Sample records for cations potentiometric titration

  1. Modeling potentiometric titration behavior of glauconite

    NASA Astrophysics Data System (ADS)

    Lu, Weiping; Smith, Edward H.

    1996-09-01

    Potentiometric titration behavior and the effects of dissolution on the titration experiment of a complex natural clay mineral, glauconite, were investigated and interpreted according to surface complexation theory. Considerable dissolution was detected in the time frame of the titration experiments, with the amount of individual cations released from glauconite a function of solution variables and dissolution kinetics. Dissolution effects can be accounted for in model simulations of titration behavior by considering hydrolysis of these cations. Proton surface charge can be calculated by subtracting supernatant titration curves from those of glauconite suspension. Surface complexation models were used to describe titration data. The nonelectrostatic model (NEM) and constant capacitance model (CCM) were implemented using single-site, single-site with dissolution correction, and multi-site with dissolution correction approaches. CCM typically produced better fits of experimental data than NEM based on a statistical fitting parameter. In general, model descriptions are good for background electrolyte concentration ? 0.01 M. In most instances, the correction for dissolution effects yielded a modest improvement in model simulation of experimental data over that obtained by a simple single-site model, but complexity of the model calculations increases greatly when the numerous additional chemical reactions are considered. Incorporation of ion exchange interactions produced no substantive improvement over the other approaches. Consistent with these results, speciation calculations indicate that the > XOH group dominates over other surface species in the pH range of interest, and surface protonation-deprotonation are the most influential reactions with respect to the surface chemistry of the mineral.

  2. 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.

  3. DETERMINATION OF ANTHRANILIC ACID BY POTENTIOMETRIC TITRATION

    Microsoft Academic Search

    Dana Moja; I. Badea

    Cerium (IV) sulfate solution in sulfuric acid was used for the determination of o-aminobenzoic acid in sulfuric acid solution by potentiometric titration. The optima working conditions were set up for the quantitative determination of o-aminobenzoic acid. The method is simple, rapid and reliable. The effects of the acidity of the reaction medium and of the titrant concentration have been investigated.

  4. Potentiometric titrations using pencil and graphite sensors

    Microsoft Academic Search

    Walter S. Selig

    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

  5. Potentiometric titrations of rutile suspensions to 250 C

    SciTech Connect

    Machesky, M.L. [Illinois State Water Survey, Champaign, IL (United States)] [Illinois State Water Survey, Champaign, IL (United States); Wesolowski, D.J.; Palmer, D.A. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.] [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.; Ichiro-Hayashi, Ken [Tohoku Univ., Sendai (Japan). Inst. of Mineralogy, Petrology and Economic Geology] [Tohoku Univ., Sendai (Japan). Inst. of Mineralogy, Petrology and Economic Geology

    1998-04-15

    A stirred hydrogen electrode concentration cell was used to conduct potentiometric titrations of rutile suspensions from 25 to 250 C in NaCl and tetramethylammonium chloride media (0.03 to 1.1 m). Hydrothermal pretreatment of the rutile improved titration reproducibility, decreased titration hysteresis, and facilitated determination of the point of zero net proton charge (pHznpc). These pHznpc values are 5.4, 5.1, 4.7, 4.4, 4.3 ({+-} 0.2 pH units), and 4.2 ({+-} 0.3 pH units) at 25, 50, 100, 150, 200, and 250 C, respectively. The difference between these pHznpc values and 1/2 pK{sub w} (the neutral pH of water) is rather constant between 25 and 250 C ({minus} 1.45 {+-} 0.2). This constancy is useful for predictive purposes and, more fundamentally, may reflect similarities between the hydration behavior of surface hydroxyl groups and water. A three-layer, 1pKa surface complexation model with three adjustable parameters (two capacitance values and one counterion binding constant) adequately described all titration data. The most apparent trend in these data for pH values greater than the pHznpc was the increase in proton release (negative surface charge) with increasing temperature. This reflects more efficient screening by Na{sup +} relative to Cl{sup {minus}}. Replacing Na{sup +} with the larger tetramethylammonium cation for some conditions resulted in decreased proton release due to the less efficient screening of negative surface charge by this larger cation.

  6. 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.

  7. Potentiometric titration of thallium(I) with sodium tetraphenylborate, using ion-selective electrodes.

    PubMed

    Selig, W

    1980-11-01

    Thallium(I) has been determined by potentiometric titration with sodium tetraphenylborate. The titrations were monitored with a double-junction reference electrode and various liquid-membrane and solid-state ion-selective electrodes. The largest end-point breaks were obtained with the liquid-membrane fluoroborate and nitrate electrodes. The cyanide electrode yielded the largest break of the solid-state electrodes tested. Although the magnitude of the end-point break for the cyanide electrode is considerably less than for the above-mentioned liquid-membrane electrodes, routine use of this electrode is preferred because no conditioning is required for the solid-state electrodes. Precision was satisfactory for all electrodes investigated. Thallium(I) can be titrated with tetraphenylborate at any pH from 1.3 to at least 10.2. Other cations that can be precipitated with tetraphenylborate interfere. PMID:18962822

  8. Potentiometric automatic titration (PAT) method to evaluate zero point of charge (ZPC) of variable charge soils

    Microsoft Academic Search

    Katsutoshi Sakurai; Yohichi Ohdate; Kazutake Kyuma

    1989-01-01

    A potentiometric titration technique using an automatic titrator (PAT method) was evaluated for the determination of the ZPC of two different kinds of variable charge soils. The titration mode of PAT was proposed as follows: pre-equilibration for 2 min with continuous stirring, soil: solution ratio of 1 : 10, and cut off time (interval of titrant addition to the system)

  9. POTENTIOMETRIC TITRATION OF AN ACID MIXTURE Background Reading: Harris, 7th

    E-print Network

    McQuade, D. Tyler

    acids is titrated with standard base. Because the pH does not change abruptly enough at either from a derivative plot; that is, (pH)/(vol) vs. volume of base added. A mixture of two acids canPOTENTIOMETRIC TITRATION OF AN ACID MIXTURE Background Reading: Harris, 7th ed., Chapter 11. Skoog

  10. Comparison of salt titration and potentiometric titration methods for the determination of Zero Point of Charge (ZPC)

    Microsoft Academic Search

    Katsutoshi Sakurai; Yohichi Ohdate; Kazutake Kyuma

    1988-01-01

    The salt titration (ST) method was evaluated as a method to determine ZPC in comparison with the potentiometric titration (PT) method for 26 soils with variable charge clays, i.e., Oxisols and Ultisols from Thailand and Andisols from Japan. In addition to the determination of ST-pH0 as the zero point of charge, a calculation procedure (STPT method) was adopted here in

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

    NASA Astrophysics Data System (ADS)

    Villela, R. L. A.; Borges, P. P.; Vysko?il, 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.

  12. Simple home-made sensors for potentiometric titrations. [Nitroform CH(NO/sub 2/)/sub 3/

    SciTech Connect

    Selig, W.

    1982-04-01

    A sensor for potentiometric titrations was prepared by coating a spectroscopic graphite rod with a solution of poly(vinyl chloride) and dioctyphthalate in tetrahydrofuran. The reference electrode was an Ag/AgCl single-junction electrode. The sensor was used in precipitation, acid-base, compleximetric, and redox titrations. 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. Various uncoated types of graphite have also been investigated as sensors, particularly in two applications of interest in the analysis of propellants: the titration of nitroform and perchlorate. Obviously, these sensors can be used also in nonaqueous, or partially nonaqueous media. These sensors may also find use in the potentiometric titration of fluoride vs La(III) or Th(IV).

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

    Microsoft Academic Search

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

    2010-01-01

    A simple but high performance potentiometric titration technique using pulsating sensors has been developed for assay of dissolved oxygen (DO) in water samples down to 10.0?gL?1 levels. The technique involves Winkler titration chemistry, commonly used for determination of dissolved oxygen in water at mgL?1 levels, with modification in methodology for accurate detection of end point even at 10.0?gL?1 levels DO

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  15. Limiting Solubilities and lonization Constants of Sparingly Soluble Compounds: Determination from Aqueous Potentiometric Titration Data Only

    Microsoft Academic Search

    Adriaan P. IJzerman

    1988-01-01

    A new method is described for the concomitant determination of limiting solubilities and ionization constants of sparingly soluble compounds, i.e., drugs. Aqueous potentiometric titration data were recorded both before and after precipitation of the compound and subjected to computer-assisted analysis. Limiting solubilities and ionization constants were obtained for nucleoside transport inhibitors, viz., dilazep, soluflazine, and hexobendine. The method was validated

  16. Non-euclidean simplex optimization. [Application to potentiometric titration of Pu

    Microsoft Academic Search

    1977-01-01

    Geometric optimization techniques useful for studying chemical equilibrium traditionally rely upon principles of euclidean geometry, but such algorithms may also be based upon principles of a non-euclidean geometry. The sequential simplex method is adapted to the hyperbolic plane, and application of optimization to problems such as the potentiometric titration of plutonium is suggested.

  17. Potentiometric titration of chloride in plant tissue extracts using the chloride ion electrode

    Microsoft Academic Search

    R. L. LaCroix; D. R. Keeney; L. M. Walsh

    1970-01-01

    Use of the chloride specific ion electrode to determine chloride in plants was evaluted. Direct potentiometric determination of chloride by the electrode resulted in unreproducible and extremely high chloride values. However, use of this electrode to indicate the end point in titration of the tissue?extract mixture with AgNO3 gave results nearly identical to those obtained by the Mohr procedure. The

  18. Rapid semi-micro potentiometric titration of Ir(IV) with hydrazine sulphate

    SciTech Connect

    Lichtig, J.; ALves, J.C. [Universidade de Sao Paulo (Brazil)

    1994-07-01

    A rapid potentiometric titration of Ir(IV) with hydrazine sulphate is described. 1.0 mg, 0.25 mg and 0.10 mg are determined with precision of 0.5%, 0.8% and 3.0%, respectively. Most of the common ions do not interfere as well as Rh(III). Some determinations of Ir(IV) in ores made with good precision and compared with a spectrophotometric method.

  19. Determination of Hydrogen Fluoride and Uranium (VI) in Crude Uranium Hexafluoride by Hydrolysis and Potentiometric Titration

    Microsoft Academic Search

    Haruka SHINOHARA; Kimie IZAWA; Shigeo TSUJIMURA; Kenji MOTOJIMA

    1967-01-01

    A simple method for determining HF and U(VI) in a hydrolyzed solution of UF6 by alkalimetry is described.About 1 g of UF6 was taken in a polytrifluoromonochloroethylene tube, and hydrolyzed with about 50 ml of water in a closed polyethylene bottle. Using a glass electrode, HF in the hydrolyzed solution was titrated potentiometrically with an alkali solution, after the U(VI)

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

    SciTech Connect

    Engmann, J.; Blanch, H.W.; Prausnitz, J.M. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.

    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.

  1. Effect of Surface Site Interactions on Potentiometric Titration of Hematite (?-Fe2O3) Crystal Faces

    SciTech Connect

    Chatman, Shawn ME; Zarzycki, Piotr P.; Preocanin, Tajana; Rosso, Kevin M.

    2013-02-01

    Time dependent potentiometric pH titrations were used to study the effect of atomic scale surface structure on the protonation behavior of the structurally well defined hematite/aqueous electrolyte interfaces. Our recently proposed thermodynamic model [1,23] was applied to measured acidimetric and alkalimetric titration hysteresis loops, collected from highly organized (001), (012), and (113) crystal face terminations using pH equilibration times ranging from 15 to 30 mins. Hysteresis loop areas indicate that (001) faces equilibrate faster than the (012) and (113) faces, consistent with the different expected ensembles of singly, doubly, and triply coordinated surface sites on each face. Strongly non-linear hysteretic pH-potential relationships were found, with slopes exceeding Nernstian, collectively indicating that protonation and deprotonation is much more complex than embodied in present day surface complexation models. The asymmetrical shape of the acidimetric and alkalimetric titration branches were used to illustrate a proposed steric "leaky screen" repulsion/trapping interaction mechanism that stems from high affinity singly-coordinated sites electrostatically and sterically screening lower affinity doubly and triply coordinated sites. Our data indicate that site interaction is the dominant phenomenon defining surface potential accumulation behavior on single crystal faces of metal oxide minerals.

  2. Origin of two time-scale regimes in potentiometric titration of metal oxides. A replica kinetic Monte Carlo study

    SciTech Connect

    Zarzycki, Piotr P.; Rosso, Kevin M.

    2009-06-16

    Replica Kinetic Monte Carlo simulations were used to study the characteristic time scales of potentiometric titration of the metal oxides and (oxy)hydroxides. The effect of surface heterogeneity and surface transformation on the titration kinetics were also examined. Two characteristic relaxation times are often observed experimentally, with the trailing slower part attributed to surface non-uniformity, porosity, polymerization, amorphization, and other dynamic surface processes induced by unbalanced surface charge. However, our simulations show that these two characteristic relaxation times are intrinsic to the proton binding reaction for energetically homogeneous surfaces, and therefore surface heterogeneity or transformation do not necessarily need to be invoked. However, all such second-order surface processes are found to intensify the separation and distinction of the two kinetic regimes. The effect of surface energetic-topographic non-uniformity, as well dynamic surface transformation, interface roughening/smoothing were described in a statistical fashion. Furthermore, our simulations show that a shift in the point-of-zero charge is expected from increased titration speed and the pH-dependence of the titration measurement error is in excellent agreement with experimental studies.

  3. Potentiometric titrations of Bacillus subtilis cells to low pH and a comparison of modeling approaches

    NASA Astrophysics Data System (ADS)

    Fein, Jeremy B.; Boily, Jean-François; Yee, Nathan; Gorman-Lewis, Drew; Turner, Benjamin F.

    2005-03-01

    To provide constraints on the speciation of bacterial surface functional groups, we have conducted potentiometric titrations using the gram-positive aerobic species Bacillus subtilis, covering the pH range 2.1 to 9.8. Titration experiments were conducted using an auto-titrator assembly, with the bacteria suspended in fixed ionic strength (0.01 to 0.3 M) NaClO 4 solutions. We observed significant adsorption of protons over the entire pH range of this study, including to the lowest pH values examined, indicating that proton saturation of the cell wall did not occur under any of the conditions of the experiments. Ionic strength, over the range studied here, did not have a significant effect on the observed buffering behavior relative to experimental uncertainty. Electrophoretic mobility measurements indicate that the cell wall is negatively charged, even under the lowest pH conditions studied. These experimental results necessitate a definition of the zero proton condition such that the total proton concentration at the pH of suspension is offset to account for the negative bacterial surface charge that tends towards neutrality at pH <2. The buffering intensity of the bacterial suspensions reveals a wide spread of apparent pKa values. This spread was modeled using three significantly different approaches: a Non-Electrostatic Model, a Constant Capacitance Model, and a Langmuir-Freundlich Model. The approaches differ in the manner in which they treat the surface electric field effects, and in whether they treat the proton-active sites as discrete functional groups or as continuous distributions of related sites. Each type of model tested, however, provides an excellent fit to the experimental data, indicating that titration data alone are insufficient for characterizing the molecular-scale reactions that occur on the bacterial surface. Spectroscopic data on the molecular-scale properties of the bacterial surface are required to differentiate between the underlying mechanisms of proton adsorption inherent in these models. The applicability and underlying conceptual foundation of each model is discussed in the context of our current knowledge of the structure of bacterial cell walls.

  4. Diagrams of the formation of In2S3 and In2Se3 films on vitroceramic upon precipitation, according to potentiometric titration

    NASA Astrophysics Data System (ADS)

    Tulenin, S. S.; Bakhteev, S. A.; Yusupov, R. A.; Maskaeva, L. N.; Markov, V. F.

    2013-10-01

    Boundary conditions and ranges of the formation of indium(III) sulfide and selenide upon precipitation by thiocarbamide and selenocarbamide are determined. Potentiometric titration of indium chloride (InCl3) in the concentration range of 0.0001 to 0.100 mol/L by a solution of sodium hydroxide is performed. It is found that the following pH ranges are optimal for In2S3 and In2Se3 film precipitation: from 3.0 to 4.5 and from 9.0 to 14.0. Indium selenide layers 100 to 300 nm thick are prepared on vitroceramic by hydrochemcial precipitation.

  5. Thermodynamics of cationic lipid-DNA complex formation as studied by isothermal titration calorimetry.

    PubMed Central

    Pozharski, Edwin; MacDonald, Robert C

    2002-01-01

    The detailed analysis of the cationic lipid-DNA complex formation by means of isothermal titration calorimetry is presented. Most experiments were done using 1,2-dioleyl-sn-glycero-3-ethylphosphocholine (EDOPC), but basic titrations were also done using DOTAP, DOTAP:DOPC, and DOTAP:DOPE mixtures. Complex formation was endothermic with less than 1 kcal absorbed per mole of lipid or DNA charge. This enthalpy change was attributed to DNA-DNA mutual repulsion within the lamellar complex. The exception was DOTAP:DOPE-containing lipoplex for which the enthalpy of formation was exothermic, presumably because of DOPE amine group protonation. Experimental conditions, namely, direction and titration increment as well as concentration of titrant, which dictate the structure of resulting lipoplex (whether lamellar complex or DNA-coated vesicle), were found to affect the apparent thermodynamics of complex formation. The structure, in turn, influences the biological properties of the lipoplex. If the titration of lipid into DNA was carried out in large increments, the DeltaH was larger than when the injection increments were smaller, a finding that is consistent with increased vesicle disruption under large increments and which is expected theoretically. Cationic lipid-DNA binding was weak in high ionic strength solutions, however, the effective binding constant is within micromolar range because of macromolecular nature of the interaction. PMID:12080142

  6. Effect of fluoride, chloride, bromide, and thiocynate on potentiometric titrations of iron(II)-tin(II) mixtures with cerium(IV)

    SciTech Connect

    Kwok, Y.M.

    1980-07-31

    A two-step curve is expected in the potentiometric titration of Fe(II)-Sn(II) mixtures with Ce(IV) in H/sub 2/SO/sub 4/. Each end point should indicate the respective oxidation of Sn(II) and Fe(II). However, experimentally only one end point was found; it corresponded to the total oxidation of Sn(II) and Fe(II). When this oxidation-reduction reaction was carried out in the presence of Cl/sup -/, the theoretical behavior was observed. The present study was done to ascertain if monovalent anions other than Cl/sup -/ have a similar effect on this oxidation-reduction system. The monovalent species F/sup -/, Br/sup -/, and SCN/sup -/ were selected for this study, and the results indicate that each affects the rate of reaction relative to the ease of oxidation of the individual ions.

  7. A novel 1,10-phenanthroline-sensitive membrane sensor for potentiometric determination of Hg(II) and Cu(II) cations

    Microsoft Academic Search

    Sayed A. M. Marzouk; Wadie T. Al-Ariqui; Saad S. M. Hassan

    2003-01-01

    Preparation, characterization, and applications of a 1,10-phenanthrolinium cation (phenH+)-sensitive potentiometric sensor are described. The sensor incorporates a liquid polymeric membrane consisting of phenH-tetraphenylborate, nitrophenyloctyl ether, and poly(vinyl chloride) as ion exchanger, plasticizer, and polymeric support, respectively. The sensor exhibits a fast and Nernstian response to phenH+ over the concentration range of 6᎒ш-2᎒ц M with a monovalent cationic slope of 58.0ǂ.5

  8. Determination of pKa values of new phenacyl-piperidine derivatives by potentiometric titration method in aqueous medium at room temperature (25±0.5oC).

    PubMed

    Zafar, Shaista; Akhtar, Shamim; Tariq, Talat; Mushtaq, Noushin; Akram, Arfa; Ahmed, Ahsaan; Arif, Muhammad; Naeem, Sabahat; Anwar, Sana

    2014-07-01

    Dissociation constant (pKa) of ten novel phenacyl derivatives of piperidine were determined by potentiometric titration method in aqueous medium at room temperature (25 ±0.5°C). The sample solutions were prepared in deionized water with ionic strength 0.01M and titrated with 0.1M NaOH solution. In addition, ?G values were also calculated. Different prediction software programs were used to calculate pKa values too and compared to the experimentally observed pKa values. The experimental and theoretical values were found in close agreement. The results obtained in this research would help to predict the good absorption of the studied compounds and can be selected as lead molecules for the synthesis of CNS active agents because of their lipophilic nature especially compound VII. PMID:25015461

  9. Titrations in non-aqueous media: potentiometric investigation of symmetrical and unsymmetrical tetra-aryl porphyrins with 4-nitrophenyl and 4-aminophenyl substituents in nitrobenzene solvent

    Microsoft Academic Search

    Necla Gündüz; Turgut Gündüz; Mustafa Hayvali

    1999-01-01

    The basicity of the symmetrical and unsymmetrical tetraphenylporphyrins, namely 5,10,15,20-tetraphenylporphyrin (I) (references), 5-(4-nitrophenyl)-10,15,20-triphenylporphyrin (II), a mixture of 5,10-bis(4-nitrophenyl)-15,20-diphenylporphyrin and 5,15-bis(4-nitrophenyl)-10,20-diphenylporphyrin (III), 5,10,15-tris(4-nitrophenyl)-20-phenylporphyrin (IV), 5,10,15,20-tetrakis(4-nitrophenyl)porphyrin (V), 5-(4-aminophenyl)-10,15,20-triphenylporphyrin (VI), a mixture of 5,10-bis(4-aminophenyl)-15,20-diphenylporphyrin and 5,15-bis(4-aminophenyl)-10,20-diphenylporphyrin (VII), 5,10,15-tris(4-aminophenyl)-20-phenylporphyrin (VIII) and 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (IX), was investigated potentiometrically in nitrobenzene solvent. This investigation showed that these compounds are basic rather than acidic. Although they can not

  10. UPTAKE OF METAL IONS BY A NEW CHELATING ION EXCHANGE RESIN. PART 3: PROTONATION CONSTANTS VIA POTENTIOMETRIC TITRATION AND SOLID STATE 31P NMR SPECTROSCOPY

    Microsoft Academic Search

    K. L. Nash; P. G. Rickert; J. V. Muntean; S. D. Alexandratos

    1994-01-01

    A new chelating ion exchange resin which incorporates methylenediphosphonate, carboxylate, and sulfonate functional groups in a polystyrene-divinylbenzene matrix has been prepared. This resin exhibits exceptionally high affinity for polyvalent cations even from moderately acidic aqueous media. Metal ion coordination occurs primarily at the diphosphonate group with the secondary binding sites contributing to charge neutralization when necessary and possible, and to

  11. 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)

  12. Ionometric determination of quaternary ammonium cations in industrial extraction reagents and sewage

    SciTech Connect

    Kokovkin, V.V.; Nemirovskii, A.M.; Kravchenko, L.Kh.; Smolyakov, B.S.

    1988-01-01

    When extraction reagents based on salts of quaternary ammonium bases (QAS) are used in the technology of purification of rare earth elements (REE), the problem arises of determining QAS in technological and dilute aqueous solutions (circulating waters and sewage). A direct method of determining cations of QAS is known, based on the use of ion-selective electrodes, reversible to hydrophobic cations. Two types of procedures can be distinguished within the framework of this method: potentiometric titration and direct potentiometry. In this work the authors discuss the possibilities of both types for practical use in industrial analysis.

  13. Potentiometric batch and flow injection analysis of betaine hydrochloride.

    PubMed

    Badawy, Sayed S; Youssef, Ahmed F A; Mutair, Ali A

    2007-01-01

    Novel PVC membrane electrodes for the determination of betaine ion based on the formation of betaine-tetraphenylborate (Be-TPB) and betaine-phosphotungstate (Be-PT) ion-exchangers as electroactive materials are described. The sensors show a fast, stable, near Nernstian response for 6.92 x 10(-6) to 7.94 x 10(-3) M and 1.0 x 10(-4) to 1.0 x 10(-2) M betaine hydrochloride (Be.Cl) in case of Be-TPB electrode applying batch and flow injection analysis (FIA), respectively, and 2.95 x 10(-5) to 2.26 x 10(-3) M and 3.16 x 10(-5) to 1.0 x 10(-2) M in case of Be-PT electrode for batch and FIA electrodes, respectively, at 25 degrees C over the pH range of 3.5-10 with a cationic slope of 60.2 and 59.1 mV decade(-1) and a fast potential response of < or =15 s. The lower detection limits are 7.94 x 10(-6) and 3.18 x 10(-5) M Be.Cl for Be-TPB and Be-PT electrodes, respectively. Selectivity coefficient data for some common inorganic cations, sugars, amino acids and the components other than betaine, of the mixed drug investigated show negligible interference. The electrodes have been applied to the direct potentiometric determination of betaine hydrochloride in water and in a pharmaceutical preparation under batch and FIA conditions. Potentiometric titrations of Be.Cl with NaTPB and PTA as titrants were monitored with the developed betaine electrodes as an end point indicator electrode. The determination of Be.Cl shows an average recovery of 100.8% with mean relative standard deviation of 0.61%. The effect of temperature on the electrodes was also studied. PMID:17822229

  14. Luminescence titrations of polyelectrolytes 

    E-print Network

    Alvarez, Edwin Rene

    1986-01-01

    of polyelectrolyte has been added to the lumophore solution. The equivalent weight (EW) of the polyelectrolyte (Le. & grams polymer per mole of charged sites) can be determined if the concentration of the polyelectrolyte (% w/v) is known or its concentration... are to be obtained. The binding constant, K, of the lumophore to the polyelectrolyte determines the shape of the titration curves. An appropiate cationic probe is identified. The placement of ionic groups within the molecular structure of a polymer produces...

  15. Studies on the solid acidity of heated and cation-exchanged montmorillonite using n-butylamine titration in non-aqueous system and diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy

    NASA Astrophysics Data System (ADS)

    Liu, Hongmei; Liu, Dong; Yuan, Peng; Tan, Daoyong; Cai, Jingong; He, Hongping; Zhu, Jianxi; Song, Zhiguang

    2013-06-01

    The effects of heating and cation exchange on the solid acidity of montmorillonite were investigated using n-butylamine titration in non-aqueous system and diffuse reflectance Fourier transform infrared spectroscopy. The number of total, Brønsted, and Lewis acid sites showed the same modulation tendency with increasing heating temperature, reaching a maximum at 120 °C and subsequently decreasing until it reaches a minimum at 600 °C. The Lewis acid sites result from unsaturated Al3+ cations, and their number increased with the heating temperature due to the dehydration and dehydroxylation of montmorillonite. The generation and evolution of Brønsted acidity were mainly related to interlayer-polarized water molecules. Water adsorbed on the unsaturated Al3+ ions also acted as a Brønsted acid. The acid strength of the Brønsted acid sites was dependent on the polarization ability of the exchangeable cation, the amount of interlayer water, and the degree of dissociation of the interlayer water coordinated to exchangeable cations. All cation-exchanged montmorillonites exhibited different numbers of acid sites and various distributions of acid strength. Brønsted acidity was predominant in Al3+-exchanged montmorillonite, whereas the Na+- and K+-exchanged montmorillonites showed predominantly Lewis acidity. Moreover, Mg2+- and Li+-exchanged montmorillonites exhibited approximately equal numbers of Brønsted and Lewis acid sites. The Brønsted acidity of cation-exchanged montmorillonite was positively correlated with the charge-to-radius ratios of the cations, whereas the Lewis acidity was highly dependent on the electronegativity of the cations. The acid strengths of Al3+- and Mg2+-exchanged montmorillonites were remarkably higher than those of monovalent cation-exchanged montmorillonites, showing the highest acid strength ( H 0 ? -3.0). Li+- and Na+-exchanged montmorillonites exhibited an acid strength distribution of -3.0 < H 0 ? 4.8, with the acid strength ranging primarily from 1.5 to 3.3 in Li+-exchanged montmorillonite, whereas only weaker-strength acid sites (1.5 < H 0 ? 4.8) were present in K+-exchanged montmorillonite. The results of the catalysis experiments indicated that montmorillonite promoted the thermal decomposition of the model organic. The catalytic activity showed a positive correlation with the solid acidity of montmorillonite and was affected by cation exchange, which occurs naturally in geological processes.

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

    PubMed Central

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

    2004-01-01

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

  17. Dithizone modified gold nanoparticles films for potentiometric sensing.

    PubMed

    Wo?nica, Emilia; Wójcik, Micha? M; Wojciechowski, Marcin; Mieczkowski, Józef; Bulska, Ewa; Maksymiuk, Krzysztof; Michalska, Agata

    2012-05-15

    For the first time, application of a membrane composed of gold nanoparticles decorated with complexing ligand for potentiometric sensing is shown. Gold nanoparticles drop cast from a solution form a porous structure on a substrate electrode surface. Sample cations can penetrate the gold nanoparticles layer and interact with ligand acting as a charged ionophore, resulting in Nernstian potentiometric responses. Anchoring of complexing ligand on the gold surface abolishes the necessity of ionophore application. Moreover, it opens the possibility of preparation of potentiometric sensors using chelators of significantly different selectivity patterns further enhanced by the absence of polymeric membrane matrix. This was clearly seen, for example, for gold nanoparticles stabilizing the applied ligand-dithizone-thiol conformation leading to a high potentiometric selectivity toward copper ions, much higher than that of ionophores typically used to induce selectivity for polymeric ion-selective membranes. PMID:22510225

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

    PubMed Central

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

    2014-01-01

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

  19. Modern Directions for Potentiometric Sensors

    PubMed Central

    Bakker, Eric; Chumbimuni-Torres, Karin

    2009-01-01

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

  20. Acid-base titrations for polyacids: Significance of the pK sub a and parameters in the Kern equation

    NASA Technical Reports Server (NTRS)

    Meites, L.

    1978-01-01

    A new method is suggested for calculating the dissociation constants of polyvalent acids, especially polymeric acids. In qualitative form the most significant characteristics of the titration curves are demonstrated and identified which are obtained when titrating the solutions of such acids with a standard base potentiometrically.

  1. Potentiometric determination of acid dissociation constants (p K a) for human and veterinary antibiotics

    Microsoft Academic Search

    Zhimin Qiang; Craig Adams

    2004-01-01

    This work determined the acid dissociation constants (pKa) of 26 common human and veterinary antibiotics by potentiometric titration. Selected antibiotics consisted of sulfonamides, macrolides, tetracyclines, fluoroquinolones, and other miscellaneous antibiotics. After validation of analysis methods using phosphoric acid as a model compound, a second-derivative (?2pH\\/?V2) method was primarily applied to determining pKa's from titration curves for most antibiotics due to

  2. Hydrogen Bonding and Solvent Effects on Complexation of Alkali Metal Cations by Lower Rim Calix[4]arene Tetra( O -[ N -acetyl- D -phenylglycine methyl ester]) Derivative

    Microsoft Academic Search

    VLADISLAV TOMISIC ´; NIVES GALIC ´; Branimir Bertoša; Leo Frkanec; Vladimir Simeon; Mladen Žini?

    2005-01-01

    Complexation of alkali metal cations with 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis(O-methyl-D-?-phenylglycylcarbonylmethoxy)calix[4]arene (L) was studied by means of spectrophotometric, conductometric and potentiometric titrations at 25 °C. The solvent effect on the binding ability of L was examined by using two solvents with different affinities for hydrogen bonding, viz. methanol and acetonitrile. Despite the presence of intramolecular NH···O=C hydrogen bonds in L, which need to be disrupted

  3. POTENTIOMETRIC DETERMINATION OF SMALL AMOUNTS OF HEXAVALENT URANIUM IN URANIUM DIOXIDE

    Microsoft Academic Search

    J. Minczewski; R. Przytycka; L. Kohman

    1958-01-01

    For determination of small amounts of U(6+) in UOâ use is made of ; potentiometric titration with a solution of Tiâ(SOâ)â. To 4 to ; 5 g UCâ in a Pt-dish are added 10 ml concentrated HF, 30 ml water, and the ; mixture is heated until a green precipitate (UFâ) is formed containing no ; black particles. Thereafter the

  4. ACIDBASE TITRATION NUMERICAL SIMULATOR

    Microsoft Academic Search

    Lorentz JÄNTSCHI; Delia GLIGOR; Mihaela Ligia

    2003-01-01

    The analytical methods of qualitative and quantitative determination of ions in solutions are very flexible to automation. The present work is focus on modeling the process of titration and presents a numerical simulation of acid-base titration. A PHP program to compute all iterations in titration process that solves a 3 rd rank equation to find value of pH for was

  5. An elevated temperature titration calorimeter

    SciTech Connect

    Smith, J.R.; Zanonato, P.L.; Choppin, G.R. (Florida State Univ., Tallahassee, FL (USA). Dept. of Chemistry)

    1991-06-01

    A variable-temperature (313 K to 353 K) titration calorimeter of high sensitivity has been constructed. The purpose of the calorimeter is to study temperature effects on the enthalpies of complex formation and of other reactions of metal cations such as hydrolysis and precipitation. Operation of the calorimetric system, including that final calculation of the heat released during titration, is automatic via computer control. Calibration tests of the calorimeter using 2-amino-2-hydroxymethyl-1,3-propanediol gave -(46.0 {plus minus} 0.3) kJ mol{sup {minus}1} and -(46.2 {plus minus} 0.2) kJ mol{sup {minus}1} for the enthalpy of protonation, at 318 K and at 343 K, respectively. For titrations of 2-bis(2-hydroxyethyl) amino-2-hydroxymethyl-1,3-propanediol, enthalpy of protonation values of -(28.4 {plus minus} 0.3) kJ mol{sup {minus}1} and -(29.3 {plus minus} 0.2) kJ mol{sup {minus}1} were obtained at 318 K and at 343 K, respectively. 6 refs., 3 figs., 2 tabs.

  6. Modeling sorption of divalent metal cations on hydrous manganese oxide using the diffuse double layer model

    USGS Publications Warehouse

    Tonkin, J.W.; Balistrieri, L.S.; Murray, J.W.

    2004-01-01

    Manganese oxides are important scavengers of trace metals and other contaminants in the environment. The inclusion of Mn oxides in predictive models, however, has been difficult due to the lack of a comprehensive set of sorption reactions consistent with a given surface complexation model (SCM), and the discrepancies between published sorption data and predictions using the available models. The authors have compiled a set of surface complexation reactions for synthetic hydrous Mn oxide (HMO) using a two surface site model and the diffuse double layer SCM which complements databases developed for hydrous Fe (III) oxide, goethite and crystalline Al oxide. This compilation encompasses a range of data observed in the literature for the complex HMO surface and provides an error envelope for predictions not well defined by fitting parameters for single or limited data sets. Data describing surface characteristics and cation sorption were compiled from the literature for the synthetic HMO phases birnessite, vernadite and ??-MnO2. A specific surface area of 746 m2g-1 and a surface site density of 2.1 mmol g-1 were determined from crystallographic data and considered fixed parameters in the model. Potentiometric titration data sets were adjusted to a pH1EP value of 2.2. Two site types (???XOH and ???YOH) were used. The fraction of total sites attributed to ???XOH (??) and pKa2 were optimized for each of 7 published potentiometric titration data sets using the computer program FITEQL3.2. pKa2 values of 2.35??0.077 (???XOH) and 6.06??0.040 (???YOH) were determined at the 95% confidence level. The calculated average ?? value was 0.64, with high and low values ranging from 1.0 to 0.24, respectively. pKa2 and ?? values and published cation sorption data were used subsequently to determine equilibrium surface complexation constants for Ba2+, Ca2+, Cd 2+, Co2+, Cu2+, Mg2+, Mn 2+, Ni2+, Pb2+, Sr2+ and Zn 2+. In addition, average model parameters were used to predict additional sorption data for which complementary titration data were not available. The two-site model accounts for variability in the titration data and most metal sorption data are fit well using the pKa2 and ?? values reported above. A linear free energy relationship (LFER) appears to exist for some of the metals; however, redox and cation exchange reactions may limit the prediction of surface complexation constants for additional metals using the LFER. ?? 2003 Elsevier Ltd. All rights reserved.

  7. Micromechanical potentiometric sensors

    DOEpatents

    Thundat, Thomas G. (Knoxville, TN)

    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.

  8. Novel membrane potentiometric sulfate ion sensor based on zinc-phthalocyanine for the quick determination of trace amounts of sulfate.

    PubMed

    Ganjali, Mohammad Reza; Pourjavid, Mohammad Reza; Shamsipur, Mojtaba; Poursaeri, Taherh; Rezapour, Morteza; Javanbakht, Mehran; Sharghi, Hashem

    2003-07-01

    Poly(vinyl chloride) (PVC) based membranes of zinc-phthalocyanine (ZPC) with hexadecyltrimethylammonium bromide (HTAB) as a cation excluder, and dibutyl phthalate (DBP) and benzyl acetate (BA) as plasticizing solvent mediators were prepared and investigated as a SO4(2-) selective electrode. The best performance was observed with a membrane having a composition of ZPC-PVC-HTAB-BA in a ratio of 5%:32%:3%:60%, which works well over a wide concentration range (1.0 x 10(-2) - 1.0 x 10(-6) M) with a Nemstian slope of -29.2 mV per decade of activity, between the pH values of 2.0 to 7.0. This sensor shows a very fast response time of 10 s, and can be used over a period of 2 months with good reproducibility. The proposed sensor displays excellent selectivity for SO4(2-) over a large number of common inorganic anions. The sensor has been successfully applied for the direct and indirect determination of sulfate and zinc in zinc sulfate tablets, respectively. It was also used as an indicator electrode in the potentiometric titration of sulfate ions with barium ions. PMID:12880081

  9. Peptide-lanthanide cation equilibria in aqueous phase. I. Bound shifts for L-carnosine-praseodymium complexes

    NASA Astrophysics Data System (ADS)

    Mossoyan, J.; Asso, M.; Benlian, D.

    L-Carnosine complexes of Pr 3+ were characterized in aqueous solution by 1H NMR and potentiometric titration. A rigorous treatment of chemical shifts and pH variation data with lanthanide concentration is presented. Two different forms of the peptide ligand, forming simultaneously two complexes, were taken into account. At low pH values the cation is only coordinated at the carboxylate site of the ligand in a weak complex ( ?2 = 6) whereas in neutral solution a stronger complex ( ?1 = 37) is present as a consequence of the deprotonation of the imidazole ring. The computation of induced bound shifts † 2 and ?1 for resonating nuclei of the peptide in both forms yields consistent figures. These provide the experimental basis for a conformational model which is usually not obtainable for labile complexes with low stability constants.

  10. Titration Curves: Fact and Fiction.

    ERIC Educational Resources Information Center

    Chamberlain, John

    1997-01-01

    Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…

  11. Potentiometric and UV–Vis Spectroscopy Studies of Citrate with the Hexaquo Fe and Cr Metal Ions

    Microsoft Academic Search

    Yahia Z. Hamada; Brandon L. Carlson; Jeremy T. Shank

    2003-01-01

    We are reporting the interaction and behavior of citrate with the hexaqo Fe(NO3)3, and Cr(NO3)3 (Fe and Cr will be used as shorthand notation for the two metal ions) using ultraviolet and visible spectroscopy (UV–Vis). The identity of the proposed metal complexes was confirmed by using the potentiometric titration technique. With the Fe\\/citric acid system, it appeared that the simple

  12. Iodine losses during Winkler titrations

    NASA Astrophysics Data System (ADS)

    Knapp, George P.; Stalcup, Marvel C.; Stanley, Robert J.

    1991-01-01

    An experiment designed to measure iodine loss during the aliquot version of the Winkler titration for dissolved oxygen in seawater shows that 0.01-0.03 ml l -1 equivalent oxygen is lost at typical oceanic concentrations in the method presently used. A standardization technique, which mimics that employed during the titration of seawater samples, compensates for this iodine loss throughout the oceanic range. This result, contradicting an earlier report by GREEN and CARRITT (1966, Analyst, 91, 207-208), demonstrates that the whole-bottle method of oxygen titration is not to be preferred over the aliquot method.

  13. Novel sensors for potassium, calcium and magnesium ions based on a silicon transducer as a light-addressable potentiometric sensor

    Microsoft Academic Search

    Atsushi Seki; Kentaro Motoya; Sinya Watanabe; Izumi Kubo

    1999-01-01

    Potentiometric cation sensors using a silicon transducer, light-addressable potentiometric sensor (LAPS) and ion-recognition elements are described, and their performance are discussed. In the silicon transducer, an Al2O3 layer was used as an insulating layer. On the surface of the Al2O3 layer, ion-recognition element such as valinomycin, 18-crown-6 ether, bis[di(n-octylphenyl)phosphato]calcium(II) and ETH1117 were immobilized in the matrix of poly(vinyl chloride) film.

  14. Potentiometric Determination of Phytic Acid and Investigations of Phytate Interactions with Some Metal Ions.

    PubMed

    Marolt, Gregor; Pihlar, Boris

    2015-01-01

    Determination of correct amount (concentration) of phytic acid is of vital importance when dealing with protonation and/or metal complexation equilibria. A novel approach for precise and reliable assay of phytic acid, based on the difference between end points by potentiometric titration, has been presented. Twelve phytic acid protons are classified into three groups of acidity, which enables detection of 2 to 3 distinct equivalent points (EPs) depending on experimental conditions, e.g. counter-ion concentration. Using the differences between individual EPs enables correct phytate determination as well as identification of potential contamination and/or determination of initial protonation degree. Impact of uncertainty of phytate amount on the calculation of protonation constants has been evaluated using computer simulation program (Hyperquad2013). With the analysis of titration curves different binding sites on phytate ligand have been proposed for complexation of Ca2+ and Fe3+ ions. PMID:26085413

  15. [Accelerated titration design].

    PubMed

    Minami, H

    2000-09-01

    To reduce the number of patients treated at low and biologically inactive doses in phase I trials of anticancer agents, attempts to decrease the number of patients per dose level and to conduct a larger dose escalation have been made. Among them, accelerated titration designs were proposed and evaluated by simulation; designs 2 and 4 were reported to be acceptable (J Natl Cancer Inst 89: 1138-1147, 1997). Both designs 2 and 4 included only one patient per cohort during the initial accelerated phase. Dosage steps for the accelerated phase were defined using the modified Fibonacci method for design 2 and 100% escalation for design 4, respectively. The accelerated phase continued until one patient experienced dose-limiting toxicity or two patients experienced grade 2 toxicities. Dose escalation was conducted based on the information from the first course in design 2 and from the first three courses in design 4. In the simulation, both designs successfully reduced the total number of patients and the number of undertreated patients without increasing the number of overtreated patients. However, the safety of design 4 was assured as long as all patients received three courses of chemotherapy, which is unusual in phase I studies in Japan. Decision-making on dose escalation based on the information on toxicity in three courses might be cumbersome. Therefore, in Japan, design 2 would be recommended among the proposed accelerated designs. The performance of the design should be investigated by applying it to actual phase I studies and by evaluating the number of undertreated and overtreated patients. PMID:11016010

  16. A mechanistic description of Ni and Zn sorption on Na-montmorillonite Part I: Titration and sorption measurements

    Microsoft Academic Search

    Bart Baeyens; Michael H. Bradbury

    1997-01-01

    In this paper experimental investigations into the acid\\/base titration characteristics of Na-montmorillonite and the sorption behaviour of Ni and Zn under a wide variety of conditions are presented. From these measurements the dominant sorption mechanisms could be deduced. In the following paper (Bradbury and Baeyens, 1997) the titration and sorption data are analysed to determine the parameters in cation exchange

  17. High frequency titration of amines in nonaqueous solutions

    E-print Network

    Witmer, William Byron

    1958-01-01

    -PROPYLAMINE. . . . . . . 1$ II TITRATION OF DI-n-PROFYLAMINE . ~ ~ ~ o 15 III TITRATION OF TRIETHYLAMINE. . . ~ ~ . ~ 17 TITRATION OF ETHANOLAMINE 19 V TITRATION OF PYRIDINE. . . . . o. . . 21 VI TITRATION OF ANILINE. ~ ~ i ~ 2) VII VIII TITRATION OF m...-BROMOANILINE. . . . . . 25 SUMMARY OF RESULTS. LIST OF FIGURES Page TITRATI05 OF n-PROPYLAMINE, . . . . . 14 TITRATION OF DI-n-PROPYLAMINE . . . . 16 TITRATION OF TRIETHYLAMINE. TITRATION OF ETHANOLAMINE TITRATION OF PYRIDINE . ~ 18 20 22 TITRATION OF ANILINE...

  18. Potentiometric assessment of iron release during ferritin reduction by exogenous agents.

    PubMed

    Vladimirova, Lilia S; Kochev, Valery K

    2010-09-01

    This work studied the possibilities for quantitative determination of iron mobilization in connection with ferritin reduction by ascorbic acid (vitamin C) and sodium dithionite in vitro. The iron storage protein was incubated with an excess of reductant in aerobic conditions in the absence of complexing agents in the medium. The release of Fe(2+) was let to go to completion, and the overall content of Fe(2+) in the solution was evaluated with the aid of potentiometric titration using Ce(4+) as an oxidizing titrant. Results suggest a moderate iron efflux under the influence of the chosen reducing agents. Although such a reduction of the protein mineral core by dihydroxyfumarate contributes greatly to the iron mobilization, ferritin behavior with vitamin C and dithionite seems to be different. Although redox properties of dihydroxyfumarate are determined by hydroxyl groups similar to those of ascorbic acid, the two compounds differ significantly in structure, and this could be the basis for an explanation of the specificities in their interaction with ferritin. As revealed by the study, potentiometric titration promises to be a reliable tool for evaluation of the amount of Fe(2+) present in the solution as a result of the reduction of the ferritin's mineral core. PMID:20434425

  19. High-sensitivity titration microcalorimeter

    NASA Astrophysics Data System (ADS)

    Velikov, A. A.; Grigoryev, S. V.; Chuikin, A. V.

    2015-02-01

    A differential titration microcalorimeter for studying intermolecular interactions in solutions has been designed. To increase the speed of the instrument, the dynamic correction method has been used. It has been shown that electrical calibration of the microcalorimeter is consistent with its chemical calibration. The use of the instrument for measuring the integral heats of dilution of 1-propanol has been demonstrated.

  20. Polyelectrolyte Titration: Theory and Experiment

    E-print Network

    I. Borukhov; D. Andelman; R. Borrega; M. Cloitre; L. Leibler; H. Orland

    2000-05-18

    Titration of methacrylic acid / ethyl-acrylate copolymers is studied experimentally and theoretically. At low salt concentrations, this polyacid exhibits a plateau in the titration curve below the neutralization point. The plateau has been often attributed to a first-order phase transition associated with polymer conformational changes. We argue that the specific shape of titration curves of hydrophobic polyelectrolytes is due to electrostatics and does not necessarily require a conformation change of the polyelectrolyte chains. We calculate the free energy at the mean-field level and its first-order (one loop) correction using a loop expansion. The latter is dominated by Debye-Huckel--like charge-charge correlations as well as by correlations between dissociation sites along the polymer chain. We show that the one-loop corrections to the free energy lead to titration curves that agree with experiments. In particular, the model explains the decrease of the pH at the plateau when the polymer concentration is increased or when salt is added to the solution.

  1. 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…

  2. ChemTeacher Resource: Acid Base Titration

    NSDL National Science Digital Library

    University of Southern California

    2011-01-01

    Acid-Base titration applet that plots pH changes as student adds acid or base. Gives choice of indicators. Compares plots for titration of traditional solution and a buffered solution. Can alter starting concentrations.

  3. Photochemical Titration of Imine Chelons

    Microsoft Academic Search

    J. M. Fitzgerald; John L. Beck

    1970-01-01

    A photochemical titration for determination of the analytically useful imine chelons 1,10-phenanthroline and 2,4,6-tripyridyl-s-triazine has been developed. The titrant, iron(II), is photolytically generated from iron(III)-citrate; citrate buffers the solution permitting rapid reaction of iron(II) with the chelons. A single mercury vapor arc serves as source for both photolysis and the photometric end point (546 nm); 1 to 40 micromoles of

  4. Sequential potentiometric complexometric redox determination of iron(III) and cobalt(II) with application to alloys.

    PubMed

    Rao, B V; Gopinath, R

    1989-08-01

    A simple potentiometric method is presented for successive determination of iron(III) and cobalt(II) by complexometric titration of the iron(III) with EDTA at pH 2 and 40 degrees , followed by redox titration of the cobalt(II) complex with 1,10-phenanthroline or 2,2'-bipyridyl at pH 4-5 and 40 degrees , with gold(III). There is no interference in either determination from common metal ions other than copper(II), which severely affects the cobalt determination but can be removed by electrolysis. The method has been successfully applied to determination of iron and cobalt in Kovar and Alnico magnet alloys. PMID:18964822

  5. Determination of polyhexamethylene biguanide hydrochloride using photometric colloidal titration with crystal violet as a color indicator.

    PubMed

    Masadome, Takashi; Miyanishi, Takaaki; Watanabe, Keita; Ueda, Hiroshi; Hattori, Toshiaki

    2011-01-01

    A solution of polyhexamethylene biguanide hydrochloride (PHMB-HCl) was titrated with a standard solution of potassium poly(vinyl sulfate) (PVSK) using crystal violet (CV) as an photometric indicator cation. The end point was detected by a sharp absorbance change due to an abrupt decrease in the concentration of CV. A linear relationship between the concentration of PHMB-HCl and the end-point volume of the titrant existed in the concentration range from 2 to 10 × 10(-6) eq mol L(-1). Back-titration was based on adding an excess amount of PVSK to a sample solution containing CV, which was titrated with a standard solution of poly(diallyldimethylammonium chloride) (PDADMAC). The calibration curve of the PHMB-HCl concentration to the end point volume of the titrant was also linear in the concentration range from 2 to 8 × 10(-6) eq mol L(-1). Both photometric titrations were applied to the determination of PHMB-HCl in a few contact-lens detergents. Back-titration showed a clear end point, but direct titration showed an unclear end point. The results of the back-titration of PHMB-HCl were compared with the content registered in its labels. PMID:21828919

  6. Actinide cation-cation complexes

    SciTech Connect

    Stoyer, N.J. [Lawrence Berkeley Lab., CA (United States); Seaborg, G.T. [Lawrence Livermore National Lab., CA (United States)

    1994-12-01

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO{sub 2}{sup +}) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO{sub 2}{sup +}; therefore, cation-cation complexes indicate something unique about AnO{sub 2}{sup +} cations compared to actinide cations in general. The first cation-cation complex, NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO{sub 2}{sup +} species, the cation-cation complexes of NpO{sub 2}{sup +} have been studied most extensively while the other actinides have not. The only PuO{sub 2}{sup +} cation-cation complexes that have been studied are with Fe{sup 3+} and Cr{sup 3+} and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, NpO{sub 2}{sup +}{center_dot}Th{sup 4+}, PuO{sub 2}{sup +}{center_dot}UO{sub 2}{sup 2+}, and PuO{sub 2}{sup +}{center_dot}Th{sup 4+} at an ionic strength of 6 M using LIPAS are 2.4 {plus_minus} 0.2, 1.8 {plus_minus} 0.9, 2.2 {plus_minus} 1.5, and {approx}0.8 M{sup {minus}1}.

  7. Modeling of light-addressable potentiometric sensors

    Microsoft Academic Search

    Luigi Colalongo; Giovanni Verzellesi; Daniele Passeri; A. Lui; Paolo Ciampolini; Massimo V. Rudan

    1997-01-01

    In this paper, the extension of numerical simulation techniques to the analysis of light-addressable potentiometric sensors (LAPS) is discussed in detail. To this purpose, proper physical models of both the ion-sensitive and the photo-sensitive transduction mechanisms have been incorporated into the framework of a general-purpose device simulator. A self-consistent, accurate picture of charge transport within the device under the combined

  8. Heparin assay and protamine titration.

    PubMed

    Anido, G; Freeman, D J

    1981-10-01

    By utilizing the fact that heparin and protamine sulfate directly neutralize each other, it is possible to quickly detect excess levels of protamine (anti-heparin activity) by back-titrating a plasma specimen with predetermined amounts of heparin. The approach suggested allows for the simultaneous definition of low levels of heparin, and incorporates an equally rapid and accurate measurement of high heparin concentrations. The methodology presented employs heparin assays using the "Protopath" technic. The concept appears to be applicable to other test systems currently designed to monitor heparin activity. PMID:7293964

  9. Sorption and desorption of quaternary amine cations on clays

    Microsoft Academic Search

    Z. Zhong Zhang; Donald L. Sparks; Noel C. Scrivner

    1993-01-01

    The authors have studied the sorption and desorption of three quaternary amines, namely, nonyltrimethylammonium, dodecyltrimethylammonium, and hexadecyltrimethylammonium, on homoionic Na- and K-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were sorbed on the montmorillonite when the added amines were less than 70% of the cation-exchange capacity of the montmorillonite. Sorption of

  10. Coulometric titrations of bases in propylene carbonate using hydrogenpalladium and deuteriumpalladium generator electrodes.

    PubMed

    Mihajlovi?, R P; Jaksi?, L N; Vajgand, V V

    1992-12-01

    The application of hydrogen and deuterium ions obtained by anodic oxidation of hydrogen and deuterium dissolved in palladium, for the coulometric determination of bases (both individual and in mixtures) in propylene carbonate, is described. The current-potential curves at a palladium anode for supporting electrolyte indicator, titrated bases, hydrogen dissolved in palladium and deuterium dissolved in palladium showed that hydrogen and deuterium are oxidized at much less positive potentials than the oxidation potentials of other substances present in the solution. The generated H(+) and D(+) ions were used for the titration of bases (pyridine, quinoline, triethylamine, n-butylaniline, 2,2'-dipiridyl and aminopyrine) with visual and potentiometric detection. The oxidation of hydrogen and deuterium proceeded with 100% current efficiency. Two-component mixtures of bases (aliphatic + aromatic amine) were titrated successfully by using two indicators, Eosin and Crystal Violet. The relative error of the determination with respect to each individual base determination, was less than 2.5% for quantities of bases ranging from 1 to 3 mg. PMID:18965575

  11. Theoretical considerations and a simple method for measuring alkalinity and acidity in low-pH waters by gran titration

    USGS Publications Warehouse

    Barringer, J.L.; Johnsson, P.A.

    1996-01-01

    Titrations for alkalinity and acidity using the technique described by Gran (1952, Determination of the equivalence point in potentiometric titrations, Part II: The Analyst, v. 77, p. 661-671) have been employed in the analysis of low-pH natural waters. This report includes a synopsis of the theory and calculations associated with Gran's technique and presents a simple and inexpensive method for performing alkalinity and acidity determinations. However, potential sources of error introduced by the chemical character of some waters may limit the utility of Gran's technique. Therefore, the cost- and time-efficient method for performing alkalinity and acidity determinations described in this report is useful for exploring the suitability of Gran's technique in studies of water chemistry.

  12. Field Test for Titratable Acidity in Milk

    Microsoft Academic Search

    H. O. Jaynes; M. G. Pearsall; H. C. Holt

    1981-01-01

    A field test was developed to enable milk haulers to assess titratable acidity at pickup. The test involved adding a volume of milk to a set volume of standard base in calibrated screwcapped test tubes. Judgment was based on final color after adding phenolphthalein. No color change indicated titratable acidity above a chosen cutoff point, and the typical pink color

  13. Potentiometric sensing array for monitoring aquatic systems.

    PubMed

    Pankratova, Nadezda; Crespo, Gastón A; Afshar, Majid Ghahraman; Crespi, Miquel Coll; Jeanneret, Stéphane; Cherubini, Thomas; Tercier-Waeber, Mary-Lou; Pomati, Francesco; Bakker, Eric

    2015-05-12

    Since aquatic environments are highly heterogeneous and dynamic, there is the need in aquatic ecosystem monitoring to replace traditional approaches based on periodical sampling followed by laboratory analysis with new automated techniques that allow one to obtain monitoring data with high spatial and temporal resolution. We report here on a potentiometric sensing array based on polymeric membrane materials for the continuous monitoring of nutrients and chemical species relevant for the carbon cycle in freshwater ecosystems. The proposed setup operates autonomously, with measurement, calibration, fluidic control and acquisition triggers all integrated into a self-contained instrument. Experimental validation was performed on an automated monitoring platform on lake Greifensee (Switzerland) using potentiometric sensors selective for hydrogen ions, carbonate, calcium, nitrate and ammonium. Results from the field tests were compared with those obtained by traditional laboratory analysis. A linear correlation between calcium and nitrate activities measured with ISEs and relevant concentrations measured in the laboratory was found, with the slopes corresponding to apparent single ion activity coefficients and . Good correlation between pH values measured with ISE and CTD probes (SD = 0.2 pH) suggests adequate reliability of the methodology. PMID:25850652

  14. Carboxylic Acid Unknowns and Titration 90 CARBOXYLIC ACID UNKNOWN

    E-print Network

    Jasperse, Craig P.

    Carboxylic Acid Unknowns and Titration 90 CARBOXYLIC ACID UNKNOWN A. Solubility Tests: Water, Na the formula weight. #12;Carboxylic Acid Unknowns and Titration 91 Note: Do your titration once, and check

  15. Titrated energy cardioversion of patients on digitalis.

    PubMed Central

    Hagemeijer, F; Van Houwe, E

    1975-01-01

    Elective cardioversion with titrated energy was carried out under diazepam anaesthesia (38 procedures) in 26 patients on digitalis who presented with supraventricular or ventricular arrhythmias. Low energy shocks were given to establish the absence of latent digitalis intoxication, not unmasked by previous carotid sinus massage, and to restore sinus rhythm with the lowest possible energy discharge. In the absence of digitalis overdosage, titrated energy cardioversion restored sinus rhythm, at least temporarily, without dangerous ventricular arrhythmias. In one patient this precaution was neglected: a shock of 200 Ws provoked ventricular tachycardia. We present experimental and clinical evidence for the safety and effectiveness of titrated energy cardioversion in patients on digitalis. Images PMID:1225345

  16. Aqueous uranyl complexes. 3. Potentiometric measurements of the hydrolysis of uranyl(VI) ion at 25{degrees}C

    SciTech Connect

    Palmer, D.A.; Nguyen-Trung, C. [Oak Ridge National Lab., TN (United States)

    1995-12-01

    Potentiometric titrations of uranyl(VI) solutions were conducted using a standard glass/calomel electrode combination over the pH range 3 to 12 at 0.1 mol-kg{sup {minus}1} ionic strength with tetramethylammonium trifluoromethanesulfonate as the supporting electrolyte. The electrodes were calibrated directly on the hydrogen ion concentration scale during the initial stage of each titration. The species, UO{sub 2}{sup 2+}, (UO{sub 2}){sub 2}(OH){sub 2}{sup 2+}, (UO{sub 2}){sub 3}(OH){sub 5}{sup +}, (UO{sub 2}){sub 3}(OH){sub 7}{sup {minus}}, (UO{sub 2}){sub 3}(OH){sub 8}{sup 2-}, and (UO{sub 2}){sub 3}(OH){sub 10}{sup 4-} identified in an earlier Raman study were compatible with the analysis of the titration data. Based on this analysis and application of the extended Debye-Hueckel treatment, the polynuclear species indicated above were assigned overall formation constants at 25{degrees}C and at infinite dilution of -5.51{plus_minus}0.04, -15.3{plus_minus}0.1, -27.77{plus_minus}0.09, -37.65{plus_minus}0.14, and -62.4{plus_minus}0.3, respectively. The results are discussed in reference to hydrolysis quotients reported in the literature for the first three species. Formation quotients for the last two species have not been reported previously.

  17. DNA Nanostructure-Based Magnetic Beads for Potentiometric Aptasensing.

    PubMed

    Ding, Jiawang; Gu, Yue; Li, Fei; Zhang, Hongxia; Qin, Wei

    2015-07-01

    In this work, a simple, general, and sensitive potentiometric platform is presented, which allows potentiometric sensing to be applied to any class of molecule irrespective of the analyte charge. DNA nanostructures are self-assembled on magnetic beads via the incorporation of an aptamer into a hybridization chain reaction. The aptamer-target binding event leads to the disassembly of the DNA nanostructures, which results in a dramatic change in the surface charge of the magnetic beads. Such a surface charge change can be sensitively detected by a polycation-sensitive membrane electrode using protamine as an indicator. With an endocrine disruptor bisphenol A as a model, the proposed potentiometric method shows a wide linear range from 0.1 to 100 nM with a low detection limit of 80 pM (3?). The proposed sensing strategy will lay a foundation for the development of potentiometric sensors for highly sensitive and selective detection of various targets. PMID:26044085

  18. Use of Potentiometric Fluorophores in the Measurement of Mitochondrial Reactive Oxygen Species

    PubMed Central

    Polster, Brian M.; Nicholls, David G.; Ge, Shealinna X.; Roelofs, Brian A.

    2015-01-01

    Mitochondrial reactive oxygen species (ROS) are implicated in signal transduction, inflammation, neurodegenerative disorders, and normal aging. Net ROS release by isolated brain mitochondria derived from a mixture of neurons and glia is readily quantified using fluorescent dyes. Measuring intracellular ROS in intact neurons or glia and assigning the origin to mitochondria are far more difficult. In recent years, the protonmotive force crucial to mitochondrial function has been exploited to target a variety of compounds to the highly negative mitochondrial matrix using the lipophilic triphenylphosphonium cation (TPP+) as a “delivery” conjugate. Among these, MitoSOX Red, also called mito-hydroethidine or mitodihydroethidium, is prevalently used for mitochondrial ROS estimation. Although the TPP+ moiety of MitoSOX enables the many-fold accumulation of ROS-sensitive hydroethidine in the mitochondrial matrix, the membrane potential sensitivity conferred by TPP+ creates a daunting set of challenges not often considered in the application of this dye. This chapter provides recommendations and cautionary notes on the use of potentiometric fluorescent indicators for the approximation of mitochondrial ROS in live neurons, with principles that can be extrapolated to non-neuronal cell types. It is concluded that mitochondrial membrane potential changes render accurate estimation of mitochondrial ROS using MitoSOX difficult to impossible. Consequently, knowledge of mitochondrial membrane potential is essential to the application of potentiometric fluorophores for the measurement of intramitochondrial ROS. PMID:25416361

  19. Choice of ion-selective electrodes in potentiometric determination of mercaptans and hydrogen sulfide in condensates

    SciTech Connect

    Kiyanskii, V.V.; Burakhta, V.A.

    1988-05-01

    Ion-selective electrodes for the potentiometric analysis of sulfur content of high-sulfur gas condensates from fields in the Caspian lowlands and West Siberia were evaluated. The membrane electrodes are based on silver sulfide in combination with tungsten, copper, cadmium, lead, zirconium, and platinum. Tests were also conducted for titrants that form stable compounds with mercaptans as well as for solvents that would be compatible with the condensates and not stratify when the titrants were added. Anion-selective electrodes included iodine-selective, sulfide-selective, and thiocyanate-selective; cation-selective electrodes were cadmium-selective, copper-selective, and lead-selective. The preferred titrant was found to be either a solution of ammoniacal silver nitrate in isopropanol or a solution of silver nitrate in DMFA. Reduction and poisoning behavior along with service life and sensitivity were assessed. The electrodes were field tested and the procedure has been implemented at the Karachaganak field.

  20. Virtual Titrator: A Student-Oriented Instrument.

    ERIC Educational Resources Information Center

    Ritter, David; Johnson, Michael

    1997-01-01

    Describes a titrator system, constructed from a computer-interfaced pH-meter, that was designed to increase student involvement in the process. Combines automatic data collection with real-time graphical display and interactive controls to focus attention on the process rather than on bits of data. Improves understanding of concepts and…

  1. Acid Rain Analysis by Standard Addition Titration.

    ERIC Educational Resources Information Center

    Ophardt, Charles E.

    1985-01-01

    The standard addition titration is a precise and rapid method for the determination of the acidity in rain or snow samples. The method requires use of a standard buret, a pH meter, and Gran's plot to determine the equivalence point. Experimental procedures used and typical results obtained are presented. (JN)

  2. A Monte Carlo Study of Titrating Polyelectrolytes

    E-print Network

    Peterson, Carsten

    A Monte Carlo Study of Titrating Polyelectrolytes Magnus Ullner y and Bo J¨onsson z Physical, Sweden Journal of Chemical Physics 104, 3048­3057 (1996) Monte Carlo simulations have been used to study of the polymer more difficult and biases the conformations towards more extended structures. In the Monte Carlo

  3. A Monte Carlo Study of Titrating Polyelectrolytes

    E-print Network

    Peterson, Carsten

    A Monte Carlo Study of Titrating Polyelectrolytes Magnus Ullnery and Bo Jonssonz Physical Chemistry Journal of Chemical Physics 104, 3048-3057 (1996) Monte Carlo simulations have been used to study three di the conformations towards more extended structures. In the Monte Carlo simulations presented here, focus

  4. 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. PMID:12675338

  5. An Olfactory Indicator for Acid-Base Titrations.

    ERIC Educational Resources Information Center

    Flair, Mark N.; Setzer, William N.

    1990-01-01

    The use of an olfactory acid-base indicator in titrations for visually impaired students is discussed. Potential olfactory indicators include eugenol, thymol, vanillin, and thiophenol. Titrations performed with each indicator with eugenol proved to be successful. (KR)

  6. New ionophores for vitamin B1 and vitamin B6 potentiometric sensors for multivitaminic control.

    PubMed

    Pires, Ana Rita; Araújo, Alberto N; Montenegro, M Conceição B S M; Chocholous, Petr; Solich, Petr

    2008-03-13

    The construction, evaluation and analytical application of potentiometric sensors sensitive to vitamin B1 and vitamin B6 are reported. The solid contact electrodes were produced using beta-cyclodextrins as ionophores in a carboxylated poly(vinyl chloride) support matrix. Near Nernstian slopes (mV/decade) of 51.7+/-0.8, 60.6+/-0.6 and 61.1+/-1.4, within the intervals (M) of 1.0 x 10(-4) to 1.0 x 10(-1), 5.8 x 10(-5) to 1.0 x 10(-1) and 4.3 x 10(-5) to 1.0 x 10(-1) were obtained, for thiamine and pyridoxine I and II prepared membranes, respectively. A pH operational range of 6.5-8.5 for thiamine and 2-4.5 for pyridoxine electrodes was found. Assessment of selectivity coefficients toward a large number of inorganic cations and organic cations usually present in multivitamin formulations revealed good performance. Analysis of vitamins B1 and B6 in complex multivitamin drugs was achieved with recoveries within the intervals of 95.1-99.6% for thiamine and 95.1-102% for pyridoxine. Furthermore, the results enabled by the proposed procedure revealed good agreement with those provided by HPLC. PMID:18207686

  7. Potentiometric Sensors Based on Fluorous Membranes Doped with Highly Selective Ionophores for Carbonate

    PubMed Central

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

    2011-01-01

    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 CO32? that exceed those of previously reported ISEs based on non-fluorous membranes by several orders of magnitude. In particular, the interference from chloride and salicylate was reduced by two and six orders of magnitude, respectively. To achieve this, the selectivities of these ISEs were fine-tuned by addition of non-coordinating 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, (Rf6(CH2)3)3PN+P(Rf6(CH2)3)3, were utilized. The optimum CO32? 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 CO32? with stability constants up to 4.1 × 1015. 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 suggests their use not only for potentiometric sensing but also for other types of sensors, such as the selective separation of carbonate from other anions and the sequestration of carbon dioxide. PMID:22070518

  8. Integrated acquisition of analytical and biopharmaceutical screening data for beta-adrenergic-drugs employing diversified macrocycle supported potentiometric detection in HPLC systems.

    PubMed

    Bazylak, Grzegorz; Nagels, Luc J

    2002-08-01

    Potentiometric detection with poly(vinyl chloride) (PVC) based liquid membrane electrode coatings is presented for a series of eighteen beta-adrenoceptor binding drugs (five agonists and thirteen antagonists) in cation exchange-HPLC and RP-HPLC systems. Incorporation of lipophilic cation-exchanger tetrakis(p-chlorophenyl)borate (TCPB) alone or in combination with trioctylated alpha-cyclodextrin into the polymeric liquid membrane gives very sensitive responses for racemic forms of bufuralol, propranolol, carazolol, clenbuterol, mabuterol, cimaterol, bisoprolol, oxprenolol, alprenolol, tertatolol, and bevantolol, especially in the cation-exchange HPLC system applying acetonitrile -- 40 mM phosphoric acid (15: 85, v/v, pH* = 2.35) as the mobile phase. In both applied orthogonal HPLC modes we observed that use of TCPB containing electrodes (no addition of neutral macrocyclic ionophores) gives more than five fold improvement in limit of detection down to 10(-7) M for mabuterol, bufuralol, alprenolol and tertatolol in comparison with UV detection. These results suggest that potentiometric detection, especially in RP-HPLC employing hybrid polymer-silica packings, can be considered as the promising alternative in the high-throughput drug abuse or doping control procedures of investigated beta-adrenergic agonists and beta-adrenolytics in humans and animals. The quantitative structure - potentiometric response relationships were developed for a set of eighteen beta-adrenenergic drugs and a set of PVC based electrodes using TCPB alone or in admixture with trioctylated alpha-cyclodextrin, dibenzo-18-crown-6 or calix[6]arene hexaethylacetate ester. A multiple linear regression model based on computationally derived set of molecular descriptors was used to predict detection limits of beta-blocking agents and beta-adrenergic agonists from their molecular structure in the developed potentiometric detectors. Principal components analysis (PCA) of data considering determined potentiometric detection limits revealed that it can be used to establish a reliable pharmacological classification of compounds with beta-adrenoceptor activity, especially for the differentiation of cardioselective and non-cardioselective beta1-antagonists. PMID:12171563

  9. Determination of carbonate carbon in geological materials by coulometric titration

    USGS Publications Warehouse

    Engleman, E.E.; Jackson, L.L.; Norton, D.R.

    1985-01-01

    A coulometric titration is used for the determination of carbonate carbon in geological materials. Carbon dioxide is evolved from the sample by the addition of 2 M perchloric acid, with heating, and is determined by automated coulometric titration. The coulometric titration showed improved speed and precision with comparable accuracy to gravimetric and gasometric techniques. ?? 1985.

  10. 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. PMID:26002212

  11. Association quotients of aluminum sulphate complexes in NaCl media from 50 to 125 C: Results of a potentiometric and solubility study

    SciTech Connect

    Ridley, M.K.; Kettler, R.M. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Geology] [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Geology; Wesolowski, D.J.; Palmer, D.A. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.] [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.

    1999-02-01

    The speciation and molal formation quotients for the complexation of aluminum with sulphate were measured based on potentiometric and solubility experiments. Potentiometric titrations, utilizing a hydrogen-electrode concentration cell, were performed from 50 to 125 C at ionic strengths of 0.1, 0.3 and 1.0 molal in aqueous NaCl media. Two aluminum-sulphate species, AlSO{sub 4}{sup +} and Al(SO{sub 4}){sub 2}{sup {minus}}, were identified from the titration data and the formation quotients for these species were modeled by empirical equations to describe their temperature and ionic strength dependencies. Thermodynamic parameters for the complexation reactions were obtained by differentiating the empirical equations with respect to temperature. The thermodynamic quantities obtained for the formation of AlSO{sub 4}{sup +} at 50 C and infinite dilution are: logK{sub 1} = 3.7 {+-} 0.4, {Delta}H{sub 1}{degree} = {minus}10 {+-} 30 kJ/mol, {Delta}S{sub 1}{degree} = 40 {+-} 100 J/K{center_dot}mol and {Delta}C{sub p 1}{degree} = 1900 {+-} 800 J/K{center_dot}mol; whereas the values for Al(SO{sub 4}){sub 2}{sup {minus}} are: logK{sub 2} = 5.6 {+-} 0.7, {Delta}H{sub 2}{degree} = 10 {+-} 50 kJ/mol, {Delta}S{sub 2}{degree} = 100 {+-} 100 J/K{center_dot}mol and {Delta}C{sub p 2}{degree} = 2800 {+-} 800 J/K{center_dot}mol. A solubility study, which was undertaken to verify the 50 C potentiometric data, was performed by reacting powdered gibbsite (Al(OH){sub 3}) with sulphate solutions at 10{sup {minus}3.5} and 10{sup {minus}4} molal H{sup +}, total sulphate concentrations from 0.005 to 0.080 molal, and 0.1 and 1.0 molal ionic strength in aqueous NaCl media. The results of the solubility study are in good agreement with the potentiometric data and establish that Al-sulphate complexation substantially enhances the equilibrium solubility of gibbsite.

  12. Environ. Sci. Technol. 1993, 27, 1625-1631 Sorptlon and Desorption of Quaternary Amine Cations on Clays

    E-print Network

    Sparks, Donald L.

    Environ. Sci. Technol. 1993, 27, 1625-1631 Sorptlon and Desorption of Quaternary Amine Cations 19714 We have studied the sorption and desorption of three quaternary amines, namely-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were

  13. Alternative sensor materials for light-addressable potentiometric sensors

    Microsoft Academic Search

    T Yoshinobu; H Ecken; A Poghossian; H Lüth; H Iwasaki; M. J Schöning

    2001-01-01

    Ta2O5 and porous Si were investigated as alternative sensor materials for the light-addressable potentiometric sensor (LAPS). The Ta2O5 LAPS, prepared by the pulsed laser deposition (PLD) technique, showed a high pH sensitivity of 57.5mV\\/pH and a good linearity. Porous Si was prepared by anodic etching of Si in a mixture of HF and ethanol. The porous Si LAPS with a

  14. Portable light-addressable potentiometric sensor (LAPS) for multisensor applications

    Microsoft Academic Search

    T. Yoshinobu; M. J. Schöning; R. Otto; K. Furuichi; Yu. Mourzina; Yu. Ermolenko; H. Iwasaki

    2003-01-01

    A novel design of the light-addressable potentiometric sensor (LAPS) for realisation of a portable multisensor device is presented. Light sources and electronics including an oscillator, a multiplexer, a pre-amplifier and a high-pass filter are encapsulated in a pen-shaped case, on which the sensor plate is mounted. This sensor device is capable of measuring up to four different ion species by

  15. 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.

  16. Potentiometric studies on bismuth ferrocyanide and the determination of bismuth

    Microsoft Academic Search

    Ram Sahai Saxena; C. S. Bhatnagar

    1959-01-01

    The reaction between bismuth nitrate and ferrocyanides of alkali metals such as sodium, potassium, lithium and ammonium, has been studied potentiometrically using platinum as an indicator electrode in conjunction with a saturated calomel electrode through KNO3 bridge. The equivalence point obtained from the maximum value of dE\\/dV corresponds to the formation and complete precipitation of a compound having molecular formula

  17. Titration of chaos with added noise.

    PubMed

    Poon, C S; Barahona, M

    2001-06-19

    Deterministic chaos has been implicated in numerous natural and man-made complex phenomena ranging from quantum to astronomical scales and in disciplines as diverse as meteorology, physiology, ecology, and economics. However, the lack of a definitive test of chaos vs. random noise in experimental time series has led to considerable controversy in many fields. Here we propose a numerical titration procedure as a simple "litmus test" for highly sensitive, specific, and robust detection of chaos in short noisy data without the need for intensive surrogate data testing. We show that the controlled addition of white or colored noise to a signal with a preexisting noise floor results in a titration index that: (i) faithfully tracks the onset of deterministic chaos in all standard bifurcation routes to chaos; and (ii) gives a relative measure of chaos intensity. Such reliable detection and quantification of chaos under severe conditions of relatively low signal-to-noise ratio is of great interest, as it may open potential practical ways of identifying, forecasting, and controlling complex behaviors in a wide variety of physical, biomedical, and socioeconomic systems. PMID:11416195

  18. Soil water content by Karl Fischer titration

    SciTech Connect

    Prunty, L.; Zellis, M.K.; Bell, J.S. [North Dakota State Univ., Fargo, ND (United States). Dept. of Soil Science

    1997-12-31

    Specific analytical determination of water content is often desirable in contaminated soils. Karl Fischer (KF) titration is useful for this purpose, since it consumes only H{sub 2}O, even in the presence of other volatile substances. Although widely used for water content determination in industrial and food products, KF has been virtually ignored in soil and environmental science. Oven drying (OD), conversely, is considered the standard method of soil water determination, but is an indiscriminate determiner of all volatiles. The authors examined KF titration for soil water content determination. Two soil types were mixed with varying amounts of water and octane or toluene. The prepared samples containing water only, water and octane, and water and toluene were analyzed for volatile/moisture content using OD/KF analysis. Soil moisture values determined by the calibrated KF method (w{sub c}) compared favorably to those determined by OD (w{sub 0}) in terms of regression slope, intercept, correlation coefficient, and Student`s t. Regression slopes ranged from 0.980 to 1.009 while intercepts ranged from {minus}0.6 to 7.8 g kg{sup {minus}1}. Plots of the data show essentially a 1:1 correspondence of w{sub c} to w{sub o}.

  19. Ion-exchange and potentiometric characterization of Al-cystine and Al-cysteine complexes.

    PubMed

    Bohrer, Denise; Polli, Vania Gabbi; Cícero do Nascimento, Paulo; Mendonça, Jean Karlo A; de Carvalho, Leandro Machado; Pomblum, Solange Garcia

    2006-11-01

    The interaction between aluminium and cysteine and cystine was evaluated by means of ion-exchange experiments and potentiometry. Ion-exchange experiments included other ligands with affinity for aluminium and two kinds of resins, either a Na+ -form or an Al3+ -form exchanger. The ability of the ligands to keep aluminium in solution in the presence of the Na+ exchanger or to withdraw it from the Al3+ -form resin was evaluated. Aluminium quantification was carried out by either graphite-furnace or flame atomic absorption spectrometry. Aluminium extraction isotherms were linearised using the Scatchard plot, and stability constants were obtained from the curves' slopes. The experiments showed that the ability of the ligands to withdraw aluminium from the Al3+ -form resin increased following the order cysteine < oxalate < citrate = cystine < nitrilotriacetic acid < ethylenediaminetetraacetic acid. Potentiometric titrations, carried out in aqueous solution with constant ionic strength and temperature, showed that the predominant species in solution have a metal-ligand proportion of 1:1 for both amino acids. The main species are Al(OH)3L, with log K of 6.2 for cysteine, and AlL and Al(OH)L, with log K of 10.3 and 1.7, respectively, for cystine. Stability constants obtained from the Scatchard plots showed a linear correlation with the stability constants obtained by potentiometry for cystine and cysteine in this work and those collected from the literature for the other ligands. These results show that cysteine and cystine extract and maintain aluminium in solution, which may explain elevated concentrations of aluminium in parenteral nutrition solutions containing these amino acids. PMID:16932929

  20. Automated titration method for use on blended asphalts

    DOEpatents

    Pauli, Adam T. (Cheyenne, WY); Robertson, Raymond E. (Laramie, WY); Branthaver, Jan F. (Chatham, IL); Schabron, John F. (Laramie, WY)

    2012-08-07

    A system for determining parameters and compatibility of a substance such as an asphalt or other petroleum substance uses titration to highly accurately determine one or more flocculation occurrences and is especially applicable to the determination or use of Heithaus parameters and optimal mixing of various asphalt stocks. In a preferred embodiment, automated titration in an oxygen gas exclusive system and further using spectrophotometric analysis (2-8) of solution turbidity is presented. A reversible titration technique enabling in-situ titration measurement of various solution concentrations is also presented.

  1. A potentiometric study of the hydrolysis of ethylenediaminetetraacetic acid to 150{degrees}C

    SciTech Connect

    Palmer, D.A. [Oak Ridge National Lab., TN (United States); Nguyen-Trung, Chinh [CREGU, Vandoeuvre les Nancy (France)

    1995-02-01

    Ethylenediaminetetraacetate anions, EDTA{sup 4-}, were titrated in a hydrogen-electrode concentration cell with an acidic titrant from 0 to 150{degrees}C at 25{degrees}C intervals. These titrations were carried out in the presence of 0. 1, 0.2, and 1.0 mol{center_dot}kg{sup -1} with the supporting electrolytes, sodium chloride, NaCl, and 1.0 mol{center_dot}kg{sup -1} tetramethylammonium trifluoromethylsulfonate, (CH{sub 3}){sub 4}N(F{sub 3}CSO{sub 3}) {l_brace}TMATFMS{r_brace} in order to assess the effect of both cation complexation by EDTA{sup 4-} and anion activity coefficient variations. The resulting hydrolysis quotients are discussed with reference to applications in boiler and heat exchanger chemical cleaning, as well as chemical and nuclear waste containment. Some recent diverse uses of this emf technique that also pertain to these applications will be mentioned briefly, e.g., surface absorption - zero-point-of-charge - measurements to high temperatures and in situ pH measurements in solubility and kinetic experiments.

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

    PubMed

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

    2011-09-15

    Solid-contact sensors for the selective screening of sulfadiazine (SDZ) in aquaculture waters are reported. Sensor surfaces were made from PVC membranes doped with tetraphenylporphyrin-manganese(III) chloride, ?-cyclodextrin, ?-cyclodextrin, or ?-cyclodextrin ionophores that were dispersed in plasticizer. Some membranes also presented a positive or a negatively charged additive. Phorphyrin-based sensors relied on a charged carrier mechanism. They exhibited a near-Nernstian response with slopes of 52 mV decade(-1) and detection limits of 3.91×10(-5) mol L(-1). The addition of cationic lipophilic compounds to the membrane originated Nernstian behaviours, with slopes ranging 59.7-62.0 mV decade(-1) and wider linear ranges. Cyclodextrin-based sensors acted as neutral carriers. In general, sensors with positively charged additives showed an improved potentiometric performance when compared to those without additive. Some SDZ selective membranes displayed higher slopes and extended linear concentration ranges with an increasing amount of additive (always <100% ionophore). The sensors were independent from the pH of test solutions within 2-7. The sensors displayed fast response, always <15s. In general, a good discriminating ability was found in real sample environment. The sensors were successfully applied to the fast screening of SDZ in real waters samples from aquaculture fish farms. The method offered the advantages of simplicity, accuracy, and automation feasibility. The sensing membrane may contribute to the development of small devices allowing in locus measurements of sulfadiazine or parent-drugs. PMID:21807216

  3. Performance Evaluation of a Novel Potentiometric Membrane Sensor for Determination of Atorvastatin in Pharmaceutical Preparations

    PubMed Central

    Ahmadi, Farhad; Asaadi, Nasim

    2013-01-01

    A novel potentiometric ion-selective PVC membrane sensor for analysis of atorvastatin (AT) in pharmaceutical preparations based on atorvastatin-(tetraphenyl borate), (AT-(TPB)2) as sensing element, tetraphenyl borate as additive and tris-2-ethyl-hexyl phosphate (TOP) as plasticizer solvent was prepared. The electrode shows a good Nernestian response over the concentration range of 0.09–5586 ?g mL-1of AT with slope of 30.1±0.1 mV/decade and limit of detection0.056?g mL-1.The response time of sensor is fats (less than 10 sec) and could be used for about one month in the pH range of 4.5–8.0. The electrode exhibit good selectivity for the AT in the presence of large amount of co-drugs and inorganic cations. The method is precise and accurate with mean relative standard deviation of <2%.Atorvastatin is determined successfully in several tablets by the proposed membrane. PMID:24523744

  4. Manganese(III) Porphyrin-based Potentiometric Sensors for Diclofenac Assay in Pharmaceutical Preparations

    PubMed Central

    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. PMID:22163384

  5. The acid-base titration of montmorillonite

    NASA Astrophysics Data System (ADS)

    Bourg, I. C.; Sposito, G.; Bourg, A. C.

    2003-12-01

    Proton binding to clay minerals plays an important role in the chemical reactivity of soils (e.g., acidification, retention of nutrients or pollutants). If should also affect the performance of clay barriers for waste disposal. The surface acidity of clay minerals is commonly modelled empirically by assuming generic amphoteric surface sites (>SOH) on a flat surface, with fitted site densities and acidity constant. Current advances in experimental methods (notably spectroscopy) are rapidly improving our understanding of the structure and reactivity of the surface of clay minerals (arrangement of the particles, nature of the reactive surface sites, adsorption mechanisms). These developments are motivated by the difficulty of modelling the surface chemistry of mineral surfaces at the macro-scale (e.g., adsorption or titration) without a detailed (molecular-scale) picture of the mechanisms, and should be progressively incorporated into surface complexation models. In this view, we have combined recent estimates of montmorillonite surface properties (surface site density and structure, edge surface area, surface electrostatic potential) with surface site acidities obtained from the titration of alpha-Al2O3 and SiO2, and a novel method of accounting for the unknown initial net proton surface charge of the solid. The model predictions were compared to experimental titrations of SWy-1 montmorillonite and purified MX-80 bentonite in 0.1-0.5 mol/L NaClO4 and 0.005-0.5 mol/L NaNO3 background electrolytes, respectively. Most of the experimental data were appropriately described by the model after we adjusted a single parameter (silanol sites on the surface of montmorillonite were made to be slightly more acidic than those of silica). At low ionic strength and acidic pH the model underestimated the buffering capacity of the montmorillonite, perhaps due to clay swelling or to the interlayer adsorption of dissolved aluminum. The agreement between our model and the experimental data illustrates the complementarity of molecular and macro-scale descriptions of the clay reactivity.

  6. Cetylpyridinium tetrachlorozincate as standard for tenside titration. Analytical methods with 1,3-dibromo-5,5-dimethylhydantoin (DBH) in respect to environmental and economical concern, part 19.

    PubMed

    Hilp, M; Zembatova, S

    2004-08-01

    The determination of the cationic active disinfectants benzalkonium chloride, benzethonium chloride, cetrimide, and cetylpyridinium chloride according to PH. EUR. 2002 resp. supplement 4.3/2003 can be improved using the DBH-method. By application of column extraction the iodide determination can be performed in the organic layer by visual indication. However, titration in aqueous solution with sodium dodecyl sulphate as titrant and methyl orange resp. bromophenol blue as indicator can be performed more simple. Cetylpyridinium tetrachlorozincate is recommended as a standard for tenside titration. PMID:15378850

  7. Isothermal titration calorimetry in drug discovery.

    PubMed

    Ward, W H; Holdgate, G A

    2001-01-01

    Isothermal titration calorimetry (ITC) follows the heat change when a test compound binds to a target protein. It allows precise measurement of affinity. The method is direct, making interpretation facile, because there is no requirement for competing molecules. Titration in the presence of other ligands rapidly provides information on the mechanism of action of the test compound, identifying the intermolecular complexes that are relevant for structure-based design. Calorimetry allows measurement of stoichiometry and so evaluation of the proportion of the sample that is functional. ITC can characterize protein fragments and catalytically inactive mutant enzymes. It is the only technique which directly measures the enthalpy of binding (delta H degree). Interpretation of delta H degree and its temperature dependence (delta Cp) is usually qualitative, not quantitative. This is because of complicated contributions from linked equilibria and a single change in structure giving modification of several physicochemical properties. Measured delta H degree values allow characterization of proton movement linked to the association of protein and ligand, giving information on the ionization of groups involved in binding. Biochemical systems characteristically exhibit enthalpy-entropy compensation where increased bonding is offset by an entropic penalty, reducing the magnitude of change in affinity. This also causes a lack of correlation between the free energy of binding (delta G degree) and delta H degree. When characterizing structure-activity relationships (SAR), most groups involved in binding can be detected as contributing to delta H degree, but not to affinity. Large enthalpy changes may reflect a modified binding mode, or protein conformation changes. Thus, delta H degree values may highlight a potential discontinuity in SAR, so that experimental structural data are likely to be particularly valuable in molecular design. PMID:11774798

  8. Microscale pH Titrations Using an Automatic Pipet.

    ERIC Educational Resources Information Center

    Flint, Edward B.; Kortz, Carrie L.; Taylor, Max A.

    2002-01-01

    Presents a microscale pH titration technique that utilizes an automatic pipet. A small aliquot (1-5 mL) of the analyte solution is titrated with repeated additions of titrant, and the pH is determined after each delivery. The equivalence point is determined graphically by either the second derivative method or a Gran plot. The pipet can be…

  9. Spectrophotometric Titration of a Mixture of Calcium and Magnesium.

    ERIC Educational Resources Information Center

    Fulton, Robert; And Others

    1986-01-01

    Describes a spectrophotometric titration experiment which uses a manual titration spectrophotometer and manually operated buret, rather than special instrumentation. Identifies the equipment, materials, and procedures needed for the completion of the experiment. Recommends the use of this experiment in introductory quantitative analysis…

  10. Students' integration of multiple representations in a titration experiment

    NASA Astrophysics Data System (ADS)

    Kunze, Nicole M.

    A complete understanding of a chemical concept is dependent upon a student's ability to understand the microscopic or particulate nature of the phenomenon and integrate the microscopic, symbolic, and macroscopic representations of the phenomenon. Acid-base chemistry is a general chemistry topic requiring students to understand the topics of chemical reactions, solutions, and equilibrium presented earlier in the course. In this study, twenty-five student volunteers from a second semester general chemistry course completed two interviews. The first interview was completed prior to any classroom instruction on acids and bases. The second interview took place after classroom instruction, a prelab activity consisting of a titration calculation worksheet, a titration computer simulation, or a microscopic level animation of a titration, and two microcomputer-based laboratory (MBL) titration experiments. During the interviews, participants were asked to define and describe acid-base concepts and in the second interview they also drew the microscopic representations of four stages in an acid-base titration. An analysis of the data showed that participants had integrated the three representations of an acid-base titration to varying degrees. While some participants showed complete understanding of acids, bases, titrations, and solution chemistry, other participants showed several alternative conceptions concerning strong acid and base dissociation, the formation of titration products, and the dissociation of soluble salts. Before instruction, participants' definitions of acid, base, and pH were brief and consisted of descriptive terms. After instruction, the definitions were more scientific and reflected the definitions presented during classroom instruction.

  11. Characterization of Petroleum Sulfonates by a Nonaqueous Titration Method

    Microsoft Academic Search

    Kim Voss; Clark Bricker; M. J. Michnick; G. P. Willhite

    1981-01-01

    A new method is described for the determination of the equivalent weight for petroleum sulfonates. The method is based on the direct acidimetric titration of the sulfonate in acetic acid\\/acetic anhydride solvent using a titrant of perchloric acid in dioxane. From the titration, the moles of perchloric acid required to react with the sulfonate is measured. The equivalent weight is

  12. Ionization properties of titratable groups in ribonuclease T 1

    Microsoft Academic Search

    Assen Koumanov; Normann Spitzner; Heinz Rüterjans; Andrey Karshikoff

    2001-01-01

    The experimental NMR data for the individual titratable groups in ribonuclease T1 presented in the preceding paper were analysed by means of a continuum dielectric model. The role of two factors, the alteration of hydrogen loci on the ionizable groups and the conformational flexibility, were analysed. It was suggested that the position of the titratable hydrogen is essential mainly for

  13. Determination of the Capacitance of Solid-State Potentiometric Sensors: An Electrochemical

    E-print Network

    Majda, Marcin

    be performance-limiting.16-18 When dealing with characterization of potentiometric sensors, the effectDetermination of the Capacitance of Solid-State Potentiometric Sensors: An Electrochemical Time the generator current, or the initial concentration of the primary ion of interest is low, appreciable delays

  14. 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.

  15. Preliminary map showing the potentiometric surface of the Aquia Aquifer in southern Maryland, September 1984

    USGS Publications Warehouse

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

    1985-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Aquia aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  16. The Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 1985

    USGS Publications Warehouse

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

    1987-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Aquia aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  17. The potentiometric surface of the Magothy Aquifer in southern Maryland, September 1985

    USGS Publications Warehouse

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

    1987-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Magothy aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  18. Potentiometric surface of the Aquia Aquifer in southern Maryland during the Fall of 1986

    USGS Publications Warehouse

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

    1987-01-01

    Thr potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Aquia aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  19. The potentiometric surface of the Magothy Aquifer in southern Maryland, September 1984

    USGS Publications Warehouse

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

    1985-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Magothy aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  20. Potentiometric surface of the Magothy Aquifer in southern Maryland during the Fall of 1986

    USGS Publications Warehouse

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

    1987-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Magothy aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  1. Potentiometric surface of Floridan aquifer May 1975, and change of potentiometric surface 1969 to 1975, Southwest Florida Water Management District and adjacent areas

    USGS Publications Warehouse

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

    1976-01-01

    Maps showing the potentiometric surface of the Floridan aquifer for May 1975, and changes of potentiometric surface from 1964 to 1975 were prepared for areas in southwest Florida. Contours and color codes describe water-level changes. The larger map, scale 1:500,000, reflects the water-level changes from 1969-75. The smaller map shows the changes from January 1964 to May 1969. (Woodard-USGS)

  2. Magnetic Nanoparticles Produced in Spontaneous Cationic-Anionic Vesicles: Room Temperature Synthesis and Characterization

    Microsoft Academic Search

    Iskandar I. Yaacob; Anthony C. Nunes; Arijit Bose

    1995-01-01

    Unilamellar vesicles formed spontaneously by forming solutions of single-tailed cationic and anionic surfactants [cetyltrimethylammonium bromide (CTAB) and dodecylbenzenesulfonic acid (HDBS), respectively] have been used as reactors for the direct, room temperature synthesis of nanometer-sized magnetic particles within their internal cores. A micellar anionic surfactant solution was titrated slowly into a micellar cationic surfactant solution containing ferrous chloride, forming defect-free unilamellar

  3. A surface complex reaction model for the pH-dependence of corundum and kaolinite dissolution rates

    Microsoft Academic Search

    Susan A. Carroll-Webb; John V. Walther

    1988-01-01

    Comparison of experimental and theoretical potentiometric titrations of kaolinite at 25°C indicates that the adsorption of H + and OH - ions to the mineral surface are metal cation specific and that the net adsorption can be modeled in terms of the constituent oxide components. We conclude, from the potentiometric, electrophoretic, and dissolution rate data presented in this paper, that

  4. Automatic photometric titrations of calcium and magnesium in carbonate rocks

    USGS Publications Warehouse

    Shapiro, L.; Brannock, W.W.

    1955-01-01

    Rapid nonsubjective methods have been developed for the determination of calcium and magnesium in carbonate rocks. From a single solution of the sample, calcium is titrated directly, and magnesium is titrated after a rapid removal of R2O3 and precipitation of calcium as the tungstate. A concentrated and a dilute solution of disodium ethylenediamine tetraacetate are used as titrants. The concentrated solution is added almost to the end point, then the weak solution is added in an automatic titrator to determine the end point precisely.

  5. Aqueous complexation of trivalent lanthanide and actinide cations by N,N,N'{sub 2},N'-tetrakis(2-pyridylmethyl)ethylenediamine.

    SciTech Connect

    Beitz, J. V.; Ensor, D. D.; Jensen, M. P.; Morss, L. R.

    1999-06-16

    The aqueous complexation reactions of trivalent lanthanide and actinide cations with the hexadentate ligand N,N,N{prime},N{prime}-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), have been characterized using potentiometric and spectroscopic techniques in 0.1 M NaClO{sub 4} At 25 C, the stability constant of Am(TPEN){sup 3+} is two orders of magnitude larger than that of Sm(TPEN){sup 3+}, reflecting the stronger interactions of the trivalent actinide cations with softer ligands as compared to lanthanide cations.

  6. Titration Microcalorimetry Study: Interaction of Drug and Ionic Microgel System

    E-print Network

    Tian, Y.

    Doxorubicin (DOX) and Pluronic-PAA interaction was investigated using isothermal titration calorimetry (ITC). DOX/polymer interaction is governed primarily by electrostatic interaction. The uptake of DOX results in the ...

  7. Microscope Titration and Extraction of DNA from Liver.

    ERIC Educational Resources Information Center

    Mayo, Lois T.; And Others

    1993-01-01

    Describes a simple and inexpensive, one-period activity to extract DNA to make the study of DNA less abstract. A microscope titration is used to determine when cells are ready for DNA extraction. (PR)

  8. 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)

  9. 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.

  10. Potentiometric surface of the Aquia 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 Aquia aquifer in the Paleocene Aquia Formation in southern Maryland during the fall of 1987 was prepared by using water level measurements from 80 observation wells. The potentiometric surface was above sea level near the northeastern boundary and outcrop area of the aquifer in topographically high areas of Anne Arundel and Prince Georges Counties. The potentiometric surface was below sea level in the remainder of the study area. The hydraulic gradient was generally to the southeast toward an extensive cone of depression, which is centered around well fields near Lexington Park. Much of the cone is more than 40 ft below sea level. (USGS)

  11. 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. PMID:25857888

  12. Potentiometric sensors with carbon black supporting platinum nanoparticles.

    PubMed

    Paczosa-Bator, Beata; Cabaj, Leszek; Piech, Robert; Skupie?, Krzysztof

    2013-11-01

    For the first time, a single-piece, all-solid-state ion-selective electrode was fabricated with carbon black supporting platinum nanoparticles (PtNPs-CB) and a polymeric membrane. The PtNPs-CB, as an intermediate layer, was drop-casted directly on the solid substrate, and then an ionophore-doped solvent polymeric membrane was added in order to form a sensor. The performance of the newly developed electrodes was evaluated on the basis of potassium and nitrate ions. The stability of the electrical potential for the electrodes was examined by performing current-reversal chronopotentiometry, and the influence of the interfacial water film was assessed by the potentiometric aqueous-layer test. Fabricated potassium- and nitrate-selective electrodes displayed a Nernstian slope and several outstanding properties such as high long-term potential stability, potential repeatability, and reproducibility. PMID:24094044

  13. CO2 Selective Potentiometric Sensor in Thick-film Technology

    PubMed Central

    Sahner, Kathy; Schulz, Anne; Kita, Jaroslaw; Merkle, Rotraut; Maier, Joachim; Moos, Ralf

    2008-01-01

    A potentiometric sensor device based on screen-printed Nasicon films was investigated. In order to transfer the promising sensor concept of an open sodium titanate reference to thick film technology, “sodium-rich” and “sodium-poor” formulations were compared. While the “sodium-rich” composition was found to react with the ion conducting Nasicon during thermal treatment, the “sodium-poor” reference mixture was identified as an appropriate reference composition. Screen-printed sensor devices were prepared and tested with respect to CO2 response, reproducibility, and cross-interference of oxygen. Excellent agreement with the theory was observed. With the integration of a screen-printed heater, sensor elements were operated actively heated in a cold gas stream.

  14. 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.

  15. 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 ?M for penicillin and achieved a minimum detectable concentration of 0.3 ?M. The biosensor was successfully utilized for the detection of Amoxycillin and gave an average percentage recovery of 102±6%. Satisfactory recoveries of penicillin G were also achieved in milk samples with the potentiometric biosensor when concentrations are ?20 ppm. PMID:22319276

  16. Instrument-free control of the standard potential of potentiometric solid-contact ion-selective electrodes by short-circuiting with a conventional reference electrode.

    PubMed

    Vanamo, Ulriika; Bobacka, Johan

    2014-11-01

    A simple, instrument-free method to control the standard potential (E°) of potentiometric solid-contact ion-selective electrodes (SC-ISE) is described. In this method, the electrode potential of a SC-ISE is reset by short-circuiting the electrode with a metallic wire to a conventional Ag/AgCl/3 M KCl reference electrode (RE) in a solution containing primary ions. The method is studied experimentally for SC-ISEs where the conducting polymer poly(3,4-ethylenedioxythiophene) doped with the bulky anion poly(sodium 4-styrenesulfonate), PEDOT(PSS), is used as the solid contact. Three different types of ion-selective membranes (ISMs) are studied: two potassium-selective membranes, with and without the lipohilic additive tetradodecylammonium tetrakis(4-chlorophenyl)borate (ETH-500) and a cation-sensitive membrane without an ionophore. When the SC-ISE is short-circuited with the RE, the PEDOT(PSS) layer is oxidized or reduced, thereby shifting the potential of the SC-ISE to the proximity of the potential of the RE so that the potential difference between these two electrodes becomes zero or close to zero. The slope of the calibration curve is preserved after the short-circuit treatment of the SC-ISEs. The short-circuiting method is an important step toward calibration-free potentiometric analysis. PMID:25284311

  17. Intrinsic thermodynamics of 4-substituted-2,3,5,6-tetrafluorobenzenesulfonamide binding to carbonic anhydrases by isothermal titration calorimetry.

    PubMed

    Zubrien?, Asta; Smirnovien?, Joana; Smirnov, Alexey; Mork?nait?, Vaida; Michailovien?, Vilma; Jachno, Jelena; Juozapaitien?, Vaida; Norvaišas, Povilas; Manakova, Elena; Gražulis, Saulius; Matulis, Daumantas

    2015-10-01

    Para substituted tetrafluorobenzenesulfonamides bind to carbonic anhydrases (CAs) extremely tightly and exhibit some of the strongest known protein-small ligand interactions, reaching an intrinsic affinity of 2 pM as determined by displacement isothermal titration calorimetry (ITC). The enthalpy and entropy of binding to five CA isoforms were measured by ITC in two buffers of different protonation enthalpies. The pKa values of compound sulfonamide groups were measured potentiometrically and spectrophotometrically, and enthalpies of protonation were measured by ITC in order to evaluate the proton linkage contributions to the observed binding thermodynamics. Intrinsic means the affinity of a sulfonamide anion for the Zn bound water form of CAs. Fluorination of the benzene ring significantly enhanced the observed affinities as it increased the fraction of deprotonated ligand while having little impact on intrinsic affinities. Intrinsic enthalpy contributions to the binding affinity were dominant over entropy and were more exothermic for CA I than for other CA isoforms. Thermodynamic measurements together with the X-ray crystallographic structures of protein-ligand complexes enabled analysis of structure-activity relationships in this enzyme ligand system. PMID:26079542

  18. The Cation-? Interaction

    PubMed Central

    DOUGHERTY, DENNIS A.

    2014-01-01

    CONSPECTUS The chemistry community now recognizes the cation-? interaction as a major force for molecular recognition, joining the hydrophobic effect, the hydrogen bond, and the ion pair in determining macromolecular structure and drug-receptor interactions. This Account provides the author’s perspective on the intellectual origins and fundamental nature of the cation-? interaction. Early studies on cyclophanes established that water-soluble, cationic molecules would forgo aqueous solvation to enter a hydrophobic cavity if that cavity was lined with ? systems. Important gas phase studies established the fundamental nature of the cation-? interaction. The strength of the cation-? interaction – Li+ binds to benzene with 38 kcal/mol of binding energy; NH4+ with 19 kcal/mol– distinguishes it from the weaker polar-? interactions observed in the benzene dimer or water-benzene complexes. In addition to the substantial intrinsic strength of the cation-? interaction in gas phase studies, the cation-? interaction remains energetically significant in aqueous media and under biological conditions. Many studies have shown that cation-? interactions can enhance binding energies by 2 – 5 kcal/mol, making them competitive with hydrogen bonds and ion pairs in drug-receptor and protein-protein interactions. As with other noncovalent interactions involving aromatic systems, the cation-? interaction includes a substantial electrostatic component. The six (four) C??–H?+ bond dipoles of a molecule like benzene (ethylene) combine to produce a region of negative electrostatic potential on the face of the ? system. Simple electrostatics facilitate a natural attraction of cations to the surface. The trend for (gas phase) binding energies is Li+>Na+>K+>Rb+: as the ion gets larger the charge is dispersed over a larger sphere and binding interactions weaken, a classical electrostatic effect. On other hand, polarizability does not define these interactions. Cyclohexane is more polarizable than benzene, but a decidedly poorer cation binder. Many studies have documented cation-? interactions in protein structures, where Lys or Arg side chains interact with Phe, Tyr, or Trp. In addition, countless studies have established the importance of cation-? interaction in a range of biological processes. Our work has focused on molecular neurobiology, and we have shown that neurotransmitters generally use a cation-? interaction to bind to their receptors. We have also shown that many drug-receptor interactions involve cation-? interactions. A cation-? interaction plays a critical role in the binding of nicotine to ACh receptors in the brain, an especially significant case. Other researchers have established important cation-? interactions in the recognition of the “histone code,” in terpene biosynthesis, in chemical catalysis, and in many other systems. PMID:23214924

  19. Geochemical modeling of reactions and partitioning of trace metals and radionuclides during titration of contaminated acidic sediments

    SciTech Connect

    Zhang, Fan [ORNL; Parker, Jack C. [University of Tennessee, Knoxville (UTK); Brooks, Scott C [ORNL; Watson, David B [ORNL; Jardine, Philip M [ORNL; Gu, Baohua [ORNL

    2008-01-01

    This study investigated sorption of uranium and technetium onto aluminum and iron hydroxides during titration of a contaminated groundwater using both Na hydroxide and carbonate as titrants. The contaminated groundwater has a low pH of 3.8 and high concentrations of NO3-, SO42-, Al, Ca, Mg, Mn, trace metals such as Ni and Co, and radionuclides such as U and Tc. During titration, most Al and Fe were precipitated out at pH above ~4.5. U as well as Tc was found to be removed from aqueous phase at pH below ~5.5, but to some extent released at higher pH values. An earlier geochemical equilibrium reaction path model that considered aqueous complexation and precipitation/dissolution reactions predicted mineral precipitation and adequately described concentration variations of Al, Fe and some other metal cations, but failed to predict sulfate, U and Tc concentrations during titration. Previous studies have shown that Fe- and Al-oxyhydroxides strongly sorb dissolved sulfate, U and Tc species. Therefore, an anion exchange model was developed for the sorption of sulfate, U and Tc onto Al and Fe hydroxides. With the additional consideration of the anion exchange reactions, concentration profiles of sulfate, U and Tc were more accurately predicted. Results of this study indicate that consideration of complex reactions such as sorption/desorption on mixed mineral phases, in addition to hydrolysis and precipitation, could improve the prediction of various contaminants during pre- and post-groundwater treatment practices.

  20. Cation-alkane interaction.

    PubMed

    Premkumar, J Richard; Sastry, G Narahari

    2014-12-01

    Ab initio computations, up to CCSD(T)/CBS on model systems, and MP2/cc-pVTZ and DFT calculations are performed on cation-alkane and cation-alkene complexes, cation = Li(+), Na(+), Be(2+), Mg(2+), Ca(2+), Cu(+) and Zn(2+); alkane = C(n)H2(n+2) (n = 1-10) and C6H12; and alkene = C2H4 and C6H6. Density functional theory-symmetry adapted perturbation theory (DFT-SAPT) calculations reveal that the cation-alkane interactions are predominantly constituted of induction component. The dramatic modulation of the strength of their interaction and the topological features obtained from atoms in molecules (AIM) analysis are consistent with the characteristics of a typical noncovalent interaction. In contrast to many of the conventional noncovalent interactions, cation-alkane interactions are substantially strong and are comparable in strength to the well studied cation-? interactions. PMID:25384257

  1. Prediction of uranium and technetium sorption during titration of contaminated acidic groundwater

    SciTech Connect

    Zhang, Fan [ORNL; Parker, Jack C. [University of Tennessee, Knoxville (UTK); Watson, David B [ORNL; Jardine, Philip M [ORNL; Gu, Baohua [ORNL

    2010-01-01

    This study investigates uranium and technetium sorption onto aluminum and iron hydroxides during titration of acidic groundwater. The contaminated groundwater exhibits oxic conditions with high concentrations of NO{sub 3}{sup -}, SO{sub 4}{sup 2-}, U, Tc, and various metal cations. More than 90% of U and Tc was removed from the aqueous phase as Al and Fe precipitated above pH 5.5, but was partially resolublized at higher pH values. An equilibrium hydrolysis and precipitation reaction model adequately described variations in aqueous concentrations of metal cations. An anion exchange reaction model was incorporated to simulate sulfate, U and Tc sorption onto variably charged (pH-dependent) Al and Fe hydroxides. Modeling results indicate that competitive sorption/desorption on mixed mineral phases needs to be considered to adequately predict U and Tc mobility. The model could be useful for future studies of the speciation of U, Tc and co-existing ions during pre- and post-groundwater treatment practices.

  2. Phosphate rock treatment with citric acid for the rapid potentiometric determination of fluoride with ion-selective electrode.

    PubMed

    Al-Othman, A O; Sweileh, J A

    2000-04-28

    A fast method for sample treatment of phosphate rock has been developed for the purpose of quantitative leaching (98-100%) of fluoride but less of the interfering cations such as iron and aluminum. Citric acid (0.5 M) was used to extract fluoride in 15-45 min. Leaching of iron and aluminum is minimal, and these ions are complexed with citric acid. The leaching method was optimized with respect to sample size, citric acid concentration, leaching time and temperature. The analysis was completed by the rapid determination of fluoride with ion-selective electrode. The proposed treatment method was applied to phosphate rock samples from Jordan and Morocco and yielded accurate results as compared to the standard steam distillation from strong acid solution followed by thorium nitrate titration. PMID:18967930

  3. 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-?-cyclodextrin [(triacetyl-?-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. PMID:23200395

  4. Potentiometric CO titrations of carbon monoxide dehydrogenase and CO-inhibition of the NI-removing reaction with 1,10--phenanthroline 

    E-print Network

    Russell, William Kent

    1996-01-01

    Carbon monoxide dehydrogenase from Clostridium thermoaceticum catalyzes two reactions involving redox chemistry (the reversible oxidation Of CO to C02, and the synthesis of acetyl-CoA) using three types of Ni and Fe-S structures called the A-, B...

  5. Potentiometric CO titrations of carbon monoxide dehydrogenase and CO-inhibition of the NI-removing reaction with 1,10--phenanthroline

    E-print Network

    Russell, William Kent

    1996-01-01

    Carbon monoxide dehydrogenase from Clostridium thermoaceticum catalyzes two reactions involving redox chemistry (the reversible oxidation Of CO to C02, and the synthesis of acetyl-CoA) using three types of Ni and Fe-S structures called the A-, B...

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

    PubMed

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

    2015-10-01

    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. PMID:25830410

  7. Sorption and desorption of quaternary amine cations on clays

    SciTech Connect

    Zhang, Z.Z.; Sparks, D.L. (Univ. of Delaware, Newark, DE (United States)); Scrivner, N.C. (DuPont Engineering, Newark, DE (United States))

    1993-08-01

    The authors have studied the sorption and desorption of three quaternary amines, namely, nonyltrimethylammonium, dodecyltrimethylammonium, and hexadecyltrimethylammonium, on homoionic Na- and K-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were sorbed on the montmorillonite when the added amines were less than 70% of the cation-exchange capacity of the montmorillonite. Sorption of quaternary amine cations involves at least two types of reactions, namely, an exchange reaction and the adsorption of amines at nonexchangeable sites. The exchange reaction proceeded almost to completion when Na[sup +] was the exchangeable cation. Exchangeable K[sup +] was much more difficult to replace. The adsorbed quaternary amine cations were not easily desorbed in the presence of 0.1 M NaCl and KCl solutions. In addition, desorption of quaternary amines did not increase with prolonged equilibrium time, up to 180 days. Therefore, it appears that there is good promise in using quaternary amine-modified clays as effective sorbents for removing organic pollutants or mitigating their mobilities in the environment. 26 refs., 5 figs., 6 tabs.

  8. Direct measurement of protein binding energetics by isothermal titration calorimetry

    Microsoft Academic Search

    Stephanie Leavitt; Ernesto Freire

    2001-01-01

    Of all the techniques that are currently available to measure binding, isothermal titration calorimetry is the only one capable of measuring not only the magnitude of the binding affinity but also the magnitude of the two thermodynamic terms that define the binding affinity: the enthalpy (?H) and entropy (?S) changes. Recent advances in instrumentation have facilitated the development of experimental

  9. Titration of Isolated Cell Walls of Lemna minor L.

    PubMed

    Morvan, C; Demarty, M; Thellier, M

    1979-06-01

    A theoretical model has been built to bypass the equation of titration of the cell wall. This equation, which is an extension of the Henderson-Hasselbach equation, underlines the importance of the exchange constant, the ionic strength as well as the rate of neutralization. The model is restricted to the case when the ionization degree is equal to the neutralization degree. The shape of the titration curve is shown to be strongly dependent on the valency of the base used.Experimental results have shown that isolated cell walls bear at least two kinds of sites. The first sites which are titrated after a short time of equilibration are attributed to polyuronic acids (capacity: 0.3 milliequivalents per gram fresh cell walls). The second sites, are obtained after a long time of equilibration (capacity: 1.2 to 1.3 milliequivalents per gram, fresh cell walls). Titrations have been performed with different bases [KOH, NaOH, and Ca(OH)(2)] and under different ionic strengths.The results obtained with NaOH and KOH do not exhibit any difference of selectivity. Conversely, the sites have a much bigger affinity for the Ca(2+) ions than for the monovalent ones. The apparent pKa of the uronic acids was estimated to lie between 3.0 and 3.4; this is consistent with the values obtained with polyuronic acid solutions. PMID:16660868

  10. Titration of Isolated Cell Walls of Lemna minor L 1

    PubMed Central

    Morvan, Claudine; Demarty, Maurice; Thellier, Michel

    1979-01-01

    A theoretical model has been built to bypass the equation of titration of the cell wall. This equation, which is an extension of the Henderson-Hasselbach equation, underlines the importance of the exchange constant, the ionic strength as well as the rate of neutralization. The model is restricted to the case when the ionization degree is equal to the neutralization degree. The shape of the titration curve is shown to be strongly dependent on the valency of the base used. Experimental results have shown that isolated cell walls bear at least two kinds of sites. The first sites which are titrated after a short time of equilibration are attributed to polyuronic acids (capacity: 0.3 milliequivalents per gram fresh cell walls). The second sites, are obtained after a long time of equilibration (capacity: 1.2 to 1.3 milliequivalents per gram, fresh cell walls). Titrations have been performed with different bases [KOH, NaOH, and Ca(OH)2] and under different ionic strengths. The results obtained with NaOH and KOH do not exhibit any difference of selectivity. Conversely, the sites have a much bigger affinity for the Ca2+ ions than for the monovalent ones. The apparent pKa of the uronic acids was estimated to lie between 3.0 and 3.4; this is consistent with the values obtained with polyuronic acid solutions. PMID:16660868

  11. Titrating-Delay Matching-to-Sample in the Pigeon

    PubMed Central

    Kangas, Brian D; Vaidya, Manish; Branch, Marc N

    2010-01-01

    The titrating-delay matching-to-sample (TDMTS) procedure offers researchers an additional behavioral task thought to capture some important features of remembering. In this procedure, the delay between sample offset and comparison onset adjusts as a function of the subject's performance. Specifically, correct matches increase the delay and incorrect matches decrease the delay, and steady-state titrated delays serve as the primary dependent measure. The present series of experiments investigated the effects of several procedural variables on performance in TDMTS procedures in an effort to elucidate better its features to allow for more precision in future use. Experiment 1 reports results from a parametric analysis of fixed-ratio response requirements on the sample key that indicated improved remembering in the form of higher daily titrated delay values as the requirement was increased. Experiment 2 investigated the extent to which the initial delay value in each session affected session-wide delay values. Results indicated that regardless of value of the initial delay, the subjects' performances adjusted the delay values in the direction of the known baseline delay-value levels. Experiment 3 manipulated the step size by which delay values were adjusted and the results indicated that larger step sizes increased both session-to-session variability and within-session range of titrated delay values, although the average values remained approximately the same. These results suggest that the TDMTS task serves as a promising procedure to study what many refer to as memory. PMID:21279163

  12. Titrating-Delay Matching-to-Sample in the Pigeon

    ERIC Educational Resources Information Center

    Kangas, Brian D.; Vaidya, Manish; Branch, Marc N.

    2010-01-01

    The titrating-delay matching-to-sample (TDMTS) procedure offers researchers an additional behavioral task thought to capture some important features of remembering. In this procedure, the delay between sample offset and comparison onset adjusts as a function of the subject's performance. Specifically, correct matches increase the delay and…

  13. Characterisation of iron binding ligands in seawater by reverse titration.

    PubMed

    Hawkes, Jeffrey A; Gledhill, Martha; Connelly, Douglas P; Achterberg, Eric P

    2013-03-01

    Here we demonstrate the use of reverse titration - competitive ligand exchange-adsorptive cathodic stripping voltammetry (RT-CLE-ACSV) for the analysis of iron (Fe) binding ligands in seawater. In contrast to the forward titration, which examines excess ligands in solution, RT-CLE-ACSV examines the existing Fe-ligand complexes by increasing the concentration of added (electroactive) ligand (1-nitroso-2-naphthol) and analysis of the proportion of Fe bound to the added ligand. The data manipulation allows the accurate characterisation of ligands at equal or lower concentrations than Fe in seawater, and disregards electrochemically inert dissolved Fe such as some colloidal phases. The method is thus superior to the forward titration in environments with high Fe and low ligand concentrations or high concentrations of inert Fe. We validated the technique using the siderophore ligand ferrioxamine B, and observed a stability constant [Formula: see text] of 0.74-4.37×10(21) mol(-1), in agreement with previous results. We also successfully analysed samples from coastal waters and a deep ocean hydrothermal plume. Samples from these environments could not be analysed with confidence using the forward titration, highlighting the effectiveness of the RT-CLE-ACSV technique in waters with high concentrations of inert Fe. PMID:23427800

  14. Potentiometric enzyme immunoassay using miniaturized anion-selective electrodes for detection

    PubMed Central

    Sz?cs, Júlia; Pretsch, Ernö; Gyurcsányi, Róbert E.

    2010-01-01

    An enzyme-linked immunosorbent assay (ELISA) for prostate specific antigen (PSA) detection in human serum was developed based on the potentiometric detection of 6,8-difluoro-4-methylumbelliferone (DiFMU). The assays were carried out in anti-human PSA capture-antibody modified microtiter plates (150 µl volume). After incubation in the PSA containing serum samples, ?-galactosidase-labeled PSA tracer antibody was added. The ?-galactosidase label catalyzed the hydrolysis of 6,8-difluoro-4-methylumbelliferyl-?-D-galactopyranoside (DiFMUG) and the resulting DiFMU? anion was detected by potentiometric microelectrodes with anion-exchanger membrane. The selectivity of the anion-exchanger electrode is governed by the lipophilicity of the anions in the sample. Since DiFMU? is much more lipophilic (log P = 1.83) than any of the inorganic anions normally present in the working buffers and occurs in its anionic form at the physiological pH (pKa = 4.19), it was chosen as the species to be detected. The potentiometric ELISA-based method detects PSA in serum with a linear concentration range of 0.1–50 ng/mL. These results confirm the applicability of potentiometric detection in diagnostic PSA assays. Owing to simple methodology and low cost, potentiometric immunoassays seem to offer a feasible alternative to the development of in vitro diagnostic platforms. PMID:20448926

  15. Potentiometric enzyme immunoassay using miniaturized anion-selective electrodes for detection.

    PubMed

    Szucs, Júlia; Pretsch, Ernö; Gyurcsányi, Róbert E

    2009-08-01

    An enzyme-linked immunosorbent assay (ELISA) for prostate specific antigen (PSA) detection in human serum was developed based on the potentiometric detection of 6,8-difluoro-4-methylumbelliferone (DiFMU). The assays were carried out in anti-human PSA capture antibody modified microtiter plates (150 microL volume). After incubation in the PSA-containing serum samples, beta-galactosidase-labeled PSA tracer antibody was added. The beta-galactosidase label catalyzed the hydrolysis of 6,8-difluoro-4-methylumbelliferyl-beta-D-galactopyranoside (DiFMUG) and the resulting DiFMU(-) anion was detected by potentiometric microelectrodes with anion-exchanger membrane. The selectivity of the anion-exchanger electrode is governed by the lipophilicity of the anions in the sample. Since DiFMU(-) is much more lipophilic (log P = 1.83) than any of the inorganic anions normally present in the working buffers and occurs in its anionic form at the physiological pH (pK(a) = 4.19), it was chosen as the species to be detected. The potentiometric ELISA-based method detects PSA in serum with a linear concentration range of 0.1-50 ng/mL. These results confirm the applicability of potentiometric detection in diagnostic PSA assays. Owing to simple methodology and low cost, potentiometric immunoassays seem to offer a feasible alternative to the development of in vitro diagnostic platforms. PMID:20448926

  16. The cyclopropyl cation 

    E-print Network

    Hampton, Loyd Ernest

    1969-01-01

    THE CYCLOPROPYL CATION A Thesis by Loyd Ernest Hampton, Jr. Submitted to the Graduate College of Texas AAN University in partial fulfillment of the requirement for the degree of MASTER OP SCIENCE August month 1969 year Na]or Subyeot... Chemistry THE CYCLOPROPXL CATION A 1'hesis Loyd Ernest Hampton, Jr. Approved as to style and content bye Head of' Oepar ent / Co-chairman ember Nember Nem er em er Au ust Non h l 6 Year 111 ABSTRACT The Cyclopropyl Cation. (August 1969) Loyd...

  17. Investigation of the spatial resolution of the light-addressable potentiometric sensor (LAPS) , W. J. Parak1*

    E-print Network

    Moritz, Werner

    Investigation of the spatial resolution of the light-addressable potentiometric sensor (LAPS) M.parak@physik.uni-muenchen.de Abstract The spatial resolution of the light-addressable potentiometric sensor (LAPS) is investigated both, the effective diffusion length of light generated charge carriers parallel to the sensor surface was measured

  18. The difference between the potentiometric surfaces of the Magothy Aquifer of September 1982 and September 1984 in southern Maryland

    USGS Publications Warehouse

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

    1985-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Magothy aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  19. Difference between the potentiometric surfaces of the Magothy Aquifer in Fall of 1975 and Fall of 1986 in southern Maryland

    USGS Publications Warehouse

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

    1987-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Magothy aquifer; (2) the approximate location of the line of equal difference between the potentiometric surface in fall 1975 and fall 1986; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  20. Difference between the potentiometric surface of the Aquia Aquifer in Spring of 1979 and Fall of 1986 in southern Maryland

    USGS Publications Warehouse

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

    1987-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Aquia aquifer; (2) the approximate line of equal distance between the potentiometric surfaces of spring 1979 and fall 1986; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  1. 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)

  2. 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)

  3. Carbonic acid ionization and the stability of sodium bicarbonate and carbonate ion pairs to 200 °C - A potentiometric and spectrophotometric study

    NASA Astrophysics Data System (ADS)

    Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

    2013-11-01

    Carbonic acid ionization and sodium bicarbonate and carbonate ion pair formation constants have been experimentally determined in dilute hydrothermal solutions to 200 °C. Two experimental approaches were applied, potentiometric acid-base titrations at 10-60 °C and spectrophotometric pH measurements using the pH indicators, 2-napthol and 4-nitrophenol, at 25-200 °C. At a given temperature, the first and second ionization constants of carbonic acid (K1, K2) and the ion pair formation constants for NaHCO(aq)(K) and NaCO3-(aq)(K) were simultaneously fitted to the data. Results of this study compare well with previously determined values of K1 and K2. The NaHCO(aq) and NaCO3-(aq) ion pair formation constants vary between 25 and 200 °C having values of logK=-0.18 to 0.58 and logK=1.01 to 2.21, respectively. These ion pairs are weak at low-temperatures but become increasingly important with increasing temperature under neutral to alkaline conditions in moderately dilute to concentrated NaCl solutions, with NaCO3-(aq) predominating over CO32-(aq) in ?0.1 M NaCl solution at temperatures above 100 °C. The results demonstrate that NaCl cannot be considered as an inert (non-complexing) electrolyte in aqueous carbon dioxide containing solutions at elevated temperatures.

  4. 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

  5. Biosensors based on light-addressable potentiometric sensors for urea, penicillin and glucose

    Microsoft Academic Search

    Atsushi Seki; Syuu-ichi Ikeda; Izumi Kubo; Isao Karube

    1998-01-01

    Novel potentiometric biosensors based on light-addressable potentiometric sensors for detection of glucose, penicillin and urea as model compounds are described. n-type silicon substrates covered with SiO2 and\\/or Al2O3 were applied as a pH sensor. The Al2O3 and SiO2 films were pH-sensitive in the range pH 3–11. The pH-sensitive electrode was applied to produce biosensors for glucose, penicillin and urea by

  6. Propagation of error in fulvic acid titration data: a comparison of three analytical methods

    E-print Network

    Morel, François M. M.

    Propagation of error in fulvic acid titration data: a comparison of three analytical methods but little consideration has been given to the magnitude of error in the resulting titration data. Most of random instrumenterror into a titrationdata set is not uniform throughout a titration and the pattern

  7. Can Patients with Obstructive Sleep Apnea Titrate Their Own Continuous Positive Airway Pressure?

    Microsoft Academic Search

    Michael F. Fitzpatrick; Christi E. D. Alloway; Tracy M. Wakeford; Alistair W. MacLean; Peter W. Munt; Andrew G. Day

    Manual continuous positive airway pressure (CPAP) titration in a tions (9) can improve the efficiency with which CPAP treat- sleep laboratory is costly and limits access for diagnostic studies. ment is delivered, as compared with conventional in-labora- Many factors affect CPAP compliance, but education and support, tory overnight CPAP titration. Given the high disease rather than in-laboratory CPAP titration, appear

  8. The Acid-Base Titration of a Very Weak Acid: Boric Acid

    ERIC Educational Resources Information Center

    Celeste, M.; Azevedo, C.; Cavaleiro, Ana M. V.

    2012-01-01

    A laboratory experiment based on the titration of boric acid with strong base in the presence of d-mannitol is described. Boric acid is a very weak acid and direct titration with NaOH is not possible. An auxiliary reagent that contributes to the release of protons in a known stoichiometry facilitates the acid-base titration. Students obtain the…

  9. Free Software Development. 3. Numerical Description of Weak Acid with Weak Base Titration

    Microsoft Academic Search

    Lorentz JÄNTSCHI; Horea Iustin

    2002-01-01

    The analytical methods of qualitative and quantitative determination of ions in solutions are very flexible to automation. The present work is focus on modeling the process of titration and presents a numerical simulation of acid-base titration. A PHP program to compute all iterations in titration process that solves a 3 th rank equation to find value of pH for was

  10. Kids in a Candy Store: An Analogy for Back Titration

    NASA Astrophysics Data System (ADS)

    Last, Arthur M.

    1998-09-01

    A simple analogy for back titration is presented. A child is sent into a candy store with a known amount of money in order to purchase a candy bar and the cost of the bar is subsequently determined by counting the amount of change the child brings back. This is analogous to adding excess acid to a base and determining how much base was present by titrating the unreacted acid. The analogy is extended to illustrate what happens when an acidic or basic impurity is present in the system and is further developed to cover a situation in which the acid and unknown base react in a 2:1 ratio rather than a 1:1 ratio.

  11. Chromazurol S ion-selective electrode for chelatometric titration.

    PubMed

    Kataoka, M; Shin, M; Kambara, T

    1977-04-01

    A liquid membrane type Chromazurol S ion-selective electrode has been constructed and applied to chelatometric titrations. In aqueous medium, zephiramine (benzyldimethyltetradecylammonium chloride) forms with the anion of Chromazurol S an ion-pair which is easily extracted into nitrobenzene. The extract is used as the liquid ion-exchanger for the Chromazurol S ion-selective electrode. The most suitable ion-pair concentration in the liquid ion-exchanger membrane is 10(-4)M. The linear Nernstian-response range of the Chromazurol S anion in aqueous solution is 10(-2)-10(-6)M. The electrode has been successfully applied to the chelatometric titration of Cu(II), Ni(II), Fe(III) and Pb(II) with EDTA. PMID:18962078

  12. A high sensitivity titration calorimeter using pyroelectric sensor

    Microsoft Academic Search

    E. K. Merabet; H. K. Yuen; W. A. Grote; K. L. Deppermann

    1994-01-01

    A new sensitive isothermal titration microcalorimeter using polyvinylidene difluoride (PVDF) as detector has been developed.\\u000a Heat pulses of less than 0.4 ?J can be detected and the baseline noise level (p-p) is 40 nW. The calorimeter is constructed with one reaction cell (0.7 ml) insulated by several radiation shields inside a\\u000a vacuum chamber. The performance of the instrument was examined

  13. Quantitative estimation of benzylisoquinoline derivatives by coulometric titration

    Microsoft Academic Search

    G. K. Ziyatdinova; A. I. Samigullin; S. G. Abdullina; G. K. Budnikov

    2008-01-01

    A method for estimating papaverine HCl and drotaverine HCl by coulometric titration with biamperometric indication of the\\u000a end point was developed. The stoichiometric coefficients of the reactions of papaverine and drotaverine with electrogenerated\\u000a chlorine were determined. Microgram quantities of agents in substance and therapeutic forms were estimated with a relative\\u000a standard deviation (RSD) of 0.01–0.03.

  14. Automatic karl fischer titration of moisture in sunflower seed

    Microsoft Academic Search

    James A. Robertson; W. R. Windham

    1983-01-01

    An automatic Karl Fischer (KF) titrator of the motor-driven buret type was applied to the determination of moisture in sunflower\\u000a seed. A study of the effect of sample size on KF moisture analysis showed a significant decrease in moisture content with\\u000a increase in sample size from 1 to 5 g. In the moisture range of 5.5–10.5%, a sample size of

  15. New developments for the numerical analysis of spectrophotometric titrations

    Microsoft Academic Search

    Raylene M. Dyson; Porn Jandanklang; Marcel Maeder; Caroline J. Mason; Andrew Whitson

    1999-01-01

    Spectrophotometric titrations are a valuable tool for the investigation of solution equilibria. Data acquisition and recent developments on methods for the analysis of the measurements are discussed in this contribution. Hard-modeling methods are based on non-linear least-squares fitting, and algorithms have been developed which can cope with the large amount of data and parameters of multiwavelength or multivariate measurements. Good

  16. Topiramate slow dose titration: improved efficacy and tolerability.

    PubMed

    Albsoul-Younes, Abla M; Salem, Hazem A; Ajlouni, Saleh F; Al-Safi, Saafan A

    2004-11-01

    Topiramate is an effective treatment for several types of seizures. The aim of this study is to assess the efficacy and tolerability of slow topiramate dose titration as add-on therapy in childhood epilepsy. This investigation is a prospective open-label, single-center, add-on study in 22 children with a diagnosis of refractory epilepsy. Topiramate (dose 0.5-2 mg/kg/day) was titrated at 2-week intervals up to the recommended dose of 6-12 mg/kg/day. Seizure frequency rate reduction was significant, declining from 23 +/- 5.1 seizures/week (mean +/- S.E.M.) at baseline phase to 3.5 +/- 1.2 seizures/week at the end of the 16-week stabilization phase (P < 0.001). After 16 weeks of stabilization, 19 patients (86%) had more than 50% seizure reduction. Seven patients (31%) were 100% seizure-free. Two patients (9%) manifested no improvement; only one patient (5%) did not tolerate the added drug and discontinued topiramate. One patient manifested severe side effects, whereas 21 patients experienced mild to moderate side effects mostly represented by somnolence, nervousness, and anorexia with or without weight loss. We conclude that slow dose titration improves efficacy and tolerability of topiramate as add-on therapy in the treatment in refractory epilepsy. PMID:15519117

  17. Titrating and evaluating multi-drug regimens within subjects.

    PubMed

    Shih, Margaret; Gennings, Chris; Chinchilli, Vernon M; Carter, Walter H

    2003-07-30

    The dosing of combination therapies is commonly undertaken empirically by practising physicians, and a coherent algorithm to approach the problem of combination dosing is currently lacking. Current methods of evaluating multiple drug combinations in clinical trials fail to provide information regarding the location of more effective doses when the combination is not found to differ from the standard, even though the absence of a difference does not necessarily mean the new combination is ineffective. Moreover, in studies where the new combination is found more effective, often a large proportion of the study participants obtain no benefit from the trial. Even with early stopping rules, the time these subjects spend on inferior treatments can have lasting detrimental effects, leading to problems with patient enrolment and adherence to study protocol. This paper describes an evolutionary operation (EVOP) direct-search procedure to titrate combination doses within individual patients. The Nelder-Mead simplex direct-search algorithm is used to titrate combinations of drugs within individual subjects. Desirability functions are utilized to define the main response of interest and additional responses or constraints. Statistical methodology for determining whether the titrated treatment combination has resulted in an improvement in subject response and for evaluating for therapeutic synergism is developed. Inferences can then be made about the efficacy of the combination or about the individual drugs that comprise the combination. The advantages of this approach include affording every patient the potential to benefit from the combination under study and permitting the consideration of multiple endpoints simultaneously. PMID:12854092

  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. pH titration monitored by quantum cascade laser-based vibrational circular dichroism.

    PubMed

    Rüther, Anja; Pfeifer, Marcel; Lórenz-Fonfría, Víctor A; Lüdeke, Steffen

    2014-04-10

    Vibrational circular dichroism (VCD) spectra of aqueous solutions of proline were recorded in the course of titrations from basic to acidic pH using a spectrometer equipped with a quantum cascade laser (QCL) as an infrared light source in the spectral range from 1320 to 1220 cm(-1). The pH-dependent spectra were analyzed by singular value decomposition and global fitting of a two-pK Henderson-Hasselbalch model. The analysis delivered relative fractions of the three different protonation species. Their agreement with the relative fractions obtained from performing the same analysis on pH-dependent Fourier transform infrared (FT-IR) and QCL-IR spectra validates the quantitative results from QCL-VCD. Global fitting of the pH-dependent VCD spectra of L-proline allowed for extraction of pure spectra corresponding to anionic, zwitterionic, and cationic L-proline. From a static experiment, only pure spectra of the zwitterion would be accessible in a straightforward way. A comparison to VCD spectra calculated for all three species led to assignment of vibrational modes that are characteristic for the respective protonation states. The study demonstrates the applicability of QCL-VCD both for quantitative evaluation and for qualitative interpretation of dynamic processes in aqueous solutions. PMID:24655319

  20. 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

  1. 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)

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

    PubMed

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

    2015-01-01

    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

  3. Biosensor for direct determination of organophosphate nerve agents. 1. Potentiometric enzyme electrode

    Microsoft Academic Search

    Priti Mulchandani; Ashok Mulchandani; Irina Kaneva; Wilfred Chen

    1999-01-01

    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 with bovine serum albumin (BSA) and glutaraldehyde. OPH catalyses the hydrolysis of organophosphorus pesticides to release protons, the concentration of which is

  4. 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.

  5. A Solid-State Potentiometric Sensor for Monitoring Hydrogen in Commercial Pipeline Steel

    Microsoft Academic Search

    D. R. Morris; L. R. Wan

    1995-01-01

    A solid-state potentiometric sensor for monitoring hydrogen in commercial pipeline steel was developed. Performance of the sensor was investigated using five commercial steels into which hydrogen was introduced by gas charging or by corrosion reactions. The equivalent pressure of hydrogen (p{sub Hâeq}) in the steel as determined by the sensor was related to the concentration of hydrogen and to the

  6. Can the light-addressable potentiometric sensor (LAPS) detect extracellular potentials of cardiac myocytes?

    Microsoft Academic Search

    Wolfgang J. Parak; Michael George; Jan Domke; Manfred Radmacher; Jan C. Behrends; Morgan C. Denyer; Hermann E. Gaub

    2000-01-01

    The light-addressable potentiometric sensor (LAPS) measures localized photo-induced currents from a silicon wafer, which are dependent on the local surface potential and on the intensity of the light pointer. In this study the ability of the LAPS to record extracellular potentials of adherent cells was investigated. Time dependent LAPS photocurrent signals that correlated in time with contractions were recorded from

  7. Lateral resolution of light-addressable potentiometric sensors: an experimental and theoretical investigation

    Microsoft Academic Search

    Wolfgang J. Parak; Ulrich G. Hofmann; Hermann E. Gaub; John C. Owicki

    1997-01-01

    The surface potential of semiconductor devices in contact with electrolyte solutions is an important part of signal transduction for a variety of bioanalytical devices. Here we have investigated the lateral resolution at which the surface potential may be measured with a semiconductor-based device, a light-addressable potentiometric sensor (LAPS). We have first established an experimental setup where a permanent charge pattern

  8. Investigation of the spatial resolution of the light-addressable potentiometric sensor

    Microsoft Academic Search

    M. George; W. J. Parak; I. Gerhardt; W. Moritz; F. Kaesen; H. Geiger; I. Eisele; H. E. Gaub

    2000-01-01

    The spatial resolution of the light-addressable potentiometric sensor (LAPS) is investigated both theoretically and experimentally. For a theoretical analysis, the diffusion equation for minority charge carriers in the semiconductor was solved. The results suggest that by thinning the semiconductor wafer, the spatial resolution of the LAPS is no longer limited by the bulk minority charge carrier diffusion length. Spatial resolution

  9. “LAPS Card”—A novel chip card-based light-addressable potentiometric sensor (LAPS)

    Microsoft Academic Search

    T. Wagner; C. Rao; J. P. Kloock; T. Yoshinobu; R. Otto; M. Keusgen; M. J. Schöning

    2006-01-01

    A novel design of a light-addressable potentiometric sensor (LAPS) for the realisation of an easy exchangeable and modular measurement set-up is presented in this work. The sensor chip for up to 16 independent sensor spots is integrated in a standard plastic card and the appropriate measurement cell allows a selection of different chip cards within seconds. The measurement cell contains

  10. Potentiometric flow injection determination of amylase activity by using hexacyanoferrate(III)-hexacyanoferrate(II) potential buffer

    Microsoft Academic Search

    Hiroki Ohura; Toshihiko Imato; Yasukazu Asano; Sumio Yamasaki

    1998-01-01

    A highly sensitive potentiometric flow injection determination of amylase activity was carried out, utilizing a redox reaction of hexacyanoferrate(III) in alkaline media with reducing sugar as product of the enzymatic hydrolysis reaction of starch with amylase. The analytical method is based on the potential change detection of a flow-through type redox electrode detector due to the composition change of a

  11. 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…

  12. Direct Determinationof Cadmiumand Lead in Whole Blood by Potentiometric Stripping Analysis

    Microsoft Academic Search

    Peter Ostapczuk

    The commercially available equipment for potentiometric stripping analysis (PSA) was tested for routine lead and cadmium determination in whole-blood samples. In con- trast to anodic stripping voltammetry, PSA is not subject to background interferences from organic electroactive constituents in the sample or to the presence of dissolved oxygen (i.e., oxygen removal is not necessary). To deter- mine lead and cadmium

  13. Carbon Paste Electrode for the Potentiometric Flow Injection Analysis of Drotaverine Hydrochloride in Serum and Urine

    Microsoft Academic Search

    Yousry M. Issa; Hosny Ibrahim; Hazem M. Abu-Shawish

    2005-01-01

    A carbon paste electrode for drotaverine hydrochloride (DvCl) was prepared and fully characterized in terms of composition, life span, usable pH range, response time and temperature. The electrode was applied to the potentiometric determination of drotaverinium ions in pharmaceutical preparations and biological fluids in steady state and flow injection conditions (FIA). The electrode is based on a mixture of two

  14. 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)

  15. Reversible potentiometric oxygen sensors based on polymeric and metallic film electrodes.

    PubMed

    Yim, H S; Meyerhoff, M E

    1992-09-01

    Various materials and sensor configurations that exhibit reversible potentiometric responses to the partial pressure of oxygen at room temperature in neutral pH solution are examined. In one arrangement, platinum electrodes are coated with plasticized poly(vinyl chloride) films doped with a cobalt(II) tetraethylene pentamine complex. For such sensors, potentiometric oxygen response is attributed to a mixed potential originating from the underlying platinum electrode surface as well as a change in redox potential of the Co(II)-tetren-doped film as the complex binds oxygen reversibly. The response due to the platinum surface is prolonged by the presence of the Co(II)-tetren/PVC film. Alternately, thin films of metallic copper, electrochemically deposited on platinum and/or sputtered or vapor deposited on a single crystal silicon substrate, may be used for reversible oxygen sensing. The long-term reversibility and potentiometric stability of such copper film-based sensors is enhanced (up to 1 month) by preventing the formation of cuprous oxide on the surfaces via the application of an external nonpolarizing cathodic current through the working electrode or by specifically using sputtered copper films that have [100] preferred crystal structures as determined by X-ray diffraction. The implications of these findings in relation to fabricating analytically useful potentiometric oxygen sensors are discussed. PMID:1416035

  16. 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 used for the 1986-87 potentiometric-surface map. Well symbols with circles on the 2009 potentiometric-surface map (fig. 1) indicate wells that were used for the 1986-87 potentiometric-surface map.

  17. Cation binding to 15-TBA quadruplex DNA is a multiple-pathway cation-dependent process

    PubMed Central

    Reshetnikov, Roman V.; Sponer, Jiri; Rassokhina, Olga I.; Kopylov, Alexei M.; Tsvetkov, Philipp O.; Makarov, Alexander A.; Golovin, Andrey V.

    2011-01-01

    A combination of explicit solvent molecular dynamics simulation (30 simulations reaching 4?µs in total), hybrid quantum mechanics/molecular mechanics approach and isothermal titration calorimetry was used to investigate the atomistic picture of ion binding to 15-mer thrombin-binding quadruplex DNA (G-DNA) aptamer. Binding of ions to G-DNA is complex multiple pathway process, which is strongly affected by the type of the cation. The individual ion-binding events are substantially modulated by the connecting loops of the aptamer, which play several roles. They stabilize the molecule during time periods when the bound ions are not present, they modulate the route of the ion into the stem and they also stabilize the internal ions by closing the gates through which the ions enter the quadruplex. Using our extensive simulations, we for the first time observed full spontaneous exchange of internal cation between quadruplex molecule and bulk solvent at atomistic resolution. The simulation suggests that expulsion of the internally bound ion is correlated with initial binding of the incoming ion. The incoming ion then readily replaces the bound ion while minimizing any destabilization of the solute molecule during the exchange. PMID:21893589

  18. 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.

  19. Altitude and configuration of the potentiometric surface, Casey Village, Warminster and Upper Southampton townships, Bucks County, Pennsylvania, August 3, 1995

    USGS Publications Warehouse

    Sloto, Ronald A.; Grazul, Kevin E.

    1995-01-01

    A map showing the potentiometric surface in Casey Village, Warminster and Upper Southampton Townships, Bucks County, was constructed from water levels measured on August 3, 1995. The potentiometric surface, measured in 17 wells screened between 18 and 64 feet below land surface, ranged from 321.99 to 344.80 feet above sea level. The potentiometric surface, measured in 12 wells screened between 48 and 108 feet below land surface, ranged from 321.95 to 337.50 feet above sea level.

  20. classi cation, regression,

    E-print Network

    Roweis, Sam

    function K(x 1 ;x 2 ) called a kernel. #15; This has a very deep interpretation as mapping the dataLecture 13: Kernel Machines Sam Roweis December 4, 2002 Algorithms Based on Vector Data #15; Recall our normal approach to many classi#12;cation, regression, and unsupervised learning problems: Embed

  1. classi cation, regression,

    E-print Network

    Roweis, Sam

    Lecture 13: Kernel Machines Sam Roweis December 2, 2003 Algorithms Based on Vector Data #15; Recall our normal approach to many classi#12;cation, regression, and unsupervised learning problems: Embed operations. #15;We can often make our algorithms more powerful by embedding the data into a richer (larger

  2. A titration model for evaluating calcium hydroxide removal techniques

    PubMed Central

    PHILLIPS, Mark; McCLANAHAN, Scott; BOWLES, Walter

    2015-01-01

    Objective Calcium hydroxide (Ca(OH)2) has been used in endodontics as an intracanal medicament due to its antimicrobial effects and its ability to inactivate bacterial endotoxin. The inability to totally remove this intracanal medicament from the root canal system, however, may interfere with the setting of eugenol-based sealers or inhibit bonding of resin to dentin, thus presenting clinical challenges with endodontic treatment. This study used a chemical titration method to measure residual Ca(OH)2 left after different endodontic irrigation methods. Material and Methods Eighty-six human canine roots were prepared for obturation. Thirty teeth were filled with known but different amounts of Ca(OH)2 for 7 days, which were dissolved out and titrated to quantitate the residual Ca(OH)2 recovered from each root to produce a standard curve. Forty-eight of the remaining teeth were filled with equal amounts of Ca(OH)2 followed by gross Ca(OH)2 removal using hand files and randomized treatment of either: 1) Syringe irrigation; 2) Syringe irrigation with use of an apical file; 3) Syringe irrigation with added 30 s of passive ultrasonic irrigation (PUI), or 4) Syringe irrigation with apical file and PUI (n=12/group). Residual Ca(OH)2 was dissolved with glycerin and titrated to measure residual Ca(OH)2 left in the root. Results No method completely removed all residual Ca(OH)2. The addition of 30 s PUI with or without apical file use removed Ca(OH)2 significantly better than irrigation alone. Conclusions This technique allowed quantification of residual Ca(OH)2. The use of PUI (with or without apical file) resulted in significantly lower Ca(OH)2 residue compared to irrigation alone. PMID:25760272

  3. Titratable acidity of beverages influences salivary pH recovery.

    PubMed

    Tenuta, Livia Maria Andaló; Fernández, Constanza Estefany; Brandão, Ana Carolina Siqueira; Cury, Jaime Aparecido

    2015-01-01

    A low pH and a high titratable acidity of juices and cola-based beverages are relevant factors that contribute to dental erosion, but the relative importance of these properties to maintain salivary pH at demineralizing levels for long periods of time after drinking is unknown. In this crossover study conducted in vivo, orange juice, a cola-based soft drink, and a 10% sucrose solution (negative control) were tested. These drinks differ in terms of their pH (3.5 ± 0.04, 2.5 ± 0.05, and 5.9 ± 0.1, respectively) and titratable acidity (3.17 ± 0.06, 0.57 ± 0.04 and < 0.005 mmols OH- to reach pH 5.5, respectively). Eight volunteers with a normal salivary flow rate and buffering capacity kept 15 mL of each beverage in their mouth for 10 s, expectorated it, and their saliva was collected after 15, 30, 45, 60, 90, and 120 s. The salivary pH, determined using a mini pH electrode, returned to the baseline value at 30 s after expectoration of the cola-based soft drink, but only at 90 s after expectoration of the orange juice. The salivary pH increased to greater than 5.5 at 15 s after expectoration of the cola drink and at 30 s after expectoration of the orange juice. These findings suggest that the titratable acidity of a beverage influences salivary pH values after drinking acidic beverages more than the beverage pH. PMID:25715032

  4. Potentiometric surface of the Black Creek Aquifer in the central coastal plain of North Carolina, December 1986

    USGS Publications Warehouse

    Lyke, William L.; Winner, M.D., Jr.; Brockman, Allen Richard

    1989-01-01

    Water level measurements were made in 95 wells open to the Black Creek aquifer at the end of 1986 to determine the configuration of its potentiometric surface over an area of about 4,900 sq mi in the central Coastal Plain of North Carolina. The altitude of the potentiometric surface of the Black Creek ranges between 80 and 100 ft above sea level along the western limit of the aquifer. From there the potentiometric surface slopes southeasterly toward a large, elongated cone of depression that has coalesced from cones that have developed around three main pumping centers and several smaller ones. The potentiometric surface in the Black Creek has declined to more than 120 ft below sea level in the southernmost cone developing near Jacksonville in Onslow County.

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

    USGS Publications Warehouse

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

    1990-01-01

    A map was prepared that shows the net change in the potentiometric surface of the Aquia aquifer (in the Paleocene Aquia Formation) in southern Maryland from the fall of 1986 to the fall of 1988. The map, based on water level measurements from 74 observation wells, shows that during the 2 year period the potentiometric surface declined less than 6 ft in most of southern Maryland but 10 ft or more in the Lexington Park and Solomons Island areas. (USGS)

  6. Acetoclastic methanogenic activity measurement by a titration bioassay.

    PubMed

    Rozzi, Alberto; Castellazzi, Luca; Speece, Richard E

    2002-01-01

    A titration bioassay, designed to accurately determine the activity of acetoclastic methanogens, is described that also allows evaluation of inhibition due to potential toxicants on the active biomass. The instrument is made of a pH-stat connected to an anaerobic batch reactor. Acetate is blended and mixed with anaerobic sludge in the reactor where a 1:1 N2 and CO2 mixture is sparged at the beginning of each test. As the acetoclastic methanogens consume acetate, the pH increase, and the titration unit adds acetic acid and keeps the pH constant. The rate of titrant addition is directly proportional to the methanogenic activity. A very useful feature of the system is its potential to operate for long periods (days) at constant pH and substrate (acetate) concentration. The theoretical background and principle of operation are described as well as some of the practical problems encountered with the use of the instrument. Estimation of kinetic constants for an anaerobic culture according to the Michaelis-Menten model is presented. Examples of inhibition by inorganics (NaCl) and chlorinated solvents (chloroform) are also given. PMID:11745170

  7. Characterization of the kinetic and thermodynamic landscape of RNA folding using a novel application of isothermal titration calorimetry.

    PubMed

    Vander Meulen, Kirk A; Butcher, Samuel E

    2012-03-01

    A novel isothermal titration calorimetry (ITC) method was applied to investigate RNA helical packing driven by the GAAA tetraloop-receptor interaction in magnesium and potassium solutions. Both the kinetics and thermodynamics were obtained in individual ITC experiments, and analysis of the kinetic data over a range of temperatures provided Arrhenius activation energies (?H(‡)) and Eyring transition state entropies (?S(‡)). The resulting rich dataset reveals strongly contrasting kinetic and thermodynamic profiles for this RNA folding system when stabilized by potassium versus magnesium. In potassium, association is highly exothermic (?H(25°C) = -41.6 ± 1.2 kcal/mol in 150 mM KCl) and the transition state is enthalpically barrierless (?H(‡) = -0.6 ± 0.5). These parameters are significantly positively shifted in magnesium (?H(25°C) = -20.5 ± 2.1 kcal/mol, ?H(‡) = 7.3 ± 2.2 kcal/mol in 0.5 mM MgCl(2)). Mixed salt solutions approximating physiological conditions exhibit an intermediate thermodynamic character. The cation-dependent thermodynamic landscape may reflect either a salt-dependent unbound receptor conformation, or alternatively and more generally, it may reflect a small per-cation enthalpic penalty associated with folding-coupled magnesium uptake. PMID:22058128

  8. Characterization of the kinetic and thermodynamic landscape of RNA folding using a novel application of isothermal titration calorimetry

    PubMed Central

    Vander Meulen, Kirk A.; Butcher, Samuel E.

    2012-01-01

    A novel isothermal titration calorimetry (ITC) method was applied to investigate RNA helical packing driven by the GAAA tetraloop–receptor interaction in magnesium and potassium solutions. Both the kinetics and thermodynamics were obtained in individual ITC experiments, and analysis of the kinetic data over a range of temperatures provided Arrhenius activation energies (?H‡) and Eyring transition state entropies (?S‡). The resulting rich dataset reveals strongly contrasting kinetic and thermodynamic profiles for this RNA folding system when stabilized by potassium versus magnesium. In potassium, association is highly exothermic (?H25°C?=??41.6?±?1.2?kcal/mol in 150?mM KCl) and the transition state is enthalpically barrierless (?H‡?=??0.6?±?0.5). These parameters are sigificantly positively shifted in magnesium (?H25°C?=??20.5?±?2.1?kcal/mol, ?H‡?=?7.3?±?2.2?kcal/mol in 0.5?mM MgCl2). Mixed salt solutions approximating physiological conditions exhibit an intermediate thermodynamic character. The cation-dependent thermodynamic landscape may reflect either a salt-dependent unbound receptor conformation, or alternatively and more generally, it may reflect a small per-cation enthalpic penalty associated with folding-coupled magnesium uptake. PMID:22058128

  9. Development of a method for estimating an accurate equivalence point in nickel titration of cyanide ions

    Microsoft Academic Search

    Toshihiro Suzuki; Akiharu Hioki; Masayasu Kurahashi

    2003-01-01

    In a nickel titration of cyanide ions using murexide as indicator, an accurate equivalence point was determined by a non-linear least-squares curve-fitting for a titration curve. This method was developed to establish a standard solution for cyanide ions. In a curve-fitting procedure, a theoretical titration curve was calculated, assuming that nickel ion formed only a 1:4 Ni2+:CN? complex with cyanide

  10. 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.

  11. Rapid Detection of High Charge Density Polyanion Contaminants in Biomedical Heparin Preparations Using Potentiometric Polyanion Sensors

    PubMed Central

    Wang, Lin; Buchanan, Stacey; Meyerhoff, Mark E.

    2009-01-01

    A very simple and inexpensive method to detect oversulfated chondroitin sulfate (OSCS) or other high charge density polyanionic structures as contaminants in heparin products using potentiometric polyanion sensors is described. In the potentiometric measurement, a greater change in the phase boundary equilibrium potential of polymeric membranes formulated with tridodecylmethylammonium (TDMA) anion exchange sites is observed for the contaminated heparin than for the untainted heparin due to the higher charge density of OSCS or other impurities compared to that of porcine heparin. Detection of 0.5 wt% OSCS impurity is readily achieved using only 1 mg/mL of final polyion concentration. Even lower detection limits for OSCS contamination may be possible if higher final concentrations of heparin preparations can be employed in the test procedure. PMID:19007240

  12. Potentiometric surface of the Aquia 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 Aquia aquifer in the Paleocene Aquia Formation in southern Maryland during the fall of 1988 was constructed on the basis of water level measurements made at 84 observation 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; it was below sea level in the remainder of the study area. The hydraulic gradient generally was to the southeast toward an extensive cone of depression centered around well fields near Lexington Park and Solomons Island. Water levels were more than 60 ft below sea level in a 50 sq-mi area near the center of the cone and were more than 100 ft below sea level at two of the wells near the center of the cone. (USGS)

  13. 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.

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

    USGS Publications Warehouse

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

    2005-01-01

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

  15. Potentiometric 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.

  16. The study of some possible measurement errors in clinical blood electrolyte potentiometric (ISE) analysers.

    PubMed

    Rumenjak, Vlatko; Milardovi?, Stjepan; Kruhak, Ivan; Grabari?, Bozidar S

    2003-09-01

    The understanding of the most important sources of error in potentiometric blood analyser which might contribute to better instruments measurement repeatability is very often marginalized in fabrications and daily operation of some commercial blood analysers. In this paper ISEs-potentiometric measurements were performed and validated in Clinical Institute of Laboratory Diagnosis of the Zagreb University School of Medicine and Clinical Hospital Centre, using a carefully designed and constructed fully automated (computerised) homemade ISE-based blood electrolyte analyser constructed with an in-line five-channel flow-through measuring cell. The influence of electrolyte concentration of the salt bridge is reported. Special attention has been paid to the reference electrode design, and constructions which can operate in open liquid junction and membrane restricted liquid junction modes are described. PMID:12927687

  17. PVC membrane sensor based on periodate—Cetylpyridinium ion pair for the potentiometric determination of periodate

    Microsoft Academic Search

    Abdelhameed M. Othman

    2010-01-01

    A new plasticized membrane sensor has been proposed for the determination of periodate based on periodate-cetylpyridinium\\u000a ion pair complex. The electrode shows a linear, reproducible and stable potentiometric response with anionic Nernstian slope\\u000a of 58.1 ± 0.5 mV\\/decade over a wide range of concentrations 10?5–10?2 M and a detection limit of 2.0 × 10?6 M of IO4?. The membrane exhibits

  18. Neurochip based on light-addressable potentiometric sensor with wavelet transform de-noising

    Microsoft Academic Search

    Qing-jun Liu; Wei-wei Ye; Hui Yu; Ning Hu; Li-ping Du; Ping Wang

    2010-01-01

    Neurochip based on light-addressable potentiometric sensor (LAPS), whose sensing elements are excitable cells, can monitor\\u000a electrophysiological properties of cultured neuron networks with cellular signals well analyzed. Here we report a kind of\\u000a neurochip with rat pheochromocytoma (PC12) cells hybrid with LAPS and a method of de-noising signals based on wavelet transform.\\u000a Cells were cultured on LAPS for several days to

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

    PubMed Central

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

    1985-01-01

    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). PMID:4091553

  20. Flow injection potentiometric stripping analysis for study of adsorption of heavy metal ions onto modified diatomite

    Microsoft Academic Search

    Mohammad A. Al-Ghouti; Majeda A. M. Khraisheh; Maha Tutuji

    2004-01-01

    Computerised flow injection coupled with potentiometric stripping analysis (FIPSA) was employed for examination of the adsorption behaviour of Pb(II), Cd(II) and Zn(II) ions onto diatomite modified with manganese oxides. Signal optimisation was undertaken with respect to flow rate, deposition time, deposition potential, oxidising agent concentration, thickness of mercury film, solution pH and metal ion concentration. Examination of the column adsorption

  1. Potentiometric dissolved oxygen sensors with reference electrode integrated in thick film technology

    Microsoft Academic Search

    R. Martinez-Manez; J. Soto Camino; E. Garcia-Breijo; L. Gil Sanchez; J. Ibanez Civera; E. Gadea Morant

    2005-01-01

    New designed dissolved oxygen potentiometric sensors in thick film technology based in the use of RuO 2 as active material and TiO 2 or polyisoftalamide diphenylsulphone (PIDS) as membranes have been developed. TiO 2-coated RuO 2 electrodes showed a linear response as a function of the logarithm of the dissolved oxygen concentration in the 0.5-8 ppm range. The electrode displays

  2. Extracellular measurements of averaged ionic currents with the light-addressable potentiometric sensor (LAPS)

    Microsoft Academic Search

    B. Stein; M. George; H. E. Gaub; W. J. Parak

    2004-01-01

    The light-addressable potentiometric sensor (LAPS) is a silicon-based detector which allows for measuring the electric potential distribution along its surface. The point of measurement is determined by illumination with a pulsed light source, and therefore the surface potential distribution can be measured spatially resolved by raster scanning a light-pointer along the surface. In this study electrically excitable neuronal cells (N1-E115

  3. Picogram detection levels of asialofetuin via the carbohydrate moieties using the light addressable potentiometric sensor

    Microsoft Academic Search

    Kilian Dill; John D. Olson

    1995-01-01

    Fetal calf serum asialofetuin was assayed in the sandwich format using biotinylated and fluoresceinated ricin toxin (B-RCA and F-RCA). The sandwiched species was captured on a biotin-BSA coated nitrocellulose membrane with streptavidin. Anti-fluorescein antibody-urease conjugate was bound to the complex, and detected and quantitated under microvolume conditions using the light addressable potentiometric sensor. As little as 250 pg of asialofetuin

  4. Investigation on light-addressable potentiometric sensor as a possible cell–semiconductor hybrid

    Microsoft Academic Search

    Tatsuo Yoshinobu; Hiroshi Iwasaki; Hirokazu Sugihara; Tetsuo Yukimasa; Isao Hirata; Hiroo Iwata

    2003-01-01

    This article reports an investigation on light-addressable potentiometric sensor (LAPS) to be used as a possible biological cell–semiconductor hybrid that will enable us to make an interface between the physical and biological system. To increase the surface potential sensitivity, we used a LAPS structure with single insulator (SiO2) coated with poly-l-ornithine and laminin (PLOL) on Si. Efficient culturing of PC-12

  5. Detection of plasmids using DNA and RNA probes and the light-addressable potentiometric sensor

    Microsoft Academic Search

    Kilian Dill; Samuel D. H Chan; Thomas W Gibbs

    1997-01-01

    Intact plasmids, plasmid fragments, and cDNA were detected using two DNA or RNA probes of varying lengths, each containing only biotin or fluorescein molecules. The probes were hybridized with the target plasmid\\/cDNA, bound with streptavidin, captured on nitrocellulose membranes, and detected using the urease-conjugate of an anti-fluorescein antibody via the light-addressable potentiometric sensor. The output of the silicon-chip sensor is

  6. Cell-based biosensors based on light-addressable potentiometric sensors for single cell monitoring

    Microsoft Academic Search

    Gaixia Xu; Xuesong Ye; Lifeng Qin; Ying Xu; Yan Li; Rong Li; Ping Wang

    2005-01-01

    Cell-based biosensors incorporate cells as sensing elements that convert changes in immediate environment to signals for processing. This paper reports an investigation on light-addressable potentiometric sensor (LAPS) to be used as a possible cell-base biosensor that will enable us to monitor extracellular action potential of single living cell under stimulant. In order to modify chip surface and immobilize cells, we

  7. The light-addressable potentiometric sensor for multi-ion sensing and imaging

    Microsoft Academic Search

    T. Yoshinobu; H. Iwasaki; Y. Ui; K. Furuichi; Yu. Ermolenko; Yu. Mourzina; T. Wagner; N. Näther; M. J. Schöning

    2005-01-01

    The light-addressable potentiometric sensor (LAPS) is a semiconductor-based chemical sensor with an electrolyte–insulator–semiconductor structure. The LAPS can have many measuring points integrated on the sensing surface, which are individually accessed by a light beam. By modifying the measuring points with different materials, a single sensor plate can be used as a multi-analyte sensor. In this paper, instrumentation and application of

  8. Potentiometric detection in UPLC as an easy alternative to determine cocaine in biological samples.

    PubMed

    Daems, Devin; van Nuijs, Alexander L N; Covaci, Adrian; Hamidi-Asl, Ezat; Van Camp, Guy; Nagels, Luc J

    2015-07-01

    The analytical methods which are often used for the determination of cocaine in complex biological matrices are a prescreening immunoassay and confirmation by chromatography combined with mass spectrometry. We suggest an ultra-high-pressure liquid chromatography combined with a potentiometric detector, as a fast and practical method to detect and quantify cocaine in biological samples. An adsorption/desorption model was used to investigate the usefulness of the potentiometric detector to determine cocaine in complex matrices. Detection limits of 6.3?ng?mL(-1) were obtained in plasma and urine, which is below the maximum residue limit (MRL) of 25?ng?mL(-1) . A set of seven plasma samples and 10 urine samples were classified identically by both methods as exceeding the MRL or being inferior to it. The results obtained with the UPLC/potentiometric detection method were compared with the results obtained with the UPLC/MS method for samples spiked with varying cocaine concentrations. The intraclass correlation coefficient was 0.997 for serum (n =7) and 0.977 for urine (n =8). As liquid chromatography is an established technique, and as potentiometry is very simple and cost-effective in terms of equipment, we believe that this method is potentially easy, inexpensive, fast and reliable. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25516367

  9. 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

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

    PubMed

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

    2014-04-15

    This article describes the fabrication, characterization and application of an epidermal temporary-transfer tattoo-based potentiometric sensor, coupled with a miniaturized wearable wireless transceiver, for real-time monitoring of sodium in the human perspiration. Sodium excreted during perspiration is an excellent marker for electrolyte imbalance and provides valuable information regarding an individual's physical and mental wellbeing. The realization of the new skin-worn non-invasive tattoo-like sensing device has been realized by amalgamating several state-of-the-art thick film, laser printing, solid-state potentiometry, fluidics and wireless technologies. The resulting tattoo-based potentiometric sodium sensor displays a rapid near-Nernstian response with negligible carryover effects, and good resiliency against various mechanical deformations experienced by the human epidermis. On-body testing of the tattoo sensor coupled to a wireless transceiver during exercise activity demonstrated its ability to continuously monitor sweat sodium dynamics. The real-time sweat sodium concentration was transmitted wirelessly via a body-worn transceiver from the sodium tattoo sensor to a notebook while the subjects perspired on a stationary cycle. The favorable analytical performance along with the wearable nature of the wireless transceiver makes the new epidermal potentiometric sensing system attractive for continuous monitoring the sodium dynamics in human perspiration during diverse activities relevant to the healthcare, fitness, military, healthcare and skin-care domains. PMID:24333582

  11. 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.

  12. Potentiometric and spectrophotometric study of the stability of magnesium carbonate and bicarbonate ion pairs to 150 °C and aqueous inorganic carbon speciation and magnesite solubility

    NASA Astrophysics Data System (ADS)

    Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

    2014-08-01

    The formation constants of magnesium bicarbonate and carbonate ion pairs have been experimentally determined in dilute hydrothermal solutions to 150 °C. Two experimental approaches were applied, potentiometric acid-base titrations at 10-60 °C and spectrophotometric pH measurements using two pH indicators, 2-naphthol and 4-nitrophenol, at 25 and 80-150 °C. At a given temperature, the first and second ionization constants of carbonic acid (K1, K2) and the ion pair formation constants for MgHCO3+(aq) (KMgHCO3+) and MgCO3(aq) (KMgCO3) were simultaneously fitted to the data. Results of this study compare well with previously determined values of K1 and K2. The formation constants of MgHCO3+(aq) and MgCO3(aq) ion pairs increased significantly with increasing temperature, with values of logKMgHCO3+ = 1.14 and 1.75 and of logKMgCO3 = 2.86 and 3.48 at 10 °C and 100 °C, respectively. These ion pairs are important aqueous species under neutral to alkaline conditions in moderately dilute to concentrated Mg-containing solutions, with MgCO3(aq) predominating over CO32-(aq) in solutions at pH >8. The predominance of magnesium carbonate over carbonate is dependent on the concentration of dissolved magnesium and the ratio of magnesium over carbonate. With increasing temperature and at alkaline pH, brucite solubility further reduced the magnesium concentration to levels below 1 mmol kg-1, thus limiting availability of Mg2+(aq) for magnesite precipitation.

  13. [Secretory IgA: quality control of the titration method].

    PubMed

    Rosaschino, F; Torre, R; Grisler, R

    In order to verify if the method for the titration of salivary secretory IgA (s-IgA) by the technical of radial immunodiffusion is trustworthy, have been carried out the precision tests in the series and among the series in two saliva samples with very different s-IgA concentrations, and precision and accuracy tests in the series and among the series using a solution with a known titre of IgA. The results of the first battery tests have shown a precision ranging from 93.04 to 95.43%. The results of the tests of the second battery have shown a precision ranging about 96% and an accuracy about 97%. The tested method is, therefore, sufficiently trustworthy. PMID:1670042

  14. 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 approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 19-23, 2008. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2008). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

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

    USGS Publications Warehouse

    Ortiz, A.G.

    2006-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District (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-level conditions, respectively. Most of the water-level data for this map were collected by the USGS during September 19-23, 2005. Suppplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the SWFWMD boundary by the USGS office in Altamonte Springs, Florida (Kinnaman, 2006). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

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

    USGS Publications Warehouse

    Ortiz, A.G.

    2008-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in September 2007. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the wet season, when ground-water levels usually are at an annual high and withdrawals for agricultural use typically are low. The cumulative average rainfall of 39.50 inches for west-central Florida (from October 2006 through September 2007) was 13.42 inches below the historical cumulative average of 52.92 inches (Southwest Florida Water Management District, 2007). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period September 17-21, 2007. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2008). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

  17. 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 approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 21-25, 2007. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2007). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

  18. 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 year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period September 15-19, 2008. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2009). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

  19. 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 year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during September 18-22, 2006. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman, 2007). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal high water-level condition.

  20. The interactions of ?-carrageenan with cationic surfactants in aqueous solutions.

    PubMed

    Yin, Tianxiang; Qin, Miao; Yang, Yan; Zheng, Peizhu; Fan, Dashuang; Shen, Weiguo

    2014-06-21

    The interactions between the anionic polymer ?-carrageenan (IC) and the cationic surfactants 1-dodecyl-3-methylimidazolium bromide (C12mimBr), dodecyltrimethylammonium bromide (DTAB) and ethyl-?,?-bis(dodecyldimethylammonium)dibromide (12-2-12) have been studied by fluorimetry and isothermal titration calorimetry. Our experimental results showed that at a low surfactant concentration, the monomers adsorbed on the IC chains through the electrostatic attraction, followed by the formation of induced micelles on the IC chains through the hydrophobic interaction until the IC chains are saturated by surfactant molecules; after that the added surfactant formed free micelles in the solution. A pseudo-phase-equilibrium thermodynamic model was proposed to explain the experimental results and to understand the mechanisms of the interactions in these three systems. Moreover, the salt effect on the interactions was investigated and found that it changed the critical concentrations but not the interaction mechanism. PMID:24752291

  1. Understanding and mitigating conductivity transitions in weak cation exchange chromatography.

    PubMed

    Fogle, Jace; Hsiung, Jenny

    2010-01-29

    Large conductivity fluctuations were observed during a high pH wash step in a weak cation exchange chromatography process. These conductivity transitions resulted in a conductivity drop during pH increase and a conductivity rise during pH decrease. In some cases, the absolute conductivity change was greater than 6mS/cm which was sufficient to affect target protein retention on the column. Further investigation revealed that wash buffer concentration, resin ligand density, and resin ligand pK have a profound effect on the magnitude of the conductivity transitions and the shape of corresponding pH traces. A potentiometric electrode selective for sodium ions was used to measure effluent counterion concentrations from two preparative resins during high pH washes, and the number of exchangeable counterions was compared to predictions made using ion exchange equilibrium theory. Results from this analysis show that conductivity transitions can be effectively mitigated without compromising process performance by optimizing the trade-off between wash buffer concentration and wash phase duration. PMID:20022015

  2. 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 approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 18-22, 2009. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Orlando, Florida (Kinnaman and Dixon, 2009). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition. The potentiometric contours are generalized to synoptically portray the head in a dynamic hydrologic system, taking due account of the variations in hydrogeologic conditions, such as differing depths of wells, nonsimultaneous measurements of water levels, variable effects of pumping, and changing climatic influence. The potentiometric contours may not conform exactly with the individual measurements of water levels.

  3. Using RNA sample titrations to assess microarray platform performance and normalization techniques

    Microsoft Academic Search

    Stephanie Fulmer-Smentek; Roderick V Jensen; Wendell D Jones; Paul K Wolber; Charles D Johnson; P Scott Pine; Cecilie Boysen; Xu Guo; Eugene Chudin; Yongming Andrew Sun; James C Willey; Jean Thierry-Mieg; Danielle Thierry-Mieg; Robert A Setterquist; Mike Wilson; Anne Bergstrom Lucas; Natalia Novoradovskaya; Adam Papallo; Yaron Turpaz; Shawn C Baker; Janet A Warrington; Leming Shi; Damir Herman; Richard Shippy

    2006-01-01

    We have assessed the utility of RNA titration samples for evaluating microarray platform performance and the impact of different normalization methods on the results obtained. As part of the MicroArray Quality Control project, we investigated the performance of five commercial microarray platforms using two independent RNA samples and two titration mixtures of these samples. Focusing on 12,091 genes common across

  4. From Titration Data to Buffer Capacities: A Computer Experiment for the Chemistry Lab or Lecture

    Microsoft Academic Search

    Roy W. Clark; Gary D. White; Judith M. Bonicamp; Exum D. Watts

    1995-01-01

    This paper, for chemistry teachers who have beginning students, computers, and spreadsheets, presents tables of titration data simulated using the program EQUIL. Instructors are invited to give students the titration data to enter into their spreadsheets, have them plot it in several ways, and produce an assortment of graphs. In the process, they will discover many things about pH,. the

  5. Binding of globular proteins to lipid membranes studied by isothermal titration calorimetry and fluorescence

    Microsoft Academic Search

    Mariana N Dimitrova; Hideo Matsumura; Nelly Terezova; Vassil Neytchev

    2002-01-01

    The interactions of bovine serum albumin, lysozyme and cytochrome c with phosphatidylcholine liposomes in liquid crystalline phase have been investigated using isothermal titration calorimetry in combination with steady state, and fluorescence measurements. Calorimetric titration studies of the binding of liposomes to the protein species indicate in all cases exothermic processes with single binding sites in the protein molecule. Distinct saturation

  6. Factors governing the assembly of cationic phospholipid-DNA complexes.

    PubMed Central

    Kennedy, M T; Pozharski, E V; Rakhmanova, V A; MacDonald, R C

    2000-01-01

    The interaction of DNA with a novel cationic phospholipid transfection reagent, 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EDOPC), was investigated by monitoring thermal effects, particle size, vesicle rupture, and lipid mixing. By isothermal titration calorimetry, the heat of interaction between large unilamellar EDOPC vesicles and plasmid DNA was endothermic at both physiological and low ionic strength, although the heat absorbed was slightly larger at the higher ionic strength. The energetic driving force for DNA-EDOPC association is thus an increase in entropy, presumably due to release of counterions and water. The estimated minimum entropy gain per released counterion was 1.4 cal/mole- degrees K (about 0.7 kT), consistent with previous theoretical predictions. All experimental approaches revealed significant differences in the DNA-lipid particle, depending upon whether complexes were formed by the addition of DNA to lipid or vice versa. When EDOPC vesicles were titrated with DNA at physiological ionic strength, particle size increased, vesicles ruptured, and membrane lipids became mixed as the amount of DNA was added up to a 1.6:1 (+:-) charge ratio. This charge ratio also corresponded to the calorimetric end point. In contrast, when lipid was added to DNA, vesicles remained separate and intact until a charge ratio of 1:1 (+:-) was exceeded. Under such conditions, the calorimetric end point was 3:1 (+:-). Thus it is clear that fundamental differences in DNA-cationic lipid complexes exist, depending upon their mode of formation. A model is proposed to explain the major differences between these two situations. Significant effects of ionic strength were observed; these are rationalized in terms of the model. The implications of the analysis are that considerable control can be exerted over the structure of the complex by exploiting vectorial preparation methods and manipulating ionic strength. PMID:10692346

  7. Macromolecular Competition Titration Method: Accessing Thermodynamics of the Unmodified Macromolecule–Ligand Interactions Through Spectroscopic Titrations of Fluorescent Analogs

    PubMed Central

    Bujalowski, Wlodzimierz; Jezewska, Maria J.

    2011-01-01

    Analysis of thermodynamically rigorous binding isotherms provides fundamental information about the energetics of the ligand–macromolecule interactions and often an invaluable insight about the structure of the formed complexes. The Macromolecular Competition Titration (MCT) method enables one to quantitatively obtain interaction parameters of protein–nucleic acid interactions, which may not be available by other methods, particularly for the unmodified long polymer lattices and specific nucleic acid substrates, if the binding is not accompanied by adequate spectroscopic signal changes. The method can be applied using different fluorescent nucleic acids or fluorophores, although the etheno-derivatives of nucleic acid are especially suitable as they are relatively easy to prepare, have significant blue fluorescence, their excitation band lies far from the protein absorption spectrum, and the modification eliminates the possibility of base pairing with other nucleic acids. The MCT method is not limited to the specific size of the reference nucleic acid. Particularly, a simple analysis of the competition titration experiments is described in which the fluorescent, short fragment of nucleic acid, spanning the exact site-size of the protein–nucleic acid complex, and binding with only a 1:1 stoichiometry to the protein, is used as a reference macromolecule. Although the MCT method is predominantly discussed as applied to studying protein–nucleic acid interactions, it can generally be applied to any ligand–macromolecule system by monitoring the association reaction using the spectroscopic signal originating from the reference macromolecule in the presence of the competing macromolecule, whose interaction parameters with the ligand are to be determined. PMID:21195223

  8. Dose titration of BAF312 attenuates the initial heart rate reducing effect in healthy subjects

    PubMed Central

    Legangneux, Eric; Gardin, Anne; Johns, Donald

    2013-01-01

    Aim Previous studies have shown transient decreases in heart rate (HR) following administration of sphingosine 1?phosphate (S1P) receptor modulators including BAF312. This study was conducted to determine whether dose titration of BAF312 reduces or eliminates these effects. Methods Fifty?six healthy subjects were randomized 1:1:1:1 to receive BAF312 in one of two dose titration (DT) regimens (DT1 and DT2: 0.25–10?mg over 9–10?days), no titration (10?mg starting dose) or placebo. Pharmacodynamic and pharmacokinetic parameters were assessed. Results Neither DT1 nor DT2 resulted in clinically significant bradycardia or atrioventricular conduction effects. Both titration regimens showed a favourable difference on each of days 1–12 vs. the non?titration regimen on day 1 for HR effects (P < 0.0001). On day 1, the geometric mean ratio of the fraction from the previous day in minimum daily HR between DT1 and non?titration was 1.18 (95% confidence interval [CI] 1.13, 1.23) and 1.14 (95% CI 1.09, 1.18) for DT2 (both P < 0.05) with significant differences noted through to day 12. Non?titration HRs showed considerable separation from placebo throughout the study. There was no statistically significant reduction in HR vs. placebo on day?1 in either titration regimen. On days 3–7 subjects in DT1 and DT2 experienced minor reductions in HR vs. placebo (approximately 5?beats?min?1; P ? 0.0001). From days 9–12, HRs in both titration regimens were comparable with placebo. Conclusion Both titration regimens effectively attenuated the initial bradyarrhythmia observed on day 1 of treatment with BAF312 10?mg. PMID:22845008

  9. Water Content Determination of Rubber Stoppers Utilized for Sealing Lyophilized Pharmaceutical Products: Assessment of Two Karl Fischer Titration Methods

    E-print Network

    Voth, Laura Marie

    2013-08-31

    methods for measurement of the water content of rubber stoppers: a gravimetric method and a Karl Fischer (KF) titration method with oven. A third less common test method is the Karl Fischer titration method with tetrahydrofuran (THF) extraction...

  10. Modeling and optimization of the bi-substrate peroxidase-enzyme catalyzed potentiometric assay of hydrogen peroxide by response surface methodology with a central composite rotatable design

    Microsoft Academic Search

    Farzad Deyhimi; Faezeh Nami

    2011-01-01

    In view of the great importance of determination of hydrogen peroxide in many chemical, biological, clinical, environmental processes, and the attractive operational simplicity of potentiometric approach for the enzymatic assay, after preliminary optimization, the efficient response surface methodology (RSM) with a central composite rotatable design (CCRD), was used for modeling and optimization of the initial-rate potentiometric method of HRP enzyme

  11. Preliminary map showing the difference between the potentiometric surfaces of the Aquia Aquifer of September 1982 and September 1984 in southern Maryland

    USGS Publications Warehouse

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

    1985-01-01

    The potentiometric map is highlighted with indications concerning: (1) outcrop areas of the Aquia aquifer; (2) the potentiometric contour of the aquifer; (3) observation and/or supply wells yielding < 10,000 gallons/day (gpd); and (4) other supply wells with yields > 10,000 gpd. (Lantz-PTT)

  12. Survey of the year 2008: applications of isothermal titration calorimetry.

    PubMed

    Falconer, Robert J; Penkova, Anita; Jelesarov, Ilian; Collins, Brett M

    2010-01-01

    Isothermal titration calorimetry (ITC) is a fast, accurate and label-free method for measuring the thermodynamics and binding affinities of molecular associations in solution. Because the method will measure any reaction that results in a heat change, it is applicable to many different fields of research from biomolecular science, to drug design and materials engineering, and can be used to measure binding events between essentially any type of biological or chemical ligand. ITC is the only method that can directly measure binding energetics including Gibbs free energy, enthalpy, entropy and heat capacity changes. Not only binding thermodynamics but also catalytic reactions, conformational rearrangements, changes in protonation and molecular dissociations can be readily quantified by performing only a small number of ITC experiments. In this review, we highlight some of the particularly interesting reports from 2008 employing ITC, with a particular focus on protein interactions with other proteins, nucleic acids, lipids and drugs. As is tradition in these reviews we have not attempted a comprehensive analysis of all 500 papers using ITC, but emphasize those reports that particularly captured our interest and that included more thorough discussions we consider exemplify the power of the technique and might serve to inspire other users. PMID:20213668

  13. Enzyme kinetics determined by single-injection isothermal titration calorimetry.

    PubMed

    Transtrum, Mark K; Hansen, Lee D; Quinn, Colette

    2015-04-01

    The purposes of this paper are (a) to examine the effect of calorimeter time constant (?) on heat rate data from a single enzyme injection into substrate in an isothermal titration calorimeter (ITC), (b) to provide information that can be used to predict the optimum experimental conditions for determining the rate constant (k2), Michaelis constant (KM), and enthalpy change of the reaction (?RH), and (c) to describe methods for evaluating these parameters. We find that KM, k2 and ?RH can be accurately estimated without correcting for the calorimeter time constant, ?, if (k2E/KM), where E is the total active enzyme concentration, is between 0.1/? and 1/? and the reaction goes to at least 99% completion. If experimental conditions are outside this domain and no correction is made for ?, errors in the inferred parameters quickly become unreasonable. A method for fitting single-injection data to the Michaelis-Menten or Briggs-Haldane model to simultaneously evaluate KM, k2, ?RH, and ? is described and validated with experimental data. All four of these parameters can be accurately inferred provided the reaction time constant (k2E/KM) is larger than 1/? and the data include enzyme saturated conditions. PMID:25497059

  14. Titration of the gap junction protein Connexin43 reduces atherogenesis.

    PubMed

    Morel, S; Chanson, M; Nguyen, T D; Glass, A M; Richani Sarieddine, M Z; Meens, M J; Burnier, L; Kwak, B R; Taffet, S M

    2014-08-01

    Ubiquitous reduction of the gap junction protein Connexin43 (Cx43) in mice provides beneficial effects on progression and composition of atherosclerotic lesions. Cx43 is expressed in multiple atheroma-associated cells but its function in each cell type is not known. To examine specifically the role of Cx43 in immune cells, we have lethally irradiated low-density lipoprotein receptor-deficient mice and reconstituted with Cx43+/+, Cx43+/- or Cx43-/- haematopoietic fetal liver cells. Progression of atherosclerosis was significantly lower in aortic roots of Cx43+/- chimeras compared with Cx43+/+ and Cx43-/- chimeras, and their plaques contained significantly less neutrophils. The relative proportion of circulating leukocytes was similar between the three groups. Interestingly, the chemoattraction of neutrophils, which did not express Cx43, was reduced in response to supernatant secreted by Cx43+/- macrophages in comparison with the ones of Cx43+/+ and Cx43-/- macrophages. Cx43+/- macrophages did not differ from Cx43+/+ and Cx43-/- macrophages in terms of M1/M2 polarisation but show modified gene expression for a variety chemokines and complement components. In conclusion, titration of Cx43 expression in bone marrow-derived macrophages reduces atherosclerotic plaque formation and chemoattraction of neutrophils to the lesions. PMID:24828015

  15. The titration of the active centers of cellobiohydrolase from Trichoderma reesei.

    PubMed

    Rabinowitch, M L; Klyosov, A A; Melnick, M S

    1986-08-01

    A novel approach has been developed for the titration of enzyme active centers and for the determination of the molecular activity of enzymes. It is based on the simultaneous use of a nonspecific chromogenic substrate and a specific ligand (a substrate or an inhibitor), the latter being tightly bound with the enzyme's active center. The approach is demonstrated using the titration (that is, the determination of the molar concentration of the enzyme active centers) of purified cellobiohydrolase I (CBH I) (EC 3.2.1.91) of the fungus Trichoderma reesei. p-Nitrophenyl-beta-D-lactoside was used as a reference substrate (Km = 0.5 mM), and cellobiose and CM-cellulose as specific ligands. The molecular weight of CBH I as it was determined by the titration with cellobiose was 42,000 +/- 3,000. The inhibition constant by cellobiose was (6 +/- 1) X 10(-6) M. The value of the catalytic constant for the hydrolysis of p-nitrophenyl-beta-D-lactoside calculated from the titration data was equal to 0.063 s-1. CM-cellulose turned out to be more efficient titration agent for cellobiohydrolase than cellobiose, and might be used for the titration of the enzyme in concentrations of the latter of 0.008-0.02 mg/ml. The titration data showed that the inhibition constant of CM-cellulose toward CBH I was equal to (1.0 +/- 0.2) X 10(-7) M. PMID:3766948

  16. A sequential injection electronic tongue employing the transient response from potentiometric sensors for anion multidetermination

    Microsoft Academic Search

    M. Cortina; A. Duran; S. Alegret; M. del Valle

    2006-01-01

    Intelligent and automatic systems based on arrays of\\u000a non-specific-response chemical sensors were recently developed in our\\u000a laboratory. For multidetermination applications, the normal choice is an\\u000a array of potentiometric sensors to generate the signal, and an\\u000a artificial neural network (ANN) correctly trained to obtain the\\u000a calibration model. As a great amount of information is required for the\\u000a proper modelling, we proposed

  17. Underground Test Area Subproject Phase I Data Analysis Task. Volume II - Potentiometric Data Document Package

    SciTech Connect

    None

    1996-12-01

    Volume II of the documentation for the Phase I Data Analysis Task performed in support of the current Regional Flow Model, Transport Model, and Risk Assessment for the Nevada Test Site Underground Test Area Subproject contains the potentiometric data. Because of the size and complexity of the model area, a considerable quantity of data was collected and analyzed in support of the modeling efforts. The data analysis task was consequently broken into eight subtasks, and descriptions of each subtask's activities are contained in one of the eight volumes that comprise the Phase I Data Analysis Documentation.

  18. Potentiometric surface of the upper Floridan aquifer, west-central Florida, May 2011

    USGS Publications Warehouse

    Ortiz, Anita G.

    2011-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2011. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 45.74 inches for west-central Florida (from June 2010 through May 2011) was 6.85 inches below the historical cumulative average of 52.59 inches (Southwest Florida Water Management District, 2011). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September from 1975 through 2010. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 23-27, 2011. Supplemental water-level data were collected by other agencies and companies. Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a "snapshot" of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

  19. Potentiometric Surface of the Upper Floridan Aquifer, West-central Florida, May 2010

    USGS Publications Warehouse

    Ortiz, A.G.

    2010-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2010. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when groundwater levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 55.21 inches for west-central Florida (from June 2009 through May 2010) was 2.55 inches above the historical cumulative average of 52.66 inches (Southwest Florida Water Management District, 2010). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 17-21, 2010. Supplemental water-level data were collected by other agencies and companies. Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition.

  20. New ionophores for vitamin B1 and vitamin B6 potentiometric sensors for multivitaminic control

    Microsoft Academic Search

    Ana Rita Pires; Alberto N. Araújo; M. Conceição B. S. M. Montenegro; Petr Chocholous; Petr Solich

    2008-01-01

    The construction, evaluation and analytical application of potentiometric sensors sensitive to vitamin B1 and vitamin B6 are reported. The solid contact electrodes were produced using ?-cyclodextrins as ionophores in a carboxylated poly(vinyl chloride) support matrix. Near Nernstian slopes (mV\\/decade) of 51.7±0.8, 60.6±0.6 and 61.1±1.4, within the intervals (M) of 1.0×10?4 to 1.0×10?1, 5.8×10?5 to 1.0×10?1 and 4.3×10?5 to 1.0×10?1 were

  1. Ionselective light-addressable potentiometric sensor (LAPS) with chalcogenide thin film prepared by pulsed laser deposition

    Microsoft Academic Search

    Y. Mourzina; T. Yoshinobu; J. Schubert; H. Lüth; H. Iwasaki; M. J. Schöning

    2001-01-01

    Pb–Ag–As–I–S chalcogenide glass was deposited on the surface of a light-addressable potentiometric sensor (LAPS) by means of the pulsed laser beam deposition (PLD) technique. The deposited layer worked as a Pb2+-ion-sensitive transducer, and the sensor showed Nernstian response with a sensitivity of 29±1mV\\/decade. The detection limit of the sensor for Pb2+-ions was 1×10?6mol\\/l. The response time does not exceed 50s

  2. Solid-state potentiometric CO2-sensor in thick film technology for breath analysis

    Microsoft Academic Search

    S. Wiegartner; G. Hagen; J. Kita; R. Moos; M. Seufert; E. Glaser; K. Grimmel; A. Bolz; C. Schmaus; A. Kiessig

    2011-01-01

    A solid-state potentiometric CO2-sensor of the type CO2, O2, Au, Li2CO3-BaCO3 | Nasicon | Na2Ti6O13-TiO2, Au, O2, CO2 was fully manufactured in planar thick-film technology. Due to an integrated screen-printed heater on the rear side, the sensor can be applied in a small tube for breath analysis, despite its high working temperature of 525 °C. The sensor is insensitive to

  3. Chemically fashioned ZnO nanowalls and their potential application for potentiometric cholesterol biosensor

    NASA Astrophysics Data System (ADS)

    Israr, M. Q.; Sadaf, J. R.; Nur, O.; Willander, M.; Salman, S.; Danielsson, B.

    2011-06-01

    Chemically fashioned zinc oxide (ZnO) nanowalls on aluminum wire have been characterized and utilized to fabricate a potentiometric cholesterol biosensor by an electrostatic conjugation with cholesterol oxidase. The sensitivity, specificity, reusability, and stability of the conjugated surface of ZnO nanowalls with thickness of ˜80 nm have been investigated over a wide logarithmic concentrations of cholesterol electrolyte solution ranging from 1×10-6-1×10-3 M. The presented biosensor illustrates good linear sensitivity slope curve (˜53 mV/decade) corresponding to cholesterol concentrations along with rapid output response time of ˜5 s.

  4. Cationic ?-cyclodextrin polymer applied to a dual cyclodextrin polyelectrolyte multilayer system.

    PubMed

    Junthip, Jatupol; Tabary, Nicolas; Leclercq, Laurent; Martel, Bernard

    2015-08-01

    A polyelectrolyte multilayer film (PEM) based on cationic and anionic ?-cyclodextrin polyelectrolytes was coated onto a textile substrate for future drug delivery purposes. We firstly synthesized a novel cationic ?-cyclodextrin polymer (polyEPG-CD) by crosslinking ?-cyclodextrin (?CD) with epichlorohydrin (EP) under basic conditions, in the presence of glycidyltrimetrylammonium chloride (GTMAC) as cationizing group. The influence of preparation conditions has been investigated in order to preferably obtain a water soluble fraction whose charge density and molecular weights were optimal for the layer-by-layer (LbL) deposition process. The different cationic cyclodextrin polymers obtained were characterized by FTIR, NMR, colloidal titration, conductimetry, thermogravimetric analysis and size exclusion chromatography. Besides, the counterpart polyelectrolyte was a ?-cyclodextrin polymer crosslinked with citric acid, polyCTR-CD, whose synthesis and characterization have been previously reported. Finally we realized the Layer by Layer (LbL) build-up of the PEM coating onto the textile support, using the dip coating method, by alternatively soaking it in cationic polyEPG-CD and anionic polyCTR-CD solutions. This multilayer self-assembly was monitored by SEM, gravimetry and OWLS in function of both polyelectrolytes concentrations and ratios. Solutions parameters such as pH, ionic strenght were also discussed. PMID:25933534

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

    USGS Publications Warehouse

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

    2005-01-01

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

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

    USGS Publications Warehouse

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

    1990-01-01

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

  7. The difference between the potentiometric surfaces of the Aquia Aquifer, September 1982 and September 2003 in southern Maryland

    USGS Publications Warehouse

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

    2005-01-01

    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 2003. The map, based on water level measurements in 56 wells, shows that the potentiometric surface during the 21-year period declined from zero in the northernmost part of the study area, which is the outcrop of the aquifer, to 108 feet at Lexington Park. Lexington Park is near the southeasternmost part of the study area and approaches the downdip boundary of the aquifer.

  8. The formation constants of ionomycin with divalent cations in 80% methanol/water.

    PubMed

    Stiles, M K; Craig, M E; Gunnell, S L; Pfeiffer, D R; Taylor, R W

    1991-05-01

    The protonation constants and complex formation constants of ionomycin have been determined in 80% methanol/water (w/w) at 25.0 degrees C and mu = 0.050 (tetraethylammonium perchlorate). Potentiometric and spectrometric titration techniques give the following values for the mixed-mode protonation constants of ionomycin: log KH1 = 11.94 +/- 0.02 and log KH2 = 6.80 +/- 0.03. Comparison of these values with those for model compounds indicates that KH1 and KH2 refer to equilibria involving the beta-diketone and carboxylic acid moieties, respectively. Titrations of ionomycin with metal ion at fixed values of pH produced changes in the UV-visual absorbance spectra which were analyzed to give conditional complex formation constants, KMI'. The pH dependence of the values of KMI' indicated that 1:1 divalent metal ion-ionomycin (MI) complexes and protonated MHI+ complexes were formed in the pH range studied. The values of log KMI ranged from 5.30 +/- 0.11 for Sr2+ to 10.25 +/- 0.03 for Ni2+. The selectivity pattern and relative affinities (in parentheses) for the formation of the species MI are as follows: Ni2+ (2000) greater than Zn2+ (600) greater than CO2+ (440) greater than Mn2+ (47) greater than Mg2+ (1.00) greater than Ca2+ (0.21) greater than Sr2+ (0.022). Logarithmic values of KMHI, for the reaction MI + H+ in equilibrium MHI+, ranged from 5.9 (Ni2+) to 8.4 (Sr2+). Calculations using the values of the equilibrium constants determined indicate that an appreciable fraction of the complexed ionophore exists as the protonated complex, MHI+, in the pH range of 6.5-8.5. PMID:1850743

  9. Circular dichroism-inhibitor titrations of arsanilazotyrosine-248 carboxypeptidase A.

    PubMed

    Johansen, J T; Klyosov, A A; Vallee, B L

    1976-01-27

    Coupling of carboxypeptidase with diazotized arsanilic acid specifically modifies a single tyrosyl residue. Yet, owing to the fact that the resultant azoTyr-248 can form an intramolecular chelate with zinc, two different circular dichroism probes result: azoTyr-248 itself and the azoTyr-248-Zn chelate. Both are environmentally sensitive and, characteristically, each can signal the same or different perturbations, as is apparent from circular dichroic spectra. This dual probe function greatly magnifies the scope of these chromophores in mapping the topography of the active center with respect to sites of interaction of inhibitors (or substrates). Titration of the azoenzyme with a series of synthetic, competitive inhibitors, e.g., L-benzylsuccinate, L-phenyllactate, and L-Phe, and with the pseudosubstrate, Gly-L-Tyr, in turn generates characteristic circular dichroic spectra. Their analysis yields a single binding constant for each of these agents, one molecule of each binding to the active center. Mixed inhibitions, as seen with beta-phenylpropionate and phenylacetate, resolved previously into competitive and noncompetitive components, are characterized by different spectral effects. Two molecules of these agents bind to the enzyme, consistent with both thermodynamic and enzymatic studies. The interactions leading to competitive and noncompetitive inhibition, respectively, can be recognized and assigned, based on the manner in which the extrema at 340 and 420 nm, reflecting azoTyr-248, and the negative 510-nm circular dichroism band, typical of its chelate with zinc, are affected and on the pH dependence of spectral and kinetic data. Certai4 noncompetitive inhibitors and modifiers induce yet other spectral features. Each probe is very sensitive to changes in its particular active center environment, though both can be relatively insensitive to inhibitors interacting at a distance from the active center. PMID:1247518

  10. An isoperibol calorimeter for the investigation of biochemical kinetics and isothermal titration calorimetry

    E-print Network

    Amadi, Ovid Charles

    2007-01-01

    Isothermal titration calorimetry is a technique used to measure the enthalpy change associated with a molecular binding interaction. From these data, the binding constant for the reaction can be determined. In the scope ...

  11. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10 ml. Reagents 1. Preparation of...

  12. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10 ml. Reagents 1. Preparation of...

  13. 40 CFR Appendix A to Part 425 - Potassium Ferricyanide Titration Method

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10 ml. Reagents 1. Preparation of...

  14. Impedimetric and potentiometric investigation of a sulfate anion-selective electrode: experiment and simulation.

    PubMed

    Mazloum-Ardakani, Mohammad; Manshadi, Abdolhosein Dehghan; Bagherzadeh, Mojtaba; Kargar, Hadi

    2012-03-20

    A new anion-selective polyvinyl chloride (PVC) membrane electrode based on {6,6'-diethoxy-2,2'-[2,2-dimethylpropane-1,3-diylbis(nitrilomethylidyne)]diphenolato}nickel(II)monohydrate as a carrier for the sulfate anion is reported. In this work, a new strategy for optimizing membrane components by electrochemical impedance spectroscopy (EIS) is presented. The performance of this electrode was investigated using potentiometric and EIS techniques. The potentiometric results indicated that the prepared electrode had a Nernstian slope of -28.9 ± 0.1 mV in a linear concentrations range of 1.0 × 10(-6) to 3.0 × 10(-1) M, a detection limit of 6.3 × 10(-7) M, an applied pH range of 4.0-9.0, and a response time of less than 15 s; while using the EIS technique, the linear concentrations range was 1.0 × 10(-9) to 1.0 × 10(-1) M and the pH range increased to 4.0-10.0. Finally, the impedance spectra were simulated using the Maple 13 software. A comparison of the experimental data and information obtained from the simulation confirmed the accuracy of the impedance measurement of this electrode. PMID:22288440

  15. Dual aptamer-immobilized surfaces for improved affinity through multiple target binding in potentiometric thrombin biosensing.

    PubMed

    Goda, Tatsuro; Higashi, Daiki; Matsumoto, Akira; Hoshi, Toru; Sawaguchi, Takashi; Miyahara, Yuji

    2015-11-15

    We developed a label-free and reagent-less potentiometric biosensor with improved affinity for thrombin. Two different oligomeric DNA aptamers that can recognize different epitopes in thrombin were introduced in parallel or serial manners on the sensing surface to capture the target via multiple contacts as found in many biological systems. The spacer and linker in the aptamer probes were optimized for exerting the best performance in molecular recognition. To gain the specificity of the sensor to the target, an antifouling molecule, sulfobeaine-3-undecanethiol (SB), was introduced on the sensor to form a self-assembled monolayer (SAM). Surface characterization revealed that the aptamer probe density was comparable to the distance of the two epitopes in thrombin, while the backfilling SB SAM was tightly aligned on the surface to resist nonspecific adsorption. The apparent binding parameters were obtained by thrombin sensing in potentiometry using the 1:1 Langmuir adsorption model, showing the improved dissociation constants (Kd) with the limit of detection of 5.5nM on the dual aptamer-immobilized surfaces compared with single aptamer-immobilized ones. A fine control of spacer and linker length in the aptamer ligand was essential to realize the multivalent binding of thrombin on the sensor surface. The findings reported herein are effective for improving the sensitivity of potentiometric biosensor in an affordable way towards detection of tiny amount of biomolecules. PMID:26067329

  16. Application of nanostructured TCNQ to potentiometric ion-selective K(+) and Na(+) electrodes.

    PubMed

    Paczosa-Bator, Beata; Pi?k, Magdalena; Piech, Robert

    2015-02-01

    A new type of potentiometric solid-state ion-selective electrode (SS-ISE) has been fabricated with an intermediate layer made of 7,7,8,8-tetracyanoquinodimethane (TCNQ) or its ion-radical salts and an ionophore-based ion-selective membrane. To show the influence of the TCNQ layer on electrode selectivity, sodium- and potassium-sensitive membranes were applied. A good Nernstian response with a slope of 59.24 mV/dec in the range from 10(-6.5) to 10(-1) M KCl and 58.68 mV/dec (10(-6) to 10(-1) M NaCl) was observed. The influence of an interfacial water film was assessed by an aqueous-layer test performed during potentiometric measurements. The stability of the electrical potential of the new solid-contact electrodes was tested by performing current-reversal chronopotentiometry, and the capacitance of the electrodes is 132 ?F or 154 ?F for K(+) and Na(+) solid-contact electrodes. These properties confirmed the analytical applicability of TCNQ-based SC-ISEs and should allow the development of a new solid-state ion sensor group. PMID:25551547

  17. 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. PMID:22514137

  18. New molecularly-imprinted polymer for carnitine and its application as ionophore in potentiometric selective membranes.

    PubMed

    Moret, Joséphine; Moreira, Felismina T C; Almeida, Sofia A A; Sales, M Goreti F

    2014-10-01

    Carnitine (CRT) is a biological metabolite found in urine that contributes in assessingseveral disease conditions, including cancer. Novel quick screening procedures for CRT are therefore fundamental. This work proposes a novel potentiometric device where molecularly imprinted polymers (MIPs) were used as ionophores. The host-tailored sites were imprinted on a polymeric network assembled by radical polymerization of methacrylic acid (MAA) and trimethylpropane trimethacrylate (TRIM). Non-imprinted polymers (NIPs) were produced as control by removing the template from the reaction media. The selective membrane was prepared by dispersing MIP or NIP particles in plasticizer and poly(vinyl chloride), PVC, and casting this mixture over a solid contact support made of graphite. The composition of the selective membrane was investigated with regard to kind/amount of sensory material (MIP or NIP), and the need for a lipophilic additive. Overall, MIP sensors with additive exhibited the best performance, with near-Nernstian response down to ~1×10(-4)mol L(-1), at pH5, and a detection limit of ~8×10(-5)mol L(-1). Suitable selectivity was found for all membranes, assessed by the matched potential method against some of the most common species in urine (urea, sodium, creatinine, sulfate, fructose and hemoglobin). CRT selective membranes including MIP materials were applied successfully to the potentiometric determination of CRT in urine samples. PMID:25175239

  19. Potentiometric Surface of the Lower 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 Lower 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 69 wells. The highest measured water level was 108 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 measured ground-water levels declined to 87 feet below sea level at Severndale, 39 feet below sea level at Arnold, and 43 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 measured were as low as 191 feet below sea level at Waldorf, 131 feet below sea level at LaPlata, 115 feet below sea level at Indian Head, and 86 feet below sea level at the Morgantown power plant.

  20. Geochemical Modeling of Reactions and Partitioning of Trace Metals and Radionuclides during Titration of Contaminated Acidic Sediments

    SciTech Connect

    Zhang, Fan [ORNL; Parker, Jack C. [University of Tennessee, Knoxville (UTK); Luo, Wensui [ORNL; Spalding, Brian Patrick [ORNL; Brooks, Scott C [ORNL; Watson, David B [ORNL; Jardine, Philip M [ORNL; Gu, Baohua [ORNL

    2008-01-01

    Many geochemical reactions that control aqueous metal concentrations are directly affected by solution pH. However, changes in solution pH are strongly buffered by various aqueous phase and solid phase precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior of the soil-solution system is thus critical to predict metal transport under variable pH conditions. This study was undertaken to develop a practical generic geochemical modeling approach to predict aqueous and solid phase concentrations of metals and anions during conditions of acid or base additions. The method of Spalding and Spalding was utilized to model soil buffer capacity and pH-dependent cation exchange capacity by treating aquifer solids as a polyprotic acid. To simulate the dynamic and pH-dependent anion exchange capacity, the aquifer solids were simultaneously treated as a polyprotic base controlled by mineral precipitation/dissolution reactions. An equilibrium reaction model that describes aqueous complexation, precipitation, sorption and soil buffering with pH-dependent ion exchange was developed using HydroGeoChem v5.0 (HGC5). Comparison of model results with experimental titration data of pH, Al, Ca, Mg, Sr, Mn, Ni, Co, and SO{sub 4}{sup 2-} for contaminated sediments indicated close agreement, suggesting that the model could potentially be used to predict the acid-base behavior of the sediment-solution system under variable pH conditions.

  1. Expenditures Associated with Dose Titration At Initiation of Therapy in Patients With Major Depressive Disorder

    PubMed Central

    Camacho, Fabian; Kong, Meg C.; Sheehan, David V.; Balkrishnan, Rajesh

    2010-01-01

    Objective. Although selective serotonin reuptake inhibitors (SSRIs) are considered cost-effective medications for patients with major depressive disorder (MDD), significant dosage adjustments are often necessary when treatment is initiated. Our study was conducted to examine whether dose titration for SSRIs at initiation of therapy was associated with a greater use of health care resources and higher costs. Study Design. A retrospective database analysis was conducted. Methods. A nationally representative cohort of individuals with MDD was identified in a large managed care claims database between January 1, 2004, and December 31, 2006. A study-specific titration algorithm was used to identify patients who underwent dose titration, compared with those who did not, within the first eight weeks of initiating SSRI therapy. We calculated propensity scores and identified a 1:1 matched cohort of titration versus non-titration patients. We used univariate and multivariate statistical tests to compare the mean number of therapeutic days, health care service utilization, and expenditures between the two groups during the first eight weeks (56 days) of treatment and six months (180 days) after treatment began. Results. Over the first eight weeks, the titration cohort had a 32% decrease in the adjusted mean number of therapeutic days (38 vs. 56, respectively; P < 0.001), a 50% increase in depression-related outpatient visits (1.8 vs. 1.2; P < 0.001), a 38% increase in depression-related outpatient costs ($137 vs. $81; P ? 0.001), an increase in antidepressant pharmacy costs ($139 vs. $61; P < 0.001), and a 64% increase in psychiatric visits (0.69 vs. 0.42; P = 0.001), compared with the matched non-titration cohort. These differences were consistent among individual SSRI groups as well as during the six-month period. Conclusion. Patients undergoing dose titration of SSRIs at the beginning of therapy consumed more medical resources and spent more days receiving a subtherapeutic dose than a comparable control group without dose titration. Differences in the utilization of resources were consistent with increased patient monitoring in the titration group; however, the added benefit of titration could not be assessed with this database. PMID:20844695

  2. Pincher ferrocene-derived cation carboxylate ion pairs in aqueous DMSO.

    PubMed

    Beck, Christie L; Berg, Stephen A; Winter, Arthur H

    2013-09-21

    Pincher cationic ferrocene hosts for carboxylate ion guests were synthesized and the binding constants were determined by NMR or UV-Vis titrations. These (di)cationic hosts form tight complexes with benzoate or acetate even in competitive aqueous DMSO solvent. A bis(acylguanidinium) ferrocene dication achieves a remarkable Ka of ~10(6) M(-1) to acetate in 9 : 1 DMSO-H2O and a Ka of 850 M(-1) in neat D2O, one of the highest association constants known for a carboxylate complex exploiting only electrostatic interactions in neat water. DFT computations of the binding enthalpy are in good agreement with the experimentally determined association constants. The ferrocene backbone used in these pincher complexes may prove to be a useful semi-flexible scaffold for redox detectable/switchable self-assemblies in aqueous solutions. PMID:23896645

  3. Potentiometric surface of the Upper Floridan aquifer, west-central Florida, May 2005

    USGS Publications Warehouse

    Ortiz, A.G.; Blanchard, R.A.

    2006-01-01

    The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing freshwater are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is a highly productive aquifer and supplies more than 10 times the amount of water pumped from either the surficial aquifer system or the intermediate aquifer system in most of the study area (Duerr and others, 1988). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2005. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in a tightly cased well that taps a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 67.27 inches for west-central Florida (from June 2004 through May 2005) was 14.20 inches above the historical cumulative average of 53.07 inches (Southwest Florida Water Management District (SWFWMD), 2005). The above average precipitation is attributed to the active hurrican season for Florida in 2004. Historical cumulative averages are calculated from regional rainfall summary reports (1915 to the most recent completed calendar year) and are updated monthly by the SWFWMD. This report, prepared by the U.S. Geological Survey (USGS) in cooperation with the SWFWMD, is part of a semiannual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the USGS during May 23-27, 2005. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the SWFWMD boundary by the USGS office in Altamonte Springs, Florida (Kinnaman, 2006). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition. Water levels in about 19 percent of the wells measured in May 2005 were lower than the May 2004 water levels (Blanchard and others, 2004). Data from 409 wells indicate that the May 2005 water levels ranged from about 5 feet below to about 18 feet above the May 2004 water levels (fig. 1). The largest water-level declines occurred in southwestern Hernando County, northeastern Hillsborough County, and parts of Hillsborough, Sumter, and Sarasota Counties. The largest water-level rises occurred in southeastern Hillsborough County, eastern Manatee County, and western Hardee County (fig. 1). Water levels in about 95 percent of the wells measured in May 2005 were lower than the September 2004 water levels (Blanchard and Seidenfeld, 2005). Data from 405 wells indicate that the May 2005 water levels ranged from about 22 feet below to 14 feet above the September 2004 water levels. The largest water-level decline was in east-central Manatee County and the largest water-level rise was in central Sarasota County.

  4. Potentiometric Surface of the Upper Floridan Aquifer, West-Central Florida, May 2006

    USGS Publications Warehouse

    Ortiz, A.G.

    2007-01-01

    Introduction Hydrologic Conditions in West-Central Florida The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by the middle confining unit. The middle confining unit and the Lower Floridan aquifer in west-central Florida generally contain highly mineralized water. The water-bearing units containing fresh water are herein referred to as the Upper Floridan aquifer. The Upper Floridan aquifer is the principal source of water in the Southwest Florida Water Management District and is used for major public supply, domestic use, irrigation, and brackish water desalination in coastal communities (Southwest Florida Water Management District, 2000). This map report shows the potentiometric surface of the Upper Floridan aquifer measured in May 2006. The potentiometric surface is an imaginary surface connecting points of equal altitude to which water will rise in tightly-cased wells that tap a confined aquifer system (Lohman, 1979). This map represents water-level conditions near the end of the dry season, when ground-water levels usually are at an annual low and withdrawals for agricultural use typically are high. The cumulative average rainfall of 50.23 inches for west-central Florida (from June 2005 through May 2006) was 2.82 inches below the historical cumulative average of 53.05 inches (Southwest Florida Water Management District, 2006). Historical cumulative averages are calculated from regional rainfall summary reports (1915 to most recent complete calendar year) and are updated monthly by the Southwest Florida Water Management District. This report, prepared by the U.S. Geological Survey in cooperation with the Southwest Florida Water Management District, is part of a semi-annual series of Upper Floridan aquifer potentiometric-surface map reports for west-central Florida. Potentiometric-surface maps have been prepared for January 1964, May 1969, May 1971, May 1973, May 1974, and for each May and September since 1975. Water-level data are collected in May and September each year to show the approximate annual low and high water-level conditions, respectively. Most of the water-level data for this map were collected by the U.S. Geological Survey during the period May 15-19, 2006. Supplemental water-level data were collected by other agencies and companies. A corresponding potentiometric-surface map was prepared for areas east and north of the Southwest Florida Water Management District boundary by the U.S. Geological Survey office in Altamonte Springs, Florida (Kinnaman, 2006). Most water-level measurements were made during a 5-day period; therefore, measurements do not represent a 'snapshot' of conditions at a specific time, nor do they necessarily coincide with the seasonal low water-level condition. Water-Level Changes Water levels in about 95 percent of the wells measured in May 2006 were lower than the May 2005 water levels (Ortiz and Blanchard, 2006). May 2006 water levels in 403 wells ranged from about 26 feet below to about 6 feet above May 2005 water levels (fig. 1). Significant water level declines occurred in eastern Manatee County, southwestern Polk County, southeastern Hillsborough County, and in all of Hardee County. The largest water level declines occurred in southwestern Hardee County. The largest water level rises occurred in south-central Pasco County, northeastern Levy County, northwestern Marion County, and along the gulf coast from Pasco County to Citrus County (fig. 1). Water levels in about 96 percent of the wells measured in May 2006 were lower than the September 2005 water levels (Ortiz, 2006). May 2006 water levels in 397 wells ranged from about 31 feet below to 3 feet above the September 2005 water levels. The largest water level decline was in west-central Hardee County and the largest rise in water levels was in south-central Pasco County.

  5. Unusual properties of crocodilian ovomacroglobulin shown in its methylamine treatment and sulfhydryl titration

    SciTech Connect

    Arakawa, H.; Osada, T.; Ikai, A.

    1986-02-01

    The inhibitory activity of chicken and crocodilian ovomacroglobulins against trypsin was measured before and after their incubation with methylamine. The result for crocodilian ovomacroglobulin showed that methylamine treatment destroyed half of its activity, in unique contrast to human alpha 2-macroglobulin and chicken ovomacroglobulin for which methylamine either destroys the inhibitory activity of the former completely or does not affect that of the latter at all. Free sulfhydryl groups of chicken and crocodilian ovomacroglobulins were titrated with 5,5'-dithiobis(2-nitrobenzoic acid) before and after incubation with trypsin. Prior to the incubation with trypsin the chicken and crocodilian proteins respectively had 0 and 1 titratable sulfhydryl per molecule of Mr 720,000. After treatment with trypsin the crocodilian protein had 3.5-4 titratable sulfhydryls, whereas there were no titratable sulfhydryls in the chicken protein. After denaturation of the crocodilian protein in sodium dodecyl sulfate at 100 degrees C the number of titratable sulfhydryls was 4. Chicken ovomacroglobulin again did not have an appreciable number of titratable sulfhydryls under similar denaturing conditions. Incubation of crocodilian protein with (14C)methylamine showed an incorporation of at least 2 mol of methylamine per molecule. The result indicated the presence of three intramolecular thiol ester bonds in crocodilian ovomacroglobulin with differential stability against external perturbations.

  6. Cation–cation interactions and cation exchange in a series of isostructural framework uranyl tungstates

    SciTech Connect

    Balboni, Enrica [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Burns, Peter C., E-mail: pburns@nd.edu [Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556 (United States)

    2014-05-01

    The isotypical compounds (UO{sub 2}){sub 3}(WO{sub 6})(H{sub 2}O){sub 5} (1), Ag(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3} (2), K(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 4} (3), Rb(UO{sub 2}){sub 3}(WO{sub 6})(OH)(H{sub 2}O){sub 3.5} (4), and Cs(UO{sub 2}){sub 3}(WO{sub 6})OH(H{sub 2}O){sub 3} (5) were synthesized, characterized, and their structures determined. Each crystallizes in space group Cc. (1): a=12.979 (3), b=10.238 (2), c=11.302 (2), ?=102.044 (2); (2): a=13.148 (2), b=9.520 (1), c=11.083 (2), ?=101.568 (2); (3): a=13.111 (8), b=9.930 (6), c=11.242 (7), ?=101.024 (7); (4): a=12.940 (2), b=10.231 (2), c=11.259(2), ?=102.205 (2); (5): a=12.983 (3), b=10.191 (3), c=11.263 (4), ?=101.661 (4). Compounds 1–5 are a framework of uranyl and tungsten polyhedra containing cation–cation interactions. The framework has three symmetrically distinct U(VI) cations, one tungsten, sixteen to eighteen oxygen atoms, and in 2–5, one monovalent cation. Each atom occupies a general position. Each U(VI) cation is present as a typical (UO{sub 2}){sup 2+} uranyl ion in an overall pentagonal bipyramidal coordination environment. Each pentagonal bipyramid shares two equatorial edges with two other pentagonal bipyramids, forming a trimer. Trimers are connected into chains by edge-sharing with WO{sub 6} octahedra. Chains are linked through cation–cation interactions between two symmetrically independent uranyl ions. This yields a remarkably complex system of intersecting channels that extend along [0 0 1] and [?1 1 0]. The cation exchange properties of 2 and 3 were characterized at room temperature and at 140 °C. - Graphical abstract: Chains of uranium and tungsten polyhedra are connected into a three dimensional framework by cation–cation interactions occurring between two symmetrically independent uranyl pentagonal bipyramids. Monovalent cations present in channels within the structure can be exchanged by room temperature or mild hydrothermal treatments. The framework of these compounds is robust to cation exchange and heat. (yellow polyhedra=uranium pentagonal bipyramids; blue polyhedra=tungsten octahedral, purple balls=K; yellow balls=Na; grey balls=Tl). - Highlights: • Five isostructural uranyl tungstates compounds were synthesized hydrothermally. • The structures consist of a chains of uranium and tungstate polyhedral. • Chains are connected into a framework by cation–cation interactions. • Cation exchange does not alter the structural integrity of the compounds. • Cation exchange was successful at room temperature and mild hydrothermal conditions.

  7. High-resolution ultrasonic spectroscopy study of interactions between hyaluronan and cationic surfactants.

    PubMed

    Kargerová, Andrea; Peka?, Miloslav

    2014-10-14

    Interactions in a cationic surfactant-hyaluronan system in water and in sodium chloride solution were investigated by high-resolution ultrasonic spectroscopy at 25 °C. Two alkyltrimethylammonium bromide surfactants of different chain lengths (tetradecyl and hexadecyl) were used; hyaluronan molecular weight ranged from 10 to 1750 kDa. Two main parameters-ultrasonic velocity and attenuation-were measured in the titration regime. Up to six different regions could be identified in the velocity titration profiles in water in a narrow interval of surfactant concentration. These regions differed primarily in the compressibility of structures formed in the system. The number of detected transitions was higher for the tetradecyl surfactant; therefore, the increased length of the hydrophobic chain simplified the details of the structure-forming behavior. The measurement of attenuation was much less sensitive and detected only the formation of microheterogeneous structures or visible phase separates. The richness of the titration profiles was depressed in salt solution, where essentially only two principal regions were observed. On the other hand, the effect of hyaluronan molecular weight on the positions of boundaries between regions was more significant in the presence of salt. Besides electrostatic interactions, hydrophobic interactions are also relevant for determining the behavior of hyaluronan-surfactant systems and the properties of formed complexes (aggregates). PMID:25247835

  8. Historical potentiometric surface of the Edwards-Trinity aquifer system and contiguous hydraulically connected units, west-central Texas

    USGS Publications Warehouse

    Bush, Peter W.; Ardis, Ann F.; Wynn, Kirby H.

    1993-01-01

    The historical potentiometric-surface map of the Edwards-Trinity aquifer system and contiguous hydraulically connected units is based on 1,789 water-level (or pressure-head) measurements made in wells between December 1915 and November 1969. The mapped data reflect a wide range of rainfall conditions. On the basis of interpretations of historical climatologic data by the National Oceanic and Atmospheric Administration, near- normal rainfall conditions preceded 55 percent of the measurements. Moderately dry conditions preceded 20 percent of the measurements; moderately wet conditions preceded 22 percent of the measurements; very dry conditions preceded less than 1 percent; and very wet conditions preceded 3 percent. The historical potentiometric-surface map represents general predevelopment conditions because negligible ground-water withdrawals existed in most areas when the water-level measurements used to construct the map were made. However, in Bexar, Reeves, Pecos, Reagan, and Upton Counties, early withdrawals caused declines in water levels that are reflected in water-level features shown on the map. Topographic relief and stream or spring drainage are two major factors affecting the configuration of the historical potentiometric surface. The strong influence of stream or spring drainage on the potentiometric surface shows that the regional direction of ground-water movement is largely dictated by the locations of major discharge feature. a

  9. A novel light-addressable potentiometric sensors set-up with LCD projector as scanning light source

    Microsoft Academic Search

    Yen-Heng Lin; Anirban Das; Kai-Siang Ho; Chao-Sung Lai

    2011-01-01

    In a typical set-up of light-addressable potentiometric sensor (LAPS), the individual sensing parts of the photosensitive semiconductor chip are addressed by modulated light beam such as laser beam. Although the laser can be executed with precision, the relative equipment is complex and expensive. In this work, a novel approach of utilizing Liquid Crystal Display (LCD) projector as a programmable modulated

  10. Determination of cadmium(II) and zinc(II) in olive oils by derivative potentiometric stripping analysis

    Microsoft Academic Search

    F Lo Coco; L Ceccon; L Ciraolo; V Novelli

    2003-01-01

    A method for the determination of cadmium(II) and zinc(II) in olive oils by derivative potentiometric stripping analysis after dry ashing of the sample is described. The metal ions were concentrated as their amalgams on the glassy carbon working electrode that was previously coated with a thin mercury film and then stripped by a suitable oxidant. Potential and time data were

  11. Determination of lead (II) and cadmium (II) in hard and soft wheat by derivative potentiometric stripping analysis

    Microsoft Academic Search

    F Lo Coco; P Monotti; V Fiecchi; L Ceccon

    2000-01-01

    A method for the determination of lead (II) and cadmium (II) in hard and soft wheat by derivative potentiometric stripping analysis is described. The metal ions were concentrated as their amalgams on the glassy carbon surface of a working electrode that was previously coated with a thin mercury film, and then stripped by a suitable oxidant. Potential and time data

  12. Simulated effects of ground-water development on potentiometric surface of the Floridan Aquifer, west-central Florida

    USGS Publications Warehouse

    Wilson, William Edward; Gerhart, James M.

    1980-01-01

    A digital model of two-dimensional ground-water flow was used to predict changes in the potentiometric surface of the Floridan aquifer, 1976-2000, in a 5,938-square-mile area of west-central Florida. In 1975, ground water withdrawn from the Floridan aquifer for irrigation, phosphate mines, other industries, and municipal supplies averaged about 649 million gallons per day. Rates are projected to increase to about 840 million gallons per day by 2000. The model was calibrated under steady-state and transient conditions. Input parameters included transmissivity and storage coefficient of the Floridan aquifer; thickness, vertical hydraulic conductivity, and storage coefficient of the upper confining bed; altitudes of the water table and potentiometric surface; and ground-water withdrawals. Simulation of May 1976 to May 2000, using projected combined pumping rates for municipal supplies, irrigation, and industry (including existing and proposed phosphate mines), resulted in a rise in the potentiometric surface of about 10 feet in Polk County, and a decline of about 35 feet in parts of Manatee and Hardee Counties. The lowest predicted potentiometric level was about 30 feet below sea level. Predicted declines for November 1976 to October 2000 were generally 5 to 10 feet less than those for May 1976 to May 2000. (USGS)

  13. Simulated effects of ground-water development on potentiometric surface of the Floridan Aquifer, west-central Florida

    USGS Publications Warehouse

    Wilson, W.E.; Gerhart, J.M.

    1982-01-01

    A digital model of two-dimensional ground-water flow was used to predict changes in the potentiometric surface of the Floridan aquifer, 1976 to 2000, in a 5,938-square-mile area of west-central Florida. In 1975, ground water withdrawn from the Floridan aquifer for irrigation, phosphate mines, other industries, and municipal supplies averaged about 649 million gallons per day. Rates are projected to increase to about 840 million gallons per day by 2000. The model was calibrated under steady-state and transient conditions. Input parameters included transmissivity and storage coefficient of the Floridan aquifer; thickness, vertical hydraulic conductivity, and storage coefficient of the upper confining bed; altitudes of the water table and potentiometric surface; and ground-water withdrawals. Simulation of May 1976 to May 2000, using projected combined pumping rates for municipal supplies, irrigation, and industry (including existing and proposed phosphate mines), resulted in a rise in the potentiometric surface of about 10 feet in Polk County, and a decline of about 35 feet in parts of Manatee and Hardee Counties. The lowest predicted potentiometric level was about 30 feet below sea level. Predicted declines for November 1976 to October 2000 were generally 5 to 10 feet less than those for May 1976 to May 2000. (USGS)

  14. 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) the land surface elevation of the region. Examples from the midcontinent of the United States, specifically Kansas, Oklahoma, and parts of adjacent states illustrate the process.

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

    USGS Publications Warehouse

    Wasson, B.E.

    1980-01-01

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

  16. A study of the effect of magnetized water on enzyme activities by potentiometric enzyme electrode method.

    PubMed

    Ma, Y L; Ren, H; Ren, S; Zhen, E K; Hao, G; Zhao, Y W

    1992-01-01

    A very promising glutamate decarboxylase electrode, which has linear response range of 5.6 x 10(-5)-1.2 x 10(-2) mol/L. Nernstian slope of 50 mV/decade, detection limit of 3.2 x 10(-5) mol/L and response time less than 3 min, has been designed to observe and evaluate quantitatively the effect of magnetized water on enzyme activities by potentiometric enzyme electrode method. It was found that the activity of glutamate decarboxylase can increase by 30% in magnetized water. The mechanism of increased enzyme activity was discussed in the present paper. Such a new finding will probably lead to some new explanations for the physiological and biological mechanism of the effect of magnetized water on living organisms, thus providing a new approach to the study of the effect of magnetized water. PMID:1289564

  17. 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

  18. Potentiometric Surface of the Aquia Aquifer in Southern Maryland, September 2002

    USGS Publications Warehouse

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

    2003-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2002. The map is based on water-level measurements in 94 wells. The highest measured water level was 38 feet above sea level near the northern boundary and outcrop area of the aquifer in the central part of Anne Arundel County, and was below sea level just south of this area and in the remainder of the study area. The hydraulic gradient increased southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. Another cone of depression occurred in northern Calvert County due to pumpage at and near Chesapeake Beach and North Beach. The water level measured in this area has declined to 55 feet below sea level. The lowest water level measured was 169 feet below sea level at the center of a cone of depression at Lexington Park.

  19. Potentiometric surface of the Aquia Aquifer in southern Maryland, September 2003

    USGS Publications Warehouse

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

    2005-01-01

    This report presents a map showing the potentiometric surface of the Aquia aquifer in the Aquia Formation of Paleocene age in Southern Maryland during September 2003. The map is based on water-level measurements in 91 wells. The highest measured water level was 40 feet above sea level near the northern boundary and outcrop area of the aquifer in the central part of Anne Arundel County, and was below sea level just south of this area and in the remainder of the study area. The hydraulic gradient increased southeastward toward an extensive cone of depression around well fields at Lexington Park and Solomons Island. Another cone of depression occurred in northern Calvert County due to pumpage at and near North Beach and Chesapeake Beach. The water level measured in this area has declined to 48 feet below sea level. The lowest water level measured was 156 feet below sea level at the center of a cone of depression at Lexington Park.

  20. Generalized potentiometric surface of aquifers of Pleistocene age, Southern Louisiana, 1980

    USGS Publications Warehouse

    Martin, Angel, Jr.; Whiteman, Charles D., Jr.

    1985-01-01

    A map of potentiometric surface defines generalized water levels for 1980 in the Pleistocene aquifers of southern Louisiana. The map was prepared as part of the Western Gulf Coast Regional Aquifer-System Analysis study. The Pleistocene deposits in southern Louisiana consist of alternating beds of sand, gravel, silt, and clay deposited under fluvial, deltaic, and near-short marine conditions. The aquifers are mainly under artesian conditions and the regional flow direction is primarily southward. Areally definable cones of depression result from heavy pumpage in the Baton Rouge, Lake Charles, and New Orleans metropolitan areas and in the rice irrigation area of southwestern Louisiana. Where water levels differ vertically within the aquifer, the lowest water levels in the vertical section were used because these levels represented the thickest and most heavily pumped unit in the aquifer. The map represents regional water levels in the Pleistocene aquifers, and is not intended to show localized variations near pumping centers. (USGS)

  1. Potentiometric surfaces of the coastal plain aquifers of South Carolina prior to development

    USGS Publications Warehouse

    Aucott, Walter R.; Speiran, Gary K.

    1985-01-01

    Characteristics of the Coastal Plains aquifers of South Carolina are being studied as a part of the Regional Aquifer Systems Analysis program of the U.S. Geological Survey. A framework has been developed to best represent the hydrology of the Coastal Plain aquifers by dividing them into a system of five aquifers. This framework includes a surficial aquifer consisting of coastal terrace deposits, a limestone and stratigraphically equivalent sand aquifer of Eocene age, and three sand aquifers of Cretaceous age. This report presents a general description of the aquifer framework, potentiometric maps for the aquifers of Eocene and Cretaceous age prior to development, and a general description of the flow system prior to development. In the lower Coastal Plain, flow in the aquifer of Eocene age is generally perpendicular to the coast but is almost parallel to the coast in the aquifers of Cretaceous age. (USGS)

  2. Forsterite surface composition in aqueous solutions: a combined potentiometric, electrokinetic, and spectroscopic approach

    Microsoft Academic Search

    Oleg S. Pokrovsky; Jacques Schott

    2000-01-01

    Surfaces of natural and synthetic forsterite (Fo91 and Fo100) in aqueous solutions at 25°C were investigated using surface titrations in batch and limited residence time reactors, column filtration experiments, electrokinetic measurements (streaming potential and electrophoresis techniques), Diffuse Reflectance Infrared Spectroscopy (DRIFT), and X-ray Photoelectron Spectroscopy (XPS). At pH < 9, a Mg-depleted, Si-rich layer (<20 Å thick) is formed on

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

    PubMed

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

    2011-01-01

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

  4. Ascorbic Acid as a Standard for Iodometric Titrations. An Analytical Experiment for General Chemistry

    NASA Astrophysics Data System (ADS)

    Silva, Cesar R.; Simoni, Jose A.; Collins, Carol H.; Volpe, Pedro L. O.

    1999-10-01

    Ascorbic acid is suggested as the weighable compound for the standardization of iodine solutions in an analytical experiment in general chemistry. The experiment involves an iodometric titration in which iodine reacts with ascorbic acid, oxidizing it to dehydroascorbic acid. The redox titration endpoint is determined by the first iodine excess that is complexed with starch, giving a deep blue-violet color. The results of the titration of iodine solution using ascorbic acid as a calibration standard were compared with the results acquired by the classic method using a standardized solution of sodium thiosulfate. The standardization of the iodine solution using ascorbic acid was accurate and precise, with the advantages of saving time and avoiding mistakes due to solution preparation. The colorless ascorbic acid solution gives a very clear and sharp titration end point with starch. It was shown by thermogravimetric analysis that ascorbic acid can be dried at 393 K for 2 h without decomposition. This experiment allows general chemistry students to perform an iodometric titration during a single laboratory period, determining with precision the content of vitamin C in pharmaceutical formulations.

  5. Methods for the determination of cyclopropenoid fatty acids. II. A stepwise hydrogen bromide titration method for cyclopropenid and epoxy derivatives

    Microsoft Academic Search

    J. A. Harris; F. C. Magne; E. L. Skau

    1963-01-01

    A rapid titration method is described for the quantitative determination of both cyclopropenoid and epoxy fatty acid derivatives\\u000a in mixtures. It was found that epoxy compounds can be titrated selectively with Durbetaki reagent at 3C without interference\\u000a from cyclopropenoid derivatives. Cyclopropenoid derivatives can be titrated much more rapidly to a much sharper end point\\u000a a 55C that at room temperature.

  6. Cation-cation interactions and cation exchange in a series of isostructural framework uranyl tungstates

    NASA Astrophysics Data System (ADS)

    Balboni, Enrica; Burns, Peter C.

    2014-05-01

    The isotypical compounds (UO2)3(WO6)(H2O)5 (1), Ag(UO2)3(WO6)(OH)(H2O)3 (2), K(UO2)3(WO6)OH(H2O)4 (3), Rb(UO2)3(WO6)(OH)(H2O)3.5 (4), and Cs(UO2)3(WO6)OH(H2O)3 (5) were synthesized, characterized, and their structures determined. Each crystallizes in space group Cc. (1): a=12.979 (3), b=10.238 (2), c=11.302 (2), ?=102.044 (2); (2): a=13.148 (2), b=9.520 (1), c=11.083 (2), ?=101.568 (2); (3): a=13.111 (8), b=9.930 (6), c=11.242 (7), ?=101.024 (7); (4): a=12.940 (2), b=10.231 (2), c=11.259(2), ?=102.205 (2); (5): a=12.983 (3), b=10.191 (3), c=11.263 (4), ?=101.661 (4). Compounds 1-5 are a framework of uranyl and tungsten polyhedra containing cation-cation interactions. The framework has three symmetrically distinct U(VI) cations, one tungsten, sixteen to eighteen oxygen atoms, and in 2-5, one monovalent cation. Each atom occupies a general position. Each U(VI) cation is present as a typical (UO2)2+ uranyl ion in an overall pentagonal bipyramidal coordination environment. Each pentagonal bipyramid shares two equatorial edges with two other pentagonal bipyramids, forming a trimer. Trimers are connected into chains by edge-sharing with WO6 octahedra. Chains are linked through cation-cation interactions between two symmetrically independent uranyl ions. This yields a remarkably complex system of intersecting channels that extend along [0 0 1] and [-1 1 0]. The cation exchange properties of 2 and 3 were characterized at room temperature and at 140 °C.

  7. Cation ordering in complex oxides

    Microsoft Academic Search

    Peter K. Davies

    1999-01-01

    Several recent papers have addressed the fundamental aspects of the stability and kinetics of ordering in complex oxides, and investigated systems where the properties are mediated by the degree of order. Cation ordering reactions have been shown to induce large alterations in the dielectric, ferroelectric, magnetic, and electronic response of many complex oxides. The majority of the cited publications focus

  8. Cationic surfactants based on ferrocene

    SciTech Connect

    Pankratov, V.A.; Kucherova, N.L.; Abramzon, A.A.

    1988-07-20

    Quaternary ammonium salts based on ferrocene were synthesized and their surface active properties were studied as potential cationic surfactants and for uses including antiknock compounds. The salts were halide and nitrate derivatives of dimethylferrocenylmethylammonium and were prepared by aminomethylation of ferrocene. Chemical reaction yields, melting points, surface tension isotherms, and other characteristics were assessed.

  9. Ion-ion correlation and charge reversal at titrating solid interfaces

    E-print Network

    Christophe Labbez; Bo Jonsson; Michal Skarba; Michal Borkovec

    2008-12-01

    Confronting grand canonical titration Monte Carlo simulations (MC) with recently published titration and charge reversal (CR) experiments on silica surfaces by Dove et al. and van der Heyden it et al, we show that ion-ion correlations quantitatively explain why divalent counterions strongly promote surface charge which, in turn, eventually causes a charge reversal (CR). Titration and CR results from simulations and experiments are in excellent agreement without any fitting parameters. This is the first unambiguous evidence that ion-ion correlations are instrumental in the creation of highly charged surfaces and responsible for their CR. Finally, we show that charge correlations result in "anomalous" charge regulation in strongly coupled conditions in qualitative desagreement with its classical treatment.

  10. Survey of the year 2004: literature on applications of isothermal titration calorimetry.

    PubMed

    Ababou, Abdessamad; Ladbury, John E

    2006-01-01

    The market for commercially available isothermal titration calorimeters continues to grow as new applications and methodologies are developed. Concomitantly the number of users (and abusers) increases dramatically, resulting in a steady increase in the number of publications in which isothermal titration calorimetry (ITC) plays a role. In the present review, we will focus on areas where ITC is making a significant contribution and will highlight some interesting applications of the technique. This overview of papers published in 2004 also discusses current issues of interest in the development of ITC as a tool of choice in the determination of the thermodynamics of molecular recognition and interaction. PMID:16220545

  11. Denitrifying activity measurements using an anoxic titration (pHstat) bioassay.

    PubMed

    Foxon, K M; Brouckaert, C J; Rozzi, A

    2002-01-01

    An anoxic titrimetric test was investigated for measuring denitrifying activity in an activated sludge system. The method measures the amount of acid that is required to maintain the pH set-point value in a batch denitrification experiment. An iterative algorithm was implemented to extract nitrate uptake rate (NUR) data from titration data, since the accumulation and depletion (stripping) of reaction by-products HCO3- and CO2 affects the direct calculation of denitrifying activity from titration data. This method was performed using an automatic pH-stat acid dosing system, and the data were analysed using the simulation software package, AQUASIM. PMID:12448471

  12. Arene-thioether mixed complex radical cations

    SciTech Connect

    Werst, D.W.

    1994-03-01

    Studies of radiolytically generated radical cations in aromatic hydrocarbon solvents have led to the first direct characterization of monomeric thioether radical cations in liquid solution. Observation of these very reactive chemical intermediates is made possible by the great sensitivity of fluorescence-detected magnetic resonance (FDMR) and by solvent stabilization of the thioether radical cations via electron donation. Monomeric thioether radical cations in arene solvents such as toluene exist as arene-thioether mixed complex radical cations -- the first {pi}-lone pair mixed complex radical cations ever observed. Such orbital interactions are of fundamental importance for open-shell intermediates as they have consequences for both electronic structure and reactivity. Thioether radical cations provide a valuable test system to probe the chemical influence of orbital interactions that are generic to all {pi}-type and heteroatom-containing organic radical cations, and magnetic resonance provides unsurpassed structural resolution for condensed-phase paramagnetic intermediates.

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

    USGS Publications Warehouse

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

    2009-01-01

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

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

    USGS Publications Warehouse

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

    1987-01-01

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

  15. Highly Selective Potentiometric Membrane Sensor for Hg(II) Based on Bis(Benzoyl Acetone) Diethylene Triamine

    Microsoft Academic Search

    Ali A. Ensafi; S. Meghdadi; Alireza R. Allafchian

    2008-01-01

    A new ion selective PVC membrane sensor is described based on bis(benzoyl acetone) diethylene triamine as a potentiometric sensor for Hg2+ ions. The membrane having bis(benzoyl acetone) diethylene triamine as an electroactive material, sodium tetraphenyl phthalate (NaTPB), and dibutyl phthalate (DBP) as an anion excluder in PVC matrix in the percentage ratio 4.21:2.11:60.25:33.43 (Ionophore:NaTPB:DBP:PVC) (w\\/w) of exhibits a linear response

  16. Novel CeO2-based Screen-Printed Potentiometric Electrodes for pH monitoring S. Betelu1*

    E-print Network

    Boyer, Edmond

    1 Novel CeO2-based Screen-Printed Potentiometric Electrodes for pH monitoring S. Betelu1* , K) is a possible candidate for nuclear waste storage. This work investigates the applicability of CeO2-based oxides (CeO2, Ce0.8Sm0.2O2 and Ce0.8Zr0.2O2) for monitoring the pH of the COx pore water. The study

  17. Immobilization of Urease and Cholinesterase on the Surface of Semiconductor Transducer for the Development of Light-Addressable Potentiometric Sensors

    Microsoft Academic Search

    Ioulia G. Mourzina; Tatsuo Yoshinobu; Yuri E. Ermolenko; Yuri G. Vlasov; Michael J. Schöning; Hiroshi Iwasaki

    2004-01-01

    Various methods for the immobilization of urease and butyrylcholinesterase on the insulator surface of a laser-scanned semiconductor transducer (LSST) have been tested and compared for the development of an enzyme-based light-addressable potentiometric sensor (LAPS). The method of preparing photocurable membranes on LAPS is presented, and a new type of enzyme LAPS with photocurable polymeric enzyme membranes has been elaborated. It

  18. Use of a Light-Addressable Potentiometric Sensor for the Detection of Escherichia coliO157:H7

    Microsoft Academic Search

    Andrew G. Gehring; Deidre L. Patterson; Shu-I Tu

    1998-01-01

    We describe the development of an immunoligand assay (ILA) in conjunction with a light-addressable potentiometric sensor (LAPS) for the rapid detection ofEscherichia coliO157:H7 cells in buffered saline. The ILA protocol consists of “sandwiching” bacterial analyte between biotinylated and fluoresceinated antibodies, indirect enzyme labeling of the bacteria with urease-labeled anti-fluorescein antibody, and active capture of the immune complex at a biotinylated

  19. A Potentiometric and Spectroscopic Investigation of Copper(II)– and Zinc(II)–Orotate Complex Equilibria Under Physiological Conditions

    Microsoft Academic Search

    Brahim Hacht; Hassan Tayaa; Ahmed Benayad; Mostafa Mimouni

    2002-01-01

    A quantitative study of zinc(II) and copper(II) complex formation with orotic acid has been performed under physiological conditions (37°C; 0.15 mol-dm-3 NaCl) using the glass electrode potentiometric technique. Several species have been identified within the pH range 2–10 for the metal-to-ligand concentration ratios investigated. Three mononuclear complexes, ML, ML2, and ML2H-1, have been characterized with both metals. In addition, the

  20. Cationic electrodepositable coating composition comprising lignin

    DOEpatents

    Fenn, David; Bowman, Mark P; Zawacky, Steven R; Van Buskirk, Ellor J; Kamarchik, Peter

    2013-07-30

    A cationic electrodepositable coating composition is disclosed. The present invention in directed to a cationic electrodepositable coating composition comprising a lignin-containing cationic salt resin, that comprises (A) the reaction product of: lignin, an amine, and a carbonyl compound; (B) the reaction product of lignin, epichlorohydrin, and an amine; or (C) combinations thereof.

  1. Preparation and Utilization of Cationized Sawdust

    Microsoft Academic Search

    A. Hashem; A. A. Aly; A. S. Aly

    2006-01-01

    Glycidyl trimethyl ammonium acetate (GTMAA) was prepared. Factors affecting the cationization of sawdust with GTMAA in presence of sodium hydroxide were investigated. These factors include sodium hydroxide\\/GTMAA molar ratio, liquor ratio, reaction duration, and temperature. The extent of cationization was traced by estimating the nitrogen content of the cationized sawdust, and its structural features were confirmed by IR analysis. The

  2. Weak protein-cationic co-ion interactions addressed by X-ray crystallography and mass spectrometry.

    PubMed

    Bénas, Philippe; Auzeil, Nicolas; Legrand, Laurent; Brachet, Franck; Regazzetti, Anne; Riès-Kautt, Madeleine

    2014-08-01

    The adsorption of Rb(+), Cs(+), Mn(2+), Co(2+) and Yb(3+) onto the positively charged hen egg-white lysozyme (HEWL) has been investigated by solving 13 X-ray structures of HEWL crystallized with their chlorides and by applying electrospray ionization mass spectrometry (ESI-MS) first to dissolved protein crystals and then to the protein in buffered salt solutions. The number of bound cations follows the order Cs(+) < Mn(2+) ? Co(2+) < Yb(3+) at 293?K. HEWL binds less Rb(+) (qtot = 0.7) than Cs(+) (qtot = 3.9) at 100?K. Crystal flash-cooling drastically increases the binding of Cs(+), but poorly affects that of Yb(3+), suggesting different interactions. The addition of glycerol increases the number of bound Yb(3+) cations, but only slightly increases that of Rb(+). HEWL titrations with the same chlorides, followed by ESI-MS analysis, show that only about 10% of HEWL binds Cs(+) and about 40% binds 1-2 Yb(3+) cations, while the highest binding reaches 60-70% for protein binding 1-3 Mn(2+) or Co(2+) cations. The binding sites identified by X-ray crystallography show that the monovalent Rb(+) and Cs(+) preferentially bind to carbonyl groups, whereas the multivalent Mn(2+), Co(2+) and Yb(3+) interact with carboxylic groups. This work elucidates the basis of the effect of the Hofmeister cation series on protein solubility. PMID:25084340

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

    PubMed Central

    Ohura, Hiroki; Imato, Toshihiko

    2011-01-01

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

  4. Calorimetric study of cationic photopolymerization

    NASA Astrophysics Data System (ADS)

    Czajlik, I.; Hedvig, P.; Ille, A.; Dobó, J.

    1996-03-01

    The photopolymerization of penta-erythritol tetra-glycidyl ether (initiator Degacure KI-85) was studied by a du Pont 910 type DSC. From our experimental results the following conclusions can be drawn: (1) During the cationic polymerization reaction the lifetime of the initiating centers are long compared to the lifetime of free radicals in case of radical polymerization. (2) The rate of deactivation of the initiating centers increases with increasing temperature.

  5. Cation coordination in oxychloride glasses

    Microsoft Academic Search

    J. A. Johnson; D. Holland; J. Bland; C. E. Johnson; M. F. Thomas

    2003-01-01

    Glasses containing mixtures of cations and anions of nominal compositions [Sb2O3]x - [ZnCl2]1-x where x = 0.25, 0.50, 0.75, and 1.00, have been studied by means of neutron diffraction and Raman and Mössbauer spectroscopy. There is preferential bonding within the system with the absence of Sb-Cl bonds. Antimony is found to be threefold coordinated to oxygen, and zinc fourfold coordinated.

  6. Cation coordination in oxychloride glasses

    Microsoft Academic Search

    J A Johnson; D Holland; J Bland; C E Johnson; M F Thomas

    2003-01-01

    Glasses containing mixtures of cations and anions of nominal compositions [Sb2O3]x – [ZnCl2]1?x where x = 0.25, 0.50, 0.75, and 1.00, have been studied by means of neutron diffraction and Raman and Mössbauer spectroscopy. There is preferential bonding within the system with the absence of Sb–Cl bonds. Antimony is found to be threefold coordinated to oxygen, and zinc fourfold coordinated.

  7. Comparison of the Zeta Potential with the Diffuse Layer Potential from Charge Titration

    E-print Network

    Attard, Phil

    that no counterion binding occurs. For the metal oxides analyzed (titanium dioxide, aluminum oxide, and silicon) theory is used to compare charge titration and zeta potential data for several colloids. It is found dioxide) the two measurements can only be reconciled by postulating counterion binding or surface charge

  8. Polyelectrolyte Titration: Theory and Experiment Itamar Borukhov,*, David Andelman,,| Regis Borrega, Michel Cloitre, Ludwik Leibler, and

    E-print Network

    Andelman, David

    transition associated with polymer conformational changes. We argue that the specific shape of titration-Hu¨ckel-like charge-charge correlations as well as by correlations between dissociation sites along the polymer chain with experiments. In particular, the model explains the decrease of the pH at the plateau when the polymer

  9. Titration of high dose sedation is effective in severe tetanus: a case report

    Microsoft Academic Search

    Pan Chun; Huang Ying-Zi; Yang Yi; Qiu Hai-Bo

    2009-01-01

    INTRODUCTION: Tetanus is a fatal infectious disease. It could cause typical signs like pain, headache, stiffness, and spasms of facial muscles as well as trunk and skeletal muscles. The symptoms are risus sardonicus, trismus and opisthotonus. How to control the spasticity and rigidity of muscles is still a problem. Our object is to raise the feasibility of titration of high

  10. Titrating steroids on exhaled nitric oxide in children with asthma: a randomized controlled trial

    Microsoft Academic Search

    M. W. H. Pijnenburg; W. C. J. Hop; Jongste de J. C; E. M. Bakker

    2005-01-01

    RATIONALE: Corticosteroids are the antiinflammatory treatment of choice in asthma. Treatment guidelines are mainly symptom-driven but symptoms are not closely related to airway inflammation. The fraction of nitric oxide in exhaled air (FENO) is a marker of airway inflammation in asthma. OBJECTIVE: We evaluated whether titrating steroids on FENO improved asthma management in children. METHODS: Eighty-five children with atopic asthma,

  11. Exact Analysis of Competition Ligand Binding by Displacement Isothermal Titration Calorimetry

    Microsoft Academic Search

    Bent W. Sigurskjold

    2000-01-01

    A rigorous method for the least-squares nonlinear regression analysis of displacement isothermal titration calorimetric data is presented. The method can fit the binding isotherm of a ligand which is competitively inhibited in its binding by another bound ligand to a molecule with n identical and independent binding sites. There are no other assumptions for the method and no approximations. Analysis

  12. Avian influenza virus isolation, propagation and titration in embryonated chicken eggs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Avian influenza (AI) virus is usually isolated, propagated, and titrated in embryonated chickens eggs (ECE). Most any sample type can be accommodated for culture with appropriate processing. Isolation may also be accomplished in cell culture particularly if mammalian lineage isolates are suspected, ...

  13. Impairment and Deportment Responses to Different Methylphenidate Doses in Children With ADHD: The MTA Titration Trial

    Microsoft Academic Search

    LAURENCE L. GREENHILL; JAMES M. SWANSON; BENEDETTO VITIELLO; MARK DAVIES; WALTER CLEVENGER; MIN WU; L. EUGENE ARNOLD; HOWARD B. ABIKOFF; OSCAR G. BUKSTEIN; C. KEITH CONNERS; GLEN R. ELLIOTT; LILY HECHTMAN; STEPHEN P. HINSHAW; BETSY HOZA; PETER S. JENSEN; HELENA C. KRAEMER; JOHN S. MARCH; JEFFREY H. NEWCORN; JOANNE B. SEVERE; KAREN WELLS; TIMOTHY WIGAL

    2001-01-01

    ObjectiveResults of the NIMH Collaborative Multisite Multimodal Treatment Study of Children With Attention-Deficit\\/Hyperactivity Disorder (MTA) were analyzed to determine whether a double-blind, placebo-controlled methylphenidate (MPH) titration trial identified the best MPH dose for each child with attention-deficit\\/hyperactivity disorder (ADHD).

  14. Subsite binding energies of an exo-polygalacturonase using isothermal titration calorimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Thermodynamic parameters for binding of a series of galacturonic acid oligomers to an exo-polygalacturonase, RPG16 from Rhizopus oryzae, were determined by isothermal titration calorimetry. Binding of oligomers varying in chain length from two to five galacturonic acid residues is an exothermic proc...

  15. The Simulation of an Oxidation-Reduction Titration Curve with Computer Algebra

    ERIC Educational Resources Information Center

    Whiteley, Richard V., Jr.

    2015-01-01

    Although the simulation of an oxidation/reduction titration curve is an important exercise in an undergraduate course in quantitative analysis, that exercise is frequently simplified to accommodate computational limitations. With the use of readily available computer algebra systems, however, such curves for complicated systems can be generated…

  16. Coulometric Titration of Ethylenediaminetetraacetate (EDTA) with Spectrophotometric Endpoint Detection: An Experiment for the Instrumental Analysis Laboratory

    ERIC Educational Resources Information Center

    Williams, Kathryn R.; Young, Vaneica Y.; Killian, Benjamin J.

    2011-01-01

    Ethylenediaminetetraacetate (EDTA) is commonly used as an anticoagulant in blood-collection procedures. In this experiment for the instrumental analysis laboratory, students determine the quantity of EDTA in commercial collection tubes by coulometric titration with electrolytically generated Cu[superscript 2+]. The endpoint is detected…

  17. Performing Titration Analyses for Water Quality. Module 17. Vocational Education Training in Environmental Health Sciences.

    ERIC Educational Resources Information Center

    Consumer Dynamics Inc., Rockville, MD.

    This module, one of 25 on vocational education training for careers in environmental health occupations, contains self-instructional materials on performing titration analysis for water quality. Following guidelines for students and instructors and an introduction that explains what the student will learn are three lessons: (1) naming each part of…

  18. The titration curve of insulin in the presence of various bivalent metal ions

    PubMed Central

    Graae, John

    1968-01-01

    1. Titration curves of insulin in the presence and absence of various metal ions are reported. 2. The difference in base consumption with and without the metal ions is compared with calculated curves. 3. These experiments suggest that in dilute solutions Zn2+ and Cu2+ ions are bound to ?-amino groups. PMID:5637362

  19. RAINBOW TROUT COMPLEMENT FIXATION USED FOR TITRATION OF ANTIBODIES AGAINST SEVERAL PATHOGENS

    E-print Network

    Paris-Sud XI, Université de

    RAINBOW TROUT COMPLEMENT FIXATION USED FOR TITRATION OF ANTIBODIES AGAINST SEVERAL PATHOGENS M pathogens. In contrast, there is very little information con- cerning complement fixation. However, the existence of complement in the serum of the eel (Anguilla anguilla) and the tench, ( Tinca tinca

  20. DNA heats up: Energetics of genome ejection from phage revealed by isothermal titration calorimetry.

    E-print Network

    1 DNA heats up: Energetics of genome ejection from phage revealed by isothermal titration-stranded DNA into bacteria upon receptor binding in an essentially spontaneous way. This downhill thermodynamic process from the intact virion toward the empty viral capsid plus released DNA is made possible

  1. AMPEROMETRIC TITRATION OF VANADIUM AND URANIUM WITH TITANIUM(III) SALTS

    Microsoft Academic Search

    Z. A. Gallai; N. M. Sheina

    1961-01-01

    An amperometric method was develeped for the titration of vanadium(IV) ; with titanrum(III) in pure salts and in the prescence of chromium, manganese, and ; titanium. Conditions were found for- the amperometric determination of uranium ; using titanrrun(III) in the presence of titanum(IV) up to the U: Ti ratio 1:100. ; (auth);

  2. Comprehensive Formulation of Titration Curves for Complex AcidBase Systems and Its Analytical Implications

    Microsoft Academic Search

    Agustin G. Asuero; Tadeusz Micha?owski

    2011-01-01

    This article provides extensive and exhaustive mathematical description of titration curves related to acid-base systems with mixtures of mono- and polyprotic acids and their salts and bases involved. The related curves are presented in compact forms facilitating further operations made for particular needs. Some derivative properties of the curves, such as buffer capacity and inflection points, are also discussed. The

  3. Charge Density Quantification of Polyelectrolyte Polysaccharides by Conductometric Titration: An Analytical Chemistry Experiment

    ERIC Educational Resources Information Center

    Farris, Stefano; Mora, Luigi; Capretti, Giorgio; Piergiovanni, Luciano

    2012-01-01

    An easy analytical method for determination of the charge density of polyelectrolytes, including polysaccharides and other biopolymers, is presented. The basic principles of conductometric titration, which is used in the pulp and paper industry as well as in colloid and interface science, were adapted to quantify the charge densities of a…

  4. Single-experiment displacement assay for quantifying high-affinity binding by isothermal titration calorimetry.

    PubMed

    Krainer, Georg; Keller, Sandro

    2015-04-01

    Isothermal titration calorimetry (ITC) is the gold standard for dissecting the thermodynamics of a biomolecular binding process within a single experiment. However, reliable determination of the dissociation constant (KD) from a single titration is typically limited to the range 100 ?M>KD>1 nM. Interactions characterized by a lower KD can be assessed indirectly by so-called competition or displacement assays, provided that a suitable competitive ligand is available whose KD falls within the directly accessible window. However, this protocol is limited by the fact that it necessitates at least two titrations to characterize one high-affinity inhibitor, resulting in considerable consumption of both sample material and time. Here, we introduce a fast and efficient ITC displacement assay that allows for the simultaneous characterization of both a high-affinity ligand and a moderate-affinity ligand competing for the same binding site on a receptor within a single experiment. The protocol is based on a titration of the high-affinity ligand into a solution containing the moderate-affinity ligand bound to the receptor present in excess. The resulting biphasic binding isotherm enables accurate and precise determination of KD values and binding enthalpies (?H) of both ligands. We discuss the theoretical background underlying the approach, demonstrate its practical application to metal ion chelation, explore its potential and limitations with the aid of simulations and statistical analyses, and elaborate on potential applications to protein-inhibitor interactions. PMID:25461813

  5. Anal. Chem. 1982, 54, 2117-2120 2117 validity of the ASV titration method. We are confident that

    E-print Network

    Zare, Richard N.

    Anal. Chem. 1982, 54, 2117-2120 2117 validity of the ASV titration method. We are confident,the validity of the assumptions has not been demonstrated for any pure ligand nor for natural water organics-titration method to yield an accurate p' value. In gen- eral, the validity of these assumptions can be tested

  6. The Quantitative Resolution of a Mixture of Group II Metal Ions by Thermometric Titration with EDTA. An Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Smith, Robert L.; Popham, Ronald E.

    1983-01-01

    Presents an experiment in thermometric titration used in an analytic chemistry-chemical instrumentation course, consisting of two titrations, one a mixture of calcium and magnesium, the other of calcium, magnesium, and barium ions. Provides equipment and solutions list/specifications, graphs, and discussion of results. (JM)

  7. Gaseous protein cations are amphoteric

    SciTech Connect

    Stephenson, J.L. Jr.; McLuckey, S.A. [Oak Ridge National Lab., TN (United States)] [Oak Ridge National Lab., TN (United States)

    1997-02-19

    Singly- and multiply-protonated ubiquitin molecules are found to react with iodide anions, and certain other anions, by attachment of the anion, in competition with proton transfer to the anion. The resulting adduct ions are relatively weakly bound and dissociate upon collisional activation by loss of the neutral acid derived from the anion. Adduct ions that behave similarly can also be formed via ion/molecule reactions involving the neutral acid. The ion/molecule reaction phenomenology, however, stands in contrast with that expected based on the reaction site(s) being charged. Reaction rates increase inversely with charge state and the total number of neutral molecules that add to the protein cations increases inversely with cation charge. These observations are inconsistent with the formation of proton-bound clusters but are fully consistent with the formation of ion pairs or dipole/dipole bonding involving the neutral acid and neutral basic sites in the protein. The ion/ion reactions can be interpreted on the basis of conjugate acid/base chemistry in which the anion, which is a strong gaseous base, reacts with a protonated site, which is a strong gaseous acid. Adduct ions can also be formed via ion/molecule reaction which, on the basis of microscopic reversibility, implies that the neutral acid interacts with neutral basic sites on the protein cation. 26 refs., 10 figs., 1 tab.

  8. Interactions of cationic trimeric, gemini and monomeric surfactants with trianionic curcumin in aqueous solution.

    PubMed

    Wang, Meina; Wu, Chunxian; Tang, Yongqiang; Fan, Yaxun; Han, Yuchun; Wang, Yilin

    2014-05-21

    Interactions of trianionic curcumin (Cur(3-)) with a series of cationic surfactants, monomeric surfactant dodecyl trimethylammonium bromide (DTAB), dimeric surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD), have been investigated in aqueous solution of pH 13.0. Surface tension and spectral measurements indicate that the cationic surfactants display a similar surfactant concentration dependent interaction process with Cur(3-), involving three interaction stages. At first the three cationic surfactants electrostatically bind on Cur(3-) to form the surfactant-Cur(3-) complex. Then the bound and unbound cationic surfactants with Cur(3-) aggregate into surfactant-Cur(3-) mixed micelles through hydrophobic interactions above the critical micelle concentration of the surfactants (CMCC) in the presence of Cur(3-). Finally excess unbound surfactants self-assemble into micelles like those without Cur(3-). For all the three surfactants, the addition of Cur(3-) only decreases the critical micelle concentration of 12-6-12 but does not affect the critical micelle concentration of DTAB and DTAD. As the oligomeric degree of surfactants increases, the intermolecular interaction of the cationic surfactants with Cur(3-) increases and the surfactant amount needed for Cur(3-) encapsulation decreases. Compared with 12-6-12, either the weaker interaction of DTAB with Cur(3-) or stronger interaction of DTAD with Cur(3-) limits the stability or solubility of Cur(3-) in surfactant micelles. Therefore, gemini surfactant 12-6-12 is the best choice to effectively suppress Cur(3-) degradation at very low concentrations. Isothermal titration microcalorimetry, surface tension and (1)H NMR results reveal that 12-6-12 and Cur(3-) form a (12-6-12)2-Cur(3-) complex and start to form micelles at extremely decreased concentrations, where either 12-6-12 or Cur(3-) works as a bridge linkage and the resultant structure exhibits the characteristics of oligomeric surfactants. PMID:24647897

  9. Protofit: A program for determining surface protonation constants from titration data

    NASA Astrophysics Data System (ADS)

    Turner, Benjamin F.; Fein, Jeremy B.

    2006-11-01

    Determining the surface protonation behavior of natural adsorbents is essential to understand how they interact with their environments. ProtoFit is a tool for analysis of acid-base titration data and optimization of surface protonation models. The program offers a number of useful features including: (1) enables visualization of adsorbent buffering behavior; (2) uses an optimization approach independent of starting titration conditions or initial surface charge; (3) does not require an initial surface charge to be defined or to be treated as an optimizable parameter; (4) includes an error analysis intrinsically as part of the computational methods; and (5) generates simulated titration curves for comparison with observation. ProtoFit will typically be run through ProtoFit-GUI, a graphical user interface providing user-friendly control of model optimization, simulation, and data visualization. ProtoFit calculates an adsorbent proton buffering value as a function of pH from raw titration data (including pH and volume of acid or base added). The data is reduced to a form where the protons required to change the pH of the solution are subtracted out, leaving protons exchanged between solution and surface per unit mass of adsorbent as a function of pH. The buffering intensity function Qads* is calculated as the instantaneous slope of this reduced titration curve. Parameters for a surface complexation model are obtained by minimizing the sum of squares between the modeled (i.e. simulated) buffering intensity curve and the experimental data. The variance in the slope estimate, intrinsically produced as part of the Qads* calculation, can be used to weight the sum of squares calculation between the measured buffering intensity and a simulated curve. Effects of analytical error on data visualization and model optimization are discussed. Examples are provided of using ProtoFit for data visualization, model optimization, and model evaluation.

  10. Direct Sensing of Total Acidity by Chronopotentiometric Flash Titrations at Polymer Membrane Ion-Selective Electrodes

    PubMed Central

    Gemene, Kebede L.; Bakker, Eric

    2008-01-01

    Polymer membrane ion-selective electrodes containing lipophilic ionophores are traditionally interrogated by zero current potentiometry, which, ideally, gives information on the sample activity of ionic species. It is shown here that a discrete cathodic current pulse across an H+-selective polymeric membrane doped with the ionophore ETH 5294 may be used for the chronopotentiometric detection of pH in well buffered samples. However, a reduction in the buffer capacity leads to large deviations from the expected Nernstian response slope. This is explained by the local depletion of hydrogen ions at the sample-membrane interface as a result of the galvanostatically imposed ion flux in direction of the membrane. This depletion is found to be a function of the total acidity of the sample and can be directly monitored chronopotentiometrically in a flash titration experiment. The subsequent application of a baseline potential pulse reverses the extraction process of the current pulse, allowing one to interrogate the sample with minimal perturbation. In one protocol, total acidity is found to be proportional to the magnitude of applied current at the flash titration endpoint. More conveniently, the square root of the flash titration endpoint time observed at a fixed applied current is a linear function of the total acid concentration. This suggests that it is possible to perform rapid localized pH titrations at ion-selective electrodes without the need for volumetric titrimetry. The technique is explored here for acetic acid, MES and citric acid with promising results. Polymeric membrane electrodes on the basis of poly(vinyl chloride) plasticized with o-nitrophenyloctylether in a 1:2 mass ratio may be used for the detection of acids of up to ca. 1 mM concentration, with flash titration times on the order of a few seconds. Possible limitations of the technique are discussed, including variations of the acid diffusion coefficients and influence of electrical migration. PMID:18370399

  11. Resorcarene-based receptor: versatile behavior in its interaction with heavy and soft metal cations.

    PubMed

    Danil de Namor, Angela F; Chaaban, Jinane K; Piro, Oscar E; Castellano, Eduardo E

    2006-02-01

    Standard solution Gibbs energies, DeltasG degrees, of the resorcarene-based receptor 5,11,17,23-ethylthiomethylated calix[4]resorcarene, (characterized by 1H NMR and X-ray diffraction studies) in its monomeric state (established through partition experiments) in various solvents are for the first time reported in the area of resorcarene chemistry. Transfer Gibbs energies of from hexane (reference solvent) to other medium are calculated. Agreement between DeltatG degrees (referred to the pure solvents) and standard partition Gibbs energies, DeltapG degrees (solvent mutually saturated) is found. Cation-ligand interactions were investigated through 1H NMR (CD3CN and CD3OD) and conductometric titrations in acetonitrile and methanol. 1H NMR data revealed the sites of interaction of with the metal cation. The composition of the metal-ion complexes (Ag+ and Pb2+ in acetonitrile and Ag+ and Cu2+ in methanol) was established through conductometric titrations. Thus, complexes of 1:1 stoichiometry were formed between and Ag+ and Pb2+ in acetonitrile and Cu2+ in methanol. However, in moving from acetonitrile to methanol, the composition of the silver complex was altered. Thus, two metal cations are hosted by a unit of the ligand. As far as Cu2+ and in acetonitrile is concerned, conductance data suggest that metalates are formed in which up to four units of Cu2+ are taken up per unit of resorcarene. The contrasting behavior of with Cu2+ in acetonitrile relative to methanol is discussed. As far as mercury (II) is concerned, the unusual jump in conductance observed in the titration of Hg2+ with in acetonitrile and methanol after the formation of a multicharged complex (undefined composition) is attributed to the presence of highly charged smaller units (higher mobility) resulting from the departure of pendant arms from the resorcarene backbone. Isolation of these species followed by X-ray diffraction studies corroborated this statement. The thermodynamic characterization of metal-ion complexes of Ag+ and Pb2+ in acetonitrile and Cu2+ and Ag+ in methanol is reported. Final conclusions are given. PMID:16471836

  12. Safety and tolerability of different titration rates of retigabine (ezogabine) in patients with partial-onset seizures.

    PubMed

    Biton, Victor; Gil-Nagel, Antonio; Brodie, Martin J; Derossett, Sarah E; Nohria, Virinder

    2013-11-01

    Retigabine (RTG; international nonproprietary name)/ezogabine (EZG; US adopted name) is an antiepileptic drug (AED) that prolongs neuronal voltage-gated potassium-channel KCNQ2-5 (Kv 7.2-7.5) opening. This double-blind study evaluated different RTG/EZG dose-titration rates. Patients (N=73) with partial-onset seizures receiving concomitant AEDs were randomized to one of three titration groups, all of which were initiated at RTG/EZG 300mg/day divided into three equal doses. Fast-, medium-, and slow-titration groups received dose increments of 150mg/day every 2, 4, and 7 days, respectively, achieving the target dose of 1200mg/day after 13, 25, and 43 days, respectively. Safety assessments were performed throughout. Discontinuation rates due to treatment-emergent adverse events (TEAEs) were numerically higher in the fast- (10/23) and medium- (7/22) titration groups than in the slow-titration group (3/23) but statistical significance was achieved only for the high-titration group compared with the low-titration group (p=0.024). Stratified analysis, with concomitant AEDs divided into enzyme inducers (carbamazepine, phenytoin, oxcarbazepine) or noninducers, showed that the risk of discontinuation due primarily to TEAEs was significantly higher in the fast- (p=0.010) but not in the medium-titration group (p=0.078) when compared with the slow-titration group. Overall, the slow-titration rate appeared to be best tolerated and was used in further efficacy and safety studies with RTG/EZG. PMID:24094693

  13. Development of potentiometric equipment for the identification of altered dry-cured hams: A preliminary study.

    PubMed

    Girón, Joel; Gil-Sánchez, Luís; García-Breijo, Eduardo; Jesús Pagán, M; Barat, José M; Grau, Raúl

    2015-08-01

    Microbiological contamination in dry-cured ham can occur in the early stages of the process, a large number of microorganisms involved in spoilage can produce alterations in the product. These include non-common odours, which are detected at the end of the process by a procedure called "cala", consisting of a sharp instrument punctured in every ham; this is smelled by an expert taster, who classifies hams as good and altered hams. An electronic device would be suitable for this process given the large amount of hams. The present research aims to develop objective equipment based on the potentiometry technique that identifies altered hams. A probe was developed, containing silver, nickel and copper electrodes, and was employed to classify altered and unaltered hams prior to classification by a tester. The results shown lower Ag and higher Cu potential values for altered hams. The differences in potentiometric response reveal a classification model, although further studies are required to obtain a reliable classification model. PMID:25839997

  14. Incorporating ?-cyclodextrin with ZnO nanorods: a potentiometric strategy for selectivity and detection of dopamine.

    PubMed

    Elhag, Sami; Ibupoto, Zafar Hussain; Nur, Omer; Willander, Magnus

    2013-01-01

    We describe a chemical sensor based on a simple synthesis of zinc oxide nanorods (ZNRs) for the detection of dopamine molecules by a potentiometric approach. The polar nature of dopamine leads to a change of surface charges on the ZNR surface via metal ligand bond formation which results in a measurable electrical signal. ZNRs were grown on a gold-coated glass substrate by a low temperature aqueous chemical growth (ACG) method. Polymeric membranes incorporating ?-cyclodextrin (?-CD) and potassium tetrakis (4-chlorophenyl) borate was immobilized on the ZNR surface. The fabricated electrodes were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The grown ZNRs were well aligned and exhibited good crystal quality. The present sensor system displays a stable potential response for the detection of dopamine in 10(-2) mol·L(-1) acetic acid/sodium acetate buffer solution at pH 5.45 within a wide concentration range of 1 × 10(-6) M(-1) × 10(-1) M, with sensitivity of 49 mV/decade. The electrode shows a good response time (less than 10 s) and excellent repeatability. This finding can contribute to routine analysis in laboratories studying the neuropharmacology of catecholamines. Moreover, the metal-ligand bonds can be further exploited to detect DA receptors, and for bio-imaging applications. PMID:24445413

  15. Novel and selective potentiometric membrane sensor for amiloride determination in pharmaceutical compounds and urine.

    PubMed

    Ensafi, Ali A; Allafchian, Ali R

    2008-08-01

    A new PVC membrane sensor is described as a potentiometric sensor for amiloride. The sensor having amiloride-sodium tetraphenyl phthalate (ion-pair) as an electroactive material and dibutyl phthalate (DBP) as an anion excluder in PVC matrix in the percentage ratio of 4:66:30 (ion-pair: DBP:PVC) (w/w). The membrane sensor exhibits suitable response to amiloride in a concentration range of 1.0 x 10(-2) to 1.0 x 10(-6)mol L(-1) with a limit of detection of 9.9 x 10(-7)mol L(-1). The slope of the system was -54.3+/-1.0 mV decade(-1) over pH range of 2.0-7.0. Selectivity coefficients for amiloride relative to a numbers of potential interfering substances were investigated. The sensor was highly selective for amiloride over a large number of similar compounds. The sensor showing a fast response time of 6s and was used over a period of 2 months with a good reproducibility. The sensor was successfully applied to determination of amiloride in pharmaceutical samples with satisfactory results. PMID:18448303

  16. A polyaniline based ultrasensitive potentiometric immunosensor for cardiac troponin complex detection.

    PubMed

    Zhang, Qi; Prabhu, Alok; San, Avdar; Al-Sharab, Jafar F; Levon, Kalle

    2015-10-15

    An ultrasensitive immunosensor based on potentiometric ELISA for the detection of a cardiac biomarker, troponin I-T-C (Tn I-T-C) complex, was developed. The sensor fabrication involves typical sandwich ELISA procedures, while the final signal readout was achieved using open circuit potentiometry (OCP). Glassy carbon (GC) working electrodes were first coated with emulsion-polymerized polyaniline/dinonylnaphthalenesulfonic acid (PANI/DNNSA) and the coated surface was utilized as a transducer layer on which sandwich ELISA incubation steps were performed. An enzymatic reaction between o-phenylenediamine (OPD) and hydrogen peroxide (H2O2) was catalyzed by horseradish peroxidase (HRP) labeled on the secondary antibodies. The polymer transducer charged state was mediated through electron (e(-)) and charge transfers between the transducer and charged species generated by the same enzymatic reaction. Such a change in the polymer transducer led to potential variations against an Ag/AgCl reference electrode as a function of Tn I-T-C complex concentration during incubations. The sequence of OPD and H2O2 additions, electrochemical properties of the PANI/DNNSA layer and non-specific binding prevention were all crucial factors for the assay performance. Under optimized conditions, the assay has a low limit of detection (LOD) (<5pg/mL or 56fM), a wide dynamic range (>6 orders of magnitude), high repeatability (coefficient of variance <8% for all concentrations higher than 5pg/mL) and a short detection time (<10min). PMID:25966464

  17. 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 ) ?g/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

  18. Potentiometric CO2 Sensor Using Li+ Ion Conducting Li3PO4 Thin Film Electrolyte

    PubMed Central

    Noh, Whyo Sub; Satyanarayana, L.; Park, Jin Seong

    2005-01-01

    Li+ ion conducting Li3PO4 thin film electrolytes with thickness 300nm, 650nm and 1.2?m were deposited on Al2O3 substrate at room temperature by thermal evaporation method. Reference and sensing electrodes were printed on Au interfaces by conventional screen printing technique. The overall dimension of the sensor was 3 × 3 mm and of electrodes were 1 × 1.5 mm each. The fabricated solid state potentiometric CO2 sensors of type: CO2, O2, Au, Li2TiO3-TiO2| Li3PO4 |Li2CO3, Au, CO2, O2 have been investigated for CO2 sensing properties. The electromotive force (emf) and ?emf/dec values of the sensors are dependent on the thickness of the electrolyte film. 1.2?m thickness deposited sensor has shown good sensing behavior than the sensors with less thickness. The ?emf values of the sensor are linearly increased up to 460°C operating temperature and became stable above 460°C. Between 460-500°C temperatures region the sensor has reached an equilibrium state and the experimentally obtained ?emf values are about 80% of the theoretically calculated values. A Nernst's slope of -61mV/decade has been obtained between 250 to 5000 ppm of CO2 concentration at 500°C temperature. The sensor is suitable for ease of mass production in view of its miniaturization and cost effectiveness after some further improvement.

  19. Neurochip based on light-addressable potentiometric sensor with wavelet transform de-noising.

    PubMed

    Liu, Qing-Jun; Ye, Wei-Wei; Yu, Hui; Hu, Ning; Du, Li-Ping; Wang, Ping

    2010-05-01

    Neurochip based on light-addressable potentiometric sensor (LAPS), whose sensing elements are excitable cells, can monitor electrophysiological properties of cultured neuron networks with cellular signals well analyzed. Here we report a kind of neurochip with rat pheochromocytoma (PC12) cells hybrid with LAPS and a method of de-noising signals based on wavelet transform. Cells were cultured on LAPS for several days to form networks, and we then used LAPS system to detect the extracellular potentials with signals de-noised according to decomposition in the time-frequency space. The signal was decomposed into various scales, and coefficients were processed based on the properties of each layer. At last, signal was reconstructed based on the new coefficients. The results show that after de-noising, baseline drift is removed and signal-to-noise ratio is increased. It suggests that the neurochip of PC12 cells coupled to LAPS is stable and suitable for long-term and non-invasive measurement of cell electrophysiological properties with wavelet transform, taking advantage of its time-frequency localization analysis to reduce noise. PMID:20443210

  20. Neurochip based on light-addressable potentiometric sensor with wavelet transform de-noising*

    PubMed Central

    Liu, Qing-jun; Ye, Wei-wei; Yu, Hui; Hu, Ning; Du, Li-ping; Wang, Ping

    2010-01-01

    Neurochip based on light-addressable potentiometric sensor (LAPS), whose sensing elements are excitable cells, can monitor electrophysiological properties of cultured neuron networks with cellular signals well analyzed. Here we report a kind of neurochip with rat pheochromocytoma (PC12) cells hybrid with LAPS and a method of de-noising signals based on wavelet transform. Cells were cultured on LAPS for several days to form networks, and we then used LAPS system to detect the extracellular potentials with signals de-noised according to decomposition in the time-frequency space. The signal was decomposed into various scales, and coefficients were processed based on the properties of each layer. At last, signal was reconstructed based on the new coefficients. The results show that after de-noising, baseline drift is removed and signal-to-noise ratio is increased. It suggests that the neurochip of PC12 cells coupled to LAPS is stable and suitable for long-term and non-invasive measurement of cell electrophysiological properties with wavelet transform, taking advantage of its time-frequency localization analysis to reduce noise. PMID:20443210

  1. Generalized potentiometric surface of the Evangeline and equivalent aquifers in Louisiana, 1980

    USGS Publications Warehouse

    Martin, Angel, Jr.; Whiteman, Charles D., Jr.

    1985-01-01

    A generalized potentiometric-surface map defines the altitude of water levels for 1980 in wells in the Evangeline aquifer in southwestern Louisiana and stratigraphically equivalent aquifers in southeastern Louisiana. The Evangeline and equivalent aquifers increase in thickness from zero at the northern edge of the outcrop/subcrop belt to more than 2,000 feet along the southern limit of fresh water. The aquifers are recharged by rainfall on the overlying upland terrace deposits of south-central Louisiana, southeastern Louisiana, and southwestern Mississippi. The aquifers are under artesian conditions except locally in the recharge areas. The regional flow direction is primarily southward. Water levels in wells in the Evangeline aquifer are lowered by heavy pumping from the overlying Chicot aquifer in Evangeline and Acadia Parishes. Areally definable cones of depression result from pumpage from the Evangeline and equivalent aquifers in and near Baton Rouge, Eunice, and Ville Platte. Water levels may differ vertically within the aquifer near pumping centers. The map does not account for localized distortion of the regional flow pattern near these centers. (USGS)

  2. Competitive Ion Exchange Behavior on Oxides C. P. Schulthess* and D. L. Sparks

    E-print Network

    Sparks, Donald L.

    for modeling ion adsorption. The rmax values can be de- termined based on potentiometric titration data (Huang with this method is that the proton isotherms ob- tained by the traditional potentiometric titration methods

  3. Cation coordination in oxychloride glasses

    NASA Astrophysics Data System (ADS)

    Johnson, J. A.; Holland, D.; Bland, J.; Johnson, C. E.; Thomas, M. F.

    2003-02-01

    Glasses containing mixtures of cations and anions of nominal compositions [Sb2O3]x - [ZnCl2]1-x where x = 0.25, 0.50, 0.75, and 1.00, have been studied by means of neutron diffraction and Raman and Mössbauer spectroscopy. There is preferential bonding within the system with the absence of Sb-Cl bonds. Antimony is found to be threefold coordinated to oxygen, and zinc fourfold coordinated. The main contributing species are of the form [Sb(OSb)2(OZn)] and [Zn(ClZn)2(OSb)2].

  4. Entropic Effects and Slow Kinetics Revealed in Titrations of D2O-H2O Solutions with Different D/H Ratios

    E-print Network

    Jacob, Eshel Ben

    Entropic Effects and Slow Kinetics Revealed in Titrations of D2O-H2O Solutions with Different D for H2O, which cause a larger entropic cost for solvating molecules in D2O. Here we used isothermal titration calorimetry (ITC) to investigate the enthalpy of titration of D2O-H2O solutions with different D

  5. Cyclic Group 15 Radical Cations.

    PubMed

    Brückner, Angelika; Hinz, Alexander; Priebe, Jacqueline B; Schulz, Axel; Villinger, Alexander

    2015-06-15

    Singlet cyclo-1,3-dipnicta-2,4-diazane-1,3-diyls of the type [E(?-NTer)2 E] (2, E=P, As, Ter=2,6-dimesitylphenyl) can undergo a one-electron-oxidation utilizing silver salts of weakly coordinating anions such as [AgLn ][B(C6 F5 )4 ] (L=donor solvents) to afford the novel cyclic radical cations, [E(?-NTer)2 E](+.) (3(+.) ). When smaller and more basic anions were employed in the reaction, the anions were found to form covalent bonds to the radical centers yielding dipnictadiazanes, [FP(?-NTer)2 PF] (5) and [(CF3 CO2 )P(?-NTer)2 P(CF3 CO2 )] (6). A two-electron oxidation process, resulting in the formation of dications of the type [E(?-NTer)2 E](2+) , could not be observed. Computational and EPR data revealed that the spin density is almost completely localized at the two heavier pnictogen centers E of the former 1,3-dipnictadiazane-1,3-diyls. The bonding situation in the radical cations features a rare example of a transannular one-electron ? bond without having a ? bond. PMID:25960190

  6. Cationic starch: an effective flocculating agent

    Microsoft Academic Search

    S. Pal; D. Mal; R. P. Singh

    2005-01-01

    A series of cationic starches (Cat St) have been developed by incorporating a cationic moiety N-(3-Chloro-2-hydroxypropyl) trimethyl ammonium chloride (CHPTAC) onto the backbone of starch in presence of NaOH. The cationic starches are characterized by elemental analysis, FTIR spectroscopy and intrinsic viscosity measurement. The flocculation characteristics of these starches have been evaluated in 0.25wt% silica suspension by jar test. It

  7. Mechanism of Oligonucleotide Release from Cationic Liposomes

    Microsoft Academic Search

    Olivier Zelphati; Francis C. Szoka

    1996-01-01

    We propose a mechanism for oligonucleotide (ODN) release from cationic lipid complexes in cells that accounts for various observations on cationic lipid-nucleic acid-cell interactions. Fluorescent confocal microscopy of cells treated with rhodamine-labeled cationic liposome\\/fluorescein-labeled ODN (F-ODN) complexes show the F-ODN separates from the lipid after internalization and enters the nucleus leaving the fluorescent lipid in cytoplasmic structures. ODN displacement from

  8. Flocculation of microalgae using cationic starch

    Microsoft Academic Search

    Dries Vandamme; Imogen Foubert; Boudewijn Meesschaert; Koenraad Muylaert

    2010-01-01

    Due to their small size and low concentration in the culture medium, cost-efficient harvesting of microalgae is a major challenge.\\u000a We evaluated the potential of cationic starch as a flocculant for harvesting microalgae using jar test experiments. Cationic\\u000a starch was an efficient flocculant for freshwater (Parachlorella, Scenedesmus) but not for marine microalgae (Phaeodactylum, Nannochloropsis). At high cationic starch doses, dispersion

  9. Volumetric determination of uranium titanous sulfate as reductant before oxidimetric titration

    USGS Publications Warehouse

    Wahlberg, J.S.; Skinner, D.L.; Rader, L.F., Jr.

    1957-01-01

    Need for a more rapid volumetric method for the routine determination of uranium in uranium-rich materials has led to the development of a method that uses titanous sulfate as a reductant before oxidimetric titration. Separation of the hydrogen sulfide group is not necessary. Interfering elements precipitated by cupferron are removed by automatic filtrations made simultaneously rather than by the longer chloroform extraction method. Uranium is reduced from VI to IV by addition of an excess of titanous sulfate solution, cupric ion serving as an indicator by forming red metallic copper when reduction is complete. The copper is reoxidized by addition of mercuric perchlorate. The reduced uranium is then determined by addition of excess ferric sulfate and titration with ceric sulfate. The method has proved to be rapid, accurate, and economical.

  10. Indirect determination of fluoride by EDTA back-titration of lanthanum.

    PubMed

    Murase, K; Nakagawa, G; Kodama, K; Shiraishi, N

    1977-01-01

    Semimicro to macro amounts of fluoride ion (0.4-100 mg) are determined rapidly and accurately by precipitation with an excess of lanthanum at pH 2.5-2.8 by digestion on a water-bath, cooling to room temperature, addition of excess of EDTA and back-titration of the excess with zinc solution to the Xylenol Orange end-point at ph 5.8-5..9. Large amounts of chloride, acetate and perchlorate, and small amounts of sulphate and silicate do not interfere, but phosphate does. This method is much superior to the usual thorium nitrate titration method and can be applied after preliminary separation of fluorine by steam distillation or pyrolysis. PMID:18962019

  11. Spectrophotometric extractive titrations-IV Determination of zinc in germanium dioxide and germanium chloride.

    PubMed

    Galík, A

    1967-07-01

    A simple and selective determination of zinc in germanium chloride and germanium dioxide is described. The sample is dissolved in sodium potassium tartrate solution and zinc is titrated spectrophotometrically at 532 mug( with a dithizone solution in carbon tetrachloride without discarding the organic phase. Interfering ions such as Bi(III), Cu(II), Cd(II), Co(II), Ni(II), Pb(II), Sn(II), Fe(II), Fe(III), Mn(II) and T1(I) are masked with bis(2-hydroxyethyl)dithiocarbamate. The detection limit is 3-23 x 10(-5)% of zinc and this may be lowered by taking a larger sample and by performing the analysis in a closed system. A simplified technique, consisting of the simultaneous titration of the sample and blank, is described. PMID:18960156

  12. Water determination in composite PEO-based polymer electrolytes by volumetric Karl Fischer titration method.

    PubMed

    Scaccia, Silvera

    2005-10-15

    The determination of water in composite poly(ethylene oxide) (PEO)-based polymer electrolytes by volumetric Karl Fischer (KF) titration is described. The measurements have been carried out on specimens (up to 10 g) of polymer electrolytes (as single components, their mixture and thin film) in a dry-room (relative humidity, RH, <0.2% at 20 degrees C). The use of a dry-room allowed to obtain a baseline drift (defined as the titration rate necessary to keep dry the cell) as low as 0.5 microg H(2)O min(-1). Working range is 0.001-0.5 wt.% H(2)O and precision, expressed as relative standard deviation of seven replicates, is 5 at 0.5 wt.% level. Comparison of the gathered results with those obtained by oven methods are provided. Uptake water from surrounding environment can be detected at a level as low as 0.001 wt.%. PMID:18970224

  13. Combining automatic titration of total iron and sulfur in thermal battery materials

    NASA Astrophysics Data System (ADS)

    Marley, N. A.

    1986-05-01

    Optimal thermal battery performance requires careful control of the iron disulfide content in the catholyte mixture. Previously, the iron and sulfur content of battery materials was determined separately, each requiring a lengthy sample preparation and clean up procedure. A new method has been developed which allows both determinations to be made on the same sample following a simple dissolution procedure. Sample preparation requires oxidation and dissolution with nitric acid followed by dissolution in hydrochloric acid. Iron and sulfur are then determined on sample aliquots by automatic titration. The implementation of this combined procedure for the determination of iron and sulfur by automatic titration has resulted in a substantial reduction in the analysis time. Since sample aliquots are used for each determination, the need to repeat a sample for analysis is rare, improving both the analytical efficiency and sample throughput. Results obtained for sulfur show an improved precision.

  14. 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 generally flows to the west in the study area, and to surface features (lakes, rivers, and springs) particularly in the south and east of the study area where the Springfield Plateau aquifer is closest to land surface. The potentiometric-surface map of the Ozark aquifer indicates a maximum measured water-level altitude of 1,303 feet in the study area at a well in Washington County, Arkansas, and a minimum measured water-level altitude of 390 feet in Ottawa County, Oklahoma. The water in the Ozark aquifer generally flows to the northwest in the northern part of the study area and to the west in the remaining study area. Cones of depression occur in Barry, Barton, Cedar, Jasper, Lawrence, McDonald, Newton, and Vernon Counties in Missouri, Cherokee and Crawford Counties in Kansas, and Craig and Ottawa Counties in Oklahoma. These cones of depression are associated with municipal supply wells. The flow directions, based on both potentiometric-surface maps, generally agree with flow directions indicated by previous studies.

  15. Hydrogeology, groundwater levels, and generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system, 2010–14, in the northern Green River structural basin

    USGS Publications Warehouse

    Bartos, Timothy T.; Hallberg, Laura L.; Miller, Cheryl E.

    2015-01-01

    The groundwater-level measurements were used to construct a generalized potentiometric-surface map of the Green River Basin lower Tertiary aquifer system. Groundwater-level altitudes measured in nonflowing and flowing wells used to construct the potentiometric-surface map ranged from 6,451 to 7,307 feet (excluding four unmeasured flowing wells used for contour construction purposes). The potentiometric-surface map indicates that groundwater in the study area generally moves from north to south, but this pattern of flow is altered locally by groundwater divides, groundwater discharge to the Green River, and possibly to a tributary river (Big Sandy River) and two reservoirs (Fontenelle and Big Sandy Reservoirs).

  16. Comparison Between Potentiometric and Stripping Voltammetric Detection of Trace Metals: Measurements of Cadmium and Lead in the Presence of Thalium, Indium, and Tin.

    PubMed

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

    2009-08-12

    Recent advances in ion-selective electrodes have pushed the detection limits of direct potentiometry to the nanomolar concentration range. Here we present a direct comparison of the sensitivity and selectivity of potentiometric and stripping-voltammetric measurements of cadmium and lead. While both techniques offer a similar sensitivity, the potentiometric method offers higher selectivity in the presence of excess of metal ions (e.g., thallium, tin) that commonly interfere in the stripping-voltammetric operation. Because of the complementary nature of the potentiometric and stripping-voltammetric methods, it is recommended that these techniques will be selected based on the specific analytical problem or used in parallel to provide additional analytical information. PMID:20228885

  17. Titration Curves: A Useful Instrument for Assessing the Buffer Systems of Acidic Mining Waters (10 pp)

    Microsoft Academic Search

    Oliver Totsche; Andrew Fyson; Margarete Kalin; Christian Steinberg

    2006-01-01

    Background, Aims and Scope   The acidification of mine waters is generally caused by metal sulfide oxidation, related to mining activities. These waters\\u000a are characterized by low pH and high acidity due to strong buffering systems. The standard acidity parameter, the Base Neutralization\\u000a Capacity (BNC) is determined by endpoint titration, and reflects a cumulative parameter of both hydrogen ions and all

  18. Comparison of ozone determinations by ultraviolet photometry and gas-phase titration

    NASA Technical Reports Server (NTRS)

    Demore, W. B.; Patapoff, M.

    1976-01-01

    A comparison of ozone determinations based on ultraviolet absorption photometry and gas-phase titration (GPT) shows good agreement between the two methods. Together with other results, these findings indicate that three candidate reference methods for ozone, UV photometry, IR photometry, and GPT are in substantial agreement. However, the GPT method is not recommended for routine use by air pollution agencies for calibration of ozone monitors because of susceptibility to experimental error.

  19. A Geochemical Reaction Model for Titration of Contaminated Soil and Groundwater at the Oak Ridge Reservation

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Parker, J. C.; Gu, B.; Luo, W.; Brooks, S. C.; Spalding, B. P.; Jardine, P. M.; Watson, D. B.

    2007-12-01

    This study investigates geochemical reactions during titration of contaminated soil and groundwater at the Oak Ridge Reservation in eastern Tennessee. The soils and groundwater exhibits low pH and high concentrations of aluminum, calcium, magnesium, manganese, various trace metals such as nickel and cobalt, and radionuclides such as uranium and technetium. The mobility of many of the contaminant species diminishes with increasing pH. However, base additions to increase pH are strongly buffered by various precipitation/dissolution and adsorption/desorption reactions. The ability to predict acid-base behavior and associated geochemical effects is thus critical to evaluate remediation performance of pH manipulation strategies. This study was undertaken to develop a practical but generally applicable geochemical model to predict aqueous and solid-phase speciation during soil and groundwater titration. To model titration in the presence of aquifer solids, an approach proposed by Spalding and Spalding (2001) was utilized, which treats aquifer solids as a polyprotic acid. Previous studies have shown that Fe and Al-oxyhydroxides strongly sorb dissolved Ni, U and Tc species. In this study, since the total Fe concentration is much smaller than that of Al, only ion exchange reactions associated with Al hydroxides are considered. An equilibrium reaction model that includes aqueous complexation, precipitation, ion exchange, and soil buffering reactions was developed and implemented in the code HydroGeoChem 5.0 (HGC5). Comparison of model results with experimental titration curves for contaminated groundwater alone and for soil- water systems indicated close agreement. This study is expected to facilitate field-scale modeling of geochemical processes under conditions with highly variable pH to develop practical methods to control contaminant mobility at geochemically complex sites.

  20. Closed loop odorant injection control utilizing a feedforward and titrator control system

    SciTech Connect

    Bosse, P.H.; Smith, G.A.

    1982-08-01

    Precise measurement of downstream odorant concentration and quick response during flow changes characterize this new concept in odorant control. Incorporating a closed-loop automatic odorant-injection system, this design employs an indicating process controller and an odorant analyzer (Titrator) to provide feedback control. A feedforward control system handles short-term responses to flow changes. Assembled from high-quality, off-the-shelf components, the unit is easy to calibrate and maintain.

  1. Water determination in composite PEO-based polymer electrolytes by volumetric Karl Fischer titration method

    Microsoft Academic Search

    Silvera Scaccia

    2005-01-01

    The determination of water in composite poly(ethylene oxide) (PEO)-based polymer electrolytes by volumetric Karl Fischer (KF) titration is described. The measurements have been carried out on specimens (up to 10g) of polymer electrolytes (as single components, their mixture and thin film) in a dry-room (relative humidity, RH, <0.2% at 20°C). The use of a dry-room allowed to obtain a baseline

  2. AFREM test procedures concerning chlorides in concrete: Extraction and titration methods

    Microsoft Academic Search

    T. Chaussadent; G. Arliguie

    1999-01-01

    The article presents a part of a study carried out by the AFREM “Durability-Chloride penetration in concrete” group. It deals\\u000a with the extraction of “free” and total chlorides from concrete and their titration. The goal is to define test procedures\\u000a that will take into account the chemical behaviour of concrete components, in particular bound chlorides in calcium chloroaluminate.\\u000a The basic

  3. Polypyrrole-based potentiometric sensors: Novel devices for the detection of nitrate and urea

    SciTech Connect

    Hernandez, E.C.; Hutchins, R.S.; Witkowski, A. [Univ. of Kentucky, Lexington, KY (United States)] [and others

    1995-12-31

    Polypyrrole is a sturdy polymer with interesting structural and electronic properties that has found numerous applications in the field of Analytical Chemistry. To illustrate polypyrrole`s versatility in the development of analytical probes, two novel polypyrrole-based potentiometric sensors, one selective for nitrate (NO{sub 3}{sup -}) and the other for urea, will be described. For the nitrate selective electrode, polypyrrole was prepared electrochemically in the presence of a salt of the anion of interest. This electrochemically mediated templating approach resulted in a film that exhibited linear, near-Nernstian response to nitrate (-56 {+-} 1 mV/decade, n=18) over four decades of concentration (5.0 x 10{sup -5} - 0.50 M nitrate) and detection limits of 2 ({+-} 1) x 10{sup -5} M nitrate. The sensor exhibited improved selectivity towards nitrate in the presence of lipophilic anions like Perchlorate and iodide. The second sensor involves the use of polypyrrole as a pH-based transducer to develop a biosensor for urea. Urease was covalently attached to the surface of an amine functionalized polypyrrole film by means of a carbodiimide reaction. The resulting sensor exhibited near-Nernstian behavior to pH changes (-54 {+-} 1 mV/pH unit). The film also responded to urea with high sensitivity (93 mV/decade) and good detection limits of 1.4 x 10{sup -4} {+-} 1 x 10{sup -5} M urea (n=3). The effects on the biosensor of possible interferent species such as N-methylurea and hydroxyurea will be described.

  4. Limitations of Current Polarization for Lowering the Detection Limit of Potentiometric Polymeric Membrane Sensors

    PubMed Central

    Höfler, Lajos; Bedlechowicz, Iwona; Vigassy, Tamás; Gyurcsányi, Róbert E.; Bakker, Eric; Pretsch, Ernö

    2009-01-01

    Ion fluxes across polymeric ion-selective membranes are a decisive parameter dictating the lower detection limit of potentiometric ion sensors. An applied current was earlier proposed to counteract such fluxes and reduce the detection limit to ultra-trace levels. So far, however, the method has not been used in practical situations since the correct current amplitude requires prior knowledge of the sample composition. This paper explores the use of the stir effect to evaluate the optimal current by theory and experiments. It is shown that the traditionally used steady-state model assuming a uniform distribution of ion exchanger in the membrane, fixed with time, violates the electroneutrality condition. A modified steady-state model is introduced that allows for a concentration tilt of the ion exchanger and predicts that a stir effect can indeed be utilized to find the optimal current. Ideally, by choosing the optimal current and very long measurement times, the thermodynamic detection limit might be obtained. However, in practice the stir effect declines at low concentrations and the conditions are far from steady state. Therefore, the improvement of the lower detection limit achievable by galvanostatic control is only about one order of magnitude. A numerical finite-difference approximation is shown to trace the experimental potential responses of silver-selective electrodes well, and to reproduce the stir effect adequately, even for different conditioning protocols. The stir effect is successfully used to improve the detection limit of electrodes with ill-optimized inner solutions, however, significant improvements beyond what is commonly feasible by chemical optimization does not seem to be easily achievable. The results indicate that with conventional membranes the possibility of improving the detection limit by current polarization is much more limited than assumed so far. PMID:19338286

  5. EPR monitored redox titration of the cofactors of Saccharomyces cerevisiae Nar1.

    PubMed

    Hagedoorn, Peter-Leon; van der Weel, Laura; Hagen, Wilfred R

    2014-01-01

    Electron Paramagnetic Resonance (EPR) monitored redox titrations are a powerful method to determine the midpoint potential of cofactors in proteins and to identify and quantify the cofactors in their detectable redox state. The technique is complementary to direct electrochemistry (voltammetry) approaches, as it does not offer information on electron transfer rates, but does establish the identity and redox state of the cofactors in the protein under study. The technique is widely applicable to any protein containing an electron paramagnetic resonance (EPR) detectable cofactor. A typical titration requires 2 ml protein with a cofactor concentration in the range of 1-100 µM. The protein is titrated with a chemical reductant (sodium dithionite) or oxidant (potassium ferricyanide) in order to poise the sample at a certain potential. A platinum wire and a Ag/AgCl reference electrode are connected to a voltmeter to measure the potential of the protein solution A set of 13 different redox mediators is used to equilibrate between the redox cofactors of the protein and the electrodes. Samples are drawn at different potentials and the Electron Paramagnetic Resonance spectra, characteristic for the different redox cofactors in the protein, are measured. The plot of the signal intensity versus the sample potential is analyzed using the Nernst equation in order to determine the midpoint potential of the cofactor. PMID:25490157

  6. Chaotic dynamics of resting ventilatory flow in humans assessed through noise titration

    E-print Network

    Marc Wysocki; Marie-Noelle Fiamma; Christian Straus; Chi-Sang Poon; Thomas Similowski

    2006-06-12

    The mammalian ventilatory behavior exhibits nonlinear dynamics as reflected by certain nonlinearity or complexity indicators (e.g. correlation dimension, approximate entropy, Lyapunov exponents...) but this is not sufficient to determine its possible chaotic nature. To address this, we applied the noise titration technique, previously shown to discern and quantify chaos in short and noisy time series, to ventilatory flow recordings obtained in quietly breathing normal humans. Nine subjects (8 men and 1 woman, 24-42 yrs) were studied during 15-minute epochs of ventilatory steady-state (10.1 +/- 3.0 breaths/minute, tidal volume 0.63 +/- 0.2L). Noise titration applied to the unfiltered signals subsampled at 5 Hz detected nonlinearity in all cases (noise limit 20.2 +/- 12.5%). Noise limit values were weakly correlated to the correlation dimension and the largest Lyapunov exponent of the signals. This study shows that the noise titration approach evidences a chaotic dimension to the behavior of ventilatory flow over time in normal humans during tidal breathing.

  7. Calorimetry, activity, and micro-FTIR analysis of CO chemisorption, titration, and oxidation on supported Pt

    NASA Technical Reports Server (NTRS)

    Sermon, Paul A.; Self, Valerie A.; Vong, Mariana S. W.; Wurie, Alpha T.

    1990-01-01

    The value of in situ analysis on CO chemisorption, titration and oxidation over supported Pt catalysts using calorimetry, catalytic and micro-FTIR methods is illustrated using silica- and titania-supported samples. Isothermal CO-O and O2-CO titrations have not been widely used on metal surfaces and may be complicated if some oxide supports are reduced by CO titrant. However, they can illuminate the kinetics of CO oxidation on metal/oxide catalysts since during such titrations all O and CO coverages are scanned as a function of time. There are clear advantages in following the rates of the catalyzed CO oxidation via calorimetry and gc-ms simultaneously. At lower temperatures the evidence they provide is complementary. CO oxidation and its catalysis of CO oxidation have been extensively studied with hysteresis and oscillations apparent, and the present results suggest the benefits of a combined approach. Silica support porosity may be important in defining activity-temperature hysteresis. FTIR microspectroscopy reveals the chemical heterogeneity of the catalytic surfaces used; it is interesting that the evidence with regard to the dominant CO surface species and their reactivities with regard to surface oxygen for present oxide-supported Pt are different from those seen on graphite-supported Pt.

  8. Titration of biologically active amyloid–? seeds in a transgenic mouse model of Alzheimer's disease

    PubMed Central

    Morales, Rodrigo; Bravo-Alegria, Javiera; Duran-Aniotz, Claudia; Soto, Claudio

    2015-01-01

    Experimental evidence in animal models suggests that misfolded Amyloid-? (A?) spreads in disease following a prion-like mechanism. Several properties characteristics of infectious prions have been shown for the induction of A? aggregates. However, a detailed titration of A? misfolding transmissibility and estimation of the minimum concentration of biologically active A? seeds able to accelerate pathological changes has not yet been performed. In this study, brain extracts from old tg2576 animals were serially diluted and intra-cerebrally injected into young subjects from the same transgenic line. Animals were sacrificed several months after treatment and brain slices were analyzed for amyloid pathology. We observed that administration of misfolded A? was able to significantly accelerate amyloid deposition in young mice, even when the original sample was diluted a million times. The titration curve obtained in this experiment was compared to the natural A? load spontaneously accumulated by these mice overtime. Our findings suggest that administration of the largest dose of A? seeds led to an acceleration of pathology equivalent to over a year. These results show that active A? seeds present in the brain can seed amyloidosis in a titratable manner, similarly as observed for infectious prions. PMID:25879692

  9. Anion-selective light-addressable potentiometric sensors (LAPS) for the determination of nitrate and sulphate ions

    Microsoft Academic Search

    Yu. G. Mourzina; Yu. E. Ermolenko; T. Yoshinobu; Yu. Vlasov; H. Iwasaki; M. J. Schöning

    2003-01-01

    The technology of fabrication of anion-selective light-addressable potentiometric sensors (LAPS) by using a solid-state microelectronic device integrated with an ion-recognition membrane has been elaborated. The nitrate sensor with ion-exchange membrane exhibits a linear response interval of 3×10?5 to 1×10?1mol\\/l NO3? with an ionic sensitivity of 58±2mV\\/pNO3. The detection limit was found to be 1×10?5mol\\/l of nitrate ions and the working

  10. Method for encapsulating and isolating hazardous cations, medium for encapsulating and isolating hazardous cations

    DOEpatents

    Wasserman, Stephen R. (Darien, IL); Anderson, Kenneth B. (Lisle, IL); Song, Kang (Woodridge, IL); Yuchs, Steven E. (Naperville, IL); Marshall, Christopher L. (Naperville, IL)

    1998-01-01

    A method for encapsulating hazardous cations is provided comprising supplying a pretreated substrate containing the cations; contacting the substrate with an organo-silane compound to form a coating on the substrate; and allowing the coating to cure. A medium for containing hazardous cations is also provided, comprising a substrate having ion-exchange capacity and a silane-containing coating on the substrate.

  11. [Photometric micro-titration model of DPPH radicals scavenging activity and its application].

    PubMed

    Gao, Yun-tao; Wei, Wei; Ye, Li-qing; Li, Xiao-fen; Liu, Ping; Zhang, Hong-jiao; Yang, Lu; Yu, Jiao-jiao; Cha, Jia-wei

    2015-02-01

    In the present paper, the stoichiometric ratio (R) for the interreaction of DPPH radicals with the antoxidant was employed as a evaluation index for DPPH radicals scavenging activity of antioxidants. This evaluation index was related only with the stoichiometric relationship between DPPH radicals and the antioxidant, not the relationship with the initial DPPH amount and the volume of sample, which could offer a solution for the problem of poor comparability of EC50 under different conditions. A novel photometric micro-titration method was proposed for the determination of the stoichiometric ratio (R) for the interreaction of DPPH radicals with the antoxidant. The titration equation was established based on the absorbance difference (deltaA) of DPPH radicals in the titration process and the added amount of antoxidant. The stoichiometric ratio (R) for the reaction of DPPH radicals with the addition amount of antoxidant was determined by the titration equation obtained, while, the DPPH median elimination concentration (EC50) of antoxidant can be calculated by the stoichiometric ratio (R). The above photometric micro-titration model was verified using rutin as DPPH radicals scavenger. As experiment results, the stoichiometric ratio (R) of DPPH radicals to rutin was determined to be in the range of 1.817-1.846. The calculated value of EC50 was 1.196 x 10(-3), 2.392 x 10(-3), 4.819 x 10(-3) and 7.292 x 10(-3) mg x mL(-1) for 1.12 x 10(-7), 2.24 x 10(-7), 4.48 x 10(-7) and 6.72 x 10(-7) mol of the additon amount of DPPH radicals, respectively. The proposed method has better precision and reliability with smaller amount of sample than conventional method. While, the obtained stoichiometric ratio value (R) of rutin was employed to calculate the rutin median elimination concentration for DPPH EC50) according to the conditions as reported in the literatures, and the calculated results were consistent with that reported in the literatures. PMID:25970919

  12. Maitotoxin, a cationic channel activator.

    PubMed

    Escobar, L I; Salvador, C; Martínez, M; Vaca, L

    1998-01-01

    Maitotoxin (MTX), a water soluble polyether obtained from the marine dinoflagellate Gambierdiscus toxicus is one of the entities responsible for Ciguatera, a form of seafood poisoning. This toxin is a potent activator of changes in the intracellular Ca2+ concentrations of cells from a wide variety of organisms. Evidence published in the last few years strongly suggests that this toxin has no ionophoretic activity. Molecular mechanics studies, shown for the first time in this review, models MTX as a molecular 'wire'. The present work compiles the few studies developed with electrophysiological techniques. All these reports indicate that MTX is activating a voltage independent, nonselective cationic channel, which in some preparations requires the presence of extracellular Ca2+ for channel activation. The conductance estimated from a variety of tissues is in the order of 12-40 pS. Thus far, no specific blocker has been identified for this channel. The nature of the MTX receptor remains a mistery. PMID:9713832

  13. The allergenicity of complex cations.

    PubMed

    Schallreuter, K U; Wood, J M

    1986-02-26

    A homologous series of eight quaternary ammonium salts (quats) were used as complex cations in a survey of contact hypersensitivity in guinea pigs. Two of the quats tested were found to be strong allergens which was due to stable association with membrane lipids at the surface of epidermal cells. This surface complexation reaction was studied in detail by using a spin-labelled quat of intermediate allergenicity. Electron spin resonance was used to show that stable "ion pairs" are formed between membrane receptor sites and the two strong allergens. Information was obtained on the specificity and kinetics of immunogenic complex formation as well as on the position and orientation of these haptens on epidermal receptor sites in vivo. PMID:3006681

  14. The association of octadecyl-end-capped poly-(sodium 2-acrylamido-2-methylpropanesulfonates) in water and salt solutions: A study by fluorescence spectroscopy and isothermal titration calorimetry

    NASA Astrophysics Data System (ADS)

    Mizusaki, M.; Morishima, Y.; Raju, B. B.; Winnik, F. M.

    Steady-state fluorescence spectroscopy and isothermal titration calorimetry (ITC) have been used to study the aggregation in aqueous solutions of poly-(2-acrylamido)-2-methylpropanesulfonic acids, sodium salt mono-endcapped with either N,N-di-n-octadecyl or N-4-[(1-pyrenyl)butyl]-N-n-octadecyl which were prepared by free radical polymerization of 2-(acrylamido)-2-methylpropane sulfonic acid (AMPS) initiated with the azo compounds, 4,4'-azobis{cyano-N,N-di-n-octadecyl}pentanamide and 4,4'-azobis{cyano-N,N-[4-(1-pyrenyl)butyl]-n-octadecyl}pentanamide, respectively. Both techniques indicate the occurrence of multimolecular aggregates in solutions of the polymers in water and in 0.2 M NaCl. The concentration range for aggregation is about 1-14 mmol AMPS l^{-1} (0.5-2.7 g l^{-1}) in 0.2 M NaCl and the enthalpy of micellization, estimated from ITC data, is 100 J [mol AMPS]^{-1}. The accessibility of the chromophores to neutral molecules and to cationic species was assessed by quenching of fluorescence with nitromethane and thallium nitrate, respectively. The association of the mono-endcapped polymers is compared to that of PAMPS derivatives carrying hydrophobic groups randomly attached along the chain.

  15. Structural Thermodynamics of Cationic Liposome DNA System

    E-print Network

    Hernández Contreras, Martín

    Structural Thermodynamics of Cationic Liposome DNA System O. González-Amezcua and M. Hernández.P. 14-740, México Distrito Federal, Mexico Abstract. Cationic liposomes serve as useful vehicles form two dimen- sional crystalline arrays in the carrier liposome interior. One expects that a precise

  16. Proton nuclear magnetic resonance spectroscopy of human transferrin N-terminal half-molecule: titration and hydrogen-deuterium exchange

    Microsoft Academic Search

    A. A. Valcour; R. C. Woodworth

    1987-01-01

    The binding of Ga(III) to the proteolytically derived N-terminal half-molecule of human transferrin (HTF\\/2N) was studied by proton nuclear magnetic resonance spectroscopy. The pH-dependent titration curves of the histidinyl C(2) proton chemical shifts were altered upon formation of the GaIIIHTF\\/2N(CâOâ) ternary complex. Two high-pK'a histidines failed to titrate when the metal and synergistic anion formed a complex with the protein.

  17. Organic cation secretion in flounder renal tissue

    SciTech Connect

    Miller, D.S.; Holohan, P.D. (National Institutes of Health, Research Triangle Park, NC (USA) State Univ. of New York Upstate Medical Center, Syracuse, NY (USA) Mount Desert Island Biological Laboratory, Salsbury Cove, ME (USA))

    1987-12-01

    In the winter flounder, Pseudopleuronectes americanus, renal clearance experiments showed that the model organic cations, tetraethylammonium (TEA) and N{prime}-methylnicotinamide (NMN), were strongly secreted; organic cation-to-polyethylene glycol (glomerular filtration rate marker) clearance ratios averaged 130 and 30, respectively. TEA uptake by isolated renal tubular masses was concentrative and saturable. Transport was inhibited by competitor organic cations and reduced by exposure to NaCN, 2,4-dinitrophenol, ouabain, and HgCl{sub 2}. Organic anions did not reduce TEA uptake. NMN was the poorest inhibitor of TEA uptake of all the organic cations tested. In addition, the rate of NMN uptake was slower than that of TEA, and the steady-state tissue-to-medium ratio was lower. The data show the presence of an organic cation secretory system in flounder tissue that resembles the mammalian systems in several respects.

  18. The ?-Cation Radical of Chlorophyll a*

    PubMed Central

    Borg, Donald C.; Fajer, Jack; Felton, Ronald H.; Dolphin, David

    1970-01-01

    Chlorophyll a undergoes reversible one-electron oxidation in dichloromethane and butyronitrile. Removal of the electron by controlled potential electrolysis or by stoichiometric charge transfer to a known cation radical yields a radical (epr line width = 9 gauss, g = 2.0025 ± 0.0001) whose optical spectrum is bleached relative to that of chlorophyll. Upon electrophoresis this bleached species behaves as a cation. By comparison with the known properties of ?-cation radicals of porphyrins and chlorins, the chlorophyll radical is also identified as a ?-cation. Further correlation of optical and epr properties with published studies on photosynthesis leads to the conclusion that oxidized P700, the first photochemical product of photosystem I in green plants, contains a ?-cation radical of the chlorin component of chlorophyll a. This radical is the likely source of the rapidly-decaying, narrow epr signal of photosynthesis. PMID:16591873

  19. A Full Automatic Device for Sampling Small Solution Volumes in Photometric Titration Procedure Based on Multicommuted Flow System

    PubMed Central

    Borges, Sivanildo S.; Vieira, Gláucia P.; Reis, Boaventura F.

    2007-01-01

    In this work, an automatic device to deliver titrant solution into a titration chamber with the ability to determine the dispensed volume of solution, with good precision independent of both elapsed time and flow rate, is proposed. A glass tube maintained at the vertical position was employed as a container for the titrant solution. Electronic devices were coupled to the glass tube in order to control its filling with titrant solution, as well as the stepwise solution delivering into the titration chamber. The detection of the titration end point was performed employing a photometer designed using a green LED (?=545 nm) and a phototransistor. The titration flow system comprised three-way solenoid valves, which were assembled to allow that the steps comprising the solution container loading and the titration run were carried out automatically. The device for the solution volume determination was designed employing an infrared LED (?=930 nm) and a photodiode. When solution volume delivered from proposed device was within the range of 5 to 105 ?l, a linear relationship (R = 0.999) between the delivered volumes and the generated potential difference was achieved. The usefulness of the proposed device was proved performing photometric titration of hydrochloric acid solution with a standardized sodium hydroxide solution and using phenolphthalein as an external indicator. The achieved results presented relative standard deviation of 1.5%. PMID:18317510

  20. Evaluation of the 5 and 8 pH point titration methods for monitoring anaerobic digesters treating solid waste.

    PubMed

    Vannecke, T P W; Lampens, D R A; Ekama, G A; Volcke, E I P

    2015-04-01

    Simple titration methods certainly deserve consideration for on-site routine monitoring of volatile fatty acid (VFA) concentration and alkalinity during anaerobic digestion (AD), because of their simplicity, speed and cost-effectiveness. In this study, the 5 and 8 pH point titration methods for measuring the VFA concentration and carbonate system alkalinity (H2CO3*-alkalinity) were assessed and compared. For this purpose, synthetic solutions with known H2CO3*-alkalinity and VFA concentration as well as samples from anaerobic digesters treating three different kind of solid wastes were analysed. The results of these two related titration methods were verified with photometric and high-pressure liquid chromatography measurements. It was shown that photometric measurements lead to overestimations of the VFA concentration in the case of coloured samples. In contrast, the 5 pH point titration method provides an accurate estimation of the VFA concentration, clearly corresponding with the true value. Concerning the H2CO3*-alkalinity, the most accurate and precise estimations, showing very similar results for repeated measurements, were obtained using the 8 pH point titration. Overall, it was concluded that the 5 pH point titration method is the preferred method for the practical monitoring of AD of solid wastes due to its robustness, cost efficiency and user-friendliness. PMID:25224566

  1. Potentiometric flow injection sensing system for determination of heparin based on current-controlled release of protamine.

    PubMed

    Lei, Jiahong; Ding, Jiawang; Chen, Yan; Qin, Wei

    2015-02-01

    A flow injection system incorporated with a polycation-sensitive polymeric membrane electrode in the flow cell is proposed for potentiometric determination of heparin. An external current in nano-ampere scale is continuously applied across the polymeric membrane for controlled release of protamine from the inner filling solution to the sample solution, which makes the electrode membrane regenerate quickly after each measurement. The protamine released at membrane-sample interface is consumed by heparin injected into the flow cell via their strong electrostatic interaction, thus decreasing the measured potential, by which heparin can be detected. Under optimized conditions, a linear relationship between the potential peak height and the concentration of heparin in the sample solution can be obtained in the range of 0.1-2.0 U mL(-1), and the detection limit is 0.06 U mL(-1). The proposed potentiometric sensing system has been successfully applied to the determination of heparin in undiluted sheep whole blood. PMID:25597803

  2. Rapid identification of biological warfare agents using an instrument employing a light addressable potentiometric sensor and a flow-through immunofiltration-enzyme assay system

    Microsoft Academic Search

    Keith A Uithoven; John C Schmidt; Mark E Ballman

    2000-01-01

    An instrument employing a light addressable potentiometric sensor and a flow-through immunofiltration-enzyme assay system has been developed for the rapid and specific identification of biological warfare (BW) agents. The system has been designed to assay for up to eight agents simultaneously and provides an indication of the absence or presence of a threat within 15 min. Parameters affecting the mixing

  3. Novel Flow Injection\\/Potentiometric Measurement of Slightly Soluble Salts in Small Volumes: Determination of Solubility Product Constants of Some Silver Salts

    Microsoft Academic Search

    Amin T. Haj-hussein; Gary D. Christian

    1986-01-01

    The flow injection technique is shown to provide fast, reliable and sensitive determination of solubility product constants of silver acetate, silver sulfate, silver oxide, silver bromate and silver chloride in microliter volume samples. Potentiometric detection using electrodes of the first kind and second kind was used for measuring silver ions and chloride ions, respectively. The solubilities were determined from measurement

  4. Simultaneous determination of zinc, cadmium and lead in environmental water samples by potentiometric stripping analysis (PSA) using multiwalled carbon nanotube electrode

    Microsoft Academic Search

    César Ricardo Teixeira Tarley; Vivian Silva Santos; Bruno Eduardo Lobo Baêta; Arnaldo César Pereira; Lauro Tatsuo Kubota

    2009-01-01

    The present paper has focused on the potential application of multiwalled carbon nanotube for the development of a new, simple and highly selective electrochemical method for simultaneous Zn (II), Cd (II) and Pb (II) monitoring in water samples (lake and effluent waters), by using potentiometric stripping analysis (PSA). The electrochemical method is based on simultaneous preconcentration\\/reduction of metal ions onto

  5. Probing oppositely charged surfactant and copolymer interactions by isothermal titration microcalorimetry

    E-print Network

    J. Courtois; J. -F. Berret

    2011-07-26

    The complexation between charged-neutral block copolymers and oppositely charged surfactants was investigated by light scattering experiments and by isothermal titration calorimetry (ITC). The copolymer was poly(sodium acrylate)-b-poly(acrylamide) and the surfactant dodecyltrimethylammonium bromide (DTAB). In a previous report, we had shown that the copolymers and the surfactants co-assembled spontaneously into colloidal complexes. Depending of the charge ratio Z = [DTA+]/[COO-], the complexes were either single surfactant micelles decorated by copolymers, or core-shell hierarchical structures. ITC was performed in order to investigate the thermodynamics of the complex formation. Titrations of copolymers by surfactants and of surfactants by copolymers revealed that the electrostatic co-assembly was an endothermic reaction, suggesting a process dominated by the entropy of the counterions. Here we found that the thermodynamic quantities associated with the reaction depended on the mixing order. When surfactants were added stepwise to copolymers, the titration was associated with the formation of single micelles decorated by a unique polymer. Above a critical charge ratio, the micelles rearranged themselves into 100 nm colloidal complexes in a collective process which displayed the following features : i) the process was very slow as compared to the timescale of Brownian diffusion, ii) the thermodynamic signature was a endothermic peak and iii) the stoichiometry between the positive and negative charges was modified from n = 0.48 (single micelles) to 0.75 (core-shell complexes). The amount of polyelectrolytes needed for the complex formation exceeded the number required to compensate the net micellar charge, confirming the evidence of overcharging in the complex formation.

  6. Non-damaging laser therapy of the macula: Titration algorithm and tissue response

    NASA Astrophysics Data System (ADS)

    Palanker, Daniel; Lavinsky, Daniel; Dalal, Roopa; Huie, Philip

    2014-02-01

    Retinal photocoagulation typically results in permanent scarring and scotomata, which limit its applicability to the macula, preclude treatments in the fovea, and restrict the retreatments. Non-damaging approaches to laser therapy have been tested in the past, but the lack of reliable titration and slow treatment paradigms limited their clinical use. We developed and tested a titration algorithm for sub-visible and non-damaging treatments of the retina with pulses sufficiently short to be used with pattern laser scanning. The algorithm based on Arrhenius model of tissue damage optimizes the power and duration for every energy level, relative to the threshold of lesion visibility established during titration (and defined as 100%). Experiments with pigmented rabbits established that lesions in the 50-75% energy range were invisible ophthalmoscopically, but detectable with Fluorescein Angiography and OCT, while at 30% energy there was only very minor damage to the RPE, which recovered within a few days. Patients with Diabetic Macular Edema (DME) and Central Serous Retinopathy (CSR) have been treated over the edematous areas at 30% energy, using 200?m spots with 0.25 diameter spacing. No signs of laser damage have been detected with any imaging modality. In CSR patients, subretinal fluid resolved within 45 days. In DME patients the edema decreased by approximately 150?m over 60 days. After 3-4 months some patients presented with recurrence of edema, and they responded well to retreatment with the same parameters, without any clinically visible damage. This pilot data indicates a possibility of effective and repeatable macular laser therapy below the tissue damage threshold.

  7. Molecular Dynamics Simulation of the Titration of Polyoxocations in Aqueous Solution

    SciTech Connect

    Rustad, James R.

    2005-09-01

    The aqueous complex ion Al30O8(OH)56(H2O)26 18+(Al30) has a variety of bridging and terminal amphoteric surface functional groups which deprotonate over a pH range of 4–7. Their relative degree of protonation is calculated here from a series of molecular dynamics simulations in what appear to be the first molecular dynamics simulations of an acidometric titration. In these simulations, a model M30O8(OH)56(H2O)26 18+ ion is embedded in aqueous solution and titrated with hydroxide ions in the presence of a charge-compensating background of perchlorate ions. Comparison with titration of a model M13O4(OH)24(H2O)12 7+ reveals that the M30 ion is more acidic than the M13 ion due to the presence of acidic nH2O functional groups. The higher acidities of the functional groups on the M30 ion appear to result from enhanced hydration. Metal–oxygen bond lengths are calculated for the ion in solution, an isolated ion in the gas phase, and in its crystalline hydrate sulfate salt. Gas-phase and crystalline bond lengths do not correlate well with those calculated in solution. The acidities do not relate in any simple way to the number of metals coordinating the surface functional group or the M-O bond length. Moreover, the calculated acidity in solution does not correlate with proton affinities calculated for the isolated ion in the absence of solvent. It is concluded that the search for simple indicators of structure–reactivity relationships at the level of individual reactive sites faces major limitations, unless specific information on the hydration states of the functional groups is available.

  8. Cation-? interactions in protonated phenylalkylamines.

    PubMed

    Chiavarino, Barbara; Crestoni, Maria Elisa; Schütz, Markus; Bouchet, Aude; Piccirillo, Susanna; Steinmetz, Vincent; Dopfer, Otto; Fornarini, Simonetta

    2014-08-28

    Phenylalkylamines of the general formula C6H5(CH2)nNH2 (n = 1-4) have been delivered to the gas phase as protonated species using electrospray ionization. The ions thus formed have been assayed by IRMPD spectroscopy in two different spectroscopic domains, namely, the 600-1800 and the 3000-3500 cm(-1) regions using either an IR free electron laser or a tabletop OPO/OPA laser source. The interpretation of the experimental spectra is aided by density functional theory calculations of candidate species and vibrational frequency analyses. Protonated benzylamine presents a relatively straightforward instance of a single stable conformer, providing a trial case for the adopted approach. Turning to the higher homologues, C6H5(CH2)nNH3(+) (n = 2-4), more conformations become accessible. For each C6H5(CH2)nNH3(+) ion (n = 2-4), the most stable geometry is characterized by cation-? interactions between the positively charged ammonium group and the aromatic ?-electronic system, permitted by the folding of the polymethylene chain. The IRMPD spectra of the sampled ions confirm the presence of the folded structures by comparison with the calculated IR spectra of the various possible conformers. An inspection of the NH stretching region is helpful in this regard. PMID:25061749

  9. A simple method to prepare magnetic modified beer yeast and its application for cationic dye adsorption.

    PubMed

    Yu, Jun-Xia; Wang, Li-Yan; Chi, Ru-An; Zhang, Yue-Fei; Xu, Zhi-Gao; Guo, Jia

    2013-01-01

    The purpose of this research is to use a simple method to prepare magnetic modified biomass with good adsorption performances for cationic ions. The magnetic modified biomass was prepared by two steps: (1) preparation of pyromellitic dianhydride (PMDA) modified biomass in N, N-dimethylacetamide solution and (2) preparation of magnetic PMDA modified biomass by a situ co-precipitation method under the assistance of ultrasound irradiation in ammonia water. The adsorption potential of the as-prepared magnetic modified biomass was analyzed by using cationic dyes: methylene blue and basic magenta as model dyes. Optical micrograph and x-ray diffraction analyses showed that Fe(3)O(4) particles were precipitated on the modified biomass surface. The as-prepared biosorbent could be recycled easily by using an applied magnetic field. Titration analysis showed that the total concentration of the functional groups on the magnetic PMDA modified biomass was calculated to be 0.75 mmol g(-1) by using the first derivative method. The adsorption capacities (q(m)) of the magnetic PMDA modified biomass for methylene blue and basic magenta were 609.0 and 520.9 mg g(-1), respectively, according to the Langmuir equation. Kinetics experiment showed that adsorption could be completed within 150 min for both dyes. The desorption experiment showed that the magnetic sorbent could be used repeatedly after regeneration. The as-prepared magnetic modified sorbent had a potential in the dyeing industry wastewater treatment. PMID:22529003

  10. Automated high-pressure titration system with in situ infrared spectroscopic detection

    SciTech Connect

    Thompson, Christopher J., E-mail: chris.thompson@pnnl.gov; Martin, Paul F.; Chen, Jeffrey; Schaef, Herbert T.; Rosso, Kevin M.; Felmy, Andrew R.; Loring, John S. [Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)] [Pacific Northwest National Laboratory, Richland, Washington 99352 (United States); Benezeth, Pascale [Géosciences Environnement Toulouse (GET), CNRS-Université de Toulouse, 31400 Toulouse (France)] [Géosciences Environnement Toulouse (GET), CNRS-Université de Toulouse, 31400 Toulouse (France)

    2014-04-15

    A fully automated titration system with infrared detection was developed for investigating interfacial chemistry at high pressures. The apparatus consists of a high-pressure fluid generation and delivery system coupled to a high-pressure cell with infrared optics. A manifold of electronically actuated valves is used to direct pressurized fluids into the cell. Precise reagent additions to the pressurized cell are made with calibrated tubing loops that are filled with reagent and placed in-line with the cell and a syringe pump. The cell's infrared optics facilitate both transmission and attenuated total reflection (ATR) measurements to monitor bulk-fluid composition and solid-surface phenomena such as adsorption, desorption, complexation, dissolution, and precipitation. Switching between the two measurement modes is accomplished with moveable mirrors that direct the light path of a Fourier transform infrared spectrometer into the cell along transmission or ATR light paths. The versatility of the high-pressure IR titration system was demonstrated with three case studies. First, we titrated water into supercritical CO{sub 2} (scCO{sub 2}) to generate an infrared calibration curve and determine the solubility of water in CO{sub 2} at 50?°C and 90 bar. Next, we characterized the partitioning of water between a montmorillonite clay and scCO{sub 2} at 50?°C and 90 bar. Transmission-mode spectra were used to quantify changes in the clay's sorbed water concentration as a function of scCO{sub 2} hydration, and ATR measurements provided insights into competitive residency of water and CO{sub 2} on the clay surface and in the interlayer. Finally, we demonstrated how time-dependent studies can be conducted with the system by monitoring the carbonation reaction of forsterite (Mg{sub 2}SiO{sub 4}) in water-bearing scCO{sub 2} at 50?°C and 90 bar. Immediately after water dissolved in the scCO{sub 2}, a thin film of adsorbed water formed on the mineral surface, and the film thickness increased with time as the forsterite began to dissolve. However, after approximately 2.5 h, the trend reversed, and a carbonate precipitate began to form on the forsterite surface, exposing dramatic chemical changes in the thin-water film. Collectively, these applications illustrate how the high-pressure IR titration system can provide molecular-level information about the interactions between variably wet scCO{sub 2} and minerals relevant to underground storage of CO{sub 2} (geologic carbon sequestration). The apparatus could also be utilized to study high-pressure interfacial chemistry in other areas such as catalysis, polymerization, food processing, and oil and gas recovery.

  11. Automated High-Pressure Titration System with In Situ Infrared Spectroscopic Detection

    SciTech Connect

    Thompson, Christopher J.; Martin, Paul F.; Chen, Jeffrey; Benezeth, Pascale; Schaef, Herbert T.; Rosso, Kevin M.; Felmy, Andrew R.; Loring, John S.

    2014-04-17

    A fully automated titration system with infrared detection was developed for investigating interfacial chemistry at high pressures. The apparatus consists of a high-pressure fluid generation and delivery system coupled to a high-pressure cell with infrared optics. A manifold of electronically actuated valves is used to direct pressurized fluids into the cell. Precise reagent additions to the pressurized cell are made with calibrated tubing loops that are filled with reagent and placed in-line with the cell and a syringe pump. The cell’s infrared optics facilitate both transmission and attenuated total reflection (ATR) measurements to monitor bulk-fluid composition and solid-surface phenomena such as adsorption, desorption, complexation, dissolution, and precipitation. Switching between the two measurement modes is accomplished with moveable mirrors that direct radiation from a Fourier transform infrared spectrometer into the cell along transmission or ATR light paths. The versatility of the high-pressure IR titration system is demonstrated with three case studies. First, we titrated water into supercritical CO2 (scCO2) to generate an infrared calibration curve and determine the solubility of water in CO2 at 50 °C and 90 bar. Next, we characterized the partitioning of water between a montmorillonite clay and scCO2 at 50 °C and 90 bar. Transmission-mode spectra were used to quantify changes in the clay’s sorbed water concentration as a function of scCO2 hydration, and ATR measurements provided insights into competitive residency of water and CO2 on the clay surface and in the interlayer. Finally, we demonstrated how time-dependent studies can be conducted with the system by monitoring the carbonation reaction of forsterite (Mg2SiO4) in water-bearing scCO2 at 50 °C and 90 bar. Immediately after water dissolved in the scCO2, a thin film of adsorbed water formed on the mineral surface, and the film thickness increased with time as the forsterite began to dissolve. However, after approximately 2.5 hours, the trend reversed, and a carbonate precipitate began to form on the forsterite surface, exposing dramatic chemical changes in the thin-water film. Collectively, these applications illustrate how the high-pressure IR titration system can provide molecular-level information about the interactions between variably wet scCO2 and minerals relevant to underground storage of CO2 (geologic carbon sequestration). The apparatus could also be utilized to study high-pressure interfacial chemistry in other areas such as catalysis, polymerization, food processing, and oil and gas recovery.

  12. Automated high-pressure titration system with in situ infrared spectroscopic detection.

    PubMed

    Thompson, Christopher J; Martin, Paul F; Chen, Jeffrey; Benezeth, Pascale; Schaef, Herbert T; Rosso, Kevin M; Felmy, Andrew R; Loring, John S

    2014-04-01

    A fully automated titration system with infrared detection was developed for investigating interfacial chemistry at high pressures. The apparatus consists of a high-pressure fluid generation and delivery system coupled to a high-pressure cell with infrared optics. A manifold of electronically actuated valves is used to direct pressurized fluids into the cell. Precise reagent additions to the pressurized cell are made with calibrated tubing loops that are filled with reagent and placed in-line with the cell and a syringe pump. The cell's infrared optics facilitate both transmission and attenuated total reflection (ATR) measurements to monitor bulk-fluid composition and solid-surface phenomena such as adsorption, desorption, complexation, dissolution, and precipitation. Switching between the two measurement modes is accomplished with moveable mirrors that direct the light path of a Fourier transform infrared spectrometer into the cell along transmission or ATR light paths. The versatility of the high-pressure IR titration system was demonstrated with three case studies. First, we titrated water into supercritical CO2 (scCO2) to generate an infrared calibration curve and determine the solubility of water in CO2 at 50?°C and 90 bar. Next, we characterized the partitioning of water between a montmorillonite clay and scCO2 at 50?°C and 90 bar. Transmission-mode spectra were used to quantify changes in the clay's sorbed water concentration as a function of scCO2 hydration, and ATR measurements provided insights into competitive residency of water and CO2 on the clay surface and in the interlayer. Finally, we demonstrated how time-dependent studies can be conducted with the system by monitoring the carbonation reaction of forsterite (Mg2SiO4) in water-bearing scCO2 at 50?°C and 90 bar. Immediately after water dissolved in the scCO2, a thin film of adsorbed water formed on the mineral surface, and the film thickness increased with time as the forsterite began to dissolve. However, after approximately 2.5 h, the trend reversed, and a carbonate precipitate began to form on the forsterite surface, exposing dramatic chemical changes in the thin-water film. Collectively, these applications illustrate how the high-pressure IR titration system can provide molecular-level information about the interactions between variably wet scCO2 and minerals relevant to underground storage of CO2 (geologic carbon sequestration). The apparatus could also be utilized to study high-pressure interfacial chemistry in other areas such as catalysis, polymerization, food processing, and oil and gas recovery. PMID:24784630

  13. The effects of solubility, ionization, and polarity on end points in high frequency titrations 

    E-print Network

    White, James Decker

    1951-01-01

    milliliters of 2-acetone-l-benzene, l. Addition of 5 milliliters of 9-bensene 1-methanol' 2. Addition of 3 millilitera of 1-bensene- 1-methanol' 3, Addition of 2 milliliters of 1-bensens- 2-methanoli 4 ~ Addition of' 3 milliliters of methanol, VI...- 2-methanol' Titration of 10 millV itsrs of 0. 1039 N 43 lauric acid by 0 38~6 H HaOCH3 in methanol, g3 VIII. Variations in loedinH caused by add1tlon of titz'ant solvents to 50 milliliters of l-acetone-l-benzene. 1 ~ Addition of 5 m111111tsrs...

  14. Inclusion complex of benzocaine and ?-cyclodextrin: 1H NMR and isothermal titration calorimetry studies

    NASA Astrophysics Data System (ADS)

    Mic, Mihaela; P?rn?u, Adrian; Bogdan, Mircea; Turcu, Ioan

    2013-11-01

    The supramolecular structure of the inclusion complex of ?-cyclodextrin with benzocaine in aqueous solution has been investigated by 1H NMR spectroscopy and isothermal titration nanocalorimetry (ITC). Analysis of 1H NMR data by continuous variation method indicates that the benzocaine: ?-cyclodextrin inclusion complex occurs and has a 1:1 stoichiometry. Rotating frame NOE spectroscopy (ROESY) was used to ascertain the solution geometry of the host-guest complex which indicates that the benzocaine molecule was included with the aromatic ring into the cyclodextrin cavity. Although the affinity of benzocaine for cyclodextrin is relatively high, the association constant cannot be measured using ITC due to the low solubility of benzocaine in water.

  15. Automated high-pressure titration system with in situ infrared spectroscopic detection

    NASA Astrophysics Data System (ADS)

    Thompson, Christopher J.; Martin, Paul F.; Chen, Jeffrey; Benezeth, Pascale; Schaef, Herbert T.; Rosso, Kevin M.; Felmy, Andrew R.; Loring, John S.

    2014-04-01

    A fully automated titration system with infrared detection was developed for investigating interfacial chemistry at high pressures. The apparatus consists of a high-pressure fluid generation and delivery system coupled to a high-pressure cell with infrared optics. A manifold of electronically actuated valves is used to direct pressurized fluids into the cell. Precise reagent additions to the pressurized cell are made with calibrated tubing loops that are filled with reagent and placed in-line with the cell and a syringe pump. The cell's infrared optics facilitate both transmission and attenuated total reflection (ATR) measurements to monitor bulk-fluid composition and solid-surface phenomena such as adsorption, desorption, complexation, dissolution, and precipitation. Switching between the two measurement modes is accomplished with moveable mirrors that direct the light path of a Fourier transform infrared spectrometer into the cell along transmission or ATR light paths. The versatility of the high-pressure IR titration system was demonstrated with three case studies. First, we titrated water into supercritical CO2 (scCO2) to generate an infrared calibration curve and determine the solubility of water in CO2 at 50 °C and 90 bar. Next, we characterized the partitioning of water between a montmorillonite clay and scCO2 at 50 °C and 90 bar. Transmission-mode spectra were used to quantify changes in the clay's sorbed water concentration as a function of scCO2 hydration, and ATR measurements provided insights into competitive residency of water and CO2 on the clay surface and in the interlayer. Finally, we demonstrated how time-dependent studies can be conducted with the system by monitoring the carbonation reaction of forsterite (Mg2SiO4) in water-bearing scCO2 at 50 °C and 90 bar. Immediately after water dissolved in the scCO2, a thin film of adsorbed water formed on the mineral surface, and the film thickness increased with time as the forsterite began to dissolve. However, after approximately 2.5 h, the trend reversed, and a carbonate precipitate began to form on the forsterite surface, exposing dramatic chemical changes in the thin-water film. Collectively, these applications illustrate how the high-pressure IR titration system can provide molecular-level information about the interactions between variably wet scCO2 and minerals relevant to underground storage of CO2 (geologic carbon sequestration). The apparatus could also be utilized to study high-pressure interfacial chemistry in other areas such as catalysis, polymerization, food processing, and oil and gas recovery.

  16. Titration of aspartate-85 in bacteriorhodopsin: what it says about chromophore isomerization and proton release.

    PubMed Central

    Balashov, S P; Imasheva, E S; Govindjee, R; Ebrey, T G

    1996-01-01

    Titration of Asp-85, the proton acceptor and part of the counterion in bacteriorhodopsin, over a wide pH range (2-11) leads us to the following conclusions: 1) Asp-85 has a complex titration curve with two values of pKa; in addition to a main transition with pKa = 2.6 it shows a second inflection point at high pH (pKa = 9.7 in 150-mM KCl). This complex titration behavior of Asp-85 is explained by interaction of Asp-85 with an ionizable residue X'. As follows from the fit of the titration curve of Asp-85, deprotonation of X' increases the proton affinity of Asp-85 by shifting its pKa from 2.6 to 7.5. Conversely, protonation of Asp-85 decreases the pKa of X' by 4.9 units, from 9.7 to 4.8. The interaction between Asp-85 and X' has important implications for the mechanism of proton transfer. In the photocycle after the formation of M intermediate (and protonation of Asp-85) the group X' should release a proton. This deprotonated state of X' would stabilize the protonated state of Asp-85.2) Thermal isomerization of the chromophore (dark adaptation) occurs on transient protonation of Asp-85 and formation of the blue membrane. The latter conclusion is based on the observation that the rate constant of dark adaptation is directly proportional to the fraction of blue membrane (in which Asp-85 is protonated) between pH 2 and 11. The rate constant of isomerization is at least 10(4) times faster in the blue membrane than in the purple membrane. The protonated state of Asp-85 probably is important for the catalysis not only of all-trans <=> 13-cis thermal isomerization during dark adaptation but also of the reisomerization of the chromophore from 13-cis to all-trans configuration during N-->O-->bR transition in the photocycle. This would explain why Asp-85 stays protonated in the N and O intermediates. PMID:8770224

  17. Cation distributions on rapidly solidified cobalt ferrite

    NASA Technical Reports Server (NTRS)

    De Guire, Mark R.; Kalonji, Gretchen; O'Handley, Robert C.

    1990-01-01

    The cation distributions in two rapidly solidified cobalt ferrites have been determined using Moessbauer spectroscopy at 4.2 K in an 8-T magnetic field. The samples were obtained by gas atomization of a Co0-Fe2O3-P2O5 melt. The degree of cation disorder in both cases was greater than is obtainable by cooling unmelted cobalt ferrite. The more rapidly cooled sample exhibited a smaller departure from the equilibrium cation distribution than did the more slowly cooled sample. This result is explained on the basis of two competing effects of rapid solidification: high cooling rate of the solid, and large undercooling.

  18. Sequestering ability of phytate toward biologically and environmentally relevant trivalent metal cations.

    PubMed

    Bretti, Clemente; Cigala, Rosalia Maria; Lando, Gabriele; Milea, Demetrio; Sammartano, Silvio

    2012-08-22

    Quantitative parameters for the interactions between phytate (Phy) and Al(3+), Fe(3+), and Cr(3+) were determined potentiometrically in NaNO(3) aqueous solutions at I = 0.10 mol L(-1) and T = 298.15 K. Different complex species were found in a wide pH range. The various species are partially protonated, depending on the pH in which they are formed, and are indicated with the general formula MH(q)Phy (with 0 ? q ? 6). In all cases, the stability of the FeH(q)Phy species is several log K units higher than that of the analogous AlH(q)Phy and CrH(q)Phy species. For example, for the MH(2)Phy species, the stability trend is log K(2) = 15.81, 20.61, and 16.70 for Al(3+), Fe(3+), and Cr(3+), respectively. The sequestering ability of phytate toward the considered metal cations was evaluated by calculating the pL(0.5) values (i.e., the total ligand concentration necessary to bind 50% of the cation present in trace in solution) at different pH values. In general, phytate results in a quite good sequestering agent toward all three cations in the whole investigated pH range, but the order of pL(0.5) depends on it. For example, at pH 5.0 it is pL(0.5) = 5.33, 5.44, and 5.75 for Fe(3+), Cr(3+), and Al(3+), respectively (Fe(3+) < Cr(3+) < Al(3+)); at pH 7.4 it is pL(0.5) = 9.94, 9.23, and 8.71 (Al(3+) < Cr(3+) < Fe(3+)), whereas at pH 9.0 it is pL(0.5) = 10.42, 10.87, and 8.34 (Al(3+) < Fe(3+) < Cr(3+)). All of the pL(0.5) values, and therefore the sequestering ability, regularly increase with increasing pH, and the dependence of pL(0.5) on pH was modeled using some empirical equations. PMID:22845864

  19. Trimesitylsilylium cation verification of a free silylium cation in solution by NMR chemical shift calculations

    NASA Astrophysics Data System (ADS)

    Kraka, Elfi; Sosa, Carlos P.; Gräfenstein, Jürgen; Cremer, Dieter

    1997-11-01

    NMR chemical shift calculations at the SOS-DFPT/PW91/[9s6p2d/5s4pld/5s4pld/3s]//B3LYP/6-31G(d) level of theory were used to describe the trimesitylsilylium cation 1, recently synthesized in benzene solution and investigated by NMR spectroscopy. The conformation of cation 1 is characterized by mesityl rings rotated by 47° in a propeller-like form. Contrary to other silylium cations investigated, cation 1 forms a weak Van der Waals complex 3 with benzene rather than a Wheland ?-complex. The calculated 29Si NMR chemical shifts for 1 and 3 are 226 and 227 ppm, compared to the experimental value of 225.5 ppm. The agreement between calculated and measured NMR chemical shifts provides evidence that cation 1 presents the first free silylium cation synthesized.

  20. Structural behaviour differences in low methoxy pectin solutions in the presence of divalent cations (Ca(2+) and Zn(2+)): a process driven by the binding mechanism of the cation with the galacturonate unit.

    PubMed

    Assifaoui, Ali; Lerbret, Adrien; Uyen, Huynh T D; Neiers, Fabrice; Chambin, Odile; Loupiac, Camille; Cousin, Fabrice

    2015-01-21

    In this paper, we compare the interactions between low methoxy pectin (LMP) and either Ca(2+) or Zn(2+) in semi-dilute solutions. Intrinsic viscosity and turbidity measurements reveal that pectin-calcium solutions are more viscous, but yet less turbid, than pectin-zinc ones. To get a molecular understanding of the origin of this rather unexpected behavior, we further performed isothermal titration calorimetry, small angle neutron scattering experiments, as well as molecular dynamics simulations. Our results suggest that calcium cations induce the formation of a more homogeneous network of pectin than zinc cations do. The molecular dynamics simulations indicate that this difference could originate from the way the two cations bind to the galacturonate unit (Gal), the main component of LMP: zinc interacts with both carboxylate and hydroxyl groups of Gal, in a similar way to that described in the so-called egg-box model, whereas calcium only interacts with carboxylate groups. This different binding behavior seems to arise from the stronger interaction of water molecules with zinc than with calcium. Accordingly, galacturonate chains are more loosely associated with each other in the presence of Ca(2+) than with Zn(2+). This may improve their ability to form a gel, not only by dimerization, but also by the formation of point-like cross-links. Overall, our results show that zinc binds less easily to pectin than calcium does. PMID:25425418

  1. Observer\\/Kalman Filter Identié cation for Online System Identié cation of Aircraft

    Microsoft Academic Search

    John Valasekand; Wei Chen

    The observer\\/Kalman é lter identié cation method is applied to the problem of online system identié cation of accurate,locallylinear,aircraftdynamicmodelsofnonlinearaircraft.Itisa time-domaintechniquethatidentié esa discreteinput -outputmapping from known inputand outputdata samples,withoutuserimposed a prioriassump- tions about model structure or model order. The basic formulation of observer\\/Kalman é lter identié cation specié c to theaircraftproblem isdeveloped and implementedina nonlinear,six-degree-of-freedom simulation of an AV-8B Harrier. A

  2. Four types of eect modi...cation -a classi...cation based on directed acyclic graphs

    E-print Network

    Four types of e¤ect modi...cation - a classi...cation based on directed acyclic graphs By TYLER J of causal relationships that can give rise to e¤ect modi...cation on the risk di¤erence scale. Directed¤ect modi...er for the causal risk di¤erence concerning two other variables. The directed acyclic graph

  3. Ortho ester-based cleavable cationic surfactants

    Microsoft Academic Search

    Per-Erik Hellberg; Akzo Nobel

    2002-01-01

    A new type of cleavable cationic surfactant, based on the ortho ester link, is described. Ortho ester amines with alkyl chain\\u000a lengths from C8 to C16 were synthesized from a short-chain ortho ester, a fatty alcohol, and an amino acohol. The ortho ester amine was subsequently\\u000a quaternized with methyl chloride, yielding a cationic surfactant. The structures were confirmed by 1H

  4. Dopant titrating ion mobility spectrometry for trace exhaled nitric oxide detection.

    PubMed

    Peng, Liying; Hua, Lei; Li, Enyou; Wang, Weiguo; Zhou, Qinghua; Wang, Xin; Wang, Changsong; Li, Jinghua; Li, Haiyang

    2015-03-01

    Ion mobility spectrometry (IMS) is a promising non-invasive tool for the analysis of exhaled gas and exhaled nitric oxide (NO), a biomarker for diagnosis of respiratory diseases. However, the high moisture in exhaled gas always brings about extra overlapping ion peaks and results in poor identification ability. In this paper, p-benzoquinone (PBQ) was introduced into IMS to eliminate the interference of overlapping ion peaks and realize the selective identification of NO. The overlapping ions caused by moisture were titrated by PBQ and then converted to hydrated PBQ anions (C6H4[Formula: see text](H2O)n). The NO concentration could be determined by quantifying gas phase hydrated nitrite anions (N[Formula: see text](H2O)n), product ions of NO. Under optimized conditions, a limit of detection (LOD) of about 1.4?ppbv and a linear range of 10-200?ppbv were obtained for NO even in 100% relative humidity (RH) purified air. Furthermore, this established method was applied to measure hourly the exhaled NO of eight healthy volunteers, and real-time monitoring the exhaled NO of an esophageal carcinoma patient during radical surgery. These results revealed the potential of the current dopant titrating IMS method in the measurement of exhaled NO for medical disease diagnosis. PMID:25557839

  5. Development of a novel baculovirus titration method using the Enzyme-linked immunosorbent spot (ELISPOT) assay.

    PubMed

    Wang, Wei; Cheng, Tong; Ma, Ke; Xia, Dezhen; Wang, Yongmei; Liu, Jian; Du, Hailian; Shih, James Wai Kuo; Zhang, Jun; Zhao, Qinjian; Xia, Ningshao

    2013-03-01

    The baculovirus expression vector system (BEVS) is one of the most powerful methods for production of recombinant proteins for research or commercial purposes. Titration of viable virus in insect cell culture is often required when BEVS is used for basic research or bioprocessing. An enzyme-linked immunosorbent spot (ELISPOT) assay using monoclonal antibodies against the major capsid protein VP39 of both Autographa californica nuclear polyhedrosis virus (AcMNPV) and Bombyx mori nuclear polyhedrosis virus (BmNPV) was developed for baculovirus quantitation at 48h post-infection. The titer was determined by visualizing infected insect cells as blue spots and automated spot counting was achieved with ELISPOT hardware and software. Log-scale comparison of the results between the ELISPOT assay and a conventional end point dilution assay using a fluorescent marker showed a good correlation for both AcMNPV (R(2)=0.9980, p<0.05) and BmNPV (R(2)=0.9834, p<0.05). In conclusion, a novel, rapid and semi-automated procedure for titrating baculovirus was developed based on the specific immunostaining of infected cells followed by automated spot counting. PMID:23274754

  6. Interaction of gymnemic acid with cyclodextrins analyzed by isothermal titration calorimetry, NMR and dynamic light scattering.

    PubMed

    Izutani, Yusuke; Kanaori, Kenji; Imoto, Toshiaki; Oda, Masayuki

    2005-12-01

    The physiological phenomenon that the antisweet taste effect of gymnemic acid (GA) is diminished by application of gamma-cyclodextrin (gamma-CD) to the mouth was evaluated at the molecular level using isothermal titration calorimetry, NMR and dynamic light scattering. These analyses showed that GA specifically binds to gamma-CD. Thermodynamic analysis using isothermal titration calorimetry revealed that the association constant of GA and gamma-CD is 10(5)-10(6) m(-1) with favorable enthalpy and entropy changes. The heat capacity change was negative and large, despite the change in accessible surface area upon binding being small. These thermodynamics indicate that the binding is dominated by hydrophobic interactions, which is in agreement with inclusion complex formation of gamma-CD. In addition, NMR measurements showed that in solution the spectra of GA are broad and sharpened by the addition of gamma-CD, indicating that unbound GA is in a water-soluble aggregate that is dispersed when it forms a complex with gamma-CD. Dynamic light scattering showed that the average diameter of unbound GA is > 30 nm and that of GA and gamma-CD complex is 2.2 nm, similar to unbound gamma-CD, supporting the aggregate property of GA and the inclusion complexation of GA by gamma-CD. PMID:16302978

  7. Cation-Anion Dual Sensing of a Fluorescent Quinoxalinone Derivative Using Lactam-Lactim Tautomerism.

    PubMed

    Nakane, Yuta; Takeda, Takashi; Hoshino, Norihisa; Sakai, Ken-Ichi; Akutagawa, Tomoyuki

    2015-06-18

    A quinoxalinone derivative capable of lactam-lactim tautomerization was designed as a new fluorescence probe for sensing of cation (M(+) = Li(+) and Na(+)) and anion (X(-) = F(-), Cl(-), Br(-), and CH3COO(-)) in organic solvents. In THF, the minor lactam tautomer exhibited a weak fluorescence band at 425 nm with a typical Stokes shift of ?4400 cm(-1), whereas the major lactim tautomer exhibited an intense fluorescence band at 520 nm with large Stokes shift of ?8900 cm(-1) due to excited-state intramolecular proton transfer (ESIPT). The presence of either cations or anions was found to promote lactim-to-lactam conversion, resulting in the lowering of the ESIPT fluorescence. The lone pairs on the alkylamide oxygen and the quinoxalinone ring nitrogen of the lactam were found to bind Li(+) to form a 1:2 coordination complex, which was confirmed by single crystal X-ray structural analysis and fluorescent titrations. In addition, the N-H bond of the lactam was able to recognize anions via N-H···X hydrogen bonding interactions. Where X = F(-) or CH3COO(-), further addition of these anions caused deprotonation of the lactam to generate an anionic state, consistent with the crystal structure of the anion prepared by mixing tetrabutylammonium fluoride and the quinoxalinone derivative in THF. Dual cation-anion-sensing responses were found to depend on the ion-recognition procedure. The anionic quinoxalinone derivative and its Li(+) complex, which are formed by the addition of CH3COO(-) and Li(+), respectively, displayed different fluorescence enhancement behavior due to the two anions exchanging with each other. PMID:26014712

  8. Potentiometric surface, ground-water withdrawals, and recharge area for the Lisbon aquifer in Alabama, fall 1982

    USGS Publications Warehouse

    Williams, John S.; Planert, Michael; DeJarnette, Sydney S.

    1986-01-01

    The U.S. Geological Survey began a nationwide program in 1978, termed Regional Aquifer-System Analysis (RASA), to study a number of the major aquifer systems that provide a significant part of the country 's water supply. One of the aquifer systems chosen for study was the thick and extensive sequence of sands of Cretaceous and early Tertiary age that underlies the Coastal Plain of the southeastern United States. This system, which extends from Mississippi eastward to South Carolina, is called the Southeastern Coastal Plain aquifer system. It can be divided geohydrologically into several separate aquifers. The map presented, one of a series that portray the potentiometric surface, groundwater withdrawals, and recharge areas for aquifers in Alabama that are included in the regional system, deals with the Lisbon aquifer. (Lantz-PTT)

  9. Data Fusion from Voltammetric and Potentiometric Sensors to Build a Hybrid Electronic Tongue Applied in Classification of Beers

    NASA Astrophysics Data System (ADS)

    Haddi, Zouhair; Amari, Aziz; Bouchikhi, Benachir; Gutiérrez, Juan Manuel; Cetó, Xavier; Mimendia, Aitor; del Valle, Manel

    2011-09-01

    A hybrid electronic tongue based on data fusion of two different sensor families was built and used to recognize three types of beer. The employed sensor array was formed by three modified graphite-epoxy voltammetric sensors plus six potentiometric sensors with cross-sensitivity. The sensors array coupled with feature extraction and pattern recognition methods, namely Principal Component Analysis (PCA) and Discriminant Factor Analysis (DFA), were trained to classify the data clusters related to different beer types. PCA was used to visualize the different categories of taste profiles and DFA with leave-one-out cross validation approach permitted the qualitative classification. According to the DFA model, 96% of beer samples were correctly classified. The aim of this work is to prove performance of hybrid electronic tongue systems by exploiting the new approach of data fusion of different sensor families, in comparison of electronic tongue with only one sensor type.

  10. Shape Preserving Local Histogram Modi cation Vicent Caselles,

    E-print Network

    Caselles, Vicent

    Shape Preserving Local Histogram Modi cation Vicent Caselles, Jose-Luis Lisani ; Jean. A schematic example of the contrast enhancement problem and its solution via histogram modi cation is given of histogram modi cation to improve image contrast. Histogram modi cation, and in particular histogram

  11. Hydrogeology and Potentiometric Surface of the Dublin and Midville Aquifer Systems in Richmond County, Georgia, January 2007

    USGS Publications Warehouse

    Williams, Lester J.

    2007-01-01

    INTRODUCTION The Dublin and Midville aquifer systems are part of the Cretaceous aquifer system that underlies most of Richmond County, Georgia (Gorday, 1985; Falls and others, 1997). The Cretaceous aquifer system is the second most productive aquifer in Georgia and is a major source of water in the region. About 220 million gallons per day (Mgal/d) of water was withdrawn from the Cretaceous aquifer system during 2000 in Georgia (Fanning, 2003). The Augusta-Richmond County Water System is the largest public water supplier in the county and withdrew 13 Mgal/d of ground water during 2000; withdrawals decreased from 2001 to 2005. The towns of Hephzibah and Blythe withdrew 0.4 and 0.03 Mgal/d, respectively. Industrial ground-water withdrawals are concentrated along the Savannah River and totaled 2.89 Mgal/d. To monitor seasonal and long-term water-level fluctuations and trends in the aquifers, the U.S. Geological Survey (USGS) - in cooperation with Augusta Utilities - maintains a countywide network of about 100 water-level monitoring wells in various aquifers, including a new continuous monitoring site (well 30AA33) and two existing USGS-Georgia Environmental Protection Division network sites (wells 29AA09 and 30AA04). Data compiled during this study were used to better define the hydrogeologic units and to construct an updated potentiometric-surface map for the area, which is used to better understand ground-water movement in the Cretaceous aquifer system. In addition, the potentiometric surface and related water-level data can be used for water-resource planning and to update ground-water flow models for the region (Clarke and West, 1997; Cherry, 2006).

  12. Synthesis of piperidides and morpholides of organic acids by reactions of transamidation and study of their repellent activity

    Microsoft Academic Search

    V. I. Latyshev; A. V. Starkov; T. M. Voronkina; V. P. Dremova

    1968-01-01

    The piperidides and morpholides obtained were subjected to quantitative determination by potentiometric titration. For the titration we used the previously described [6,7] method of nonaqueous titration of amides of acids. The samples were titrated potentiometrical ly in acetic anhydride medium with 0.1 N perchloric acid in dioxane. Glass and calomel electrodes were used, the latter being connected to the working

  13. Slow versus standard up-titration of paroxetine for the treatment of depression in cancer patients: a pilot study

    Microsoft Academic Search

    Laura Amodeo; Lorys Castelli; Paolo Leombruni; Daniela Cipriani; Alessia Biancofiore; Riccardo Torta

    Objectives  This study aimed to compare the tolerability and efficacy of two different titrations of paroxetine (slow and standard) in\\u000a a population of cancer patients with depression.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  This randomized open trial included 30 cancer patients with depression (major depressive disorder, dysthymic disorder, or\\u000a adjustment disorder with depressed mood) and aimed to compare the safety of slow up-titration (arm A) versus standard

  14. Additivity of Cation-Interactions: An ab Initio Computational Study on -Cation-Sandwich Complexes

    E-print Network

    Sussman, Joel L.

    Additivity of Cation- Interactions: An ab Initio Computational Study on -Cation- Sandwich Complexes- sandwiches are the sums of the two corresponding TMA- systems. The contribution of electron correlation- sandwiches and to estimate their binding energies. Morokuma decomposition analysis on the binding energy

  15. Coacervation and aggregate transitions of a cationic ammonium gemini surfactant with sodium benzoate in aqueous solution.

    PubMed

    Wang, Ruijuan; Tian, Maozhang; Wang, Yilin

    2014-03-21

    Coacervation in an aqueous solution of cationic ammonium gemini surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (C12C6C12Br2) with sodium benzoate (NaBz) has been investigated at 25 °C by turbidity titration, light microscopy, dynamic light scattering, cryogenic temperature transmission electron microscopy (Cryo-TEM), scanning electron microscopy (SEM), isothermal titration calorimetry, ? potential and (1)H NMR measurements. There is a critical NaBz concentration of 0.10 M, only above which coacervation can take place. However, if the NaBz concentration is too large, coacervation also becomes difficult. Coacervation takes place at a very low concentration of C12C6C12Br2 and exists in a very wide concentration region of C12C6C12Br2. The phase behavior in the NaBz concentration from 0.15 to 0.50 M includes spherical micelles, threadlike micelles, coacervation, and precipitation. With increasing NaBz concentration, the phase boundaries of coacervation shift to higher C12C6C12Br2 concentration. Moreover, the C12C6C12Br2-NaBz aggregates in the coacervate are found to be close to charge neutralized. The Cryo-TEM and SEM images of the coacervate shows a layer-layer stacking structure consisting of a three-dimensional network formed by the assembly of threadlike micelles. Long, dense and almost uncharged threadlike micelles are the precursors of coacervation in the system. PMID:24651935

  16. Survey of the year 2005: literature on applications of isothermal titration calorimetry.

    PubMed

    Ababou, Adessamad; Ladbury, John E

    2007-01-01

    Isothermal titration calorimetry (ITC) can provide a full thermodynamic characterization of an interaction. Its usage does not suffer from constraints of molecular size, shape or chemical constitution. Neither is there any need for chemical modification or attachment to solid support. This ease of use has made it an invaluable instrumental resource and led to its appearance in many laboratories. Despite this, the value of the thermodynamic parameterization has, only quite recently, become widely appreciated. Although our understanding of the correlation between thermodynamic data and structural details continues to be somewhat naïve, a large number of publications have begun to improve the situation. In this overview of the literature for 2005, we have attempted to highlight works of interest and novelty. Furthermore, we draw attention to those works which we feel have provided a route to better analysis and increased our ability to understand the meaning of thermodynamic change on binding. PMID:17006876

  17. Thermodynamic signature of secondary nano-emulsion formation by isothermal titration calorimetry.

    PubMed

    Fotticchia, Iolanda; Fotticchia, Teresa; Mattia, Carlo Andrea; Netti, Paolo Antonio; Vecchione, Raffaele; Giancola, Concetta

    2014-12-01

    The stabilization of oil in water nano-emulsions by means of a polymer coating is extremely important; it prolongs the shelf life of the product and makes it suitable for a variety of applications ranging from nutraceutics to cosmetics and pharmaceutics. To date, an effective methodology to assess the best formulations in terms of thermodynamic stability has yet to be designed. Here, we perform a complete physicochemical characterization based on isothermal titration calorimetry (ITC) compared to conventional dynamic light scattering (DLS) to identify polymer concentration domains that are thermodynamically stable and to define the degree of stability through thermodynamic functions depending upon any relevant parameter affecting the stability itself, such as type of polymer coating, droplet distance, etc. For instance, the method was proven by measuring the energetics in the case of two different biopolymers, chitosan and poly-L-lysine, and for different concentrations of the emulsion coated with poly-L-lysine. PMID:25396753

  18. Binding of chrysoidine to catalase: spectroscopy, isothermal titration calorimetry and molecular docking studies.

    PubMed

    Yang, Bingjun; Hao, Fang; Li, Jiarong; Chen, Dongliang; Liu, Rutao

    2013-11-01

    Chrysoidine is an industrial azo dye and the presence of chrysoidine in water and food has become an environmental concern due to its negative effects on human beings. In this work, the interactions between chrysoidine and bovine liver catalase (BLC) were explored. Obvious loss in catalytic activity was observed after incubation of BLC with chrysoidine, and the inhibition effect of BLC was found to be of the non-competitive type. No profound conformational change of BLC occurs in the presence of chrysoidine as revealed by UV-vis absorption, circular dichroism and fluorescence spectroscopy studies. Isothermal titration calorimetry results indicate that catalase has two sets of binding sites for chrysoidine. Further, molecular docking simulations show that chrysoidine is located within the bottleneck in the main channel of the substrate to the active site of BLC, which explain the activity inhibition of BLC by chrysoidine. PMID:24001681

  19. Substrate binding properties of potato tuber ADP-glucose pyrophosphorylase as determined by isothermal titration calorimetry.

    PubMed

    Cakir, Bilal; Tuncel, Aytug; Green, Abigail R; Koper, Kaan; Hwang, Seon-Kap; Okita, Thomas W; Kang, ChulHee

    2015-06-01

    Substrate binding properties of the large (LS) and small (SS) subunits of potato tuber ADP-glucose pyrophosphorylase were investigated by using isothermal titration calorimetry. Our results clearly show that the wild type heterotetramer (S(WT)L(WT)) possesses two distinct types of ATP binding sites, whereas the homotetrameric LS and SS variant forms only exhibited properties of one of the two binding sites. The wild type enzyme also exhibited significantly increased affinity to this substrate compared to the homotetrameric enzyme forms. No stable binding was evident for the second substrate, glucose-1-phosphate, in the presence or absence of ATP?S suggesting that interaction of glucose-1-phosphate is dependent on hydrolysis of ATP and supports the Theorell-Chance bi bi reaction mechanism. PMID:25953126

  20. DNA heats up : Energetics of genome ejection from phage revealed by isothermal titration calorimetry

    E-print Network

    Jeembaeva, Meerim; Castelnovo, Martin; Evilevitch, Alex

    2010-01-01

    Most bacteriophages are known to inject their double-stranded DNA into bacteria upon receptor binding in an essentially spontaneous way. This downhill thermodynamic process from the intact virion toward the empty viral capsid plus released DNA is made possible by the energy stored during active packaging of the genome into the capsid. Only indirect measurements of this energy have been available until now using either single-molecule or osmotic suppression techniques. In this paper, we describe for the first time the use of isothermal titration calorimetry to directly measure the heat released (or equivalently the enthalpy) during DNA ejection from phage lambda, triggered in solution by a solubilized receptor. Quantitative analyses of the results lead to the identification of thermodynamic determinants associated with DNA ejection. The values obtained were found to be consistent with those previously predicted by analytical models and numerical simulations. Moreover, the results confirm the role of DNA hydrat...

  1. Measuring anaerobic sludge digestion and growth by a simple alkalimetric titration

    SciTech Connect

    Jenkins, S.R.; Morgan, J.M.; Sawyer, C.L.

    1983-05-01

    Organic acids produced in the anaerobic digestion of waste-water sludges tend continuously to depress pH below a point where the acids can be converted to methane. As a result, a large buffering capacity is required to maintain pH between 6.7 and 7.4, which allows efficient operation. Present tests to measure this buffer capacity are inadequate. The present research proposes a simple but adequate test that will provide plant operators with accurate information on anaerobic digester efficiency, as well as considerable long-range insight into digester operation - it would seem that an alkalimetric titration to pH 5.75 can be used routinely to monitor laboratory and actual anaerobic digester performance with a high degree of confidence. The simplicity of the test should encourage many operators to pay more attention to digester performance and, therefore, result in improved waste water treatment efficiency. (Refs. 7).

  2. DNA heats up : Energetics of genome ejection from phage revealed by isothermal titration calorimetry

    E-print Network

    Meerim Jeembaeva; B. Jönsson; Martin Castelnovo; Alex Evilevitch

    2010-01-06

    Most bacteriophages are known to inject their double-stranded DNA into bacteria upon receptor binding in an essentially spontaneous way. This downhill thermodynamic process from the intact virion toward the empty viral capsid plus released DNA is made possible by the energy stored during active packaging of the genome into the capsid. Only indirect measurements of this energy have been available until now using either single-molecule or osmotic suppression techniques. In this paper, we describe for the first time the use of isothermal titration calorimetry to directly measure the heat released (or equivalently the enthalpy) during DNA ejection from phage lambda, triggered in solution by a solubilized receptor. Quantitative analyses of the results lead to the identification of thermodynamic determinants associated with DNA ejection. The values obtained were found to be consistent with those previously predicted by analytical models and numerical simulations. Moreover, the results confirm the role of DNA hydration in the energetics of genome confinement in viral capsids.

  3. Titration without Mixing or Dilution:? Sequential Injection of Chemical Sensing Membranes.

    PubMed

    Holman, D A; Christian, G D; Ruzicka, J

    1997-05-01

    A novel, miniaturized titration was developed using beads 35 ?m in diameter as semisolid aqueous titrant retained in a nonaqueous sample stream. Agarose beads with internally bound pH indicator served as a pH sensing membrane material swollen with aqueous NaOH titrant. The indicator monitored the remaining titrant within the agarose beads during perfusion with H(2)SO(4) in 1-butanol samples. Irreversible reaction of 2 mg bead layers was made possible by automated packing and disposal in a flow cell. This strategy substituted membrane advantages for the burdens of mixing and unnecessary dilution under laminar flow conditions. The agarose environment was conditioned with NaCl to tolerate dissolved salt in the sample. Transmittance measurements were made via fiber optics through FEP PTFE optical windows. A simple inverse relationship held between endpoint volume and acid concentration so that calibration curves were linear, R(2) = 0.9980. PMID:21639300

  4. Probing the binding of (+)-catechin to bovine serum albumin by isothermal titration calorimetry and spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Li, Xiangrong; Hao, Yongbing

    2015-07-01

    In this study, the interaction between (+)-catechin and bovine serum albumin (BSA) was investigated using isothermal titration calorimetry (ITC), in combination with fluorescence spectroscopy, UV-vis absorption spectroscopy, and Fourier transform infrared (FT-IR) spectroscopy. Thermodynamic investigations reveal that the electrostatic interaction and hydrophobic interaction are the major binding forces in the binding of (+)-catechin to BSA. The binding of (+)-catechin to BSA is synergistically driven by enthalpy and entropy. Fluorescence experiments suggest that (+)-catechin can quench the fluorescence of BSA through a static quenching mechanism. The obtained binding constants and the equilibrium fraction of unbound (+)-catechin show that (+)-catechin can be stored and transported from the circulatory system to reach its target organ. Binding site I is found to be the primary binding site for (+)-catechin. Additionally, as shown by the UV-vis absorption, synchronous fluorescence spectroscopy and FT-IR, (+)-catechin may induce conformational and microenvironmental changes of BSA.

  5. Reliability of pulse oximetry in titrating supplemental oxygen therapy in ventilator-dependent patients.

    PubMed

    Jubran, A; Tobin, M J

    1990-06-01

    Pulse oximetry is widely used in the critical care setting, but few studies have examined its usefulness in clinical decision making. One area where pulse oximetry might be useful is in the titration of fractional inspired O2 concentration (FIO2) in ventilator-dependent patients. Unfortunately, documented guidelines for this use do not exist, and in a survey of directors of intensive care units, we found that they employed a wide range of target O2 saturation (SpO2) values. Consequently, we undertook a study to determine if SpO2 could be reliably substituted for measurements of arterial O2 tension (PaO2) when adjusting FIO2 in ventilator-dependent patients. We examined a number of SpO2 target values in 54 critically ill patients aiming for a PaO2 of greater than or equal to 60 mm Hg, while minimizing the risk of O2 toxicity. In white patients, we found that a SpO2 target of 92 percent was reliable in predicting a satisfactory level of oxygenation. However, in black patients, such a SpO2 reading was commonly associated with significant hypoxemia (PaO2 as low as 49 mm Hg), and a higher SpO2 target, 95 percent, was required. In addition, inaccurate oximetry readings (ie, greater than 4 percent difference between SpO2 and direct SaO2 measurements) were more common in black (27 percent) than in white patients (11 percent, p less than 0.05). In conclusion, a SpO2 target of 92 percent was reliable when titrating supplemental O2 in white patients receiving mechanical ventilation; however, in black patients, such a SpO2 reading was commonly associated with significant hypoxemia, and a higher SpO2 target, 95 percent, was required to ensure a satisfactory level of oxygenation. PMID:2347228

  6. Prescribed targets for titration of vasopressors in septic shock: a retrospective cohort study

    PubMed Central

    St-Arnaud, Charles; Éthier, Jean-François; Hamielec, Cindy; Bersten, Andrew; Guyatt, Gordon; Meade, Maureen; Zhou, Qi; Leclair, Marc-André; Patel, Alpesh

    2013-01-01

    Background Without robust clinical evidence to guide titration of vasopressors in septic shock, it is unclear how dosing of these potent medications occurs. We sought to measure the proportion of vasopressor prescriptions for septic shock that were missing explicit targets and to describe the targets that we identified. Methods We conducted a multicentre, retrospective cohort study involving 9 intensive care units (ICUs) located at 3 academic hospitals in Canada and Australia. We reviewed charts of consecutive patients aged 18 years or older who were admitted to the ICU for a presumptive diagnosis of sepsis. Other inclusion criteria were hypotension (systolic arterial pressure ? 90 mm Hg or mean arterial pressure [MAP] ? 65 mm Hg) and continuous infusion of vasopressors for at least 1 hour within the initial 48 hours of ICU stay, the period of observation for this study. Results We included data from 369 patient charts. At least 1 target was specified in 99% of charts. The most common targets were MAP measurements (73%). The median initial MAP target was 65 (range 55–90) mm Hg. In multivariable regression models, hospital site and older age of the patient, but not comorbidities of the patient, were associated with MAP targets. In 40% of patients, the treating team modified the initial target at least once. Interpretation This study suggests that an explicit blood pressure target accompanies nearly every vasopressor prescription and that patient characteristics have little influence on its value. Identification of a titration strategy that will maximize benefit and minimize harm constitutes a research priority. PMID:25077114

  7. Titrating matching-to-sample performance in pigeons: effects of diazepam, morphine, and cholinergic agents.

    PubMed

    Wenger, G R; Hudzik, T J; Wright, D W

    1993-10-01

    Five adult, male White Carneau pigeons were trained to respond under a titrating matching-to-sample schedule of reinforcement. Under this titration schedule, each trial began with the presentation of a sample stimulus (red or green light) on the center key of a three-key pigeon chamber. Completion of 15 responses on the center key resulted in the termination of the stimulus presentation and the initiation of a delay period. The length of the delay changed as a function of the pigeon's performance. During the first five trials of each session, the delay was fixed at 3 s in length. On the sixth and all subsequent trials, the length of the delay was either increased, did not change, or decreased such that accuracy was maintained at approximately 80%. Following the delay, two of the three pigeon keys were transilluminated with different colored lights (red or green). A single response upon the key transilluminated with the same stimulus color as the sample stimulus resulted in the presentation of food. A response on the key transilluminated with the stimulus color that did not match the sample stimulus resulted in a time-out period. Using this procedure, the effects of two drugs of abuse, diazepam (0.03-3 mg/kg) and morphine (0.03-10 mg/kg), a muscarinic antagonist, scopolamine (0.003-0.3 mg/kg), the quaternary derivative of scopolamine, methylscopolamine (0.003-0.3 mg/kg), a cholinesterase inhibitor, physostigmine (0.003-0.1 mg/kg), and the quaternary derivative of physostigmine, neostigmine (0.003-0.1 mg/kg), were determined. Diazepam decreased matching accuracy such that a decrease in the mean delay value for the session was observed.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8265699

  8. In vitro retention of a new thermoplastic titratable mandibular advancement device.

    PubMed

    Braem, Marc

    2015-01-01

    Oral appliance (OA) therapy with a mandibular advancement device (OAm) is a non-invasive, alternative approach to maintaining upper airway patency. The main requirement for an OAm to be effective is the adequate retention on the teeth while the patient is asleep. We evaluated the retentive forces of a new low-cost, customizable, titratable, thermoplastic OAm (BluePro (®); BlueSom, France). Dental impressions and casts were made for one patient with complete upper and lower dental arches including the third molars and class II bite proportions. A setup based on Frasaco ANA-4 models was also used. Two protrusive positions of the mandible were investigated: 3 mm and 8 mm, representing respectively 25% and 65% of the maximal protrusion. The forces required to remove the BluePro (®) device from the carriers were recorded continuously over 730 cycles (=365 days, twice a day) to simulate 1 year of clinical use. At 8 mm protrusion the BluePro (®) device showed retentive forces of ~27N. There was a slight but non-significant decrease in retentive forces in the tests on the epoxified carriers which was not found on the ANA-4 carriers. There were no significant differences between the carriers as a function of protrusion. The BluePro (®) device tested in the present study possesses sufficient retention forces to resist initial jaw opening forces and full mouth opening forces estimated to be ~20N. It could therefore broaden the indications for use of thermoplastic OAms. It could provide a temporary OAm while a custom-made OAm is being manufactured or repaired. Patients could be provided with a low-cost try-out device capable of reliable titration, providing an indication of effectiveness and of patient acceptance of an OAm, although the effect of device shape and size on therapeutic outcome is not yet known. Finally it could provide an affordable OAm solution in resource-restricted healthcare settings. PMID:25901281

  9. Heparin and Protamine Titration Does Not Improve Haemostasis after Cardiac Surgery: A Prospective Randomized Study

    PubMed Central

    Radulovic, Vladimir; Laffin, Anna; Hansson, Kenny M.; Backlund, Erika; Baghaei, Fariba; Jeppsson, Anders

    2015-01-01

    Background Bleeding complications are common in cardiac surgery. Perioperative handling of heparin and protamine may influence the haemostasis. We hypothesized that heparin and protamine dosing based on individual titration curves would improve haemostasis in comparison to standard dosing. Subjects and Methods Sixty patients scheduled for first time elective coronary artery bypass grafting or valve surgery were included in a prospective randomized study. The patients were randomized to heparin and protamine dosing with Hepcon HMS Plus device or to standard weight and activated clotting time (ACT) based dosing. Blood samples were collected before and 10 minutes, 2 hours and 4 hours after cardiopulmonary bypass. Primary endpoint was endogenous thrombin potential in plasma 2 hours after surgery as assessed by calibrated automated thrombography. Secondary endpoints included total heparin and protamine doses, whole blood clot formation (thromboelastometry) and post-operative bleeding volume and transfusions. Heparin effect was assessed by measuring anti-Xa activity. Results Endogenous thrombin potential and clot formation deteriorated in both groups after surgery without statistically significant intergroup difference. There were no significant differences between the groups in total heparin and protamine doses, heparin effect, or postoperative bleeding and transfusions at any time point. Significant inverse correlations between anti-Xa activity and endogenous thrombin potential were observed 10 min (r = -0.43, p = 0.001), 2 hours (r = -0.66, p<0.001) and 4 hours after surgery (r = -0.58, p<0.001). Conclusion In conclusion, the results suggest that perioperative heparin and protamine dosing based on individual titration curves does not improve haemostasis after cardiac surgery. Postoperative thrombin generation capacity correlates to residual heparin effect. Trial Registration www.isrctn.com ISRCTN14201041. PMID:26134993

  10. Use of Complementary Cation And Anion Heavy Atom-Atom Salt Derivatives to Solve the Structure of Cytochrome P450 46a1

    SciTech Connect

    White, M.A.; Mast, N.; Bjorkhem, I.; Johnson, E.F.; Stout, C.D.; Pikuleva, I.A.

    2009-05-26

    Human cytochrome P450 46A1 (CYP46A1) is one of the key enzymes in cholesterol homeostasis in the brain. The crystallization and heavy-atom structure solution of an active truncated CYP46A1 in complex with the high-affinity substrate analogue cholesterol-3-sulfate (CH-3S) is reported. The 2.6 {angstrom} structure of CYP46A1-CH-3S was solved using both anion and cation heavy-atom salts. In addition to the native anomalous signal from the haem iron, an NaI anion halide salt derivative and a complementary CsCl alkali-metal cation salt derivative were used. The general implications of the use of halide and alkali-metal quick soaks are discussed. The importance of using isoionic strength buffers, the titration of heavy-atom salts into different ionic species and the role of concentration are considered. It was observed that cation/anion-binding sites will occasionally overlap, which could negatively impact upon mixed RbBr soaks used for multiple anomalous scatterer MAD (MMAD). The use of complementary cation and anion heavy-atom salt derivatives is a convenient and powerful tool for MIR(AS) structure solution.

  11. Cationically polymerizable monomers derived from renewable sources

    SciTech Connect

    Crivello, J.V.

    1991-10-01

    The objective of this project is to make use of products obtained from renewable plant sources as monomers for the direct production of polymers which can be used for a wide range of plastic applications. In this report is described progress in the synthesis and polymerization of cationically polymerizable monomers and oligomers derived from botanical oils, terpenes, natural rubber, and lignin. Nine different botanical oils were obtained from various sources, characterized and then epoxidized. Their photopolymerization was carried out using cationic photoinitiators and the mechanical properties of the resulting polymers characterized. Preliminary biodegradation studies are being conducted on the photopolymerized films from several of these oils. Limonene was cationically polymerized to give dimers and the dimers epoxidized to yield highly reactive monomers suitable for coatings, inks and adhesives. The direct phase transfer epoxidation of squalene and natural rubber was carried out. The modified rubbers undergo facile photocrosslinking in the presence of onium salts to give crosslinked elastomers. 12 refs., 3 figs., 10 tabs.

  12. Cationic acrylamide emulsion polymer brine thickeners

    SciTech Connect

    Gleason, P.A.; Piccoline, M.A.

    1986-12-02

    This patent describes a thickened, solids free, aqueous drilling and servicing brine having a density of at least 14.4 ppg. comprising (a) an aqueous solution of at least one water-soluble salt of a multivalent metal, and (b) a cationic water-in-oil emulsion polymer of acrylamide or methacrylamide and a cationic monomer selected from the group consisting of a dialkylaminoalkyl acrylamide or methacrylamide, a trialkylaminoalkyl acrylamide or methacrylamide, a trialkylaminoalkyl acrylate or methacrylate, and a dialkyldialkyl ammonium halide. The acrylamide or methacrylamide to cationic monomer molar ratio of the polymer is about 70:30 to 95:5, the polymer having an I.V. in 1.0N KCl of about 1.0 to 7.0 dl/g and being present in a compatible and viscosifying amount; the thickened brine characterized by being substantially non-dilatent.

  13. Map showing the difference between the potentiometric surfaces of the Magothy Aquifer of September 1975 and September 1982 in southern Maryland

    USGS Publications Warehouse

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

    1982-01-01

    A map was prepared that shows the net change in the potentiometric surface of the Magothy aquifer in southern Maryland from September 1975 to September 1982. The map is based on measurements from a network of 55 observation wells. During the 8-year period, the potentiometric surface was (1) lowered by at least a few feet throughout the entire southern Maryland area , (2) lowered by at least 10 feet in the southern half of the area, and (3) lowered by 30 to 40 feet in most of northern Charles County. The network of observation 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)

  14. Determination of nitrogen dioxide, sulfur dioxide, ozone, and ammonia in ambient air using the passive sampling method associated with ion chromatographic and potentiometric analyses

    Microsoft Academic Search

    Alaa A. Salem; Ahmed A. Soliman; Ismail A. El-Haty

    2009-01-01

    Concentrations of nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and ammonia (NH3) were determined in the ambient air of Al-Ain city over a year using the passive sampling method associated with ion chromatographic\\u000a and potentiometric detections. IVL samplers were used for collecting nitrogen and sulfur dioxides whereas Ogawa samplers were\\u000a used for collecting ozone and ammonia. Five sites representing

  15. Thermal behavior of Belousov-Zhabotinskii reactions with Ce(IV) salts measured by heat exchange calorimetry of flow type involving simultaneous observation of potentiometric oscillations

    Microsoft Academic Search

    Shuko Fujieda; Wei Zhang

    1995-01-01

    Thermal and potentiometric oscillations of Belousov-Zhabotinskii reactions catalyzed by Ce(IV) salt were simultaneously observed in a continuously stirred tank reactor. A heat exchange calorimeter of flow type was assembled. An Ag-AgBr electrode and one end of salt bridge were incorporated in the sample and reference vessels. Three kinds of stock solutions in 0.200 M sulfuric acid were used in typical

  16. Second order global analysis: the evaluation of series of spectrophotometric titrations for improved determination of equilibrium constants

    Microsoft Academic Search

    Raylene M. Dyson; Susan Kaderli; Geoffrey A. Lawrance; Marcel Maeder

    1997-01-01

    In spectrophotometric titrations, linear or near-linear dependence of concentration profiles and the existence of minor species cause difficulties in the evaluation of the data. In the first case calculated absorption spectra and in the second case the corresponding equilibrium constants are not or only poorly defined. The result is the inability to reliably fit a reasonable model to the data.

  17. Isothermal titration calorimetry and differential scanning calorimetry as complementary tools to investigate the energetics of biomolecular recognition

    Microsoft Academic Search

    Ilian Jelesarov; Hans Rudolf Bosshard

    1999-01-01

    The principles of isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) are reviewed together with the basic thermodynamic formalism on which the two techniques are based. Although ITC is particularly suitable to follow the energetics of an association reaction between biomolecules, the combination of ITC and DSC provides a more comprehensive description of the thermodynamics of an associating system.

  18. Kinetic properties of two Rhizopus exo-polygalacturonase enzymes hydrolyzing galacturonic acid oligomers using isothermal titration calorimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The kinetic characteristics of two Rhizopus oryzae exo-polygalacturonases acting on galacturonic acid oligomers (GalpA) were determined using isothermal titration calorimetry (ITC). RPG15 hydrolyzing (GalpA)2 demonstrated a Km of 55 uM and kcat of 10.3 s^-1^ while RPG16 was shown to have greater af...

  19. MODIFICATION OF THE IODIMETRIC TITRATION METHOD FOR THE DETERMINATION OF BROMIDE AND ITS APPLICATION TO MIXED DOMESTIC - INDUSTRIAL WASTE EFFLUENTS

    EPA Science Inventory

    The iodimetric titration method for the determination of bromide involves the observation of various color changes, making the method unsuitable for use with samples that are highly colored. A modification is described, which extends the usefulness of the method to highly colored...

  20. 3-D Surface Visualization of pH Titration "Topos": Equivalence Point Cliffs, Dilution Ramps, and Buffer Plateaus

    ERIC Educational Resources Information Center

    Smith, Garon C.; Hossain, Md Mainul; MacCarthy, Patrick

    2014-01-01

    3-D topographic surfaces ("topos") can be generated to visualize how pH behaves during titration and dilution procedures. The surfaces are constructed by plotting computed pH values above a composition grid with volume of base added in one direction and overall system dilution on the other. What emerge are surface features that…

  1. Isothermal Titration Calorimetric Study of RNase-A Kinetics (cCMP ? 3'CMP) Involving EndProduct Inhibition

    Microsoft Academic Search

    Shawn D. Spencer; Robert B. Raffa

    2004-01-01

    Purpose. Isothermal titration calorimetry (ITC) and progress curve analysis was used to measure the enzyme kinetic parameters (KM and kcat) of the hydrolysis of cCMP by RNase-A, a reaction that includes end-product competitive inhibition by 3'-CMP.

  2. Use of chicken cell line LSCC-H32 for titration of animal viruses and exogenous chicken interferon.

    PubMed Central

    Roth, S; Kaaden, O R

    1985-01-01

    The chicken embryo cell line LSCC-H32 was tested for the propagation and titration of several animal viruses of the families Toga-, Reo-, Rhabdo-, Herpeto-, Orthomyxo-, Paramyxo-, and Poxviridae and compared with secondary chicken embryo cells. The LSCC-H32 cells were demonstrated to be as susceptible for most of the tested viruses as were secondary chicken embryo cells. Both produced comparably sized virus plaques. The titers of Sindbis and Semliki Forest viruses in LSCC-H32 cells were 5- to 40-fold higher than in secondary chicken embryo cells or BHK-21 cells, respectively. Furthermore, exogenous chicken standard interferon was titrated in the LSCC-H32 cells, and a 50% plaque titer reduction of the challenging vesicular stomatitis virus was achieved by 0.12 IU of a standard chicken interferon preparation. Endogenous chicken interferon could not be induced by treatment of the cells with polyinosinic acid-polycytidylic acid. Due to its high plating efficiency and metabolic activities, the LSCC-H32 cell line provides a useful cell system for the titration and large-scale production of the tested animal viruses and for the titration of exogenous chicken interferon. PMID:2581511

  3. A simple and rapid Hepatitis A Virus (HAV) titration assay based on antibiotic resistance of infected cells: evaluation of the HAV neutralization potency of human immune globulin preparations

    Microsoft Academic Search

    Krishnamurthy Konduru; Maria Luisa Virata-Theimer; Mei-ying W Yu; Gerardo G Kaplan

    2008-01-01

    BACKGROUND: Hepatitis A virus (HAV), the causative agent of acute hepatitis in humans, is an atypical Picornaviridae that grows poorly in cell culture. HAV titrations are laborious and time-consuming because the virus in general does not cause cytopathic effect and is detected by immunochemical or molecular probes. Simple HAV titration assays could be developed using currently available viral construct containing

  4. Synthetic cationic antimicrobial peptides bind with their hydrophobic parts to drug site II of human serum albumin

    PubMed Central

    2014-01-01

    Background Many biologically active compounds bind to plasma transport proteins, and this binding can be either advantageous or disadvantageous from a drug design perspective. Human serum albumin (HSA) is one of the most important transport proteins in the cardiovascular system due to its great binding capacity and high physiological concentration. HSA has a preference for accommodating neutral lipophilic and acidic drug-like ligands, but is also surprisingly able to bind positively charged peptides. Understanding of how short cationic antimicrobial peptides interact with human serum albumin is of importance for developing such compounds into the clinics. Results The binding of a selection of short synthetic cationic antimicrobial peptides (CAPs) to human albumin with binding affinities in the ?M range is described. Competitive isothermal titration calorimetry (ITC) and NMR WaterLOGSY experiments mapped the binding site of the CAPs to the well-known drug site II within subdomain IIIA of HSA. Thermodynamic and structural analysis revealed that the binding is exclusively driven by interactions with the hydrophobic moieties of the peptides, and is independent of the cationic residues that are vital for antimicrobial activity. Both of the hydrophobic moieties comprising the peptides were detected to interact with drug site II by NMR saturation transfer difference (STD) group epitope mapping (GEM) and INPHARMA experiments. Molecular models of the complexes between the peptides and albumin were constructed using docking experiments, and support the binding hypothesis and confirm the overall binding affinities of the CAPs. Conclusions The biophysical and structural characterizations of albumin-peptide complexes reported here provide detailed insight into how albumin can bind short cationic peptides. The hydrophobic elements of the peptides studied here are responsible for the main interaction with HSA. We suggest that albumin binding should be taken into careful consideration in antimicrobial peptide studies, as the systemic distribution can be significantly affected by HSA interactions. PMID:24456893

  5. Process and apparatus for the production of Bi-213 cations

    DOEpatents

    Horwitz, E.P.; Hines, J.J.; Chiarizia, R.; Dietz, M.

    1998-12-29

    A process for producing substantially impurity-free Bi-213 cations is disclosed. An aqueous acid feed solution containing Ac-225 cations is contacted with an ion exchange medium to bind the Ac-225 cations and form an Ac-225-laden ion exchange medium. The bound Ac-225 incubates on the ion exchange medium to form Bi-213 cations by radioactive decay. The Bi-213 cations are then recovered from the Ac-225-laden ion exchange medium to form a substantially impurity-free aqueous Bi-213 cation acid solution. An apparatus for carrying out this process is also disclosed. 7 figs.

  6. Restructuring of a Peat in Interaction with Multivalent Cations: Effect of Cation Type and Aging Time

    PubMed Central

    Kunhi Mouvenchery, Yamuna; Jaeger, Alexander; Aquino, Adelia J. A.; Tunega, Daniel; Diehl, Dörte; Bertmer, Marko; Schaumann, Gabriele Ellen

    2013-01-01

    It is assumed to be common knowledge that multivalent cations cross-link soil organic matter (SOM) molecules via cation bridges (CaB). The concept has not been explicitly demonstrated in solid SOM by targeted experiments, yet. Therefore, the requirements for and characteristics of CaB remain unidentified. In this study, a combined experimental and molecular modeling approach was adopted to investigate the interaction of cations on a peat OM from physicochemical perspective. Before treatment with salt solutions of Al3+, Ca2+ or Na+, respectively, the original exchangeable cations were removed using cation exchange resin. Cation treatment was conducted at two different values of pH prior to adjusting pH to 4.1. Cation sorption is slower (>>2 h) than deprotonation of functional groups (<2 h) and was described by a Langmuir model. The maximum uptake increased with pH of cation addition and decreased with increasing cation valency. Sorption coefficients were similar for all cations and at both pH. This contradicts the general expectations for electrostatic interactions, suggesting that not only the interaction chemistry but also spatial distribution of functional groups in OM determines binding of cations in this peat. The reaction of contact angle, matrix rigidity due to water molecule bridges (WaMB) and molecular mobility of water (NMR analysis) suggested that cross-linking via CaB has low relevance in this peat. This unexpected finding is probably due to the low cation exchange capacity, resulting in low abundance of charged functionalities. Molecular modeling demonstrates that large average distances between functionalities (?3 nm in this peat) cannot be bridged by CaB-WaMB associations. However, aging strongly increased matrix rigidity, suggesting successive increase of WaMB size to connect functionalities and thus increasing degree of cross-linking by CaB-WaMB associations. Results thus demonstrated that the physicochemical structure of OM is decisive for CaB and aging-induced structural reorganisation can enhance cross-link formation. PMID:23750256

  7. AMDTreat 5.0+ with PHREEQC titration module to compute caustic chemical quantity, effluent quality, and sludge volume

    USGS Publications Warehouse

    Cravotta, Charles; Means, Brent P; Arthur, Willam; McKenzie, Robert M; Parkhurst, David L.

    2015-01-01

    Alkaline chemicals are commonly added to discharges from coal mines to increase pH and decrease concentrations of acidity and dissolved aluminum, iron, manganese, and associated metals. The annual cost of chemical treatment depends on the type and quantities of chemicals added and sludge produced. The AMDTreat computer program, initially developed in 2003, is widely used to compute such costs on the basis of the user-specified flow rate and water quality data for the untreated AMD. Although AMDTreat can use results of empirical titration of net-acidic or net-alkaline effluent with caustic chemicals to accurately estimate costs for treatment, such empirical data are rarely available. A titration simulation module using the geochemical program PHREEQC has been incorporated with AMDTreat 5.0+ to improve the capability of AMDTreat to estimate: (1) the quantity and cost of caustic chemicals to attain a target pH, (2) the chemical composition of the treated effluent, and (3) the volume of sludge produced by the treatment. The simulated titration results for selected caustic chemicals (NaOH, CaO, Ca(OH)2, Na2CO3, or NH3) without aeration or with pre-aeration can be compared with or used in place of empirical titration data to estimate chemical quantities, treated effluent composition, sludge volume (precipitated metals plus unreacted chemical), and associated treatment costs. This paper describes the development, evaluation, and potential utilization of the PHREEQC titration module with the new AMDTreat 5.0+ computer program available at http://www.amd.osmre.gov/.

  8. Aluminium substitution in iron(II-III)-layered double hydroxides: Formation and cationic order

    SciTech Connect

    Ruby, Christian [Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME UMR7564 CNRS-Nancy Universite, 405 rue de Vandoeuvre, 54600 Villers-les-Nancy (France)], E-mail: Christian.ruby@lcpme.cnrs-nancy.fr; Abdelmoula, Mustapha; Aissa, Rabha [Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, LCPME UMR7564 CNRS-Nancy Universite, 405 rue de Vandoeuvre, 54600 Villers-les-Nancy (France); Medjahdi, Ghouti [Laboratoire de Chimie du Solide Mineral, LCSM UMR 7555 CNRS-Nancy Universite, Faculte des Sciences, BP239, 54506 Vandoeuvre-les-Nancy (France); Brunelli, Michela [European Synchrotron Radiation Facility (ESRF), 6 rue Jules Horowitz, BP 220, 38043 Grenoble Cedex (France); Francois, Michel [Laboratoire de Chimie du Solide Mineral, LCSM UMR 7555 CNRS-Nancy Universite, Faculte des Sciences, BP239, 54506 Vandoeuvre-les-Nancy (France)

    2008-09-15

    The formation and the modifications of the structural properties of an aluminium-substituted iron(II-III)-layered double hydroxide (LDH) of formula Fe{sub 4}{sup II}Fe{sub (2-6y)}{sup III}Al{sub 6y}{sup III} (OH){sub 12} SO{sub 4}, 8H{sub 2}O are followed by pH titration curves, Moessbauer spectroscopy and high-resolution X-ray powder diffraction using synchrotron radiation. Rietveld refinements allow to build a structural model for hydroxysulphate green rust, GR(SO{sub 4}{sup 2-}), i.e. y=0, in which a bilayer of sulphate anions points to the Fe{sup 3+} species. A cationic order is proposed to occur in both GR(SO{sub 4}{sup 2-}) and aluminium-substituted hydroxysulphate green rust when y<0.08. Variation of the cell parameters and a sharp decrease in average crystal size and anisotropy are detected for an aluminium content as low as y=0.01. The formation of Al-GR(SO{sub 4}{sup 2-}) is preceded by the successive precipitation of Fe{sup III} and Al{sup III} (oxy)hydroxides. Adsorption of more soluble Al{sup III} species onto the initially formed ferric oxyhydroxide may be responsible for this slowdown of crystal growth. Therefore, the insertion of low aluminium amount (y{approx}0.01) could be an interesting way for increasing the surface reactivity of iron(II-III) LDH that maintains constant the quantity of the reactive Fe{sup II} species of the material. - Graphical abstract: (a) Crystallographical structure of sulphated green rust: SO{sub 4}{sup 2-} point to the Fe{sup 3+} cations (red) that form an ordered array with the Fe{sup 2+} cations (green). (b) Width and asymmetry of the synchrotron XRD peaks increase rapidly when some Al{sup 3+} species substitute the Fe{sup 3+} cations; z is molar ratio Al{sup 3+}/Fe{sup 3+}.

  9. Algebraic Process Veri cation J. F. Groote

    E-print Network

    Reniers, Michel

    in Handbook of Process Algebra, editors A. Ponse and S. Smolka, Elsevier Science Publishers B.V. 1 #12; 1Algebraic Process Veri#12;cation J. F. Groote CWI, P.O. Box 94079, NL-1090 GB Amsterdam from an explicit process algebraic standpoint. This means that all calculations are based on the axioms

  10. Viscoelastic cationic polymers containing the urethane linkage

    NASA Technical Reports Server (NTRS)

    Rembaum, A. (inventor)

    1972-01-01

    A method for the synthesis and manufacturing of elastomeric compositions and articles containing quaternary nitrogen centers and condensation residues along the polymeric backbone of the centers is presented. Linear and cross-linked straight chain and block polymers having a wide damping temperature range were synthesized. Formulae for the viscoelastic cationic polymers are presented.

  11. Removal of cationic dyes by kaolinite

    Microsoft Academic Search

    M. Hamdi Karao?lu; Mehmet Do?an; Mahir Alkan

    2009-01-01

    The removal of cationic dyes such as maxilon yellow 4GL (MY 4GL) and maxilon red GRL (MR GRL) on kaolinite from aqueous solutions has been studied according to the adsorption method. The adsorbed amount of dyes on kaolinite surface was investigated as a function of pH, ionic strength, temperature, acid activation, and calcination temperature. It was found that: (i) the

  12. The 9-homocubyl cation rearrangement revisited.

    PubMed

    Jalife, Said; Wu, Judy I-Chia; Martínez-Guajardo, Gerardo; von Ragué Schleyer, Paul; Fernández-Herrera, María A; Merino, Gabriel

    2015-03-28

    Complexity of the potential energy surface of the 9-homocubyl cation is revealed by Born-Oppenheimer molecular dynamics simulations and high ab initio levels. The stereospecific automerizations observed experimentally involve bridged ions, which have either an aromatic or an anti-aromatic character. New pathways leading to more stable isomers are unveiled. PMID:25370742

  13. ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS

    EPA Science Inventory

    The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. The sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaCl,...

  14. ADSORPTION OF ORGANIC CATIONS TO NATURAL MATERIALS

    EPA Science Inventory

    The factors that control the extent of adsorption of amphiphilic organic cations on environmental and pristine surfaces have been studied. he sorbents were kaolinite, montmorillonite, two aquifer materials, and a soil; solutions contained various concentrations of NaCl and CaC12,...

  15. Cationic Hyperbranched Poly(amino ester): A Novel Class of DNA Condensing Molecule with Cationic

    E-print Network

    Park, Jong-Sang

    * School of Chemistry & Molecular Engineering Seoul National UniVersity, Seoul 151-742, Korea Recei to that of other cationic polymers is due to the "endosome buffering" or "proton sponge" effect of the polymers

  16. Measurement of atmospheric OH by titration of near-IR fluorescent dyes

    NASA Technical Reports Server (NTRS)

    Betterton, Eric A.; Gast, Karl

    1994-01-01

    Recent research has shown that certain polymethine dyes can be detected at ultratrace levels (greater than or equal to 6x10(exp -14) M) in solution by fluorimetry. These detection limits are possible because of the inherent sensitivity of fluorescence techniques, because the dyes fluoresce in the near infrared region where background interference is negligible, and because powerful infrared diode lasers are now available to improve the signal to noise ratio. Other work has shown that the hydroxyl radical destroys the ability of polymethine dyes to fluoresce. These observations form the basis for a new hydroxyl radical detector that is essentially a fluorometric titrator. Theoretically, the detector should show an acceptable sensitivity and response time. Assuming that the atmospheric HO concentration is about 10(exp -11) moles m(exp -3) (i.e. 10(exp 6) molecules cm(exp -3)), then 10 L of air 'titrated' with 20 mL of 10(exp -11) M dye solution (an easily detected concentration) should result in a drop in the fluorescent signal of 50 percent - a readily detectable change. At a flow rate of 3 L min(exp -1) the sampling time would be 3 minutes. The biggest potential problem is selectivity: other oxidants may also cause the fluorescence signal to be lost. The chemistry of polymethine dyes has not been studied in detail and so no quantitative data are available. However, a survey of the literature suggests that in general HO should react up to six orders of magnitude faster than HO2 and other radicals such as RO2 and RO. It should also react much more rapidly than H2O2 and O3. Thus it may be possible to discriminate kinetically against potential interfering substances. It was shown in the laboratory that 10(exp -4) M H2O2 has little effect on the absorption spectrum of the dye IR125 over a period of hours but that the band at 780 nm is slowly lost in water over a period of days even under argon in the dark. By contrast, DMSO solutions of IR125 are stable.

  17. Cation-cation interactions, magnetic communication and reactivity of the pentavalent uraniumion [U(NR)2]+

    SciTech Connect

    Spencer, Liam P [Los Alamos National Laboratory; Schelter, Eric J [Los Alamos National Laboratory; Boncella, James M [Los Alamos National Laboratory; Yang, Ping [Los Alamos National Laboratory; Gsula, Robyn L [NON LANL; Scott, Brian L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Kiplinger, Jacqueline L [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory

    2009-01-01

    The dimeric bis(imido) uranium complex [{l_brace}U(NtBu)2(I)(tBu2bpy){r_brace}2] (see picture; U green, N blue, I red) has cation-cation interactions between [U(NR)2]+ ions. This f1-f1 system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

  18. Role of cation exchange processes on the sorption influenced transport of cationic ?-blockers in aquifer sediments.

    PubMed

    Schaffer, Mario; Börnick, Hilmar; Nödler, Karsten; Licha, Tobias; Worch, Eckhard

    2012-11-01

    The influence of cation exchange processes on the transport behavior of the cationic ?-blockers atenolol and metoprolol was investigated by applying saturated laboratory column experiments. Breakthrough curves using natural sediments under different competitive conditions were generated and resulting sorption coefficients were compared. For the cationic species of atenolol (at pH = 8), the existence and dominating role of cation exchange processes were demonstrated by varying calcium concentrations. No effect of atenolol concentration on its retardation was observed within a wide concentration range. The breakthrough curve comparison of atenolol and the more hydrophobic metoprolol under constant conditions showed a significantly stronger retardation for metoprolol than for atenolol. However, additional non-polar interactions cannot explain the observed differences as they are determined to be negligible for both compounds. Due to the dominating role of cation exchange processes for the cationic species on overall sorption, a simple prediction of ?-blocker transport in the subsurface by using K(OC) values derived from log K(OW)-log K(OC) correlations is not feasible. PMID:22884374

  19. Characterization of a lipophilic plasmid DNA condensate formed with a cationic peptide fatty acid conjugate.

    PubMed

    Do, Trinh T; Tang, Vicky J; Aguilera, Joe A; Perry, Christopher C; Milligan, Jamie R

    2011-05-01

    In the presence of cationic ligands, DNA molecules can become aggregated into larger particles in a process known as condensation. DNA condensates are of interest as models for the dense packing found in naturally occurring structures such as phage heads and chromatin. They have found extensive application in DNA transfection and also provide convenient models with which to study DNA damage by the direct effect of ionizing radiation. Further, conjugates of cationic peptides with fatty acids may represent a class of attractive ligands for these areas because of their simple synthesis. When plasmid pUC18 is used as the DNA target and N-caproyl-penta-arginine amide (Cap-R(5)-NH(2)) is used as the ligand, the physical properties of the resulting mixtures were characterized using static and dynamic light scattering, sedimentation, dye exclusion, circular dichroism, nanoparticle tracking, and atomic force microscopy. Their chemical properties were assayed using solvent extraction and protection against hydroxyl radical attack and nuclease digestion. Titration of the plasmid with the Cap-R(5)-NH(2) ligand produced sharply defined changes in both chemical and physical properties, which was associated with the formation of condensed DNA particles in the 100-2000 nm size range. The caproyl group at the ligand's N-terminus produced a large increase in the partitioning of the resulting condensate from water into chloroform and in its binding to the neutral detergent Pluronic F-127. Both the physical and chemical data were all consistent with condensation of the plasmid by the ligand where the presence in the ligand of the caproyl group conferred an extensive lipophilic character upon the condensate. PMID:21410151

  20. Thermodynamic functions of Ni(II) complexes with 5-(2-hydroxyphenyl)-pyrazole derivatives. A potentiometric study

    NASA Astrophysics Data System (ADS)

    Deosarkar, S. D.; Narwade, M. L.; Thakre, V. J.

    2013-10-01

    Proton-ligand dissociation constants of five biologically important pyrazole derivatives, viz. [5-(2-hydroxyphenyl)-3-(pyridin-3-yl)-4-benzoyl]-pyrazol (HPPBP), [5-(2-hydroxyphenyl)-3-(3-nitrophenyl)-4-(3-pyridinoyl)]-pyrazol (HPNPPP), [5-(2-hydroxyphenyl)-3-(3-nitrophenyl)-4-benzoyl]-pyrazol (HPNPBP), [5-(2-hydroxyphenyl)-3-phenyl-4-(3-pyridinoyl)]-pyrazol (HPPPP), and [5-(2-hydroxyphenyl)-3-(3-nitrophenyl)-4-(2-furoyl) pyrazol (HPNPFP) and metal ligand stability constants of their Ni(II) complexes in 70% (v/v) dioxane-water and 0.1 M KNO3 were determined at 298.15, 303.15, and 308.15 K by potentiometric method. Thermodynamic functions, such as, free energy change (? G ?), enthalpy change (? H ?) and entropy (? S ?) change for dissociation and complex formation have been estimated form temperature dependence of proton-ligand and metal-ligand stability constants and interpreted in terms of feasibility of these processes.

  1. 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. PMID:25460877

  2. Single-strand DNA translation initiation step analyzed by Isothermal Titration Calorimetry

    SciTech Connect

    Damian, Luminita, E-mail: luminitadamian@microcal.eu.com [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France) [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France); Universite de Toulouse, UPS, IPBS, F-31077 Toulouse (France); IUB, School of Engineering and Science, D-28727 Bremen (Germany); Marty-Detraves, Claire, E-mail: claire.detraves@free.fr [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France) [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France); Universite de Toulouse, UPS, IPBS, F-31077 Toulouse (France); Winterhalter, Mathias [IUB, School of Engineering and Science, D-28727 Bremen (Germany)] [IUB, School of Engineering and Science, D-28727 Bremen (Germany); Fournier, Didier, E-mail: Didier.Fournier@ipbs.fr [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France) [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France); Universite de Toulouse, UPS, IPBS, F-31077 Toulouse (France); Paquereau, Laurent, E-mail: Laurent.Paquereau@ipbs.fr [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France) [CNRS, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 route de Narbonne, F-31077 Toulouse (France); Universite de Toulouse, UPS, IPBS, F-31077 Toulouse (France)

    2009-07-31

    Is single-strand DNA translatable? Since the 60s, the question still remains whether or not DNA could be directly translated into protein. Some discrepancies in the results were reported about functional translation of single-strand DNA but all results converged on a similar behavior of RNA and ssDNA in the initiation step. Isothermal Titration Calorimetry method was used to determine thermodynamic constants of interaction between single-strand DNA and S30 extract of Escherichia coli. Our results showed that the binding was not affected by the nature of the template tested and the dissociation constants were in the same range when ssDNA (K{sub d} = 3.62 {+-} 2.1 x 10{sup -8} M) or the RNA corresponding sequence (K{sub d} = 2.7 {+-} 0.82 x 10{sup -8} M) bearing SD/ATG sequences were used. The binding specificity was confirmed by antibiotic interferences which block the initiation complex formation. These results suggest that the limiting step in translation of ssDNA is the elongation process.

  3. Rapid baculovirus titration assay based on viable cell side scatter (SSC).

    PubMed

    Qi, Jing; Liu, Tao; Pan, Junjie; Miao, Peng; Zhang, Chun

    2015-06-16

    The baculovirus expression system is one of the most powerful tools for the production of recombinant proteins on both laboratory and industrial scales. Multiplicity of infection (MOI) is the crucial parameter for efficient protein expression. To obtain an optimal MOI, it is important to determine titer of virus stock before protein production. Herein, we established a label-free, simple and rapid method for virus titration based on viable cell side scatter (SSC). Generally, the SSC of cells infected with a series of virus dilutions was measured by a flow cytometer at 48h post-infection, and the probability of infected cells at a given dilution was estimated. For each well with the infection probabilities between 0.20 and 0.80, the range of dilutions was chosen, and virus titer was determined with a statistical method. Log-scale comparison of the results between the SSC based method and a standard plaque assay showed a good correlation (R(2)=0.9853), suggesting the fine accuracy of this proposed method. PMID:26002477

  4. Volumetric determination of uranium using titanous sulfate as reductant before oxidimetric titration

    USGS Publications Warehouse

    Wahlberg, James S.; Skinner, Dwight L.; Rader, Lewis F.

    1956-01-01

    A new method for determining uranium in samples containing 0.05 percent or more U3O8, using titanous sulfate as reducing agent, is much shorter, faster, and has fewer interferences than conventional methods using reductor columns. The sample is dissolved with sulfuric, nitric, perchloric, and hydrofluoric acids. Elements that would otherwise form insoluble fluorides are kept in solution by complexing the fluoride ion with boric acid. A precipitation is made with cupferron to remove interfering elements. The solution is filtered to remove the precipitated cupferrates instead of extracting them with chloroform as is usually done. Filtration is preferred to extraction because any niobium that may be in solution forms an insoluble cupferrate that may be removed by filtering but is very difficult to extract with chloroform. Excess cupferron is destroyed by oxidizing with nitric and perchloric acids, and evaporating to dense fumes of sulfuric acid. The uranium is reduced to U(IV) by the addition of titanous sulfate, with cupric sulfate used as an indicator of the completeness of the reduction. Metallic copper is formed when all the uranium is reduced. The reduced copper is then reoxidized by the addition of mercuric perchlorate, an excess of ferric sulfate added, and the solution titrated immediately with standard ceric sulfate with ferroin as an indicator. Precision of the method compared favorable with methods in common use, both for uranium ores and for most types of uranium-rich materials.

  5. A Universal Method for Fishing Target Proteins from Mixtures of Biomolecules using Isothermal Titration Calorimetry

    SciTech Connect

    Zhou, X.; Sun, Q; Kini, R; Sivaraman, J

    2008-01-01

    The most challenging tasks in biology include the identification of (1) the orphan receptor for a ligand, (2) the ligand for an orphan receptor protein, and (3) the target protein(s) for a given drug or a lead compound that are critical for the pharmacological or side effects. At present, several approaches are available, including cell- or animal-based assays, affinity labeling, solid-phase binding assays, surface plasmon resonance, and nuclear magnetic resonance. Most of these techniques are not easy to apply when the target protein is unknown and the compound is not amenable to labeling, chemical modification, or immobilization. Here we demonstrate a new universal method for fishing orphan target proteins from a complex mixture of biomolecules using isothermal titration calorimetry (ITC) as a tracking tool. We took snake venom, a crude mixture of several hundred proteins/peptides, as a model to demonstrate our proposed ITC method in tracking the isolation and purification of two distinct target proteins, a major component and a minor component. Identities of fished out target proteins were confirmed by amino acid sequencing and inhibition assays. This method has the potential to make a significant advancement in the area of identifying orphan target proteins and inhibitor screening in drug discovery and characterization.

  6. Real-Time Monitoring of Membrane-Protein Reconstitution by Isothermal Titration Calorimetry

    PubMed Central

    2013-01-01

    Phase diagrams offer a wealth of thermodynamic information on aqueous mixtures of bilayer-forming lipids and micelle-forming detergents, providing a straightforward means of monitoring and adjusting the supramolecular state of such systems. However, equilibrium phase diagrams are of very limited use for the reconstitution of membrane proteins because of the occurrence of irreversible, unproductive processes such as aggregation and precipitation that compete with productive reconstitution. Here, we exemplify this by dissecting the effects of the K+ channel KcsA on the process of bilayer self-assembly in a mixture of Escherichia coli polar lipid extract and the nonionic detergent octyl-?-d-glucopyranoside. Even at starting concentrations in the low micromolar range, KcsA has a tremendous impact on the supramolecular organization of the system, shifting the critical lipid/detergent ratios at the onset and completion of vesicle formation by more than 2-fold. Thus, equilibrium phase diagrams obtained for protein-free lipid/detergent mixtures would be misleading when used to guide the reconstitution process. To address this issue, we demonstrate that, even under such nonequilibrium conditions, high-sensitivity isothermal titration calorimetry can be exploited to monitor the progress of membrane-protein reconstitution in real time, in a noninvasive manner, and at high resolution to yield functional proteoliposomes with a narrow size distribution for further downstream applications. PMID:24354292

  7. Interaction of oridonin with human serum albumin by isothermal titration calorimetry and spectroscopic techniques.

    PubMed

    Li, Xiangrong; Yang, Zhenhua

    2015-05-01

    Oridonin has been traditionally and widely used for treatment of various human diseases due to its uniquely biological, pharmacological and physiological functions. In this study, the interaction between oridonin and human serum albumin (HSA) was investigated using isothermal titration calorimetry (ITC), in combination with fluorescence spectroscopy and UV-vis absorption spectroscopy. We found that the hydrogen bond and van der Waals force are the major binding forces in the binding of oridonin to HSA. The binding of oridonin to HSA is driven by favorable enthalpy and unfavorable entropy. Oridonin can quench the fluorescence of HSA through a static quenching mechanism. The binding constant between oridonin and HSA is moderate and the equilibrium fraction of unbound oridonin f(u) > 60%. Binding site I is found to be the primary binding site for oridonin. Additionally, oridonin may induce conformational changes of HSA and affect its biological function as the carrier protein. The results of the current study suggest that oridonin can be stored and transported from the circulatory system to reach its target organ to provide its therapeutic effects. But its side-effect in the clinics cannot be overlook. The study provides an accurate and full basic data for clarifying the binding mechanism of oridonin with HSA and is helpful for understanding its effect on protein function during the blood transportation process and its biological activity in vivo. PMID:25816984

  8. Inducible and titratable silencing of Caenorhabditis elegans neurons in vivo with histamine-gated chloride channels

    PubMed Central

    Pokala, Navin; Liu, Qiang; Gordus, Andrew; Bargmann, Cornelia I.

    2014-01-01

    Recent progress in neuroscience has been facilitated by tools for neuronal activation and inactivation that are orthogonal to endogenous signaling systems. We describe here a chemical-genetic approach for inducible silencing of Caenorhabditis elegans neurons in intact animals, using the histamine-gated chloride channel HisCl1 from Drosophila and exogenous histamine. Administering histamine to freely moving C. elegans that express HisCl1 transgenes in neurons leads to rapid and potent inhibition of neural activity within minutes, as assessed by behavior, functional calcium imaging, and electrophysiology of neurons expressing HisCl1. C. elegans does not use histamine as an endogenous neurotransmitter, and exogenous histamine has little apparent effect on wild-type C. elegans behavior. HisCl1-histamine silencing of sensory neurons, interneurons, and motor neurons leads to behavioral effects matching their known functions. In addition, the HisCl1-histamine system can be used to titrate the level of neural activity, revealing quantitative relationships between neural activity and behavioral output. We use these methods to dissect escape circuits, define interneurons that regulate locomotion speed (AVA, AIB) and escape-related omega turns (AIB), and demonstrate graded control of reversal length by AVA interneurons and DA/VA motor neurons. The histamine-HisCl1 system is effective, robust, compatible with standard behavioral assays, and easily combined with optogenetic tools, properties that should make it a useful addition to C. elegans neurotechnology. PMID:24550306

  9. Titration of subcutaneously administered eprinomectin against mature and immature nematodes in cattle.

    PubMed

    Shoop, W; Michael, B; Egerton, J; Mrozik, H; Fisher, M

    2001-12-01

    Eprinomectin has been approved for use as a topically applied endectocide for beef and dairy cattle. To determine if eprinomectin has utility as an injectable anthelmintic, it was titrated at 0.05, 0.1, and 0.2 mg/kg s.c. against adult (Trial 1) and at 0.05, 0.1, 0.14, and 0.2 mg/kg s.c. against immature (Trial 2) stages of lung and gastrointestinal nematodes in cattle. In Trial 1, every dose of subcutaneously delivered eprinomectin showed maximal or near-maximal (> or = 99%) efficacy against Haemonchus placei, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia punctata, Nematodirus helvetianus, Oesophagostomum radiatum, and Dictyocaulus viviparus. Adult C. oncophora was the only exception. However, even against this species, the lowest dose of 0.05 mg/kg showed 93% efficacy, and the efficacious dose necessary to kill 95% (ED95) of adults was 0.056 mg/kg. In Trial 2, every dose of subcutaneously delivered eprinomectin showed maximal or near-maximal (> or = 99%) efficacy against the immature stages of all of the above species of endoparasites. As a result, ED95 values could not be calculated. Consequently, the exquisite potency against endoparasites through parenteral administration suggests that eprinomectin may also have potential utility as an injectable product for cattle. PMID:11780839

  10. A universal method for fishing target proteins from mixtures of biomolecules using isothermal titration calorimetry

    PubMed Central

    Zhou, Xingding; Sun, Qingxiang; Kini, R. Manjunatha; Sivaraman, J.

    2008-01-01

    The most challenging tasks in biology include the identification of (1) the orphan receptor for a ligand, (2) the ligand for an orphan receptor protein, and (3) the target protein(s) for a given drug or a lead compound that are critical for the pharmacological or side effects. At present, several approaches are available, including cell- or animal-based assays, affinity labeling, solid-phase binding assays, surface plasmon resonance, and nuclear magnetic resonance. Most of these techniques are not easy to apply when the target protein is unknown and the compound is not amenable to labeling, chemical modification, or immobilization. Here we demonstrate a new universal method for fishing orphan target proteins from a complex mixture of biomolecules using isothermal titration calorimetry (ITC) as a tracking tool. We took snake venom, a crude mixture of several hundred proteins/peptides, as a model to demonstrate our proposed ITC method in tracking the isolation and purification of two distinct target proteins, a major component and a minor component. Identities of fished out target proteins were confirmed by amino acid sequencing and inhibition assays. This method has the potential to make a significant advancement in the area of identifying orphan target proteins and inhibitor screening in drug discovery and characterization. PMID:18621915

  11. Thermodynamic Profiling of Peptide Membrane Interactions by Isothermal Titration Calorimetry: A Search for Pores and Micelles

    PubMed Central

    Henriksen, J.R.; Andresen, T.L.

    2011-01-01

    Antimicrobial peptides are known to interact strongly with negatively charged lipid membranes, initially by peripheral insertion of the peptide into the bilayer, which for some antimicrobial peptides will be followed by pore formation, and successive solubilization of the membranes resulting in mixed peptide-lipid micelles. We have investigated the mode of action of the antimicrobial peptide mastoparan-X using isothermal titration calorimetry (ITC) and cryo-transmission electron microscopy (cryo-TEM). The results show that mastoparan-X induces a range of structural transitions of POPC/POPG (3:1) lipid membranes at different peptide/lipid ratios. It has been established that ITC can be used as a fast method for localizing membrane transitions and when combined with DLS and cryo-TEM can elucidate structural changes, including the threshold for pore formation and micellation. Cryo-TEM was employed to confirm the structural changes associated with the thermodynamic transitions found by ITC. The pore-formation process has furthermore been investigated in detail and the thermodynamic parameters of pore formation have been characterized using a system-specific temperature where the enthalpy of peptide partitioning becomes zero (Tzero). This allows for an exclusive study of the pore-formation process. The use of ITC to find Tzero allows for characterization of the thermodynamic parameters of secondary processes on lipid membranes. PMID:21723819

  12. MECHANISM OF RETENTION OF METAL CATIONS IN LINERBOARD AND NEVER-

    E-print Network

    Abubakr, Said

    properties (1,2). Changes in virgin fiber quality and the movement to ECF/TCF bleaching along with increased of Agri- culture of any product or service. INTRODUCTION Metal cations are present naturally in wood with cationic movement (2). The loss in swel- ling hinders bonding and leads to a weaker sheet. The cation

  13. Model for Competitive Adsorption of Organic Cations on Clays

    Microsoft Academic Search

    L. Margulies; H. ROZEN; S. NIR

    1988-01-01

    The adsorption on montmorillonite of two monovalent organic cations, methylene blue (MB) and thioflavin T (TFT), was studied in four different situations: (1) separate adsorption of MB or TFT; (2) competitive adsorption of TFT and Cs; (3) competitive adsorption of the two organic cations from their equimolar solutions; and (4) adsorption of TFT on a clay whose cation-exchange capacity (CEC)

  14. Transaction-Based Knowledge Acquisition: Complex Modi cations Made Easier

    E-print Network

    Southern California, University of

    Transaction-Based Knowledge Acquisition: Complex Modi cations Made Easier Yolanda Gil and Marcelo. These changes may require several individual modi cations to various parts of the knowledge base, that need support users in making complex modi cations to a knowledge base. A transaction is a sequence of changes

  15. [PAH Cations as Viable Carriers of DIBs

    NASA Technical Reports Server (NTRS)

    Snow, Ted

    1998-01-01

    This report is intended to fill in the blanks in NASA's file system for our lab astro study of molecular ions of astrophysical interest. In order to give NASA what it needs for its files, I attach below the text of the section from our recent proposal to continue this work, in which we describe progress to date, including a large number of publications. Our initial studies were focused on PAH cations, which appear to be viable candidates as the carriers of the DIBs, an idea that has been supported by laboratory spectroscopy of PAH cations in inert matrices. Beginning with the simplest aromatic (benzene; C6H6) and moving progressively to larger species (naphthalene, C10OH8; pyrene, C16H10; and most recently chrysene, C18H12), we have been able to derive rate coefficients for reactions with neutral spices that are abundant in the diffuse interstellar medium.

  16. Expanding the Palette of Phenanthridinium Cations

    PubMed Central

    Cairns, Andrew G; Senn, Hans Martin; Murphy, Michael P; Hartley, Richard C

    2014-01-01

    5,6-Disubstituted phenanthridinium cations have a range of redox, fluorescence and biological properties. Some properties rely on phenanthridiniums intercalating into DNA, but the use of these cations as exomarkers for the reactive oxygen species (ROS), superoxide, and as inhibitors of acetylcholine esterase (AChE) do not require intercalation. A versatile modular synthesis of 5,6-disubstituted phenanthridiniums that introduces diversity by Suzuki–Miyaura coupling, imine formation and microwave-assisted cyclisation is presented. Computational modelling at the density functional theory (DFT) level reveals that the novel displacement of the aryl halide by an acyclic N-alkylimine proceeds by an SNAr mechanism rather than electrocyclisation. It is found that the displacement of halide is concerted and there is no stable Meisenheimer intermediate, provided the calculations consistently use a polarisable solvent model and a diffuse basis set. PMID:24677631

  17. DNA-assisted photoinduced charge transfer between a cationic poly(phenylene vinylene) and a cationic fullerene.

    PubMed

    Park, Youngil; Liu, Zhongwei; Routh, Prahlad K; Kuo, Cheng-Yu; Park, Young-Shin; Tsai, Hsinhan; Martinez, Jennifer S; Shreve, Andrew P; Cotlet, Mircea; Wang, Hsing-Lin

    2015-06-28

    Water-soluble cationic conjugated poly(phenylene vinylene) (PPV) and cationic fullerene were complexed with negatively charged single stranded DNA and double stranded DNA via electrostatic interactions to achieve photoinduced charge transfer with efficiencies as high as those observed from oppositely charged, cationic PPV and anionic fullerene but with distinctly different quenching mechanisms. PMID:25894733

  18. Sn Cation Valency Dependence in Cation Exchange Reactions Involving Cu2-xSe Nanocrystals

    PubMed Central

    2014-01-01

    We studied cation exchange reactions in colloidal Cu2-xSe nanocrystals (NCs) involving the replacement of Cu+ cations with either Sn2+ or Sn4+ cations. This is a model system in several aspects: first, the +2 and +4 oxidation states for tin are relatively stable; in addition, the phase of the Cu2-xSe NCs remains cubic regardless of the degree of copper deficiency (that is, “x”) in the NC lattice. Also, Sn4+ ions are comparable in size to the Cu+ ions, while Sn2+ ones are much larger. We show here that the valency of the entering Sn ions dictates the structure and composition not only of the final products but also of the intermediate steps of the exchange. When Sn4+ cations are used, alloyed Cu2–4ySnySe NCs (with y ? 0.33) are formed as intermediates, with almost no distortion of the anion framework, apart from a small contraction. In this exchange reaction the final stoichiometry of the NCs cannot go beyond Cu0.66Sn0.33Se (that is Cu2SnSe3), as any further replacement of Cu+ cations with Sn4+ cations would require a drastic reorganization of the anion framework, which is not possible at the reaction conditions of the experiments. When instead Sn2+ cations are employed, SnSe NCs are formed, mostly in the orthorhombic phase, with significant, albeit not drastic, distortion of the anion framework. Intermediate steps in this exchange reaction are represented by Janus-type Cu2-xSe/SnSe heterostructures, with no Cu–Sn–Se alloys. PMID:25340627

  19. Dimer radical cations of indole and indole-3-carbinol: localized and delocalized radical cations of diindolylmethane.

    PubMed

    B?och-Mechkour, Anna; Bally, Thomas; Marcinek, Andrzej

    2011-07-01

    Extending our previous study on the title species (J. Phys. Chem. A2010, 114, 6787), we investigated the dimer cations that are formed on oxidation of the glucobrassin derivatives indole-3-carbinol (I3C) and diindolylmethane (DIM) and of parent indole (I). Radiolysis in ionic liquid and Ar matrices shows that, at sufficiently high concentrations and/or on annealing the solid glasses, intense intermolecular charge-resonance (CR) absorption bands in the NIR herald the formation of sandwich-type dimer cations. The molecular and electronic structure of these species is modeled by calculations with the double-hybrid B2-PLYP-D density functional method which yields predictions in good accord with experiment. The radical cation of DIM also shows a CR band, but unlike in the case of I and I3C, its occurrence is not dependent on the concentration but instead on the solvent: in ionic liquid the CR band is initially absent and arises only on annealing, whereas in Ar matrices it is present from the outset and undergoes blue shifting and sharpening on annealing. These puzzling findings are rationalized on the basis of B2-PLYP-D calculations which predict that neutral DIM exists in the form of two conformers, present in different relative amounts in the two experiments, which on vertical ionization form distinct radical cations, a nonsymmetric one where the odd electron is largely localized on one of the two indole moieties and one with C(2) symmetry where charge and spin are completely delocalized over both halves of the molecule, thus giving rise to an intramolecular CR transition. On annealing, the nonsymmetric cation relaxes to a similarly delocalized structure with C(s) symmetry, thus explaining the observed increase and the shift of the CR band. We believe that DIM(•+) represents the first example of a radical cation which can exist under the same conditions as a localized and a delocalized complex cation. PMID:21648387

  20. Combination of isothermal titration calorimetry and time-resolved luminescence for high affinity antibody-ligand interaction thermodynamics and kinetics

    PubMed Central

    Aweda, Tolulope A.; Meares, Claude F.

    2011-01-01

    For experiments using synthetic ligands as probes for biological experiments, it is useful to determine the specificity and affinity of the ligands for their receptors. As ligands with higher affinities are developed (KA >108 M?1; KD <10?8 M), a new challenge arises: to measure these values accurately. Isothermal titration calorimetry measures heat produced or consumed during ligand binding, and also provides the equilibrium binding constant. However, as normally practiced, its range is limited. Displacement titration, where a competing weaker ligand is used to lower the apparent affinity of the stronger ligand, can be used to determine the binding affinity as well as the complete thermodynamic data for ligand-antibody complexes with very high affinity. These equilibrium data have been combined with kinetic measurements to yield the rate constants as well. We describe this methodology, using as an example antibody 2D12.5, which captures yttrium S-2-(4-aminobenzyl)-1, 4, 7, 10-tetraazacyclododecanetetraacetate. PMID:21964396