electrode in potentiometric titrations of calcium in mixed solvents, where conventional PVC-based electrode can not be used. For the first time, the practical applicability of PPy-based electrodes in titrations is demonstrated.

  16. Two analyte calibrations from the transient response of a single potentiometric sensor employed with the SIA technique.

    PubMed

    Cartas, Raul; Mimendia, Aitor; Legin, Andrey; Del Valle, Manel

    2010-01-15

    Simultaneous quantification of Cd(2+) and Pb(2+) in solution has been correctly targeted using the kinetic information from a single non-specific potentiometric sensor. Dual quantification was accomplished from the complex information in the transient response of an electrode used in a Sequential Injection Analysis (SIA) system and recorded after step injection of sample. Data was firstly preprocessed with the Discrete Wavelet Transform (DWT) to extract significant features and then fed into an Artificial Neural Network (ANN) for building the calibration model. DWT stage was optimized regarding the wavelet function and decomposition level, while the ANN stage was optimized on its structure. To simultaneously corroborate the effectiveness of the approach, two different potentiometric sensors were used as study case, one using a glass selective to Cd(2+) and another a PVC membrane selective to Pb(2+).

  17. Direct potentiometric determination of diastase activity in honey.

    PubMed

    Sak-Bosnar, Milan; Sakač, Nikola

    2012-11-15

    A novel method for the determination of diastase activity is reported. The method is based on a direct potentiometric measurement of triiodide ion that is released when a starch-triiodide complex is hydrolysed by honey diastase. The increase of free triiodide ion concentration in a sample is found to be directly proportional to the diastase activity of the sample. A response mechanism of the platinum redox electrode is proposed, allowing a calculation of the diastase activity factor (F). The sensor and analyte parameters, including F, were obtained by least squares fitting of potentiometric data using the optimisation function of the Solver add-in of Microsoft Excel. The values of F obtained by the new direct potentiometric method were compared with those obtained using the standard Phadebas method (DN values), and the two values were found to agree within experimental error. Finally, the diastase activity of nine varieties of honey was determined using the novel method developed here.

  18. Covalent Polymers Containing Discrete Heterocyclic Anion Receptors

    PubMed Central

    Rambo, Brett M.; Silver, Eric S.; Bielawski, Christopher W.; Sessler, Jonathan L.

    2010-01-01

    This chapter covers recent advances in the development of polymeric materials containing discrete heterocyclic anion receptors, and focuses on advances in anion binding and chemosensor chemistry. The development of polymers specific for anionic species is a relatively new and flourishing area of materials chemistry. The incorporation of heterocyclic receptors capable of complexing anions through non-covalent interactions (e.g., hydrogen bonding and electrostatic interactions) provides a route to not only sensitive but also selective polymer materials. Furthermore, these systems have been utilized in the development of polymers capable of extracting anionic species from aqueous environments. These latter materials may lead to advances in water purification and treatment of diseases resulting from surplus ions. PMID:20871791

  19. Conceptual Models of the Potentiometric Surface at Yucca Mountain, NV

    NASA Astrophysics Data System (ADS)

    Hill, M.; Winterle, J.; Farrell, D.; Sims, D.; Bertetti, P.

    2002-05-01

    The U.S. Department of Energy (DOE) is evaluating Yucca Mountain (YM) Nevada, as the potential site for geologic disposal of high-level nuclear waste (HLW). If approved, the repository would be located approximately 244 to 305 m (800-1,000 ft) above the present water table. Total-system performance assessments that consider both engineered and geologic barrier systems are one method used to evaluate whether the potential repository can meet regulatory requirements. Flow paths interpreted from the potentiometric surface in the saturated zone beneath YM are incorporated into the performance assessment codes. Therefore, it is important that our understanding of the potentiometric surface is sufficient to assess potential repository performance. The addition of new water-level data from the Nye County Early Warning Drilling Program (EWDP) has helped constrain the conceptual model of the site-scale potentiometric surface at YM, specifically in the southern portion of the site along U.S. Highway 95. The EWDP was initiated in 1998, with the purpose of identifying the flow paths for contaminants should they egress from the proposed repository into the groundwater system. A revised site-scale potentiometric surface map for YM utilizing the new water-level data obtained from the EWDP is presented. The revised site-scale potentiometric surface map and other existing site-scale potentiometric surface maps interpreted from water-level data, are compared to structural, geophysical, and chemical data to evaluate whether consensus exists among the different data types concerning groundwater flow at YM. This abstract documents work performed in part by the Center for Nuclear Waste Regulatory Analyses under contract No. NRC-02-97-009. The report is an independent product and does not reflect the regulatory position of the NRC.

  20. A computer-controlled potentiometric/spectrophotometric titrator

    PubMed Central

    Stong, John D.

    1988-01-01

    A laboratory computer controlled potentiometric titrator interfaced to a diode array spectrophotometer is described. The titrator consists of widely used, commercially available components; therefore, major attention is given to modes of interconnection and software implementation in data format and system control. Replicate potentiometric titrations of glycines gave a relative standard deviation in titre of 1.035% and a relative standard deviation in pH of 0.745%. Replicate spectrophotometric titrations of bromophenol blue were analysed at three wavelengths to yield pKa= 3.898 ± 0.075 (1.9% rsd). Methods of data presentation and manipulation are presented. PMID:18925194

  1. Potentiometric stripping analysis of selected heavy metals in biological materials.

    PubMed

    Sattar, A; Ahmad, N; Khan, L A

    1993-01-01

    Different biological materials such as edible oils, refined and unrefined cane and beet sugar and tea (black and green) leaves were assayed for the heavy metals cadmium, copper, lead and zinc. The results revealed significant differences in heavy metal contents within each class of the biological materials (P < 0.05). Cadmium was not detectable in sugar samples. Among the oils, highest amounts of copper (0.263 microgram/g) and lead (0.154 microgram/g) were in corn oil and zinc in olive oil (3.01 micrograms/g) whereas cadmium exhibited a narrow range (0.023-0.033 microgram/g). The samples of beet-sugar generally contained higher levels of the heavy metals than cane-sugar. Black and green tea leaves contained 0.411-0.908 microgram Cd/g, 6.500-9.220 micrograms Cu/g, 2.200-5.238 micrograms Pb/g, and 14.500-25.180 micrograms Zn/g. PMID:8361526

  2. Fabrication of coated graphite electrode for the selective determination of europium (III) ions.

    PubMed

    Upadhyay, Anjali; Singh, Ashok Kumar; Bandi, Koteswara Rao; Jain, A K

    2013-10-15

    Preliminary complexation study showed that two ligands (ionophores) (2-((2-phenyl-2-(pyridin-2-yl)hydazono)methyl)pyridine) [L1], (2-((2-phenyl-2-(pyridin-2-yl)hydazono) methyl)phenol) [L2] can act as europium selective electrode. Europium selective coated graphite electrodes (CGE) were prepared by using ligands [L1] and [L2] and their potentiometric characteristics were determined. Membranes having different compositions of poly(vinylchloride) (PVC), the different plasticizers, anionic additives and ionophores were coated onto the graphite surface. The potential response measurements showed that the best performance was exhibited by the proposed CGE. This electrode had the widest working concentration range, Nernstian slope and fast response times of 10s. The selectivity studies showed that this electrode have higher selectivity towards Eu(3+) over a large number of cations. Furthermore, the electrode generated constant potentials in the pH range 2.7-9.0. This electrode can be used to quantify europium in soil, binary mixtures and also used as an indicator electrode in the potentiometric titration of Eu(3+) with EDTA. The proposed electrode was also successfully applied to the determination of fluoride ions in real samples.

  3. Ion-Selective Electrodes.

    ERIC Educational Resources Information Center

    Arnold, Mark A.; Meyerhoff, Mark E.

    1984-01-01

    Literature on ion-selective electrodes (ISEs) is reviewed in seven sections: books, conferences, reviews; potentiometric membrane electrodes; glass and solid-state membrane electrodes; liquid and polymer membrane ISEs; coated wire electrodes, ion-selective field effect transistors, and microelectrodes; gas sensors and selective bioelectrode…

  4. 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.

  5. Anion-selective channelrhodopsin expressed in neuronal cell culture and in vivo in murine brain: Light-induced inhibition of generation of action potentials.

    PubMed

    Dolgikh, D A; Malyshev, A Yu; Salozhin, S V; Nekrasova, O V; Petrovskaya, L E; Roshchin, M V; Borodinova, A A; Feldman, T B; Balaban, P M; Kirpichnikov, M P; Ostrovsky, M A

    2015-01-01

    Anionic channelrhodopsin slow ChloC was expressed in the culture of nerve cells and in vivo in mouse brain. We demonstrated ability of slow ChloC to suppress effectively the activity of the neuron in response to the illumination with the visible light. It has been shown for a first time that slow ChloC works equally efficiently in both neuronal culture and in the whole brain being expressed in vivo. Thus, slow ChloC could be considered as an effective optogenetic tool capable in response to light stimulation to inhibit the generation of action potentials in the neuron.

  6. 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

  7. Potentiometric sensors doped with biomolecules as a new approach to small molecule/biomolecule binding kinetics analysis.

    PubMed

    Daems, D; De Wael, K; Vissenberg, K; Van Camp, G; Nagels, L

    2014-04-15

    The most successful binding kinetics analysis systems at this moment include surface plasmon resonance (SPR), quartz microcrystal balance (QMB) and surface acoustic wave (SAW). Although these are powerful methods, they generally are complex, expensive and require the use of monolayers. Here, we report on potentiometric sensors as an inexpensive and simple alternative to do binding kinetics analysis between small molecules in solution and biomolecules (covalently) attached in a biopolymer sensor coating layer. As an example, dopamine and an anti-dopamine aptamer were used as the small molecule and the biomolecule respectively. Binding between both follows a Langmuir adsorption type model and creates a surface potential. The system operates in Flow Injection Analysis mode (FIA). Besides being an interesting new binding kinetics tool, the approach allows systematic design of potentiometric biosensors (in the present study a dopamine sensor), and gives new insights into the functioning of ion-selective electrodes (ISE's).

  8. Potentiometric Acid-Base Titrations with Activated Graphite Electrodes

    NASA Astrophysics Data System (ADS)

    Riyazuddin, P.; Devika, D.

    1997-10-01

    Dry cell graphite (DCG) electrodes activated with potassium permanganate are employed as potentiometric indicator electrodes for acid-base titrations. Special attention is given to an indicator probe comprising activated DCG-non-activiated DCG electrode couple. This combination also proves suitable for the titration of strong or weak acids.

  9. Aluminum Zintl anion moieties within sodium aluminum clusters

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Bowen, Kit H. E-mail: kiran@mcneese.edu; Schnöckel, Hansgeorg; Eichhorn, Bryan W.; Lee, Mal-Soon; Jena, P.; Kandalam, Anil K. E-mail: kiran@mcneese.edu; Kiran, Boggavarapu E-mail: kiran@mcneese.edu

    2014-02-07

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium–aluminum cluster anions, Na{sub m}Al{sub n}{sup −}, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

  10. Aluminum Zintl anion moieties within sodium aluminum clusters

    NASA Astrophysics Data System (ADS)

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Ganteför, Gerd; Schnöckel, Hansgeorg; Eichhorn, Bryan W.; Lee, Mal-Soon; Jena, P.; Kandalam, Anil K.; Kiran, Boggavarapu; Bowen, Kit H.

    2014-02-01

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, NamAln-, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

  11. Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative.

    PubMed

    Orojloo, Masoumeh; Amani, Saeid

    2016-10-01

    A new chromogenic receptor, 4-((2,4-dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino) methyl)phenol, has been designed and synthesized for quantitative and low-cost detection of various biological anions and cations. The dye was characterized by elemental analyses, infrared, UV-visible spectroscopy, and NMR spectroscopy. Upon the addition of F(-) and H2PO4(-) to the solution of chemosensor in DMSO, the dramatic naked eye detectable color changes were observed from yellow to red and orange with a limit of detection (LOD) of 1.66×10(-6)mol. L(-1) and 1.24×10(-6)mol. L(-1) at room temperature, respectively. The chemosensor showed visual changes towards cations, such as Al(3+), Cu(2+), Fe(3+), and Cr(3+), in DMSO/water (9:1). The detection limit of receptor L for the analysis of Al(3+) ion was calculated to be 3.02×10(-6)mol. L(-1). The anion recognition property of the receptor via proton transfer was monitored by UV-visible titration and (1)HNMR spectroscopy. The binding constant (Ka) and stoichiometry of the host-guest complexes formed were determined by the Benesi-Hildebrand (B-H) plot and Job's method, respectively. PMID:27474311

  12. Synthesis and studies of selective chemosensor for naked-eye detection of anions and cations based on a new Schiff-base derivative.

    PubMed

    Orojloo, Masoumeh; Amani, Saeid

    2016-10-01

    A new chromogenic receptor, 4-((2,4-dichlorophenyl)diazenyl)-2-(3-hydroxypropylimino) methyl)phenol, has been designed and synthesized for quantitative and low-cost detection of various biological anions and cations. The dye was characterized by elemental analyses, infrared, UV-visible spectroscopy, and NMR spectroscopy. Upon the addition of F(-) and H2PO4(-) to the solution of chemosensor in DMSO, the dramatic naked eye detectable color changes were observed from yellow to red and orange with a limit of detection (LOD) of 1.66×10(-6)mol. L(-1) and 1.24×10(-6)mol. L(-1) at room temperature, respectively. The chemosensor showed visual changes towards cations, such as Al(3+), Cu(2+), Fe(3+), and Cr(3+), in DMSO/water (9:1). The detection limit of receptor L for the analysis of Al(3+) ion was calculated to be 3.02×10(-6)mol. L(-1). The anion recognition property of the receptor via proton transfer was monitored by UV-visible titration and (1)HNMR spectroscopy. The binding constant (Ka) and stoichiometry of the host-guest complexes formed were determined by the Benesi-Hildebrand (B-H) plot and Job's method, respectively.

  13. Selective intercalation of Cs+ in the "V"-shaped cavity of a bichromophoric anion radical: Cs+ assisted pi-s-pi-delocalization of an electron.

    PubMed

    Stevenson, Cheryl D; Kiesewetter, Matthew K; Reiter, Richard C; Chebny, Vincent J; Rathore, Rajendra

    2006-08-10

    EPR studies in tetrahydrofuran, reveal that the one electron reduction of 1-(9-methyl-9H-fluoren-9-yl)-4-methylbenzene via electron transfer from cesium metal produces an anion radical that has a large affinity for the cesium cation. The affinity of this anion radical for Cs+ is so great that it will actually "suck" the Cs+ (but not Na+ or K+) right out of the grasp of 18-crown-6, leading to a cation-assisted pi-stacked complex, where the s-orbital of the metal cation is simultaneously overlapped with the pi-clouds of the phenyl and fluorenyl moieties. At ambient temperature, proton- and cesium-electron coupling constants are rapidly (on the EPR time scale) modulated as a result of the simultaneous existence of two interconverting conformers having an averaged cesium splitting (a(Cs)) of about 1.6 G. The pi-s-pi-electronic coupling can be turned on or off via the addition or removal of cesium cations. Analogous pi-s-pi-electronic coupling is observed in the 1,4-bis(9-methyl-9H-fluoren-9-yl)benzene-cesium system.

  14. Anion solvation in alcohols

    SciTech Connect

    Jonah, C.D.; Xujia, Zhang; Lin, Yi

    1996-03-01

    Anion solvation is measured in alcohols using pump-probe pulse radiolysis and the activation energy of solvation is determined. Solvation of an anion appears to be different than excited state solvation. The continuum dielectric model does not appear to explain the results.

  15. Formation of Self-Templated 2,6-Bis(1,2,3-triazol-4-yl)pyridine [2]Catenanes by Triazolyl Hydrogen Bonding: Selective Anion Hosts for Phosphate.

    PubMed

    Byrne, Joseph P; Blasco, Salvador; Aletti, Anna B; Hessman, Gary; Gunnlaugsson, Thorfinnur

    2016-07-25

    We report the remarkable ability of 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) compounds 2 with appended olefin amide arms to self-template the formation of interlocked [2]catenane structures 3 in up to 50 % yield when subjected to olefin ring-closing metathesis in CH2 Cl2 . X-ray diffraction crystallography enabled the structural characterization of both the [2]catenane 3 a and the non-interlocked macrocycle 4 a. These [2]catenanes showed selective triazolyl hydrogen-bonding interactions with the tetrahedral phosphate anion when screened against a range of ions; 3 a,b are the first examples of selective [2]catenane hosts for phosphate. PMID:27295556

  16. In-vitro study on the competitive binding of diflunisal and uraemic toxins to serum albumin and human plasma using a potentiometric ion-probe technique.

    PubMed

    Davilas, A; Koupparis, M; Macheras, P; Valsami, G

    2006-11-01

    The competitive binding of diflunisal and three well-known uraemic toxins (3-indoxyl sulfate, indole-3-acetic acid and hippuric acid) to bovine serum albumin (BSA), human serum albumin (HSA) and human plasma was studied by direct potentiometry. The method used the potentiometric drug ion-probe technique with a home-made ion sensor (electrode) selective to the drug anion. The site-oriented Scatchard model was used to describe the binding of diflunisal to BSA, HSA and human plasma, while the general competitive binding model was used to calculate the binding parameters of the three uraemic toxins to BSA. Diflunisal binding parameters, number of binding sites, n(i) and association constants for each class of binding site, K(i), were calculated in the absence and presence of uraemic toxins. Although diflunisal exhibits high binding affinity for site I of HSA and the three uraemic toxins bind primarily to site II, strong interaction was observed between the drug and the three toxins, which were found to affect the binding of diflunisal on its primary class of binding sites on both BSA and HSA molecules and on human plasma. These results are strong evidence that the decreased binding of diflunisal that occurs in uraemic plasma may not be solely attributed to the lower albumin concentration observed in many patients with renal failure. The uraemic toxins that accumulate in uraemic plasma may displace the drug from its specific binding sites on plasma proteins, resulting in increased free drug plasma concentration in uraemic patients. PMID:17132209

  17. Study on the effect of chain-length compatibility of mixed anionic-cationic surfactants on the cloud-point extraction of selected organophosphorus pesticides.

    PubMed

    Seebunrueng, Ketsarin; Santaladchaiyakit, Yanawath; Srijaranai, Supalax

    2012-09-01

    The chain-length compatibility of mixed anionic-cationic surfactants was investigated for the extraction of organophosphorus pesticides (OPPs). Cationic surfactants with different chain lengths (n = 12 and 16) were mixed with sodium dodecyl sulfate (SDS; n = 12) for the mixed anionic-cationic surfactants-based extraction. Six OPPs were studied including azinphos-methyl, parathion-methyl, fenitrothion, diazinon, chlorpyrifos, and prothiophos. Reversed-phase high-performance liquid chromatography was used for the determination of the studied OPPs. The extraction was performed using mixtures of SDS and cationic surfactants including dodecyltrimethyl ammonium bromide or dodecyltrimethylammonium bromide (DTAB; n = 12) and cetyltrimethyl ammonium bromide or cetyltrimethyl ammonium bromide (CTAB; n = 16). The parameters affecting the extraction efficiencies of two extraction systems were studied and discussed. The optimum condition for SDS-DTAB was 15 mmol L(-1) SDS and 1 mmol L(-1) DTAB in the presence of 15% (w/v) sodium chloride (NaCl). Meanwhile, the condition for SDS-CTAB was 10 mmol L(-1) SDS and 1.0 mmol L(-1) CTAB with 10% (w/v) NaCl. Under the optimum conditions, the extraction efficiency of SDS-DTAB (66-85%) was slightly higher than that of SDS-CTAB (61-82%). In addition, the SDS-DTAB system also gave greater enrichment factor than SDS-CTAB for all the studied OPPs. This result may be due to the compatibility of chain length between SDS and DTAB. The extraction using SDS-DTAB was successfully applied to determine OPPs in fruit samples (i.e., pomelo, apple, and pineapple). No contamination by the studied OPPs in samples was observed. Good accuracy with recoveries ranging from 77 to 105% was obtained. Low limits of detection were in the range of 0.003-0.01 mg kg(-1) which are below the MRLs established by EU-MRLs for the OPPs residues in fruit samples.

  18. Anion gap acidosis.

    PubMed

    Ishihara, K; Szerlip, H M

    1998-01-01

    Although an anion gap at less than 20 mEq/L rarely has a defined etiology, significant elevations in the anion gap almost always signify presence of an acidosis that can be easily identified. Anion gap acidoses can be divided into those caused by lactate accumulation, ketoacid production, toxin/drugs, and uremia. Lactic acidoses caused by decreased oxygen delivery or defective oxygen utilization are associated with high mortality. The treatment of lactic acidosis is controversial. The use of bicarbonate to increase pH is rarely successful and, by generating PCO2, may worsen outcome. Ketoacidosis is usually secondary to diabetes or alcohol. Treatment is aimed at turning off ketogenesis and repairing fluid and electrolyte abnormalities. Methanol, ethylene glycol, and salicylates are responsible for the majority of toxin-induced anion gap acidoses. Both methanol and ethylene glycol are associated with severe acidoses and elevated osmolar gaps. Treatment of both is alcohol infusion to decrease formation of toxic metabolites and dialyses to remove toxins. Salicylate toxicity usually is associated with a mild metabolic acidosis and a respiratory alkalosis. Uremia is associated with a mild acidosis secondary to decreased ammonia secretion and an anion gap caused by the retention of unmeasured anions. A decrease in anion gap is caused by numerous mechanisms and thus has little clinical utility.

  19. Spectrophotometric, potentiometric, and gravimetric determination of lanthanides with peri-dihydroxynaphthindenone

    SciTech Connect

    Hassan, S.S.M.; Mahmoud, W.H.

    1982-02-01

    Sensitive and reasonably selective methods are described for the spectrophotometric, potentiometric, and gravimetric determination of lanthanides using peri-dihydroxynaphthindenone as a novel chromogenic and precipitating reagent. The reagent forms a stable 1:2 (metal:reagent) type of complex with light lanthanides at pH 2-7 in 1:1 ethanol-water mixture. Low metal concentrations (<10 ..mu..g/mL) develop colored species (lambda/sub max/ 580 to 590 nm, epsilon/sub max/ (4-6) x 10/sup 4/ L mol/sup -1/ cm/sup -1/) which obey Beer's law. Quantitative precipitation of the complexes from metal solutions of concentrations > 100 ..mu..g/mL permits both gravimetric quantitation by igniting the precipitates to the metal oxides and potentiometric titration of the excess reagent. Results with an average recovery of 98% (standard deviation 0.7%) are obtainable for 0.1 ..mu..g to 200 mg of all light lanthanides. Many foreign ions naturally occurring or frequently associated with lanthanides do not interfere or can be tolerated.

  20. A biomimetic potentiometric sensor based on molecularly imprinted polymer for the determination of memantine in tablets.

    PubMed

    Arvand, Majid; Samie, Hedyeh Asadi

    2013-06-01

    Memantine hydrochloride is one of the first novel class medications for treatment of Alzheimer's disease. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer, was fabricated for the recognition and determination of memantine in pure drug and tablet pharmaceutical form. The molecularly imprinted polymer was synthesized by precipitation polymerization, using memantine hydrochloride as a template molecule, methacrylic acid as a functional monomer, and ethylene glycol dimethacrylate as a cross-linking agent. The sensor was developed by dispersing the memantine imprinted polymer particles in dibutyl sebacate plasticizer and embedding in poly(vinyl chloride) matrix. The wide linear range (10(-5) -10(-1)  M), with a near Nernstian response of 57.4 mV/decade, a limit of detection 6.0 × 10(-6)  M, fast response time (~15 s) and a satisfactory long-term stability (4 months) are characterizations of the proposed sensor. The sensor showed a high selectivity and a sensitive response to the template in aqueous system. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. It was used as indicator electrode in potentiometric determination of memantine in pharmaceutical formulations.

  1. 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

  2. Simultaneous determination of fermented milk aroma compounds by a potentiometric sensor array.

    PubMed

    Hruskar, Mirjana; Major, Nikola; Krpan, Marina; Vahcić, Nada

    2010-09-15

    The paper reports on the application of an electronic tongue for simultaneous determination of ethanol, acetaldehyde, diacetyl, lactic acid, acetic acid and citric acid content in probiotic fermented milk. The alphaAstree electronic tongue by Alpha M.O.S. was employed. The sensor array comprised of seven non-specific, cross-sensitive sensors developed especially for food analysis coupled with a reference Ag/AgCl electrode. Samples of plain, strawberry, apple-pear and forest-fruit flavored probiotic fermented milk were analyzed both by standard methods and by the potentiometric sensor array. The results obtained by these methods were used for the development of neural network models for rapid estimation of aroma compounds content in probiotic fermented milk. The highest correlation (0.967) and lowest standard deviation of error for the training (0.585), selection (0.503) and testing (0.571) subset was obtained for the estimation of ethanol content. The lowest correlation (0.669) was obtained for the estimation of acetaldehyde content. The model exhibited poor performance in average error and standard deviations of errors in all subsets which could be explained by low sensitivity of the sensor array to the compound. The obtained results indicate that the potentiometric electronic tongue coupled with artificial neural networks can be applied as a rapid method for the determination of aroma compounds in probiotic fermented milk.

  3. Potentiometric electronic tongue-flow injection analysis system for the monitoring of heavy metal biosorption processes.

    PubMed

    Wilson, D; del Valle, M; Alegret, S; Valderrama, C; Florido, A

    2012-05-15

    An automated flow injection potentiometric (FIP) system with electronic tongue detection (ET) is used for the monitoring of biosorption processes of heavy metals on vegetable wastes. Grape stalk wastes are used as biosorbent to remove Cu(2+) ions in a fixed-bed column configuration. The ET is formed by a 5-sensor array with Cu(2+) and Ca(2+)-selective electrodes and electrodes with generic response to heavy-metals, plus an artificial neural network response model of the sensor's cross-response. The real-time monitoring of both the Cu(2+) and the cation exchanged and released (Ca(2+)) in the effluent solution is performed by using flow-injection potentiometric electronic tongue system. The coupling of the electronic tongue with automation features of the flow-injection system allows us to accurately characterize the Cu(2+) ion-biosorption process, through obtaining its breakthrough curves, and the profile of the Ca(2+) ion release. In parallel, fractions of the extract solution are analysed by spectroscopic techniques in order to validate the results obtained with the reported methodology. The sorption performance of grape stalks is also evaluated by means of well-established sorption models.

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

    NASA Astrophysics Data System (ADS)

    Saefurohman, Asep; Buchari, Noviandri, Indra; Syoni

    2014-03-01

    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 report 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-1, 1031 cm-1 and 794.7 cm-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-1 indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R3P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10-3 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 10-5 and 10-1 M.

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

    SciTech Connect

    Saefurohman, Asep Buchari, Noviandri, Indra; Syoni

    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 report 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.

  6. Comparison of a miniaturized shake-flask solubility method with automated potentiometric acid/base titrations and calculated solubilities.

    PubMed

    Glomme, A; März, J; Dressman, J B

    2005-01-01

    Solubility is one of the most important parameters for lead selection and optimization during drug discovery. Its determination should therefore take place as early as possible in the process. Because of the large numbers of compounds involved and the very low amounts of each compound available in the early development stage, it is highly desirable to measure the solubility with as little compound as possible and to be able to improve the throughput of the methods used. In this work, a miniaturized shake-flask method was developed and the solubility results were compared with those measured by semiautomated potentiometric acid/base titrations and computational methods for 21 poorly soluble compounds with solubilities mostly in the range 0.03-30 microg/mL. The potentiometric method is very economical (approximately 100 microg of a poorly soluble compound is needed) and is able to create a pH/solubility profile with one single determination, but is limited to ionizable compounds. The miniaturized shake-flask method can be used for all compounds and a wide variety of media. Its precision and throughput proved superior to the potentiometric method for very poorly soluble compounds. Up to 20 compounds a week can be studied with one set-up. Calculated solubility data seem to be sufficient for a first estimate of the solubility, but they cannot currently be used as a substitute for experimental measurements at key decision points in the development process.

  7. A Cyanuric Acid Platform Based Tripodal Bis-heteroleptic Ru(II) Complex of Click Generated Ligand for Selective Sensing of Phosphates via C-H···Anion Interaction.

    PubMed

    Chowdhury, Bijit; Dutta, Ranjan; Khatua, Snehadrinarayan; Ghosh, Pradyut

    2016-01-01

    A new bis-heteroleptic trinuclear Ru(II) complex (1[PF6]6) has been synthesized from electron deficient cyanuric acid platform based copper-catalyzed azide-alkyne cycloaddition, i.e., CuAAC click generated ligand, 1,3,5-tris [(2-aminoethyl-1H-1,2,3-triazol-4-yl)-pyridine]-1,3,5-triazinane-2,4,6-trione (L1). Complex 1[PF6]6 displays weak luminescence (ϕf = 0.002) at room temperature with a short lifetime of ∼5 ns in acetonitrile. It shows selective sensing of hydrogen pyrophosphate (HP2O7(3-)) through 20-fold enhanced emission intensity (ϕf = 0.039) with a 15 nm red shift in emission maxima even in the presence of a large excess of various competitive anions like F(-), Cl(-), AcO(-), BzO(-), NO3(-), HCO3(-), HSO4(-), HO(-), and H2PO4(-) in acetonitrile. Selective change in the decay profile as well as in the lifetime of 1[PF6]6 in the presence of HP2O7(3-) (108 ns) further supports its selectivity toward HP2O7(3-). UV-vis and photoluminescence titration profiles and corresponding Job's plot analyses suggest 1:3 host-guest stoichiometric binding between 1[PF6]6 and HP2O7(3-). High emission enhancement of 1[PF6]6 in the presence of HP2O7(3-) has resulted in the detection limit of the anion being as low as 0.02 μM. However, 1[PF6]6 shows selectivity toward higher analogues of phosphates (e.g., ATP, ADP, and AMP) over HP2O7(3-)/H2PO4(-) in 10% Tris HCl buffer (10 mM)/acetonitrile medium. Downfield shifting of the triazole C-H in a (1)H NMR titration study confirms that the binding of HP2O7(3-)/H2PO4(-) is occurring via C-H···anion interaction. The single crystal X-ray structure of complex 1 having NO3(-) counteranion, 1[NO3]6 shows binding of NO3(-) with complex 1 via C-H···NO3(-) interactions. PMID:26653882

  8. Direct potentiometric quantification of histamine using solid-phase imprinted nanoparticles as recognition elements.

    PubMed

    Basozabal, Itsaso; Guerreiro, Antonio; Gomez-Caballero, Alberto; Aranzazu Goicolea, M; Barrio, Ramón J

    2014-08-15

    A new potentiometric sensor based on molecularly imprinted nanoparticles produced via the solid-phase imprinting method was developed. For histamine quantification, the nanoparticles were incorporated within a membrane, which was then used to fabricate an ion-selective electrode. The use of nanoparticles with high affinity and specificity allowed for label-free detection/quantification of histamine in real samples with short response times. The sensor could selectively quantify histamine in presence of other biogenic amines in real wine and fish matrices. The limit of detection achieved was 1.12×10(-6)molL(-1), with a linear range between 10(-6) and 10(-2)molL(-1) and a response time below 20s, making the sensor as developed a promising tool for direct quantification of histamine in the food industry.

  9. Intrinsic anion oxidation potentials.

    PubMed

    Johansson, Patrik

    2006-11-01

    Anions of lithium battery salts have been investigated by electronic structure calculations with the objective to find a computational measure to correlate with the observed (in)stability of nonaqueous lithium battery electrolytes vs oxidation often encountered in practice. Accurate prediction of intrinsic anion oxidation potentials is here made possible by computing the vertical free energy difference between anion and neutral radical (Delta Gv) and further strengthened by an empirical correction using only the anion volume as a parameter. The 6-311+G(2df,p) basis set, the VSXC functional, and the C-PCM SCRF algorithm were used. The Delta Gv calculations can be performed using any standard computational chemistry software. PMID:17078600

  10. Anion exchange polymer electrolytes

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

    Anion exchange polymer electrolytes that include guanidinium functionalized polymers may be used as membranes and binders for electrocatalysts in preparation of anodes for electrochemical cells such as solid alkaline fuel cells.

  11. Microtitration of various anions with quaternary ammonium halides using solid-state electrodes

    SciTech Connect

    Selig, W.

    1980-01-01

    Many solid-state electrodes were found to respond as endpoint detectors in the potentiometric titration of large inorganic and organic anions with quaternary ammonium halides. The best response was obtained with the iodide and cyanide electrodes although practically any electrode can function as endpoint sensor. The titrants were hexadecylpyridinium chloride and hexadecyltrimethylammonium chloride; hexadecyltrimethylammonium bromide and Hyamine 1622 may also be used. Some inorganic anions thus titratable are perrhenate, persulfate, ferricyanide, hexafluorophosphate, and hexachloroplatinate. Examples of organic anions titratable are nitroform, tetraphenylborate, cyanotriphenylborate, picrate, long-chain sulfates and sulfonates, and some soaps. The reverse titration of quaternary ammonium halides vs dodecylsulfate is also feasible. Some titrations are feasible in a partially nonaqueous medium.

  12. 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.

  13. Probing and evaluating anion-π interaction in meso-dinitrophenyl functionalized calix[4]pyrrole isomers.

    PubMed

    Kim, Ajeong; Ali, Rashid; Park, Seok Ho; Kim, Yong-Hoon; Park, Jung Su

    2016-09-25

    We investigate anion-π binding modes in a cis-isomer of 3,5-dinitrophenyl-substituted calix[4]pyrrole with various anions via X-ray crystallographic analyses and compare its binding affinities with those of the corresponding trans-isomer. Sandwich-type anion-π interactions prove to not only enhancing anion binding abilities but also altering the anion-binding selectivity of the calix[4]pyrrole framework. PMID:27549578

  14. Redox potential of shallow groundwater by 1-month continuous in situ potentiometric measurements

    NASA Astrophysics Data System (ADS)

    Ioka, Seiichiro; Muraoka, Hirofumi; Suzuki, Yota

    2016-06-01

    One-month continuous in situ potentiometric measurements of redox potential (Eh) were used to investigate the dominant redox processes in the shallow groundwater (i.e., <10 m) of a Holocene aquifer, Aomori City, northern Japan. The Eh values, which were determined using a platinum electrode, were -163, -169 and -173 mV, respectively, for three monitoring campaigns. The temperatures and pH values of shallow groundwater during all three periods were approximately 12 °C and 6.6, respectively. Dissolved oxygen and sulfide ion concentrations were not detected. Chemical analyses showed that the shallow groundwater is Na-Fe-HCO3 type, and contains over 40 mg/L of Fe (the dominant cation) and over 200 mg/L of HCO3 - (the dominant anion). A good fit was found between measured Eh values and Eh values calculated using thermodynamic data of fine-grained goethite. This suggests that Fe redox system is related to the Eh values of shallow groundwater in the Aomori City aquifer.

  15. Direct potentiometric determination of starch using a platinum redox sensor.

    PubMed

    Sakač, Nikola; Sak-Bosnar, Milan; Horvat, Marija

    2013-05-01

    Here, we describe the development of a platinum redox sensor for the direct potentiometric quantification of starch in solution. The sensor measures the decrease in free triiodide ion after it complexes with starch to form a starch-triiodide complex. This decrease was, therefore, correlated with starch concentration, and the composition and stability of the potassium triiodide solution were optimised. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. We also propose a response mechanism for the platinum redox sensor towards starch and an appropriate theoretical model. The optimised method exhibited satisfactory accuracy and precision and was in good agreement with a standard spectrophotometric method. The sensor was tested over a range of 0.4-9 mg starch, with recoveries ranging from 97.8% to 103.4% and a detection limit of 0.01 mg starch.

  16. Evidence for anionic cation transport of lithium, sodium and potassium across the human erythrocyte membrane induced by divalent anions.

    PubMed Central

    Becker, B F; Duhm, J

    1978-01-01

    1. The passive net transport of Li+ and Na+ across the human red cell membrane was accelerated by the divalent anions carbonate, sulphite, oxalate, phosphite and malonate. Phthalate, maleate, sulphate and succinate were found additionally to stimulate downhill transport of K+. Marked differences in anion efficacy and selectivity were observed. 2. The effects of these 'carbonate type' anions were reversible and fully blocked by SITS, dipyridamole and other inhibitors of anion transfer. 3. Cation transport acceleration induced by the monovalent anions salicylate, benzoate, thiocyanate and 2,4-dinitrophenol were inhibited by dipyridamole, but not affected by SITS. A great number of mono- and polyvalent anions were without detectable influence on Li+ transport. 4. Li+ net uptake induced by oxalate exhibited a pH dependence similar to that reported for halide self exchange. 5. Transport acceleration by carbonate type anions displayed a linear, 1:1 dependence on the concentrations of both the anion and the cation and was symmetric with respect to the two sides of the membrane. 6. It is concluded that the divalent carbonate type anions form singly charged, negative 1:1 ion pairs with the respective alkali metal cations, the ion pairs traversing the red cell membrane via the anion exchange pathway. This concept of anionic formation of some of the ion pairs considered. The relative efficacies and cation selectivities of polyvalent anions can largely be explained on the basis of electrostatic interactions governing ion pair formation. However, the chelating properties, structural flexibility, polarizability of the anions and the accessibility of the ion pairs to the anion exchange pathway need also be considered. 7. An exchange of NaCO-3 ion pairs for internal HCO-3 or Cl- is discussed as a possible mode of cellular pH regulation. PMID:31458

  17. 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.

  18. Porous silicon as a substrate material for potentiometric biosensors

    NASA Astrophysics Data System (ADS)

    Thust, Marion; Schöning, M. J.; Frohnhoff, S.; Arens-Fischer, R.; Kordos, P.; Lüth, H.

    1996-01-01

    For the first time porous silicon has been investigated for the purpose of application as a substrate material for potentiometric biosensors operating in aqueous solutions. Porous silicon was prepared from differently doped silicon substrates by a standard anodic etching process. After oxidation, penicillinase, an enzyme sensitive to penicillin, was bound to the porous structure by physical adsorption. To characterize the electrochemical properties of the so build up penicillin biosensor, capacitance - voltage (C - V) measurements were performed on these field-effect structures.

  19. Potentiometric map of the Cockfield Aquifer in Mississippi, fall 1984

    USGS Publications Warehouse

    Darden, Daphne

    1986-01-01

    This map, the second in a series for the Cockfield aquifer in Mississippi, follows a map that delineated the 1980 potentiometric surface of the aquifer. This water level map is based on water level measurements made in about 80 wells in the Cockfield aquifer in the fall of 1984. The contours show altitudes at which water levels would have stood in tightly cased unpumped wells in fall 1984. (Lantz-PTT)

  20. 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.

  1. 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.

  2. Novel lipoate-selective membrane sensor for the flow injection determination of alpha-lipoic acid in pharmaceutical preparations and urine.

    PubMed

    Abbas, M N; Radwan, A A

    2008-02-15

    A potentiometric lipoate-selective sensor based on mercuric lipoate ion-pair as a membrane carrier is reported. The electrode was prepared by coating the membrane solution containing PVC, plasticizer, and carrier on the surface of graphite electrode. Influences of the membrane composition, pH, and possible interfering anions were investigated on the response properties of the electrode. The sensor exhibits significantly enhanced response toward lipoate ions over the concentration range 1 x 10(-7) molL(-1) to 1 x 10(-2) molL(-1) with a lower detection limit of (LDL) of 9 x 10(-8) molL(-1) and a slope of -29.4 m V decade(-1), with S.D. of the slope is 0.214 mV. Fast and stable response, good reproducibility, long-term stability, applicability over a pH range of 8.0-9.5 is demonstrated. The sensor has a response time of anions. The CGE was used in flow injection potentiometry (FIP) and resulted in well defined peaks for lipoate ions with stable baseline, excellent reproducibility and reasonable sampling rate of 30 injections per hour. The proposed sensor has been applied for the direct and FI potentiometric determination of LA in pharmaceutical preparations and urine; and has been also utilized as an indicator electrode for the potentiometric titration of LA.

  3. Ion-selective electrodes based on molecular tweezer-type neutral carriers.

    PubMed

    Shim, Jun Ho; Jeong, In Seok; Lee, Min Hyung; Hong, Hun Pyo; On, Jeung Hoon; Kim, Ki Soo; Kim, Hong-Seok; Kim, Byeong Hyo; Cha, Geun Sig; Nam, Hakhyun

    2004-05-10

    Potentiometric properties of cholic and deoxycholic acid derivatives substituted with various ion-recognizing moieties, such as dithiocarbamate, bipyridyl, glycolic and malonic diamides, urea and thiourea, and trifluoroacetophenons (TFAP), have been studied using solvent polymeric membranes. The dithiocarbamate and bipyridyl group containing ionophores exhibit high silver ion selectivity. The cholic acid derivatized with glycolic diamides exhibited high calcium selectivity, but its complex formulation constant was 10(5) times smaller than that of ETH 1001. The reduced calcium binding ability of the glycolic diamide-substituted ionophore was advantageous for eliminating anionic interference. The bi- or tripodal malonic diamide-substituted ionophores exhibited substantially increased magnesium selectivity. Anion-selective ionophores have been designed by substituting urea and thiourea group containing chains to the hydroxyl linkers of chenodeoxycholic acid frames; their selectivity closely followed the sequence of Hoffmeister series, except the unusually large response of the thiourea-substituted ionophore to sulfate. The most successful examples of cholic or deoxycholic acid frame-based ionophores are those functionalized with two carbonate-selective TFAP groups: bipodal TFAP groups behaves like a tweezers for the incoming carbonate, and exhibit analytically interference free and quantitative responses to the carbonate in serum and seawater samples. PMID:18969404

  4. Potentiometric surface of the Ozark Aquifer in northern Arkansas, 1995

    USGS Publications Warehouse

    Pugh, Aaron L.

    1998-01-01

    The Ozark aquifer in northern Arkansas is comprised of dolostones, 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 diffuse flow components with large spatial variations in porosity and permeability. 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. Within Arkansas, the potentiometric-surface map based on October- December 1995 data indicates maximum water-level altitudes of greater than 1,300 feet in Boone, Carroll, and Madison Counties and minimum water-level altitudes of less than 400 feet in Independence, Izard, Lawrence, Randolph, Sharp, and Stone Counties. Comparing the 1995 potentiometric-surface map with a predevelopment potentiometric- surface map (Imes, 199), indicates general agreement between the two surfaces except in parts of Benton and Sharp Counties. Water-level differences could be attributed to differences in the time of year in which the water-level data were collected, differences in pumping conditions just prior to water-level measurement, differences in interpretation resulting (in part) from greater number of water-level measurements used for this report than for Imes (1990), or erroneous water-level data.

  5. Preliminary potentiometric map and flow dynamic characteristics for the upper-basalt confined aquifer system

    SciTech Connect

    Spane, F.A. Jr.; Raymond, R.G.

    1993-09-01

    This report presents the first comprehensive Hanford Site-wide potentiometric map for the upper-basalt confined aquifer system (i.e., the upper Saddle Mountains Basalt). In constructing the potentiometric map, over forty on-site and off-site monitoring wells and boreholes were used. The potentiometric map developed for the upper-basalt confined aquifer is consistent with the areal head pattern indicated for the Mabton interbed, which is a deeper and more areally extensive confined aquifer underlying the Hanford Site. Salient features for the upper-basalt confined aquifer system potentiometric map are described.

  6. Structural Design Criteria for Anion Hosts: Strategies for Achieving Anion Shape Recognition through the Complementary Placement of Urea Donor Groups

    SciTech Connect

    Hay, Benjamin P.; Firman, Timothy K.; Moyer, Bruce A.

    2005-02-16

    The arrangement of urea ligands about different shaped anions has been evaluated with electronic structure calculations. Geometries and binding energies are reported for urea complexes with Cl{sup -}, NO{sub 3}{sup -}, and ClO{sub 4}{sup -}. The results yield new insight into the nature of urea-anion interactions and provide structural criteria for the deliberate design of anion selective receptors containing two or more urea donor groups.

  7. Anion-π catalysis.

    PubMed

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-01

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  8. Anion-π catalysis.

    PubMed

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-01

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  9. 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.

  10. 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.

  11. Potentiometric measurement of ascorbate by using a solvent polymeric membrane electrode.

    PubMed

    Guo, Huimin; Yin, Tanji; Su, Qingmei; Qin, Wei

    2008-05-15

    A novel potentiometric method for the determination of ascorbate is described in this communication. It is based on ascorbate oxidation with permanganate which is continuously released from the inner reference solution of a ligand-free tridodecylmethylammonium chloride (TDMAC)-based polymeric membrane ion selective electrode (ISE). The ISE potential determined by the activity of permanganate ions released at the sample-membrane phase boundary is increased with the consumption of permanganate. The proposed membrane electrode is useful for continuous and reversible detection of ascorbate at concentrations in 0.1M NaCl ranging from 1.0 x 10(-6) to 1.0 x 10(-3)M with a detection limit of 2.2 x 10(-7)M.

  12. Potentiometric sensor fabrication having 2D sarcosine memories and analytical features.

    PubMed

    Özkütük, Ebru Birlik; Diltemiz, Sibel Emir; Avcı, Şeyma; Uğurağ, Deniz; Aykanat, Rabia Berna; Ersöz, Arzu; Say, Rıdvan

    2016-12-01

    In this study, a simple, rapid and sensitive method based on novel molecular imprinted polymeric sensor has been developed and validated for the determination of prostate cancer metabolite biomarker. The molecularly imprinted polymer (MIP) has been synthesized by emulsion polymerization, using sarcosine as template molecule, methacryloylamido histidine (MAH) as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The performance of the developed sarcosine sensor has been evaluated, and the results have indicated that a sensitive potentiometric sensor has been fabricated. The sarcosine sensor has showed high-selectivity, shorter response time (<2min), wider linear range (10(-2)-10(-6)mM), lower detection limit (1.35×10(-7)mM), and satisfactory long-term stability (>5.5months). PMID:27612708

  13. 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.

  14. A New Composition for Co(II)-porphyrin-based Membranes Used in Thiocyanate-selective Electrodes

    PubMed Central

    Vlascici, Dana; Fagadar-Cosma, Eugenia; Bizerea-Spiridon, Otilia

    2006-01-01

    In the present paper, the potentiometric response characteristics of a metalloporphyrin-based electrode in o-nitrophenyloctylether (o-NPOE) plasticized polyvinyl chloride (PVC) membrane are presented for a set of monovalent anions. As membrane ionophore, 5,10,15,20-tetrakis-(4-methoxyphenyl)-porphyrin-Co(II) (CoTMeOPP) was used. To establish the optimum composition of the membrane, different molar percents of cationic derivative (mol.% relative to ionophore) were used. Electrodes formulated with membranes containing 1 wt.% ionophore, 66 wt.% o-NPOE, 33 wt.% PVC (plasticizer: PVC = 2:1) and the lipophilic cationic derivative (35 mol%) are shown to exhibit high selectivity for thiocyanate with a near-Nernstian slope in the working concentration range of 1.0×10−1–1.0×10−5 M, with a good stability in time.

  15. Cesium cation templated selective synthesis of a "cone-shaped" sugar macrotricyclic cryptand: A dual anion-cation molecular recognition of potassium tartrate.

    PubMed

    Porwanski, S; Moretti, F; Dumarcay-Charbonnier, F; Marsura, A

    2016-05-01

    Cesium templated Staudinger-aza-Wittig tandem reaction (S.A.W.) has been used in the synthesis of a bis-diazacrown-bis-cellobiosyl-tetra-ureido cryptand. A novel macrotricyclic compound having a "cone-shaped" configuration was selectively obtained. Additionally, first results on potential recognition properties of the cryptand are also given. PMID:26826794

  16. Cesium cation templated selective synthesis of a "cone-shaped" sugar macrotricyclic cryptand: A dual anion-cation molecular recognition of potassium tartrate.

    PubMed

    Porwanski, S; Moretti, F; Dumarcay-Charbonnier, F; Marsura, A

    2016-05-01

    Cesium templated Staudinger-aza-Wittig tandem reaction (S.A.W.) has been used in the synthesis of a bis-diazacrown-bis-cellobiosyl-tetra-ureido cryptand. A novel macrotricyclic compound having a "cone-shaped" configuration was selectively obtained. Additionally, first results on potential recognition properties of the cryptand are also given.

  17. 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

    semivariograms decreased markedly between 2002 and 2003, timing that coincided with decreases in well-field pumping. Cross-validation results suggest that the kriging interpolation may smooth over the drawdown of the potentiometric surface near production wells. The groundwater monitoring network of 197 wells yielded an average kriging error in the potentiometric-surface elevations of 2 feet or less over approximately 70 percent of the map area. Additional data collection within the existing monitoring network of 260 wells and near selected well fields could reduce the error in individual months. Reducing the kriging error in other areas would require adding new monitoring wells. Potentiometric-surface elevations fluctuated by as much as 30 feet over the study period, and the spatially averaged elevation for the entire surface rose by about 2 feet over the decade. Monthly potentiometric-surface elevations describe the lateral groundwater flow patterns in the aquifer and are usable at a variety of spatial scales to describe vertical groundwater recharge and discharge conditions for overlying surface-water features.

  18. Polymeric membrane electrodes with high nitrite selectivity based on rhodium(III) porphyrins and salophens as ionophores.

    PubMed

    Pietrzak, Mariusz; Meyerhoff, Mark E

    2009-05-01

    Several porphyrin and salophen complexes with Rh(III) are examined as ionophores to prepare nitrite selective polymeric membrane electrodes. All ionophores tested exhibit preferred selectivity toward nitrite anion. Enhanced potentiometric nitrite selectivity is observed in the presence of either lipophilic anionic as well as cationic sites within the membranes, suggesting that the ionophores can function via either a charged or a neutral carrier response mechanism. Among a range of complexes and membrane formulations examined, optimal nitrite selectivity and reversible response down to 5 x 10(-6) M is achieved using Rh(III)-tetra(t-butylphenylporphyrin) as the ionophore in the presence of lipophilic cationic sites in plasticized poly(vinyl chloride) membrane. Response times are substantially longer than typical membrane electrodes apparently because of a slow nitrite ligation reaction with Rh(III); however, a significant improvement in dynamic EMF response can be realized by optimizing the membrane formulation and increasing the temperature. The selectivity observed with these membranes is greater than the best nitrite selective electrodes reported to date in the literature based on lipophilic Co(III)-corrin complexes, allowing the new nitrite electrodes to be utilized to determine the level of nitrite in meats with good correlation to the colorimetric Griess assay method.

  19. Electron anions and the glass transition temperature.

    PubMed

    Johnson, Lewis E; Sushko, Peter V; Tomota, Yudai; Hosono, Hideo

    2016-09-01

    Properties of glasses are typically controlled by judicious selection of the glass-forming and glass-modifying constituents. Through an experimental and computational study of the crystalline, molten, and amorphous [Ca12Al14O32](2+) ⋅ (e(-))2, we demonstrate that electron anions in this system behave as glass modifiers that strongly affect solidification dynamics, the glass transition temperature, and spectroscopic properties of the resultant amorphous material. The concentration of such electron anions is a consequential control parameter: It invokes materials evolution pathways and properties not available in conventional glasses, which opens a unique avenue in rational materials design. PMID:27559083

  20. Potentiometric surface of the Lloyd aquifer on Long Island, New York, in January 1975

    USGS Publications Warehouse

    Rich, Charles A.; Prince, Keith R.; Spinello, Anthony G.

    1975-01-01

    A map showing the potentiometric surface of the Lloyd aquifer was drawn from water-level measurements made in January 1975. Altitude of the potentiometric surface ranged from more than 20 feet below mean sea level in Queens County to more than 40 feet above mean sea level in Suffolk County.

  1. Solid state potentiometric gaseous oxide sensor

    NASA Technical Reports Server (NTRS)

    Wachsman, Eric D. (Inventor); Azad, Abdul Majeed (Inventor)

    2003-01-01

    A solid state electrochemical cell (10a) for measuring the concentration of a component of a gas mixture (12) includes first semiconductor electrode (14) and second semiconductor electrode (16) formed from first and second semiconductor materials, respectively. The materials are selected so as to undergo a change in resistivity upon contacting a gas component, such as CO or NO. An electrolyte (18) is provided in contact with the first and second semiconductor electrodes. A reference cell can be included in contact with the electrolyte. Preferably, a voltage response of the first semiconductor electrode is opposite in slope direction to that of the second semiconductor electrode to produce a voltage response equal to the sum of the absolute values of the control system uses measured pollutant concentrations to direct adjustment of engine combustion conditions.

  2. The use of graphite electrodes in potentiometric titrations

    SciTech Connect

    Selig, W.S.

    1987-04-01

    The use of various types of graphite as indicator electrodes in potentiometry has been limited to acid-base and redox titrations. We have expanded the range of feasible titrations to: (1) precipitation titrations; (2) acid-base titrations; (3) compleximetric titrations; and (4) redox titrations. Graphite covered with an organic membrane containing poly(vinyl chloride) (PVC) and a plasticizer is particularly useful in monitoring the endpoints of titrations in which insoluble ion-pairs are formed. The potentiometric titration of fluoride vs La(III) or Th(IV), or of sulfate vs Pb (II) or Ba(II), which can be monitored with a plain carbon rod, is discussed.

  3. 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.

  4. 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. PMID:22154105

  5. Polymeric Membrane Electrodes with High Nitrite Selectivity Based on Rhodium(III) Porphyrins and Salophens as Ionophores

    PubMed Central

    Pietrzak, Mariusz; Meyerhoff, Mark E.

    2009-01-01

    Several porphyrin and salophen complexes with Rh(III) are examined as ionophores to prepare nitrite selective polymeric membrane electrodes. All ionophores tested exhibit preferred selectivity towards nitrite anion. Enhanced potentiometric nitrite selectivity is observed in the presence of either lipophilic anionic as well as cationic sites within the membranes, suggesting that the ionophores can function via either a charged or neutral carrier response mechanism. Among a range of complexes and membrane formulations examined, optimal nitrite selectivity and reversible response down to 5 × 10−6 M is achieved using Rh(III)-tetra(t-butyl-phenylporphyrin) as the ionophore in the presence of lipophilic cationic sites in plasticized PVC membrane. Response times are substantially longer than typical membrane electrodes apparently due to slow nitrite ligation reaction however, a significant improvement in dynamic EMF response can be realized by optimizing the membrane formulation and increasing temperature. The selecitivity observed with these membranes is greater than the best nitrite selective electrodes reported to the date in the literature based on lipophilic Co(III)-corrin complexes, allowing the new nitrite electrodes to be utilized to determine the level of nitrite in meats with good correlation to the colorimetric Griess assay method. PMID:19402723

  6. Hydrated hydride anion clusters

    NASA Astrophysics Data System (ADS)

    Lee, Han Myoung; Kim, Dongwook; Singh, N. Jiten; Kołaski, Maciej; Kim, Kwang S.

    2007-10-01

    On the basis of density functional theory (DFT) and high level ab initio theory, we report the structures, binding energies, thermodynamic quantities, IR spectra, and electronic properties of the hydride anion hydrated by up to six water molecules. Ground state DFT molecular dynamics simulations (based on the Born-Oppenheimer potential surface) show that as the temperature increases, the surface-bound hydride anion changes to the internally bound structure. Car-Parrinello molecular dynamics simulations are also carried out for the spectral analysis of the monohydrated hydride. Excited-state ab initio molecular dynamics simulations show that the photoinduced charge-transfer-to-solvent phenomena are accompanied by the formation of the excess electron-water clusters and the detachment of the H radical from the clusters. The dynamics of the detachment process of a hydrogen radical upon the excitation is discussed.

  7. Improving the limits of detection in potentiometric sensors

    NASA Astrophysics Data System (ADS)

    van der Bent, J. F.; Puik, E. C. N.; Tong, H. D.; van Rijn, C. J. M.

    2015-12-01

    Potentiometric sensors will generally suffer from unwanted responses as a result to changing temperatures by generating an electromotive force. Typically, this voltage drift has a non-linear character and therefore it is difficult to compensate using linear algorithms implemented in the analogue domain. A solution is proposed to improve the sensor characteristics by combining the digitized output of two CO2 rubidium silver iodide sensors with a specially designed digital algorithm to improve the limits of detection (LOD). Experiments show that this method has the capability to improve the LOD of the sensor with a factor 4.5x during temperature variations of 22 °C over a measurement period of 22 h. It enables potentiometric sensors to be used in low power wireless sensor networks for long term air quality control. Furthermore, the influence of depletion of the rubidium silver iodide electrolyte layer can be effectively compensated by determining the decay of the active layer according to the Nernst equation. Knowing the function of depletion over time helps to correct the sensor output and thereby improves the accuracy of the sensor.

  8. 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.

  9. Surface characterization of hydroxyapatite: potentiometric titrations coupled with solubility measurements.

    PubMed

    Skartsila, Kyriaki; Spanos, Nikos

    2007-04-15

    The acid-base properties of synthetically prepared and well-characterized hydroxyapatite (HAP) in contact with KNO3 solutions were investigated at 25 degrees C, through potentiometric titrations, zeta-potential measurements, and surface complex modeling. Aliquots of suspension were withdrawn every 0.5 pH unit during the titration procedure and analyzed for calcium and phosphate. It was found that, even for rapid titration experiments, a remarkable amount of H+ ions (H+dissol.) is consumed in the bulk solution in reacting with species coming from the dissolution of HAP. These H+ ions must be taken into account in the H+ mass balance, in order for true value for the point of zero charge (pzc=6.5+/-0.2) and consequently true value for the surface charge (sigma0) to be obtained. Besides the conventional potentiometric titration technique, it was found that pzc may be determined much more easily as the intersection point of the suspension titration curve and the blank one modified to include the amount of H+dissol. obtained at one ionic strength. Finally, a surface complexation model was proposed for the development of surface charge. Experimental data were satisfactorily fitted by using the value of 4.2 F m-2 for the capacitance.

  10. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

    1984-01-01

    Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

  11. Anion permselective membrane

    NASA Astrophysics Data System (ADS)

    Hodgdon, R. B.; Waite, W. A.; Alexander, S. S.

    1984-07-01

    Two polymer ion exchange membranes were synthesized to fulfill the needs of both electrical resistivity and anolyte/catholyte separation for utility load leveling utilizing the DOE/NASA mixed electrolyte REDOX battery. Both membranes were shown to meet mixed electrolyte utility load leveling criteria. Several modifications of an anion exchange membrane failed to meet utility load leveling REDOX battery criteria using the unmixed electrolyte REDOX cell.

  12. Solid-contact potentiometric aptasensor based on aptamer functionalized carbon nanotubes for the direct determination of proteins.

    PubMed

    Düzgün, Ali; Maroto, Alicia; Mairal, Teresa; O'Sullivan, Ciara; Rius, F Xavier

    2010-05-01

    A facile, solid-contact selective potentiometric aptasensor exploiting a network of single-walled carbon nanotubes (SWCNT) acting as a transducing element is described in this work. The molecular properties of the SWCNT surface have been modified by covalently linking aptamers as biorecognition elements to the carboxylic groups of the SWCNT walls. As a model system to demonstrate the generic application of the approach, a 15-mer thrombin aptamer interacts with thrombin and the affinity interaction gives rise to a direct potentiometric signal that can be easily recorded within 15 s. The dynamic linear range, with a sensitivity of 8.0 mV/log a(Thr) corresponds to the 10(-7)-10(-6) M range of thrombin concentrations, with a limit of detection of 80 nM. The aptasensor displays selectivity against elastase and bovine serum albumin and is easily regenerated by immersion in 2 M NaCl. The aptasensor demonstrates the capacity of direct detection of the recognition event avoiding the use of labels, mediators, or the addition of further reagents or analyte accumulation. PMID:20419254

  13. Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties

    USGS Publications Warehouse

    Boyer, T.H.; Singer, P.C.; Aiken, G.R.

    2008-01-01

    Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized asterrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM. ?? 2008 American Chemical Society.

  14. 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.

  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. PMID:25910442

  16. 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

  17. Construction and performance characteristics of polymeric membrane electrode and coated graphite electrode for the selective determination of Fe³⁺ ion.

    PubMed

    Bandi, Koteswara Rao; Singh, Ashok K; Upadhyay, Anjali

    2014-03-01

    Novel Fe(3+) ion-selective polymeric membrane electrodes (PMEs) were prepared using three different ionophores N-(4-(dimethylamino)benzylidene)thiazol-2-amine [L1], 5-((3-methylthiophene-2yl) methyleneamino)-1,3,4-thiadiazole-2-thiol [L2] and N-((3-methylthiophene-2yl)methylene)thiazol-2-amine [L3] and their potentiometric characteristics were discussed. Effect of various plasticizers and anion excluders was also studied in detail and improved performance was observed. The best performance was obtained for the membrane electrode having a composition of L2:PVC:o-NPOE:NaTPB as 3:38.5:56:2.5 (w/w; mg). A coated graphite electrode (CGE) was also prepared with the same composition and compared. CGE is found to perform better as it shows a wider working concentration range of 8.3×10(-8)-1.0×10(-1)molL(-1), a lower detection limit of 2.3×10(-8)molL(-1), and a near Nernstian slope of 19.5 ± 0.4 mVdecade(-1) of activity with a response time of 10s. The CGE shows a shelf life of 6 weeks and in view of high selectivity, it can be used to quantify Fe(3+) ion in water, soil, vegetable and medicinal plants. It can also be used as an indicator electrode in potentiometric titration of EDTA with Fe(3+) ion.

  18. 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

    The Springfield Plateau and Ozark aquifers are important sources of ground water in the Ozark Plateaus aquifer system. Water from these aquifers is used for agricultural, domestic, industrial, and municipal water sources. Changing water use over time in these aquifers presents a need for updated potentiometric-surface maps of the Springfield Plateau and Ozark aquifers. The Springfield Plateau aquifer consists of water-bearing Mississippian-age limestone and chert. The Ozark aquifer consists of Late Cambrian to Middle Devonian age water-bearing rocks consisting of dolostone, limestone, and sandstone. Both aquifers are complex with areally varying lithologies, discrete hydrologic units, varying permeabilities, and secondary permeabilities related to fractures and karst features. During the spring of 2006, ground-water levels were measured in 285 wells. These data, and water levels from selected lakes, rivers, and springs, were used to create potentiometric-surface maps for the Springfield Plateau and Ozark aquifers. Linear kriging was used initially to construct the water-level contours on the maps; the contours were subsequently modified using hydrologic judgment. The potentiometric-surface maps presented in this report represent ground-water conditions during the spring of 2006. During the spring of 2006, the region received less than average rainfall. Dry conditions prior to the spring of 2006 could have contributed to the observed water levels as well. The potentiometric-surface map of the Springfield Plateau aquifer shows a maximum measured water-level altitude within the study area of about 1,450 feet at a spring in Barry County, Missouri, and a minimum measured water-level altitude of 579 feet at a well in Ottawa County, Oklahoma. Cones of depression occur in Dade, Lawrence and Newton Counties in Missouri and Delaware and Ottawa Counties in Oklahoma. These cones of depression are associated with private wells. Ground water in the Springfield Plateau aquifer

  19. Complexes of tetra-tert-butyl-tetraazaporphine with Al(III) and Zr(IV) cations as fluoride selective ionophores.

    PubMed

    Górski, Lukasz; Mroczkiewicz, Monika; Pietrzak, Mariusz; Malinowska, Elzbieta

    2009-02-01

    In this work, complexes of Zr(IV) and Al(III) cations with 2,7,12,17-tetra-tert-butyl-5,10,15,20-tetraazaporphine (TAP) were tested as ionophores in plasticized PVC membranes of ion-selective electrodes. It was found that both tested ionophores show enhanced affinity towards fluoride anion. High fluoride selectivity was observed in the presence of anionic or cationic additives in the membrane, which indicates that proposed compounds work according to charged or neutral carrier mechanism, depending on membrane composition and pretreatment. tert-Butyl substituents, present in the structure of tested compounds, were supposed to prevent formation of ionophore dimers within the membrane phase. This process was found to be responsible for some unfavorable potentiometric properties of electrodes based on complexes of Zr(IV) and Al(III) cations with porphyrins (compounds closely related to tetra-tert-butyl-5,10,15,20-tetraazaporphine). As it was shown using spectrophotometrical measurements, Al(III)-TAP was not susceptible to dimerization, while dimer formation was observed for Zr(IV)-TAP. In full agreement with these observations, electrodes with membranes containing Al(III)-TAP responded in near-Nernstian and fast manner towards fluoride anion, while the employment of Zr(IV)-TAP as ionophore resulted in super-Nernstian and sluggish response. Plasticized PVC membranes doped with Al(III)-TAP and 20mol% of lipophilic anionic additives shown remarkable F(-) selectivity, with selectivity coefficients, logK(F-pot.).(Y-), as follows: -4.4 (Y(-)Br(-)), -4.3 (Cl(-)), -4.2 (NO(3)(-)), -3.6 (SCN(-)), -2.9 (ClO(4)(-)). PMID:19166721

  20. Potentiometric surface of the lower 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 lower Patapsco aquifer in the Patapsco Formation of Cretaceous age in southern Maryland during September 1991 was prepared from water levels measured in 53 wells. The potentiometric surface was at least 125 feet above sea level near the northwestern boundary and outcrop area of the aquifer in a topographically high area of Prince Georges County, and at least 87 ft above sea level in a similar setting in Anne Arundel County. From these high areas, the potentiometric surface declined to the south and southeast toward large well fields at Severndale, Annapolis, Waldorf, La Plata, Indian Head, and Morgantown.

  1. 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.

  2. Map showing the potentiometric surface of the Aquia Aquifer, May 19-23, 1980

    USGS Publications Warehouse

    Chapelle, Frank; Drummond, Dave; Curley, Tracey

    1981-01-01

    The map is based on water level measurements made May 19-23, 1980. The well network used included 83 wells which have been screened in the Aquia aquifer (Aquia Formation of Paleocene Age). Highest levels of the potentiometric surface, 20 to 35 feet above sea level, were measured near the outcrop or subcrop of the aquifer in the topographically high areas of Anne Arundel and Prince Georges Counties. The potentiometric surface slopes to the southeast. Four separate and extensive cones of depression have developed in the potentiometric surface in the vicinities of Lexington Park, Leonardtown, Prince Frederick, and Chesapeake Beach. The cones of Leonardtown and Lexington Park seem to be merging. (USGS)

  3. Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District, September 1980

    USGS Publications Warehouse

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

    1980-01-01

    A September 1980 potentiometric-surface map of the Southwest Florida Water Management District depicts the annual high water-level period. Potentiometric levels rose 1 to 31 feet between May 1980 and September 1980 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 reduced pumping for irrigation and have the greatest range in fluctuations. Generally, potentiometric levels were lower than previous September levels except in Citrus, eastern Levy, and western Marion Counties where levels were 0 to 8 feet higher. (USGS)

  4. Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District, September 1979

    USGS Publications Warehouse

    Yobbi, D.K.; Woodham, W.M.; Laughlin, Charles P.

    1979-01-01

    A September 1979 potentiometric-surface map of the Southwest Florida Water Management District depicts the annual high water-level period. Potentiometric levels increased 1 to 20 feet between May 1979 and September 1979, 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 increases ranged from 0 to 7 feet in coastal, northern, and southern areas of the Water Management District. Generally, potentiometric levels were higher than previous September levels due to heavy rains in August and September. (USGS)

  5. Anion permselective membrane

    NASA Technical Reports Server (NTRS)

    Hodgdon, R. B.; Waite, W. A.

    1980-01-01

    The efforts on the synthesis of polymer anion redox membranes were mainly concentrated in two areas, membrane development and membrane fabrication. Membrane development covered the preparation and evaluation of experimental membranes systems with improved resistance stability and/or lower permeability. Membrane fabrication covered the laboratory scale production of prime candidate membranes in quantities of up to two hundred and sizes up to 18 inches x 18 inches (46 cm x 46 cm). These small (10 in x 11 in) and medium sized membranes were mainly for assembly into multicell units. Improvements in processing procedures and techniques for preparing such membrane sets lifted yields to over 90 percent.

  6. Phosphate binding by a novel Zn(II) complex featuring a trans-1,2-diaminocyclohexane ligand. Effective anion recognition in water.

    PubMed

    Francesconi, Oscar; Gentili, Matteo; Bartoli, Francesco; Bencini, Andrea; Conti, Luca; Giorgi, Claudia; Roelens, Stefano

    2015-02-14

    In this work we have investigated the binding properties of a new synthetic receptor for phosphate anions that combines metal ion coordination with electrostatic and H-bonding interactions. The described receptor is obtained by assembling an iminodiacetic (IDA) fragment, as a Zn(II) binding site, with a polyamine macrocyclic portion containing two trans-1,2-diaminocyclohexane (DAC) units and a pyrrole ring, as a cationic binding site, into an adaptive structure appropriately spanning the length of di- and tridentate phosphates. Potentiometric measurements together with (1)H and (31)P NMR investigation showed that, in a wide pH range including values of physiological interest, the Zn(II) complex of the receptor binds di- and triphosphates, such as ADP, ATP, pyrophosphate (PP) and triphosphate (TP), far better than monophosphate (MP), and that TP is poorly bound by methyliminodiacetate (MIDA) as a model for the Zn(II) binding site. Besides the excellent selectivity over other phosphates, the affinity for TP is the largest reported to date for Zn(II) complexes in water.

  7. Potentiometric studies at ORNL with hydrogen electrode concentration cells

    SciTech Connect

    Mesmer, R.E.; Palmer, D.A.; Wesolowski, D.J.

    1994-12-31

    The absence of suitably stable reference electrodes for and to 300 C led ORNL to develop hydrogen electrode concentration cells for studies of equilibria of interest in reactor and steam generator systems to about 300 C during the late 1960`s and seventies. During the intervening two dozen years over twenty scientists have participated in potentiometric studies at Oak Ridge and much of that work will be summarized in this paper. A description of hydrogen electrode concentration cells developed in the late sixties and currently in use at Oak Ridge is given. The method of measurement, data interpretation, and published results are reviewed for studies of acid-base ionization, metal ion hydrolysis, and metal complexation reactions using principally such cells in titration or flow modes. 41 refs.

  8. Comparison of a potentiometric and a micromechanical triglyceride biosensor.

    PubMed

    Fernandez, Renny Edwin; Hareesh, Vemulachedu; Bhattacharya, Enakshi; Chadha, Anju

    2009-01-01

    Sensitive biosensors for detection of triglyceride concentration are important. In this paper we report on two types of silicon based triglyceride sensors: an electrolyte-insulator-semiconductor capacitor (EISCAP) which is a potentiometric device and a polysilicon microcantilever. The detection principle for both sensors is based on the enzymatic hydrolysis of triglyceride though the sensing mechanisms are different: electronic for the EISCAP and mechanical for the microcantilever. The characteristics and performances of the two sensors are critically compared. The EISCAP sensor necessitates the presence of a buffer for stable measurements which limits the sensitivity of the sensor at low concentrations of the bioanalyte to 1mM. The cantilever sensor works without a buffer which improves the lower level of sensitivity to 10 microm. Both sensors are found to give reproducible and reliable results.

  9. Revised potentiometric-surface map, Yucca Mountain and vicinity, Nevada

    USGS Publications Warehouse

    Ervin, E.M.; Luckey, R.R.; Burkhardt, D.J.

    1993-01-01

    The revised potentiometric-surface map presented in this report updates earlier maps of the Yucca Mountain area using mainly 1988 average water levels. Because of refinements in the corrections to the water-level measurements, these water levels have increased accuracy and precision over older values. The small-gradient area to the southeast of Yucca Mountain is contoured with a 0.25-meter interval and ranges in water-level altitude from 728.5 to 731.0 meters. Other areas with different water levels, to the north and west of Yucca Mountain, are illustrated with shaded patterns. The potentiometric surface can be divided into three regions: 1) A small-gradient area to the southeast of Yucca Mountain, which may be explained by flow through high-transmissivity rocks or low ground-water flux through the area; 2) A moderate-gradient area, on the western side of Yucca Mountain, where the water-level altitude ranges from 775 to 780 meters, and appears to be impeded by the Solitario Canyon Fault and a splay of that fault; and 3) A large-gradient area, to the north-northeast of Yucca Mountain, where water level altitude ranges from 738 to 1,035 meters, possibly as a result of a semi-perched groundwater system. Water levels from wells at Yucca Mountain were examined for yearly trends (1986-89) using linear least-squares regression. Data from five wells exhibited trends which were statistically significant, but some of those may be a result of slow equilibration of the water level from drilling in less permeable rocks. Adjustments for temperature and density changes in the deep wells with long fluid columns were attempted, but some of the adjusted data did not fit the surrounding data and, thus, were not used.

  10. Revised potentiometric-surface map, Yucca Mountain and vicinity, Nevada

    SciTech Connect

    Ervin, E.M.; Luckey, R.R.; Burkhardt, D.J.

    1994-12-01

    The revised potentiometric-surface map presented in this report updates earlier maps of the Yucca Mountain area using mainly 1988 average water levels. Because of refinements in the corrections to the water-level measurements, these water levels have increased accuracy and precision over older values. The small-gradient area to the southeast of Yucca Mountain is contoured with a 0.25-meter interval and ranges in water-level altitude from 728.5 to 73 1.0 meters. Other areas with different water levels, to the north and west of Yucca Mountain, are illustrated with shaded patterns. The potentiometric surface can be divided into three regions: (1) A small-gradient area to the southeast of Yucca Mountain, which may be explained by flow through high-transmissivity rocks or low ground-water flux through the area; (2) A moderate-gradient area, on the western side of Yucca Mountain, where the water-level altitude ranges from 775 to 780 meters, and appears to be impeded by the Solitario Canyon Fault and a splay of that fault; and (3) A large-gradient area, to the north-northeast of Yucca Mountain, where water level altitude ranges from 738 to 1,035 meters, possibly as a result of a semi-perched groundwater system. Water levels from wells at Yucca Mountain were examined for yearly trends using linear least-squares regression. Data from five wells exhibited trends which were statistically significant, but some of those may be a result of slow equilibration of the water level from drilling in less permeable rocks. Adjustments for temperature and density changes in the deep wells with long fluid columns were attempted, but some of the adjusted data did not fit the surrounding data and, thus, were not used.

  11. Microdroplet-Based Potentiometric Redox Measurements on Gold Nanoporous Electrodes.

    PubMed

    Freeman, Christopher J; Farghaly, Ahmed A; Choudhary, Hajira; Chavis, Amy E; Brady, Kyle T; Reiner, Joseph E; Collinson, Maryanne M

    2016-04-01

    Potentiometric redox measurements were made in subnanoliter droplets of solutions using an optically transparent nanoporous gold electrode strategically mounted on the stage of an inverted microscope. Nanoporous gold was prepared via dealloying gold leaf with concentrated nitric acid and was chemisorbed to a standard microscope coverslip with (3-mercaptopropyl)trimethoxysilane. The gold surface was further modified with 1-hexanethiol to optimize hydrophobicity of the surface to allow for redox measurements to be made in nanoscopic volumes. Time traces of the open-circuit potential (OCP) were used to construct Nernst plots to evaluate the applicability of the droplet-based potentiometric redox measurement system. Two poised one-electron transfer systems (potassium ferricyanide/ferrocyanide and ferrous/ferric ammonium sulfate) yielded Nernstian slopes of -58.5 and -60.3 mV, respectively, with regression coefficients greater than 0.99. The y-intercepts of the two agreed well to the formal potential of the two standard oxidation-reduction potential (ORP) calibrants, ZoBell's and Light's solution. The benzoquinone and hydroquinone redox couple was examined as a representative two-electron redox system; a Nernst slope of -30.8 mV was obtained. Additionally, two unpoised systems (potassium ferricyanide and ascorbic acid) were studied to evaluate the system under conditions where only one form of the redox couple is present in appreciable concentrations. Again, slopes near the Nernstian values of -59 and -29 mV, respectively, were obtained. All experiments were carried out using solution volumes between 280 and 1400 pL with injection volumes between 8 and 100 pL. The miniscule volumes allowed for extremely rapid mixing (<305 ms) as well. The small volumes and rapid mixing along with the high accuracy and sensitivity of these measurements lend support to the use of this approach in applications where time is a factor and only small volumes are available for testing. PMID

  12. Miniaturized ionophore-based potentiometric sensors for the flow-injection determination of metformin in pharmaceutical formulations and biological fluids.

    PubMed

    Khaled, Elmorsy; Kamel, Manal S; Hassan, Hassan N; Abd El-Alim, Sameh H; Aboul-Enein, Hassan Y

    2012-12-01

    Miniaturized potentiometric sensors based on β-cyclodextrins (β-CDs) are described for determination of metformin (Mf) in pharmaceutical preparations and biological fluids. Electrode matrix compositions are optimized on the basis of the nature and content of sensing ionophore, ionic sites and plasticizers. Coated wire electrodes (CWEs) modified with heptakis(2,3,6-tri-O-methyl)-β-CD, sodium tetrakis(4-fluorophenyl)borate (NaTFPB) and 2-fluorophenyl 2-nitrophenyl ether (f-NPE), work satisfactorily in the concentration range from 10(-6) to 10(-1) mol L(-1) with Nernstian compliance (55.7 ± 0.4 mV per decade activity) and a detection limit of 8 × 10(-7) mol L(-1). Incorporation of β-CD as a molecular recognition element improved the electrode sensitivity and selectivity due to encapsulation of Mf into the β-CD cavity (host-guest interaction). The developed electrodes have been successfully applied for the potentiometric determination of Mf under batch and flow injection analysis (FIA). FIA allows analysis of 90 samples per h offering the advantages of simplicity, accuracy and automation feasibility. The dissolution profile for metformin pharmaceutical samples (Cidophage®) was monitored using the proposed electrode in comparison with the official spectrophotometric methods. Characterization of the formed Mf-β-CD inclusion complexes is discussed in detail.

  13. Standard addition flow method for potentiometric measurements at low concentration levels: application to the determination of fluoride in food samples.

    PubMed

    Galvis-Sánchez, Andrea C; Santos, João Rodrigo; Rangel, António O S S

    2015-02-01

    A standard addition method was implemented by using a flow manifold able to perform automatically multiple standard additions and in-line sample treatment. This analytical strategy was based on the in-line mixing of sample and standard addition solutions, using a merging zone approach. The flow system aimed to exploit the standard addition method to quantify the target analyte particularly in cases where the analyte concentration in the matrix is below the lower limit of linear response of the detector. The feasibility of the proposed flow configuration was assessed through the potentiometric determination of fluoride in sea salts of different origins and different types of coffee infusions. The limit of quantification of the proposed manifold was 5×10(-6) mol L(-1), 10-fold lower than the lower limit of linear response of the potentiometric detector used. A determination rate of 8 samples h(-1) was achieved considering an experimental procedure based on three standard additions per sample. The main advantage of the proposed strategy is the simple approach to perform multiple standard additions, which can be implemented with other ion selective electrodes, especially in cases when the primary ion is below the lower limit of linear response of the detector.

  14. Protein Detection with Potentiometric Aptasensors: A Comparative Study between Polyaniline and Single-Walled Carbon Nanotubes Transducers

    PubMed Central

    Imran, Hassan; Levon, Kalle; Rius, F. Xavier

    2013-01-01

    A comparison study on the performance characteristics and surface characterization of two different solid-contact selective potentiometric thrombin aptasensors, one exploiting a network of single-walled carbon nanotubes (SWCNTs) and the other the polyaniline (PANI), both acting as a transducing element, is described in this work. The molecular properties of both SWCNT and PANI surfaces have been modified by covalently linking thrombin binding aptamers as biorecognition elements. The two aptasensors are compared and characterized through potentiometry and electrochemical impedance spectroscopy (EIS) based on the voltammetric response of multiply charged transition metal cations (such as hexaammineruthenium, [Ru(NH3)6]3+) bound electrostatically to the DNA probes. The surface densities of aptamers were accurately determined by the integration of the peak for the reduction of [Ru(NH3)6]3+ to [Ru(NH3)6]2+. The differences and the similarities, as well as the transduction mechanism, are also discussed. The sensitivity is calculated as 2.97 mV/decade and 8.03 mV/decade for the PANI and SWCNTs aptasensors, respectively. These results are in accordance with the higher surface density of the aptamers in the SWCNT potentiometric sensor. PMID:23533345

  15. Pseudorotation in fullerene anions

    NASA Astrophysics Data System (ADS)

    Dunn, Janette L.; Hands, Ian D.; Bates, Colin A.

    2007-07-01

    Jahn-Teller (JT) problems are often characterised by an adiabatic potential energy surface (APES) containing either a set of isoenergetic wells or a trough of equivalent-energy points, which may be warped by higher-order coupling terms or anisotropic effects. In all three cases, the JT effect will be dynamic. Either tunnelling between the wells or rotation (of a distortion) around the trough will restore the original symmetry of the system. This motion is referred to as pseudorotation. It should be possible to observe a JT system in a distorted geometry if measurements are made on a sufficiently short timescale. In various cubic systems, this timescale has been calculated to be the order of picoseconds. Such timescales are accessible using modern methods of ultrafast spectroscopy. Measurements of pseudorotation rates can lead to important information on the strength and nature of the JT coupling present. We will present analytical calculations that allow the rate of pseudorotation to be determined in terms of the vibronic coupling parameters. We will show how these results can be applied to E ⊗ e systems and then to the more complicated system applicable to C60- anions. This is of particular interest because of the high icosahedral symmetry of fullerene ions and also because of the many potential uses of materials containing these ions. We conclude by outlining experiments that should be capable of measuring pseudorotation in C 60 anions.

  16. All-solid-state reference electrodes based on colloid-imprinted mesoporous carbon and their application in disposable paper-based potentiometric sensing devices.

    PubMed

    Hu, Jinbo; Ho, Kieu T; Zou, Xu U; Smyrl, William H; Stein, Andreas; Bühlmann, Philippe

    2015-03-01

    Reference electrodes are used in almost every electroanalytical measurement. Here, all-solid-state reference electrodes are described that employ colloid-imprinted mesoporous (CIM) carbon as solid contact and a poly(vinyl chloride) reference membrane to contact the sample. Such a reference membrane is doped with a moderately hydrophilic ionic liquid and a hydrophobic redox couple, leading to well-defined constant potentials at the interfaces of this membrane to the sample and to the solid contact, respectively. Due to the intrinsic properties of CIM carbon, reference electrodes with a CIM carbon solid contact exhibit excellent resistance to common interfering agents such as light and O2, with outstanding potential stability in continuous potentiometric measurements. The potential drift of CIM carbon-based reference electrodes without redox couple is as low as 1.7 μV/h over 110 h, making them the most stable all-solid-state reference electrodes reported so far. To demonstrate the compatibility of CIM carbon-based reference electrodes with miniaturized potentiometric systems, these reference electrodes were integrated into paper-based potentiometric sensing devices, successfully replacing the conventional reference electrode with its reference electrolyte solution. As a proof of concept, disposable paper-based Cl(-) sensing devices that contain stencil-printed Ag/AgCl-based Cl(-) selective electrodes and CIM carbon-based reference electrodes were constructed. These sensing devices are inexpensive, easy to use, and offer highly reproducible Cl(-) measurements with sample volumes as low as 10 μL. PMID:25630744

  17. Design and characterization of novel all-solid-state potentiometric sensor array dedicated to physiological measurements.

    PubMed

    Toczyłowska-Mamińska, Renata; Kloch, Monika; Zawistowska-Deniziak, Anna; Bala, Agnieszka

    2016-10-01

    A novel construction of all-solid-state potentiometric sensor array designed for physiological measurements has been presented. The planar construction and elimination of liquid phase creates broad opportunities for the modifications in the sensing part of the sensor. The designed construction is based on all-solid-state ion-selective electrodes integrated with the ionic-liquid based reference electrode. Work parameters of the sensor arrays were characterized. It has been shown that presented sensor design indicates high sensitivity (55.2±1mV/dec, 56.3±2mV/dec, 58.4±1mV/dec and 53.5±1mV/pH for sodium-, potassium-, chloride- and pH-selective electrodes, respectively in 10(-5)-10(-1.5)M range of primary ions), low response time (t95 did not exceed 10s), high potential stability (potential drift in 28-h measurement was ca. ±2mV) and potential repeatability ca. ±1mV. The system was successfully applied to the simultaneous determination of K(+), Cl(-), Na(+) and pH in the model physiological solution and for the ion flux studies in human colon epithelium Caco-2 cell line as well.

  18. Design and characterization of novel all-solid-state potentiometric sensor array dedicated to physiological measurements.

    PubMed

    Toczyłowska-Mamińska, Renata; Kloch, Monika; Zawistowska-Deniziak, Anna; Bala, Agnieszka

    2016-10-01

    A novel construction of all-solid-state potentiometric sensor array designed for physiological measurements has been presented. The planar construction and elimination of liquid phase creates broad opportunities for the modifications in the sensing part of the sensor. The designed construction is based on all-solid-state ion-selective electrodes integrated with the ionic-liquid based reference electrode. Work parameters of the sensor arrays were characterized. It has been shown that presented sensor design indicates high sensitivity (55.2±1mV/dec, 56.3±2mV/dec, 58.4±1mV/dec and 53.5±1mV/pH for sodium-, potassium-, chloride- and pH-selective electrodes, respectively in 10(-5)-10(-1.5)M range of primary ions), low response time (t95 did not exceed 10s), high potential stability (potential drift in 28-h measurement was ca. ±2mV) and potential repeatability ca. ±1mV. The system was successfully applied to the simultaneous determination of K(+), Cl(-), Na(+) and pH in the model physiological solution and for the ion flux studies in human colon epithelium Caco-2 cell line as well. PMID:27474272

  19. 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)

  20. Galvanostatic entrapment of penicillinase into polytyramine films and its utilization for the potentiometric determination of penicillin.

    PubMed

    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.

  1. 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)

  2. Potentiometric surface of Floridan Aquifer, Southwest Florida Water Management District and adjacent areas, May 1979

    USGS Publications Warehouse

    Wolansky, R.M.; Mills, L.R.; Woodham, W.M.; Laughlin, C.P.

    1979-01-01

    A May 1979 potentiometric-surface map depicts the annual low water-level period. Potentiometric levels declined 4 to 21 feet between September 1978 and May 1979, 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 declines ranged from 0 to 6 feet in coastal, northern, and southern areas of the Water Management District. Generally potentiometric levels were higher than previous May levels due to heavy rains in April and May. In parts of Hillsborough, Pasco, and Pinellas Counties, May 1979 potentiometric levels were 18 feet higher than those of September 1978. (USGS)

  3. Potentiometric determination of urea by sequential injection using Jack bean meal crude extract as a source of urease.

    PubMed

    Silva, F V; Nogueira, A R; Souza, G B; Reis, B F; Araújo, A N; Montenegro, M C; Lima, J L

    2000-11-01

    A sequential injection system was proposed to accomplish the potentiometric determination of urea. This procedure used an ammonium tubular selective electrode to assess ammonium concentration produced by enzymatic hydrolysis of urea from Jack bean meal (Canavalia ensiformis DC) crude extract. A gaseous diffusion device was coupled to the flow set-up allowing on-line sampling and suitable selectivity for determinations. A detection limit of 6.0x10(-4) mol urea l(-1), a relative standard deviation of 1.9% (n=10) and a sampling rate of 20 samples h(-1) were observed when 172 Sumner units (SU) of urease and 900 mul of sample were used. Results agreeing with a comparative method were obtained by the proposed procedure and the use of the crude extract solution combined with the sequential injection approach improved the performance, producing reproducible results and low costs in comparison with procedures using commercial enzymes. PMID:18968118

  4. Organic Anion Transporting Polypeptides

    PubMed Central

    Stieger, Bruno; Hagenbuch, Bruno

    2013-01-01

    Organic anion transporting polypeptides or OATPs are central transporters in the disposition of drugs and other xenobiotics. In addition, they mediate transport of a wide variety of endogenous substrates. The critical role of OATPs in drug disposition has spurred research both in academia and in the pharmaceutical industry. Translational aspects with clinical questions are the focus in academia, while the pharmaceutical industry tries to define and understand the role these transporters play in pharmacotherapy. The present overview summarizes our knowledge on the interaction of food constituents with OATPs, and on the OATP transport mechanisms. Further, it gives an update on the available information on the structure-function relationship of the OATPs, and finally, covers the transcriptional and posttranscriptional regulation of OATPs. PMID:24745984

  5. Resonant spectra of quadrupolar anions

    NASA Astrophysics Data System (ADS)

    Fossez, K.; Mao, Xingze; Nazarewicz, W.; Michel, N.; Garrett, W. R.; Płoszajczak, M.

    2016-09-01

    In quadrupole-bound anions, an extra electron is attached at a sufficiently large quadrupole moment of a neutral molecule, which is lacking a permanent dipole moment. The nature of the bound states and low-lying resonances of such anions is of interest for understanding the threshold behavior of open quantum systems in general. In this work, we investigate the properties of quadrupolar anions as halo systems, the formation of rotational bands, and the transition from a subcritical to supercritical electric quadrupole moment. We solve the electron-plus-rotor problem using a nonadiabatic coupled-channel formalism by employing the Berggren ensemble, which explicitly contains bound states, narrow resonances, and the scattering continuum. The rotor is treated as a linear triad of point charges with zero monopole and dipole moments and nonzero quadrupole moment. We demonstrate that binding energies and radii of quadrupolar anions strictly follow the scaling laws for two-body halo systems. Contrary to the case of dipolar anions, ground-state band of quadrupolar anions smoothly extend into the continuum, and many rotational bands could be identified above the detachment threshold. We study the evolution of a bound state of an anion as it dives into the continuum at a critical quadrupole moment and we show that the associated critical exponent is α =2 . Everything considered, quadrupolar anions represent a perfect laboratory for the studies of marginally bound open quantum systems.

  6. Chromium(III) selective membrane sensors based on Schiff bases as chelating ionophores.

    PubMed

    Singh, A K; Gupta, V K; Gupta, Barkha

    2007-02-28

    The two chromium chelates of Schiff bases, N-(acetoacetanilide)-1,2-diaminoethane (L(1)) and N,N'-bis(acetoacetanilide)-triethylenetetraammine (L(2)), have been synthesized and explored as neutral ionophores for preparing poly(vinylchloride) (PVC) based membrane sensors selective to Cr(III). The addition of lipophilic anion excluder (NaTPB) and various plasticizers viz. o-Nitrophenyloctyl ether (o-NPOE), dioctylpthalate (DOP), dibutylphthalate (DBP), tris(2-ethylhexyl)phosphate (TEHP), and benzyl acetate (BA) have found to improve the performance of the sensors. The best performance was obtained for the membrane sensor having a composition of L(1):PVC:DBP:NaTPB in the ratio 5:150:250:3 (w/w). The sensor exhibits Nernstian response in the concentration range 8.9 x 10(-8) to 1.0 x 10(-1) M Cr(3+) with limit of detection 5.6 x 10(-8) M. The proposed sensor manifest advantages of relatively fast response (10s) and good selectivity over some alkali, alkaline earth, transition and heavy metal ions. The selectivity behavior of the proposed electrode revealed a considerable improvement as compared to the best previously PVC-membrane electrode for chromium(III) ion. The potentiometric response of the proposed sensor was independent of pH of the test solution in the range of 2.0-7.0. The sensor has found to work satisfactorily in partially non-aqueous media up to 20% (v/v) content of methanol, ethanol and acetonitrile and could be used for a period of 3 months. The proposed electrode was used as an indicator electrode in potentiometric titration of chromium ion with EDTA and in direct determination in different water and food samples.

  7. Inhibitive potentiometric detection of trace metals with ultrathin polypyrrole glucose oxidase biosensor.

    PubMed

    Ayenimo, Joseph G; Adeloju, Samuel B

    2015-05-01

    A method, based on the inhibition of an ultrathin polypyrrole-glucose oxidase (PPy-GOx) potentiometric biosensor response, is described for the detection of Cu(2+), Hg(2+), Cd(2+) and Pb(2+) ions. Based on experimental conditions (0.2 M pyrrole, 500 U mL(-1) GOx, and an applied current density of 0.05 mA cm(-2) and a polymerization period of 500s) previously published by us, PPy-GOx films of approximately 55 nm thick were used to demonstrate the inhibitive potentiometric detection of selected trace metals down to 0.079 μM Cu(2+), 0.025 μM Hg(2+), 0.024 μM Pb(2+) and 0.044 μM Cd(2+). Furthermore, good linear concentration ranges were achieved for Cu(2+) (0.079-16 μM), Hg(2+) (0.025-5 μM), Pb(2+) (0.10-15 μM) and Cd(2+) (0.04-62 μM). The analysis of the nature of the inhibition of glucose oxidase in the PPy-GOx biosensor by these metals was achieved by Dixon and Cornish-Bowden plots. The shapes of the curves (exponential decay, parabolic and linear) obtained for the inhibitors suggest that the inhibition by the metal ions may not be exclusively directed at the essential -SH group, but involve additional binding sites of the enzyme. Dixon and Cornish-Bowden plots suggest that the inhibition is competitive for Cd(2+), while non-competitive inhibition was observed for other metal ions. The ultra-thin PPy-GOx film enabled improved permeability to the metal inhibitors than possible with conventional biosensors with thicker films and, hence, better reflects the actual inhibition effect of the trace metals on the enzyme activity. The use of the ultra-thin film also eliminated the usual need for incubation of the enzyme electrode for a long period in the presence of the inhibitors. Furthermore, a rapid recovery of the enzyme activity was achieved by simply washing the electrode with water and storing in phosphate buffer for 10-15 min. The proposed biosensing approach was successfully used for the detection of individual trace metals in tap water, achieving a 98

  8. Inhibitive potentiometric detection of trace metals with ultrathin polypyrrole glucose oxidase biosensor.

    PubMed

    Ayenimo, Joseph G; Adeloju, Samuel B

    2015-05-01

    A method, based on the inhibition of an ultrathin polypyrrole-glucose oxidase (PPy-GOx) potentiometric biosensor response, is described for the detection of Cu(2+), Hg(2+), Cd(2+) and Pb(2+) ions. Based on experimental conditions (0.2 M pyrrole, 500 U mL(-1) GOx, and an applied current density of 0.05 mA cm(-2) and a polymerization period of 500s) previously published by us, PPy-GOx films of approximately 55 nm thick were used to demonstrate the inhibitive potentiometric detection of selected trace metals down to 0.079 μM Cu(2+), 0.025 μM Hg(2+), 0.024 μM Pb(2+) and 0.044 μM Cd(2+). Furthermore, good linear concentration ranges were achieved for Cu(2+) (0.079-16 μM), Hg(2+) (0.025-5 μM), Pb(2+) (0.10-15 μM) and Cd(2+) (0.04-62 μM). The analysis of the nature of the inhibition of glucose oxidase in the PPy-GOx biosensor by these metals was achieved by Dixon and Cornish-Bowden plots. The shapes of the curves (exponential decay, parabolic and linear) obtained for the inhibitors suggest that the inhibition by the metal ions may not be exclusively directed at the essential -SH group, but involve additional binding sites of the enzyme. Dixon and Cornish-Bowden plots suggest that the inhibition is competitive for Cd(2+), while non-competitive inhibition was observed for other metal ions. The ultra-thin PPy-GOx film enabled improved permeability to the metal inhibitors than possible with conventional biosensors with thicker films and, hence, better reflects the actual inhibition effect of the trace metals on the enzyme activity. The use of the ultra-thin film also eliminated the usual need for incubation of the enzyme electrode for a long period in the presence of the inhibitors. Furthermore, a rapid recovery of the enzyme activity was achieved by simply washing the electrode with water and storing in phosphate buffer for 10-15 min. The proposed biosensing approach was successfully used for the detection of individual trace metals in tap water, achieving a 98

  9. Probes for anionic cell surface detection

    DOEpatents

    Smith, Bradley D.

    2013-03-05

    Embodiments of the present invention are generally directed to compositions comprising a class of molecular probes for detecting the presence of anionic cell surfaces. Embodiments include compositions that are enriched for these compositions and preparations, particularly preparations suitable for use as laboratory/clinical reagents and diagnostic indicators, either alone or as part of a kit. An embodiment of the invention provides for a highly selective agent useful in the discernment and identification of dead or dying cells, such as apoptotic cells, in a relatively calcium-free environment. An embodiment of the invention provides a selective agent for the identification of bacteria in a mixed population of bacterial cells and nonbacterial cells.

  10. The superfamily of organic anion transporting polypeptides.

    PubMed

    Hagenbuch, B; Meier, P J

    2003-01-10

    Organic anion transporting polypeptides (Oatps/OATPs) form a growing gene superfamily and mediate transport of a wide spectrum of amphipathic organic solutes. Different Oatps/OATPs have partially overlapping and partially distinct substrate preferences for organic solutes such as bile salts, steroid conjugates, thyroid hormones, anionic oligopeptides, drugs, toxins and other xenobiotics. While some Oatps/OATPs are preferentially or even selectively expressed in one tissue such as the liver, others are expressed in multiple organs including the blood-brain barrier (BBB), choroid plexus, lung, heart, intestine, kidney, placenta and testis. This review summarizes the actual state of the rapidly expanding OATP superfamily and covers the structural properties, the genomic classification, the phylogenetic relationships and the functional transport characteristics. In addition, we propose a new species independent and open ended nomenclature and classification system, which is based on divergent evolution and agrees with the guidelines of the Human Genome Nomenclature Committee.

  11. An intracellular anion channel critical for pigmentation.

    PubMed

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-12-16

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation.

  12. Single interface flow system with potentiometric detection for the determination of nitrate in water and vegetables.

    PubMed

    Santos, João Rodrigo; Santos, João L M; Lima, José L F C

    2010-01-15

    In this work a single interface flow system (SIFA) with potentiometric detection was for the first time implemented and applied to the determination of nitrate in waters and plant extracts. The analytical potential of the SIFA system was exploited not only to transport the sample towards detection but also to carry out, in a reproducible and automated way, the tasks associated with sample pre-treatment, namely ionic strength, pH adjustment and interfering species suppression. The advantageous aspects of combining a SIFA system with potentiometry with enhanced simplicity, ease of implementation and automation were further discussed and emphasised. The obtained results showed relative deviations lower than 5%, for both types of samples, with sampling rates of about 40h(-1). In addition, an innovative and straightforward process for constructing plastic membrane ion selective electrodes with a tubular configuration able to be coupled to flow-based analytical systems is also proposed. The developed approach, consisting of assembling the electrode inside a flow tubing connector is very simple to implement, robust, particularly adequate to be combined with flow methodologies and maintains all dynamic and analytical characteristics exhibited by previous assembling processes.

  13. Potentiometric sensors for the determination of trifluoperazine hydrochloride in pharmaceutical preparations.

    PubMed

    Hassan, Ahmed K; Ameen, Suhaam T; Saad, Bahruddin; Al-Aragi, Suad M

    2009-11-01

    Trifluoperazine is widely used in the treatment of psychotic patients for its neuroleptic and antidepressive action. In this study, the construction, evaluation and application of new potentiometric sensors for trifluoperazine hydrochloride (TFPH) are described. The sensing membranes incorporated either ion-pair complexes of the trifluoperazine cation and phosphotungstic acid (PTA) or phosphomolybdic acid (PMA) or sodium tetraphenyl borate (NaTPB) as electroactive materials in poly(vinyl chloride) matrix membrane. The plasticizers used were di-n-butyl phthalate (DBPH) and tri-n-butyl phosphate (TBP). After a series of experiments, the best electrodes were based on PTA or PMA as electroactive materials and DBPH as plasticizer. A linear concentration range between 1 x 10(-5)-1 x 10(-2) M with a near Nernstian slope of 28.43 and 32.11 mV decade(-1), respectively, was obtained. The electrodes were characterized in terms of the composition, usable pH range, life span and response time. The selectivity coefficient values were calculated for different inorganic cations and sugars. Validation of the method shows the suitability of the electrodes for the determination of TFPH in pharmaceutical formulations.

  14. Novel PVC-membrane electrode for flow injection potentiometric determination of Biperiden in pharmaceutical preparations.

    PubMed

    Khaled, Elmorsy; El-Sabbagh, Inas A; El-Kholy, N G; Ghahni, E Y Abdel

    2011-12-15

    The construction and performance characteristics of Biperiden (BP) polyvinyl chloride (PVC) electrodes are described. Different methods for electrode fabrication are tested including; incorporation of BP-ion pairs (BP-IPs), incorporation of ion pairing agents, or soaking the plain electrode in BP-ion pairs suspension solution. Electrode matrices were optimized referring to the effect of modifier content and nature, plasticizer and the method of modification. The proposed electrodes work satisfactorily in the BP concentration range from 10(-5) to 10(-2)mol L(-1), with fast response time (7s) and adequate operational lifetime (28 days). The electrode potential is pH independent within the range 2.0-7.0, with good selectivity towards BP in presence of various interfering species. The developed electrodes have been applied for potentiometric determination of BP in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. FIA offers the advantages of accuracy and automation feasibility with high sampling frequency. The dissolution profile for Akineton tablets (2mg BP/tablet) was studied using the proposed electrode in comparison with the official methods.

  15. A potentiometric biosensor for the detection of notch 3 using functionalized ZnO nanorods.

    PubMed

    Ibupoto, Z H; Khun, K; Liu, X; Willander, M

    2014-09-01

    The notch signalling plays a vital and radical role for the activity of cellular proliferation, differentiation and apoptosis. In this study, for the first time a particular biosensor is developed for the detection of notch 3. ZnO nanorods were fabricated on the gold coated glass substrate by hydrothermal method and afterwards were decorated with the gold nanoparticles by electrodepositing technique. Scanning electron microscopy (SEM) has shown the perpendicular to the substrate growth pattern of ZnO nanorods. X-ray diffraction (XRD) studies showed the c-axis oriented growth direction with wurtzite crystal structure of ZnO nanorods. X-ray Photoelectron Spectroscopy (XPS) and energy dispersive X-ray (EDX) techniques have shown the presence of Zn, O and Au atoms in the prepared functional material. Furthermore, the anti-notch 3 was physically adsorbed on the gold nanoparticles functionalized ZnO nanorods. The developed potentiometric immunosensor has shown response to the wide range of notch 3 molecules. The detected range included 1.00 x 10(-5)-1.50 x 10(0 ) μg/mL with a sensitivity of 23.15 ± 0.31 mV/decade. The analytical parameters including reproducibility, stability, and selectivity were also investigated and the observed results indicate the acceptable performance of the notch 3 biosensor. Moreover, the proposed notch 3 biosensor exhibited a fast response time of 10 s. PMID:25924320

  16. Anion-exchange nanospheres as titration reagents for anionic analytes.

    PubMed

    Zhai, Jingying; Xie, Xiaojiang; Bakker, Eric

    2015-08-18

    We present here anion-exchange nanospheres as novel titration reagents for anions. The nanospheres contain a lipophilic cation for which the counterion is initially Cl(-). Ion exchange takes place between Cl(-) in the nanospheres and a more lipophilic anion in the sample, such as ClO4(-) and NO3(-). Consecutive titration in the same sample solution for ClO4(-) and NO3(-) were demonstrated. As an application, the concentration of NO3(-) in spinach was successfully determined using this method.

  17. 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.

  18. 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.

  19. Ion-pairing ability, chemical stability, and selectivity behavior of halogenated dodecacarborane cation exchangers in neutral carrier-based ion-selective electrodes.

    PubMed

    Peper, Shane; Qin, Yu; Almond, Philip; McKee, Michael; Telting-Diaz, Martin; Albrecht-Schmitt, Thomas; Bakker, Eric

    2003-05-01

    Recently, it has been discovered that carba-closo-dodecaborates can be used as cation exchangers in neutral carrier-based ion-selective chemical sensors. Because of their inherent chemical stability and versatile functionalization chemistries, they offer many advantages that may potentially be exploited for ion analyses that require nontraditional sample conditions, including strongly acidic media. In this work, trimethylammonium salts of undecachlorinated (UCC), undecabrominated (UBC), hexabrominated (HBC), and undecaiodinated (UIC) carborane anions were prepared and evaluated for their potential use in solvent polymeric membrane-based sensors. Computational methods including Natural population analysis and electrostatic mapping were used to predict the ion-exchanging ability of each lipophilic anion. In addition, the sandwich membrane technique was used to evaluate the ion-pairing ability of each carborane anion in situ (i.e., within bis(2-ethylhexyl) sebacate (DOS)- and 2-nitrophenyl octyl ether (o-NPOE)-plasticized ISE membranes). The results of the computational and potentiometric studies found that binding affinity of the anions followed the generalized trend HBC > UCC > UBC > UIC. PVC-DOS bulk optode thin films containing the chromoionophore ETH 5315 and a respective anion were used to determine the chemical stability/lipophilicity of the carboranes and tetrakis[3,5-bis(trifluoromethyl)phenyl] borate (TFPB) in acidic media (0.2 M HOAc) under flowing conditions. The studies found that in terms of stability/lipophilicity UIC > UBC > TFPB approximately UCC > HBC. Electrodes containing a Pb(2+)-selective ionophore, tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide)(lead IV), were used to evaluate the functionality of each cation exchanger. An evaluation of response characteristics such as slope and selectivity found that UIC and UBC were quite comparable to the behavior of TFPB. Interestingly, both UIC and UBC showed a marked selectivity improvement

  20. Potentiometric study of antioxidant activity: development and prospects.

    PubMed

    Ivanova, A V; Gerasimova, E L; Brainina, Kh Z

    2015-01-01

    The increasing interest in the study of the antioxidant activity of different objects is caused by an unbalance between the formation of reactive oxygen species (ROS) and the performance of the antioxidant system in humans under certain conditions, which leads to oxidative stress and pathological states of the organism. This article presents a brief critical review of the methods that are used to measure integrated antioxidant activity (AOA). It is shown that the most promising methods for measuring AOA are electrochemical ones, particularly potentiometry, as it best fits the nature of the processes causing oxidative stress. The article gives the theoretical rational for requirements that an oxidizer of antioxidants (AO) should meet. The work presents the thermodynamic grounds for the use of an earlier proposed mediator system, kinetics of chemical reactions between AO and the mediator system. In order to confirm reliability and accuracy of the results, numerous correlation studies were conducted, aiming to compare the data obtained with the use the proposed method and independent analytical methods. The article presents the results of the potentiometric study of AOA for a variety of objects, including individual antioxidant → nutritional supplements → food → blood and blood fractions.

  1. Novel heterocyclic thiosemicarbazones derivatives as colorimetric and “turn on” fluorescent sensors for fluoride anion sensing employing hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Ashok Kumar, S. L.; Saravana Kumar, M.; Sreeja, P. B.; Sreekanth, A.

    2013-09-01

    Two novel heterocyclic thiosemicarbazone derivatives have been synthesized, and characterized, by means of spectroscopic and single crystal X-ray diffraction methods. Their chromophoric-fluorogenic response towards anions in competing solvent dimethyl sulfoxide (DMSO) was studied. The receptor shows selective recognition towards fluoride anion. The binding affinity of the receptors with fluoride anion was calculated using UV-visible and fluorescence spectroscopic techniques.

  2. A comparative study on fabrication of Mn2+ selective polymeric membrane electrode and coated graphite electrode.

    PubMed

    Singh, Ashok Kumar; Bandi, Koteswara Rao; Upadhyay, Anjali; Jain, A K

    2013-03-01

    Poly(vinyl chloride)-based membranes of two ligands 2,4-bis(2-acetoxybenzylamino)-6-phenyl-1,3,5-triazine (L1) and N2,N4-di(cyanoethyl)-2,4-bis(2-acetoxybenzylamino)-6-phenyl-1,3,5-triazine (L2) were fabricated and explored as Mn(2+) ion selective electrodes. The performance of the polymeric membranes electrodes of ionophores with different plasticizers (dibutylphthalate, benzoic acid, o-nitrophenyloctyl ether, 1-chloronapthalene and tri-n-butylphosphate) and anion excluders (sodium tetraphenylborate and potassium tetrakis p-(chloro phenyl)borate) was looked in to and the better results were obtained with the membrane having composition L2: NaTPB: DBP: PVC as 6: 3: 56: 35 (w/w; mg). The coated graphite electrode (CGE) with same composition was also fabricated and investigated as Mn(2+) selective electrode. It was found that CGE showed better response characteristics than PME. The potentiometric response of CGE was independent of pH in the range 3.0-9.0 exhibiting the Nernstian slope 29.5 ± 0.3 mVdecade(-1) of activity and working concentration range 4.1 × 10(-7)-1.0 × 10(-1)mol L(-1) with a limit of detection 6.7 × 10(-8)mol L(-1). The electrode showed a fast response time of 12s with a shelf life of 105 days. The proposed CGE could be successfully used for the determination of Mn(2+) ions in different water, soil, vegetables and medicinal plants also used as an indicator electrode in potentiometric titration with EDTA.

  3. Anion Transport with Chalcogen Bonds.

    PubMed

    Benz, Sebastian; Macchione, Mariano; Verolet, Quentin; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2016-07-27

    In this report, we introduce synthetic anion transporters that operate with chalcogen bonds. Electron-deficient dithieno[3,2-b;2',3'-d]thiophenes (DTTs) are identified as ideal to bind anions in the focal point of the σ holes on the cofacial endocyclic sulfur atoms. Anion binding in solution and anion transport across lipid bilayers are found to increase with the depth of the σ holes of the DTT anionophores. These results introduce DTTs and related architectures as a privileged motif to engineer chalcogen bonds into functional systems, complementary in scope to classics such as 2,2'-bipyrroles or 2,2'-bipyridines that operate with hydrogen bonds and lone pairs, respectively. PMID:27433964

  4. 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)

  5. Highly sensitive covalently functionalized light-addressable potentiometric sensor for determination of biomarker.

    PubMed

    Liang, Jintao; Guan, Mingyuan; Huang, Guoyin; Qiu, Hengming; Chen, Zhengcheng; Li, Guiyin; Huang, Yong

    2016-06-01

    A biomarker is related to the biological status of a living organism and shows great promise for the early prediction of a related disease. Herein we presented a novel structured light-addressable potentiometric sensor (LAPS) for the determination of a model biomarker, human immunoglobulin G (hIgG). In this system, the goat anti-human immunoglobulin G antibody was used as recognition element and covalently immobilized on the surface of light-addressable potentiometric sensor chip to capture human immunoglobulin G. Due to the light addressable capability of light-addressable potentiometric sensor, human immunoglobulin G dissolved in the supporting electrolyte solution can be detected by monitoring the potential shifts of the sensor. In order to produce a stable photocurrent, the laser diode controlled by field-programmable gate array was used as the light emitter to drive the light-addressable potentiometric sensor. A linear correlation between the potential shift response and the concentration of human immunoglobulin G was achieved and the corresponding regression equation was ΔV (V)=0.00714ChIgG (μg/mL)-0.0147 with a correlation coefficient of 0.9968 over a range 0-150 μg/mL. Moreover, the light-addressable potentiometric sensor system also showed acceptable stability and reproducibility. All the results demonstrated that the system was more applicable to detection of disease biomarkers with simple operation, multiple-sample format and might hold great promise in various environmental, food, and clinical applications.

  6. Development of novel enzyme potentiometric biosensor based on pH-sensitive field-effect transistors for aflatoxin B1 analysis in real samples.

    PubMed

    Stepurska, K V; Soldatkin, O O; Arkhypova, V M; Soldatkin, A P; Lagarde, F; Jaffrezic-Renault, N; Dzyadevych, S V

    2015-11-01

    This study aimed at the development and optimization of a potentiometric biosensor based on pH-sensitive field-effect transistors and acetylcholinesterase for aflatoxin B1 determination in real samples. Optimal conditions for bioselective elements operation were defined and analytical characteristics of the proposed biosensor were studied. The proposed biosensor characterized high operational stability and reproducibility of signal. Selectivity of acetylcholinesterase-biosensor to aflatoxins in relation to other groups of toxic substances was analyzed. The developed biosensor was applied to the determination of aflatoxin B1 in real samples (sesame, walnut and pea).

  7. Adsorption properties of the nanozirconia/anionic polyacrylamide system-Effects of surfactant presence, solution pH and polymer carboxyl groups content

    NASA Astrophysics Data System (ADS)

    Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

    2016-05-01

    The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate-SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level.

  8. Collision-induced dissociation of fluoropyridinide anions

    NASA Astrophysics Data System (ADS)

    Kato, Shuji; Lineberger, W. Carl; Bierbaum, Veronica M.

    2007-10-01

    Collision-induced dissociation of ortho-fluoro, meta-fluoro, and 2,6-difluoropyridinide anions are studied using the selected ion flow tube technique. Structures and energetics of the reactants, transition states, and products are calculated at the MP4(SDQ)/6-31 + G(d) level of theory based on the B3LYP/6-311++G(d,p) and/or MP2/6-31 + G(d) optimized geometries. The monofluoropyridinide anions (C5NH3F-) dissociate almost exclusively via loss of an HF molecule, i.e., C5NH2- + HF at low collision energies, in addition to loss of F- at higher energies. 2,6-Difluoropyridinide anions (C5NH2F2-) dissociate via successive loss of HF molecules to form C5NHF- then C5N- depending on the collision energy. The CID results strongly suggest formation of ring-intact pyridynide structures (C5NH2-, C5NHF-) with a bent triple bond embedded in the azine ring systems. Calculated reaction energy diagrams are totally consistent with the experimental observations. Didehydropyridynides C5NH2- and C5NHF- have substantial barriers to decomposition. Tetradehydropyridynide C5N- is a highly strained ring system and metastable with a predicted barrier of about 5 kcal mol-1 (20 kJ mol-1) toward ring-opening to a linear NCCCCC- structure. The observed C5N- species is most likely the linear anion under experimental conditions; however, the ring-intact C5N- pyridynide is a highly energetic species releasing about 80 kcal mol-1 (340 kJ mol-1) of energy upon the ring-opening.

  9. Relationship of net chloride flow across the human erythrocyte membrane to the anion exchange mechanism

    SciTech Connect

    Knauf, P.A.; Law, F.Y.; Marchant, P.J.

    1983-01-01

    The parallel effects of the anion transport inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'disulfonate) on net chloride flow and on chloride exchange suggest that a major portion of net chloride flow takes place through the anion exchange system. The ''slippage'' model postulates that the rate of net anion flow is determined by the movement of the unloaded anion transport site across the membrane. Both the halide selectivity of net anion flow and the dependence of net chloride flux on chloride concentration over the range of 75 to 300 mM are inconsistent with the slippage model. Models in which the divalent form of the anion exchange carrier or water pores mediate net anion flow are also inconsistent with the data. The observations that net chloride flux increases with chloride concentration and that the DIDS-sensitive component tends to saturate suggest a model in which net anion flow involves ''transit'' of anions through the diffusion barriers in series with the transport site, without any change in transport site conformation such as normally occurs during the anion exchange process. This model is successful in predicting that the anion exchange inhibitor NAP-taurine, which binds to the modifier site and inhibits the conformational change, has less effect on net chloride flow than on chloride exchange.

  10. Photoelectron spectroscopy of boron aluminum hydride cluster anions

    SciTech Connect

    Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Gantefoer, Gerd; Bowen, Kit H. E-mail: kiran@mcneese.edu; Li, Xiang; Kiran, Boggavarapu E-mail: kiran@mcneese.edu; Kandalam, Anil K.

    2014-04-28

    Boron aluminum hydride clusters are studied through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations. Boron aluminum hydride cluster anions, B{sub x}Al{sub y}H{sub z}{sup −}, were generated in a pulsed arc cluster ionization source and identified by time-of-flight mass spectrometry. After mass selection, their photoelectron spectra were measured by a magnetic bottle-type electron energy analyzer. The resultant photoelectron spectra as well as calculations on a selected series of stoichiometries reveal significant geometrical changes upon substitution of aluminum atoms by boron atoms.

  11. Potentiometric surface of the Ozark aquifer in northern Arkansas, 2010

    USGS Publications Warehouse

    Czarnecki, John B.; Pugh, Aaron L.; Blackstock, Joshua M.

    2014-01-01

    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 56 well and 5 spring water-level measurements made in 2010 in Arkansas and Missouri, has a maximum water-level altitude measurement of 1,174 feet in Carroll County and a minimum water-level altitude measurement of 120 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. Water-level altitudes changed 0.5 feet or less in 31 out of 56 wells measured between 2007 and 2010. Despite rapidly increasing population within the study area, the increase appears to have minimal effect on groundwater levels, although the effect may have been minimized by the development and use of surface-water distribution infrastructure, suggesting that most of the incoming populations are fulfilling their water needs from surface-water sources. The conversion of some users from groundwater to surface water may be allowing water levels in some wells to recover (rise) or decline at a slower rate in some areas such as in Benton, Carroll, and Washington Counties.

  12. Anion exchange polymer electrolytes

    DOEpatents

    Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

    2013-07-23

    Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

  13. Bound anionic states of adenine

    SciTech Connect

    Haranczyk, Maciej; Gutowski, Maciej S; Li, Xiang; Bowen, Kit H

    2007-03-20

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases, are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the new-found anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The discovery of these valence anionic states of adenine was facilitated by the development of: (i) a new experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a new combinatorial/ quantum chemical approach for identification of the most stable tautomers of organic molecules. The computational portion of this work was supported by the: (i) Polish State Committee for Scientific Research (KBN) Grants: DS/8000-4-0140-7 (M.G.) and N204 127 31/2963 (M.H.), (ii) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.), and (iii) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic

  14. 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)

  15. Potentiometric Surface of the Upper Patapsco 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 Upper Patapsco aquifer in the Patapsco Formation of Cretaceous age in Southern Maryland during September 2001. The map is based on water-level measurements in 49 wells. The potentiometric surface was highest at 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 southeast toward large well fields in the Annapolis area, and from all directions toward a cone of depression located southwest of Waldorf. The ground-water level declined to 26 feet below sea level in the Annapolis area, and the lowest water level was 132 feet below sea level southwest of Waldorf.

  16. Potentiometric surface of the upper Patapsco 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 Upper Patapsco aquifer in the Patapsco Formation of Cretaceous age in Southern Maryland during September 1999. The map is based on water-level measurements in 49 wells. The potentiometric surface was 119 feet above sea level near the northern boundary and outcrop area of the aquifer in a topographically high area of Anne Arundel County, and 55 feet above sea level in a similar setting in Prince Georges County. From these high areas, the potentiometric surface declined to the southeast toward large well fields in the Annapolis area, and from all directions toward a cone of depression southwest of Waldorf. Ground-water levels declined to 20 feet below sea level in the Annapolis area, and 131 feet below sea level southwest of Waldorf.

  17. 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.

  18. 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)

  19. 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.

  20. 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)

  1. 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.

  2. 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.

  3. Potentiometric map of the lower Wilcox aquifer in Mississippi, fall 1982

    USGS Publications Warehouse

    Darden, Daphne

    1986-01-01

    This potentiometric map is the second map of the lower Wilcox aquifer 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 surface of the major aquifers in Mississippi. The potentiometric surface of the lower Wilcox aquifer slopes generally to the west away from the outcrop area and it is marked by a large groundwater cone of depression in the area of Tallahatchie, Quitman, and Panola Counties. Water levels in or near the outcrop of the lower Wilcox aquifer show little longterm change. Heavy withdrawals in the downdip area have caused water level declines of about 1 to 2 feet per year since 1979 in much of the confined part of the aquifer. These water level declines in the area of Tallahatchie, Quitman, and Panola Counties have resulted in a wider cone of depression since 1979. (USGS)

  4. Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District, May 1980

    USGS Publications Warehouse

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

    1980-01-01

    A May 1980 potentiometric-surface map of the Southwest Florida Water Management District depicts the annual low water-level period. Potentiometric levels decreased 5 to 36 feet between September 1979 and May 1980, in the citrus and farming sections of southern Hillsborough, southwestern Polk, northwestern DeSoto , Hardee, 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 8 feet in coastal, northern, and southern areas of the Water Management District. Generally, potentiometric levels were lower than previous May levels except in the northernmost and southernmost counties where water levels were 1 to 5 feet higher. (USGS)

  5. Gallium based low-interaction anions

    DOEpatents

    King, Wayne A.; Kubas, Gregory J.

    2000-01-01

    The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

  6. Potentiometric surface of the Sparta and Memphis aquifers in eastern Arkansas, April through July 1993

    USGS Publications Warehouse

    Westerfield, Paul W.

    1995-01-01

    A water-level map of the Sparta and Memphis aquifers for 1993 is presented in this map report. The Sparta-Memphis aquifer, consisting of sands of Eocene age, is present in much of southern and eastern Arkansas. The potentiometric surface map and long-term hydrographs illustrate the effects of large withdrawals for industrial and public supply and, to a lesser extent, agricultural use, on water levels in the aquifer. Three cones of depression, centered in Columbia, Jefferson, and Union Counties, occur in the potentiometric surface.

  7. 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.

  8. 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.

  9. Potentiometric surface of the Floridan Aquifer, Southwest Florida Water Management District and adjacent areas, September 1978

    USGS Publications Warehouse

    Wolansky, R.M.; Mills, L.R.; Woodham, W.M.; Laughlin, C.P.

    1978-01-01

    A September 1978 potentiometric-surface map depicts the annual high water-level period of the Floridan aquifer in the Southwest Florida Management District. Potentiometric levels increased 10 to 25 feet between May 1978 and September 1978, in the citrus and farming sections of southern Hillsborough, northern Hardee, southwestern Polk and Manatee Counties. These areas are widely affected by pumping for irrigation and have the greatest fluctuations in water-levels between the low and high water-level periods. Water-level rises in coastal, northern and southern areas of the Water Management District ranged from 0 to 10 feet. (Woodard-USGS)

  10. Potentiometric surface of Floridan aquifer, Southwest Florida Water Management District and adjacent areas, September 1977

    USGS Publications Warehouse

    Ryder, P.D.; Mills, L.R.; Laughlin, C.P.

    1978-01-01

    A potentiometric-surface map of the Southwest Florida Water Management District depicts the annual high water-level period. Potentiometric levels increased 15 to 30 feet between May 1977 and September 1977 in the citrus and farming sections of southeastern Hillsborough, northern Hardee, and southwestern Polk Counties. These areas are widely affected by pumpage for irrigation and have the greatest range in water-level fluctuations between the low and high water-level periods. Water-level rises in coastal, northern, and southern areas of the Water Management District ranged from 0 to 15 feet. (Woodard-USGS)

  11. 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.

  12. Photoelectron Spectroscopy and Theoretical Studies of Anion-pi Interactions: Binding Strength and Anion Specificity

    SciTech Connect

    Zhang, Jian; Zhou, Bin; Sun, Zhenrong; Wang, Xue B.

    2015-01-01

    illustrates that size-selective photoelectron spectroscopy combined with theoretical calculations represent a powerful technique to probe intrinsic anion–π interactions and has potential to provide quantitative guest-host molecular binding strengths and unravel fundamental insights in specific anion recognitions.

  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. 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. PMID:18970248

  15. Pu Anion Exchange Process Intensification

    SciTech Connect

    Taylor-Pashow, K.

    2015-10-08

    This project seeks to improve the efficiency of the plutonium anion-exchange process for purifying Pu through the development of alternate ion-exchange media. The objective of the project in FY15 was to develop and test a porous foam monolith material that could serve as a replacement for the current anion-exchange resin, Reillex® HPQ, used at the Savannah River Site (SRS) for purifying Pu. The new material provides advantages in efficiency over the current resin by the elimination of diffusive mass transport through large granular resin beads. By replacing the large resin beads with a porous foam there is much more efficient contact between the Pu solution and the anion-exchange sites present on the material. Several samples of a polystyrene based foam grafted with poly(4-vinylpyridine) were prepared and the Pu sorption was tested in batch contact tests.

  16. The force field for imidazolium-based ionic liquids: Novel anions with polar residues

    NASA Astrophysics Data System (ADS)

    Fileti, Eudes Eterno; Chaban, Vitaly V.

    2015-07-01

    Many molecules can be converted into ions via relatively simple procedures. These ions can be combined into ionic liquids (ILs). We develop a new force field (FF) for the seven selected AAILs comprising 1-ethyl-3-methylimidazolium cation and amino acid anions with polar residues. All anions were obtained via deprotonation of carboxyl group in analogy with acetate anion. We account for peculiar interactions between the anion and the cation by fitting electrostatic potential for an ion pair, in contrast to isolated ions. Furthermore, we account for hydrogen bonds obtained via electronic structure consideration. The developed model fosters computational investigation of ionic liquids.

  17. Spurious Hyperchloremia and Negative Anion Gap in a Child with Refractory Epilepsy

    PubMed Central

    Chegondi, Madhuradhar; Totapally, Balagangadhar R.

    2016-01-01

    We report a case with spurious hyperchloremia with negative anion gap in a child who was taking potassium bromide for refractory epilepsy. Blood chemistry showed a high chloride level (171 mEq/L) and a negative anion gap (−52 mEq/L). Plasma chloride concentration is measured by an ion-selective electrode method; however the presence of other anions like bromide and iodides can interfere with chloride level and largely overestimates the chloride concentration. Thus hyperchloremia with a negative anion gap is a clue to the diagnosis of halides like bromide and iodide ingestion. PMID:26981292

  18. An estimated potentiometric surface of the Death Valley region, Nevada and California, developed using geographic information system and automated interpolation techniques

    SciTech Connect

    D`Agnese, F.A.; Faunt, C.C.; Turner, A.K.

    1998-07-01

    An estimated potentiometric surface was constructed for the Death Valley region, Nevada and California, from numerous, disparate data sets. The potentiometric surface was required for conceptualization of the ground-water flow system and for construction of a numerical model to aid in the regional characterization for the Yucca Mountain repository. Because accurate, manual extrapolation of potentiometric levels over large distances is difficult, a geographic-information-system method was developed to incorporate available data and apply hydrogeologic rules during contour construction. Altitudes of lakes, springs, and wetlands, interpreted as areas where the potentiometric surface intercepts the land surface, were combined with water levels from well data. Because interpreted ground-water recharge and discharge areas commonly coincide with groundwater basin boundaries, these areas also were used to constrain a gridding algorithm and to appropriately place local maxima and minima in the potentiometric-surface map. The resulting initial potentiometric surface was examined to define areas where the algorithm incorrectly extrapolated the potentiometric surface above the land surface. A map of low-permeability rocks overlaid on the potentiometric surface also indicated areas that required editing based on hydrogeologic reasoning. An interactive editor was used to adjust generated contours to better represent the natural water table conditions, such as large hydraulic gradients and troughs, or ``vees``. The resulting estimated potentiometric-surface map agreed well with previously constructed maps. Potentiometric-surface characteristics including potentiometric-surface mounds and depressions, surface troughs, and large hydraulic gradients were described.

  19. A bidentate Lewis acid with a telluronium ion as an anion-binding site

    NASA Astrophysics Data System (ADS)

    Zhao, Haiyan; Gabbaï, François P.

    2010-11-01

    The search for receptors that can selectively capture small and potentially toxic anions in protic media has sparked a renewed interest in the synthesis and anion-binding properties of polydentate Lewis acids. Seeking new paradigms to enhance the anion affinities of such systems, we synthesized a bidentate Lewis acid that contains a boryl and a telluronium moiety as Lewis acidic sites. Anion-complexation studies indicate that this telluronium borane displays a high affinity for fluoride in methanol. Structural and computational studies show that the unusual fluoride affinity of this bidentate telluronium borane can be correlated with the formation of a B-F --> Te chelate motif supported by a strong lone-pair(F) --> σ*(Te-C) donor-acceptor interaction. These results, which illustrate the viability of heavier chalcogenium centres as anion-binding sites, allow us to introduce a novel strategy for the design of polydentate Lewis acids with enhanced anion affinities.

  20. Chloride-Anion-Templated Synthesis of a Strapped-Porphyrin-Containing Catenane Host System.

    PubMed

    Brown, Asha; Langton, Matthew J; Kilah, Nathan L; Thompson, Amber L; Beer, Paul D

    2015-12-01

    The synthesis, structure and anion-recognition properties of a new strapped-porphyrin-containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor-acceptor and coordinative pyridine-zinc interactions. The [2]catenane incorporates a three-dimensional, hydrogen-bond-donating anion-binding pocket; solid-state structural analysis of the catenane⋅chloride complex reveals that the chloride anion is encapsulated within the catenane's interlocked binding cavity through six convergent CH⋅⋅⋅⋅Cl and NH⋅⋅⋅Cl hydrogen-bonding interactions and solution-phase (1) H NMR titration experiments demonstrate that this complementary hydrogen-bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution. PMID:26508679

  1. Chloride-Anion-Templated Synthesis of a Strapped-Porphyrin-Containing Catenane Host System

    PubMed Central

    Brown, Asha; Langton, Matthew J; Kilah, Nathan L; Thompson, Amber L; Beer, Paul D

    2015-01-01

    The synthesis, structure and anion-recognition properties of a new strapped-porphyrin-containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor–acceptor and coordinative pyridine–zinc interactions. The [2]catenane incorporates a three-dimensional, hydrogen-bond-donating anion-binding pocket; solid-state structural analysis of the catenane⋅chloride complex reveals that the chloride anion is encapsulated within the catenane’s interlocked binding cavity through six convergent CH⋅⋅⋅⋅Cl and NH⋅⋅⋅Cl hydrogen-bonding interactions and solution-phase 1H NMR titration experiments demonstrate that this complementary hydrogen-bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution. PMID:26508679

  2. 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)

  3. 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.

  4. 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…

  5. 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. PMID:27444048

  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. 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…

  8. 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 ...

  9. Design and Evaluation of Potentiometric Principles for Bladder Volume Monitoring: A Preliminary Study

    PubMed Central

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

    2015-01-01

    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. PMID:26039421

  10. 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.

  11. Potentiometric study of reaction between periodate and iodide as their tetrabutylammonium salts in chloroform. Application to the determination of iodide and potentiometric detection of end points in acid-base titrations in chloroform.

    PubMed

    Pournaghi-Azar, M H; Farhadi, K

    1995-03-01

    A potentiometric method for the titration of tetrabutylammonium iodide (TBAI) in chloroform using tetrabutylammonium periodate (TBAPI) as a strong and suitable oxidizing reagent is described. The potentiometric conditions were optimized and the equilibrium constants of the reactions occurring during the titration were determined. The method was used for the determination of iodide both in chloroform and aqueous solutions after extraction into chloroform as ion-association with tetraphenylarsonium. The reaction between TBAPI and TBAI was also used as acid indicator for the potentiometric detection of end points of acid-base titrations in chloroform.

  12. Potentiometric levels and water quality in the aquifers underlying Belvidere, Illinois, 1993-96

    USGS Publications Warehouse

    Mills, Patrick C.; Thomas, C.A.; Brown, T.A.; Yeskis, D.J.; Kay, R.T.

    1999-01-01

    In 1992, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency (USEPA), began a study of the hydrogeology and water quality of the aquifers underlying the vicinity of Belvidere, Boone County, Ill. Previously, volatile organic compounds (VOC's) and other constituents of industrial origin were detected in one or more ground-water samples from about 100 of the approximately 700 monitoring and water-supply wells in the area, including the 8 municipal wells in Belvidere. A glacial drift aquifer underlies at least 50 percent of the 80-square-mile study area; bedrock aquifers that underlie virtually all of the study area include the Galena-Platteville, St. Peter Sandstone, Ordovician, and Cambrian-Ordovician aquifers. During 1993, water levels were measured in 152 wells and water-quality samples were collected from 97 wells distributed throughout the study area. During 1994-96, similar data were collected from 31 wells. Potentiometric levels in the glacial drift and Galena-Platteville aquifers are similar and range from about 750 to 900 feet above sea level. The potentiometric surfaces of the aquifers are subdued representations of the land surface. Horizontal ground-water flow in the aquifers primarily is towards the Kishwaukee River, which flows through the central part of the study area, and its principal tributaries. Vertical ground-water flow appears to be downward at most locations in the study area, particularly in the urbanized areas affected by pumping of the Belvidere municipal wells and upland areas remote from the principal surface-water drainages. Flow appears to be upward between the Galena-Platteville and glacial drift aquifers where ground water discharges to the Kishwaukee River and its principal tributaries. All water samples were analyzed for VOC's. Selected samples also were analyzed for trace metals, cyanide, semivolatile organic compounds, or other constituents. VOC's were detected in samples from 50 wells (52

  13. 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

  14. Anion binding in biological systems

    NASA Astrophysics Data System (ADS)

    Feiters, Martin C.; Meyer-Klaucke, Wolfram; Kostenko, Alexander V.; Soldatov, Alexander V.; Leblanc, Catherine; Michel, Gurvan; Potin, Philippe; Küpper, Frithjof C.; Hollenstein, Kaspar; Locher, Kaspar P.; Bevers, Loes E.; Hagedoorn, Peter-Leon; Hagen, Wilfred R.

    2009-11-01

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L3 (2p3/2) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  15. Anion Complexes with Tetrazine-Based Ligands: Formation of Strong Anion-π Interactions in Solution and in the Solid State.

    PubMed

    Savastano, Matteo; Bazzicalupi, Carla; Giorgi, Claudia; García-Gallarín, Celeste; López de la Torre, Maria Dolores; Pichierri, Fabio; Bianchi, Antonio; Melguizo, Manuel

    2016-08-15

    Ligands L1 and L2, consisting of a tetrazine ring decorated with two morpholine pendants of different lengths, show peculiar anion-binding behaviors. In several cases, even the neutral ligands, in addition to their protonated HL(+) and H2L(2+) (L = L1 and L2) forms, bind anions such as F(-), NO3(-), PF6(-), ClO4(-), and SO4(2-) to form stable complexes in water. The crystal structures of H2L1(PF6)2·2H2O, H2L1(ClO4)2·2H2O, H2L2(NO3)2, H2L2(PF6)2·H2O, and H2L2(ClO4)2·H2O show that anion-π interactions are pivotal for the formation of these complexes, although other weak forces may contribute to their stability. Complex stability constants were determined by means of potentiometric titration in aqueous solution at 298.1 K, while dissection of the free-energy change of association (ΔG°) into its enthalpic (ΔH°) and entropic (TΔS°) components was accomplished by means of isothermal titration calorimetry measurements. Stability constants are poorly regulated by anion-ligand charge-charge attraction. Thermodynamic data show that the formation of complexes with neutral ligands, which are principally stabilized by anion-π interactions, is enthalpically favorable (-ΔG°, 11.1-17.5 kJ/mol; ΔH°, -2.3 to -0.5 kJ/mol; TΔS°, 9.0-17.0 kJ/mol), while for charged ligands, enthalpy changes are mostly unfavorable. Complexation reactions are invariably promoted by large and favorable entropic contributions. The importance of desolvation phenomena manifested by such thermodynamic data was confirmed by the hydrodynamic results obtained by means of diffusion NMR spectroscopy. In the case of L2, complexation equilibria were also studied in a 80:20 (v/v) water/ethanol mixture. In this mixed solvent of lower dielectric constant than water, the stability of anion complexes decreases, relative to water. Solvation effects, mostly involving the ligand, are thought to be responsible for this peculiar behavior. PMID:27454810

  16. Anion Complexes with Tetrazine-Based Ligands: Formation of Strong Anion-π Interactions in Solution and in the Solid State.

    PubMed

    Savastano, Matteo; Bazzicalupi, Carla; Giorgi, Claudia; García-Gallarín, Celeste; López de la Torre, Maria Dolores; Pichierri, Fabio; Bianchi, Antonio; Melguizo, Manuel

    2016-08-15

    Ligands L1 and L2, consisting of a tetrazine ring decorated with two morpholine pendants of different lengths, show peculiar anion-binding behaviors. In several cases, even the neutral ligands, in addition to their protonated HL(+) and H2L(2+) (L = L1 and L2) forms, bind anions such as F(-), NO3(-), PF6(-), ClO4(-), and SO4(2-) to form stable complexes in water. The crystal structures of H2L1(PF6)2·2H2O, H2L1(ClO4)2·2H2O, H2L2(NO3)2, H2L2(PF6)2·H2O, and H2L2(ClO4)2·H2O show that anion-π interactions are pivotal for the formation of these complexes, although other weak forces may contribute to their stability. Complex stability constants were determined by means of potentiometric titration in aqueous solution at 298.1 K, while dissection of the free-energy change of association (ΔG°) into its enthalpic (ΔH°) and entropic (TΔS°) components was accomplished by means of isothermal titration calorimetry measurements. Stability constants are poorly regulated by anion-ligand charge-charge attraction. Thermodynamic data show that the formation of complexes with neutral ligands, which are principally stabilized by anion-π interactions, is enthalpically favorable (-ΔG°, 11.1-17.5 kJ/mol; ΔH°, -2.3 to -0.5 kJ/mol; TΔS°, 9.0-17.0 kJ/mol), while for charged ligands, enthalpy changes are mostly unfavorable. Complexation reactions are invariably promoted by large and favorable entropic contributions. The importance of desolvation phenomena manifested by such thermodynamic data was confirmed by the hydrodynamic results obtained by means of diffusion NMR spectroscopy. In the case of L2, complexation equilibria were also studied in a 80:20 (v/v) water/ethanol mixture. In this mixed solvent of lower dielectric constant than water, the stability of anion complexes decreases, relative to water. Solvation effects, mostly involving the ligand, are thought to be responsible for this peculiar behavior.

  17. Potentiometric surface of the Upper Floridan aquifer in the Suwannee River Water Management District, Florida, May 2005

    USGS Publications Warehouse

    Verdi, Richard Jay; Sepulveda, A. Alejandro

    2006-01-01

    Introduction: This map depicts the potentiometric surface of the Upper Floridan aquifer in the Suwannee River Water Management District (SRWMD) during May 2005. Potentiometric contours are based on water-level measurements taken at more than 400 observation wells during the period of May 1-31, 2005. A potentiometric surface is defined as an areal representation of the levels to which water would rise in tightly cased wells open to an aquifer (Fetter, 1988). Since these water-level measurements from the Upper Floridan aquifer were taken over a 31-day period, they do not represent a 'snapshot' of the conditions at a specific date and time.

  18. 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.

  19. Revised potentiometric-surface map, Yucca Mountain and vicinity, Nevada; Water-resources investigations report 93-4000

    SciTech Connect

    Ervin, E.M.; Luckey, R.R.; Burkhardt, D.J.

    1994-05-01

    This report presents a revised potentiometric-surface map based mainly on the 1988 average water levels at Yucca Mountain and the nearby vicinity extending from Crater Flat to Jackass Flats. Discussion includes an explanation of the revised potentiometric-surface map, an examination of yearly trends in the water levels, and adjustments for temperature and density effects in the deeper wells. Report scope focuses on the potentiometric surface of the uppermost saturated zone in the Tertiary volcanic rocks at Yucca Mountain. Some information, related to the underlying Paleozoic carbonate aquifer, pertinent to the volcanic flow system, is presented.

  20. Optimizing potentiometric ionophore and electrode design for environmental on-site control of antibiotic drugs: application to sulfamethoxazole.

    PubMed

    Almeida, S A A; Truta, Liliana A A N A; Queirós, Raquel B; Montenegro, M C B S M; Cunha, Alexandre L; Sales, M G F

    2012-05-15

    Potentiometric sensors are typically unable to carry out on-site monitoring of environmental drug contaminants because of their high limits of detection (LODs). Designing a novel ligand material for the target analyte and managing the composition of the internal reference solution have been the strategies employed here to produce for the first time a potentiometric-based direct reading method for an environmental drug contaminant. This concept has been applied to sulfamethoxazole (SMX), one of the many antibiotics used in aquaculture practices that may occur in environmental waters. The novel ligand has been produced by imprinting SMX on the surface of graphitic carbon nanostructures (CN)<500 nm. The imprinted carbon nanostructures (ICN) were dispersed in plasticizer and entrapped in a PVC matrix that included (or not) a small amount of a lipophilic additive. The membrane composition was optimized on solid-contact electrodes, allowing near-Nernstian responses down to 5.2 μg/mL and detecting 1.6 μg/mL. The membranes offered good selectivity against most of the ionic compounds in environmental water. The best membrane cocktail was applied on the smaller end of a 1000 μL micropipette tip made of polypropylene. The tip was then filled with inner reference solution containing SMX and chlorate (as interfering compound). The corresponding concentrations were studied for 1 × 10(-5) to 1 × 10(-10) and 1 × 10(-3) to 1 × 10(-8)mol/L. The best condition allowed the detection of 5.92 ng/L (or 2.3 × 10(-8)mol/L) SMX for a sub-Nernstian slope of -40.3 mV/decade from 5.0 × 10(-8) to 2.4 × 10(-5)mol/L. The described sensors were found promising devices for field applications. The good selectivity of the sensory materials together with a carefully selected composition for the inner reference solution allowed LODs near the nanomolar range. Both solid-contact and "pipette tip"-based sensors were successfully applied to the analysis of aquaculture waters.

  1. Characterization of Sea Lettuce Surface Functional Groups by Potentiometric Titrations

    NASA Astrophysics Data System (ADS)

    Ebling, A. M.; Schijf, J.

    2008-12-01

    In pursuit of our ultimate goal to better understand the prodigious capacity of the marine macroalga Ulva lactuca (sea lettuce) for adsorbing a broad range of dissolved trace metals from seawater, we performed an initial characterization of its surface functional groups. Specifically, the number of distinct functional groups as well as their individual bulk concentrations and acid dissociation constants (pKas) were determined by potentiometric titrations in NaCl solutions of various ionic strengths (I = 0.01-5.0 M), under inert nitrogen atmosphere at 25°C. Depending on the ionic strength, Ulva samples were manually titrated down to pH 2 or 3 with 1 N HCl and then up to pH 10 with 1 N NaOH in steps of 0.1-0.2 units, continuously monitoring pH with a glass combination electrode. Titrations of a dehydrated Ulva standard reference material (BCR-279) were compared with fresh Ulva tissue cultured in our laboratory. A titration in filtered natural seawater was also compared with one in an NaCl solution of equal ionic strength. Equilibrium constants for the ionization of water in NaCl solutions as a function of ionic strength were obtained from the literature. Fits to the titration data ([H]T vs. pH) were performed with the FITEQL4.0 computer code using non-electrostatic 3-, 4-, and 5-site models, either by fixing ionic strength at its experimental value or by allowing it to be extrapolated to zero, while considering all functional group pKas and bulk concentrations as adjustable parameters. Since pKas and bulk concentrations were found to be strongly correlated, the latter were also fixed in some cases to further constrain the pKas. Whereas these calculations are currently ongoing, preliminary results point to three, possibly four, functional groups with pKas of about 4.1, 6.3, and 9.5 at I = 0. Bulk concentrations of the three groups are very similar, about 5-6×10-4 mol/g based on dry weight, which suggests that all are homogeneously distributed over the surface and

  2. An intracellular anion channel critical for pigmentation

    PubMed Central

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-01-01

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation. DOI: http://dx.doi.org/10.7554/eLife.04543.001 PMID:25513726

  3. An intracellular anion channel critical for pigmentation.

    PubMed

    Bellono, Nicholas W; Escobar, Iliana E; Lefkovith, Ariel J; Marks, Michael S; Oancea, Elena

    2014-01-01

    Intracellular ion channels are essential regulators of organellar and cellular function, yet the molecular identity and physiological role of many of these channels remains elusive. In particular, no ion channel has been characterized in melanosomes, organelles that produce and store the major mammalian pigment melanin. Defects in melanosome function cause albinism, characterized by vision and pigmentation deficits, impaired retinal development, and increased susceptibility to skin and eye cancers. The most common form of albinism is caused by mutations in oculocutaneous albinism II (OCA2), a melanosome-specific transmembrane protein with unknown function. Here we used direct patch-clamp of skin and eye melanosomes to identify a novel chloride-selective anion conductance mediated by OCA2 and required for melanin production. Expression of OCA2 increases organelle pH, suggesting that the chloride channel might regulate melanin synthesis by modulating melanosome pH. Thus, a melanosomal anion channel that requires OCA2 is essential for skin and eye pigmentation. PMID:25513726

  4. Water-level data from wells and test holes through 1991 and potentiometric contours as of 1991 for Yucca Flat, Nevada Test Site, Nye County, Nevada

    SciTech Connect

    Hale, G.S.; Trudeau, D.A.; Savard, C.S.

    1995-12-01

    The underground nuclear testing program of the US Department of Energy (USDOE) takes place at the Nevada Test Site (NTS), about 65 mi north-west of Las Vegas, Nevada. Underground nuclear tests at Yucca Flat, one of the USDOE test areas at NTS, have affected hydrologic conditions, including groundwater levels. The purpose of this map report, prepared in cooperation with USDOE, is to present selected water-level data collected from wells and test holes through December 1991, and to show potentiometric contours representing 1991 water-table conditions in the Yucca Flat area. The more generic term, potentiometric contours, is used herein rather than ``water-table contours`` because the hydrologic units contributing water to wells and test holes may not accurately represent the water table. The water table is that surface in an unconfined water body at which the pressure is atmospheric. It is defined by the altitude at which non- perched ground water is first found in wells and test holes. Perched ground water is defined as unconfined ground water separated from an underlying body of ground water by an unsaturated zone. This map report updates information on water levels in some wells and test holes and the resulting water-table contours in rocks of Cenozoic and Paleozoic age shown by Doty and Thordarson for 1980 conditions.

  5. Ion exchange polymers for anion separations

    DOEpatents

    Jarvinen, G.D.; Marsh, S.F.; Bartsch, R.A.

    1997-09-23

    Anion exchange resins including at least two positively charged sites and a well-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

  6. Ion exchange polymers for anion separations

    DOEpatents

    Jarvinen, Gordon D.; Marsh, S. Fredric; Bartsch, Richard A.

    1997-01-01

    Anion exchange resins including at least two positively charged sites and a ell-defined spacing between the positive sites are provided together with a process of removing anions or anionic metal complexes from aqueous solutions by use of such resins. The resins can be substituted poly(vinylpyridine) and substituted polystyrene.

  7. Anion-templated supramolecular C3 assembly for efficient inclusion of charge-dispersed anions into hydrogen-bonded networks.

    PubMed

    Užarević, Krunoslav; Đilović, Ivica; Bregović, Nikola; Tomišić, Vladislav; Matković-Čalogović, Dubravka; Cindrić, Marina

    2011-09-19

    The binding properties and conformational adaptability of a known nitrate/sulfate receptor N,N'-3-azapentane-1,5-bis[3-(1-aminoethylidene)-6-methyl-3H-pyran-2,4-dione] (L) toward various charge-dispersed monoanions (HSO(3)(-), ClO(4)(-), IO(4)(-), PF(6)(-), and SbF(6)(-)) are considered. These anions template the folding of three HL(+) species through a self-assembly process into a new hollow supramolecular trication. During the self-assembly, all strong hydrogen-bond donors of the podand become coordinatively saturated by interactions with the oxo functionalities from other HL(+) molecules. In that way, only the weak hydrogen-bond-donating groups in the exterior part of the receptor are accessible for anion binding. The investigated anions are accommodated in the hydrophobic pockets of the isomorphous hydrogen-bonded frameworks, which serve as a basis for selective crystallization from the highly competitive anion/solvent systems. This behavior is discussed in terms of size and geometry of the anions as well as the receptor's coordination capabilities to provide the most favorable surroundings for guest inclusion both in solution and in the solid state.

  8. The anion-binding polyanion: a molecular cobalt vanadium oxide with anion-sensitive visual response.

    PubMed

    Seliverstov, Andrey; Forster, Johannes; Heiland, Magdalena; Unfried, Johannes; Streb, Carsten

    2014-07-25

    An anionic molecular cobalt vanadium oxide cluster, (n-Bu4N)3[Co(AcO)V4O12] and its use as anion binding site is reported. Cluster formation is controlled by an anion-dependent dynamic solution equilibrium. Reversible anion binding in solution leads to significant spectral changes, allowing the ratiometric optical detection of the anion concentration in situ, even under harsh thermal conditions (T = 90 °C). Comparative studies showed that the spectral response is dependent on the type of anion so that carboxylates, weakly coordinating anions and halides can be distinguished.

  9. Synthesis, structure, anion binding, and sensing by calix[4]pyrrole isomers.

    PubMed

    Nishiyabu, Ryuhei; Palacios, Manuel A; Dehaen, Wim; Anzenbacher, Pavel

    2006-09-01

    The synthesis, structure, and anion binding properties of chromogenic octamethylcalix[4]pyrroles (OMCPs) and their N-confused octamethylcalix[4]pyrrole isomers (NC-OMCPs) containing an inverted pyrrole ring connected via alpha'- and beta-positions are described. X-ray diffraction analyses proved the structures of two synthesized isomeric pairs of OMCPs and NC-OMCPs. The addition of anions to solutions of chromogenic OMCPs and NC-OMCPs resulted in different colors suggesting different anion-binding behaviors. The chromogenic NC-OMCPs showed significantly stronger anion-induced color changes compared to the corresponding chromogenic OMCP, and the absorption spectroscopy titrations indicated that chromogenic OMCPs and NC-OMCPs also possess different anion binding selectivity. Detailed NMR studies revealed that this rather unusual feature stems from a different anion-binding mode in OMCPs and NC-OMCPs, one where the beta-pyrrole C-H of the inverted pyrrole moiety participates in the hydrogen-bonded anion-NC-OMCP complex. Preliminary colorimetric microassays using synthesized chromogenic calixpyrroles embedded in partially hydrophilic polyurethane matrices allow for observation of analyte-specific changes in color when the anions are administered in the form of their aqueous solutions and in the presence of weakly competing anions. PMID:16939273

  10. A new potentiometric SO2 sensor based on Li3PO4 electrolyte film and its response characteristics

    NASA Astrophysics Data System (ADS)

    Wang, H.; Liu, Z.; Chen, D.; Jiang, Z.

    2015-07-01

    A potentiometric SO2 gas sensor based on Li3PO4 solid electrolyte has been developed using Au as the reference electrode and Li2SO4/V2O5 as the sensing electrode. The Li3PO4 film was deposited on Al2O3 substrate by resistance heating evaporation. Two Au films with designed patterns were formed on the Li3PO4 film by micro-fabrication technologies. The sensing electrode covers one electrode partly using thick-film technology. The electromotive force values between the sensing electrode and the reference electrode were measured and various characteristics were studied including sensitivity, response characteristics, and stability and selectivity. According to the results, we conclude that an optimal working temperature of the SO2 sensor is 500 °C, the measurement range is 0-100 ppm, the sensitivity is about 32.47 mV/dec, the response and the recovery time is about 5 min and 10 min, respectively. And the stability and the selectivity of the sensor are good, making it have potential in SO2 measurement of living environment.

  11. Polymerization of anionic wormlike micelles.

    PubMed

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles.

  12. Polymerization of anionic wormlike micelles.

    PubMed

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles. PMID:16430253

  13. Anion-induced urea deprotonation.

    PubMed

    Boiocchi, Massimo; Del Boca, Laura; Esteban-Gómez, David; Fabbrizzi, Luigi; Licchelli, Maurizio; Monzani, Enrico

    2005-05-01

    The urea-based receptor 1 (1-(7-nitrobenzo[1,2,5]oxadiazol-4-yl)-3-(4-nitrophenyl)urea, L--H), interacts with X- ions in MeCN, according to two consecutive steps: 1) formation of a hydrogen-bond complex [L--H...X]-; 2) deprotonation of L--H to give L- and [HX2]-, as shown by spectrophotometric and 1H NMR titration experiments. Step 2) takes place with more basic anions (fluoride, carboxylates, dihydrogenphosphate), while less basic anions (Cl-, NO2-, NO3-) do not induce proton transfer. On crystallisation from a solution containing L--H and excess Bu4NF, the tetrabutylammonium salt of the deprotonated urea derivative (Bu4N[L]) was isolated and its crystal and molecular structure determined. PMID:15770711

  14. Anion Solvation in Carbonate Electrolytes

    SciTech Connect

    Zhang, Zhengcheng

    2015-11-16

    With the correlation between Li+ solvation and interphasial chemistry on anodes firmly established in Li-ion batteries, the effect of cation–solvent interaction has gone beyond bulk thermodynamic and transport properties and become an essential element that determines the reversibility of electrochemistry and kinetics of Li-ion intercalation chemistries. As of now, most studies are dedicated to the solvation of Li+, and the solvation of anions in carbonate-based electrolytes and its possible effect on the electrochemical stability of such electrolytes remains little understood. As a mirror effort to prior Li+ solvation studies, this work focuses on the interactions between carbonate-based solvents and two anions (hexafluorophosphate, PF6–, and tetrafluoroborate, BF4–) that are most frequently used in Li-ion batteries. The possible correlation between such interaction and the interphasial chemistry on cathode surface is also explored.

  15. Aza compounds as anion receptors

    DOEpatents

    Lee, Hung Sui; Yang, Xiao-Qing; McBreen, James

    1998-01-06

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li.sup.+ ion in alkali metal batteries.

  16. Aza compounds as anion receptors

    DOEpatents

    Lee, H.S.; Yang, X.Q.; McBreen, J.

    1998-01-06

    A family of aza-ether based compounds including linear, multi-branched and aza-crown ethers is provided. When added to non-aqueous battery electrolytes, the family of aza-ether based compounds acts as neutral receptors to complex the anion moiety of the electrolyte salt thereby increasing the conductivity and the transference number of Li{sup +} ion in alkali metal batteries. 3 figs.

  17. Determination of tartaric acid in wines by FIA with tubular tartrate-selective electrodes.

    PubMed

    Sales, M G; Amaral, C E; Matos, C M

    2001-03-01

    A flow injection analysis (FIA) system comprising a tartrate-(TAT) selective electrode has been developed for determination of tartaric acid in wines. Several electrodes constructed for this purpose had a PVC membrane with a complex of quaternary ammonium and TAT as anion exchanger, a phenol derivative as additive, and a more or less polar mediator solvent. Characterization of the electrodes showed behavior was best for membranes with o-nitrophenyl octyl ether as solvent. On injection of 500 microL into a phosphate buffer carrier (pH = 3.1; ionic strength 10(-2) mol/L) flowing at 3 mL/min, the slope was 58.06 +/- 0.6 with a lower limit of linear range of 5.0 x 10(-4) mol/L TAT and R2 = 0.9989. The interference of several species, e.g. chloride, bromide, iodide, nitrate, gallic acid, tannin, sucrose, glucose, fructose, acetate, and citrate, was evaluated in terms of potentiometric selectivity coefficients. The Hofmeister series was followed for inorganic species and the most interfering organic ion was citrate. When red and white wines were analyzed and the results compared with those from an independent method they were found to be accurate, with relative standard deviations below 5.0%.

  18. Hopping-mediated anion transport through a mannitol-based rosette ion channel.

    PubMed

    Saha, Tanmoy; Dasari, Sathish; Tewari, Debanjan; Prathap, Annamalai; Sureshan, Kana M; Bera, Amal K; Mukherjee, Arnab; Talukdar, Pinaki

    2014-10-01

    Artificial anion selective ion channels with single-file multiple anion-recognition sites are rare. Here, we have designed, by hypothesis, a small molecule that self-organizes to form a barrel rosette ion channel in the lipid membrane environment. Being amphiphilic in nature, this molecule forms nanotubes through intermolecular hydrogen bond formation, while its hydrophobic counterpart is stabilized by hydrophobic interactions in the membrane. The anion selectivity of the channel was investigated by fluorescence-based vesicle assay and planar bilayer conductance measurements. The ion transport by a modified hopping mechanism was demonstrated by molecular dynamics simulation studies. PMID:25203165

  19. Cystic fibrosis transmembrane conductance regulator (CFTR) anion binding as a probe of the pore.

    PubMed Central

    Mansoura, M K; Smith, S S; Choi, A D; Richards, N W; Strong, T V; Drumm, M L; Collins, F S; Dawson, D C

    1998-01-01

    We compared the effects of mutations in transmembrane segments (TMs) TM1, TM5, and TM6 on the conduction and activation properties of the cystic fibrosis transmembrane conductance regulator (CFTR) to determine which functional property was most sensitive to mutations and, thereby, to develop a criterion for measuring the importance of a particular residue or TM for anion conduction or activation. Anion substitution studies provided strong evidence for the binding of permeant anions in the pore. Anion binding was highly sensitive to point mutations in TM5 and TM6. Permeability ratios, in contrast, were relatively unaffected by the same mutations, so that anion binding emerged as the conduction property most sensitive to structural changes in CFTR. The relative insensitivity of permeability ratios to CFTR mutations was in accord with the notion that anion-water interactions are important determinants of permeability selectivity. By the criterion of anion binding, TM5 and TM6 were judged to be likely to contribute to the structure of the anion-selective pore, whereas TM1 was judged to be less important. Mutations in TM5 and TM6 also dramatically reduced the sensitivity of CFTR to activation by 3-isobutyl 1-methyl xanthine (IBMX), as expected if these TMs are intimately involved in the physical process that opens and closes the channel. PMID:9512029

  20. Anionic Forensic Signatures for Sample Matching of Potassium Cyanide Using High Performance Ion Chromatography and Chemometrics

    SciTech Connect

    Fraga, Carlos G.; Farmer, Orville T.; Carman, April J.

    2011-01-30

    Potassium cyanide, a known poison, was used a model compound to determine the feasibility of using anionic impurities as a forensic signature for matching KCN samples back to their source. In this study, portions of eight KCN stocks originating from four countries were separately dissolved in water and analyzed by high performance ion chromatography (HPIC) using an anion exchange column and conductivity detection. Sixty KCN aqueous samples were produced from the eight stocks and analyzed for 11anionic impurities. Hierarchal cluster analysis and principal component analysis were used to demonstrate that KCN samples cluster according to source based on the concentrations of their anionic impurities. The F-ratio method and degree-of-class separation (DCS) were used for feature selection on a training set of KCN samples in order to optimize sample clustering. The optimal subset of anions needed for sample classification was determined to be sulfate, oxalate, phosphate, and an unknown anion named unk5. Using K-nearest neighbors (KNN) and the optimal subset of anions, KCN test samples from different KCN stocks were correctly determined to be manufactured in the United States. In addition, KCN samples from stocks manufactured in Belgium, Germany, and the Czech Republic were all correctly matched back to their original stocks because each stock had a unique anionic impurity profile. The application of the F-ratio method and DCS for feature selection improved the accuracy and confidence of sample classification by KNN.

  1. Poly(phenylene)-based anion exchange membrane

    DOEpatents

    Hibbs, Michael; Cornelius, Christopher J.; Fujimoto, Cy H.

    2011-02-15

    A poly(phenylene) compound of copolymers that can be prepared with either random or multiblock structures where a first polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 2 pendant phenyl groups and 4 pendant tolyl groups and the second polymer has a repeat unit with a structure of four sequentially connected phenyl rings with a total of 6 pendant phenyl groups. The second polymer has chemical groups attached to some of the pendant phenyl groups selected from CH.sub.3, CH.sub.2Br, and CH.sub.2N(CH.sub.3).sub.3Br groups. When at least one group is CH.sub.2N(CH.sub.3).sub.3Br, the material functions as an anion exchange membrane.

  2. Model Catalysis of Ammonia Synthesis ad Iron-Water Interfaces - ASum Frequency Generation Vibrational Spectroscopic Study of Solid-GasInterfaces and Anion Photoelectron Spectroscopic Study of Selected Anionclusters

    SciTech Connect

    Ferguson, Michael James

    2005-01-01

    the free OH or free OD. From the absence of SFG spectra of ice-like structure we conclude that surface hydroxides are formed and no liquid water is present on the surface. Other than model catalysis, gas phase anion photoelectron spectroscopy of the Cl + H2 van der Waals well, silicon clusters, germanium clusters, aluminum oxide clusters and indium phosphide clusters were studied. The spectra help to map out the neutral potential energy surfaces of the clusters. For aluminum oxide, the structures of the anions and neutrals were explored and for silicon, germanium and indium phosphide the electronic structure of larger clusters was mapped out.

  3. Conformational NMR Study of Bistriazolyl Anion Receptors.

    PubMed

    Makuc, Damjan; Merckx, Tamara; Dehaen, Wim; Plavec, Janez

    2016-01-01

    Conformational features of pyridine- and pyrimidine-based bistriazolyl anion receptors dissolved in acetonitrile-d3 were assessed by multidimensional, heteronuclear NMR spectroscopy. NOESY correlation signals suggested preorganization of both host molecules in solution in the absence of anions. In addition, only a single set of signals was observed in the 1H NMR spectra, which suggested a symmetrical conformation of anion receptors or their conformational exchange that is fast on the NMR time-scale. Furthermore, the predominant conformations of the pyridine- and pyrimidine-based anion receptors are preserved upon addition of chloride, bromide, and acetate anions. Chemical shift changes observed upon addition of anions showed that the NH (thio)urea and triazole protons are involved in anion-receptor interactions through hydrogen bonding. PMID:27640375

  4. Gating mechanisms of a natural anion channelrhodopsin

    PubMed Central

    Sineshchekov, Oleg A.; Govorunova, Elena G.; Li, Hai; Spudich, John L.

    2015-01-01

    Anion channelrhodopsins (ACRs) are a class of light-gated channels recently identified in cryptophyte algae that provide unprecedented fast and powerful hyperpolarizing tools for optogenetics. Analysis of photocurrents generated by Guillardia theta ACR 1 (GtACR1) and its mutants in response to laser flashes showed that GtACR1 gating comprises two separate mechanisms with opposite dependencies on the membrane voltage and pH and involving different amino acid residues. The first mechanism, characterized by slow opening and fast closing of the channel, is regulated by Glu-68. Neutralization of this residue (the E68Q mutation) specifically suppressed this first mechanism, but did not eliminate it completely at high pH. Our data indicate the involvement of another, yet-unidentified pH-sensitive group X. Introducing a positive charge at the Glu-68 site (the E68R mutation) inverted the channel gating so that it was open in the dark and closed in the light, without altering its ion selectivity. The second mechanism, characterized by fast opening and slow closing of the channel, was not substantially affected by the E68Q mutation, but was controlled by Cys-102. The C102A mutation reduced the rate of channel closing by the second mechanism by ∼100-fold, whereas it had only a twofold effect on the rate of the first. The results show that anion conductance by ACRs has a fundamentally different structural basis than the relatively well studied conductance by cation channelrhodopsins (CCRs), not attributable to simply a modification of the CCR selectivity filter. PMID:26578767

  5. Separation and quantification of inulin in selected artichoke (Cynara scolymus L.) cultivars and dandelion (Taraxacum officinale WEB. ex WIGG.) roots by high-performance anion exchange chromatography with pulsed amperometric detection.

    PubMed

    Schütz, Katrin; Muks, Erna; Carle, Reinhold; Schieber, Andreas

    2006-12-01

    The profile of fructooligosaccharides and fructopolysaccharides in artichoke heads and dandelion roots was investigated. For this purpose, a suitable method for high-performance anion exchange chromatography with pulsed amperometic detection was developed. The separation of monomers, oligomers and polymers up to a chain length of 79 sugar residues was achieved in one single run. Glucose, fructose, sucrose and individual fructooligosaccharides (kestose, nystose, fructofuranosylnystose) were quantified in six different artichoke cultivars and in dandelion roots. The contents ranged from 12.9 g/kg DM to 71.7 g/kg DM for glucose, from 15.8 g/kg DM to 67.2 g/kg DM for fructose, and from 16.8 g/kg DM to 55.2 g/kg DM for sucrose in the artichoke heads. Kestose was the predominant fructooligosaccharide, followed by nystose and fructofuranosylnystose. In four cultivars fructofuranosylnystose was only detectable in traces and reached its maximum value of 3.6 g/kg DM in the cultivar Le Castel. Furthermore, an average degree of polymerization of 5.3 to 16.7 was calculated for the individual artichoke cultivars, which is noticeably lower than hitherto reported. In contrast, the contents of kestose, nystose and fructofuranosylnystose in dandelion root exceeded that of artichoke, reflecting the short chain characteristic of the inulin, which was confirmed by chromatographic analysis.

  6. Hydrogen bonding and molecular association in 2-(quinuclidinium)-butyric acid bromide hydrate studied by X-ray diffraction, DFT calculations, FTIR and NMR spectroscopy, and potentiometric titration

    NASA Astrophysics Data System (ADS)

    Dega-Szafran, Z.; Katrusiak, A.; Szafran, M.; Barczyński, P.

    2010-06-01

    The structure of 2-(quinuclidinium)-butyric acid bromide hydrate (QNBu·H 2O·HBr, 3) has been determined by X-ray diffraction, DFT calculations and characterized by FTIR and NMR spectroscopy. Crystals of 3 are monoclinic, space group P2 1. The water molecule interacts with the carboxylic group of 2-(quinuclidinium)-butyric acid and with the bromide anion by the COOH⋯OH 2 and HOH⋯Br hydrogen bonds of 2.575(3) and 3.293(2) Å, respectively. The structures of monomer ( 4) and dimeric cation ( 5) of the title complex have been optimized by the B3LYP/6-31G(d,p) approach, yielding conformations consistent with this in the crystal. The solid-state FTIR spectra of 3 and its deuterated analogue have been measured and compared with the theoretical spectrum of 4. The assignments of the observed and predicted bands have been proposed. The molecule of 3 has a chiral center at the C(9) atom, which is responsible for the non-magnetically equivalence of the α-ring and C(11)H 2 methylene protons in 1H NMR spectrum. The values of p Ka of quinuclidinium-acetate (quinuclidine betaine), 2-(quinuclidinium)-propionate and 2-(quinuclidinium)-butyrate have been determined by the potentiometric titration of their hydrohalides.

  7. Acidity constants in methanol/water mixtures of polycarboxylic acids used in drug salt preparations. Potentiometric determination of aqueous pKa values of quetiapine formulated as hemifumarate.

    PubMed

    Garrido, Gemma; Ràfols, Clara; Bosch, Elisabeth

    2006-05-01

    The acidic dissociation constants in a number of methanol/water mixtures of mono and polycarboxylic acids commonly used in the preparation of drug salts were determined. These solvent mixtures are usually used to determine the pKa of drugs of low aqueous solubility. However, when these drugs are prepared in salt form, the acid-base equilibria of both the basic drug and the counter-anion are involved in the potentiometric titration curves. In these instances, the inclusion of the pKa of acids as constant values in the curve fitting provides easy computation of the drug pKa without the need of any previous step to get the free base. As an application example, the aqueous pKa values of the quetiapine formulated as hemifumarate (Seroquel) were estimated by extrapolation from the experimental pKa in several methanol/water mixtures, which were then calculated according to the suitable constants of fumaric acid. The estimated aqueous pKa values of quetiapine are compared with those directly obtained in aqueous solution by potentiometry and by capillary electrophoresis.

  8. Nano- and microsized zeolites as a perspective material for potentiometric biosensors creation.

    PubMed

    Soldatkin, Oleksandr O; Shelyakina, Margaryta K; Arkhypova, Valentyna N; Soy, Esin; Kirdeciler, Salih Kaan; Ozansoy Kasap, Berna; Lagarde, Florence; Jaffrezic-Renault, Nicole; Akata Kurç, Burcu; Soldatkin, Alexei P; Dzyadevych, Sergei V

    2015-01-01

    A number of potentiometric biosensors based on coimmobilization of enzymes with different types of zeolite on pH-ion-sensitive field-effect transistor (ISFET) have been developed. Their working characteristics have been determined and compared. It was shown that clinoptilolite and zeolite Beta polymorph A (BEA) are more promising for creating biosensors than zeolite A. Changing the concentration of zeolite BEA in membranes, it is possible to extend the biosensor linear measurement range. The two-layer method of deposition of the enzyme with clinoptilolite was found to provide a significant increase in the biosensor sensitivity to substrates, whereas thermal modification of the zeolite BEA crystals can improve analytical characteristics of potentiometric biosensors for detection of toxic substances. These results show that it is possible to regulate the ISFET characteristics for different enzyme-based biosensors by tailoring the electrode surfaces via different zeolites. This makes zeolites strong candidates for integration into biosensors as ISFET modifiers.

  9. 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.

  10. Potentiometric Surface of the Aquia Aquifer in southern Maryland, September 1995

    USGS Publications Warehouse

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

    1997-01-01

    A map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in southern Maryland during September 1995 was prepared from water-level measurements in 80 wells. The potentiometric surface was above sea level near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties, 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 70 feet below sea level in a 60-square-mile area surrounding the deepest part of the cone of depression and 126 feet below sea level in one well near the center of the cone.

  11. 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.

  12. Potentiometric surface of the Aquia 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 Aquia aquifer in the Aquia aquifer in the Aquia Formation of Paleocene age in southern Maryland during September 1994 was prepared from water levels measured in 74 wells. The potentiometric surface was above sea level near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties, 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 70 feet below sea level in a 60-square-mile area surrounding the deepest part of the cone of depression and 131 feet below sea level in one well near the center of the cone.

  13. 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.

  14. Potentiometric Surface of the Upper Patapsco 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 Upper Patapsco aquifer in the Patapsco Formation of Lower Cretaceous age in Southern Maryland during September 2002. The map is based on water-level measurements in 50 wells. The highest measured water level was 117 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 southeast toward large well fields in Arnold and Annapolis, and from all directions toward a cone of depression located southwest of Waldorf. The measured ground-water level declined to 36 feet below sea level in Arnold, and to 23 feet below sea level in Annapolis. The lowest water level measured was 136 feet below sea level southwest of Waldorf.

  15. Potentiometric surface of the Aquia 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 Aquia aquifer in the Aquia Formation of Paleocene age in southern Maryland during September 1991 was prepared from water levels measured in 82 wells. The potentiometric surface was above sea level near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties, 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. Groundwater levels were more than 60 feet below sea level in a 60-sq-mi area surrounding the deepest part of the cone of depression and 117 feet below sea level in one well near the center of the cone.

  16. Determination of peroxyl radical scavenging activity of flavonoids and plant extracts using an automatic potentiometric titrator.

    PubMed

    Sano, Mitsuaki; Yoshida, Risa; Degawa, Masakuni; Miyase, Toshio; Yoshino, Kyoji

    2003-05-01

    A novel potentiometric method for evaluation of peroxyl radical scavenging activity of flavonoids and plant extracts was developed. The oxidation of potassium iodide (KI) was performed in acetonitrilephosphate buffer (1:1) containing antioxidant using 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator. The amount of iodine released from KI during a 20-min free radical oxidation was determined quantitatively using an automatic potentiometric titrator with sodium thiosulfate. The radical scavenging activity of the sample was expressed as the inhibition ratio for iodine release of the control group mediated by the radical. The results obtained from some authentic polyphenols correlated well with those of previous reports. This is a simple, time-saving method requiring less than 30 min and is useful in assessing the radical scavenging activity of antioxidants in plant extracts. We describe the radical scavenging activities of various flavonoids including 21 kinds of tea catechins and vegetable extracts by this method.

  17. 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)

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Potentiometric Measurement of Transition Ranges and Titration Errors for Acid/Base Indicators

    NASA Astrophysics Data System (ADS)

    Flowers, Paul A.

    1997-07-01

    Sophomore analytical chemistry courses typically devote a substantial amount of lecture time to acid/base equilibrium theory, and usually include at least one laboratory project employing potentiometric titrations. In an effort to provide students a laboratory experience that more directly supports their classroom discussions on this important topic, an experiment involving potentiometric measurement of transition ranges and titration errors for common acid/base indicators has been developed. The pH and visually-assessed color of a millimolar strong acid/base system are monitored as a function of added titrant volume, and the resultant data plotted to permit determination of the indicator's transition range and associated titration error. Student response is typically quite positive, and the measured quantities correlate reasonably well to literature values.

  4. Potentiometric Determination of CO2 Concentration in the Gaseous Phase: Applications in Different Laboratory Activities

    NASA Astrophysics Data System (ADS)

    Cortón, Eduardo; Kocmur, Santiago; Haim, Liliana; Galagovsky, Lydia

    2000-09-01

    Four simple experiments are described, in two laboratory sessions of 3 hours each. They provide high school students of a combined science course with the opportunity to review and integrate many topics while participating in a hands-on activity that resembles real industrial problems. The first lab comprises the calibration of a CO2 potentiometric detector with gas mixtures. The CO2 and CO2-free air required for the gaseous samples are produced in the lab by an inexpensive and simple apparatus. In the second lab, the CO2 potentiometric device is used to measure CO2uptake and release during different metabolic processes. The variation of CO2 production will be also estimated while changing the air/fuel proportion in a Bunsen burner.

  5. Potentiometric map of the Meridian-Upper Wilcox Aquifer in Mississippi, fall 1983

    USGS Publications Warehouse

    Darden, Daphne

    1986-01-01

    The Meridian-upper Wilcox aquifer consists of the Meridian Sand member of the Tallahatta Formation and the uppermost sand beds of the Wilcox Group. Thickness of the aquifer ranges from 50 ft to 500 ft. Precipitation recharges the Meridian-upper Wilcox in the outcrop area, which extends from Benton County, MS, in the north to Clarke County, MS, in the south. The potentiometric map is based on water level measurements made in about 170 wells in the Meridian-upper Wilcox aquifer in October 1983, and on the approximate altitudes of water surfaces in some major streams. The contours show altitudes at which water levels would have stood in tightly cased unpumped wells. This map, the second in the series for the Meridian-upper Wilcox aquifer, updates a map that delineated the potentiometric surface of the aquifer in 1979. (Lantz-PTT)

  6. 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.

  7. 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)

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

    SciTech Connect

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

    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 on 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.

  9. Use of a biomimetic chromatographic stationary phase for study of the interactions occurring between inorganic anions and phosphatidylcholine membranes.

    PubMed Central

    Hu, Wenzhi; Haddad, Paul R; Hasebe, Kiyoshi; Mori, Masanobu; Tanaka, Kazuhiko; Ohno, Masako; Kamo, Naoki

    2002-01-01

    A liquid chromatographic method for the study of ion-membrane interactions is reported. A phosphatidylcholine biomimetic stationary phase was established by loading dimyristoylphosphatidylcholine (DMPC) onto a reversed-phase octadecylsilica packed column. This column was then used to study the interaction of some inorganic anions with the stationary phase by UV and conductivity detection. Ten inorganic anions were selected as model ions and were analyzed with the proposed chromatographic system. Anion-DMPC interactions of differing magnitudes were observed for all of the model anions. Perchlorate-DMPC interactions were strongest, followed by thiocyanate-DMPC, iodide-DMPC, chlorate-DMPC, nitrate-DMPC, bromide-DMPC, chloride-DMPC, fluoride-DMPC, and then sulfate-DMPC. Cations in the eluent, especially H(+) ions and divalent cations such as Ca(2+), showed strong effects on anion-DMPC interactions. The chromatographic data suggest that DMPC interacts with both the anions and the cations. Anion-DMPC interactions were dependent on the surface potential of the stationary phase: at low surface potentials anion-DMPC interactions were predominantly solvation dependent in nature whereas at more positive surface potentials anion-DMPC interactions were predominantly electrostatic in nature. Cation-DMPC interactions served to raise the surface potential, causing the anion-DMPC interactions to vary from solvation dependent to electrostatic. The chromatographic data were used to provide quantitative estimates of the enthalpies of the anion-DMPC interactions. PMID:12496102

  10. Semi-automatic version of the potentiometric titration method for characterization of uranium compounds.

    PubMed

    Cristiano, Bárbara F G; Delgado, José Ubiratan; da Silva, José Wanderley S; de Barros, Pedro D; de Araújo, Radier M S; Dias, Fábio C; Lopes, Ricardo T

    2012-09-01

    The potentiometric titration method was used for characterization of uranium compounds to be applied in intercomparison programs. The method is applied with traceability assured using a potassium dichromate primary standard. A semi-automatic version was developed to reduce the analysis time and the operator variation. The standard uncertainty in determining the total concentration of uranium was around 0.01%, which is suitable for uranium characterization and compatible with those obtained by manual techniques. PMID:22406220

  11. 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.

  12. Simulated changes in potentiometric levels resulting from groundwater development for phosphate mines, west-central Florida

    USGS Publications Warehouse

    Wilson, W.E.; Gerhart, J.M.

    1979-01-01

    A digital model of two-dimensional groundwater flow was used to predict changes in the potentiometric surface of the Floridan aquifer resulting from groundwater development for proposed and existing phosphate mines during 1976-2000. The modeled area covers 15,379 km2 in west-central Florida. In 1975, groundwater withdrawn from the Floridan aquifer for irrigation, phosphate mines, other industries and municipal supplies averaged about 28,500 l/s. Withdrawals for phosphate mines are expected to shift from Polk County to adjacent counties to the south and west, and to decline from about 7,620 l/s in 1975 to about 7,060 l/s in 2000. The model was calibrated under steady-state and transient conditions. Input parameters included aquifer transmissivity and storage coefficient; thickness, vertical hydraulic conductivity, and storage coefficient of the upper confining bed; altitudes of the water table and potentiometric surface; and groundwater withdrawals. Simulation of November 1976 to October 2000, using projected combined pumping rates for existing and proposed phosphate mines, resulted in a rise in the potentiometric surface of about 6 m in Polk County, and a decline of about 4 m in parts of Manatee and Hardee counties. ?? 1979.

  13. Potentiometric Surface of the Lower Patapsco 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 Lower Patapsco aquifer in the Patapsco Formation of Cretaceous age in Southern Maryland during September 2001. The map is based on water-level measurements in 65 wells. The potentiometric surface was as high as 110 feet above sea level near the northwestern boundary and outcrop area of the aquifer in northern Anne Arundel County. From this area, the potentiometric surface declined towards large well fields at Severndale, Arnold, and Annapolis. The ground-water levels declined to 78 feet below sea level at Severndale, 38 feet below sea level at Arnold, and 31 feet below sea level a few miles west of Annapolis. There was also a cone of depression covering a large area in Charles County that includes Waldorf, LaPlata, Indian Head, and the Morgantown power plant. The ground-water levels were as low as 173 feet below sea level at Waldorf, 126 feet below sea level at LaPlata, 112 feet below sea level at Indian Head, and 92 feet below sea level at the Morgantown power plant.

  14. Potentiometric surface of the lower 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 lower Patapsco aquifer in the Patapsco Formation of Cretaceous age in southern Maryland during September 1994 was prepared from water levels measured in 56 wells. The potentiometric surface was at least 104 feet above sea level near the northwestern boundary and outcrop area of the aquifer in a topographically high area of Prince Georges County, and at least 89 feet above sea level in a similar setting in Anne Arundel County. From these high areas, the potentiometric surface declined to the south and southeast toward large well fields at Crofton, Severndle, Arnold, Annapolis, Waldorf, La Plata, Indian Head, and Morgantown. The ground-water levels reached 20 feet below sea level at Crofton, 80 feet below sea level at Severndale, 25 feet below sea level at Arnold, more than 10 feet below sea level near Annapolis, more than 130 feet below sea level in the Waldorf area, more than 100 feet below sea level at La Plata an Indian Head, an nearly 80 feet below sea level at the Morgantown powerplant.

  15. Potentiometric Surface of the Lower 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 lower Patapsco aquifer in the Patapsco Formation of Cretaceous age in southern Maryland during September 1995 was prepared from water-level measurements in 69 wells. The potentiometric surface was 87 feet above sea level near the northwestern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel County. From this high area, the potentiometric surface declined to the south and southeast toward large well fields at Crofton, Severndale, Arnold, Annapolis, Waldorf, LaPlata, Indian Head, and Morgantown. The ground-water levels reached 18 feet below sea level at Crofton, 62 feet below sea level at Severndale, 26 feet below sea level at Arnold, more than 20 feet below sea level near Annapolis, 160 feet below sea level in the Waldorf area, nearly 100 feet below sea level at LaPlata, more than 110 feet below sea level at Indian Head, and 75 feet below sea level at the Morgantown powerplant.

  16. 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.

  17. Potentiometric map of the Paleozoic aquifer in northeastern Mississippi, November and December 1982

    USGS Publications Warehouse

    Darden, Daphne

    1984-01-01

    This potentiometric map is the second map of the Gordo aquifer 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 marked by large ground-water cones of depression in the Tupelo and Columbus areas. Water levels in or near the outcrop of the Gordo aquifer show little long-term change. Heavy withdrawals in the downdip area have caused water-level declines of about 2 feet per year since 1978 in much of the confined part of the aquifer. The water-level decline in the Tupelo area has averaged about 5 feet per year since 1966; however, there has been water-level rise at the center of the cone of depression as a result of a change in the distribution of pumping. (USGS)

  18. 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

  19. Novel heterocyclic thiosemicarbazones derivatives as colorimetric and "turn on" fluorescent sensors for fluoride anion sensing employing hydrogen bonding.

    PubMed

    Ashok Kumar, S L; Saravana Kumar, M; Sreeja, P B; Sreekanth, A

    2013-09-01

    Two novel heterocyclic thiosemicarbazone derivatives have been synthesized, and characterized, by means of spectroscopic and single crystal X-ray diffraction methods. Their chromophoric-fluorogenic response towards anions in competing solvent dimethyl sulfoxide (DMSO) was studied. The receptor shows selective recognition towards fluoride anion. The binding affinity of the receptors with fluoride anion was calculated using UV-visible and fluorescence spectroscopic techniques. PMID:23714188

  20. Water-table and Potentiometric-surface altitudes in the Upper Glacial, Magothy, and Lloyd aquifers beneath Long Island, New York, April-May 2010

    USGS Publications Warehouse

    Monti, Jack; Como, Michael D.; Busciolano, Ronald

    2013-01-01

    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 accurate than those measured at observation wells, which are not pumped (Busciolano, 2002). In this report, all water-level altitudes are referenced to the National Geodetic Vertical Datum of 1929 (NGVD 29). Hydrographs are included on these maps for selected wells that are instrumented with recording equipment. These hydrographs are representative of the 2010 water year1 to show the changes that have occurred throughout that period. The synoptic survey water level measured at the well is included on each hydrograph.

  1. Ultraviolet-circular dichroism spectroscopy and potentiometric study of the interaction between human serum albumin and sodium perfluorooctanoate.

    PubMed

    Messina, Paula; Prieto, Gerardo; Dodero, Verónica; Ruso, Juan M; Schulz, Pablo; Sarmiento, Félix

    2005-12-15

    The interaction of a fluorinated surfactant, sodium perfluorooctanoate, with human serum albumin (HSA) has been investigated by a combination of ultraviolet-circular dichroism (UV-CD) spectroscopy and potentiometry (by a home-built ion-selective electrode) techniques to detect and characterize the conformational transitions of HSA. By using difference spectroscopy, the transition was followed as a function of temperature, and the data were analyzed to obtain the parameters characterizing the thermodynamics of unfolding. The results indicate that the presence of surfactant drastically changes the melting unfolding, acting as a structure stabilizer and delaying the unfolding process. Potentiometric measurements were used to determine the binding isotherms and binding capacity for this system. The isotherm shows a high affinity of surfactant molecules for HSA. The average number of surfactant molecules absorbed per protein molecule (at 28 mM of surfactant concentration) was found to be approximately 900, about 6 g of surfactant per gram of protein. The shape of the binding capacity curve and the relation between binding capacity and extend of cooperativity were examined. From these analysis, the values of g (number of ligand-binding sites), KH (Hill binding constant), and nH (Hill coefficient) were determined.

  2. Organically nanoporous silica gel based on carbon paste electrode for potentiometric detection of trace Cr(III).

    PubMed

    Zhou, Wei; Chai, Yaqin; Yuan, Ruo; Guo, Junxiang; Wu, Xia

    2009-08-11

    A new ion-selective electrode (ISE) for the detection of trace chromium(III) was designed by using 2-acetylpyridine and nanoporous silica gel (APNSG)-functionalized carbon paste electrode (CPE). The presence of APNSG acted as not only a paste binder, but also a reactive material. With 7.5 wt% APNSG proportions, the developed electrode exhibited wide dynamic range of 1.0 x 10(-8) to 1.0 x 10(-3) M toward Cr(III) with a detection limit of 8.0 x 10(-9) M and a Nernstian slope of 19.8 +/- 0.2 mV decade(-1). The as-prepared electrode displayed rapid response (approximately 55 s), long-time stability, and high sensitivity. Moreover, the potentiometric responses could be carried out with wide pH range of 1.5-5.0. In addition, the content of Cr(III) in food samples, e.g. coffee and tea leaves, has been assayed by the developed electrode, atomic absorption spectrophotometer (AAS) and atomic emission spectrometer (ICP-AES), respectively, and consistent results were obtained. Importantly, the response mechanism of the proposed electrode was investigated by using AC impedance and UV-vis spectroscopy.

  3. Detection of circulating tumor cells in prostate cancer based on carboxylated graphene oxide modified light addressable potentiometric sensor.

    PubMed

    Gu, Yajun; Ju, Cheng; Li, Yanjun; Shang, Zhiqun; Wu, Yudong; Jia, Yunfang; Niu, Yuanjie

    2015-04-15

    Circulating tumor cells (CTCs) are a group of rare cancer cells that have detached from a primary tumor and circulate in the bloodstream. Herein, light addressable potentiometric sensor (LAPS) was exploited in the label-free detection of CTCs in the prostate cancer. To this end, the mouse anti-human epithelial cell adhesion molecule (anti-EpCAM) monoclonal antibody was selected as the probe to capture CTCs according to our western blot experiments, and therefore the anti-EpCAM was immobilized on the surface of carboxylated graphene oxide (GO-COOH) modified LAPS. Spiking experiments confirmed that LAPS' voltage decreased with the increasing of CTCs' concentration both in phosphate buffer (PBS) and blood, and as few as 10 CTCs in 1ml of blood could be detected, illustrating the high sensitivity of the proposed strategy. The analysis of healthy blood samples revealed no change in electrical signal, confirming the specificity of the system. Ultraviolet-visible (UV-vis) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and immunofluorescent assay (IFA) were conducted to characterize GO-COOH, testify its existence on LAPS and validate CTCs' capturing by anti-EpCAM grafted on GO-COOH modified substrates. It is indicated that LAPS could be a potential platform for CTCs detection and may provide a powerful tool for downstream analysis.

  4. Use of Sequential Injection Analysis to construct a Potentiometric Electronic Tongue: Application to the Multidetermination of Heavy Metals

    NASA Astrophysics Data System (ADS)

    Mimendia, Aitor; Legin, Andrey; Merkoçi, Arben; del Valle, Manel

    2009-05-01

    An automated potentiometric electronic tongue (ET) was developed for the quantitative determination of heavy metal mixtures. The Sequential Injection Analysis (SIA) technique was used in order to automate the obtaining of input data, and the combined response was modeled by means of Artificial Neural Networks (ANN). The sensor array was formed by four sensors: two based on chalcogenide glasses Cd sensor and Cu sensor, and the rest on poly(vinyl chloride) membranes Pb sensor and Zn sensor. The Ion Selective Electrode (ISE) sensors were first characterized with respect to one and two analytes, by means of high-dimensionality calibrations, thanks to the use of the automated flow system; this characterization enabled an interference study of great practical utility. To take profit of the dynamic nature of the sensor's response, the kinetic profile of each sensor was compacted by Fast Fourier Transform (FFT) and the extracted coefficients were used as inputs for the ANN in the multidetermination applications. In order to identify the ANN which provided the best model of the electrode responses, some of the network parameters were optimized. Finally analyses were performed employing synthetic samples and water samples of the river Ebro; obtained results were compared with reference methods.

  5. Use of Sequential Injection Analysis to construct a Potentiometric Electronic Tongue: Application to the Multidetermination of Heavy Metals

    SciTech Connect

    Mimendia, Aitor; Merkoci, Arben; Valle, Manel del; Legin, Andrey

    2009-05-23

    An automated potentiometric electronic tongue (ET) was developed for the quantitative determination of heavy metal mixtures. The Sequential Injection Analysis (SIA) technique was used in order to automate the obtaining of input data, and the combined response was modeled by means of Artificial Neural Networks (ANN). The sensor array was formed by four sensors: two based on chalcogenide glasses Cd sensor and Cu sensor, and the rest on poly(vinyl chloride) membranes Pb sensor and Zn sensor. The Ion Selective Electrode (ISE) sensors were first characterized with respect to one and two analytes, by means of high-dimensionality calibrations, thanks to the use of the automated flow system; this characterization enabled an interference study of great practical utility. To take profit of the dynamic nature of the sensor's response, the kinetic profile of each sensor was compacted by Fast Fourier Transform (FFT) and the extracted coefficients were used as inputs for the ANN in the multidetermination applications. In order to identify the ANN which provided the best model of the electrode responses, some of the network parameters were optimized. Finally analyses were performed employing synthetic samples and water samples of the river Ebro; obtained results were compared with reference methods.

  6. Electroactive Materials for Anion Separation-Technetium from Nitrate

    SciTech Connect

    Hubler, Timothy L.; McBreen, James; Smyrl, William H.; Lilga, Mike A.; Rassat, Scot D.

    2004-06-29

    The aim of the proposed research is to use electroactive ion exchange materials to remove anionic contaminants from HLW wastes and process streams. An ion exchange process using electroactive materials sorbs contaminants selectively and then expels (elutes) them electrochemically by changing the charge balance through redox reactions in the sorbent as opposed to requiring the addition of a chemical eluent. Such processes can theoretically remove anions (e.g., pertechnetate, chromate, and perchorate) and concentrate them in a separate product stream while adding no process chemicals. A practical implementation in HLW process facilities would be a breakthrough in the ability of DOE to economically minimize waste and prevent pollution throughout the complex. To enable this, our work focuses on manipulating specific properties of redox polymers to control the hydrophobicity and ion-pair properties pertinent to the reversibility, selectivity, stability, intercalation/de-intercalation rates, and capacity of the polymers.

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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 (SWFWMD) and is used for major public supply, domestic use, irrigation, and brackish-water desalination in coastal communties (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 a tightly cased well that taps 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 the most recent 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 show the approximate annual low and high water

  12. 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

  13. Potentiometric and NMR complexation studies of phenylboronic acid PBA and its aminophosphonate analog with selected catecholamines

    NASA Astrophysics Data System (ADS)

    Ptak, Tomasz; Młynarz, Piotr; Dobosz, Agnieszka; Rydzewska, Agata; Prokopowicz, Monika

    2013-05-01

    Boronic acids are a class of intensively explored compounds, which according to their specific properties have been intensively explored in last decades. Among them phenylboronic acids and their derivatives are most frequently examined as receptors for diverse carbohydrates. In turn, there is a large gap in basic research concerning complexation of catecholamines by these compounds. Therefore, we decided to undertake studies on interaction of chosen catecholamines, namely: noradrenaline (norephinephrine), dopamine, L-DOPA, DOPA-P (phosphonic analog of L-DOPA) and catechol, with simple phenyl boronic acid PBA by means of potentiometry and NMR spectroscopy. For comparison, the binding properties of recently synthesized phenylboronic receptor 1 bearing aminophosphonate function in meta-position were investigated and showed promising ability to bind catecholamines. The protonation and stability constants of PBA and receptor 1 complexes were examined by potentiometry. The obtained results demonstrated that PBA binds the catecholamines with the following affinity order: noradrenaline ⩾ dopamine ≈ L-DOPA > catechol > DOPA-P, while its modified analog 1 reveals slightly different preferences: dopamine > noradrenaline > catechol > L-DOPA > DOPA-P.

  14. High-capacity anion exchangers based on poly (glycidylmethacrylate-divinylbenzene) microspheres for ion chromatography.

    PubMed

    Liu, Junwei; Wang, Yong; Cheng, Heli; Wang, Nani; Wu, Shuchao; Zhang, Peimin; Zhu, Yan

    2016-10-01

    Poly (glycidylmethacrylate-divinylbenzene) microspheres were prepared by the two-staged swelling and polymerization method and applied to prepare anion exchange stationary phases. Methylamine, dimethylamine, trimethylamine, diethylamine and triethylamine were selected to prepare the quaternary ammonium groups of anion exchangers, respectively. The diameters and surface characteristics of microspheres were measured by scanning electron microscope and nitrogen adsorption-desorption measurements. The anion exchangers were characterized by Fourier transform infrared spectrum, elemental analysis and breakthrough curve methods. The chromatographic performances of anion exchangers were illustrated by separating conventional anions, organic weak acids and carbohydrates. The results indicated that the anion exchange capacities were controllable by changing either the content of glycidylmethacrylate in microspheres or the number of bonded quaternary ammonium layer. Meanwhile, the substituents of quaternary ammonium groups greatly influenced the separation properties of anion exchangers. Finally, the three-layer methylamine-quaternized anion exchanger was successfully applied for the determination of fluoride in tea sample. The content of fluoride was detected to be 0.13mgg(-1) without the interference of acetate and formate. PMID:27474308

  15. Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, May 1995

    USGS Publications Warehouse

    Knowles, Leel; O'Reilly, A. M.; Phelps, G.G.; Bradner, L.A.

    1995-01-01

    This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1995. The map is based on water-level measurements made at more than 900 wells and springs. Approximately 30 new wells were added to better define the potentiometric surface mainly in the northwest area of the map. Data on the map were contoured using 5-foot contour intervals in most areas. Two new wells located north of Rainbow Springs indicate a slight northward extension of the depressed area surrounding the springs. Several new wells in Bradford County indicate a slight reduction in the size of the potentiometric-surface high along the northwest edge of the county. The potentiometric surface of this karstic aquifer generally reflects land surface topography. Potentiometric-surface highs often correspond to topographic highs, which are areas of 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 127 feet above sea level in Polk County to 84 feet below sea level in southeast Georgia near the St. Marys River. Water levels measured in May 1995 generally were about 0 to 4 feet higher than those measured in May 1994 except in St. Lucie County and near Rainbow Springs, where levels were 1 to 3 feet lower. Generally, May 1995 water levels were 0 to 5 feet lower than levels in September 1994, except near Orlando, where levels were 6 to 12 feet lower, and across the northwest corner of the map area which includes Marion, Alachua, Bradford, Baker, and Nassau Counties, north and west Duval County, and south Georgia. (USGS)

  16. 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

  17. Sheathless capillary electrophoresis‐mass spectrometry for anionic metabolic profiling

    PubMed Central

    Gulersonmez, Mehmet Can; Lock, Stephen; Hankemeier, Thomas

    2015-01-01

    The performance of CE coupled on‐line to MS via a sheathless porous tip sprayer was evaluated for anionic metabolic profiling. A representative metabolite mixture and biological samples were used for the evaluation of various analytical parameters, such as peak efficiency (plate numbers), migration time and peak area repeatability, and LODs. The BGE, i.e. 10% acetic acid (pH 2.2), previously used for cationic metabolic profiling was now assessed for anionic metabolic profiling by using MS detection in negative ion mode. For test compounds, RSDs for migration times and peak areas were below 2 and 11%, respectively, and plate numbers ranged from 60 000 to 40 0000 demonstrating a high separation efficiency. Critical metabolites with low or no retention on reversed‐phase LC could be efficiently separated and selectively analyzed by the sheathless CE‐MS method. An injection volume of only circa 20 nL resulted in LODs between 10 and 200 nM (corresponding to an amount of 0.4–4 fmol), which was an at least tenfold improvement as compared to LODs obtained by conventional CE‐MS approaches for these analytes. The methodology was applied to anionic metabolic profiling of glioblastoma cell line extracts. Overall, a sheathless CE‐MS method has been developed for highly efficient and sensitive anionic metabolic profiling studies, which can also be used for cationic metabolic profiling studies by only switching the MS detection and separation voltage polarity. PMID:26593113

  18. Sheathless capillary electrophoresis-mass spectrometry for anionic metabolic profiling.

    PubMed

    Gulersonmez, Mehmet Can; Lock, Stephen; Hankemeier, Thomas; Ramautar, Rawi

    2016-04-01

    The performance of CE coupled on-line to MS via a sheathless porous tip sprayer was evaluated for anionic metabolic profiling. A representative metabolite mixture and biological samples were used for the evaluation of various analytical parameters, such as peak efficiency (plate numbers), migration time and peak area repeatability, and LODs. The BGE, i.e. 10% acetic acid (pH 2.2), previously used for cationic metabolic profiling was now assessed for anionic metabolic profiling by using MS detection in negative ion mode. For test compounds, RSDs for migration times and peak areas were below 2 and 11%, respectively, and plate numbers ranged from 60 000 to 40 0000 demonstrating a high separation efficiency. Critical metabolites with low or no retention on reversed-phase LC could be efficiently separated and selectively analyzed by the sheathless CE-MS method. An injection volume of only circa 20 nL resulted in LODs between 10 and 200 nM (corresponding to an amount of 0.4-4 fmol), which was an at least tenfold improvement as compared to LODs obtained by conventional CE-MS approaches for these analytes. The methodology was applied to anionic metabolic profiling of glioblastoma cell line extracts. Overall, a sheathless CE-MS method has been developed for highly efficient and sensitive anionic metabolic profiling studies, which can also be used for cationic metabolic profiling studies by only switching the MS detection and separation voltage polarity.

  19. Capillary zone electrophoresis of inorganic anions with conductivity detection.

    PubMed

    Kaniansky, D; Zelenská, V; Baluchová, D

    1996-12-01

    A carrier electrolyte system for capillary zone electrophoresis (CZE) resolving chloride, bromide, iodide, fluoride, nitrite, nitrate, sulfate, and phosphate in a hydrodynamically closed separation compartment is described. The carrier electrolyte combines the effects of pH, polyvinylpyrrolidone (PVP) and the counterionic constituent on the effective mobilities of the anions. In 300 microns ID capillary tubes made of fluorinated ethylene-propylene copolymer (FEP), and with detection of analytes with the aid of an alternating current conductivity detector, detection limits in the range of 3-10 ppb could be achieved for 200 nL sample volumes. The separation efficiencies were in the range of 1.5-2.5 x 10(5) theoretical plates per meter for an adequate sample load. The reproducibility was evaluated for two concentration levels. For concentrations close to the limits of quantitation (50-120 ppb), the RSD values ranged from 1.5-12.6%, with the highest scatter for fluoride and phosphate. The RSD values were in the range of 0.4-1.5% for 300-1200 ppb concentrations of the anions. Typical analysis times were 2-5 min, depending on the anion species. A series of water samples (drinking, river, rain) was used to assess the practical applicability of the CZE method. The method is a suitable alternative for the determination of both anionic macro- and microconstituents in water with a good overall selectivity.

  20. Adsorption affinity of anions on metal oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Pechenyuk, S. I.; Semushina, Yu. P.; Kuz'mich, L. F.

    2013-03-01

    The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO{4/3-}, CO{3/2-} > C2O{4/2-}, C(OH)(CH2)2(COO){3/3-}, (CHOH)2(COO){2/2-} > CrO{4/2-} ≫ SO{4/2-}.

  1. ANION EXCHANGE METHOD FOR SEPARATION OF METAL VALUES

    DOEpatents

    Hyde, E.K.; Raby, B.A.

    1959-02-10

    A method is described for selectively separating radium, bismuth, poloniums and lead values from a metallic mixture of thc same. The mixture is dissolved in aqueous hydrochloric acid and the acidity is adjusted to between 1 to 2M in hydrochloric acid to form the anionic polychloro complexes of polonium and bismuth. The solution is contacted with a first anion exchange resin such as strong base quaternary ammonia type to selectively absorb the polonium and bismuth leaving the radium and lead in the effluent. The effluent, after treatment in hydrochloric acid to increase the hydrochloric acid concentration to 6M is contacted with a second anion exchange iesin of the same type as the above to selectively adsorb the lead leaving the radium in the effluent. Radium is separately recovered from the effluent from the second exchange column. Lead is stripped from the loaded resin of the second column by treatment with 3M hydrochloric acid solution. The loaded resin of the first column is washed with 8M hydrochloric acid solution to recover bismuth and then treated with strong nitric acid solution to recover polonium.

  2. The dissociation constants of the cytostatic bosutinib by nonlinear least-squares regression of multiwavelength spectrophotometric and potentiometric pH-titration data.

    PubMed

    Meloun, Milan; Nečasová, Veronika; Javůrek, Milan; Pekárek, Tomáš

    2016-02-20

    Potentiometric and spectrophotometric pH-titration of the multiprotic cytostatics bosutinib for dissociation constants determination were compared. Bosutinib treats patients with positive chronic myeloid leukemia. Bosutinib exhibits four protonatable sites in a pH range from 2 to 11, where two pK are well separated (ΔpK>3), while the other two are near dissociation constants. In the neutral medium, bosutinib occurs in the slightly water soluble form LH that can be protonated to the soluble cation LH4(3+). The molecule LH can be dissociated to still difficultly soluble anion L(-). The set of spectra upon pH from 2 to 11 in the 239.3-375.0nm was divided into two absorption bands: the first one from 239.3 to 290.5nm and the second from 312.3 to 375.0nm, which differ in sensitivity of chromophores to a pH change. Estimates of pK of the entire set of spectra were compared with those of both absorption bands. Due to limited solubility of bosutinib the protonation in a mixed aqueous-methanolic medium was studied. In low methanol content of 3-6% three dissociation constants can be reliably determined with SPECFIT/32 and SQUAD(84) and after extrapolation to zero content of methanol they lead to pKc1=3.43(12), pKc2=4.54(10), pKc3=7.56(07) and pKc4=11.04(05) at 25°C and pKc1=3.44(06), pKc2=5.03(08) pKc3=7.33(05) and pKc4=10.92(06) at 37°C. With an increasing content of methanol in solvent the dissociation of bosutinib is suppressed and the percentage of LH3(2+) decreases and LH prevails. From the potentiometric pH-titration at 25°C the concentration dissociation constants were estimated with ESAB pKc1=3.51(02), pKc2=4.37(02), pKc3=7.97(02) and pKc4=11.05(03) and with HYPERQUAD: pKc1=3.29(12), pKc2=4.24(10), pKc3=7.95(07) and pKc4=11.29(05).

  3. The dissociation constants of the cytostatic bosutinib by nonlinear least-squares regression of multiwavelength spectrophotometric and potentiometric pH-titration data.

    PubMed

    Meloun, Milan; Nečasová, Veronika; Javůrek, Milan; Pekárek, Tomáš

    2016-02-20

    Potentiometric and spectrophotometric pH-titration of the multiprotic cytostatics bosutinib for dissociation constants determination were compared. Bosutinib treats patients with positive chronic myeloid leukemia. Bosutinib exhibits four protonatable sites in a pH range from 2 to 11, where two pK are well separated (ΔpK>3), while the other two are near dissociation constants. In the neutral medium, bosutinib occurs in the slightly water soluble form LH that can be protonated to the soluble cation LH4(3+). The molecule LH can be dissociated to still difficultly soluble anion L(-). The set of spectra upon pH from 2 to 11 in the 239.3-375.0nm was divided into two absorption bands: the first one from 239.3 to 290.5nm and the second from 312.3 to 375.0nm, which differ in sensitivity of chromophores to a pH change. Estimates of pK of the entire set of spectra were compared with those of both absorption bands. Due to limited solubility of bosutinib the protonation in a mixed aqueous-methanolic medium was studied. In low methanol content of 3-6% three dissociation constants can be reliably determined with SPECFIT/32 and SQUAD(84) and after extrapolation to zero content of methanol they lead to pKc1=3.43(12), pKc2=4.54(10), pKc3=7.56(07) and pKc4=11.04(05) at 25°C and pKc1=3.44(06), pKc2=5.03(08) pKc3=7.33(05) and pKc4=10.92(06) at 37°C. With an increasing content of methanol in solvent the dissociation of bosutinib is suppressed and the percentage of LH3(2+) decreases and LH prevails. From the potentiometric pH-titration at 25°C the concentration dissociation constants were estimated with ESAB pKc1=3.51(02), pKc2=4.37(02), pKc3=7.97(02) and pKc4=11.05(03) and with HYPERQUAD: pKc1=3.29(12), pKc2=4.24(10), pKc3=7.95(07) and pKc4=11.29(05). PMID:26730513

  4. Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection.

    PubMed

    Afshar, Majid Ghahraman; Crespo, Gastón A; Bakker, Eric

    2015-07-01

    We report a general concept based on a selective electrochemical ion pump used for creating concentration perturbations in thin layer samples (∼40 μL). As a first example, hydrogen ions are released from a selective polymeric membrane (proton pump) and the resulting pH is assessed potentiometrically with a second membrane placed directly opposite. By applying a constant potential modulation for 30 s, an induced proton concentration of up to 350 mM may be realized. This concept may become an attractive tool for in situ titrations without the need for sampling, because the thin layer eventually re-equilibrates with the contacting bulk sample. Acid-base titrations of NaOH and Na2 CO3 are demonstrated. The determination of total alkalinity in a river water sample is carried out, giving levels (23.1 mM) comparable to that obtained by standard methods (23.6 mM). The concept may be easily extended to other ions (cations, anions, polyions) and may become attractive for environmental and clinical applications.

  5. Thin-Layer Chemical Modulations by a Combined Selective Proton Pump and pH Probe for Direct Alkalinity Detection.

    PubMed

    Afshar, Majid Ghahraman; Crespo, Gastón A; Bakker, Eric

    2015-07-01

    We report a general concept based on a selective electrochemical ion pump used for creating concentration perturbations in thin layer samples (∼40 μL). As a first example, hydrogen ions are released from a selective polymeric membrane (proton pump) and the resulting pH is assessed potentiometrically with a second membrane placed directly opposite. By applying a constant potential modulation for 30 s, an induced proton concentration of up to 350 mM may be realized. This concept may become an attractive tool for in situ titrations without the need for sampling, because the thin layer eventually re-equilibrates with the contacting bulk sample. Acid-base titrations of NaOH and Na2 CO3 are demonstrated. The determination of total alkalinity in a river water sample is carried out, giving levels (23.1 mM) comparable to that obtained by standard methods (23.6 mM). The concept may be easily extended to other ions (cations, anions, polyions) and may become attractive for environmental and clinical applications. PMID:26014101

  6. 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.

  7. Anion Recognition and Induced Self-Assembly of an α,γ-Cyclic Peptide To Form Spherical Clusters.

    PubMed

    Rodríguez-Vázquez, Nuria; Amorín, Manuel; Alfonso, Ignacio; Granja, Juan R

    2016-03-24

    A cyclic octapeptide composed of hydroxy-functionalized γ-amino acids folds in a "V-shaped" conformation that allows the selective recognition of anions such as chloride, nitrate, and carbonate. The process involves the simultaneous self-assembly of six peptide subunits and the recognition of four anions to form a tetrahedral structure, in which the anions are located at the corners of the resulting structure. Each anion is coordinated to three different peptides. The structure was fully characterized by several techniques, including NMR spectroscopy and X-ray diffraction, and the material was able to facilitate the transmembrane transport of chloride ions. PMID:26945782

  8. Aquaporins with anion/monocarboxylate permeability: mechanisms, relevance for pathogen–host interactions

    PubMed Central

    Rambow, Janis; Wu, Binghua; Rönfeldt, Deike; Beitz, Eric

    2014-01-01

    Classically, aquaporins are divided based on pore selectivity into water specific, orthodox aquaporins and solute-facilitating aquaglyceroporins, which conduct, e.g., glycerol and urea. However, more aquaporin-passing substrates have been identified over the years, such as the gasses ammonia and carbon dioxide or the water-related hydrogen peroxide. It became apparent that not all aquaporins clearly fit into one of only two subfamilies. Furthermore, certain aquaporins from both major subfamilies have been reported to conduct inorganic anions, such as chloride, or monoacids/monocarboxylates, such as lactic acid/lactate. Here, we summarize the findings on aquaporin anion transport, analyze the pore layout of such aquaporins in comparison to prototypical non-selective anion channels, monocarboxylate transporters, and formate–nitrite transporters. Finally, we discuss in which scenarios anion conducting aquaporins may be of physiological relevance. PMID:25225485

  9. Cd(II)-coordination framework: synthesis, anion-induced structural transformation, anion-responsive luminescence, and anion separation.

    PubMed

    Hou, Shan; Liu, Qi-Kui; Ma, Jian-Ping; Dong, Yu-Bin

    2013-03-18

    A series of Cd(II) coordination frameworks that are constructed from a new oxadiazole-bridged ligand 3,5-bis(3-pyridyl-3-(3'-methylphenyl)-1,3,4-oxadiazole (L) and CdX2 (X = NO3(-), Cl(-), Br(-), I(-), N3(-), and SCN(-)) were synthesized. The NO3(-) anion of the solid CdL2(NO3)2·2THF (1) is able to be quantitatively exchanged with Cl(-), Br(-), I(-), SCN(-), and N3(-) in the solid state. For Cl(-) and Br(-), the anion exchange resulted in a anion-induced structural transformation to form the structures of 2 and 3, respectively. In addition, the Cd(II) structure herein exhibits the anion-responsive photoluminescence, which could be a useful method to monitor the anion-exchange process. Notably, compound 1 can recognize and completely separate SCN(-)/N3(-) with similar geometry.

  10. A titanium nitride nanotube array for potentiometric sensing of pH.

    PubMed

    Liu, Mengyang; Ma, Yanling; Su, Lei; Chou, Kuo-Chih; Hou, Xinmei

    2016-03-01

    A titanium nitride nanotube array (TiN NTA) electrode was fabricated through anodic oxidation of titanium and reduction and nitridation of TiO2 NTA. The microstructure of TiN NTA was characterized to be uniform with inner diameters of about 120 nm, a wall thickness of 15-20 nm and an average length of 10 μm. Open-circuit potentials were measured to evaluate the TiN TNA electrode related to pH sensitivity, response time, stability, selectivity, hysteresis and reproducibility in the pH range of 2.0-11.0 at 20 ± 1 °C. The prepared TiN NTA electrode exhibits a near-Nernstian slope of 55.33 mV per pH with the correlation coefficient value of 0.995. It shows good selectivity for H(+) ions in the presence of cations and anions, especially in fluoride-containing media. It also has good stability and reproducibility with a response time of 4.4 s. These make it a promising candidate as a pH electrode sensor. PMID:26818696

  11. Off-On-Off fluorescence behavior of an intramolecular charge transfer probe toward anions and CO2.

    PubMed

    Ali, Rashid; Razi, Syed S; Shahid, Mohammad; Srivastava, Priyanka; Misra, Arvind

    2016-11-01

    The photophysical behavior of a newly developed fluorescent probe, tricyanoethylphenyl phenanthroimidazole (TCPPI) has been studied. Upon interaction of different class of anions TCPPI displayed naked-eye sensitive fluorescence "turn-on" response to detect selectively F(-) (0.98μM, 18.62ppb) and CN(-) (1.12μM, 29.12ppb) anions in acetonitrile (MeCN). Job's plot analysis revealed a 1:1 binding stoichiometry between probe and anions. The spectral data analysis and 1H NMR titration studies suggested about the affinity of F(-) and CN(-) anions with moderately acidic -NH fragment of imidazolyl unit of probe through deprotonation and H-bonding interaction. Moreover, the anion activated probe upon interaction with CO2 revived photophysical properties of probe, "On-Off-On" type fluorescence and enabled anion-induced CO2 sensing in the medium. PMID:27267280

  12. Off-On-Off fluorescence behavior of an intramolecular charge transfer probe toward anions and CO2

    NASA Astrophysics Data System (ADS)

    Ali, Rashid; Razi, Syed S.; Shahid, Mohammad; Srivastava, Priyanka; Misra, Arvind

    2016-11-01

    The photophysical behavior of a newly developed fluorescent probe, tricyanoethylphenyl phenanthroimidazole (TCPPI) has been studied. Upon interaction of different class of anions TCPPI displayed naked-eye sensitive fluorescence "turn-on" response to detect selectively F- (0.98 μM, 18.62 ppb) and CN- (1.12 μM, 29.12 ppb) anions in acetonitrile (MeCN). Job's plot analysis revealed a 1:1 binding stoichiometry between probe and anions. The spectral data analysis and 1H NMR titration studies suggested about the affinity of F- and CN- anions with moderately acidic - NH fragment of imidazolyl unit of probe through deprotonation and H-bonding interaction. Moreover, the anion activated probe upon interaction with CO2 revived photophysical properties of probe, "On-Off-On" type fluorescence and enabled anion-induced CO2 sensing in the medium.

  13. Synthesis and evaluation of simple naked-eye colorimetric chemosensors for anions based on azo dye-thiosemicarbazones

    NASA Astrophysics Data System (ADS)

    Radchatawedchakoon, Widchaya; Sangsuwan, Withsakorn; Kruanetr, Senee; Sakee, Uthai

    2014-03-01

    A series of novel, highly selective azo dye-thiosemicarbazones based anion sensors (3e-f) have been synthesized from the condensation reaction between thiosemicarbazide and six different azo salicylaldehydes. The structure of the sensors was confirmed by spectroscopic methods. The selectivity and sensitivity in the recognition for acetate anion over other anions such as fluoride, chloride, iodide and dihydrogenphosphate anions were determined by naked-eyes and UV-vis spectra. The color of the solution containing sensor had an obvious change from light yellow to orange only after the addition of acetate anion in aqueous solution (water/dimethylsulfoxide, 7:3, v/v) while other anions did not cause obvious color change. The anion recognition property of the receptor via proton-transfer is monitored by UV-vis titration and 1H NMR spectroscopy. Under condition in aqueous solution of sensor 3e (water/dimethylsulfoxide, 7:3, v/v), linearity range for the quantification of acetate anion was 1-22 μM and limit of detection (LOD) of acetate anion was 0.71 μM.

  14. Estimated 2008 groundwater potentiometric surface and predevelopment to 2008 water-level change in the Santa Fe Group aquifer system in the Albuquerque area, central New Mexico

    USGS Publications Warehouse

    Falk, Sarah E.; Bexfield, Laura M.; Anderholm, Scott K.

    2011-01-01

    The water-supply requirements of the Albuquerque metropolitan area of central New Mexico have historically been met almost exclusively by groundwater withdrawal from the Santa Fe Group aquifer system. Previous studies have indicated that the large quantity of groundwater withdrawal relative to recharge has resulted in water-level declines in the aquifer system throughout the metropolitan area. Analysis of the magnitude and pattern of water-level change can help improve 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. This report, prepared by the U.S. Geological Survey in cooperation with the Albuquerque Bernalillo County Water Utility Authority, presents the estimated groundwater potentiometric surface during winter (from December to March) of the 2008 water year and the estimated changes in water levels between predevelopment and water year 2008 for the production zone of the Santa Fe Group aquifer system in the Albuquerque and surrounding metropolitan and military areas. Hydrographs from selected wells are included to provide details of historical water-level changes. In general, water-level measurements used for this report were measured in small-diameter observation wells screened over short intervals and were considered to best represent the potentiometric head in the production zone-the interval of the aquifer, about 300 feet below land surface to 1,100 feet or more below land surface, in which production wells generally are screened. Water-level measurements were collected by various local and Federal agencies. The 2008 water year potentiometric surface map was created in a geographic information system, and the change in water-level elevation from predevelopment to water year 2008 was calculated. The 2008 water-level contours indicate that the general direction of

  15. New reagent for extraction photomeric determination of anionic surface-active substances

    SciTech Connect

    Chernova, R.K.; Yastrebova, N.I.; Pankratov, A.N.

    1995-02-01

    The new reagent 2,6-diphenyl-4-(4-dimethylamino)styrylpyryl chloride is suggested for extraction photometric determination of anionic surface-active substances (SAS). This reagent possesses high sensitivity and selectivity, and can be used for the determination of both individual SAS of any kind and the total amount of anionic SAS. The reagent was used in analysis of highly mineralized statal waters and for the determination of sulfated products in polyoxyethylated alkylphenols.

  16. Hydration of chloride anions in the NanC Porin from Escherichia coli: A comparative study by QM/MM and MD simulations

    NASA Astrophysics Data System (ADS)

    Calandrini, V.; Dreyer, J.; Ippoliti, E.; Carloni, P.

    2014-12-01

    Chloride anions permeate the bacterial NanC porin in physiological processes. Here we present a DFT-based QM/MM study of this porin in the presence of these anions. Comparison is made with classical MD simulations on the same system. In both QM/MM and classical approaches, the anions are almost entirely solvated by water molecules. However, the average water-Cl- distance is significantly larger in the first approach. Polarization effects of protein groups close to Cl- anion are sizeable. These effects might modulate the anion-protein electrostatic interactions, which in turn play a central role for selectivity mechanisms of the channel.

  17. Hydration of chloride anions in the NanC Porin from Escherichia coli: a comparative study by QM/MM and MD simulations.

    PubMed

    Calandrini, V; Dreyer, J; Ippoliti, E; Carloni, P

    2014-12-14

    Chloride anions permeate the bacterial NanC porin in physiological processes. Here we present a DFT-based QM/MM study of this porin in the presence of these anions. Comparison is made with classical MD simulations on the same system. In both QM/MM and classical approaches, the anions are almost entirely solvated by water molecules. However, the average water-Cl(-) distance is significantly larger in the first approach. Polarization effects of protein groups close to Cl(-) anion are sizeable. These effects might modulate the anion-protein electrostatic interactions, which in turn play a central role for selectivity mechanisms of the channel.

  18. Gels based on anion recognition between triurea receptor and phosphate anion.

    PubMed

    Yang, Cuiling; Wu, Biao; Chen, Yongming; Zhang, Ke

    2015-04-01

    Anion recognition between the triurea receptor and phosphate anion is demonstrated as the cross-linkage to build supramolecular polymer gels for the first time. A novel multi-block copolymer (3) is designed to have functional triurea groups as cross-linking units along the polymer main chain. By virtue of anion coordination between the triurea receptor and phosphate anion with a binding mode of 2:1, supramolecular polymer gels are then prepared based on anion recognition using 3 as the building block. PMID:25694389

  19. Picosecond dynamics of benzophenone anion solvation

    SciTech Connect

    Lin, Y.; Jonah, C.D. )

    1993-01-14

    The dynamics of benzophenone anion solvation in alcohols are studied by pulse-radiolysis techniques. The solvation process is characterized by the blue shift of the transient absorption spectrum of the anion and is faster for the smaller alcohols. The anion is solvated more slowly than the electron in the same solvent, but the solvation times of both are similar to [tau][sub 2], the solvent dielectric relaxation time. The familiar phenomenological two-state model of solvation was found to be inappropriate for describing the anion solvation process. A multistate process appears to be a more appropriate description. The authors modeled the kinetics of the spectral relaxation. In most cases, nearly quantitative agreement between the calculated and observed spectra is achieved. The characteristic relaxation times for the alcohol solvents around the anions were also reproduced. 50 refs., 8 figs., 3 tabs.

  20. Creating molecular macrocycles for anion recognition

    PubMed Central

    2016-01-01

    Summary The creation and functionality of new classes of macrocycles that are shape persistent and can bind anions is described. The genesis of triazolophane macrocycles emerges out of activity surrounding 1,2,3-triazoles made using click chemistry; and the same triazoles are responsible for anion capture. Mistakes made and lessons learnt in anion recognition provide deeper understanding that, together with theory, now provides for computer-aided receptor design. The lessons are acted upon in the creation of two new macrocycles. First, cyanostars are larger and like to capture large anions. Second is tricarb, which also favors large anions but shows a propensity to self-assemble in an orderly and stable manner, laying a foundation for future designs of hierarchical nanostructures. PMID:27340452