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1

Potentiometric titration of calcium in seawater  

Microsoft Academic Search

By using calcium ion selective electrode (Ca ISE) as indicating electrode, saturated calomel electrode (SCE) as reference\\u000a electrode and EGTA as titrant, calcium in seawater was determined by potentiometric titration in borate buffer solution. This\\u000a method can reduce observation errors in the determination of the endpoint, and thus provide better analytical precision (<0.08%)\\u000a than present complexometric titration.

Shi-Nan Xie; Hong Ji; Ai-Qin Wu; Guo-Hua Chen

1997-01-01

2

Potentiometric and coulometric titration of 2-thiobarbituric acid.  

PubMed

A new method for the determination of 2-thiobarbituric acid, using its reaction with iodine in an alkaline medium is presented. In the volumetric titration with potentiometric end-point detection, the determinability range is 10-400 micromol (1.4-58 mg). In coulometric titration using the biamperometric end-point detection, 0.1-20 micromol (1.4 x 10(-2)-2.9 mg) of 2-thiobarbituric acid was successfully determined. PMID:18966286

Ciesielski, W; Kowalska, J; Zakrzewski, R

1995-05-01

3

Potentiometric and Coulometric Titration of 6Propyl2Thiouracil  

Microsoft Academic Search

A method for the determination of 6-propyl-2-thiouracil involving its reaction with iodine in an alkaline medium is presented. In volumetric titration with potentiometric end-point detection, the range of determination is 125-500 mmol (21-85 mg). In coulometric titration using biamperometric end-point detection, 0.5-5.0mmol (0.085-0.85 mg) of 6-propyl-2-thiouracil was successfully determined. The RSD in all applied techniques was < 1%. The methods

Witold Ciesielski; Robert Zakrzewski

1997-01-01

4

Potentiometric and coulometric titration of 2-thiobarbituric acid  

Microsoft Academic Search

A new method for the determination of 2-thiobarbituric acid, using its reaction with iodine in an alkaline medium is presented. In the volumetric titration with potentiometric end-point detection, the determinability range is 10–400 ?mol (1.4–58 mg). In coulometric titration using the biamperometric end-point detection, 0.1–20 ?mol (1.4 × 10?2?2.9 mg) of 2-thiobarbituric acid was successfully determined.

Witold Ciesielski; Joanna Kowalska; Robert Zakrzewski

1995-01-01

5

Potentiometric and coulometric titration of 6-propyl-2-thiouracil.  

PubMed

A method for the determination of 6-propyl-2-thiouracil involving its reaction with iodine in an alkaline medium is presented. In volumetric titration with potentiometric end-point detection, the range of determination is 125-500 mumol (21-85 mg). In coulometric titration using biamperometric end-point detection, 0.5-5.0 mumol (0.085-0.85 mg) of 6-propyl-2-thiouracil was successfully determined. The RSD in all applied techniques was < 1%. The methods developed were applied to the determination of 6-propyl-2-thiouracil in tablets. PMID:9246819

Ciesielski, W; Zakrzewski, R

1997-05-01

6

Potentiometric titration and equivalent weight of humic acid  

USGS Publications Warehouse

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.

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

1960-01-01

7

Potentiometric titration of gold in ores with potassium iodide  

Microsoft Academic Search

A direct potentiometric titration method for the determination of gold in ores and alloys is described. It is based on the reduction of Au(III) with iodide ions yielding accurate and reproducible results. Detection limit and sensitivity were 0.06 and 0.032 mg\\/l Au, respectively. The linear response range was between 0.1 and 120 mg\\/l Au. The method can be used for

L. C. Robles; C. Garcia-Olalla; A. J. Aller

1993-01-01

8

Simultaneous potentiometric determination of cationic and ethoxylated nonionic surfactants in liquid cleaners and disinfectants.  

PubMed

A sensitive potentiometric surfactant sensor based on a highly lipophilic 1,3-didecyl-2-methyl-imidazolium cation and a tetraphenylborate (TPB) antagonist ion was used as the end-point detector in ion-pair potentiometric surfactant titrations using sodium TPB as a titrant. Several analytical and technical grade cationic and ethoxylated nonionic surfactants (EONS) and mixtures of both were potentiometrically titrated. The sensor showed satisfactory analytical performances within a pH range of 3-10 and exhibited satisfactory selectivity for all CS and EONS investigated. Ionic strength did not influence the titration except at 0.1M NaCl, in which a slight distortion of the second inflexion corresponded with the nonionic surfactant. Two-component combinations of four CS and three EONS were potentiometrically titrated using the sensor previously mentioned as the end-point detector. The quantities of the surfactants varied between 2 and 6 ?mol for CS and 2.50 and 7.50 ?mol for EONS. The known addition methodology was used for determination of the surfactant with considerably lower concentration in the mixture. Three commercial products containing cationic surfactants as disinfectants and nonionic surfactants were potentiometrically titrated, and the results for both type of surfactants were compared with those obtained with standard conventional methods. PMID:21147321

Samardži?, Mirela; Sak-Bosnar, Milan; Maduni?-?a?i?, Dubravka

2011-01-15

9

Characterization of Sea Lettuce Surface Functional Groups by Potentiometric Titrations  

NASA Astrophysics Data System (ADS)

In pursuit of our ultimate goal to better understand the prodigious capacity of the marine macroalga Ulva lactuca (sea lettuce) for adsorbing a broad range of dissolved trace metals from seawater, we performed an initial characterization of its surface functional groups. Specifically, the number of distinct functional groups as well as their individual bulk concentrations and acid dissociation constants (pKas) were determined by potentiometric titrations in NaCl solutions of various ionic strengths (I = 0.01-5.0 M), under inert nitrogen atmosphere at 25°C. Depending on the ionic strength, Ulva samples were manually titrated down to pH 2 or 3 with 1 N HCl and then up to pH 10 with 1 N NaOH in steps of 0.1-0.2 units, continuously monitoring pH with a glass combination electrode. Titrations of a dehydrated Ulva standard reference material (BCR-279) were compared with fresh Ulva tissue cultured in our laboratory. A titration in filtered natural seawater was also compared with one in an NaCl solution of equal ionic strength. Equilibrium constants for the ionization of water in NaCl solutions as a function of ionic strength were obtained from the literature. Fits to the titration data ([H]T vs. pH) were performed with the FITEQL4.0 computer code using non-electrostatic 3-, 4-, and 5-site models, either by fixing ionic strength at its experimental value or by allowing it to be extrapolated to zero, while considering all functional group pKas and bulk concentrations as adjustable parameters. Since pKas and bulk concentrations were found to be strongly correlated, the latter were also fixed in some cases to further constrain the pKas. Whereas these calculations are currently ongoing, preliminary results point to three, possibly four, functional groups with pKas of about 4.1, 6.3, and 9.5 at I = 0. Bulk concentrations of the three groups are very similar, about 5-6×10-4 mol/g based on dry weight, which suggests that all are homogeneously distributed over the surface and probably part of a single macromolecular scaffold. Fresh Ulva tissue appears to contain the same three functional groups but at lower concentrations, based on wet weight. The titration in natural seawater was largely dominated by the non-carbonate alkalinity of the solution and could not be robustly modeled. Results of fits with ionic strengths fixed at their experimental values indicate that the pKas of all three groups display prominent Debije-Hückel-type behavior, hence that these acid dissociation reactions involve a different mechanism than metal-proton exchange reactions on mineral surfaces, whose distribution coefficients (i.e., equilibrium constants) generally show a weak ionic strength dependence.

Ebling, A. M.; Schijf, J.

2008-12-01

10

Measurements of total carbon dioxide and alkalinity by potentiometric titration in the GEOSECS program  

Microsoft Academic Search

Approximately 6000 determinations of the alkalinity and total carbon dioxide content of seawater have now been made in the Atlantic, Pacific and Indian Oceans as part of the GEOSECS program by a computer-controlled potentiometric titration technique. The equations used to locate the equivalence points of the carbonic acid system on this titration curve were developed in 1971 but have not

Alvin L. Bradshaw; Peter G. Brewer; Deborah K. Shafer; Robert T. Williams

1981-01-01

11

Rapid, high-precision potentiometric titration of alkalinity in ocean and sediment pore waters  

Microsoft Academic Search

A system for rapid, high precision potentiometric determination of alkalinity in sea water and sediment pore water is presented. Two titration units were used: a 40 ml unit for seawater and a small volume unit for sediment pore water. Titration time was normally less than 10 minutes per sample, including sample exchange. With a 40 ml sample volume, the relative

Conny Haraldsson; Leif G. Anderson; Martin Hassellöv; Stefan Hulth; Kristina Olsson

1997-01-01

12

Estimating the organic acid contribution to coastal seawater alkalinity by potentiometric titrations in a closed cell  

Microsoft Academic Search

This paper examines the performance of a previously reported, closed cell, potentiometric titration technique [J.M. Hernández-Ayón, S.L. Belli, A. Zirino, Anal. Chim. Acta 394 (1999) 101] for the simultaneous determination of pH, total inorganic carbon (TCO2), total alkalinity (TA), and organic alkalinity (OA) in coastal seawater samples. A novel interpretation of the titration data, as recently proposed by Hernández-Ayón et

François L. L. Muller; Bjørn Bleie

2008-01-01

13

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

PubMed

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 KIO(3) in HCl medium, Fe(II) against Ce(IV) and uranium using Davies-Gray method. The precision of titrations using this innovative approach lies between 0.048% and 1.0% relative standard deviation in different redox titrations. With the evolution of this rapid PC based titrator it was possible to develop a simple but high precision potentiometric titration technique for quick determination of hydrazine in nuclear fuel dissolver solution in the context of reprocessing of spent nuclear fuel in fast breeder reactors. PMID:22128994

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

2011-11-01

14

Determination of stability constants of metal-humic acid complexes by potentiometric titration and ion-selective electrodes. [Cu, Pb, Cd  

Microsoft Academic Search

A new technique based on the combined use of potentiometric titration and ion-selective electrodes is proposed for determining apparent stability constants (successive stability constants and overall stability constants) of divalent metal cation (Cu\\/sup 2 +\\/, Pb\\/sup 2 +\\/, and Cd\\/sup 2 +\\/) complexes with humic acids. Fourteen humic acids from diverse sources, including humified rice straw, were examined. The stability

T. Takamatsu; T. Yoshida

1978-01-01

15

Rapid, high-precision potentiometric titration of alkalinity in ocean and sediment pore waters  

NASA Astrophysics Data System (ADS)

A system for rapid, high precision potentiometric determination of alkalinity in sea water and sediment pore water is presented. Two titration units were used: a 40 ml unit for seawater and a small volume unit for sediment pore water. Titration time was normally less than 10 minutes per sample, including sample exchange. With a 40 ml sample volume, the relative standard deviation of the alkalinity obtained in the laboratory was 0.05% and at sea 0.1 %. The small-volume system (0.5-1.5 ml) gave a precision of 0.07%. Five titration points, in two groups after the second equivalence point, were used to evaluate the equivalence volume. Results from equilibrium calculations and computer simulated alkalinity titrations show that it was possible to use a non-modified Gran function [( V 0 +v) ?10 ( E/Z) ] and still achieve good accuracy and precision.

Haraldsson, Conny; Anderson, Leif G.; Hassellöv, Martin; Hulth, Stefan; Olsson, Kristina

1997-12-01

16

Simultaneous titration of ternary alkaline-earth mixtures employing a potentiometric electronic tongue  

Microsoft Academic Search

A fast novel complexometric titration procedure is proposed, in which\\u000a equivalence concentrations were determined using a potentiometric\\u000a electronic tongue. The titration consists in a reduced number of fixed\\u000a additions of titrant and the recording of the potentials of an array of\\u000a ion-selective electrodes with cross-selectivity response. The generated\\u000a data (number of sensors x number of additions) were used as input

Daniel Calvo; Manuel del Valle

2007-01-01

17

Semi-automatic version of the potentiometric titration method for characterization of uranium compounds.  

PubMed

The potentiometric titration method was used for characterization of uranium compounds to be applied in intercomparison programs. The method is applied with traceability assured using a potassium dichromate primary standard. A semi-automatic version was developed to reduce the analysis time and the operator variation. The standard uncertainty in determining the total concentration of uranium was around 0.01%, which is suitable for uranium characterization and compatible with those obtained by manual techniques. PMID:22406220

Cristiano, Bárbara F G; Delgado, José Ubiratan; da Silva, José Wanderley S; de Barros, Pedro D; de Araújo, Radier M S; Dias, Fábio C; Lopes, Ricardo T

2012-09-01

18

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

SciTech Connect

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.

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

1994-07-01

19

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

Microsoft Academic Search

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

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

1970-01-01

20

Indirect potentiometric titration of reducing carbohydrates. I. Using alkaline potassium mercuric bromide solution and sulphide selective electrode.  

PubMed

Indirect potentiometric titration of reducing carbohydrates was developed, where sugar is heated with excess of alkaline Hg(II)-bromide solution. The end point is detected potentiometrically using sulphide selective electrode. The effect of the alkalinity of the reagent, the heating period in a boiling water bath and the presence of the sucrose were studied. The statistical analysis of the results obtained by this method reveals that it can be used with the same accuracy as the Fehling' method. PMID:2596300

Shalaby, A; el-Shehaby, R; Aboul-Kheir, A

1989-09-01

21

A new approach to flow-batch titration. A monosegmented flow titrator with coulometric reagent generation and potentiometric or biamperometric detection.  

PubMed

Monosegmented flow analysis (MSFA) has been used as a flow-batch system to produce a simple, robust, and mechanized titrator that enables true titrations to be performed without the use of standards. This paper also introduces the use of coulometry with monosegmented titration by proposing a versatile flow cell. Coulometric generation of the titrand is attractive for titrations performed in monosegmented systems, because the reagent can be added without increasing the volume of sample injected. Also, biamperomeric and potentiometric detection of titration end-points can increase the versatility of the monosegmented titrator. The cell integrates coulometric generation of the titrand with detection of end-point by potentiometry or biamperometry. The resulting titrator is a flow-batch system in which the liquid monosegment, constrained by the interfaces of the gaseous carrier stream, plays the role of a sample of known volume to be titrated. The system has been used for determination of ascorbic acid, by coulometric generation of I2 with biamperometric detection, and for determination of Fe(II), by coulometric generation of Ce(IV) with potentiometric detection of the end-point, both in feed supplements. PMID:17036213

de Aquino, Emerson Vidal; Rohwedder, Jarbas José Rodrigues; Pasquini, Celio

2006-11-01

22

Effect of excess AgO and EDTA on the redox titration involved in potentiometric determination of plutonium  

Microsoft Academic Search

Attempts to carry out potentiometric determination of plutonium (by AgO-oxidation method) following the determination of thorium (by complexometric EDTA titration) gave positively biased irreproducible values of plutonium. In order to understand the factors leading to the erroneous values of plutonium, the effect of varying amounts of AgO and EDTA on redox [Fe(II)\\/K2Cr2O7] titration in the medium consisting of 1M H2SO4

S. P. Hasilkar; Keshav Chander; S. G. Marathe

1990-01-01

23

Estimating the organic acid contribution to coastal seawater alkalinity by potentiometric titrations in a closed cell.  

PubMed

This paper examines the performance of a previously reported, closed cell, potentiometric titration technique [J.M. Hernández-Ayón, S.L. Belli, A. Zirino, Anal. Chim. Acta 394 (1999) 101] for the simultaneous determination of pH, total inorganic carbon (TCO2), total alkalinity (TA), and organic alkalinity (OA) in coastal seawater samples. A novel interpretation of the titration data, as recently proposed by Hernández-Ayón et al. [J.M. Hernández-Ayón, A. Zirino, A.G. Dickson, T. Camiro-Vagas, E. Valenzuela-Espinoza, Limnol. Oceanogr.: Methods 5 (2007) 225] who applied it to waters of unusually high organic matter content, was applied here to fjord surface waters collected over the duration of a phytoplankton bloom. The parameters pH and TCO2--combined with knowledge of boric, phosphate and silicate species concentrations--allowed calculation of all inorganic species that contributed to TA. This inorganic alkalinity term was then subtracted from TA to produce an estimation of OA. Although the OA values obtained were very small (2-22+/-3 micromol L(-1)), they showed a reproducible trend over time in two simultaneous experiments. The organic acids that may have contributed to OA were characterised in back titrations of acidified and CO2-stripped samples with CO2-free NaOH. Two classes of organic titratable species, with pK(a) values around 4.0+/-0.2 and 9.1+/-0.2 were detected. The first occurred in concentrations that co-varied linearly (r2=0.75) with protein-like fluorescence, indicating a marine biological source, but were only weakly correlated (r2=0.46) to OA. By contrast, Class 2 organic species were not significantly correlated to any fluorescence component of either marine or terrestrial origin but were linearly correlated to OA (r2=0.69). These new results reveal that the method proposed by Hernández-Ayón et al. [J.M. Hernández-Ayón, A. Zirino, A.G. Dickson, T. Camiro-Vagas, E. Valenzuela-Espinoza, Limnol. Oceanogr.: Methods 5 (2007) 225] for estimating OA can provide a powerful and hitherto unused tool for analysing DOM dynamics and sources in most coastal environments, i.e. as a complement to the more widely used optical tools. PMID:18558111

Muller, François L L; Bleie, Bjørn

2008-07-01

24

pH, alkalinity and total CO 2 in coastal seawater by potentiometric titration with a difference derivative readout  

Microsoft Academic Search

A method for measuring three components of the CO2 system, pH, alkalinity (At) and total CO2 (TCO2) in coastal seawater is presented. The measurements are sufficiently precise to register CO2 changes of biological origin in surficial and coastal waters or in culture media. The method is based on a modified potentiometric titration of seawater with acid in a custom-built cell

J. Mart??n Hernández-Ayón; Stuart L. Belli; Alberto Zirino

1999-01-01

25

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

E-print Network

POTENTIOMETRIC CO TITRATIONS OF CARBON MONOX1DE DEHYDROGENASE AND CO-INHIBITION OF THE Nl-REMOVING REACTION WITH 1, 10-PHENANTHROLINE A Thesis by WILLIAM KENT RUSSELL Submitted to the Office of Graduate Studies of Texas ARM University... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1996 Major Subject: Chemistry POTENTIOMETRIC CO TITRATIONS OF CARBON MONOXIDE DEHYDROGENASE AND CO-INHIBITION OF THE NI-REMOVlNG REACTION WITH 1, 10-PHENANTHROLINE...

Russell, William Kent

2012-06-07

26

Determination of ion exchange equilibrium constants of strongly acidic resins with alkaline-earth metals by means of the potentiometric titrations technique  

Microsoft Academic Search

A recently developed methodology for the determination of ion exchange equilibrium constants has been applied to ion exchange systems of 1:2 stoichiometry. Potentiometric titrations with variable ionic strength were carried out. Ionic medium titrations were performed for the estimation of the liquid junction potential. The modified Bromley's methodology and the Wilson model were used for the estimation of the activity

Gregorio Borge; Gorka Arana; Luis A. Fernández; Juan M. Madariaga

1999-01-01

27

Cadmium binding to a histidine-rich glycoprotein from marine mussel blood plasma: potentiometric titration and equilibrium speciation modeling.  

PubMed

Cadmium-binding parameters (conditional stability constants and carrying capacities) of Mytilus edulis blood plasma histidine-rich glycoprotein (HRG) were investigated by potentiometric titrations using a Cd ion-specific electrode. Titration data were applied to a single-component complexation model and expressed as Scatchard plots that were analyzed using the graphical curve peeling method and the algebraic statistical mechanical method. These sets of binding parameters, derived for the purified HRG, were subsequently entered into the geochemical speciation model MINTEQA2 and then used to simulate the experimental titration, thereby determining which set of log K and CL values best represented the titration data. The Cd binding to HRG was best described by a two-class model with log K values of 7.65 +/- 0.10 and 5.41 +/- 0.06 M-1 and carrying capacities of 6.0 +/- 1.2 and 9.5 +/- 0.4 sites/molecule, respectively. At concentration of total Cd measured in the blood plasma of field-collected mussels (< or = 2 x 10(-7) M), plasma Cd speciation would be dominated by the strong affinity sites of HRG (> 93.5% of total Cd binds to HRG), whereas HRG itself would only be 0.05% saturated with Cd, indicating a high-capacity, apparently nonsaturable Cd transport system. PMID:11434304

Nair, P S; Robinson, W E

2001-07-01

28

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

E-print Network

each titration of sulfamic acid or sample, BE SURE TO CALIBRATE THE pH METER WITH THE pH STANDARD PROVIDED. Alternate titrations of sulfamic acid and sample. Standardization of the 0.1 M NaOH Titrant. Weigh to the nearest 0.1 mg about 2.5 g of sulfamic acid and then transfer it to a 100 mL volumetric

McQuade, D. Tyler

29

Phosphorus-doped and undoped glassy carbon indicator electrodes in controlled-current potentiometric titrations of bromide- or chloride-containing active ingredients in some pharmaceutical preparations.  

PubMed

Phosphorus-doped glassy carbon (as a novel material) and glassy carbon (Sigri commercial sample) were applied as potentiometric indicator electrodes in the titrimetric determination of active components with bromide or chloride in their molecules in different pharmaceutical preparations (Buscopan, Prostigmine, Isoptin, Bedoxin, Akineton and Trodon). After the necessary pre-treatment of the electrode surfaces and sample dissolution, the halide was titrated with a standard solution of silver nitrate (indirect determination). Amounts of 10-20 micromol of the investigated active ingredients per titration were determined with a relative standard deviation that, depending on the nature of indicator electrode, determined molecules and filler components, was in the range of 0.3-2.7%. The results obtained were compared with those of the official methods and with those obtained by potentiometric titrations using silver electrode. The titrimetric procedures developed are relatively fast, easy, economical and can be used to analyse of a large number of pharmaceutical products. PMID:15708666

Abramovi?, Biljana F; Guzsvány, Valéria J; Gaál, Ferenc F

2005-02-23

30

Titration  

NSDL National Science Digital Library

Created by Dale Harak, Anita Salem and Paula Shorter for the Connected Curriculum Project, this is a learning modules focusing on the chemical technique of titration. This is used to determine the concentration of a substance in a solution. The purpose of this project is to construct a mathematical model describing the effects of titration, and then to use that model to determine the concentration and the identity of an acid in a solution by fitting the model to real titration data. This is one within a much larger set of learning modules hosted by Duke University.

Harak, Dale; Salem, Anita; Shorter, Paula

2010-05-18

31

Determination of chlorine and dissolved oxygen in waters and of ascorbic acid in pharmaceuticals by iodimetric potentiometric titration using a plasticized poly(vinyl chloride) membrane electrode  

Microsoft Academic Search

The response to triiodide of an electrode based on a membrane containing poly(vinyl chloride) and 2-nitrophenyl octyl ether as plasticizer in a 1:2 (ww) ratio is studied. The electrode is suitable for the automatic potentiometric titration of triiodide in the concentration range 10?5–10?3 mol l?1 with thiosulphate. The electrode has been satisfactorily applied to the determination of chlorine and dissolved

Concepción Sánchez-Pedreño; Joaquín A. Ortuño; J. Hernández

1996-01-01

32

Determination of uranium in uranium metal, uranium oxides, and uranyl nitrate solutions by potentiometric titration  

SciTech Connect

A simple, fast method for the determination of uranium in uranium metal, uranium oxides, and uranyl nitrate solutions has been adapted from the Davies-Gray volumetric method to meet the needs of Y-12. One-gram duplicate aliquots of uranium metal or uranium oxide are dissolved in 1:1 HNO/sub 3/ and concentrated H/sub 2/SO/sub 4/ to sulfur trioxide fumes, and then diluted to 100-mL volume. Duplicate aliquots are then weighed for analysis. For uranyl nitrate samples, duplicate aliquots containing between 50 and 150 mg of U are weighed and analyzed directly. The weighed aliquot is transferred to a Berzelius beaker; 1.5 M sulfamic acid is added, followed in order by concentrated phosphoric acid, 1 M ferrous sulfate, and (after a 30-second interval) the oxidizing reagent. After a timed 3-minute waiting period, 100 mL of the 0.1% vanadyl sulfate-sulfuric acid mixture is added. The sample is then titrated past its endpoint with standard potassium dichromate, and the endpoint is determined by second derivative techniques on a mV/weight basis.

Tucker, H.L.; McElhaney, R.J.

1983-01-01

33

Predicting proton titration in cationic micelle and bilayer environments  

NASA Astrophysics Data System (ADS)

Knowledge of the protonation behavior of pH-sensitive molecules in micelles and bilayers has significant implications in consumer product development and biomedical applications. However, the calculation of pKa's in such environments proves challenging using traditional structure-based calculations. Here we apply all-atom constant pH molecular dynamics with explicit ions and titratable water to calculate the pKa of a fatty acid molecule in a micelle of dodecyl trimethylammonium chloride and liquid as well as gel-phase bilayers of diethyl ester dimethylammonium chloride. Interestingly, the pKa of the fatty acid in the gel bilayer is 5.4, 0.4 units lower than that in the analogous liquid bilayer or micelle, despite the fact that the protonated carboxylic group is significantly more desolvated in the gel bilayer. This work illustrates the capability of all-atom constant pH molecular dynamics in capturing the delicate balance in the free energies of desolvation and Coulombic interactions. It also shows the importance of the explicit treatment of ions in sampling the protonation states. The ability to model dynamics of pH-responsive substrates in a bilayer environment is useful for improving fabric care products as well as our understanding of the side effects of anti-inflammatory drugs.

Morrow, Brian H.; Eike, David M.; Murch, Bruce P.; Koenig, Peter H.; Shen, Jana K.

2014-08-01

34

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

PubMed

Natural monocrystalline pyrite as a new indicator electrode for the potentiometric titration of weak acids in acetonitrile, propionitrile and benzonitrile was studied. The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range from 0.1 to 0.001 M, with a Nernstian slope of 74 mV per decade. Sodium methylate, potassium hydroxide and tetrabutylammonium hydroxide (TBAH) proved to be very suitable titrating agent for this titration. The response time was less than (11 s) and the lifetime of the electrode is long. The advantages of the electrode are log-term stability, fast response, and reproducibility, while the sensor is easy to prepare and of low cost. PMID:19276604

Mihajlovi?, Ljiljana; Nikoli?-Mandi?, Snezana; Vukanovi?, Branislav; Mihajlovi?, Randel

2009-03-01

35

A new approach to flow-batch titration. A monosegmented flow titrator with coulometric reagent generation and potentiometric or biamperometric detection  

Microsoft Academic Search

Monosegmented flow analysis (MSFA) has been used as a flow-batch system to produce a simple, robust, and mechanized titrator\\u000a that enables true titrations to be performed without the use of standards. This paper also introduces the use of coulometry\\u000a with monosegmented titration by proposing a versatile flow cell. Coulometric generation of the titrand is attractive for titrations\\u000a performed in monosegmented

Emerson Vidal de Aquino; Jarbas José Rodrigues Rohwedder; Celio Pasquini

2006-01-01

36

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

PubMed Central

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

Pozharski, Edwin; MacDonald, Robert C

2002-01-01

37

Back titration with mercuric nitrate in alkaline medium  

Microsoft Academic Search

Small amounts of bismuth in the order of 100 µg up to ~ 25 mg were potentiometrically determined by back titration with mercuric nitrate in alkaline media. The method gives highly accurate results and is further successfully applied for analysis of pairs of bismuth together with one of the cations of calcium, copper, cadmium, zinc, manganese, nickel, lead, aluminium and

H. Khalifa; A. Soliman

1959-01-01

38

Study of the compositional heterogeneity in poly( N-isopropylacrylamide–acrylic acid) microgels by potentiometric titration experiments  

Microsoft Academic Search

The compositional distribution of acrylic acid (AA) residues in poly(N-isopropylacrylamide–acrylic acid) [poly(NIPAM–AA)] microgels has been investigated using alkaline titration experiments. It is found that the apparent acid dissociation constant (pKaapp) of the AA residues increases with the degree of dissociation. This is due to the electrostatic effect that arises as AA residues dissociate, and the pKaapp change depends on the

Morten Lykkegaard Christensen; Kristian Keiding

2005-01-01

39

Improved methylene blue two-phase titration method for determining cationic surfactant concentration in high-salinity brine.  

PubMed

The methylene blue (MB) two-phase titration method is a rapid and efficient method for determining the concentrations of anionic surfactants. The point at which the aqueous and chloroform phases appear equally blue is called Epton's end point. However, many inorganic anions, e.g., Cl(-), NO3(-), Br(-), and I(-), can form ion pairs with MB(+) and interfere with Epton's end point, resulting in the failure of the MB two-phase titration in high-salinity brine. Here we present a method to extend the MB two-phase titration method for determining the concentration of various cationic surfactants in both deionized water and high-salinity brine (22% total dissolved solid). A colorless end point, at which the blue color is completely transferred from the aqueous phase to the chloroform phase, is proposed as titration end point. Light absorbance at the characteristic wavelength of MB is measured using a spectrophotometer. When the absorbance falls below a threshold value of 0.04, the aqueous phase is considered colorless, indicating that the end point has been reached. By using this improved method, the overall error for the titration of a permanent cationic surfactant, e.g., dodecyltrimethylammonium bromide, in deionized (DI) water and high-salinity brine is 1.274% and 1.322% with limits of detection (LOD) of 0.149 and 0.215 mM, respectively. Compared to the traditional acid-base titration method, the error of this improved method for a switchable cationic surfactant, e.g., tertiary amine surfactant (Ethomeen C12), is 2.22% in DI water and 0.106% with LOD of 0.369 and 0.439 mM, respectively. PMID:25365626

Cui, Leyu; Puerto, Maura; López-Salinas, José L; Biswal, Sibani L; Hirasaki, George J

2014-11-18

40

Digital image-based titrations  

Microsoft Academic Search

The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical

Edvaldo da Nobrega Gaiao; Valdomiro Lacerda Martins; Wellington da Silva Lyra; Luciano Farias de Almeida; Edvan Cirino da Silva; Mário César Ugulino Araújo

2006-01-01

41

Coupled chemical processes at clay\\/electrolyte interface: A batch titration study of Na-montmorillonites  

Microsoft Academic Search

The present work addresses the protolytic charge of montmorillonite, which occurs on the broken-bond sites at the particle edges. The purpose is to overcome the general difficulty arising in potentiometric titration due to coupled side reactions, which severely impede the titrant budget (partial dissolution of the clay and of secondary phases, hydrolysis and readsorption of dissolved species, cation exchange). Batch

Myriam Duc; Fabien Thomas; Fabien Gaboriaud

2006-01-01

42

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

PubMed

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

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

2014-07-01

43

The effects of O-substituents of hexahomotrioxacalix[3]arene on potentiometric discrimination between dopamine and biological organic/inorganic cations.  

PubMed

As an interesting type of molecular recognition at a membrane surface, the tri-O-acetic acid ester (host 2) of hexahomotrioxacalix[3]arene, when incorporated into poly(vinyl chloride) (PVC) liquid membranes, displays a high potentiometric selectivity for dopamine over, not only other catecholamines (noradrenaline, adrenaline), but also quaternary ammonium guests (tetramethylammonium, choline, and acetylcholine) and inorganic cations (Na+, K+, NH4+). Interestingly, changes in membrane potential based on the host-guest complexation of host 2 that were observed dopamine/inorganic cation selectivity were not displayed by the related hosts 3 and 4, which contain amide substituents. This paper describes our efforts to separately estimate the two factors contributing to the dopamine selectivities, i.e., the guest lipophilicity factor and the host-guest complexation factor, in an attempt to understand the effects of the O-substituents of these hosts. The potentiometric experiments showed that, although the guests had roughly equal lipophilicity, the electromotive force (EMF) response for dopamine by host 2 was excellent. Furthermore, host 2 displayed ca. a 20-fold stronger complexation for dopamine, compared to noradrenaline, adrenaline, K+, and NH4+ cations. These results indicate that the high potentiometric selectivity of the ion-selective electrode for dopamine mainly reflect, not the guest lipophilicity factor but the host-guest complexation factor. On the other hand, host 3 displayed ca. a 3000-fold stronger binding to Na+ than dopamine, thus explaining the reasons for the lower dopamine-selectivities of host 3 compared to host 2. It is interesting to note that the high potentiometric selectivities for dopamine were displayed by not only host 2 but also host 5, regardless of the simple structure of the O-substituents. PMID:17329883

Saijo, Ryosuke; Murakami, Hiroyuki; Tsunekawa, Saori; Imanishi, Souhei; Shirai, Naohiro; Ikeda, Shin-Ichi; Odashima, Kazunori

2007-03-01

44

Potentiometric investigations of (acid + base) equilibria in ( n-butylamine + acetic acid) systems in binary (acetone + cyclohexane) solvent mixtures  

Microsoft Academic Search

By using the potentiometric titration method, standard equilibrium constants have been determined of acid dissociation of molecular acid, Ka(HA), cationic acid, Ka(BH+), of anionic and cationic homoconjugation, KAHA-andKBHB+, respectively, and of molecular heteroconjugation, KAHB (KBHA), in (acid+base) systems without proton transfer consisting of n-butylamine and acetic acid in binary (acetone+cyclohexane) solvent mixtures. The results have shown that both the pKa(HA)

Ma?gorzata Czaja; Anna Kozak; Mariusz Makowski; Lech Chmurzy?ski

2005-01-01

45

On the binding of calcium by micelles composed of carboxy-modified pluronics measured by means of differential potentiometric titration and modeled with a self-consistent-field theory.  

PubMed

We perform differential potentiometric titration measurements for the binding of Ca2+ ions to micelles composed of the carboxylic acid end-standing Pluronic P85 block copolymer (i.e., CAE-85 (COOH-(EO)26-(PO)39-(EO)26-COOH)). Two different ion-selective electrodes (ISEs) are used to detect the free calcium concentration; the first ISE is an indicator electrode, and the second is a reference electrode. The titration is done by adding the block copolymers to a known solution of Ca2+ at neutral pH and high enough temperature (above the critical micellization temperature CMT) and various amount of added monovalent salt. By measuring the difference in the electromotive force between the two ISEs, the amount of Ca2+ that is bound by the micelles is calculated. This is then used to determine the binding constant of Ca2+ with the micelles, which is a missing parameter needed to perform molecular realistic self-consistent-field (SCF) calculations. It turns out that the micelles from block copolymer CAE-85 bind Ca2+ ions both electrostatically and specifically. The specific binding between Ca2+ and carboxylic groups in the corona of the micelles is modeled through the reaction equilibrium -COOCa+ <==> -COO- + Ca2+ with pKCa = 1.7 +/- 0.06. PMID:17154568

Lauw, Y; Leermakers, F A M; Cohen Stuart, M A; Pinheiro, J P; Custers, J P A; van den Broeke, L J P; Keurentjes, J T F

2006-12-19

46

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

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

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

1994-01-01

47

Potentiometric and Coulometric Determination of Carbimazole  

Microsoft Academic Search

A method for the determination of carbimazole involving its reaction with iodine in an alkaline medium is presented. In volumetric titration with potentiometric end-point detection the range of determination is 30–500 ?mol (5.6–93 mg). In coulometric titration using biamperometric end-point detection, 0.5–20 ?mol (0.09–3.7 mg) of carbimazole was successfully determined. The coulometric titration was applied to the determination of carbimazole

Witold Ciesielski; Anna Krenc

2000-01-01

48

Digital image-based titrations.  

PubMed

The exploitation of digital images obtained from a CCD camera (WebCam) as a novel instrumental detection technique for titration is proposed for the first time. Named of digital image-based (DIB) titration, it also requires, as a traditional titration (for example, spectrophotometric, potentiometric, conductimetric), a discontinuity in titration curves where there is an end point, which is associated to the chemical equivalence condition. The monitored signal in the DIB titration is a RGB-based value that is calculated, for each digital image, by using a proposed procedure based on the red, green, and blue colour system. The DIB titration was applied to determine HCl and H3PO4 in aqueous solutions and total alkalinity in mineral and tap waters. Its results were compared to the spectrophotometric (SPEC) titration and, by applying the paired t-test, no statistic difference between the results of both methods was verified at the 95% confidence level. Identical standard deviations were obtained by both titrations in the determinations of HCl and H3PO4, with a slightly better precision for DIB titration in the determinations of total alkalinity. The DIB titration shows to be an efficient and promising tool for quantitative chemical analysis and, as it employs an inexpensive device (WebCam) as analytical detector, it offers an economically viable alternative to titrations that need instrumental detection. PMID:17723410

Gaiao, Edvaldo da Nobrega; Martins, Valdomiro Lacerda; Lyra, Wellington da Silva; de Almeida, Luciano Farias; da Silva, Edvan Cirino; Araújo, Mário César Ugulino

2006-06-16

49

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

ERIC Educational Resources Information Center

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)

Selig, Walter S.

1985-01-01

50

Surface Titrations of Perlite Suspensions  

Microsoft Academic Search

The surface charge behaviour of unexpanded and expanded perlite samples in KNO3and NaCl solutions were investigated as a function of pH and ionic strength. The solutions of KNO3and NaCl ranging from 10?3to 1.0Mwere used. The potentiometric titration method was used to determine the surface charge of perlite samples. It was confirmed that the perlite samples had no the point of

Mahir Alkan; Mehmet Do ?

1998-01-01

51

Potentiometric batch and flow injection analysis of betaine hydrochloride.  

PubMed

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

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

2007-01-01

52

Interactions of phenol with cationic micelles of hexadecyltrimethylammonium bromide studied by titration calorimetry, conductimetry, and 1H NMR in the range of low additive and surfactant concentrations  

Microsoft Academic Search

Interactions of phenol (PhOH) with micellar aggregates of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions at surfactant concentrations close to the CMC and phenol contents of 1, 5, or 10 mmol?kg?1 have been investigated at 303 K by means of titration calorimetry, solution conductimetry, and 1H NMR spectroscopy. Estimates of the main thermodynamic parameters related to HTAB micellization were made for

Radhouane Chaghi; Louis-Charles de Ménorval; Clarence Charnay; Gaëlle Derrien; Jerzy Zajac

2008-01-01

53

LABORATORY EXPERIMENT 4 Alkalimetric Titration of an Acid Mixture  

E-print Network

LABORATORY EXPERIMENT 4 Alkalimetric Titration of an Acid Mixture In this experiment the quantitative composition of a solution, which is a mixture of a monoprotic strong acid (HCl) and a weaker triprotic acid (H3PO4) will be determined by pH- potentiometric methods. This experiment will introduce you

Nazarenko, Alexander

54

Simultaneous determination of mixtures of metal ions by complexometric titration and multivariate calibration  

Microsoft Academic Search

A new complexometric titration method for the determination of mixtures of metal ions with multivariate calibration was developed. The principle of this method is described and a linear complexometric titration equation is derived. In this work, a mercury film electrode (MFE) was used as indicator electrode for potentiometric measurements, and a double junction Ag\\/AgCl electrode as reference electrode. The mixtures

Yongnian Ni; Yingliang Wu

1997-01-01

55

Titration vs. Tradition  

Microsoft Academic Search

The way titration curves are traditionally taught in the undergraduate curriculum is reviewed, and a more rational approach is advocated. A spreadsheet is then used to illustrate the various properties of titration curves and to fit titration data.

Robert de Levie

1996-01-01

56

Bioanalysis with Potentiometric Membrane Electrodes.  

ERIC Educational Resources Information Center

Discusses major themes and interrelationships common to bioselective potentiometric membrane electrodes including the nature of bioselective electrodes, applications, and future prospects. Includes tables on traditional ion-selective membrane electrodes, nontraditional electrodes, and typical biocatalytic potentiometric electrodes. (Author/JN)

Rechnitz, G. A.

1982-01-01

57

Potentiometric analysis of ionic surfactants by a new type of ion-selective electrode  

Microsoft Academic Search

A new type of ion-selective electrode for the determination of ionic surfactants is presented. It can be exploited as end-point indicator with a high sensitivity in potentiometric titration of surfactants and for direct potentiometric measurements in an online flow system. The electrode consisted of an ion pair between sodium laurylsulphate and 1,3-didecyl-2-methyl-imidazolium chloride, immobilized in a plasticized PVC membrane. This

M. Gerlache; Z. Sentürk; J. C. Viré; J. M. Kauffmann

1997-01-01

58

Thermodynamic analysis of Bacillus subtilis endospore protonation using isothermal titration calorimetry  

NASA Astrophysics Data System (ADS)

Bacterial proton and metal adsorption reactions have the capacity to affect metal speciation and transport in aqueous environments. We coupled potentiometric titration and isothermal titration calorimetry (ITC) analyses to study Bacillus subtilis spore-proton adsorption. We modeled the potentiometric data using a four and five-site non-electrostatic surface complexation model (NE-SCM). Heats of spore surface protonation from coupled ITC analyses were used to determine site specific enthalpies of protonation based on NE-SCMs. The five-site model resulted in a substantially better model fit for the heats of protonation but did not significantly improve the potentiometric titration model fit. The improvement observed in the five-site protonation heat model suggests the presence of a highly exothermic protonation reaction circa pH 7 that cannot be resolved in the less sensitive potentiometric data. From the log Ks and enthalpies we calculated corresponding site specific entropies. Log Ks and site concentrations describing spore surface protonation are statistically equivalent to B. subtilis cell surface protonation constants. Spore surface protonation enthalpies, however, are more exothermic relative to cell based adsorption suggesting a different bonding environment. The thermodynamic parameters defined in this study provide insight on molecular scale spore-surface protonation reactions. Coupled ITC and potentiometric titrations can reveal highly exothermic, and possibly endothermic, adsorption reactions that are overshadowed in potentiometric models alone. Spore-proton adsorption NE-SCMs derived in this study provide a framework for future metal adsorption studies.

Harrold, Zoë R.; Gorman-Lewis, Drew

2013-05-01

59

Modern Directions for Potentiometric Sensors.  

PubMed

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

Bakker, Eric; Chumbimuni-Torres, Karin

2008-01-01

60

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

PubMed

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

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

2014-01-01

61

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

NASA Technical Reports Server (NTRS)

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.

Meites, L.

1978-01-01

62

Potentiometric and Coulometric Determination of 5Phenyl1,3,4-Oxadiazole-2Thiol  

Microsoft Academic Search

A method for the determination of 5-phenyl-1,3,4-oxadiazole-2-thiol involving its reaction with iodine in an alkaline medium has been presented. In volumetric titration with potentiometric endpoint detection, the determination range is 25–500 µmol. In coulometric titration using biamperometric endpoint detection, 0.5–5 µmol of 5-phenyl-1,3,4-oxadiazole-2-thiol were successfully determined. The errors and the relative standard deviations were below 1%. The shapes of the

W. Ciesielski; A. Krenc

2005-01-01

63

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

Microsoft Academic Search

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

Zhimin Qiang; Craig Adams

2004-01-01

64

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

E-print Network

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

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

65

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

PubMed Central

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

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

2011-01-01

66

Potentiometric Dipyridamole Sensors Based on Lipophilic Ion Pair Complexes and Native Ionic Polymer Membranes  

Microsoft Academic Search

The construction and general performance characteristics of three novel potentiometric PVC membrane sensors responsive to the dipyridamole cation are described. These sensors are based on the use of the ion -association complexes of dipyridamole cation with tetraphenylborate and Reineckate counter anions as ion exchange sites in a plasticized PVC matrix.A plasticized native polymer (e.g., carboxylated polyvinyl chloride) is also used.

Saad S. M. Hassan; Nashwa M. H. Rizk

2000-01-01

67

Accurate Potentiometric Determination of Lipid Membrane–Water Partition Coefficients and Apparent Dissociation Constants of Ionizable Drugs: Electrostatic Corrections  

Microsoft Academic Search

Purpose  Potentiometric lipid membrane–water partition coefficient studies neglect electrostatic interactions to date; this leads to\\u000a incorrect results. We herein show how to account properly for such interactions in potentiometric data analysis.\\u000a \\u000a \\u000a \\u000a Materials and Methods  We conducted potentiometric titration experiments to determine lipid membrane–water partition coefficients of four illustrative\\u000a drugs, bupivacaine, diclofenac, ketoprofen and terbinafine. We then analyzed the results conventionally and with

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

2009-01-01

68

Automatic flow titrator based on a multicommutated unsegmented flow system for alkalinity monitoring in wastewaters  

Microsoft Academic Search

A full automatic flow system based on potentiometric titration for alkalinity monitoring in wastewater treating plants is presented. Titration to an end-point of pH 5.75 partial alkalinity (PA) and then to pH 4.3 intermediate alkalinity (IA) allows to distinguish the relative buffering contributions of both bicarbonate and volatile acids in anaerobic digesters and, thus, the attainment of a IA:PA ratio

Cristina M. N. V Almeida; Rui A. S Lapa; José L. F. C Lima

2001-01-01

69

Acidbase equilibrium of ?-adrenoceptor blocking agents in acetic acid medium and methods for their titration  

Microsoft Academic Search

The overall dissociation constants and the formation constants of the perchlorate salts, in anhydrous acetic acid, of a series of ß-adrenoceptor blocking agents have been determined. On the basis of these values simple potentiometric and visual titration methods for the assay of ß-adrenoceptor blocking drugs in acetic acid are described.

José Barbosa; Maria Eleno Torrero

1991-01-01

70

Surfactant/detergent titration analysis method and apparatus for machine working fluids, surfactant-containing wastewater and the like  

DOEpatents

The present invention is an improved method and related apparatus for quantitatively analyzing machine working fluids and other aqueous compositions such as wastewater which contain various mixtures of cationic, neutral, and/or anionic surfactants, soluble soaps, and the like. The method utilizes a single-phase, non-aqueous, reactive titration composition containing water insoluble bismuth nitrate dissolved in glycerol for the titration reactant. The chemical reaction of the bismuth ion and glycerol with the surfactant in the test solutions results in formation of micelles, changes in micelle size, and the formation of insoluble bismuth soaps. These soaps are quantified by physical and chemical changes in the aqueous test solution. Both classical potentiometric analysis and turbidity measurements have been used as sensing techniques to determine the quantity of surfactant present in test solutions. This method is amenable to the analysis of various types of new, in-use, dirty or decomposed surfactants and detergents. It is a quick and efficient method utilizing a single-phase reaction without needing a separate extraction from the aqueous solution. It is adaptable to automated control with simple and reliable sensing methods. The method is applicable to a variety of compositions with concentrations from about 1% to about 10% weight. It is also applicable to the analysis of waste water containing surfactants with appropriate pre-treatments for concentration.

Smith, Douglas D. (Knoxville, TN); Hiller, John M. (Oak Ridge, TN)

1998-01-01

71

Surfactant/detergent titration analysis method and apparatus for machine working fluids, surfactant-containing wastewater and the like  

DOEpatents

The present invention is an improved method and related apparatus for quantitatively analyzing machine working fluids and other aqueous compositions such as wastewater which contain various mixtures of cationic, neutral, and/or anionic surfactants, soluble soaps, and the like. The method utilizes a single-phase, non-aqueous, reactive titration composition containing water insoluble bismuth nitrate dissolved in glycerol for the titration reactant. The chemical reaction of the bismuth ion and glycerol with the surfactant in the test solutions results in formation of micelles, changes in micelle size, and the formation of insoluble bismuth soaps. These soaps are quantified by physical and chemical changes in the aqueous test solution. Both classical potentiometric analysis and turbidity measurements have been used as sensing techniques to determine the quantity of surfactant present in test solutions. This method is amenable to the analysis of various types of new, in-use, dirty or decomposed surfactants and detergents. It is a quick and efficient method utilizing a single-phase reaction without needing a separate extraction from the aqueous solution. It is adaptable to automated control with simple and reliable sensing methods. The method is applicable to a variety of compositions with concentrations from about 1% to about 10% weight. It is also applicable to the analysis of waste water containing surfactants with appropriate pre-treatments for concentration. 1 fig.

Smith, D.D.; Hiller, J.M.

1998-02-24

72

Studies of cellulose surfaces by titration and ESCA  

NASA Astrophysics Data System (ADS)

The surface properties of unbleached kraft pulp fibers of varying lignin content prepared by digestion with different amounts of excess alkali have been investigated using polyelectrolyte titration, potentiometric titration and ESCA. The surfaces contain two different acidic groups that dissociate completely above pH 7.5, one with pK ? 3.6 and one with pK ? 5.7. The amount of the latter group correlates directly with the amount of lignin in the pulp. The ESCA analysis indicates that the relative amount of carboxylic groups and alkyl carbon in the surface decreases as the lignin content decreases and also that material with high alkyl carbon content is enriched in the outermost surface of the cellulose. Thus, a combination of ESCA analysis and high-precision titrations is able to yield a very detailed picture of the effect of digestion conditions on surface properties of cellulose fibers of direct relevance to paper properties.

Stenius, Per; Laine, Janne

1994-01-01

73

Sorption modelling on illite Part I: Titration measurements and the sorption of Ni, Co, Eu and Sn  

NASA Astrophysics Data System (ADS)

In this study the physico-chemical, titration and sorption characteristics of Na-illite du Puy (Na-illite) have been measured and modelled. Samples of illite, collected in the region of le Puy-en-Velay, France, were purified and conditioned to the Na-form and physico-chemically characterised. Potentiometric titrations on suspensions of the Na-illite were carried out using a batch backtitration technique in 0.01, 0.1 and 0.5 M NaClO 4 background electrolytes from pH˜3 to ˜11.5 in an inert atmosphere glove box. The supernatant solutions from each titration experiment in each series were analysed for K, Mg, Ca, Sr, Si, Al, Fe and Mn. The titration data were modelled in terms of the protolysis of two amphoteric edge sites ( tbnd S W1OH and tbnd S W2OH) without an electrostatic term. Sorption edges (solid/liquid distribution ratios versus pH at trace sorbate concentrations and constant ionic strength) were determined for the transitions metals Ni(II) and Co(II), the lanthanide Eu(III), and the heavy metal Sn(IV) on Na-illite with NaClO 4 as the background electrolyte under anoxic conditions (CO 2 ? 2 ppm, O 2 ? 2 ppm). The study thus encompasses a broad range of metals with different thermodynamic characteristics and with valence states ranging from II to IV. The results from the modelling of the titration data, in combination with a non electrostatic surface complexation and cation exchange sorption model were applied to quantitatively describe the uptake characteristics of the metals listed above on Na-illite. Since sorption edges were measured at trace concentrations, metal uptake was modelled as occurring on strong type sites ( tbnd S SOH) only. This sorption model, the two site protolysis non electrostatic surface complexation and cation exchange model (2SPNE SC/CE model) had been previously developed and used to describe metal uptake on montmorillonite.

Bradbury, M. H.; Baeyens, B.

2009-02-01

74

Luminescence titrations of polyelectrolytes  

E-print Network

LUMINESCENCE TITRATIONS OF POLYELECTROLYTES A Thesis by EDWIN RENE ALVAREZ Submitted to the Graduate college of Texas ARM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1986 Major subject...: Chemistry LUMINESCENCE TITRATIONS OF POLYELECTROLYTES A Thesis by EDWIN RENE ALVAREZ Approved as to style and content by: harles R. Martin (Chair of Committee) Marvin W. Rowe (Member) , 3 James F. Haw (Member) Donald W. Pettig ew (Member...

Alvarez, Edwin Rene

2012-06-07

75

Determination of dissociation constants of weak acids by deconvolution of proton binding isotherms derived from potentiometric data  

Microsoft Academic Search

Potentiometric titration of six carboxylic acid analytes were measured in aqueous and semiaqueous solvents to determine the effect of the solvent composition on the dissociation constants of the acids. The analytes studied were monoprotic (formic acid, acetic acid), diprotic (maleic and succinic acid) and triprotic (1, 2, ranging in composition from 0 to 80% by volume dioxane. The methodology used

J. A. Schwarz; Cr. Contescu; V. T. Popa; A. Contescu; Y. Lin

1996-01-01

76

Tripodal Receptors for Cation and Anion Sensors  

PubMed Central

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

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

2006-01-01

77

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

USGS Publications Warehouse

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.

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

2004-01-01

78

Potentiometric determination of the ‘formal’ hydrolysis ratio of aluminium species in aqueous solutions  

Microsoft Academic Search

The ‘formal’ hydrolysis ratio (h=C(OH?)added\\/C(Al)total) of hydrolysed aluminium-ions is an important parameter required for the exhaustive and quantitative speciation–fractionation of aluminium in aqueous solutions. This paper describes a potentiometric method for determination of the formal hydrolysis ratio based on an automated alkaline titration procedure. The method uses the point of precipitation of aluminium hydroxide as a reference (h=3.0) in order

Agathe C. Fournier; Kirill L. Shafran; Carole C. Perry

2008-01-01

79

Protonation of carboxyl latex particles in the presence of a strong cationic polyelectrolyte  

Microsoft Academic Search

The charging behavior of carboxyl latex surface in the presence of poly(diallyl dimethyl ammonium chloride) (DADMAC) was investigated by means of potentiometric titrations and electrophoretic mobility. The titration curves at different ionic strengths show a common crossing point, which coincides with the point of zero mobility, and can be identified with the point of zero charge (PZC). This characteristic behavior

Dusko Cakara; Claire Chassagne; C ´ ecile Gehin-Delval; Michal Borkovec

2007-01-01

80

Back titration with mercuric nitrate in alkaline medium analysis of tertiary mixtures of mercury(II) with some other metals  

Microsoft Academic Search

Tertiary mixtures each containing mercury(II) were analysed by simple procedures involving combination between the recent method of back titration with mercuric nitrate in alkaline medium, and the volumetric methods which make use of masking agents as cyanide. The content of mercury(II) in most mixtures is determined potentiometrically with potassium iodide using the silver amalgam as indicator electrode. End points are

H. Khalifa; Farouk A. Osman

1960-01-01

81

Potentiometric membrane sensors for the selective determination of cinnarizine in pharmaceutical preparations  

Microsoft Academic Search

The construction and general performance characteristics of four novel potentiometric PVC membrane sensors responsive to the cinnarizinium cation are described. These sensors are based on the use of the ion-association complexes of the cinnarizinium cation with tetraphenylborate, flavianate, reineckate and 12-molybdatophosphate counter anions as ion exchange sites in a plasticized PVC matrix. These sensors exhibit fast, stable and near-Nernstian response

Saad S. M. Hassan; Ragab M. Abdel-Aziz; Alaa B. Abbas

1996-01-01

82

[Alkalimetric titrations of salts of organic bases in the Pharmacopoeia].  

PubMed

Modified methods - alkalimetry in ethanol 70% with a defined small volume of hydrochloric acid 0.01 mol/l added to the solution of the sample before the titration and alkalimetry in ethanol 70% or ethanol 96% alone with potentiometric end-point detection for the assay of halide salts of 11 organic N-bases has been investigated. The results were compared to those obtained by the method of the European Pharmacopoeia 7th Ed. (Ph. Eur. 7th Ed.). The Ph. Eur. 7th Ed. use for 8 investigated substances alkalimetry in alcohol 96 % with a defined small volume of hydrochloric acid 0.01 mol/l (5 ml) with potentiometric end-point detection: Cinchocaine hydrochloride, Codeine hydrochloride dihydrate, Ethylmorphine hydrochloride, Lidocaine hydrochloride, Papaverine hydrochloride, Pilocarpine hydrochloride, Quinine hydrochloride, Tetracaine hydrochloride. Our results revealed that the Ph. Eur. 7th Ed. method did not work for 5 drugs from this group: Cinchocaine hydrochloride, Ethylmorphine hydrochloride, Papaverine hydrochloride, Pilocarpine hydrochloride and Tetracaine hydrochloride. In the group of investigated substances we included also drugs with the character of weak organic bases for which Ph. Eur. 7th Ed. prescribed different methods for their assay: Thiamine hydrochloride and Pyridoxine hydrochloride - acidimetric titration in non-aqueous solvents with perchloric acid and Procaine hydrochloride - determination of primary aromatic amino-nitrogen (Ph. Eur. 7th Ed., chapter 2.5.8). PMID:24393115

Bezáková, Zelmíra; Stankovi?ová, Mária

2013-12-01

83

Potentiometric determination of silver(I), palladium(II) and gold(III) in mixtures by use of an iodide-selective electrode  

Microsoft Academic Search

Two procedures are proposed for the potentiometric determination of Ag(I), Pd(II) and Au(III) in binary mixtures, by titration with potassium iodide solution, and use of a commercial iodide electrode as sensor. In the first procedure, two aliquots of the mixture are titrated, at pH 2.0 ± 0.2 and 9.0 ± 0.2, adjusted with dilute sulphuric acid and ammonia solution. At

Mohamed Tarek Mohamed Zaki; Adel El-Sayed Mohamed

1991-01-01

84

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

NASA Astrophysics Data System (ADS)

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.

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

85

Potentiometric studies at ORNL with hydrogen electrode concentration cells  

SciTech Connect

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

Mesmer, R.E.; Palmer, D.A.; Wesolowski, D.J. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.

1994-12-31

86

New Insights into Chitosan-DNA Interactions Using Isothermal Titration Microcalorimetry  

E-print Network

New Insights into Chitosan-DNA Interactions Using Isothermal Titration Microcalorimetry Pei Lian Ma of deacetylation (DDA), and molecular weight (Mn) of chitosan, using isothermal titration microcalorimetry (ITC prepared by alkaline deacetylation of chitin found in the shells of crustaceans. It is a linear cationic

Buschmann, Michael

87

Acid-Base Titration Applet  

NSDL National Science Digital Library

Acid-Base titration applet that plots pH changes as student adds acid or base. Gives choice of indicators (only two right now). Compares plots for titration of traditional solution and a buffered solution (several choices for comparison). Can alter starting concentrations.

Usc

88

Potentiometric sensors with ion-exchange Donnan exclusion membranes.  

PubMed

Potentiometric sensors that exhibit a non-Hofmeister selectivity sequence are normally designed by selective chemical recognition elements in the membrane. In other situations, when used as detectors in separation science, for example, membranes that respond equally to most ions are preferred. With so-called liquid membranes, a low selectivity is difficult to accomplish since these membranes are intrinsically responsive to lipophilic species. Instead, the high solubility of sample lipids in an ionophore-free sensing matrix results in a deterioration of the response. We explore here potentiometric sensors on the basis of ion-exchange membranes commonly used in fuel cell applications and electrodialysis, which have so far not found their way into the field of ion-selective electrodes. These membranes act as Donnan exclusion membranes as the ions are not stripped of their hydration shell as they interact with the membrane. Because of this, lipophilic ions are no longer preferred over hydrophilic ones, making them promising candidates for the detection of abundant ions in the presence of lipophilic ones or as detectors in separation science. Two types of cation-exchanger membranes and one anion-exchange membrane were characterized, and potentiometric measuring ranges were found to be Nernstian over a wide range down to about 10 ?M concentrations. Depending on the specific membrane, lipophilic ions gave equal response to hydrophilic ones or were even somewhat discriminated. The medium and long-term stability and reproducibility of the electrode signals were found to be promising when evaluated in synthetic and whole blood samples. PMID:23731350

Grygolowicz-Pawlak, Ewa; Crespo, Gastón A; Ghahraman Afshar, Majid; Mistlberger, Günter; Bakker, Eric

2013-07-01

89

Solid state potentiometric oxygen gas sensors  

Microsoft Academic Search

Oxygen gas sensors, operating in the potentiometric (zero current) mode, based upon oxygen ion conducting solid electrolytes are reviewed. Detailed consideration is given to practical aspects of their composition, construction and operation.

W. C. Maskell; B. C. H. Steele

1986-01-01

90

Potentiometric studies of complex formation between methylmercury(II) and EDTA.  

PubMed

The protonation of EDTA (ethylenediaminetetra-acetic acid) and its complex formation with methylmercury(II) ions was studied by a potentiometric method at 25 degrees in 1.0M NaNO(3). The protonation constants of EDTA and the equilibrium constants for the complexation reactions between methylmercuric ions and EDTA were evaluated by analysing the experimental data with the ETITR version of the general error-minimizing program LETAGROP. The results were used to develop an analytical method, based on complexometric titration and ion-exchange separation, for the determination of inorganic and organic mercury in the presence of one another. PMID:18962242

Jawaid, M

1978-04-01

91

Coacervation of cationic gemini surfactant with N-benzoylglutamic acid in aqueous solution.  

PubMed

Coacervation of cationic gemini surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) with pH-sensitive N-benzoylglutamic acid (H2Bzglu) has been investigated by potentiometric pH-titration, turbidity titration, dynamic light scattering (DLS), isothermal titration calorimetry (ITC), TEM, (1)H NMR, and light microscopy. Phase boundaries of the 12-6-12/H2Bzglu mixture were obtained over the pH range from 2 to 9 and in the H2Bzglu concentration range from 30.0 to 50.0 mM at pH 4.5. When the H2Bzglu concentration is beyond 30.0 mM, the 12-6-12/H2Bzglu mixed solution undergoes the phase transitions from soluble aggregate, to precipitate, coacervate, and soluble aggregate again as pH increases. The results indicate that coacervation occurs at extremely low 12-6-12 concentration and lasts over a wide surfactant range, and can be enhanced or suppressed by changing pH, 12-6-12/H2Bzglu molar ratio and H2Bzglu concentration. The coacervates present a disorderly connected lay structure. Coacervation only takes place at pH 4-5, where the aggregates are nearly charge neutralized, and a minimum H2Bzglu concentration of 30.0 mM is required for coacervation. In this pH range, H2Bzglu mainly exist as HBzglu(-). The investigations on intermolecular interactions indicate that the aggregation of 12-6-12 is greatly promoted by the strong electrostatic and hydrophobic interactions with the HBzglu(-) molecules, and the interaction also promotes the formation of dimers, trimers, and tetramers of HBzglu(-) through hydrogen bonds. The double chains of 12-6-12 and the HBzglu(-) oligomers can play the bridging roles connecting aggregates. These factors endow the mixed system with a very high efficiency in generating coacervation. PMID:24205784

Wang, Meina; Fan, Yaxun; Han, Yuchun; Nie, Zongxiu; Wang, Yilin

2013-12-01

92

Potentiometric differential titration of ?-phenyl-?-aminobutyric acid hydrochloride and intermediate products of its synthesis  

Microsoft Academic Search

Preparations of fl-phenyl -?-aminobutyric acid hydrochloride (phenylbut, I) belong to the class of neotropic drugs, and due to their pronounced tranquilizing activity, find a multifaceted application in medicine [4, 7]. The increase in demand for medicinal preparations has resulted in a need of improvement in the technology of the synthesis and growth in the industrial production of I. For this

A. Ya. Veveris; I. A. Luse

1990-01-01

93

Quantitative analysis of dimethyl titanocene by iodometric titration, gas chromatography and NMR.  

PubMed

In this study we report the use of an automated iodometric titration method and a novel gas chromatography (GC) method for the quantitative analysis of dimethyl titanocene (DMT), a key raw material in drug synthesis. Both approaches are based on the reaction of DMT in toluene or tetrahydrofuran solutions with iodine. In the case of iodometric titration, excess iodine is titrated with a standardized aqueous sodium thiosulfate solution to a potentiometric end-point for the determination of DMT concentration. Alternatively, GC is employed to measure the concentration of iodomethane, a product of the reaction between DMT and iodine, in order to determine the concentration of DMT in the solution. Excellent agreement between iodometric titration, GC and NMR results using several DMT samples confirms the accuracy of the two methods and strongly supports the use of either method as a replacement to the expensive NMR for quantitative DMT analysis. The relatively few sources of error associated with the two methods, their ubiquitous nature and ease of application in routine analysis make them the analytical methods of choice, among all. Both methods have been validated according to ICH requirements. The use of iodometric titration method for DMT analysis is demonstrated with a couple of applications. PMID:11377038

Vailaya, A; Wang, T; Chen, Y; Huffman, M

2001-06-01

94

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

PubMed Central

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

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

2008-01-01

95

Amperometric, Bipotentiometric, and Coulometric Titration.  

ERIC Educational Resources Information Center

Reviews literature on amperometric, bipotentiometric, and coulometric titration methods examining: apparatus and methodology; acid-base reactions; precipitation and complexing reactions (considering methods involving silver, mercury, EDTA or analogous reagents, and other organic compounds); and oxidation-reduction reactions (considering methods…

Stock, John T.

1984-01-01

96

[Measure of alkalinity in an alcohol/water mixture by potentiometric end-point detection. Critical remarks on a new method in the European pharmacopoeia].  

PubMed

The European Pharmacopoeia introduced a new alkalimetric method for assay of alkaloid (and other N-base) salts. The principle of method is: after preliminary addition of small amount of hydrochloric acid, titration is carried out with 0.1 N NaOH in alcohol/water mixture with potentiometric end-point detection. The applicability and reproducibility of this method have been examined at 11 substances. The results of alkalimetric method were compared to those obtained by nonaqueous titration (Ph. Hg. VII.). The method of Ph. Eur. is well reproducible (SD < +/- 0.50), however it could not be applied in case of some compounds (4 cases out of 11). Authors revealed that for the titration carried out according to the present prescription of Ph. Eur. 4., minimum pKa 7 should be the basicity of the alkaloids. They suggest to perform the titration in 70% alcohol and without preliminary addition of HCl for weaker bases. PMID:15112441

Völgyi, Gergely; Takácsné, Novák Krisztina

2003-01-01

97

A Potentiometric Sensing System for Aluminium  

Microsoft Academic Search

A potentiometric flow system based on a sparingly soluble mixture of aluminum laurate and lauric acid as the responsive element and a glass electrode as the primary sensor is reported. Effects of pH adjustment, responses to possible interferent species and the response of the analogous barium sensor to aluminium are also presented.

P. E. Body; P. Stimburys; D. E. Mulcahy

1985-01-01

98

Simple Potentiometric Determination of Reducing Sugars  

ERIC Educational Resources Information Center

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…

Moresco, Henry; Sanson, Pedro; Seoane, Gustavo

2008-01-01

99

In situ dissolution testing using potentiometric sensors.  

PubMed

Potentiometric sensors can be used to determine the amount of API dissolved in the dissolution medium in function of time by measuring directly in the dissolution vessel of a Paddle (USP type 2) and Basket (USP type 1) apparatus. The prototype potentiometric sensor instrumentation showed very promising results for a selection of APIs with different physico-chemical properties. The applicability, benefits and limitations of the prototype were explored. The applicability of the measurement technique strongly depends on the log(P) of the API. Here, it is shown that measurements can easily be performed for APIs with a log(P)>4. Electrode performance however decreases with decreasing logP of the APIs due to decreased drug selectivity in comparison to the excipients and ionic strength of the applied dissolution medium. The potentiometric sensors are shown to be insensitive towards undissolved particles and air bubbles as opposed to UV spectrometric measurement where these can lead to severe light scattering. For the tested APIs, the obtained dissolution profiles are very reproducible and show a low variation compared to the measurements using manual sampling and UV or HPLC analysis. The measurements demonstrate that potentiometric sensors are a very promising technology that can become a standard for in situ dissolution measurements. PMID:18539443

Peeters, Karl; De Maesschalck, Roy; Bohets, Hugo; Vanhoutte, Koen; Nagels, Luc

2008-08-01

100

Endosomal escape and siRNA delivery with cationic shell crosslinked knedel-like nanoparticles with tunable buffering capacities  

PubMed Central

Cationic shell crosslinked knedel-like nanoparticles (cSCKs) have emerged as a highly efficient transfection agent for nucleic acids delivery. In this study, a new class of cSCKs with tunable buffering capacities has been developed by altering the amounts of histamines and primary amines incorporated into their crosslinked shell regions. The effect of histamine content of these nanoparticles with a hydrodynamic diameter of ca. 20 nm, on the siRNA-binding affinity, cytotoxicity, immunogenicity, and transfection efficiency was investigated. The modification of cSCKs with histamine was found to reduce the siRNA-binding affinity and cellular binding. On the other hand, it significantly reduced the toxicity and immunogenicity of the nanoparticles with subsequent increase in the transfection efficiency. In addition, escape from endosomes was facilitated by having two species of low and high pKas (i.e. histamine and primary amine groups, respectively), as demonstrated by the potentiometric titration experiments and the effect of bafilomycin A1, an inhibitor of the endosomal acidification, on the transfection efficiency of cSCKs. Histamine modification of 15 mol% was a threshold, above which cSCKs with higher histamine content completely lost the ability to bind siRNA and to transfect cells. This study highlights the potential of histamine incorporation to augment the gene silencing activity of cationic nanoparticles, reduce their toxicity, and increase their biocompatibility, which is of particular importance in the design of nucleic acids delivery vectors. PMID:22901966

Shrestha, Ritu; Elsabahy, Mahmoud; Florez-Malaver, Stephanie; Samarajeewa, Sandani; Wooley, Karen L.

2012-01-01

101

Potentiometric determination of free acidity in presence of hydrolysable ions and a sequential determination of hydrazine.  

PubMed

A simple potentiometric method for the determination of free acidity in presence of hydrolysable ions and sequential determination of hydrazine is developed and described. Both free acid and hydrazine are estimated from the same aliquot. In this method, free acid is titrated with standard sodium carbonate solution after the metal ions in solutions are masked with EDTA. Once the end point for the free acid is determined at pH 3.0, an aliquot of formaldehyde is added to liberate the acid equivalent to hydrazine which is then titrated with the same standard sodium carbonate solution using an automatic titration system. The described method is simple, accurate and reproducible. This method is especially applicable to all ranges of nitric acid and heavy metal ion concentration relevant to Purex process used for nuclear fuel reprocessing. The overall recovery of nitric acid is 98.9% with 1.2% relative standard deviation. Hydrazine content has also been determined in the same aliquot with a recovery of nitric acid is 99% with 2% relative standard deviation. The major advantage of the method is that generation of corrosive analytical wastes containing oxalate or sulphate is avoided. Valuable metals like uranium and plutonium can easily be recovered from analytical waste before final disposal. PMID:21726724

Ganesh, S; Khan, Fahmida; Ahmed, M K; Pandey, S K

2011-08-15

102

Flow Injection Potentiometric Assay of Hexoprenaline in Its Pure State, Pharmaceutical Preparations, and Biological Samples  

PubMed Central

Different hexoprenaline (Hx2SO4) conventional and coated wire electrodes were constructed and evaluated. Membranes were based on hexoprenalinium phosphotungstate (Hx-PTA) and hexporenalinium phosphomolybdate (Hx-PMA). The electrodes were fully characterized in terms of their composition, response time, life span, pH, and temperature and then were applied to the potentiometric determination of the hexoprenalinium ion in its pure state, pharmaceutical preparations, and biological samples, urine and plasma, under batch and flow injection conditions. The selectivity of the electrodes towards many inorganic cations, sugars, amino acids, and some other brochodilatures of close chemical composition was also tested. PMID:18483573

El-Nashar, Rasha M.

2008-01-01

103

Surface Complexation of Neodymium at the Rutile-Water Interface: A Potentiometric and Modeling Study in NaCl Media to 250°C  

SciTech Connect

The adsorption of Nd{sup 3+} onto rutile surfaces was examined by potentiometric titration from 25 to 250 C, in 0.03 and 0.30m NaCl background electrolyte. Experimental results show that Nd{sup 3+} sorbs strongly, even at low temperature, with adsorption commencing below the pHznpc of rutile. In addition, there is a systematic increase in Nd{sup 3+} adsorption with increasing temperature. The experimental results were rationalized and described using surface oxygen proton affinities computed from the MUlti SIte Complexation or MUSIC model, coupled with a Stern-based three-layer description of the oxide/water interface. Moreover, molecular-scale information was incorporated successfully into the surface complexation model, providing a unique geometry for the adsorption of Nd{sup 3+} on rutile. The primary mode of Nd{sup 3+} adsorption was assumed to be the tetradentate configuration found for Y{sup 3+} adsorption on the rutile (110) surface from previously described in situ X-ray standing wave experiments, wherein the sorbing cations bond directly with two adjacent ''terminal'' and two adjacent ''bridging'' surface oxygen atoms. Similarly, the adsorption of Na{sup +} counterions was also assumed to be tetradentate, as supported by MD simulations of Na{sup +} interactions with the rutile (110) surface, and by analogous X-ray standing wave results for Rb{sup +} adsorption on rutile. Fitting parameters for Nd{sup 3+} adsorption included binding constants for the tetradentate adsorption complex and capacitance values for the inner-sphere binding plane. In addition, hydrolysis of the tetradentate adsorption complex was permitted and resulted in significantly improved model fits at higher temperature and pH values. The modeling results indicate that the Stern-based MUSIC surface-complexation model adequately accommodates molecular-scale information to uniquely rationalize and describe multivalent ion adsorption systematically into the hydrothermal regime.

Ridley, Mora K. [Texas Tech University, Lubbock; Machesky, Michael L. [Illinois State Water Survey, Champaign, IL; Wesolowski, David J [ORNL; Palmer, Donald [ORNL

2005-01-01

104

Hydration and Lyotropic Melting of Amphiphilic Molecules: A Thermodynamic Study Using Humidity Titration Calorimetry  

Microsoft Academic Search

The hydration of the lipid 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and of the cationic detergent dodecyltrimethylammonium bromide (DTAB) has been studied by means of isothermal titration calorimetry (ITC), gravimetry, and infrared (IR) spectroscopy. During the experiments films of the amphiphiles are perfused by an inert gas of variable relative humidity. The measurement of adsorption heats using ITC represents a new adaptation of adsorption

H. Binder; B. Kohlstrunk; H. H. Heerklotz

1999-01-01

105

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

PubMed

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

Rao, B V; Gopinath, R

1989-08-01

106

Lead-selective membrane potentiometric sensor based on a recently synthesized bis(anthraquinone) sulfide derivative  

SciTech Connect

The need for monitoring of toxic heavy metal ions in environmental samples has prompted the development of ion-selective electrodes for these ions. A new PVC membrane electrode for lead ions, based on bis[(1-hydroxy-9,10-anthraquinone)-2-methyl]sulfide as membrane carrier, was prepared. The sensor exhibits a Nernstian response for Pb{sup 2+} over a wide concentration range (5.6 {times} 10{sup {minus}3}--4.0 {times} 10{sup {minus}6} M). It has a response time of about 30 s and can be used for at least 3 months without any divergence in potentials. The proposed membrane sensor revealed good selectivities for Pb{sup 2+} over a wide variety of other metal ions. It was used as an indicator electrode in potentiometric titration of lead ion.

Pouretedal, H.R.; Forghaniha, A.; Sharghi, H. [Shiraz Univ. (Iran, Islamic Republic of). Dept. of Chemistry; Shamsipur, M. [Razi Univ., Kermanshah (Iran, Islamic Republic of). Dept. of Chemistry

1998-12-01

107

Potentiometric determination of saccharin in dietary products using mercurous nitrate as titrant.  

PubMed

A rapid, precise and low cost method for saccharin determination in dietary products is proposed. Saccharin in several samples is potentiometrically titrated with mercurous nitrate solution using a silver wire coated with a metallic mercury film as the working electrode, and the end point was found using a Gran's plot. The detection limit of sodium saccharin was 0.5 mg/ml and the best pH range was from 2.0 to 3.5. Sucrose, glucose, aspartame, sodium cyclamate, sorbitol, fructose, benzoic acid, salicylic acid and lactose do not interfere even in significant amounts. The interference due to the presence of chloride and/or phosphate ions can be eliminated by previous solvent extraction of this sweetener. Recovery of saccharin from various dietary products gave from 95.2 to 103.2% of the label claim. PMID:18965696

Fo, O F; Moraes, A J; Dos Santos, G

1993-05-01

108

Determination of Solanesol by Coulometric Titration  

Microsoft Academic Search

A method for determination of solanesol by coulometric titration was developed. The titration was carried out in a mixture of 2M KBr-glacial acetic acid (22:78 v\\/v), and bromine was generated at the anode. Solanesol reacted with bromine with a value of n = 18. The end point of the titration was detected with two-electrode amperometry. The method is rapid, accurate

Kuai Zhi Liu; Meng Liu; Deliang Li

1998-01-01

109

Direct complexometric titration of calcium phosphates.  

PubMed

Calcium was determined in calcium phosphate samples by dissolving the sample in hydrochloric acid, adding hydroxynaphthol blue indicator and triethanolamine, adjusting the pH to 12.3--12.5 with potassium hydroxide solution, and titrating with standard disodium ethylenediaminetetraacetate solution. Time can be saved and the formation of a precipitate (which dissolves readily during the titration) can be avoided by adding at least 85% of the amount of complexing agent required for titration before adjusting the pH. PMID:903881

Tuckerman, M M; Sanchez de Ramos, M E

1977-09-01

110

Potentiometric Zinc Ion Sensor Based on Honeycomb-Like NiO Nanostructures  

PubMed Central

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

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

2012-01-01

111

Application of personal microcomputers in the analytical laboratory--I: Potentiometric analysis.  

PubMed

A novel general-purpose interface-controller unit has been designed and applied in potentiometric analysis. The unit is operated by a personal microcomputer programmed in BASIC. The interface-controller permits direct reading of specific ion-electrodes and can activate, under program control, laboratory instruments such as motor-driven burettes. The interface-controller is expendable to 16 analogue input channels, 16 binary (logic) input lines and 16 control relays but requires only one microcomputer I/O port (a total of 9 I/O lines) to handle all operations. Analogue to digital conversion is realized by counting, with the microcomputer, the output frequency of an analogue-to-frequency converter. This inexpensive method is effective in rejecting interfering signals such as power-line interference. The system has been applied in potentiometric titration analysis for determining the apparent dissociation constants of carbonic acid in sea-water and Dead Sea brines, and for ammonia determination with a gas-sensing electrode. PMID:18963126

Ben-Yaakov, S; Raviv, R; Guterman, H; Dayan, A; Lazar, B

1982-04-01

112

Microanalytical Determination of Formaldehyde by Direct Titration with Hydroxylamine Using Interdigitated Microelectrode Array Biamperometric End-Point Indicator  

Microsoft Academic Search

.  ?An interdigitated microelectrode array (IDA) biamperometric titration is presented for the microdetermination of formaldehyde.\\u000a It is based on a direct titration of formaldehyde with hydroxylamine under the formation of formaldoxime. The released hydrogen\\u000a cations react with hydroxyl anions in 0.1?M NaOH. The interdigitated pair of two individually polarizable microelectrodes\\u000a serves as a biamperometric end-point indicator. Hydroxylamine together with dissolved free

Peter Tom?ík; Lea Mrafkova ´; Dušan Bustin

2003-01-01

113

A disposable voltammetric cell for determining the titratable acidity in vinegar.  

PubMed

A disposable voltammetric cell using three pencil leads as working, reference, and counter electrodes was developed for determining the titratable acidity, i.e. the acid content in vinegar. The materials of the pencil leads were graphite-reinforcement carbons (GRCs). A voltammetric determination of acid was made by measuring the reduction prepeak current of 3,5-di-t-butyl-1,2-benzoquinone (DBBQ) due to the presence of acids in unbuffered solution. The potential stability of the pseudo-reference electrode of GRC was examined. The prepeak current was found to be proportional to the acetic acid concentration from 0.05 to 2.7 mM with a correlation coefficient of 0.999. The cell-to-cell reproducibility for 1 mM acetic acid was evaluated with ten individual disposable cells. The RSD of the prepeak current and the SD of the prepeak potential were 2.56% and 0.008, respectively. The titratable acidity in five vinegar samples was determined by voltammetry using disposable cells and compared with that of the titratable acidity determined by the conventional potentiometric titration method. We then observed the results by both methods, and found a correlation coefficient of 0.972. As such, the voltammetry using disposable-cell required only one thousandth the volume of a vinegar sample for the titration method. The disposable cell was superior to the conventional electrochemical cell, in terms of facility, environment-friendly, and economy, and thus a sensor using the present cell would be useful for routine work in the quality control of vinegar. PMID:14640441

Kotani, Akira; Miyaguchi, Yuji; Harada, Dai; Kusu, Fumiyo

2003-11-01

114

A new potentiometric sensor for the determination of ?-amylase activity  

Microsoft Academic Search

A platinum redox sensor for the direct potentiometric determination of ?-amylase concentration has been described. The sensor measured the amount of triiodide released from a starch–triiodide complex, which was correlated with the ?-amylase activity after biocatalytic starch degradation. The composition and stability of the potassium triiodide solution was optimized. The starch–triiodide complex was characterized potentiometrically at variable starch and triiodide

Nikola Saka?; Milan Sak-Bosnar; Marija Horvat; Dubravka Maduni?-?a?i?; Aleksandar Szechenyi; Barna Kovacs

2011-01-01

115

Determination of sulphuric acid in process effluent streams using sequential injection titration.  

PubMed

Sulphuric acid in process effluent streams from an electrorefining copper plant was analysed with a sequential injection (SI) titration system using sodium hydroxide as titrant. In the proposed SI titration system a base titrant, acid analyte and base titrant zone were injected sequentially into a distilled water carrier stream in a holding coil and swept by flow reversal through a reaction coil to the detector. The base zones contained bromothymol blue as indicator and the endpoint was monitored spectrophotometrically at 620 nm. The influence of carrier stream flow rate, acid and base zone volumes and titrant concentration on the linear range of the method was studied to obtain an optimum. A linear relationship between peak width and logarithm of the acid concentration was obtained in the range 0.006-0.178 mol l(-1) of H(2)SO(4) for a NaOH concentration of 0.002 mol l(-1). The results obtained for the SI titration of process samples were in good agreement with a standard potentiometric method with an RSD<0.75% and a sample frequency of 23 samples h(-1). PMID:18967965

du Plessis, H; van Staden, J F

2000-05-31

116

Kinetics, thermodynamics and surface heterogeneity assessment of uranium(VI) adsorption onto cation exchange resin derived from a lignocellulosic residue  

NASA Astrophysics Data System (ADS)

A new cation exchange resin (PGTFS-COOH) having a carboxylate functional group at the chain end was prepared by grafting poly(hydroxyethylmethacrylate) onto tamarind fruit shell, TFS (a lignocellulosic residue) using potassium peroxydisulphate-sodium thiosulphate redox initiator, and in the presence of N,N'-methylenebisacrylamide (MBA) as a crosslinking agent, followed by functionalisation. The adsorbent was characterized with the help of FTIR, XRD, scanning electron micrographs (SEM), and potentiometric titrations. The kinetic and isotherm data, obtained at optimum pH value 6.0 at different temperatures could be fitted with pseudo-second-order equation and Sips isotherm model, respectively. An increase in temperature induces positive effect on the adsorption process. The calculated activation energy of adsorption ( Ea, 18.67 kJ/mol) indicates that U(VI) adsorption was largely due to diffusion-controlled process. The values of adsorption enthalpy, Gibbs free energy, and entropy were calculated using thermodynamic function relationships. The decrease in adsorption enthalpy with increasing U(VI) uploading on the adsorbent, reflects the surface energetic heterogeneity of the adsorbent. The isosteric heat of adsorption was quantitatively correlated with the fractional loading for the U(VI) ions adsorption onto PGTFS-COOH. The results showed that the PGTFS-COOH possessed heterogeneous surface with sorption sites having different activities.

Anirudhan, T. S.; Radhakrishnan, P. G.

2009-02-01

117

Modeling metal binding by dissolved humic substance: a revisit to the fluorometric titration approach.  

PubMed

It is desirable to directly investigate metal cation binding by dissolved humic substance (HS) in environmental samples without isolation and purification of the HS. This is commonly achieved by the fluorometric titration approach, in which the variations of the HS components' fluorescence when titrated with metal cations, such as cupric ions (Cu(2+)), were commonly resolved by a well-established chemometric tool called parallel factor analysis and fit to a classical nonlin ear equation to obtain cation binding parameters. The nonlinear expression was derived based on the two assumptions that a given HS component (e.g., L) binds Cu(2+) with a 1:1 stoichiometry, forming only the complex LCu, and that other ligands competing with L for Cu(2+) are not explicitly considered. Given the deviations (e.g., the presence of multiple HS components competing for Cu(2+) and a likely 2:1 binding stoichiometry in addition to the 1:1 binding) from the assumptions, the fitting-derived binding parameters reported in past studies are questionable; those studies commonly reported high goodness-of-fit (R(2)) as a support of the validity of the assumptions. This study deconstructed the current equation and examined it with two organic ligand components in a simulated study to see what conditions could also yield a good fit. It turned out that high a R(2) value ranging between 0.9971 and 1.0 was observed despite the deviations from the above-mentioned assumptions. In addition, this study re-evaluated some published experimental data from these past studies and found that the fitting-derived parameters could not be accounted for based on the above-mentioned assumptions. The findings in this study therefore indicate that the current fluorometric titration approach is problematic when investigating HS component interactions with metal ions in situ. The combination of ion-selective electrode and fluorometric titration may be an alternative to the current fluorometric titration approach alone. PMID:24694698

Chen, Hao; Meng, Wei; Lei, Kun

2014-04-01

118

Flow injection potentiometric determination of saccharin in dietary products with relocation of filtration unit.  

PubMed

A flow injection potentiometric procedure for saccharin determination in dietary products is proposed. Saccharin is precipitated as mercurous saccharinate and the excess of the mercurous cation is potentiometrically measured using a silver wire coated with a mercury film as the working electrode. A filter unit is used to avoid contact between the precipitate and the electrode surface. With relocation in the flow manifold, the accumulated precipitate is removed on-line. Sucrose, glucose, aspartame, sodium cyclamate and sodium benzoate do not interfere when present in amounts similar to those observed in commercial products. Results are comparable with those obtained by UV-spectrophotometry and the correlation coefficient between methods is equal to 0.9930. A linear relationship between DeltaE (mV) and the logarithm of saccharin concentration was obtained in the saccharin concentration range 2 x 10(-3) - 1 x 10(-2)M. The sampling frequency is 60/hour and only 0.76 mg of Hg(2+)(2) is consumed in each determination. PMID:18965991

Fatibello-Filho, O; Nóbrega, J A; Moraes Guaritá-Santos, A J

1994-05-01

119

[Determination of the sulfate ion content in antibiotic sulfate salts by a complexometric titration method].  

PubMed

A possibility of assaying antibiotic sulfates, such as gentamicin, kanamycin, monomycin, neomycin, ristomycin, streptomycin, florimycin and polymyxin M sulfates for sulfate ions by titration with barium chloride in the presence of chlorphosphonaso-III, a metal indicator immediately in the salt solutions or after elimination of the cation by means of ion exchange (sulfocation exchange resins in H+-form) was tested. The procedure was shown to be adequate to the classical weight method. PMID:7469396

Kartseva, V D; Lokshin, G B; Libinson, G S; Kruzhkova, N G

1980-12-01

120

Isothermal titration calorimetric studies of the pH induced conformational changes of bovine serum albumin  

Microsoft Academic Search

Bovine serum albumin (BSA) is a soft globular protein that undergoes conformational changes through several identified transition\\u000a steps in the pH range 2–13.5. The ability to change conformation makes BSA capable of complexing different ligands from fatty\\u000a acids to cations or drugs and carries them in the bloodstream. Microcalorimetric titration of BSA with NaOH solution was performed\\u000a to measure the

Robert Kun; Márta Szekeres; Imre Dékány

2009-01-01

121

Solid-contact ion-selective electrodes for aromatic cations based on ?-coordinating soft carriers  

Microsoft Academic Search

Ion-selective electrodes (ISEs) based on ?-coordinating carriers were prepared and investigated as potentiometric sensors for aromatic cations, using N-methylpyridinium as a model aromatic cation. Derivatives of tetraphenylborate were studied as charged carriers in plasticized poly(vinyl chloride) membranes. Furthermore, neutral compounds containing ?-coordinating anthryl groups were studied as neutral carriers. Bis(2-ethylhexyl)sebacate (DOS) and 2-nitrophenyl octyl ether (o-NPOE) were used as non-polar

Johan Bobacka; Terhi Alaviuhkola; Vesa Hietapelto; Heli Koskinen; Andrzej Lewenstam; Markku Lämsä; Jouni Pursiainen; Ari Ivaska

2002-01-01

122

Paper-based potentiometric ion sensing.  

PubMed

This paper describes the design and fabrication of ion-sensing electrochemical paper-based analytical devices (EPADs) in which a miniaturized paper reference electrode is integrated with a small ion-selective paper electrode (ISPE) for potentiometric measurements. Ion-sensing EPADs use printed wax barriers to define electrochemical sample and reference zones. Single-layer EPADs for sensing of chloride ions include wax-defined sample and reference zones that each incorporate a Ag/AgCl electrode. In EPADs developed for other electrolytes (potassium, sodium, and calcium ions), a PVC-based ion-selective membrane is added to separate the sample zone from a paper indicator electrode. After the addition of a small volume (less than 10 ?L) of sample and reference solutions to different zones, ion-sensing EPADs exhibit a linear response, over 3 orders of magnitude, in ranges of electrolyte concentrations that are relevant to a variety of applications, with a slope close to the theoretical value (59.2/z mV). Ion-selective EPADs provide a portable, inexpensive, and disposable way of measuring concentrations of electrolyte ions in aqueous solutions. PMID:25197763

Lan, Wen-Jie; Zou, Xu U; Hamedi, Mahiar M; Hu, Jinbo; Parolo, Claudio; Maxwell, E Jane; Bühlmann, Philippe; Whitesides, George M

2014-10-01

123

Isothermal Titration Calorimetry in the Student Laboratory  

ERIC Educational Resources Information Center

Isothermal titration calorimetry (ITC) is the measurement of the heat produced by the stepwise addition of one substance to another. It is a common experimental technique, for example, in pharmaceutical science, to measure equilibrium constants and reaction enthalpies. We describe a stirring device and an injection pump that can be used with a…

Wadso, Lars; Li, Yujing; Li, Xi

2011-01-01

124

Coulometric titration of ketotifen in tablets.  

PubMed

A method for the determination of ketotifen involving its reaction with iodine in an alkaline medium is presented. In coulometric titration using biamperometric end-point detection 0.25-2 micromol (77-618 microg) of ketotifen was successfully determined. The elaborated method was applied to the determination of ketotifen in drugs. PMID:15801682

Ciesielski, W; Zakrzewski, R; Z?obi?ska, U

2005-03-01

125

A Monte Carlo Study of Titrating Polyelectrolytes  

E-print Network

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

Peterson, Carsten

126

A Monte Carlo Study of Titrating Polyelectrolytes  

E-print Network

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

Peterson, Carsten

127

Titration Calculations with Computer Algebra Software  

ERIC Educational Resources Information Center

This article examines the symbolic algebraic solution of the titration equations for a diprotic acid, as obtained using "Mathematica," "Maple," and "Mathcad." The equilibrium and conservation equations are solved symbolically by the programs to eliminate the approximations that normally would be performed by the student. Of the three programs,…

Lachance, Russ; Biaglow, Andrew

2012-01-01

128

Tracer monitored titrations: measurement of total alkalinity.  

PubMed

We introduce a new titration methodology, tracer monitored titration (TMT), in which analyses are free of volumetric and gravimetric measurements and insensitive to pump precision and reproducibility. Spectrophotometric monitoring of titrant dilution, rather than volume increment, lays the burden of analytical performance solely on the spectrophotometer. In the method described here, the titrant is a standardized mixture of acid-base indicator and strong acid. Dilution of a pulse of titrant in a titration vessel is tracked using the total indicator concentration measured spectrophotometrically. The concentrations of reacted and unreacted indicator species, derived from Beer's law, are used to calculate the relative proportions of titrant and sample in addition to the equilibrium position (pH) of the titration mixture. Because the method does not require volumetric or gravimetric additions of titrant, simple low-precision pumps can be used. Here, we demonstrate application of TMT for analysis of total alkalinity (A(T)). High-precision, high-accuracy seawater A(T) measurements are crucial for understanding, for example, the marine CaCO3 budget and saturation state, anthropogenic CO2 penetration into the oceans, calcareous phytoplankton blooms, and coral reef dynamics. We present data from 286 titrations on three types of total alkalinity standards: Na2CO3 in 0.7 mol kg x soln(-1) NaCl, NaOH in 0.7 mol kg x soln(-1) NaCl, and a seawater Certified Reference Material (CRM). Based on Na2CO3 standards, the accuracy and precision are +/-0.2 and +/-0.1% (4 and 2 micromol kg x soln(-1) for A(T) approximately 2100-2500 micromol kg x soln(-1), n = 242), using low-precision solenoid pumps to introduce sample and titrant. Similar accuracy and precision were found for analyses run 42 days after the initial experiments. Excellent performance is achieved by optimizing the spectrophotometric detection system and relying upon basic chemical thermodynamics for calculating the equivalence point. Although applied to acid-base titrations in this paper, the approach should be generally applicable to other types of titrations. PMID:16536416

Martz, Todd R; Dickson, Andrew G; DeGrandpre, Michael D

2006-03-15

129

Amplified potentiometric transduction of DNA hybridization using ion-loaded Karin Y. Chumbimuni-Torres,a  

E-print Network

signaling ions using a Ca2+ ion-selective electrode (ISE). The high loading yield of nearly one million liposomes a useful addition to the armory of potentiometric bioassays. Introduction Potentiometric ion-selectiveAmplified potentiometric transduction of DNA hybridization using ion-loaded liposomes Karin Y

Zhang, Liangfang

130

Highly selective and sensitized spectrophotometric determination of iron (III) following potentiometric study.  

PubMed

A simple, selective and sensitized spectrophotometric method for determination of trace amounts of Fe3+ ion in tap and waste water solutions has been described. The spectrophotometric determination of Fe3+ ion using Ferron in the presence of N,N-Dodecytrimethylammonium bromide (DTAB) has been carried out. The Beer's law is obeyed over the concentration range of 0.05-2.6 microg mL(-1) of Fe3+ ion with the relative standard deviation (RSD %) <0.2% and the molar absorptivity of complexes in pH 3.5 is 3.8 x 10(3) L mol(-1) cm(-1). Potentiometric pH titration has been used for prediction of protonation constants of ferron, and evaluating its stoichiometry and respective stability constant with Fe3+ ion. As it is obvious the most likely species of ferron alone and its complexes are LH (log = 7.64), LH2 (logK = 10.52), LH3 (logK = 11.74) and ML2 (logbeta = 23.68), ML3 (logbeta = 23.68), ML3H (logbeta = 23.68), ML3H2 (logbta = 23.68) and ML(OH)2 (logbeta = 23.68) respectively. PMID:17970298

Shokrollahi, Ardeshir; Ghaedi, Mehrorang; Rajabi, Hamid Reza

2007-09-01

131

Potentiometric determination of antimony in metal(II) hexafluoroantimonates(V).  

PubMed

The purpose of this study was to develop an accurate and precise analytical procedure for the determination of the content of antimony in coordination compounds of metal(II) hexafluoroantimonates(V) (M(SbF(6))(2) compounds, where M=Mg, Ca, Sr or Ba) synthesized in our laboratory. The major problem was to find an appropriate reagent for reductive decomposition of SbF(6)(-) to Sb(3+) required for the determination of antimony by redox titration. Effective reduction of Sb(5+) regardless of the metal M bound to SbF(6)(-) species was achieved using metallic aluminium powder in acidic medium. Precipitated Sb(0) was quantitatively reoxidized to Sb(3+) and determined potentiometrically with KBrO(3) or KMnO(4). Other metals were determined complexometrically with disodium ethylenediaminetetraacetic acid (EDTA). Highly accurate and reproducible results were obtained in the concentration range 5-25 mg Sb with an RSD smaller than 0.6%. Antimony-fluoro-hydroxo species and fluoride did not interfere with the complexometric determinations of other metals with EDTA. The developed method enabled, for the first time, complete elemental chemical analysis of M(SbF(6))(2) compounds in the bulk form. PMID:18968810

Ponikvar, M; Pihlar, B; Zemva, B

2002-10-16

132

[Estimation of sulfhydryl groups by laboratory titrator T-201].  

PubMed

A method for estimating sulfhydryl groups by laboratory titrator T-201 is proposed. It consists in culonometric titration of SH-groups by silver ions. The method is highly sensitive and reproducible. PMID:7378573

Aleksidze, N G; Koshoridze, N I

1980-01-01

133

Graphical evaluation of complexometric titration curves.  

PubMed

A graphical method, based on logarithmic concentration diagrams, for construction, without any calculations, of complexometric titration curves is examined. The titration curves obtained for different kinds of unidentate, bidentate and quadridentate ligands clearly show why only chelating ligands are usually used in titrimetric analysis. The method has also been applied to two practical cases where unidentate ligands are used: (a) the complexometric determination of mercury(II) with halides and (b) the determination of cyanide with silver, which involves both a complexation and a precipitation system; for this purpose construction of the diagrams for the HgCl(2)/HgCl(+)/Hg(2+) and Ag(CN)(2)(-)/AgCN/CN(-) systems is considered in detail. PMID:18963841

Guinon, J L

1985-04-01

134

Kinetic Titration Series with Biolayer Interferometry  

PubMed Central

Biolayer interferometry is a method to analyze protein interactions in real-time. In this study, we illustrate the usefulness to quantitatively analyze high affinity protein ligand interactions employing a kinetic titration series for characterizing the interactions between two pairs of interaction patterns, in particular immunoglobulin G and protein G B1 as well as scFv IC16 and amyloid beta (1–42). Kinetic titration series are commonly used in surface plasmon resonance and involve sequential injections of analyte over a desired concentration range on a single ligand coated sensor chip without waiting for complete dissociation between the injections. We show that applying this method to biolayer interferometry is straightforward and i) circumvents problems in data evaluation caused by unavoidable sensor differences, ii) saves resources and iii) increases throughput if screening a multitude of different analyte/ligand combinations. PMID:25229647

Frenzel, Daniel; Willbold, Dieter

2014-01-01

135

Spectrophotometric titration of zirconium in siliceous materials.  

PubMed

An accurate and selective complexometric titration procedure based upon a spectrophotometrically detected end-point has been developed for the determination of zirconium in glasses, glass-ceramics and refractories. A p-bromomandelic acid separation step for zirconium imparts excellent selectivity to the procedure. The method is particularly important for the 1-5% concentration range where a simple, accurate and selective method for the determination of zirconium has been lacking. PMID:18962344

Sugawara, K F; Su, Y S; Strzegowski, W R

136

LABORATORY EXPERIMENT 6 PRECIPITATION TITRATION WITH SILVER NITRATE.  

E-print Network

LABORATORY EXPERIMENT 6 PRECIPITATION TITRATION WITH SILVER NITRATE. The AgNO3 solution (~0.02 M in the titration of chloride ion with silver nitrate. The first excess of titrant results in the formation of a red Ag2CrO4. Calculations: From the volume of silver nitrate solution used fopr titration, calculate

Nazarenko, Alexander

137

LABORATORY EXPERIMENT 5 PRECIPITATION TITRATION WITH SILVER NITRATE.  

E-print Network

LABORATORY EXPERIMENT 5 PRECIPITATION TITRATION WITH SILVER NITRATE. The AgNO3 solution (~0.02 M in the titration of chloride ion with silver nitrate. The first excess of titrant results in the formation of a red Ag2CrO4. Calculations: From the volume of silver nitrate solution used fopr titration, calculate

Nazarenko, Alexander

138

Determination of carbonate carbon in geological materials by coulometric titration  

USGS Publications Warehouse

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.

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

1985-01-01

139

Analysis of Fish Freshness by Using Metallic Potentiometric Electrodes  

Microsoft Academic Search

We report herein the development of a simple electronic system that uses simple potentiometric electrodes applied to the analysis fish freshness. The array of sensors is built by using metallic electrodes as plain sharp wires or in a thick-film configuration. Experiments on real fish led to the conclusion that gold and silver electrodes are suitable for the development of qualitative

L. Gil; E. Garcia-Breijo; J. M. Barat; R. Martinez-Manez; J. Soto; F. Baena; J. Ibanez; E. Llobet; J. Brezmes

2007-01-01

140

A potentiometric electronic tongue to monitor meat freshness  

Microsoft Academic Search

This paper describes the development of an electronic tongue system for monitoring the freshness of meat. The analysis was made along 14 days on a whole piece of pork loin stored under refrigeration. The electronic tongue system is made by an array of potentiometric electrodes. Through the use of various multivariate analysis techniques, such as PCA and two types of

Luis Gil; José M. Barat; Diana Baigts; Ramón Martínez-Máñez; Juan Soto; Eduardo Garcia-Breijo; Eduard Llobet

2010-01-01

141

Redox-iodometry: a new potentiometric method.  

PubMed

A new iodometric method for quantifying aqueous solutions of iodide-oxidizing and iodine-reducing substances, as well as plain iodine/iodide solutions, is presented. It is based on the redox potential of said solutions after reaction with iodide (or iodine) of known initial concentration. Calibration of the system and calculations of unknown concentrations was performed on the basis of developed algorithms and simple GWBASIC-programs. The method is distinguished by a short analysis time (2-3 min) and a simple instrumentation consisting of pH/mV meter, platinum and reference electrodes. In general the feasible concentration range encompasses 0.1 to 10(-6) mol/L, although it goes down to 10(-8) mol/L (0.001 mg Cl2/L) for oxidants like active chlorine compounds. The calculated imprecision and inaccuracy of the method were found to be 0.4-0.9% and 0.3-0.8%, respectively, resulting in a total error of 0.5-1.2%. Based on the experiments, average imprecisions of 1.0-1.5% at c(Ox)>10(-5) M, 1.5-3% at 10(-5) to 10(-7) M, and 4-7% at <10(-7) M were found. Redox-iodometry is a simple, precise, and time-saving substitute for the more laborious and expensive iodometric titration method, which, like other well-established colorimetric procedures, is clearly outbalanced at low concentrations; this underlines the practical importance of redox-iodometry. PMID:15981007

Gottardi, Waldemar; Pfleiderer, Jörg

2005-07-01

142

Fibre-optic titrations-IV Direct complexometric titration of aluminium(III) with DCTA.  

PubMed

The end-point of the direct complexometric titration of Al(3+) in pH 4.6 solution can be determined by monitoring the fluorescence intensity of the aluminium-morin complex, by use of a bifurcated fibre-optic light guide. The method allows the determination of aluminium in the 1-800 ppm range with good precision. The procedure is applicable even when the solutions are strongly coloured or turbid, but because of the slow complexation kinetics requires a titration time of about 20 min. PMID:18964217

Wolfbeis, O S; Schaffar, B P; Chalmers, R A

1986-11-01

143

New challenges for pharmaceutical formulations and drug delivery systems characterization using isothermal titration calorimetry.  

PubMed

Long viewed as the 'method of choice' for characterizing thermodynamics and stoichiometry of molecular interactions, with high sensitivity, isothermal titration calorimetry (ITC) has been applied to many areas of pharmaceutical analysis. This review highlights ITC employment to measure binding thermodynamics and their use for pharmaceutical formulations and drug delivery system characterization particularly cyclodextrin-guest interactions, investigation of micellar-based systems, polyelectrolytes, nucleic acid interactions with multivalent cations and the optimization of DNA targeting and delivery. Furthermore, the potential of ITC for the characterization of different functionalities carried by nanoparticles as well as their interaction with living systems was outlined. PMID:18617012

Bouchemal, Kawthar

2008-11-01

144

Modeling complexometric titrations of natural water samples.  

PubMed

Complexometric titrations are the primary source of metal speciation data for aquatic systems, yet their interpretation in waters containing humic and fulvic acids remains problematic. In particular, the accuracy of inferred ambient free metal ion concentrations and parameters quantifying metal complexation by natural ligands has been challenged because of the difficulties inherent in calibrating common analytical methods and in modeling the diverse array of ligands present. This work tests and applies a new method of modeling titration data that combines calibration of analytical sensitivity (S) and estimation of concentrations and stability constants for discrete natural ligand classes ([Li]T and Ki) into a single step using nonlinear regression and a new analytical solution to the one-metal/two-ligand equilibrium problem. When applied to jointly model data from multiple titrations conducted at different analytical windows, it yields accurate estimates of S, [Li]T, Ki, and [Cu2+] plus Monte Carlo-based estimates of the uncertainty in [Cu2+]. Jointly modeling titration data at low-and high-analytical windows leads to an efficient adaptation of the recently proposed "overload" approach to calibrating ACSV/CLE measurements. Application of the method to published data sets yields model results with greater accuracy and precision than originally obtained. The discrete ligand-class model is also re-parametrized, using humic and fulvic acids, L1 class (K1 = 10(13) M(-1)), and strong ligands (L(S)) with K(S) > K1 as "natural components". This approach suggests that Cu complexation in NW Mediterranean Sea water can be well represented as 0.8 +/- 0.3/0.2 mg humic equiv/L, 13 +/- 1 nM L1, and 2.5 +/- 0.1 nM L(S) with [CU]T = 3 nM. In coastal seawater from Narragansett Bay, RI, Cu speciation can be modeled as 0.6 +/- 0.1 mg humic equiv/L and 22 +/- 1 nM L1 or approximately 12 nM L1 and approximately 9 nM L(S), with [CU]T = 13 nM. In both waters, the large excess (approximately 10 nM) of high-affinity, Cu-binding ligands over [CU]T results in low equilibrium [Cu2+] of 10(-14.5 +/- 0.2) M and 10(-13.3 +/- 0.4) M, respectively. PMID:12731837

Hudson, Robert J M; Rue, Eden L; Bruland, Kenneth W

2003-04-15

145

Alkaline Titrations of poly(dG-dC)·poly(dG-dC): Microemulsion Versus Solution Behavior  

Microsoft Academic Search

PolyGC was titrated with a strong base in the presence of increasing concentrations of NaCl (from 0.00 to 0.60M) either in water solution or with the polynucleotide solubilized in the aqueous core of reverse micelles, i.e., the cationic quaternary water-in-oil microemulsion CTAB\\/n-hexane\\/n-pentanol\\/water. The results for matched samples in the two media were compared. CD and UV spectroscopies and, for the

Marta Airoldi; Giuseppe Gennaro; Marcello Giomini; Anna Maria Giuliani; Mauro Giustini

2007-01-01

146

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

PubMed Central

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

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

2013-01-01

147

Measuring titratable alkalinity by single versus double endpoint titration: An evaluation in two cyprinodont species and implications for characterizing net H+  

E-print Network

Measuring titratable alkalinity by single versus double endpoint titration: An evaluation in two Fundulus heteroclitus Na+ homeostasis Acid­base balance Titratable alkalinity Ammonia Net H+ transport were the result of using double endpoint titrations to measure titratable alkalinity fluxes

Grosell, Martin

148

Zinc Selective Ionophores for Potentiometric and Optical Sensors  

Microsoft Academic Search

Iminodiacetamide derivatives were synthesized and studied as ionophores in plasticized poly(vinyl chloride) membranes with potentiometric and optical transduction. The N-benzyl and N-phenyl derivatives proved to have a distinct zinc selectivity preferring Zn over Ca, Na by factors of 6×10 and 3×10. respectively. All ionophores exhibit a serious proton interference (log K Zn , H - 6) which suggests that all

Ernö Lindner; Mária Horváth; Klára Tóth; Ernö Pungor; István Bitter; Béla Ágai; László Töke

1992-01-01

149

Automated potentiometric electrolyte analysis system. [for use in weightlessness  

NASA Technical Reports Server (NTRS)

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.

1973-01-01

150

FIA titrations of ephedrine in pharmaceutical formulations with a PVC tetraphenylborate tubular electrode.  

PubMed

A flow injection system for the titration of ephedrine in pharmaceutical products with potentiometric detection was developed. For this purpose a tetraphenylborate tubular electrode was constructed. The electrode was prepared without inner reference solution and with a PVC membrane based on tetrapentylammonium tetraphenylborate as ion exchanger and 2-nitrophenylphenyl ether as mediator solvent. Its operational characteristics were evaluated in a low dispersion manifold and compared with more conventionally shaped electrodes using the same sensor. In the pH range 2.5-11.5, the electrodes showed linear response between 3.8 x 10(-6) and 0.1 M with a slope of -56.4 mV/log[BPh4]. Ephedrine determinations in pharmaceutical products were carried out in a single channel manifold with a mixing chamber incorporated and using the tubular electrode as detector. Recovery rates of 98.6 +/- 2.5% were obtained in the analysis of tables, nasal drops and syrups with a sampling rate of about 60 h-1. PMID:9696556

Alçada, M N; Lima, J L; Montenegro, M C

1995-04-01

151

Potentiometric-surface map, 1993, Yucca Mountain and vicinity, Nevada  

SciTech Connect

The revised potentiometric surface map here, using mainly 1993 average water levels, updates earlier maps of this area. Water levels are contoured with 20-m intervals, with additional 0.5-m contours in the small-gradient area SE of Yucca Mountain. Water levels range from 728 m above sea level SE of Yucca to 1,034 m above sea level north of Yucca. Potentiometric levels in the deeper parts of the volcanic rock aquifer range from 730 to 785 m above sea level. The potentiometric surface can be divided into 3 regions: A small gradient area E and SE of Yucca, a moderate-gradient area on the west side of Yucca, and a large-gradient area to the N-NE of Yucca. Water levels from wells at Yucca were examined for yearly trends (1986-93) using linear least-squares regression. Of the 22 wells, three had significant positive trends. The trend in well UE-25 WT-3 may be influenced by monitoring equipment problems. Tends in USW WT-7 and USW WTS-10 are similar; both are located near a fault west of Yucca; however another well near that fault exhibited no significant trend.

Tucci, P.; Burkhardt, D.J.

1995-12-31

152

The acid-base titration of montmorillonite  

NASA Astrophysics Data System (ADS)

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.

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

2003-12-01

153

Automated titration method for use on blended asphalts  

DOEpatents

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.

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

2012-08-07

154

Automated Titrations with AN Alternate Flow, Linear Speed, Variation System. Applications to Amperometric, Biamperometric, and Spectrophotometric Titrations  

Microsoft Academic Search

The “alternate flow” method was recently proposed as a solution to the problem connected to the requirement of frequent calibrations of systems utilizing peristaltic pumps.This method was successfully applied to amperometric titrations of the ferrous–ceric system, biamperometric titrations of arsenite–iodine and thiosulfate–iodine systems, and spectrophotometric titrations of ferrous–permanganate and arsenite–iodine systems. Equivalence point determination is possible in the micromolar range

Tatyana A. Bendikov; Chaim N. Yarnitzky

2002-01-01

155

Spectrophotometric, spectrofluorimetric, and potentiometric assays of cetyltrimethylammonium bromide in industrial wastewater samples.  

PubMed

This work deals with spectrophotometric, spectrofluorimetric, and potentiometric analyses of cetyltrimethylammonium bromide (CTAB) cationic detergent. The spectrophotometric procedure depends on measuring the absorbance of its binary complex with eosin yellow in Britton-Robinson buffer (pH 4) at Lambda max 547 nm in the range of 2.0-14.0 microg/mL with an accuracy of 100.15 +/- 0.54%. The spectrofluorimetric procedure depends on determining the quenching of the fluorescence intensity of fluorescein dye by CTAB in the presence of borate buffer at Lambda em = 500 nm, Lambda ex = 304 nm, in the range of 2.90-14.50 microg/mL with an accuracy of 99.81 + 0.33%. The electrochemical procedure describes an ionophore-based technique using a graphite sensor to measure 0.036 microg/mL and showed an accuracy of 100.11 +/- 0.61%. The experimental conditions affecting each of the three suggested procedures were studied and optimized. All the developed procedures were validated and satisfactorily applied for the determination of CTAB in industrial wastewater samples. PMID:25145154

Hussein, Lobna Abdel Aziz; Fares, Nermine Victor; El-Kosasy, Amira Mabrouk

2014-01-01

156

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

PubMed Central

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

Ahmadi, Farhad; Asaadi, Nasim

2013-01-01

157

Calibrationless Determination of Creatinine and Ammonia by Coulometric Flow Titration  

Microsoft Academic Search

A precise and sensitive working microflow titration procedure was developed to determine creatinine and ammonia in urine samples. This procedure is based on enzymatic conversion of creatinine, gas diffusional membrane separation of the released ammonia into an acid acceptor stream, and coulometric titration of ammonia with hypobromite. The hypobromite is formed after the electrogeneration of bromine in an electrolyte containing

Z. K. He; B. Fuhrmann; U. Spohn

2000-01-01

158

Spectrophotometric Titration of a Mixture of Calcium and Magnesium.  

ERIC Educational Resources Information Center

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…

Fulton, Robert; And Others

1986-01-01

159

Quantitative Analysis of Sulfate in Water by Indirect EDTA Titration  

ERIC Educational Resources Information Center

The determination of sulfate concentration in water by indirect EDTA titration is an instructive experiment that is easily implemented in an analytical chemistry laboratory course. A water sample is treated with excess barium chloride to precipitate sulfate ions as BaSO[subscript 4](s). The unprecipitated barium ions are then titrated with EDTA.…

Belle-Oudry, Deirdre

2008-01-01

160

Successive determination of praseodymium and ytterbium by coulometric complexometric titration  

Microsoft Academic Search

A method is described for the successive coulometric complexometric titration of microgram levels of light and heavy rare earth elements. The total amount of light and heavy rare earth elements is titrated by electrogenerating titrant EDTA on the mercury pool as a cathode. Then, the mercury pool is switched as an anode, electrogenerating Hg\\/sup 2 +\\/, and is used to

S. Chun-Nian; L. Jing-Ci; N. Qi-Dao; C. Mou-Sen

1982-01-01

161

A Closer Look at Acid-Base Olfactory Titrations  

ERIC Educational Resources Information Center

Olfactory titrations using raw onions and eugenol as acid-base indicators are reported. An in-depth investigation on olfactory titrations is presented to include requirements for potential olfactory indicators and protocols for using garlic, onions, and vanillin as acid-base olfactory indicators are tested.

Neppel, Kerry; Oliver-Hoyo, Maria T.; Queen, Connie; Reed, Nicole

2005-01-01

162

Characterization of Petroleum Sulfonates by a Nonaqueous Titration Method  

Microsoft Academic Search

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

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

1981-01-01

163

Spectrophotometric titration of ionisable groups in proteins: a theoretical study  

NASA Astrophysics Data System (ADS)

A simple theoretical model is proposed for evaluation of the optical titration behaviour of tyrosyl and carboxyl residues in proteins. The p K values involved in the model are computed using the semi-empirical method. The titration curves are calculated using the values of the molar absorption differences for tyrosyl residues in the ultraviolet (UV) region at 245 and 295 nm, and for carboxyl residues in the infrared (IR) region at 1565 and 1707 cm -1, respectively. The theoretical tyrosyl titration curves are compared with the experimental data for lysozyme, myoglobin and chymotrypsinogen (available in the literature). This approach provides a good tool for distinguishing between the ionisation and the conformational changes in the alkaline range. The quantitative evaluation of the change of molar extinction coefficients as a function of pH in the case of carboxyl titration for lysozyme, trypsin and cytochrome c shows a good agreement with the experimental titration data.

Miteva, Maria; Shosheva, Alexandra; Atanasov, Boris

2000-09-01

164

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

USGS Publications Warehouse

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.

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

1975-01-01

165

Zinc selective ionophores for potentiometric and optical sensors  

SciTech Connect

Iminodiacetamide derivatives were synthesized and studied as ionophores in plasticized poly(vinyl chloride) membranes with potentiometric and optical transduction. The N-benzyl and N-phenyl derivatives proved to have a distinct zinc selectivity preferring Zn{sup 2+} over Ca{sup 2+}, Na{sup +} by factors of 6x10{sup 5} and 3x10{sup 4}, respectively. All ionophores exhibit a serious proton interference (log K{sup pot}{sub Zn{sup ++}}, {sub H{sup +}} {approximately} 6) which suggests that all application of this type of ionophores based sensors are limited to hydrogen ion buffer solution at pH {>=} 6.

Lindner, E.; Horvath, M.; Toth, K.; Pungor, E.; Bitter, I.; Agai, B.; Toeke, L. (Technical Univ. of Budapest (Hungary))

1992-03-01

166

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

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)

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

1976-01-01

167

Response of DNA fragments to potentiometric sensors studied using HPLC.  

PubMed

Potentiometric sensors are studied as viable candidates for the construction of high throughput DNA arrays. For preliminary investigations, such sensors were used in an HPLC setup in the present work. This avoided errors due to ionic contaminants or additives in the commercial samples. The oligonucleotides dT(10), dT(20) and dT(30) were used as test substances. The potentiometric sensors were of the coated wire type, containing PVC, DOP, MTDDACl and a synthetic podand urea receptor. The HPLC system consisted of a reversed phase column eluted with a phosphate buffer, triethylammoniumacetate (TEAA), and an acetonitrile gradient. Molar responses and sensitivities increased with increasing chain length of oligonucleotides, yielding detection limits as low as 10(-6)M (dT(30), injected concentration). The slopes of the calibration graphs were at least 23 mV/decade (dT(10)), which was much higher than expected. The results are discussed in view of the potential use of this sensor type in high throughput microarrays. PMID:17979638

Nagels, Luc J; Everaert, Joseph; Bohets, Hugo; Del Favero, Jurgen; Goossens, Dirk; Robbens, Johan; Pietraszkiewicz, Marek; Pietraszkiewicz, Oksana

2007-08-01

168

Determination of urine ionic composition with potentiometric multisensor system.  

PubMed

The ionic composition of urine is a good indicator of patient?s general condition and allows for diagnostics of certain medical problems such as e.g., urolithiasis. Due to environmental factors and malnutrition the number of registered urinary tract cases continuously increases. Most of the methods currently used for urine analysis are expensive, quite laborious and require skilled personnel. The present work deals with feasibility study of potentiometric multisensor system of 18 ion-selective and cross-sensitive sensors as an analytical tool for determination of urine ionic composition. In total 136 samples from patients of Urolithiasis Laboratory and healthy people were analyzed by the multisensor system as well as by capillary electrophoresis as a reference method. Various chemometric approaches were implemented to relate the data from electrochemical measurements with the reference data. Logistic regression (LR) was applied for classification of samples into healthy and unhealthy producing reasonable misclassification rates. Projection on Latent Structures (PLS) regression was applied for quantitative analysis of ionic composition from potentiometric data. Mean relative errors of simultaneous prediction of sodium, potassium, ammonium, calcium, magnesium, chloride, sulfate, phosphate, urate and creatinine from multisensor system response were in the range 3-13% for independent test sets. This shows a good promise for development of a fast and inexpensive alternative method for urine analysis. PMID:25281140

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

2015-01-01

169

Spray-coated all-solid-state potentiometric sensors.  

PubMed

A novel fully spray coating-based method of the preparation of all-solid-state ion-selective electrodes of simplified construction is proposed. This method is an alternative for screen-printed electrodes used sometimes in potentiometric applications. The benefits of the herein-proposed approach include fully automatic sensor preparation and minimized use of chemicals allowing for the production of low-cost sensors that can be applied as disposables. A layer of spray-coated carbon nanotubes on an inert support was used both as an electrical lead and as a transducer, to simplify sensor layout and to avoid the possible problems of changing in-time composition of this layer, as previously observed in the case of screen-printed supporting electrodes in potentiometric applications. The ion-selective poly(vinyl chloride)-based membrane and the insulator layer were also spray-coated. The obtained sensors, as the model system potassium-selective sensors were prepared and characterized with analytical parameters well comparable with that of conventional, all-solid-state, ion-selective electrodes. In addition, the applicability of the herein-proposed approach to prepare other ion-selective electrodes was tested on examples of H(+) and Cl(-) sensors. PMID:25270688

Jaworska, Ewa; Schmidt, Morten; Scarpa, Giuseppe; Maksymiuk, Krzysztof; Michalska, Agata

2014-10-15

170

A new potentiometric sensor for the determination of ?-amylase activity.  

PubMed

A platinum redox sensor for the direct potentiometric determination of ?-amylase concentration has been described. The sensor measured the amount of triiodide released from a starch-triiodide complex, which was correlated with the ?-amylase activity after biocatalytic starch degradation. The composition and stability of the potassium triiodide solution was optimized. The starch-triiodide complex was characterized potentiometrically at variable starch and triiodide concentrations. The response mechanism of the platinum redox sensor towards ?-amylase was proposed and the appropriate theoretical model was elaborated. The results obtained using the redox sensor exhibited satisfactory accuracy and precision and good agreement with a standard spectrophotometric method and high-sensitive fully automated descret analyser method. The sensor was tested on pure ?-amylase (EC 3.2.1.1, Fluka, Switzerland), industrial granulated ?-amylase Duramyl 120 T and an industrial cogranulate of protease and ?-amylase Everlase/Duramyl 8.0 T/60 T. The detection limit was found to be 1.944 mU for ?-amylase in the range of 0-0.54 U (0-15 ?g), 0.030 mKNU for Duramyl 120 T in the range of 0-9.6 mKNU (0-80 ?g) and 0.032 mKNU for Everlase/Duramyl 8.0 T/60 T in the range of 0-9.24 mKNU (0-140 ?g). PMID:21238759

Sakac, Nikola; Sak-Bosnar, Milan; Horvat, Marija; Maduni?-Caci?, Dubravka; Szechenyi, Aleksandar; Kovacs, Barna

2011-02-15

171

Automatic photometric titrations of calcium and magnesium in carbonate rocks  

USGS Publications Warehouse

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.

Shapiro, L.; Brannock, W.W.

1955-01-01

172

[Determination of the cations concentrations in the dialysis fluid by an atom absorption spectrometer].  

PubMed

The atom absorption spectrometer is introduced to determine the cation concentrations such as potassium, sodium, calcium and magnesium in the dialysis fluid. They are accurately determined by proper preparation and correct dilution ratio under the optimized measuring conditions. Compared with the current arbitrate methods (EDTA titration determination of calcium and magnesium), it supplements the methods of international and industrial standards for determination of cations. PMID:18438053

Fan, Bo; Li, Yuan; Jiang, Xi; Ma, Chun-Bao; Fu, Rui-zhi; Zhang, Peng

2008-01-01

173

Chemically modified carbon paste electrode for the potentiometric flow injection analysis of piribedil in pharmaceutical preparation and urine.  

PubMed

A new carbon paste electrode selective for piribedil (PD) was prepared and fully characterized in terms of composition, usable pH range, response time and thermal stability. The electrode active recognition is by liquid ion-exchange mechanism via the use of piribedil phosphomolybdate as ion-exchanger dissolved in tricresyl phosphate as a more suitable solvent mediator for the paste. The modified electrode showed a Nernstian slope of 58.4+/-0.6 mV over the concentration range of 7.5 x 10(-7) to 1 x 10(-3)M with an average recovery of 98.3-101.0% and R.S.D. of 0.45-1.31%. The electrode exhibits good selectivity for PD with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The developed electrode was successfully used for the potentiometric determination of PD in its aqueous solutions, pharmaceutical preparation, and urine in batch and flow injection analysis (FIA). PMID:15967290

Ibrahim, Hosny

2005-07-15

174

Potentiometric-level monitoring program: Mississippi and Louisiana. Annual status report for fiscal year 1984  

SciTech Connect

Potentiometric-level data presented in this report were collected from October 1983 through September 1984 at 79 wells in Mississippi and Louisiana. These wells are located near Richton and Cypress Creek Domes in Mississippi and Vacherie Dome in Louisiana. Fourteen wells were added to the program during this period. Two of these wells were not measurable. Two wells previously unmeasurable were located and measured. One well was destroyed during military maneuvers in the area. Analysis of the data indicated minimal, if any, change in potentiometric levels during the past year in the Citronelle, Hattiesburg, Cockfield, Sparta, and Wilcox Formations in Mississippi. A continuing decline in potentiometric levels, ranging from 0.3 to 0.6 foot per year, occurred in the wells screened in the caprock at Richton and Cypress Creek Domes. The Catahoula Formation experienced a continuing decline in potentiometric levels of about 2 feet per year. Two wells in the Cook Mountain Formation showed a continuing rise in potentiometric levels ranging from 8 to 30 ft during the past fiscal year. Wells screened in the Austin Formation in Louisiana showed a fall in potentiometric levels of 2 to 3 ft over the past fiscal year. Other formations in Louisiana generally showed no change in potentiometric levels over the past year. 26 refs., 2 figs., 3 tabs.

Not Available

1986-07-01

175

THE TITRATION OF YELLOW FEVER VIRUS IN STEGOMYIA MOSQUITOES  

PubMed Central

Titrations were made of yellow fever virus in stegomyia mosquitoes, using rhesus monkeys as test animals. It was found that: (a) The average mosquito immediately after engorging on highly infectious blood contained between 1 and 2 million lethal doses of virus. The titer of freshly ingested blood was as high as 1 billion lethal doses of virus per cubic centimeter. (b) During the fortnight succeeding a meal on infectious blood there occurred a reduction of titratable virus to not more than 1 per cent of that present in the freshly fed insects. (c) The titer was somewhat higher at later periods. This rise in titer signified possibly not a multiplication, but merely an increase of extracellular virus and of that easily freed by grinding to a titratable form. (d) At no later stage did the quantity of titratable virus equal that demonstrable in freshly fed insects. PMID:19870190

Davis, Nelson C.; Frobisher, Martin; Lloyd, Wray

1933-01-01

176

A Titration Technique for Demonstrating a Magma Replenishment Model.  

ERIC Educational Resources Information Center

Conductiometric titrations can be used to simulate subduction-setting volcanism. Suggestions are made as to the use of this technique in teaching volcanic mechanisms and geochemical indications of tectonic settings. (JN)

Hodder, A. P. W.

1983-01-01

177

Microscope Titration and Extraction of DNA from Liver.  

ERIC Educational Resources Information Center

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)

Mayo, Lois T.; And Others

1993-01-01

178

Semiautomatic catalytic titration of palladium and gold(III)  

Microsoft Academic Search

Summary A semiautomatic potentiometric method is described for the catalytic titrimetric determination ofµg amounts of palladium or gold. The method is based on the inhibitory effect of palladium and gold(III) ions on the iodide-catalyzed Ce(IV)-As(III) reaction, and is rapid, simple, accurate, precise and sensitive. The indicator reaction is monitored with a platinum electrode and the end-point is obtained from the

T. P. Hadjiioannou; M. M. Timotheou

1977-01-01

179

A compact titration configuration for process analytical applications  

Microsoft Academic Search

A configuration for wet-chemical process analysis is proposed consisting of one piston burette, a selector valve and a reaction cell. The feasibility of the configuration is shown by optimising a simple acid\\/base titration setup. Other applications of this configuration for complexometric-, precipitation-, and back-titration, standard addition and photometric methods are discussed. The configuration offers great flexibility towards these methods without

Robert Hoogendijk

1999-01-01

180

High frequency titration of amines in nonaqueous solutions  

E-print Network

HIGH FREQUENCY TITRATION OF A%INES IN NONAQUEOUS SOLUTIONS A Thesis William Byron Witmer Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in partial fulfillment of the requirements for the degree of MASTER... OF SCIENCE January 1958 Major Subject: Chemistry HIGH FREQUENCY TITRATION OF ABIINES IN NONAQUEOUS SOLUTIONS A Thesis William Byron Witmer Approved as to style and content by: hairman of ommit ead of Department or Student Advisor January 1958...

Witmer, William Byron

2012-06-07

181

Hydration and Lyotropic Melting of Amphiphilic Molecules: A Thermodynamic Study Using Humidity Titration Calorimetry.  

PubMed

The hydration of the lipid 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and of the cationic detergent dodecyltrimethylammonium bromide (DTAB) has been studied by means of isothermal titration calorimetry (ITC), gravimetry, and infrared (IR) spectroscopy. During the experiments films of the amphiphiles are perfused by an inert gas of variable relative humidity. The measurement of adsorption heats using ITC represents a new adaptation of adsorption calorimetry which has been called the humidity titration technique. This method yields the partial molar enthalpy of water upon adsorption. It is found to be endothermic with respect to the molar enthalpy of water on condensation for the water molecules which interact directly with the headgroups of POPC and DTAB. Consequently, the spontaneous hydration of the amphiphiles is entropy driven in an aqueous environment. IR spectroscopy shows that hydration is accompanied by the increase in the conformational and/or motional freedom of the amphiphilic molecules upon water binding. In particular, a lyotropic chain melting transition is induced at a certain characteristic relative humidity. This event is paralleled by the adsorption of water. The corresponding exothermic adsorption heat is consumed completely (POPC) or partially (DTAB) by the hydrocarbon chains upon melting. Differential scanning calorimetry was used as an independent method to determine transition enthalpies of the amphiphiles at a definite hydration degree. Water binding onto the headgroups is discussed in terms of hydrogen bonding and polar interactions. The adsorption isotherms yield a number of approximately 2.6 tightly bound water molecules per POPC and DTAB molecule. Copyright 1999 Academic Press. PMID:10607439

Binder; Kohlstrunk; Heerklotz

1999-12-15

182

Complexometric Titrations: Competition of Complexing Agents in the Determination of Water Hardness with EDTA  

NASA Astrophysics Data System (ADS)

The competition of complexing agents for the same metal ion and the formation of colored metal-ion complexes is demonstrated with the use of an overhead projector. This demonstration can be used to emphasize both the relevance of the relative values of formation constants in the complexation of metal cations and the applicability of complexometric titrations in quantitative chemical analysis. The demonstration is based on the traditional determination of water hardness in which EDTA is used as the titrant that complexes Mg2+ and Ca2+ ions. The color change that signals the end of the titration represents the successful removal of the Mg2+ ions from the metallochromic indicator Calmagite. This removal is possible because the value of the formation constant of the [Mg(EDTA)]2- complex is about 3 orders of magnitude greater than that corresponding to the [Mg(Calmagite)]- complex. The color change from wine-red (metal-bound indicator) to blue (unbound indicator) can be seen clearly in a large classroom with the use of overhead projection.

Yappert, M. Cecilia; Dupre, Donald B.

1997-12-01

183

Chloride sensor based on a new potentiometric transducer  

NASA Astrophysics Data System (ADS)

A novel type of a miniature transducer with back-side contacts for potentiometric sensors is described in this paper. A back-side contact type transducer is especially suitable for the design of flow chemical sensors. The sensor structure is compatible with a flow-head used for multiparameter measurements. Unmodified transducers can be used as chloride sensors. Moreover if the chip is covered with ion-selective membrane it is possible to construct a sensor for given ion. Measurement properties of the designed transducers were determined in the experiments with chloride ions as well as interfering ions. Two types of the sensors were constructed: for flow or batch measurements. A reference electrode was integrated with the sensor in the latter version.

Dybko, Artur; Wroblewski, Wojciech; Brzozka, Zbigniew

2003-09-01

184

[Determination of lead in urine by differential potentiometric stripping analysis].  

PubMed

In the determination of lead in urine by differential potentiometric stripping analysis (DPSA) urine samples are acidified with hydrochloric acid to a total concentration equal to 0.2 mol/L without prior digestion with mineral acids. The sample is pre-electrolyzed at -1.2V (Vs SCE) for 80 seconds by glassy-carbon electrode coated with mercury. The lead concentrations are evaluated by means of standard addition. Detection limit of the method is 2ppb. The linear relationship occurs in the range of 0-150ppb. The relative standard deviations are 1.6% and the recovery of lead in urine samples is 89.5-110.0%. Compared with dithizone method, this method shows no significant difference in the results obtained. PMID:2625342

Sun, X X; Zhang, M Y; Guo, S J

1989-09-01

185

Modeling potentiometric measurements in topological insulators including parallel channels  

NASA Astrophysics Data System (ADS)

The discovery of spin-polarized states at the surface of three-dimensional topological insulators (TI) like Bi2Te3 and Bi2Se3 motivates intense interests in possible electrical measurements demonstrating unique signatures of these unusual states. Here we show that a three-terminal potentiometric set-up can be used to probe them by measuring the voltage change of a detecting magnet upon reversing its magnetization. We present numerical results using a nonequilibrium Green's function (NEGF)-based model to show the corresponding signal quantitatively in various transport regimes. We then provide an analytical expression for the resistance (the measured voltage difference divided by an applied current) that agrees with NEGF results well in both ballistic and diffusive limits. This expression is applicable to TI surface states, two-dimensional electrons with Rashba spin-split bands, and any combination of multiple channels, including bulk parallel states in TI, which makes it useful in analyzing experimental results.

Hong, Seokmin; Diep, Vinh; Datta, Supriyo; Chen, Yong P.

2012-08-01

186

Membrane surface-charge titration probed by gramicidin A channel conductance.  

PubMed Central

We manipulate lipid bilayer surface charge and gauge its influence on gramicidin A channel conductance by two strategies: titration of the lipid charge through bulk solution pH and dilution of a charged lipid by neutral. Using diphytanoyl phosphatidylserine (PS) bilayers with CsCl aqueous solutions, we show that the effects of lipid charge titration on channel conductance are masked 1) by conductance saturation with Cs+ ions in the neutral pH range and 2) by increased proton concentration when the bathing solution pH is less than 3. A smeared charge model permits us to separate different contributions to the channel conductance and to introduce a new method for "bilayer pKa" determination. We use the Gouy-Chapman expression for the charged surface potential to obtain equilibria of protons and cations with lipid charges. To calculate cation concentration at the channel mouth, we compare different models for the ion distribution, exact and linearized forms of the planar Poisson-Boltzmann equation, as well as the construction of a "Gibbs dividing surface" between salt bath and charged membrane. All approximations yield the intrinsic pKain of PS lipid in 0.1 M CsCl to be in the range 2.5-3.0. By diluting PS surface charge at a fixed pH with admixed neutral diphytanoyl phosphatidylcholine (PC), we obtain a conductance decrease in magnitude greater than expected from the electrostatic model. This observation is in accord with the different conductance saturation values for PS and PC lipids reported earlier (, Biochim. Biophys. Acta. 552:369-378) and verified in the present work for solvent-free membranes. In addition to electrostatic effects of surface charge, gramicidin A channel conductance is also influenced by lipid-dependent structural factors. PMID:9746520

Rostovtseva, T K; Aguilella, V M; Vodyanoy, I; Bezrukov, S M; Parsegian, V A

1998-01-01

187

Potentiometric-spectroscopic evaluation of metal-ion complexes by humic fractions extracted from corn tissue  

NASA Astrophysics Data System (ADS)

Humic fraction (HF) functional group-type and content are expected to depend on molecular size, which in turn, is expected to influence formation of heavy-metal complexes. In this study, corn ( Zea mays L .) stalks and leaves were decomposed for an 8-month period to produce water-soluble humic substances. These substances were separated into three water-soluble fractions, HF1, HF2 and HF3, from highest to lowest relative molecular size. Functional group determination showed that carboxylic, and phenolic OH acidity increased as relative molecular size of humic fractions decreased. We also observed decreasing C/O ratios from larger to smaller corn tissue-derived humic fractions, whereas N/C and H/C ratios remained relatively unaffected. Furthermore, using potentiometric titration and FTIR spectroscopy we studied formation of Ca 2+-, Cd 2+-, and Cu 2+-humic fraction complexes and how they were affected by pH and molecular size. We determined that metal-humic complexes exhibited at least two types of functional group-sites with respect to Ca 2+, Cd 2+, and Cu 2+ complexation. Strength of metal-ion humic complexes followed the order Cu 2+>Cd 2+>Ca 2+ and was affected by pH, especially for low affinity sites. Carboxylic groups were most likely the dominant group-sites involved in complex formation. Magnitude of the metal-humic formation constants in the logarithmic form at the lowest equilibrium metal-ion concentration, under the various pH values tested, varied from 5.39 to 5.90 for Ca 2+, 5.36 to 6.01 for Cd 2+, and 6.93 to 7.71 for Cu 2+. Furthermore, the formation constants appeared to be positively influenced by decreasing molecular size of water-soluble humic fraction, and increasing pH. However, our molecular spectra showed that the p Ka of corn humic fractions increased with decreasing relative molecular size and that Cu 2+ was more covalently bonded by humic fractions than were Ca 2+ and Cd 2+, and the nature of the covalent bond character was independent of pH.

Evangelou, V. P.; Marsi, M.; Chappell, M. A.

2002-08-01

188

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

SciTech Connect

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.

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

1994-12-01

189

The Cation-? Interaction  

PubMed Central

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

DOUGHERTY, DENNIS A.

2014-01-01

190

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

USGS Publications Warehouse

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

Wasson, B.E.

1980-01-01

191

Potentiometric response from ion-selective nanospheres with voltage-sensitive dyes.  

PubMed

Potentiometric sensors require the implementation of conducting wires for signal transduction, but this is impractical for the readout of individual nanoparticles. It is here demonstrated for the first time that the potentiometric response of ion-selective nanospheres can be observed with voltage-sensitive dyes, thereby converting nanoscale electrochemical signals into an optical readout. No reference electrode is needed since the readout is by fluorescence. The results strongly support the potentiometric origin for the fluorescence response. The ion-selective nanospheres exhibit excellent selectivity and respond to ion concentration changes independent of sample pH, providing a new platform of potentiometric nanosensors with optical readout compatible with optical imaging equipment. PMID:25387118

Xie, Xiaojiang; Zhai, Jingying; Bakker, Eric

2014-11-26

192

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

USGS Publications Warehouse

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

Wasson, B.E.

1980-01-01

193

Potentiometric stripping determination of heavy metals using a graphite-reinforcement carbon vibrating electrode  

Microsoft Academic Search

Potentiometric stripping determination of Cd, Cu and Zn using a vibrating electrode (VE) is presented. A simple VE was constructed\\u000a by using a piezoelectric bimorph oscillator and an inexpensive graphite-reinforcement carbon (GRC) rod (a mechanical pencil).\\u000a Experimental results obtained with the simple VE follow the equation valid for quantitative application of potentiometric\\u000a stripping analysis (PSA) in large solutions. It was

Teiji Kakizaki; Kiyoshi Hasebe

1998-01-01

194

Potentiometric response and mechanism of anionic recognition of heterocalixarene-based ion selective electrodes  

Microsoft Academic Search

The ion selective electrode (ISE)-based potentiometric approach is shown to be an effective means of characterizing the anion recognition sites in the molecular receptor calix[2]pyridino[2]pyrrole (CPP). In particular, potentiometric pH-measurements involving the use of experimental PVC-membranes based on CPP revealed the existence of both mono- and diprotonated forms of the receptor under readily accessible conditions. Based on these analyses, apparent

T. V. Shishkanova; D. Sýkora; J. L. Sessler; V. Král

2007-01-01

195

Determination of the drug content of pharmaceuticals containing phenothiazine compounds by triangle programmed flow titration  

Microsoft Academic Search

A flow-through triangle programmed coulometric titration technique is worked out for the determination of phenothiazine compounds. The oxidation reaction of phenothiazines with hypobromite ion served as titration reaction. A biamperometric detector cell has been used for following the titration process. The titration technique has been used for the determination of the drug content (average and individual) of chlorpromazine, promethazine, diethazine

Zsófia Fehér; Ilona Kolbe; Ern? Pungor

1988-01-01

196

Complexometric determination of metal ions by microscopic diffusional titration.  

PubMed

Acid/base titrations of pico- and femtoliter microsamples have been performed previously using a diffusional microburet (DMB) for reagent delivery in a simple droplet-heptane system (Gratzl, M.; Yi, C. Anal. Chem. 1993, 65, 2085-2088). The lowest delivery rate achieved with a DMB was about 6 fmol/s, which would correspond to about a 1 microL/year volumetric flow rate with a hypothetical equivalent mechanical delivery scheme (Yi, C.; Gratzl, M. Anal. Chem. 1994, 66, 1976-1982). In this work, the feasibility of complexometric titrations in microscopic samples is explored. Stability of pH in the microdroplets required for different determinations and the effects of DMB shank geometry on titration characteristics are also studied. Diffusional microtitrations of Fe(III), Zn(II), and Cu(II) have been performed with EDTA. Xylenol orange and Eriochrome Black T provide clear color changes at the end point of the respective titrations, despite the microscopic size of the samples (between 16 and 1570 pL, corresponding to diameters between 30 and 144 microns). Random errors of the determinations relative to full scale were 6.6% for Fe(III), 5.8% for Cu(II), and 7.9% for Zn(II). The pH required for EDTA titrations of the individual metal ions stays stable in the acidic range. This makes the microscopic titration of a number of metal ions, such as Fe(III), Fe(II), Cu(II), and Pb(II), feasible in a simple droplet-heptane system without any modification. With a higher density of strongly alkaline buffer droplets (about 100 droplets/mm2) sprayed on the bottom of the Petri dish, or by flushing N2 above the heptane, the microscopic samples can also be kept alkaline despite ambient CO2 present. In this way, Zn(II) can also be titrated in microdroplets, requiring a pH around 10. This work renders it possible to perform a variety of complexometric titrations and other chemical manipulations in microdroplets even if they need to be kept alkaline. Similar titrations in single biological cells to assess intracellular buffer capacities of different metal ions, such as Ca(II) and Mg(II), are underway. PMID:8815747

Yi, C; Huang, D; Gratzl, M

1996-05-01

197

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

PubMed

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

Vanamo, Ulriika; Bobacka, Johan

2014-11-01

198

Potentiometric-level monitoring program - Mississippi and Louisiana: annual status report for fiscal year 1983  

SciTech Connect

Potentiometric-level data presented in this report were collected from October 1982 to September 1983 at 62 wells in Mississippi and Louisiana near Richton and Vacherie Domes, respectively. Six wells were added to the monitoring program during this period, and one previously measured well was damaged and has been deleted from the monitoring program. Analysis of the data indicates that most of the potentiometric-level changes recorded during fiscal year 1983 were small (less than 2 feet) and attributable to seasonal fluctuations. Of the 62 wells monitored, 18 exhibited potentiometric-level changes in excess of 2 feet. In Mississippi, the data generally indicate that a long-term, potentiometric-level increase is occurring in the Sparta, Kosciusko, Hattiesburg, Wilcox, and Citronelle Formations. Only seasonal fluctuations in potentiometric levels were observed in the caprock, and in the Catahoula and Cockfield Formations. In Louisiana, a long-term, potentiometric-level decline was observed for the Lower Austin Formation while an increase was observed for the Sparta and Upper Austin Formations. Seasonal fluctuations were observed in the Wilcox, Carrizo, and Nacatoch Formations. This work is a continuation of that described in ONWI-478 for fiscal year 1982. 24 references, 2 figures, 3 tables.

Not Available

1984-03-01

199

A novel ion chromatographic method based on cation-exchange and acid-base interactions for the simultaneous determination of total alkalinity and monovalent cations in samples of microliter volume.  

PubMed

An ion chromatographic (IC) method based on the use of titrant (strong acid) as the stationary phase was developed for simultaneous determination of total alkalinity (TA) and monovalent cations. The titrant used in this study was obtained by initially loading lithium dodecylsulfate (Li-DS) onto a reversed-phase material and then conditioning the column with a slightly acidified aqueous LiCl solution (a mixture of 50.0 mM LiCl and 0.1 mM H2SO4). When a small amount of a basic sample was injected onto a column prepared in this way, the basic species (Bn-) reacted predominantly with H+ on the stationary phase and the reaction with the eluent phase was negligible due to the very low concentration of eluent H+ (in the eluent, a molar ratio of [Li+]/[H+] = 250:1 applied). The stationary phase H+ consumed in the acid-base reaction was then re-supplied by H+ from the eluent. By monitoring the conductance of the eluent using conductivity, an induced peak resulting from the basic species was observed. Calibration graphs of peak areas vs. molar concentration of the basic species for OH-, HCO3- and H2PO4- were found to be identical. CO3(2-), HPO4(2-), and B4O7(2-) also gave identical calibration curves but their slope values were twice those for HCO3-. The detection limit for HCO3- was less than 3.2 microM and the calibration curve was linear up to 12.3 mM (injection volume, 100 microL). Seawater was directly analyzed and its total alkalinity was found to be 2.87 mM (RSD 0.53%, n = 5), which was in good agreement with the result of 2.88 mM (RSD 3.2%, n = 5) obtained using auto-potentiometric titration. Na+ and K+ were determined simultaneously and the concentrations were 481.6 and 10.6 mM, respectively. PMID:11394291

Hu, W; Haddad, P R; Hasebe, K; Tanaka, K

2001-05-01

200

Coulometric titration of D(+)-glucose using its enzymatic oxidation.  

PubMed

A definitive method is described for the indirect assay of milligram quantities of D(+)-glucose by coulometric titration. D(+)-Glucose was aerobically oxidized by glucose oxidase in an acetate buffer solution (pH 5.1). Subsequently, the enzymatically formed hydrogen peroxide was titrated coulometrically with electrogenerated hypobromite in sodium bromide-sodium tetraborate medium of pH 8.6, with biamperometric end-point detection. Parameters affecting the enzymatically catalyzed oxidation and coulometric titration were evaluated. The optimized conditions for the oxidation of up to 20 mg of D(+)-glucose include the addition of 4500 U of glucose oxidase and stirring over a 10-min interval at 25 degrees C. Under proposed conditions, the assay values of several commercial D(+)-glucose reagents were somewhat lower than the guaranteed minimum values, with RSDs (n = 5) of 0.071 - 0.106%. PMID:11990540

Tanaka, T; Shutto, E; Mizoguchi, T; Fukushima, K

2001-02-01

201

Determination of uranium by direct titration with dipicolinic acid  

SciTech Connect

Direct titration of uranium with dipicolinic acid, in the presence of Arsenazo I, is a simple, precise, and accurate method for uranium determination. The method is particularly attractive because it can be totally automated. Detecting the end point (color change from blue to pink) depends on the concentration range. For the Micro Method (1 to 20 ppM U in the solution titrated), the gradual color change is monitored spectrophotometrically. For the Macro Method (20 to 300 ppM), the end point is determined either visually or spectrophotometrically. The spectrophotometric end point is computed by fitting the titration curve. The relative standard deviation is +-1 to 3% for the Micro Method and +-0.3% for the Macro Method.

Baumann, E.W.

1984-07-12

202

Potentiometric quasi-array employing calixarene derivatives for the high-throughput similarity/diversity screening of beta-adrenergic and beta-blocking chiral drugs by HPLC.  

PubMed

Performance of potentiometric quasi-array detection system consisted with the seven poly (vinyl chloride) (PVC) based liquid membrane electrodes in the cation-exchange HPLC using acetonitrile--40 mM phosphoric acid (15 : 85, v/v, pH* 2.35) for assessing of molecular similarity/diversity in a mini-library of beta-adrenergic and beta-blocking chiral drugs was presented. Macrocyclic compounds differing in stability of their conformers as well as in a size, steric hindrance and polarity of its internal cavities, comprising a series of five calix[6]arene derivatives completed with one modified calix[4]resorcinarene, were used as neutral ionophores to compose mentioned set of PVC-based electrodes. The output potentiometric responses were registered in the linear supernerstian range of calibration graph of each electrode, i.e. for a constant injected concentration 2.0 x 10(-4) M of investigated drugs, which is related to the amount frequently used at in vitro studies on pharmacological effects of these drugs. The impact of symmetry oriented supramolecular interactions on the responses of developed electrodes were characterised with proposed series of the highly significant quantitative structure-potentiometric response relationships (QSPRRs) combining both three-dimensional (3D) molecular descriptors of analysed drugs as well as lipophilicity and volume polarizability of calixarene-type ionophores. The principal components analysis (PCA) and unweighted hierarchical clustering analysis (HCA) were used as the pattern recognition techniques into collected potentiometric database for extraction of the useful information on the molecular and pharmacological similarity/diversity of analysed drugs, thus a high-throughput and consistent identification of therapeutically relevant agonists of beta2- and beta3-adrenoceptors and antagonists of beta1-adrenoceptor was especially achieved. This evidence supports also a hypothesis formulated by results of homology modelling on the subtle significance of an unrecognised supramolecular insertion processes of the chiral drug molecule into the flexible hydrophobic pocket(s) formed by seven helical transmembrane moving domains of beta-adrenoceptors on their final activation, sequestration, down-regulation or blockade. PMID:15200382

Bazylak, Grzegorz; Nagels, Luc J; Geise, Herman J

2004-06-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

204

Determination of the Glass Electrode Parameters by Means of Potentiometric Titration of Acetic Acid in Aqueous Sodium or Potassium Chloride Solutions at 25°C  

Microsoft Academic Search

Single-ion activity coefficient equations are presented for the calculation of stoichiometric (molality scale) dissociation constants Km for acetic acid in aqueous NaCl or KCl solutions at 25°C. These equations are of the Pitzer or Hückel type and apply to the case where the inert electrolyte alone determines the ionic strength of the acetic acid solution considered. Km for a certain

Jaakko I. Partanen; Pekka M. Juusola; Pentti O. Minkkinen

1999-01-01

205

Bio-precipitation of uranium by two bacterial isolates recovered from extreme environments as estimated by potentiometric titration, TEM and X-ray absorption spectroscopic analyses.  

PubMed

This work describes the mechanisms of uranium biomineralization at acidic conditions by Bacillus sphaericus JG-7B and Sphingomonas sp. S15-S1 both recovered from extreme environments. The U-bacterial interaction experiments were performed at low pH values (2.0-4.5) where the uranium aqueous speciation is dominated by highly mobile uranyl ions. X-ray absorption spectroscopy (XAS) showed that the cells of the studied strains precipitated uranium at pH 3.0 and 4.5 as a uranium phosphate mineral phase belonging to the meta-autunite group. Transmission electron microscopic (TEM) analyses showed strain-specific localization of the uranium precipitates. In the case of B. sphaericus JG-7B, the U(VI) precipitate was bound to the cell wall. Whereas for Sphingomonas sp. S15-S1, the U(VI) precipitates were observed both on the cell surface and intracellularly. The observed U(VI) biomineralization was associated with the activity of indigenous acid phosphatase detected at these pH values in the absence of an organic phosphate substrate. The biomineralization of uranium was not observed at pH 2.0, and U(VI) formed complexes with organophosphate ligands from the cells. This study increases the number of bacterial strains that have been demonstrated to precipitate uranium phosphates at acidic conditions via the activity of acid phosphatase. PMID:22019055

Merroun, Mohamed L; Nedelkova, Marta; Ojeda, Jesus J; Reitz, Thomas; Fernández, Margarita López; Arias, José M; Romero-González, María; Selenska-Pobell, Sonja

2011-12-15

206

The use of linear potentiometric titration curves in the determination of alkalinity and acid-base properties of diluted solutions of humic substances.  

PubMed

A critical study of the use of Gran and modified Gran functions for the determination of alkalinity and acid-base properties of diluted solutions containing humic substances is presented. These solutions were composed of 340 muM HCO3(-)(3) in 0, 10, 20.5 and 41 mg/1. of sodium humate in order to simulate natural waters with different levels of dissolved organic carbon. The results showed that the alkalinity may be determined in good agreement with the expected value using both methodologies. The modified Gran functions give information about acid-base speciation in addition to the alkalinity. The application of the modified Gran functions for determination of humic acid pK(a)s and stoichiometry was studied under conditions simulating waters rich in natural organic matter in terms of humic acid concentrations. PMID:18966083

Masini, J C

1994-08-01

207

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

PubMed Central

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

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

2008-01-01

208

Potentiometric and Relaxometric Properties of a Gadolinium-based MRI Contrast Agent for Sensing Tissue pH  

PubMed Central

The pH sensitive contrast agent, GdDOTA-4AmP (Gd1) has been successfully used to map tissue pH by MRI. Further studies now demonstrate that two distinct chemical forms of the complex can be prepared depending upon the pH at which Gd3+ is mixed with ligand 1. The desired pH sensitive form of this complex, referred to here as a Type II complex, is obtained as the exclusive product only when the complexation reaction is performed above pH 8. At lower pH values, a second complex is formed that, by analogy with an intermediate formed during preparation of GdDOTA, we tentatively assign this to a Type I complex where the Gd3+ is coordinated only by the appended side-chain arms of 1. The proportion of Type I complex formed is largely determined by the pH of the complexation reaction. The magnitude of pH dependent change in relaxivity of Gd1 was found to be less than earlier reported (S. Zhang, K. Wu, and A. D. Sherry, Angew. Chem., Int. Ed., 1999, 38, 3192), likely due to contamination of the earlier sample by an unknown amount of Type I complex. Examination of the NMRD and relaxivity temperature profiles, coupled with information from potentiometric titrations, shows that the amphoteric character of the phosphonate side-chains enables rapid prototropic exchange between the single bound water of the complex with those of the bulk water thereby giving Gd1 a unique pH dependent relaxivity that is quite useful for pH mapping of tissues by MRI. PMID:17539632

Kalman, Ferenc K.; Woods, Mark; Caravan, Peter; Jurek, Paul; Spiller, Marga; Tircso, Gyula; Kiraly, Robert; Brucher, Erno; Sherry, A. Dean

2008-01-01

209

Potentiometric polymeric membrane electrodes for mercury detection using calixarene ionophores.  

PubMed

It is here established that potentiometric polymeric membrane electrodes based on electrically neutral ionophores are a useful analytical tool for the detection of heavy metal ions from environmental and industrial waste water. PVC based membrane containing p-tert-butyl-calix[4]arenethioether derivative as active material along with sodiumtetraphenylborate (NaTPB) as solvent mediator and dibutylphthalate as a plasticizer in the ratio 45:9:460:310 (w/w%) (I:NaTPB:DBP:PVC) exhibits good properties with a Nernstian response of 29.50+/-1.0 mV per decade of activity and a working concentration range of 7.2 x 10(-8)-1.0 x 10(-1) M. The electrode gave more stable potential readings when used around pH 2.5-6.8 and exhibits fast response time of 14 s. The sensors were found to work satisfactorily in partially non-aqueous media up to 40% (v/v) content of acetone, methanol or ethanol and could be used over a period of 7-9 months. Excellent selectivity for Hg(2+) ions is indicated by match potential method and fixed interference method. The sensors could be used successfully in the estimation of mercury in different sample. PMID:20150706

Tyagi, Sonika; Agarwal, Himanshu; Ikram, Saiqa

2010-01-01

210

Potentiometric detection and removal of copper using porphyrins  

PubMed Central

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

2013-01-01

211

Coulometric Titration of Free Cyanide with Electrogenerated Hypobromite  

Microsoft Academic Search

A rapid and sensitive method is described for the direct determination of cyanide by coulometric titration with electrogenerated hypobromite. A biamperometric end point was utilized. From 0.498 – 9.980 ueq of cyanide were analyzed with an average error of 0.36% and an average standard deviation of 0.045.

R. A. Gibbs; R. J. Palma Sr

1974-01-01

212

A modified function of the formula of double iodometric titration  

Microsoft Academic Search

Double iodometric titration is the most useful method to determine oxygen content of high Tc superconductors. Its traditional calculating formula is not accurate enough, and a new calculating formula has just been put forward. To understand which relationship of the traditional formula depends on the new one is an important problem. On studying the new formula, we find a modified

Wu Ming Chen; J. Chen; X. Jin

1997-01-01

213

SUBVISIBLE RETINAL LASER THERAPY Titration Algorithm and Tissue Response  

E-print Network

SUBVISIBLE RETINAL LASER THERAPY Titration Algorithm and Tissue Response DANIEL LAVINSKY, MD, PHD,* DANIEL PALANKER, PHD* Purpose: Laser therapy for diabetic macular edema and other retinal diseases has of tissue effect. The algorithm adjusts both power and pulse duration to vary the expected level of thermal

Palanker, Daniel

214

Selective titrations of metal ions in the micromolar range  

Microsoft Academic Search

Summary An outline is given of the factors governing the complexometric titration of metal ions at low concentration. Apart from the limit of determination, special attention has been given to the selectivity of the determinations. The influence of the chemical reaction and of the method of indication has been discussed.

G. den Boef

1978-01-01

215

Direct complexometric titration of thorium with versene using SPADNS  

Microsoft Academic Search

The existing volumetric methods for the determination of thorium are indirect and unsatisfactory. A direct titrimetric method for the estimation of thorium has been developed which involves the adjustment ofph, addition of 1 ml. of 0.02% SPADNS indicator, dilution to volume and titration with versene. It is based on the fact that thorium forms a coloured complex with SPADNS and

Gurupada Banerjee

1955-01-01

216

Successive determination of praseodymium and ytterbium by coulometric complexometric titration  

SciTech Connect

A method is described for the successive coulometric complexometric titration of microgram levels of light and heavy rare earth elements. The total amount of light and heavy rare earth elements is titrated by electrogenerating titrant EDTA on the mercury pool as a cathode. Then, the mercury pool is switched as an anode, electrogenerating Hg/sup 2 +/, and is used to titrate EDTA which is displaced from its light rare earth elements complex by malic acid that has been added prior to the electrogenerating Hg/sup 2 +/. The heavy rare earth elements can be determined from the total rare earth elements minus the result of displacement titration of EDTA which is equivalent to the light rare earth elements. A 10-30 ..mu..g sample of light and heavy rare earth elements (Pr and Yb, La and Lu, Nd and Tm) can be determined successively. Errors and standard deviation are not more than 2.5% and 0.20, respectively. 2 tables, 5 figures.

Chun-Nian, S.; Jing-Ci, L.; Qi-Dao, N.; Mou-Sen, C.

1982-06-01

217

Automatic Titrators in the Analytical and Physical Chemistry Laboratories  

Microsoft Academic Search

In 1995 the University of Florida received an NSF-ILI grant to purchase six automatic titrators, which have now been successfully integrated into the analytical and physical chemistry teaching laboratories. After they have mastered fundamental techniques, students in the introductory analytical laboratory gain experience with automated analyses in three experiments: the iodimetric analysis of ascorbic acid, the determination of polymer molecular

Kathryn R. Williams

1998-01-01

218

RESEARCH Open Access Continuous positive airway pressure titration in  

E-print Network

RESEARCH Open Access Continuous positive airway pressure titration in infants with severe upper airway obstruction or bronchopulmonary dysplasia Sonia Khirani1,2 , Adriana Ramirez2,3 , Sabrina Aloui2 airway obstruction (UAO) or bronchopulmonary dysplasia (BPD). Methods: The breathing pattern

Paris-Sud XI, Université de

219

Back titration with mercuric nitrate in alkaline medium  

Microsoft Academic Search

A rapid, reliable and accurate method for the determination of trivalent chromium, based on back titrating excess EDTA solutions in the presence of chromium versenate, with mercuric nitrate in alkaline media is given. By its aid amounts of chromium in the order of 50 micro- to 15 milligrams can be determined with fair accuracy. The method is applied for analysis

H. Khalifa; M. M. Khater

1960-01-01

220

Combining Spectroscopic and Potentiometric Approach to Characterize Competitive Binding to  

E-print Network

. The knowledge of radionuclides transport in the geosphere is a key issue for the assessment of the safety+ , inorganic species, major cations, e.g., Ca(II) or Mg(II), could influence these metals transport experiments using Ca2+ or Cu2+ ion selective electrodes were used to model time-resolved laser fluorescence

Paris-Sud XI, Université de

221

Investigation of the absorption principle involved in the analyses and titrations performed in high frequency fields  

E-print Network

s e e e e ~ e e 58 Xi Contour Data for Lho Titration of ~roohlorio and Ditrie keide with 804%un F jll'oxide, ~ ~ ~ o i i ~ ~ ~ i 15 XI, Titration of Spdroohlorio kaid with Sodium Dpiroxido ~ i ~ 15 III ~ Titration of Sitrio koid with Sodiun... Epdronide e ~ e ~ i i XV XVi Titration of a Mixture of Hydroohiorie and Sitrio koide ~ e 18 VN Contour Data for the Titration of Sulphurie an4 keotie koide with 804iun Bgdronide ~ i e e ~ s + s e ~ s s ~ Sl VX+ Titration of Sulphnrie kaid with Sodiun...

Griffin, James Hilton

2012-06-07

222

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

PubMed Central

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

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

2008-01-01

223

Speci cation Broadcasting  

E-print Network

Node b snd Msg to neighbor d Node c snd Msg to neighbor d 1 2 1 3 Node a snd Msg to neighbors b and c Node d snd Msg to neighbor c 3 #12; Limitations of Pseudocode Speci#12;cation #15; not executable #15 10 #12; RBP { speci#12;cation Number Oid Oid Oid ­> Msg . msg msg_To_From_Src_ : ... SQ i j

Talcott, Carolyn L.

224

Real-time potentiometric detection of bacteria in complex samples.  

PubMed

Detecting and identifying pathogen bacteria is essential to ensure quality at all stages of the food chain and to diagnose and control microbial infections. Traditional detection methods, including those based on cell culturing, are tedious and time-consuming, and their further application in real samples generally implies more complex pretreatment steps. Even though state-of-the-art techniques for detecting microorganisms enable the quantification of very low concentrations of bacteria, to date it has been difficult to obtain successful results in real samples in a simple, reliable, and rapid manner. In this Article, we demonstrate that the label-free detection and identification of living bacteria in real samples can be carried out in a couple of minutes and in a direct, simple, and selective way at concentration levels as low as 6 colony forming units/mL (CFU) in complex matrices such as milk or 26 CFU/mL in apple juice where the pretreatment step of samples is extremely easy. We chose Escherichia coli ( E. coli ) CECT 675 cells as a model organism as a nonpathogenic surrogate for pathogenic E. coli O157:H7 to test the effectiveness of a potentiometric aptamer-based biosensor. This biosensor uses single-walled carbon nanotubes (SWCNT) as excellent ion-to-electron transducers and covalently immobilized aptamers as biorecognition elements. The selective aptamer-target interaction significantly changes the electrical potential, thus allowing for both interspecies and interstrain selectivity and enabling the direct detection of the target. This technique is therefore a powerful tool for the immediate identification and detection of microorganisms. We demonstrate the highly selective detection of living bacteria with an immediate linear response of up to 10(4) CFU/mL. The biosensor can be easily built and used, is regenerated without difficulty, and can be used at least five times with no loss in the minimum amount of detected bacteria. PMID:20961052

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

2010-11-15

225

Effect of the symmetry of the calix[4]pyrrole cavity on sensitivity and selectivity of potentiometric sensors for neutral nitrophenols  

Microsoft Academic Search

Lipophilic macrocyclic and acyclic derivatives of pyrrole were applied as sensory elements of liquid membrane potentiometric sensors destined for the recognition of neutral forms of nitrophenol isomers. All compounds displayed high ability for the uptake of protons. The potential of liquid membranes, containing pyrrole derivatives, strongly depended on the pH of the aqueous phase. Their potentiometric responses generated in the

Tomasz Piotrowski; Hanna Radecka; Jerzy Radecki; Stefaan Depraetere; Wim Dehaen

2001-01-01

226

Indirect trace determination of ethylenediaminetetraacetic acid (EDTA) in water by potentiometric stripping analysis  

SciTech Connect

An analytical method for indirect trace determination of ethylenediaminetetraacetic acid (EDTA) in water, by potentiometric stripping analysis is described. Excess Bi(III) was added to form a 1:1 complex with EDTA at pH 2.3. The uncomplexed Bi(III) was then deposited on a glassy carbon electrode at a potential of -0.40 V vs. SCE and subsequently stripped potentiometrically using potassium dichromate as oxidant. The stripping time of uncomplexed Bi(III) was recorded. The concentration of EDTA in the sample was determined from the concentration of added Bi(III) and the potentiometrically stripped Bi(III) at -0.4 V by the standard addition method. The relative standard deviation for EDTA concentration of 96 ppb and 4.5 ppb was 1.9% and 2.6%, respectively. The detection limit was about 1 ppb EDTA for a deposition time of 3 minutes.

Fayyad, M.; Tutunji, M.; Taha, Z.

1988-08-01

227

Preparation of nano-structured Pt-YSZ composite and its application in oxygen potentiometric sensor  

NASA Astrophysics Data System (ADS)

Nano-structured Platinum-Yttria Stabilized Zirconia (YSZ) composites for oxygen potentiometric sensors were directly prepared with carbon black and the precursors such as chloroplatinic acid, zirconyl nitrate and yttrium nitrate. The as-prepared Pt-YSZ composite consisted of cubic crystalline YSZ and Pt particles, and the particle sizes of Pt catalyst and YSZ electrolyte were about 25-35 and 5-10 nm, respectively. The Pt-YSZ composite electrodes exhibited excellent electrochemical performances when evaluated by EIS measurements. The introduction of the nano-structured Pt-YSZ composite into the oxygen potentiometric sensor can reduce sensor's operating temperature to be about 380 °C, and also can reduce sensor's response time to be about 5 s at 400 °C. The oxygen potentiometric sensors incorporating nano-structured Pt-YSZ composites exhibited longer lifetime than those employing pure Pt as the sensing electrodes.

ChaoYang, Xia; XuChen, Lu; Yan, Yan; TiZhuang, Wang; ZhiMin, Zhang; SuPing, Yang

2011-07-01

228

Generalized potentiometric-surface map of the High Plains aquifer in Wyoming, 1981  

USGS Publications Warehouse

A potentiometric-surface map shows the general configuration of the water surface for the High Plains Aquifer, which is composed of Oligocene age and younger rocks in southeastern Wyoming. The potentiometric contours are shown at 100-foot intervals on a map at a scale of 1:250,000. The High Plains Aquifer in Wyoming underlies an area of 8,190 square miles and geologically consists of the White River Formation of Oligocene age, the Arikaree Formation of early Miocene age, the Ogallala Formation of late Miocene age, and alluvial deposits of Quaternary age. The altitude of the potentiometric surface declines from about 7 ,100 feet in southwestern Laramie County to about 4,100 feet in eastern Goshen County. Typically, the slope is between 20 and 30 feet per mile; the general direction of flow is eastward. (USGS)

Avery, Charles; Pettijohn, Robert A.

1984-01-01

229

Understanding the response behavior of potentiometric gas sensors for non-equilibrium gas mixtures  

SciTech Connect

Many applications of gas sensors require concentration measurements of reactive gases in mixtures that are out of thermodynamic equilibrium. These applications include: hydrogen and hydrocarbon fuel gas sensors operating in ambient air for explosion hazard detection, carbon monoxide detection in ambient air for health protection, combustion efficiency sensors for stoichiometry control, and nitric oxide sensors for air pollution monitoring. Many potentiometric and amperometric electrochemical sensor technologies have been developed for these applications. A class of the potentiometric sensors developed for gas mixtures are the non-Nerstian sensors. This presentation defines a categorization and theoretical analysis of three distinct electrochemical processes that can produce a non-Nernstian sensor response.

Garzon, F. H. (Fernando H.); Mukundan, R. (Rangachary); Brosha, E. L. (Eric L.)

2002-01-01

230

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

USGS Publications Warehouse

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

Westerfield, Paul W.

1995-01-01

231

APPLICATION OF CHEMICAL MODIFIED ELECTRODE IN COULOMETRIC TITRATION FOR DETERMINATION OF SOLANESOL  

Microsoft Academic Search

The problem of large deviation of determination of solanesol by coulometric titration when using direct titration technique and double Pt electrodes amperometric method indicating the end-point has been resolved. In titration process, solanesol, an electroinactive species, can be adsorbed on the surfaces of Pt electrodes and inhibit electrode reactions of Br and Br2. Therefore, when titration reaches the end-point, the

Ge Zhao; Jianying Qu; Meng Liu; Kuaizhi Liu; Zuliang Du

2002-01-01

232

A high frequency titration of indium with benzenephosphinic acid  

E-print Network

. %~ Jensen for his eid on this work, Tba Sargent-Jensen High Frequency Titrator was used to determine the amount of indium present in a chloride solution. The addition of benzenephosphinic acid, which precipitated the indium as indium benzenephosphinate..., caused certain loading variations on the oscillator. Complexes of indium in chloride solution were responsible for producing three stoichiometric breaks in the loading curve. Calculations based on the average of these breaks measured at least 98. 65...

Keilt, Francis Xavier

2012-06-07

233

Quantitative estimation of benzylisoquinoline derivatives by coulometric titration  

Microsoft Academic Search

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.

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

2008-01-01

234

Iodometric titration of copper-oxide superconductors and Tokura's Rule  

Microsoft Academic Search

Iodometric titration measurements, which are often interpreted as obtaining the excess valence on Cu atoms in Y(LayBa1-y)2Cu3Ox, are reinterpreted as determining concentrations of 'neutral' or hypocharged oxygen instead. Tokura's Rule, an empirical relationship between the critical oxygen content xc and the critical La content yc at the onset of superconductivity, is derived on the basis of a hypocharged-oxygen model.

H. A. Blackstead; D. B. Pulling; J. D. Dow

1996-01-01

235

Iodometric titration of copper-oxide superconductors and Tokura's Rule  

NASA Astrophysics Data System (ADS)

Iodometric titration measurements, which are often interpreted as obtaining the excess valence on Cu atoms in Y(La yBa 1- y) 2Cu 3O x, are reinterpreted as determining concentrations of “neutral” or hypocharged oxygen instead. Tokura's Rule, an empirical relationship between the critical oxygen content xc and the critical La content yc at the onset of superconductivity, is derived on the basis of a hypocharged-oxygen model.

Blackstead, Howard A.; Dow, John D.; Pulling, David B.

1996-02-01

236

Iodometric titration of copper-oxide superconductors and Tokura's rule  

Microsoft Academic Search

Iodometric titration measurements, which are often interpreted as obtaining the excess valence on Cu atoms in Y(LayBa1?y)2Cu3Ox, are reinterpreted as determining concentrations of “neutral” or hypocharged oxygen instead. Tokura's Rule, an empirical relationship between the critical oxygen content xc and the critical La content yc at the onset of superconductivity, is derived on the basis of a hypocharged-oxygen model.

Howard A. Blackstead; John D. Dow; David B. Pulling

1996-01-01

237

Hydroperoxide titration by DSC in thermally oxidized polypropylene  

Microsoft Academic Search

Unstabilized polypropylene (PP) films and stabilized PP fibres were thermally oxidized at 80°C under high oxygen pressure (5.0MPa). Their oxidation was monitored by infrared (IR) spectroscopy, iodometric titration and modulated differential scanning calorimetry (MDSC). This latter technique allows separation of the thermograms into two parts: a reversing signal containing the major part of the melting endotherm and a non-reversing exothermal

E. Richaud; F. Farcas; B. Fayolle; L. Audouin; J. Verdu

2006-01-01

238

Determination of fluorine in glass crystallite using complexometric back titration  

Microsoft Academic Search

color change at the eqivalence point. To determine 0.4-2.0 mg of fluorine in organic compounds it was proposed in [3] to use complexometric titration using methylthymol blue indicator, of the excess of a lanthanum salt used to precipitate the fluorine ions. However, Murase et al. [4] felt that this method was not very suitable for determining 0.4-100 mg of fluorine

T. I. Danilevich; V. V. Abramov

1988-01-01

239

Carboxylic Acid Unknowns and Titration 90 CARBOXYLIC ACID UNKNOWN  

E-print Network

Carboxylic Acid Unknowns and Titration 90 CARBOXYLIC ACID UNKNOWN A. Solubility Tests: Water, NaHCO3, and NaOH Test the solubility of your acid first in neutral water, in NaOH/H2O, and in NaHCO3 to 30 drops. Swirl/mix well. Use of small stir bar helps. · Water Test: Only acids with small numbers

Jasperse, Craig P.

240

?- d-Glucosidase reaction kinetics from isothermal titration microcalorimetry  

Microsoft Academic Search

The cellobiase activities of nine thermal stable mutants of Thermobifida fusca BglC were assayed by isothermal titration microcalorimetry (ITC). The mutations were previously generated using random mutagenesis and identified by high-temperature screening as imparting improved thermal stability to the ?-d-glucosidase enzyme. Analysis of the substrate–saturation curves obtained by ITC for the wild-type enzyme and the nine thermally stabilized mutants revealed

Tina Jeoh; John O. Baker; Mursheda K. Ali; Michael E. Himmel; William S. Adney

2005-01-01

241

Back titration with mercuric nitrate in alkaline medium  

Microsoft Academic Search

The back titration procedure making use of mercuric nitrate as back titrant for excess EDTA in alkaline media, has been successfully applied for the determination of small amounts of scandium or palladium in the order of 0.045 to 7 or 0.1 to 4mg, respectively. Simple procedures are given for the analysis of binary or ternary mixtures of scandium or palladium

H. Khalifa; M. M. Khater

1962-01-01

242

Suspension culture titration: A simple method for measuring baculovirus titers.  

PubMed

The baculovirus-insect cell expression system is an important technology for the production of recombinant proteins and baculovirus-based biopesticides. Budded virus titration is critical when scaling up baculovirus production processes in suspension cultures, to ensure reproducible infections, especially when a low multiplicity of infection (MOI) is applied. In this study, a simple suspension culture titration (SCT) assay was developed that involves accurate measurements of the initial cell densities (ICDs) and peak cell densities (PCDs) of an infected culture, from which the MOI and hence the virus inoculum infectious titer can be estimated, using the established Power-Nielsen baculovirus infection model. The SCT assay was assessed in parallel with two adherent culture-based assays (MTT and AlamarBlue) for the Heliothine baculovirus HaSNPV, and was shown to be more objective, time-efficient and reproducible. The model predicted a linear correlation between log(PCD/ICD) and log(MOI), hence an alternative model-independent SCT assay was also developed, which relies on a well-replicated standard curve relating suspension culture-derived PCD/ICD ratios with plaque or endpoint assay-derived MOIs. Standard curves with excellent linearity were generated for HaSNPV and the industrially significant rAcMNPV, demonstrating the feasibility of this simple titration approach, especially in terms of its applicability to a wide range of virus infection kinetics. PMID:22561639

Matindoost, Leila; Chan, Leslie C L; Qi, Ying Mei; Nielsen, Lars K; Reid, Steven

2012-08-01

243

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

ERIC Educational Resources Information Center

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…

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

2012-01-01

244

COMPLEXOMETRIC DETERMINATION OF NICEL AND IRON IN THE SAME TEST BY PHOTOCOLORIMETRIC TITRATION  

Microsoft Academic Search

A complexometric titration method for iron and nickel is described. The ; iron is masked with pyrophosphate, and the nickel is titrated directly with ; (ethylenediamine)tetraacetic acid (EDTA) in the presence of murexide up to the ; violot color change. The IF 620 filter is used. The iron is titrated indirectly. ; An excess of EDTA is added, which destroys

1958-01-01

245

A potentiometric investigation of complex formation between some metal ions and biologically active quinazoline-4-3(H)-one Schiff's base  

NASA Astrophysics Data System (ADS)

The proton dissociation constant of the ligand and the stability of the complexes of Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Cu(II), Ba(II), Mg(II), Mn(II), Th(IV), and UO2(II) ions with 2-phenyl-3-(2'-hydroxy-5'-benzylidine)-quinazoline-4-(3H)-one [PBQ] were determined potentiometrically at 30 ± 0.1°C and ionic strengths of 0.025, 0.05, 0.10, 0.15 and 0.20 M NaNO3 in a 60:40 (v/v) ethanol-water medium. The proton-ligand and metal-ligand stability constants of the complexes were determined pH metrically by the Calvin-Bjerrum titration technique. The order of stability constants obeys the Irving-Rossotti rule. The negative values of ? G° suggest that the reactions are spontaneous.

Shivakumar, K.; Shashidhar, S.; Halli, M. B.

2007-10-01

246

Application of a new potentiometric method for determination of phosphate based on a surfactant-modified zeolite carbon-paste electrode (SMZ-CPE).  

PubMed

A phosphate-selective electrode based on surfactant-modified zeolite (SMZ) particles into carbon-paste has been proposed (SMZ-CPE). The electrode was fully characterized in terms of composition, response time, ionic strength, thermal stability and usable pH range. The electrode containing 20% SMZ exhibited linear response range to phosphate species in the range of 1.58 x 10(-5) to 1.00 x 10(-2) M with a detection limit of 1.28 x 10(-5) M and a Nernstian slope of 29.9+/-0.9 mV per decade of phosphate concentration. The electrode response to phosphate remains constant in the pH range of 4-12 and in the presence of 1 x 10(-4) to 4 x 10(-3) M NaNO(3). The response of the electrode reaches equilibrium within several seconds after immersing the electrode in phosphate solution. Common anions such as Cl(-), Br(-), I(-), NO(3)(-), SO(4)(2-) and Cr(2)O(7)(2-) have little effect on the determination of phosphate but AsO(4)(3-) shows some interference. A successful application of the electrode for determination of phosphate in a fertilizer, using direct potentiometry, is presented. The electrode was also used for the potentiometric titration of phosphate. The validation of the obtained results in each case was proved by statistical methods. PMID:20082776

Ejhieh, Alireza Nezamzadeh; Masoudipour, Neda

2010-01-18

247

Depression May Reduce Adherence during CPAP Titration Trial  

PubMed Central

Study Objectives: Depression is a risk factor for medication non-compliance. We aimed to identify if depression is associated with poorer adherence during home-based autotitrating continuous positive airway pressure (autoPAP) titration. Design: Mixed retrospective-observational study. Setting: Academic center. Participants: Two-hundred forty continuous positive airway pressure-naïve obstructive sleep apnea (OSA) patients. Measurements: Patients underwent approximately 1 week of home-based autoPAP titration with adherence data downloaded from the device. Electronic hospital records were reviewed in a consecutive manner for inclusion. Three areas of potential predictors were examined: (i) demographics and clinical factors, (ii) disease severity, and (iii) device-related variables. Depression and anxiety were assessed using the Hospital Anxiety and Depression Scale (HADS). Scores on the subscales were categorized as normal or clinical diagnoses of depression (? 8) and anxiety (? 11). The primary outcome variable was the mean hours of autoPAP used per night. Results: Patients were diagnosed with OSA by either attended polysomnography (n = 73, AHI 25.5[15.1-41.5]) or unattended home oximetry (n = 167, ODI3 34.0[22.4-57.4]) and had home-based autoPAP titration over 6.2 ± 1.2 nights. Mean autoPAP use was 4.5 ± 2.4 hours per night. Multiple linear regression analysis revealed that depression and lower 95th percentile pressures significantly predicted lesser hours of autoPAP use (R2 = 0.19, p < 0.001). Significantly milder OSA in those requiring lower pressures may have confounded the relationship between 95th percentile pressure and autoPAP use. Conclusion: Depression was independently associated with poorer adherence during home-based autoPAP titration. Depression may be a potential target for clinicians and future research aimed at enhancing adherence to autoPAP therapy. Citation: Law M; Naughton M; Ho S; Roebuck T; Dabscheck E. Depression may reduce adherence during CPAP titration trial. J Clin Sleep Med 2014;10(2):163-169. PMID:24532999

Law, Mandy; Naughton, Matthew; Ho, Sally; Roebuck, Teanau; Dabscheck, Eli

2014-01-01

248

Stability of Ultradisperse Copper in a Sulfo Cation Exchanger Matrix  

NASA Astrophysics Data System (ADS)

The recrystallization of ultradisperse copper chemically deposited onto a sulfo cation exchanger matrix was studied by the potentiometric method. The stationary value of the electrode potential of the copper-sulfo cation exchanger composite was established during a long period of time, which depended on the ionic form of the composite (H+, Cu2+, or Na+), solution composition (CuSO4, H2SO4, and Na2SO4), and solution concentration. Recrystallization was favored by copper(II) counterions, which entered the composite as a result of ion exchange, nonexchange absorption of copper sulfate, or preliminary composite transformation into the Cu2+ form. In the quasi-equilibrium state, the concentration of copper(II) counterions was maintained at a high level by the Donnan interfacial potential. At all the copper(II) sulfate concentrations used, the potential of the Cu2+/Cu ion—metal pair in the ion-exchange matrix remained at virtually the same level, which was indicative of the stable state of copper particles. In the absence of an external source of copper ions, recrystallization was significantly hindered; therefore, the potential exhibited only a slight drift. Copper ions formed in the solution of small crystals were localized in the vicinity of ionogenic matrix centers, which decreased the mobility of these particles as counterions; therefore, the dispersity of particles remained unchanged.

Zolotukhina, E. V.; Polyanskii, L. N.; Peshkov, S. V.; Kravchenko, T. A.; Krysanov, V. A.

2008-03-01

249

Cation nonstoichiometry in (Bi, Pb) 2Sr 2Ca 2Cu 3O 10+?  

NASA Astrophysics Data System (ADS)

X-ray lattice parameter measurements of the (Bi, Pb) 2- xSr 2- yCa 2- zCu 3O 10+? system show that a continuously varying solid-solution cation nonstoichiometry exists within -0.1< x<0.1, 0< y<0.3, and 0< z<0.3. However, the system cannot incorporate any defect at its Cu site. The oxygen content determined by titration decreases linearly with increasing cation-vacancy concentration. The critical temperature, Tc, shows a maximum value at the stoichiometric cation composition and decreases to a lower constant value across the nonstoichiometric composition region with increasing alkaline-earth deficiency. Flux pinning in this system is increased by the cation-vacancy concentration only in the low-temperature range, while it decreased in the high-temperature range. The flux-pinning behavior is discussed in view of its two-dimensionality in the superconductivity for this system.

Nomura, Shunji; Yoshino, Hisashi; Ando, Ken

1994-04-01

250

Electrostatic interaction between cationic calix[4]pyrroles and anionic porphyrins in water  

Microsoft Academic Search

The formation and characterization of molecular assemblies resulting from mixing of solutions of tetracationic calix[4]pyrroles\\u000a and tetraanionic porphyrins in water are reported. The self-assembly of the complementary building blocks was quantitatively\\u000a studied by UV–vis, 1H NMR, Fluorescence and ESI–MS. Binding constants calculated by absorption spectroscopic titrations were in the range of 103–105 M?1. The results indicate that the cationic thiacalix[4]pyrroles show

Bhaskar Garg; Tanuja Bisht; Shive Murat Singh Chauhan

2010-01-01

251

Electrochemical sensing of anions by (ferrocenylmethyl)trialkylammonium cations in homogeneous solution and in polymer films  

Microsoft Academic Search

Based on ion-pairing interactions, which are strongly reinforced upon oxidation to their ferrocenium form, (ferrocenylmethyl)trialkylammonium cations are able to electrochemically sense dihydrogenphosphate and ATP anions in organic electrolytes through two-wave voltammetric features, allowing their amperometric titration. The successful transfer of these electrochemical sensing properties from the homogeneous phase to an electrode surface was achieved using functionalized polypyrrole films synthesized by

Olivier Reynes; Jean-Claude Moutet; Guy Royal; Eric Saint-Aman

2004-01-01

252

An estimated potentiometric surface of the Death Valley region, Nevada and California, developed using geographic information system and automated interpolation techniques  

SciTech Connect

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.

D`Agnese, F.A.; Faunt, C.C.; Turner, A.K.

1998-07-01

253

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

Microsoft Academic Search

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

Hiroki Ohura; Toshihiko Imato; Yasukazu Asano; Sumio Yamasaki

1998-01-01

254

Detection of Catechol by Potentiometric-Flow Injection Analysis in the Presence of Interferents  

ERIC Educational Resources Information Center

This article describes an undergraduate analytical chemistry experiment developed to teach instrumental lab skills while incorporating common interferents encountered in the real-world analysis of catechol. The lab technique incorporates potentiometric-flow injection analysis on a dibenzo-18-crown-6 dual platinum electrode to detect catechol in…

Lunsford, Suzanne K.; Widera, Justyna; Zhang, Hong

2007-01-01

255

Collaborative study of a potentiometric method for the determination of fluoride in vegetation  

Microsoft Academic Search

A collaborative test was performed to evaluate a new potentiometric method for the analysis of fluoride in vegetation. The study was designed to provide estimates of accuracy and within- and between-laboratory precision of a method that employs extraction of fluoride, followed by analysis with an ion selective electrode. A group of laboratories experienced in fluoride analysis was provided with representative

J. S. Jacobson; L. I. Heller

1975-01-01

256

COMPUTER ANALYSIS OF POTENTIOMETRIC AND SOLVENT EXTRACTION STUDIES OF THE FLUORIDE COMPLEXES OF HAFNIUM  

Microsoft Academic Search

Measurements on fluoride-containing hafnium solutions in 3M perchlorate ; media at 25 deg C by precision potentiometry and by solvent extraction ; distribution using thenoyltrifluoroacetone (TTA) and tri-n-octylphosphine oxide ; (TOPO) were subjected to high-speed digital computer analysis and the results ; interpreted in terms of the nature and stabilities of complex hafnium fluoride ; species present. Potentiometric hydrogen ion

L. P. Varga; D. N. Hume

1962-01-01

257

Sensors and Actuators B 113 (2006) 162168 Dependence of potentiometric oxygen sensing  

E-print Network

Sensors and Actuators B 113 (2006) 162­168 Dependence of potentiometric oxygen sensing-based oxygen sensor is presented. Platinum (Pt), lanthanum strontium iron cobalt oxide (La0.6Sr0.4Fe0.8Co0.2O3. But, the measured response times for oxygen sensors using these electrodes showed values of the order

Dutta, Prabir K.

258

POTENTIOMETRIC RESPONSE AND MECHANISM OF ANIONIC RECOGNITION OF HETEROCALIXARENE-BASED ION SELECTIVE ELECTRODES  

PubMed Central

The ion selective electrode (ISE)-based potentiometric approach is shown to be an effective means of characterizing the anion recognition sites in the molecular receptor calix[2]pyridino[2]pyrrole (CPP). In particular, potentiometric pH-measurements involving the use of experimental PVC-membranes based on CPP revealed the existence of both mono- and diprotonated forms of the receptor under readily accessible conditions. Based on these analyses, apparent surface protonation constants for this heterocalixarene were found to lie between 8.5–8.9 (pKB1) and 3.3–3.8 (pKB2). CPP was found to interact with targeted anionic analytes based on both coulombic and hydrogen bond interactions, as inferred from varying the kinds of ionic sites present within the membrane phase. Potentiometric selectivity studies revealed that CPP preferred “Y-shaped” anions (e.g. acetate, lactate, benzoate) over spherical anions (e.g. fluoride and chloride), fluoride over chloride within the set of spherical anions, and the ortho- isomer over the corresponding meta- and para- isomers in the case of hydroxybenzoate (salicylate and congeners). In the context of this study the advantages of potentiometric determinations of acetylsalicylic acid using optimized PVC-membranes based on CPP relative to more conventional PVC-membrane ISEs based on traditional anion exchanger were also demonstrated. PMID:17386780

Shishkanova, T.V.; Sykora, D.; Sessler, J.L.; Kral, V.

2007-01-01

259

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

Microsoft Academic Search

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

Priti Mulchandani; Ashok Mulchandani; Irina Kaneva; Wilfred Chen

1999-01-01

260

Potentiometric and Spectrophotometric Determination of the Ionic Composition of Concentrated Sodium Polysulfides  

Microsoft Academic Search

The concentrations of ionic species in polysulfide electrolytes of photoelectrochemical converters, calculated from the results of potentiometric and spectrophotometric measurements in concentrated polysulfide solutions, are presented. The possible processes that occur at the semiconducting CdSe photoelectrode and involve electrically active species are discussed.

V. S. Vorobets; S. K. Kovach; G. Ya. Kolbasov

2003-01-01

261

Molecularly imprinted polymer-based potentiometric sensor for degradation product of chemical warfare agents  

Microsoft Academic Search

A biomimetic potentiometric sensor for the specific recognition of methylphosphonic acid (MPA), the degradation product of nerve agents sarin, soman, VX, etc., was designed. This involves the preparation of MPA imprinted polymer particles and removal of the template by soxhlet extraction. Subsequently, the leached MIP particles were dispersed in 2-nitrophenyloctyl ether (plasticizer) and embedded in polyvinyl chloride matrix. The sensor

K. P. Prathish; K. Prasad; T. Prasada Rao; M. V. S. Suryanarayana

2007-01-01

262

Lead in Hair and in Red Wine by Potentiometric Stripping Analysis: The University Students' Design.  

ERIC Educational Resources Information Center

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)

Josephsen, Jens

1985-01-01

263

Complexation Effect on Redox Potential of Iron(III)-Iron(II) Couple: A Simple Potentiometric Experiment  

ERIC Educational Resources Information Center

A titration curve with multiple inflection points results when a mixture of two or more reducing agents with sufficiently different reduction potentials are titrated. In this experiment iron(II) complexes are combined into a mixture of reducing agents and are oxidized to the corresponding iron(III) complexes. As all of the complexes involve the…

Rizvi, Masood Ahmad; Syed, Raashid Maqsood; Khan, Badruddin

2011-01-01

264

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

USGS Publications Warehouse

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.

Mashburn, Shana L.; Magers, Jessica

2011-01-01

265

Interaction between bisphenol A and tannic Acid: Spectroscopic titration approach  

NASA Astrophysics Data System (ADS)

The interaction between tannic acid (TA) and bisphenol A (BPA), an endocrine disruptor, was studied by absorption and fluorescence titration techniques. The binding constants and corresponding thermodynamic parameters at different temperatures (294, 296, 298, 300 and 303 K) were determined. The intrinsic fluorescence of BPA was strongly quenched by TA and the quenching mechanism is attributed to static quenching. The thermodynamic data revealed that the formation of TA-BPA complex was exothermic, entropic-driven, and spontaneous. Furthermore, hydrogen and van der Waals interactions seem to be the major driving forces for the formation of the nonfluorescent TA-BPA complex.

Omoike, Anselm; Brandt, Benjamin

2011-06-01

266

Basic Exchangeable Cations in Soils.  

National Technical Information Service (NTIS)

Several possible solutions for displacing basic exchangeable cations have been tested on some agricultural soils. The quantities of cations which the solutions could displace varied according to the nature of the displacing ion. This behaviour is comparab...

B. M. Tucker

1971-01-01

267

Open-cell titration of seawater for alkalinity measurements by colorimetry using bromophenol blue combined with a non-linear least-squares method.  

PubMed

The open-cell titration of seawater was studied for alkalinity measurements by colorimetry. 1) The colorimetric pH of free hydrogen ion concentration, pH(F(ind)), was calculated from the ratio of the absorbances at 436 and 590 nm (R = (590nm)A/(436nm)A), along with the molar absorption coefficient ratios (e(1), e(2) and e(3)/e(2)) and a tentative acid dissociation constant value (pK(a(2))). 2) The perturbation of hydrogen ion was evaluated from the change in titration mass (Deltam). The total hydrogen ion concentration at m + Deltam, pH(T(at m+Deltam)), was calculated using pH(F(ind)) for a mass m and constants for sulfate (S(T)) and fluoride (F(T)). 3) The alkalinity (A(T)) was computed from the titrant mass (m + Deltam) and the corresponding pH(T(at m+Deltam)) through a non-linear least-squares approach using the pK(a(2)) value as a variable parameter. Seawater sample at 2000 m depth from the West Pacific was analyzed. The resulting A(T) (2420.92 +/- 3.35 micromol kg(-1)) was in good agreement with the A(T) measured by potentiometric electric force (2420.46 +/- 1.54 micromol kg(-1)). The resulting pK(a(2)) was 3.7037, in close proximity to that reported by King et al. (pK(a(2)) = 3.695). PMID:20543505

Okamura, Kei; Kimoto, Hideshi; Kimoto, Takashi

2010-01-01

268

Acetoclastic methanogenic activity measurement by a titration bioassay.  

PubMed

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

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

2002-01-01

269

Forces Between Cationic Surfactants  

NASA Astrophysics Data System (ADS)

Experiments have been performed on a binary mixture of the liposome forming surfactants, DODAB (cationic) and DOPE (zwitterionic), which are used as DNA transfection agents. Langmuir isotherms were studied at different compositions, salt concentrations, and temperatures. The data was used to calculate the excess free energy of mixing. To further understand the non-ideal interactions, the surface forces apparatus (SFA) was utilised to measure the forces between bilayers, under varying conditions, which expose DODAB in the outer monolayers.

Campbell, Samuel; Meyer, Joan; Park, Chad; Lasic, Dan; Israelachvili, Jacob

1996-03-01

270

Synthesis, characterization of silica gel phases-chemically immobilized-4-aminoantipyrene and applications in the solid phase extraction, preconcentration and potentiometric studies.  

PubMed

Two new 4-aminoantipyrene chemically-immobilized silica gel phases: ii (N,N-donor) and iii (N,O-donor), were synthesized and characterized by IR and surface coverage determination. The latter was accomplished by thermal desorption and metal probe methods, giving 0.300 and 0.312 mmol g(-1) for ii and 0.220 and 0.250 mmol g(-1) for iii. Moreover, potentiometric titration provided a surface coverage of 0.323 mmol g(-1) for ii. The metal capacity values in mmol g(-1) of ii, iii and the active silica gel phase i for a series of di- and trivalent metal ions were determined at pH 1.0 - 6.7. Phase i showed the lowest values, while ii and iii reflected higher affinity toward most of the metal ions. The highest values were 0.300 for Hg(II)-ii and 0.220 mmol g(-1) for Cd(II)-iii. Distribution coefficients (log Kd) were in the range of 3.57 - 4.76 for ii and 2.32 - 3.46 for iii, thus confirming certain selectivity characters of the solid extractors. The application of the phases as solid extractors and preconcentrators for some heavy metal ions is presented. Good percentage extraction and removal of 94 - 98 +/- 4 - 6% of the spiked 1.000 microg ml(-1) of Hg(II), Cd(II), Pb(II), Cu(II) and Zn(II) and good percentage recovery of 94 - 99 +/- 3 - 6% of 50 ng ml(-1) of these ions from tap water samples were obtained. Stability constants of H(I) and Cu(II) with ii for the two-phase mixture at 25 degrees C and I = 0.1 (KCI) were determined potentiometrically. The pKa of ii are 5.6 and 8.4, while the log K values for CuHL and CuL (L = ii) are 6.3 and 5.8, respectively, leading to the determination of several analytical data for Cu(II)-ii. PMID:15171292

Osman, Mohamad M; Kholeif, Sherif A; Abou-Almaaty, Nevine A; Mahmoud, Mohamad E

2004-05-01

271

Coulometric titration of organic and pharmaceutical compounds with electrogenerated gold(III)  

Microsoft Academic Search

Summary Electrogenerated AuCl4- in 0.02M HCl is used to titrate hydroquinone, ascorbic acid, phenylhydrazine, phenelzine sulphate and phenylsemicarbazide, with biamperometric end-point detection. Titration recoveries are reported and compared with results of coulometry with ceric sulphate oxidation. With less than 1 mg of sample, successive titrations can be performed in the same solution, in contrast to coulometry with ceric sulphate. Phenelzine

Marianne Chateau-Gosselin; Gary D. Christian; Gaston J. Patriarche

1979-01-01

272

Maltodextrins as new chiral selectors in the design of potentiometric, enantioselective membrane electrodes.  

PubMed

Maltodextrins (dextrose equivalent (DE) 4.0-7.0, 13.0-17.0, and 16.5-19.5) are proposed as novel chiral selectors for the construction of potentiometric, enantioselective membrane electrodes. The potentiometric, enantioselective membrane electrodes can be used reliably for the assay of S-captopril as raw material and in pharmaceutical formulations such as Novocaptopril tablets, by use of direct potentiometry. The best response was obtained when maltodextrin with higher DE was used for construction of the electrode. The best enantioselectivity and time-stability was achieved for the lower DE maltodextrin. L-proline was found to be the main interferent for all the proposed electrodes. The surface of the electrodes can be regenerated by simply polishing; this furnishes a fresh surface ready for use in a new assay. PMID:11393233

Stefan, R I; van Staden, J F; Aboul-Enein, H Y

2001-05-01

273

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

PubMed Central

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

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

2009-01-01

274

Approximate potentiometric surface of the bedrock aquifer at Great Bay, southeastern New Hampshire, 2001  

USGS Publications Warehouse

Ground-water elevations (heads) in 265 wells were used to map the potentiometric-head surface in the fractured-bedrock aquifer adjacent to Great Bay, N.H. Remotely sensed data, spring-water temperatures and specific conductances, land-surface elevations, and simulated heads were also used to guide construction of the potentiometric surface. Heads in the bedrock aquifer locally varied more than 20 ft (feet) between adjacent wells as little as 200 ft apart. The depth to water below land surface was greater on the western and northwestern sides of the bay (about 20 ft) than on the southern and eastern sides (about 8 ft). Topography has a greater effect on heads than does temporal variation or measurement accuracy. Head gradients are steeper at the southern side of Great Bay, where the topographic relief is greatest, than at the northwestern and northeastern sides.

Roseen, Robert M.; Degnan, J. R.; Brannaka, L. K.; Ballestero, T. P.; Mack, T. J.

2003-01-01

275

The effects of solubility, ionization, and polarity on end points in high frequency titrations  

E-print Network

of the titx'ation product sauee4 a heavy loa4ing on the cecil latox' ~ Continual dissolut ion an4 ionisat Lcn of tho titration product with the addition of the titrant solvents caused the loading which chaxactex'ised the acid titration curves. A titrant... and Standardisation ef Reagents Procedure Disoussion of Experijsontal Results Tho Effeot of the Dielectric Constants of the Solvents The Initial Solubility of tho Titration Product Tho Slope of a Titration Cmve Loading by Exoass Titrant Tho Insoluble Product...

White, James Decker

2012-06-07

276

Investigation of moisture and acids in nonaqueous mixtures by means of high frequency titration methods  

E-print Network

SY KGB, . OP HIQK liBEQ0EKY TITRATION RNSQDS 4 Thesis Vesta LalOLV TIQRee hype'oval as to style aol co@tent x'ecommealel& Heal of the Department of Chemtstrg XN3$TXGAHON OF RQXSTMR kS? VOIDS IW NOHLQEQUS MXITOHES BY lKLHS OF 'BICB FRS@3i... for the Titration of kohle and water in the 'Prosonoe of Rethgl kloohol oith Sodioa Rothjr1ato ~ ~ ~ ln Ixi Titration of phonylaootio aoQ in nethyl kloohol ~ ~ ? 15 , XXX? Titration of- koetio koid Xn koetone?? . ? ~ ??? ' ~ ~ ?, XS XV? Titratien Of Stearie keid...

Turner, Vester Lamar

2012-06-07

277

A simple recoverable titration method for quantitative characterization of amine-functionalized carbon nanotubes  

NASA Astrophysics Data System (ADS)

A simple recoverable titration method is described for quantitative characterization of amine functions attached to the carbon nanotubes (CNTs). This titration is a two-step method, originated from the alkaline nature of amine functions. The amount of amine functions on CNTs determinate by titration method showed a good quantitative agreement with those of thermogravimetric analysis. Interestingly, the titrated samples could be easily recovered to their original activities, with a simple base treatment. Based on simplicity and minimum spent time, this method is suggested for characterization of amine functionalities attached on carbon nanotubes as well as all graphitic nanostructures.

Moaseri, Ehsan; Baniadam, Majid; Maghrebi, Morteza; Karimi, Majid

2013-01-01

278

Analysis of an Oxygen Bleach: A Redox Titration Lab  

NASA Astrophysics Data System (ADS)

An experiment is presented which allows students to balance an oxidation-reduction reaction equation and use the reaction to analyze a consumer product. The experiment calls for students to balance the reaction of H2O2 and MnO4- two different ways (one assuming that H2O2 is the oxygen source and a second assuming that MnO4- is the oxygen source). They then determine which of these balanced equations has the correct stoichiometry by titrating a standard H2O2 solution with KMnO4. Finally, they use the correct balanced equation to determine the mass percent of H2O2 in a commercially available, "environmentally friendly" oxygen bleach solution.

Copper, Christine L.; Koubek, Edward

2001-05-01

279

Historical article: Titration studies and the structure of DNA.  

PubMed

During the period of 1946-1956 ideas on the structure of the nucleic acids, especially DNA, were profoundly influenced by physico-chemical studies and, in particular, by electrometric titration studies pioneered by J. Masson Gulland and D.O. Jordan. It was eventually conclusively inferred when such studies had been sufficiently refined that: in DNA, the only hydrogen bonding that occurred was between the 1:6 amino groups of adenine and cytosine, and the -NH-CO "enolic" groups of thymine and guanine; the polynucleotide chains of DNA were not branched (or interrupted); and the internally hydrogen-bonded double-helical structure was stable both in aqueous solution and in the fibrous state. PMID:15752988

Peacocke, Arthur

2005-03-01

280

Liquid chromatography of carboxylic acids using potentiometric detection with a tungsten oxide electrode  

Microsoft Academic Search

A tungsten oxide electrode was evaluated for potentiometric detection of carboxylic acids separated using various liquid Chromatographic methods, such as reversed-phase, ion-interaction and ion-exclusion. The separation of formic, acetic, propionic and butyric acids was performed using reversed-phase chromatography with 10% methanol\\/water solution at pH 6.0 as the eluent. The calibration plots were linear in the range 0.5–3.0 mmol, and the

ZuLiang Chen; Peter W. Alexander; Paul R. Haddad

1997-01-01

281

A Generic Design of a Flow-Through Potentiometric Sensor Array  

Microsoft Academic Search

.  ?In this paper, a flow-through potentiometric microsensor is described which is based on semi-permeable tubing. The ion selective\\u000a electrodes proposed are of the liquid membrane type in which a dialysis tube captures the ion selective cocktail. Ion selective\\u000a sensors and a reference electrode based on the same design were constructed by guiding a 0.3?mm diameter dialysis tube through\\u000a a cavity

Sebastian Böhm; Wouter Olthuis; Piet Bergveld

2000-01-01

282

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

USGS Publications Warehouse

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

Mularoni, R. A.

1994-01-01

283

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

PubMed

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

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

284

Binding of cationic surfactants to a thermo-sensitive copolymer below and above its cloud point.  

PubMed

The binding interactions between cationic surfactants and a statistical thermo-sensitive copolymer based on oligo(ethylene glycol) methacrylates were studied by isothermal titration calorimetry (ITC), surfactant selective electrode (SSE) and dynamic light scattering (DLS). Strong binding interactions were observed between this copolymer and cationic surfactants. The binding is driven by the hydrophobic effect, occurring on the hydrophobic backbone instead of the ethylene-glycol side chains. The surfactant saturation concentration C2 depended on the polymer concentration, but was not affected by temperature. Three types of cationic alkyltrimethylammonium bromide surfactants (RTAB with R equal to C12, C14, and C16), namely, dodecyltrimethylammonium bromide (DoTAB), tetradecyltrimethylammonium bromide (TTAB), and cetyltrimethylammonium bromide (CTAB), were examined, and the results confirmed that the binding affinity followed the sequence: CTAB>TTAB>DoTAB. PMID:24144369

Peng, Baoliang; Han, Xia; Liu, Honglai; Tam, Kam C

2013-12-15

285

The Bakery Algorithm: Yet Another Speci cation and Veri cation  

E-print Network

1 The Bakery Algorithm: Yet Another Speci cation and Veri cation Egon Borger Yuri Gurevichy Dean's bakery algorithm. We construct two evolving algebras capturing lower and higher view respectively, enabling a simple and concise proof of correctness for the bakery algorithm.x Introduction Uri Abraham

Börger, Egon

286

Age-adapted morphine titration produces equivalent analgesia and adverse effects in younger and older patients  

E-print Network

in these patients is of importance because inadequate analgesia is likely to increase postoperative confusionAge-adapted morphine titration produces equivalent analgesia and adverse effects in younger Summary Background To determine efficacy and safety of postoperative titrated morphine in elderly patients

Paris-Sud XI, Université de

287

Age adapted morphine titration produces equivalent analgesia and side effects in younger and older patients  

E-print Network

period. Keywords: POSTOPERATIVE ANALGESIA, intravenous morphine titration, efficient and safe pain relief and management of postoperative pain in these patients is of importance because inadequate analgesia is likely1 Age adapted morphine titration produces equivalent analgesia and side effects in younger

Boyer, Edmond

288

Effects of Acute and Chronic Cocaine Administration on Titrating-Delay Matching-to-Sample Performance  

ERIC Educational Resources Information Center

The effects of cocaine were examined under a titrating-delay matching-to-sample procedure. In this procedure, the delay between sample stimulus offset and comparison stimuli onset adjusts as a function of the subject's performance. Specifically, matches increase the delay and mismatches decrease the delay. Titrated delay values served as the…

Kangas, Brian D.; Branch, Marc N.

2012-01-01

289

Monitoring of an RNA Multistep Folding Pathway by Isothermal Titration Calorimetry  

E-print Network

Monitoring of an RNA Multistep Folding Pathway by Isothermal Titration Calorimetry Ce�dric Reymond Sherbrooke, Sherbrooke, Que�bec, Canada ABSTRACT Isothermal titration calorimetry was used to monitor calorimetry appears to be a method of choice for the elucidation of an RNA's folding pathway. INTRODUCTION

Perreault, Jean-Pierre

290

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

E-print Network

and the zeta potential is that the latter applies at the plane of shear, which may be up to 2-3 water diametersComparison of the Zeta Potential with the Diffuse Layer Potential from Charge Titration Phil Attard) theory is used to compare charge titration and zeta potential data for several colloids. It is found

Attard, Phil

291

Rapid and simple determination of oxyphenbutazone in dosage forms by biamperometric titration.  

PubMed

Oxyphenbutazone was determined in the presence of glacial acetic acid, hydrochloric acid, and potassium bromide by bromometric titration with biamperometric end point indication. The course of the titration was followed with double platinum electrode with 100 mV of polarizing voltage. PMID:3700329

Sebková, D; Safarík, L

1986-01-01

292

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

Microsoft Academic Search

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.

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

1999-01-01

293

Quantitative analysis of dimethyl titanocene by iodometric titration, gas chromatography and NMR  

Microsoft Academic Search

In this study we report the use of an automated iodometric titration method and a novel gas chromatography (GC) method for the quantitative analysis of dimethyl titanocene (DMT), a key raw material in drug synthesis. Both approaches are based on the reaction of DMT in toluene or tetrahydrofuran solutions with iodine. In the case of iodometric titration, excess iodine is

Anant Vailaya; Tao Wang; Yadan Chen; Mark Huffman

2001-01-01

294

[Simultaneous determination of calcium and magnesium by calculative spectrophotometric complexometric titration].  

PubMed

A new spectrophotometric complexometric titration method coupled with chemometrics for the determination of mixtures of metal ions has been developed. In the method described here, the titrant is a mixture of EDTA and two indicators. In the process of titration, both the volumetric addition of titrant and the progress of titration reaction can be characterized simultaneously by chemometric calculation with the absorption spectra, and then the titration curves can be obtained. With the titration curves, a matrix equation can be established, and thus the concentration of each component in the mixture of metal ions can be calculated with principal component regression. The method only needs the information of absorption spectra to obtain the analytical results, and is free of volumetric measurements. So the method is simple, convenient and precise, and has been applied to the simultaneous determination of mixtures of calcium and magnesium using malachite green and Cu-PAN as indicators with satisfactory results. PMID:18330321

Liao, Li-fu; Xiao, Xi-lin; Yang, Ming-hui; Yang, Jing

2007-12-01

295

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

PubMed Central

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

Legangneux, Eric; Gardin, Anne; Johns, Donald

2013-01-01

296

Characterization of membrane protein interactions by isothermal titration calorimetry.  

PubMed

Understanding the structure, folding, and interaction of membrane proteins requires experimental tools to quantify the association of transmembrane (TM) helices. Here, we introduce isothermal titration calorimetry (ITC) to measure integrin ?IIb?3 TM complex affinity, to study the consequences of helix-helix preorientation in lipid bilayers, and to examine protein-induced lipid reorganization. Phospholipid bicelles served as membrane mimics. The association of ?IIb?3 proceeded with a free energy change of -4.61±0.04kcal/mol at bicelle conditions where the sampling of random helix-helix orientations leads to complex formation. At bicelle conditions that approach a true bilayer structure in effect, an entropy saving of >1kcal/mol was obtained from helix-helix preorientation. The magnitudes of enthalpy and entropy changes increased distinctly with bicelle dimensions, indicating long-range changes in bicelle lipid properties upon ?IIb?3 TM association. NMR spectroscopy confirmed ITC affinity measurements and revealed ?IIb?3 association and dissociation rates of 4500±100s(-1) and 2.1±0.1s(-1), respectively. Thus, ITC is able to provide comprehensive insight into the interaction of membrane proteins. PMID:25178257

Situ, Alan J; Schmidt, Thomas; Mazumder, Parichita; Ulmer, Tobias S

2014-10-23

297

Monitoring denitrification by pH-Stat titration.  

PubMed

An improved pH-stat titrimetric procedure was developed, validated, and extensively applied to monitor biological heterotrophic denitrification in a lab-scale sequencing batch reactor (SBR). So far, titrimetric procedures were not successful in monitoring denitrification processes in full-scale wastewater (WW) treatment plants, mainly because the stoichiometric ratio between proton production and nitrate reduction is highly variable due to variability of both biomass and influent WW characteristics. In this article, a new titration procedure is proposed where a simple calibration step is performed before each experimental test. This procedure allows for the assessment of (i) nitrate content in a sample of mixed liquor; (ii) the maximum denitrification rate of sludge when fed on acetate; and (iii) the denitrification potential (DNP) of different substrates. As for (i), validation by comparison with spectrophotometric measures indicated an average discrepancy of less than 3% on more than 40 samples; as for (ii) and (iii) collected values compared well with literature data. The titrimetric method proposed here is also capable of assessing the biomass anoxic yield in a very simple way, since it does not require any analytical nitrate determination. According to the results of this experimentation, titrimetry appeared to be a simple, inexpensive, and powerful tool for monitoring and operating denitrification processes in WW treatment plants. PMID:17721878

Ficara, Elena; Canziani, Roberto

2007-10-01

298

A modified function of the formula of double iodometric titration  

NASA Astrophysics Data System (ADS)

Double iodometric titration is the most useful method to determine oxygen content of high Tc superconductors. Its traditional calculating formula is not accurate enough, and a new calculating formula has just been put forward. To understand which relationship of the traditional formula depends on the new one is an important problem. On studying the new formula, we find a modified function F relating the traditional formula to the new one, and also find that the value of F depends only on molar weight of the superconductor. For Y, Bi, and Hg systems, a group of curves of the modified function are put forward here. Since many results about average copper valence and oxygen content have been published, to correct those results one can modify them by means of the corresponding F. As a sample, we modify two published data of average copper valence and oxygen content of Y and Bi systems. After comparing the unmodified with the modified data, we find that it is necessary to modify the published data for quantitative research.

Chen, Wu Ming; Chen, J.; Jin, X.

1997-02-01

299

Factors governing the assembly of cationic phospholipid-DNA complexes.  

PubMed Central

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

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

2000-01-01

300

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

PubMed

New, simple and convenient potentiometric and spectrophotometric methods are described for the determination of dextromethorphan hydrobromide (DXM) in pharmaceutical preparations. The potentiometric technique is based on developing a potentiometric sensor incorporating the dextromethorphan tetrakis(p-chlorophenyl)borate ion-pair complex as an electroactive species in a plasticized PVC matrix membrane with o-nitophenyl octyl ether or dioctyl phthalate. The sensor shows a rapid near Nernstian response of over 1 × 10(-5) - 1 × 10(-2) mol L(-1) dextromethorphan in the pH range of 3.0 - 9.0. The detection limit is 2 × 10(-6) mol L(-1) DXM and the response time is instantaneous (2 s). The proposed spectrophotometric technique involves the reaction of DXM with eriochrom black T (EBT) to form an ion-associate complex. Solvent extraction is used to improve the selectivity of the method. The optimal extraction and reaction conditions have been studied, and the analytical characteristics of the method have been obtained. Linearity is obeyed in the range of 7.37 - 73.7 × 10(-5) mol L(-1) DXM, and the detection limit of the method is 1.29 × 10(-5) mol L(-1). The relative standard deviation (RSD) and relative error for six replicate measurements of 3.685 × 10(-4) mol L(-1) are 0.672 and 0.855%, respectively. The interference effect of some excepients has also been tested. The drug contents in pharmaceutical preparations were successfully determined by the proposed methods by applying the standard-addition technique. PMID:24614739

Elmosallamy, Mohamed A F; Amin, Alaa S

2014-01-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

302

Catalyzed decomposition of nerve gases and potentiometric detection of the byproducts  

Microsoft Academic Search

Several systems are presented for detection of nerve gases, Sarin and Soman, based on catalyzed decomposition of nerve gases by copper ion–ligand chelates and potentiometric detection of the byproduct, fluoride ion. Diisopropyl fluorophosphate (DFP) was used as the nerve gas mimic. It was found that 1:1 Cu(II)–DMBP (4,4?-dimethyl-2,2?-bipyridyl) and 1:2 Cu(II)–TMEDA (N,N,N?N?-tetramethylethylenediamine) chelates were the most effective catalysts for accelerating

Yuanwu Xie; Branko N. Popov

2001-01-01

303

Potentiometric surfaces of the intermediate aquifer system, west-central Florida, September, 1993  

USGS Publications Warehouse

A map of the September 1993 potentiometric surface of the intermediate aquifer system in west- central Florida depicts water levels for the annual high water-level period. Water levels measured in September 1993 were generally below those reported for September 1992. In 134 wells with paired measurements, the September 1993 level ranged from 4.86 feet below to 5.91 feet above the September 1992 level and averaged 0.59 foot below the September 1992 level. The general decline in water levels during this period was largely the result of below normal rainfall and above average seasonal ground-water withdrawals.

Mularoni, R. A.

1994-01-01

304

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

NASA Astrophysics Data System (ADS)

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.

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

2011-06-01

305

Utilization of maltodextrin based enantioselective, potentiometric membrane electrodes for the enantioselective assay of S-perindopril.  

PubMed

Enantioselective, potentiometric membrane electrodes (EPMEs) based on carbon paste impregnated with different maltodextrins {dextrose equivalent (DE) 4.0-7.0 (I), 13.0-17.0 (II) and 16.5-19.5 (III)} as chiral selectors for the assay of S-perindopril is described. The proposed electrodes could be reliably employed in the assay of S-perindopril raw material and from its pharmaceutical formulation, Coversyl((R)) tablets. The electrode based on maltodextrin (I) showed the best enantioselectivity and time-stability. The surfaces of the electrodes are easily renewable by simply polishing on an alumina paper. PMID:18969348

Ozoemena, Kenneth I; Stefan, Raluca-Ioana; van Staden, Jacobus F; Aboul-Enein, Hassan Y

2004-03-10

306

A paper-based potentiometric cell for decentralized monitoring of Li levels in whole blood.  

PubMed

A novel approach to monitor Li levels in blood in decentralized (out of the lab) settings is presented. The approach uses a potentiometric cell fully made with filter paper as a support. Electrodes were built using carbon nanotubes ink to create a conductive path and a suitable polymeric membrane. Solid-state ion-selective electrodes for Li and a reference electrode were built and optimized. The results obtained on real samples of serum and whole blood are comparable with those obtained by conventional standard approaches. This platform shows an outstanding performance for the direct, fast and low-cost monitoring of Li levels in blood. PMID:24513977

Novell, Marta; Guinovart, Tomàs; Blondeau, Pascal; Rius, F Xavier; Andrade, Francisco J

2014-04-01

307

Virtual Instrument for an Automated Potentiometric e-Tongue Employing the SIA Technique  

PubMed Central

In this work we report the design, construction, and applications of an electronic tongue (abbreviated e-tongue) based on an array of potentiometric sensors employing the Sequential Injection Analysis technique (SIA) operated as a Virtual Instrument implemented in LabVIEW6.1™. The system can use transient and stationary responses as the measured input information for e-tongues. The new concepts applied, lead to different advantages to be obtained, such as complete automation, easy handling, saving time, reliability and modularity.

Duran, Alejandro; Cortina, Montserrat; Velasco, Lya; Rodriguez, Jose Antonio; Alegret, Salvador; del Valle, Manuel

2006-01-01

308

Potentiometric maps of the Sparta Sand, northern Louisiana and southern Arkansas, 1900, 1965, 1975, and 1980  

USGS Publications Warehouse

The potentiometric surface of the Sparta Sand in northern Louisiana is shown by contours on four maps. Maps for 1900, 1965 , and spring 1975 are generalized, small-scale maps from previously published reports. The spring 1980 map (1:500,000) is based on measurements in 144 wells and includes the southern tier of counties in southern Arkansas. The map shows regional effects of pumping from the Sparta Sand and effects of local pumping centers at Magnolia and El Dorado, Ark., and at Minden, Ruston, Jonesboro-Hodge, Winnfield, Bastrop, and in the Monroe area of Louisiana. (USGS)

Ryals, G.N.

1980-01-01

309

On the Physical Meaning of the Isothermal Titration Calorimetry Measurements in Calorimeters with Full Cells  

PubMed Central

We have performed a detailed study of the thermodynamics of the titration process in an isothermal titration calorimeter with full cells. We show that the relationship between the enthalpy and the heat measured is better described in terms of the equation ? H = Winj + Q (where Winj is the work necessary to carry out the titration) than in terms of ?H = Q. Moreover, we show that the heat of interaction between two components is related to the partial enthalpy of interaction at infinite dilution of the titrant component, as well as to its partial volume of interaction at infinite dilution. PMID:20054472

Grolier, Jean-Pierre E.; del Rio, Jose Manuel

2009-01-01

310

Selective determination of gas dialysable components in complex sample solutions using triangle programmed coulometric titration in continuous flow systems  

Microsoft Academic Search

A precisely and sensitively working coulometric flow titration procedure was developed to determine ammonium\\/ammonia and sulphide\\/hydrogen sulphide in leachate from a municipal waste landfill site. The selectivity of coulometric titration with electrogenerated hypobromite could be essentially improved by the combination with a continuously and quantitatively working thin layer gas dialysis cell, which was integrated in the flow titration setup in

M Becker; B Fuhrmann; U Spohn

1996-01-01

311

Louisiana Ground-Water Map No. 13: Hydrogeology and Potentiometric Surface of the Sparta Aquifer in Northern Louisiana, October 1996  

USGS Publications Warehouse

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

Brantly, Jeffrey A.; Seanor, Ronald C.; McCoy, Kaycee L.

2002-01-01

312

Louisiana Ground-Water Map No.13: Hydrogeology and Potentiometric Surface of the Sparta Aquifer in Northern Louisiana, October 1996  

USGS Publications Warehouse

This report describes the thickness and areal extent of the Sparta aquifer, identifies sands within the fresh-water extent of the aquifer, and presents data and a map that illustrate the generalized potentiometric surface (water levels) during October 1996. The report includes a detailed geophysical log, structure contour maps, hydrogeologic sections, and hydrographs of water levels in selected wells. The potentiometric surface-map can be used for determining direction of ground-water flow, hydraulic gradients, and the effects of withdrawals on the aquifer.

Brantly, Jeffrey A.; Seanor, Ronald C.; McCoy, Kaycee L.

2002-01-01

313

The potentiometric and thermodynamic properties of some divalent metal ions with biologically active 2-phenyl-3-(2'-hydroxy-5'-methylbenzylidine)-quinazoline-4-(3h)-one Schiff's base  

NASA Astrophysics Data System (ADS)

The formation constants of 1: 1 and 1: 2 complexes between Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Cu(II), Ba(II), Mg(II), Mn(II), Th(IV), and UO2 (II) metal ions and 2-phenyl-3-(2'-hydroxy-5'-methylbenzylidine)-quinazoline-4-(3H)-one [PHBMeQ] were determined potentiometrically at 30 ± 0.1 °C and different ionic strengths (0.025, 0.05, 0.10, 0.15, and 0.20 M NaNO3) in 60: 40 (v/v) alcohol-water solutions. The proton-ligand and metal-ligand formation constants were determined pH-metrically by the Calvin-Bjerrum titration technique. The order of stability constants was found. The negative ? G° values suggest that the reactions occur spontaneously. Correlations between the log K 1 values and some fundamental central metal ion properties are discussed.

Shivakumar, K.; Shashidhar; Halli, M. B.

2008-12-01

314

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

E-print Network

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 ...

Amadi, Ovid Charles

2007-01-01

315

Effect of Molecular Acid-Base Dissociation of Salts on Conductometric Titration Curves in Acetonitrile.  

National Technical Information Service (NTIS)

The main objectives of the paper are to calculate Kf and Kd from the characteristics of conductometric titration curves at different initial concentrations of acid. Equations were derived to find, under specified conditions, Kf from the location of and Kd...

I. M. Kolthoff, M. K. Chantooni

1964-01-01

316

EDTA titration of bismuth(III) in ores and concentrates with biamperometric indication  

Microsoft Academic Search

A method is described for the chelatometric titration of bismuth(III) with biamperometric indication. It is applied to ores and concentrates and can also be used in presence of interfering elements (as Zr, Tl, In, Mo, Cu, Fe).

J. Vorlí?ek; P. Peták; Z. Šulcek

1968-01-01

317

Optimal Conditions for Masking of Sulfite Anions with Formaldehyde in Iodometric Titration of Photographic Fixing Solutions  

Microsoft Academic Search

The iodometric titration of photographic fixing solutions can be simplified by masking sulfite anions with 3% aqueous formaldehyde in a weakly acidic medium, instead of their standard masking with concentrated aqueous formaldehyde in weakly alkaline solutions.

V. N. Kiryushov; L. I. Skvortsova

2005-01-01

318

Binding of Bovine Serum Albumin to Heparin Determined by Turbidimetric Titration and Frontal Analysis  

E-print Network

Binding of Bovine Serum Albumin to Heparin Determined by Turbidimetric Titration and Frontal analysis continuous capillary electrophoresis; BSA, bovine serum albumin; SEC, size quantita- tively. Here we demonstrate the application of capillary electrophoresis to the system of serum

Dubin, Paul D.

319

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

PubMed

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

Arvand, Majid; Samie, Hedyeh Asadi

2013-06-01

320

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

USGS Publications Warehouse

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

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

2001-01-01

321

Potentiometric surface and specific conductance of the Sparta and Memphis aquifers in eastern Arkansas, 1995  

USGS Publications Warehouse

The Sparta and Memphis aquifers in eastern and south-central Arkansas are a major source of water for industrial, public supply, and agricultural uses. An estimated 240 million gallons per day was withdrawn from the Sparta and Memphis aquifers in 1995, an increase of about 17 million gallons per day from 1990. During the spring and early summer of 1995, the water level in the Sparta and Memphis aquifers was measured in 145 wells, the specific conductance of 101 ground-water samples collected from those aquifers was measured. Maps of areal distribution of potentiometric surface and specific conductance generated from these data reveal spatial trends in these parameters across the eastern and south-central Arkansas study area. The altitude of the potentiometric surface ranged from about 206 feet below sea level in Union County to about 307 feet above sea level in Saline County. The potentiometric surface of the Sparta and Memphis aquifers contains cones of depression descending below sea level in the central and southern portions of the study area, and a potentiometric high along the western study area boundary. Major recharge areas exhibit potentiometric highs greater than 200 feet above sea level and specific conductance values less than 200 microsiemens per centimeter, and generally are located in the outcrop/subcrop areas on the southern one-third of the western boundary and the northern portion of the study area. The regional direction of ground-water flow is from the north and west to the south and east, away from the outcrop and subcrop and northern regions, except near areas affected by intense ground-water withdrawals; such areas are manifested by large cones of depression centered in Columbia, Jefferson, and Union Counties. The cones of depression in adjoining Columbia and Union Counties are coalescing at or near sea level. The lowest water level measured was about 206 feet below sea level in Union County. Increased specific conductance values were measured in the areas of the cones of depression in Columbia and Union Counties. The cones of depression centered in Jefferson County coincides with an elongate area where ground water in the aquifer has low specific conductance. This area extends eastward from the outcrop/subcrop region of recharge. This extension of ground water with low specific conductance possibly indicates increased ground-water movement to the east-southeast from the outcrop/subcrop area induced by ground- water withdrawals in Jefferson County. Specific conductance increases markedly to the northeast and gradually to the south of this area. Long-term hydrographs of eight wells in the study areas, during the period 1970-1995, reveal water-level declines ranging from less than 0.5 foot per year in Phillips County to more than 2.0 feet per year in Union County. Water-level declines of greater than 1.5 feet per year generally are associated with the cones of depression centered in Columbia, Jefferson, and Union Counties.

Stanton, Gregory P.

1997-01-01

322

A new radiometric titration method based on separation by means of ion exchange  

Microsoft Academic Search

A mathematical expression is derived for the radiocomplexometric determination of a mixture of two metals with one ligand,\\u000a using an anion exchanger in the solution as a phase separating system. An expression is also given for the complexometric\\u000a titration of a metal, when formation of acidic or basic complexes is taken into account. In the experimental part titration\\u000a procedures are

A. Heijink; H. L. Polak

1970-01-01

323

A new radiometric titration method based on separation by means of ion exchange  

Microsoft Academic Search

The determination of zinc with EDTA is chosen as an example for the earlier suggested new radio-complexometric titration procedure,\\u000a in which phase separation is achieved by means of a strongly basic anion exchanger in the solution. Concentrations of zinc\\u000a solutions down to 10?6\\u000a M have been determined. The reverse titration,viz. of EDTA with zinc solution, which can be used as

A. Heijink; H. L. Polak

1969-01-01

324

TITRIMETRIC DETERMINATION OF ZIRCONIUM. I. TITRATION OF ZIRCONIUM WITH POTASSIUM PERMANGANATE IN AN ALKALINE MEDIUM  

Microsoft Academic Search

The possibility of an indirect determination of Zr by an oxidation-; reduction titration of mandelic acid with KMnOâ solution was studied. As a ; preliminary step the method of titrating mandelic acid and p- bromomandelic acid ; with KMnOâ solution in an alkaline medium (l to 2N NaOH) was worked out; Nb\\/; sub 2\\/Oâ, TaâOâ, SiCâ, and WOâ did not

A. Schneer; H. Hartmann

1959-01-01

325

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

PubMed

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 studywas 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 SO4(2-) for contaminated sediments indicated close agreement suggesting that the model could potentially be used to predictthe acid-base behavior of the sediment-solution system under variable pH conditions. PMID:19031894

Zhang, Fan; Luo, Wensui; Parker, Jack C; Spalding, Brian P; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

2008-11-01

326

COMPLEXOMETRIC TITRATION OF RARE EARTH ELEMENTS. DISSOLUTION OF THE RARE EARTH OXALATE WITH ETHYLENEDIAMINETETRAACETIC ACID AND BACK TITRATION WITH MAGNESIUM SULFATE  

Microsoft Academic Search

The processes for dissolution of the oxalate and complexometry to ; determine the small amounts of rare earth rapidly and accurately, were studied. ; Crystalline rare earth oxalate was precipitated and filtered. The precipitate ; was dissolved completely with EDTA in alkaline solution and the excess of EDTA in ; solution was back titrated with standard magnesium sulfate solution. By

Seizo Misumi; Tomitsugu Taketatsu

1959-01-01

327

Simultaneous determination of potassium and total fluoride in toothpastes using a SIA system with two potentiometric detectors  

Microsoft Academic Search

A sequential injection analysis (SIA) system has been developed for the first time to quantify potassium and total fluoride in toothpastes and gels used to prevent both dentinal hypersensitivity and dental caries. To enable this simultaneous determination, potentiometric detection, using a conventional fluoride electrode and a tubular potassium selective electrode, formed by a PVC membrane containing valinomycin as ionophore, was

R. Pérez-Olmos; J. C. Soto; N. Zárate; I. Díez

2008-01-01

328

Potentiometric selectivity of ion-selective electrodes for alkaline-earth elements based on podands with phosphoryl terminal groups  

Microsoft Academic Search

Dependence of the analytical characteristics (detection limits, DLs) and potentiometric selectivity Kijpot) of the ion-selective electrodes (ISEs) based on phosphoryl-containing podands on the structures was investigated. It was demonstrated that the DL was determined by complex facilitated transfer energy. It was shown that the DLs of the majority of the ionophores weakly depend on the lipophilicity of the ionophores. Ionophore

O. M. Petrukhin; A. B. Kharitonov; Yu. I. Urusov; E. V. Schipulo; N. Ye. Kruchinina; V. E. Baulin

1997-01-01

329

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

USGS Publications Warehouse

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)

Wasson, B.E.

1980-01-01

330

Cation Ordering in Layered Nickelates  

NASA Astrophysics Data System (ADS)

The single layer Ruddlesden-Popper nickelates present a model system to understand how the effects of digital dopant cation ordering may affect the properties of 2-dimensional conducting sheets. We investigate the effects of aliovalent A-site cation order on LaSrNiO4 films. Using molecular beam epitaxy, we interleave full layers of SrO and LaO in a series of chemically equivalent films, varying the pattern of SrO and LaO layers relative to the NiO2 layers. Through synchrotron surface x-ray diffraction and Coherant Bragg Rod Analysis (COBRA), we directly investigate the A-site cation order and the resulting atomic displacements for each ordering pattern. We correlate these results with theoretical calculations and transport measurements of the layered nickelate films.

Nelson-Cheeseman, Brittany; Zhou, Hua; Cammarata, Antonio; Hoffman, Jason; Balachandran, Prasanna; Rondinelli, James; Bhattacharya, Anand

2013-03-01

331

High-Resolution Ultrasonic Spectroscopy Study of Interactions between Hyaluronan and Cationic Surfactants.  

PubMed

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

Kargerová, Andrea; Peka?, Miloslav

2014-10-14

332

Calix[4]pyrrole as a Chloride Anion Receptor: Solvent and Counter-Cation Effects  

PubMed Central

The interaction of calixpyrrole with several chloride salts has been studied in the solid state by X-ray crystallography as well as in solution by isothermal titration calorimetry (ITC) and 1H NMR spectroscopic titrations. The titration results in dimethylsulfoxide, acetonitrile, nitromethane, 1,2-dichloroethane and dichloromethane, carried out using various chloride salts, specifically tetraethylammonium (TEA), tetrapropylammonium (TPA), tetrabutylammonium (TBA), tetraethylphosphonium (TEP), tetrabutylphosphonium (TBP), and tetraphenylphosphonium (TPhP) showed no dependence on method of measurement. The resulting affinity constants (Ka's), on the other hand, were found to be highly dependent on the choice of solvent with Ka's ranging from 102?105 being recorded in the test solvents used for this study. In dichloromethane a strong dependence on the counter-cation was also seen, with the Ka's for the interaction with chloride ranging from 102?104. In the case of TPA, TBA and TBP the ITC data could not be fit to a 1:1 binding profile. PMID:16967979

Sessler, Jonathan L.; Gross, Dustin E.; Cho, Won-Seob; Lynch, Vincent M.; Schmidtchen, Franz P.; Bates, Gareth W.; Light, Mark E.; Gale, Philip A.

2008-01-01

333

Potentiometric surface of the upper Floridan Aquifer, west-central Florida, September 1993  

USGS Publications Warehouse

A map of the September 1993 potentiometric surface of the Upper Floridan aquifer in west-central Florida depicts ground-water levels for the annual high water-level period. Water levels measured in September 1993 were generally lower than those reported for September 1992. In 572 wells with paired measurements, the September 1993 level ranged from 9.60 feet below to 4.73 feet above the September 1992 level and averaged 0.41 foot below the September 1992 level. The general decline in water levels during this period was largely the result of below normal rainfall that resulted in above average seasonal ground-water withdrawals from the aquifer.

Mularoni, R. A.

1994-01-01

334

Highly efficient potentiometric glucose biosensor based on functionalized InN quantum dots  

NASA Astrophysics Data System (ADS)

We present a fast, highly sensitive, and efficient potentiometric glucose biosensor based on functionalized InN quantum-dots (QDs). The InN QDs are grown by molecular beam epitaxy. The InN QDs are bio-chemically functionalized through physical adsorption of glucose oxidase (GOD). GOD enzyme-coated InN QDs based biosensor exhibits excellent linear glucose concentration dependent electrochemical response against an Ag/AgCl reference electrode over a wide logarithmic glucose concentration range (1 × 10-5 M to 1 × 10-2 M) with a high sensitivity of 80 mV/decade. It exhibits a fast response time of less than 2 s with good stability and reusability and shows negligible response to common interferents such as ascorbic acid and uric acid. The fabricated biosensor has full potential to be an attractive candidate for blood sugar concentration detection in clinical diagnoses.

Alvi, N. H.; Soto Rodriguez, P. E. D.; Gómez, V. J.; Kumar, Praveen; Amin, G.; Nur, O.; Willander, M.; Nötzel, R.

2012-10-01

335

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

SciTech Connect

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

Kobos, R.K. (Virginia Commonwealth Univ., Richmond); Parks, S.J.; Meyerhoff, M.E.

1982-10-01

336

Water Determination Using Karl Fischer Titration Water content needs to be determined at all stages of the manufacturing process from raw materials to  

E-print Network

by iodine in the presence of water. It is the same reaction as the iodometric titration of sulphur dioxideWater Determination Using Karl Fischer Titration Water content needs to be determined at all stages and ease of use is Karl Fischer titration. The titration is based on the oxidation of sulphur dioxide

Nazarenko, Alexander

337

Real-Time Telemetry System for Amperometric and Potentiometric Electrochemical Sensors  

PubMed Central

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

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

338

The use of magnesium silicate (talc) in a potentiometric sensor for hydrogen ions  

Microsoft Academic Search

The construction and analytical evaluation of a pH sensor based in a matrix containing 20% of [(Mg6Si8O20)](OH)4, a magnesium silicate, talc and 30% graphite dispersed in an epoxy resin (50%) is described. The data obtained from various acid–base titrations were compared with those using a glass electrode in the same conditions. The proposed electrode presented a linear response in the

Marcos F. S. Teixeira; Carla C. S. Cavalheiro; Luiz A. Ramos; Eduardo Almeida Neves

2003-01-01

339

Psychiatric disorder does not preclude adequate continuous positive airway pressure titration.  

PubMed

Obstructive sleep apnea (OSA) is a highly prevalent disorder associated with significant morbidity and multiple complications. A large proportion of patients with OSA also have a coexisting primary psychiatric disorder. The effect of psychiatric disorders on the ability to tolerate continuous positive airway pressure (CPAP) titration is not known. In this study, whether the presence of psychiatric disorders precludes the patients' ability to tolerate CPAP titration for OSA was investigated. A retrospective chart review on a sample of 284 patients who underwent sleep studies in a single-center, university-based Veterans Affairs hospital was performed. A total of 143 patients with OSA who underwent titration of CPAP therapy were identified. The prevalence of psychiatric disorders between patients who tolerated titration and those who did not tolerate it was compared using the ?² test. The percentages of patients with psychiatric disorders who tolerated and did not tolerate CPAP were 33.6% and 33.3%, respectively. No statistically significant difference between the 2 groups (?² = 0.051 with 1 degree of freedom; P = 0.82) was found. The predominantly male patient population, exclusion of mild OSA, lack of data about the level of control of the psychiatric symptoms and the sleep technicians not being blinded to the patients' psychiatric diagnoses were some of the limitations of this study. No significant difference existed in the prevalence of psychiatric disorders between patients intolerant to CPAP titration and those who tolerated CPAP for OSA. PMID:23138124

Manjunath, Skantha K; Sarva, Siva T; Yataco, Jose C; Murillo, Luis C; Avecillas, Jaime F; Freire, Amado X

2013-08-01

340

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

NASA Astrophysics Data System (ADS)

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.

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

1999-10-01

341

Statistical criteria for the identification of protein active sites using Theoretical Microscopic Titration Curves.  

PubMed

Theoretical Microscopic Titration Curves (THEMATICS) may be used to identify chemically important residues in active sites of enzymes by characteristic deviations from the normal, sigmoidal Henderson-Hasselbalch titration behavior. Clusters of such deviant residues in physical proximity constitute reliable predictors of the location of the active site. Originally the residues with deviant predicted behavior were identified by human observation of the computed titration curves. However, it is preferable to select the unusual residues by mathematically well-defined criteria, in order to reduce the chance of error, eliminate any possible biases, and substantially speed up the selection process. Here we present some simple statistical tests that constitute such selection criteria. The first derivatives of the predicted titration curves resemble distribution functions and are normalized. The moments of these first derivative functions are computed. It is shown that the third and fourth moments, measures of asymmetry and kurtosis, respectively, are good measures of the deviations from normal behavior. Results are presented for 44 different enzymes. Detailed results are given for 4 enzymes with 4 different types of chemistry: arginine kinase from Limulus polyphemus (horseshoe crab); beta-lactamase from Escherichia coli; glutamate racemase from Aquifex pyrophilus; and 3-isopropylmalate dehydrogenase from Thiobacillus ferrooxidans. The relationship between the statistical measures of nonsigmoidal behavior in the predicted titration curves and the catalytic activity of the residue is discussed. PMID:15739204

Ko, Jaeju; Murga, Leonel F; André, Pierrette; Yang, Huyuan; Ondrechen, Mary Jo; Williams, Ronald J; Agunwamba, Akochi; Budil, David E

2005-05-01

342

Uncertain Certi…cation Standards  

Microsoft Academic Search

When consumers are unsure of the exact standard that a quality certi…cate or label represents, they must infer the di¢ culty of the standard in part from observing which …rms adopt the label. Key results from the certi…cation and disclosure literatures are thereby altered. First, consumers are more suspicious of a label if a …rm with a bad reputation adopts

Rick Harbaugh; John W. Maxwell; Beatrice Roussillony

343

CATION EXCHANGE WITH MOLTEN SALTS  

Microsoft Academic Search

The applicability of cation exchange between synthetic zeolites, such as ; Linde Molecular Sieve 4A, and molten salts, such as monovalent nitrates, was ; studied. It was found that sodium and silver nitrate were occluded in the ; cavities of the zeolite framework, wfth approximately nine to ten molecules ; occuluded per unit cell of the zeolite. No occlusion was

M. Liquornik; Y. Marcus

1963-01-01

344

Cationic Polymerization of Cyclic Sulfides  

Microsoft Academic Search

The mechanism of the cationic polymerization of several thietanes and of propylene sulfide under the influence of triethyloxonium tetrafluoroborate in methylene chloride is described. The thietane polymerizations stop at limited conversions because of a termination reaction occurring between the reactive chain ends (cyclic sulfonium salts) and the sulfur atoms of the polymer chain. The maximum conversions obtained under identical conditions

E. J. Goethals; W. Drijvers; D. Van Ooteghem; A. M. Buyle

1973-01-01

345

Cation affinity numbers of Lewis bases  

PubMed Central

Summary Using selected theoretical methods the affinity of a large range of Lewis bases towards model cations has been quantified. The range of model cations includes the methyl cation as the smallest carbon-centered electrophile, the benzhydryl and trityl cations as models for electrophilic substrates encountered in Lewis base-catalyzed synthetic procedures, and the acetyl cation as a substrate model for acyl-transfer reactions. Affinities towards these cationic electrophiles are complemented by data for Lewis-base addition to Michael acceptors as prototypical neutral electrophiles. PMID:23019478

Lindner, Christoph; Tandon, Raman; Maryasin, Boris; Larionov, Evgeny

2012-01-01

346

Ionophore-based ion-exchange emulsions as novel class of complexometric titration reagents.  

PubMed

Complexometric titrations rely on a drastic change of the pM value at the equivalence point with a water soluble chelator forming typically 1?:?1 complexes of high stability. The available chemical toolbox of suitable chelating compounds is unfortunately limited because many promising complexing agents are not water soluble. We introduce here a novel class of complexometric titration reagents, a suspension of polymeric nanospheres whose hydrophobic core is doped with lipophilic ion-exchanger and a selective complexing agent (ionophore). The emulsified nanospheres behave on the basis of heterogeneous ion exchange equilibria where the initial counter ion of the ion-exchanger is readily displaced from the emulsion for the target ion that forms a stable complex in the nanosphere core. Two different examples are shown with Ca(2+) and Pb(2+) as target ions. The lack of protonatable groups on the calcium receptor allows one to perform Ca(2+) titration without pH control. PMID:25205536

Zhai, Jingying; Xie, Xiaojiang; Bakker, Eric

2014-10-28

347

Noncovalent cation-? interactions - their role in nature.  

PubMed

Non-covalent interactions play an extremely important role in organisms. The main non-covalent interactions in nature are: ion-ion interactions, dipole-dipole interactions, hydrogen bonds, and van der Waals interactions. A new kind of intermolecular interactions - cation-? interactions - is gaining increasing attention. These interactions occur between a cation and a ? system. The main contributors to cation-? interactions are electrostatic, polarization and, to a lesser extent, dispersion interactions. At first, cation-? interactions were studied in a gas phase, with metal cation-aromatic system complexes. The characteristics of these complexes are as follows: an increase of cation atomic number leads to a decrease of interaction energy, and an increase of cation charge leads to an increase of interaction energy. Aromatic amino acids bind with metal cations mainly through interactions with their main chain. Nevertheless, cation-? interaction with a hydrophobic side chain significantly enhances binding energy. In water solutions most cations preferentially interact with water molecules rather than aromatic systems. Cation-? interactions occur in environments with lower accessibility to a polar solvent. Cation-? interactions can have a stabilizing role on the secondary, tertiary and quaternary structure of proteins. These interactions play an important role in substrate or ligand binding sites in many proteins, which should be taken into consideration when the screening of effective inhibitors for these proteins is carried out. Cation-? interactions are abundant and play an important role in many biological processes. PMID:25380210

Fink, Krzysztof; Boraty?ski, Janusz

2014-01-01

348

Titration of free hydroxyl and strained siloxane sites on silicon dioxide with fluorescent probes.  

PubMed

A technique enabling the detection and quantification of low density sites on planar SiO2 surfaces is demonstrated. Fluorescent probes are used to titrate free hydroxyl and strained siloxane sites on the surface of amorphous SiO2 substrates in vacuum. The titration of free hydroxyl sites was performed to validate the method and to provide a reference for the measurement of the strained siloxane site density. Perylene derivatives with different functional groups are chemisorbed onto the surface sites, enabling in situ photoluminescence (PL) measurements of the bound fluorophores. An amine functional group is used to selectively titrate strained siloxane sites, while an alcohol group is used for the titration of free hydroxyl sites. Emission intensity was found to be nonlinear with coverage for bound fluorophore densities greater than 0.1 nm(-2), necessitating the removal of molecules from the surface into a solution to obtain accurate density measurements. For lower densities, the coverage of bound fluorophores can be estimated directly from in situ PL measurements. The measured areal densities of bound fluorophores after titrating free hydroxyl sites are in good agreement with literature values for the densities of such sites on high surface area silica. PL measurements of SiO2 surfaces titrated with an amine derivative of perylene indicate that strained siloxane sites exist for vacuum pretreatment temperatures of 300 °C and increase with increasing pretreatment temperature. Densities of strained siloxane sites on the silica surface are estimated at 0.004-0.02 nm(-2) for pretreatment temperatures of 300-700 °C, demonstrating the sensitivity of this technique. PMID:23978272

McCrate, Joseph M; Ekerdt, John G

2013-09-24

349

Kinetic catalytic determination of trace levels of iodide based on the oxidation of basic dyes with hydrogen peroxide monitored potentiometrically using simple PVC electrodes  

Microsoft Academic Search

Four sensitive catalytic potentiometric methods have been developed for trace levels determination of iodide based on its catalytic effects on the oxidation of four dyes: viz. variamine blue (VB), rhodamine B (RB), methylene blue (MB) and malachite green (MG), with H2O2 in H3PO4 medium at 25±0.5°C. The catalyzed reaction rates were estimated potentiometrically by monitoring the potential of the corresponding

Elmorsy Khaled; M. A. El-Ries; F. I. Zidane; S. A. Ibrahim; M. S. Abd-Elmonem

2011-01-01

350

A study of an extension of the frequency range applicable to analysis and titration  

E-print Network

for Titratioxx of Sodhxs ~xxMe and /pe'oohIOpio kOQp 9&vi ?ogoogoles s ~ i a a s o, ~ ~ N ~ XX, Table gXx Data fox' Titration of Sodinxx BFdroxxide ?nd ~bloxio kaid, 107, % Negaoyales, , . . . , ~. . . 36 XXX? Table XIXx Data Ac Titratioxx of Sodioxx Bfdroxx...???, ~ ?????, ??? ~ ?? w? + ~ ' Oraph IV) Absorption Curves ef gedtum gydrcndds and gydreehlorie heM? Long Here?? q? ~ ?????? ~ ? 33 Oxnph V, & Absorption Cucyee of Sodicne+@ioxQe and ~, ~hlorie AOM? Short Sere ? ? ~ ~ ~ ? ? ? ? ~ ~ ? Oreph VX& Titration Curve for tho...

Levine, Samuel W

2012-06-07

351

Monitoring of an RNA Multistep Folding Pathway by Isothermal Titration Calorimetry  

PubMed Central

Abstract Isothermal titration calorimetry was used to monitor the energetic landscape of a catalytic RNA, specifically that of the hepatitis delta virus ribozyme. Using mutants that isolated various tertiary interactions, the thermodynamic parameters of several ribozyme-substrate intermediates were determined. The results shed light on the impact of several tertiary interactions on the global structure of the ribozyme. In addition, the data indicate that the formation of the P1.1 pseudoknot is the limiting step of the molecular mechanism. Last, as illustrated here, isothermal titration calorimetry appears to be a method of choice for the elucidation of an RNA's folding pathway. PMID:19134473

Reymond, Cedric; Bisaillon, Martin; Perreault, Jean-Pierre

2009-01-01

352

Determination of submillimolar concentration of ferrate(VI) in alkaline solutions by amperometric titration  

Microsoft Academic Search

A new amperometric titration method was developed for quantitative determination of ferrate(VI) (FeVIO4\\u000a 2?) in the 7.06×10?5?5.73×10?3 M concentration range. Chromium(III) hydroxide solution was used as the titrant. The diffusion current (Id) had a linear\\u000a relationship with the concentration of ferrate(VI) and slopes were dependent on the concentration of NaOH. The amperometric\\u000a titration could detect a lower concentration of ferrate(VI)

Dmitriy A. Golovko; Virender K. Sharma; Olga. V. Pavlova; Elena. A. Belyanovskaya; Igor. D. Golovko; Victoria. I. Suprunovich; Radek Zboril

2011-01-01

353

Cationic Main Group Compounds as Water Compatible Small Anion Receptors  

E-print Network

]+ .............................................................................................. 11 9. Spectrophotometric acid-base titration for [17]+ (top) and the crystal structure of 17-OH (bottom) .......................................................................... 13 10. UV-vis titration data showing the absorbance change of a...]+ .................................. 48 40. Crystal structure of [49]+ ................................................................................ 49 41. Equilibrium equation for pKR+ studies ........................................................... 51 42. Titration...

Leamer, Lauren Anne

2013-05-06

354

The integration of ion potentiometric measurements with chemical, structural, and morphological analysis to follow mineralization reactions in solution.  

PubMed

The solution crystallization of biominerals like calcium carbonate or calcium phosphate is a process that requires a high level of control over reaction kinetics. Ion potentiometric measurements are a way to follow and control reaction kinetics by measuring changes in pH and ion concentration, also allowing quantification of chemical compositions and solubility characteristics. By combining these measurements with various analysis techniques, one can acquire a complete spectrum of chemical, structural, and morphological data, even on metastable precursors. Therefore, in this chapter, the use of potentiometric measurements in standard solution crystallization experiments is described and the integration of these measurements with microscopy, spectroscopic and scattering analyses in such a way that the control over the reaction kinetics is maintained. PMID:24188761

Habraken, Wouter J E M

2013-01-01

355

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

PubMed

The most successful binding kinetics analysis systems at this moment include surface plasmon resonance (SPR), quartz microcrystal balance (QMB) and surface acoustic wave (SAW). Although these are powerful methods, they generally are complex, expensive and require the use of monolayers. Here, we report on potentiometric sensors as an inexpensive and simple alternative to do binding kinetics analysis between small molecules in solution and biomolecules (covalently) attached in a biopolymer sensor coating layer. As an example, dopamine and an anti-dopamine aptamer were used as the small molecule and the biomolecule respectively. Binding between both follows a Langmuir adsorption type model and creates a surface potential. The system operates in Flow Injection Analysis mode (FIA). Besides being an interesting new binding kinetics tool, the approach allows systematic design of potentiometric biosensors (in the present study a dopamine sensor), and gives new insights into the functioning of ion-selective electrodes (ISE's). PMID:24325980

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

2014-04-15

356

Comparison of different methods for calculation of the stoichiometric dissociation constant of acetic acid from results of potentiometric titrations at 298.15 K in aqueous sodium or potassium chloride solutions  

Microsoft Academic Search

Single-ion activity coefficient equations were determined for the calculation of the molality-scale dissociation constants, Km, for acetic acid in aqueous NaCl or KCl solutions at 298.15 K. The salt alone determines the ionic strength, Im, of the solutions considered in this study. The activity coefficient equations are of the Hückel type, and Km can be calculated by those for a

Jaakko I. Partanen; Pekka M. Juusola

2000-01-01

357

DNA Bending by Small, Mobile Multivalent Cations  

Microsoft Academic Search

We propose a purely electrostatic mechanism by which small, mobile, multivalent cations can induce DNA bending. A multivalent cation binds at the entrance to the B-DNA major groove, between the two phosphate strands, electrostatically repelling sodium counterions from the neighboring phosphates. The unscreened phosphates on both strands are strongly attracted to the groove-bound cation. This leads to groove closure, accompanied

Ioulia Rouzina; Victor A. Bloomfield

1998-01-01

358

Collisionally Activated Dissociation of 1-Benzyloxypyridinium Cations.  

National Technical Information Service (NTIS)

Eighteen pyridine-ring substituted N-benzyloxpyridinium cations all dissociate by two alternative pathways to give (A) a cation C7H7(+) and the substituted pyridine 1-oxide, and (B) a cation C7H7O(+) and the substituted pyridine. Appearance potentials (E(...

A. R. Katritzky, Z. Dega-Szafran, C. H. Watson, J. R. Eyler

1989-01-01

359

POTENTIOMETRIC DISCRIMINATION OF FLUORO- AND CHLOROPHENOL ISOMERS BASED ON THE HOST FUNCTIONALITY OF CALIX[4]PYRROLE AT LIQUID MEMBRANE SURFACES  

Microsoft Academic Search

This work presents a study on the generation of an “anionic” potentiometric response of a liquid polymeric membrane based on calix[4]pyrrole towards neutral chloro- and fluorophenol isomers. The results show that a calix[4]pyrrole membrane is able to recognize chloro and fluoro derivatives of phenols, and discriminate between ortho-, meta-, and para-isomers of chlorophenol. The mechanism of molecular recognition relies on

Tomasz Piotrowski; Hanna Radecka; Jerzy Radecki; Stefaan Depraetere; Wim Dehaen

2002-01-01

360

A Solid Fe2O3 Based Carbon-Epoxy Electrode For Potentiometric Measurements of pH  

Microsoft Academic Search

A solid of Fe2O3 based carbon-epoxy composite electrode was investigated for use as a potentiometric pH sensor. The electrode was constructed with a mixture of sulfated iron(III) oxide, carbon power and epoxy resin that was deposited directly onto a glass tube. The effect of composition (Fe2O3, carbon and epoxy resin) on the electrode response and its calibration curve (mV\\/pH) were

M. F. S. Teixeira; L. A. Ramos; E. A. Neves; E. T. G. Cavalheiro

2002-01-01

361

A Solid Fe 2 O 3 Based Carbon–Epoxy Electrode for Potentiometric Measurements of pH  

Microsoft Academic Search

A solid Fe2O3 based carbon-epoxy composite electrode was investigated for use as a potentiometric pH sensor. The electrode was constructed using a mixture of sulfated iron(III) oxide, carbon power, and epoxy resin, which was deposited directly onto a glass tube. The effect of composition (Fe2O3?, carbon and epoxy resin) on the electrode response and its calibration curve (mV\\/pH) were investigated.

M. F. S. Teixeira; L. A. Ramos; E. A. Neves; E. T. G. Cavalheiro

2002-01-01

362

Non-Surface Activity of Cationic Amphiphilic Diblock Copolymers  

NASA Astrophysics Data System (ADS)

Cationic amphiphilic diblock copolymers containing quaternized poly (2-vinylpyridine) chain as a hydrophilic segment (PIp-b-PNMe2VP) were synthesized by living anionic polymerization. By IR measurement, we confirmed the quaternization of the polymer (PIp-b-PNMe2VP), and determined the degree of quaternization by conductometric titration. The surface tension experiment showed that the polymers are non-surface active in nature. The foam formation of the polymer solutions was also investigated with or without added salt. Almost no foam formation behavior was observed without added salt, while a little foam was observed in the presence of 1M NaCl. The critical micelle concentration (cmc) of the diblock copolymers with 3 different chain lengths was measured by the static light scattering method. The cmc values obtained in this study were much lower than the values obtained for anionic non-surface active diblock polymers studied previously. The hydrodynamic radii of the polymer micelle increased slightly in the presence of 1 M NaCl. The transmission electron microscopic images revealed spherical micelles in pure water. In the presence of salt, the cmc values increased as was the case for anionic polymers, which is unlike conventional surfactant systems but consistent with non-surface active anionic block copolymers. The microviscosity of the micelle core was evaluated using Coumarin-153 as a fluorescent anisotropy probe using steady-sate fluorescence depolarization. Non-surface activity has been proved to be universal for ionic amphiphilic block copolymers both for anionic and cationic. Hence, the origin of non-surface activity is not the charged state of water surface itself, but should be an image charge repulsion at the air/water interface.

Ranjan Nayak, Rati; Yamada, Tasuku; Matsuoka, Hideki

2011-09-01

363

?-Cationic phosphines: synthesis and applications.  

PubMed

In coordination chemistry, typical ancillary ligands are anionic or neutral species. Cationic ones are exceptions and, when used, the positively charged groups are normally attached to the periphery and not close to the donating atom. However, this concept article highlights a series of recent experimental, as well as theoretical results, suggesting that the utility in catalysis of cationic phosphines with no spacer between the phosphorus atom and the positively charged group(s) has been largely overlooked. In fact, a growing number of studies indicate that, because of their specific architecture, these cationic ligands depict excellent ?-acceptor character that can exceed that of phosphites or polyfluorinated phosphines. This property has been used to increase the Lewis acidity of the metals they coordinate. Specifically, new extreme ?-acid catalysts, mainly based on Pt(II) and Au(I) , have been recently prepared and their superior performance demonstrated along several mechanistically distinct transformations. In this concept article the current state of the art is critically assessed and possible future directions of the topic discussed. PMID:24890133

Alcarazo, Manuel

2014-06-23

364

Gaseous protein cations are amphoteric  

SciTech Connect

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.

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

1997-02-19

365

A new construction for a potentiometric, enantioselective membrane electrode--its utilization to the S-captopril assay.  

PubMed

A novel potentiometric, enantioselective membrane electrode based on graphite paste (graphite powder and paraffin oil) has been constructed. The graphite paste is impregnated with 2-hydroxy-3-trimethylammoniopropyl-beta-cyclodextrin (as chloride salt) solution, 10(-3) mol l(-1). The potentiometric, enantioselective membrane electrode can be used reliable for S-captopril assay as raw material and from Novocaptopril tablets, using a chronopotentiometry (zero current) technique, in the 10(-6)-10(-2) mol l(-1) concentration range (detection limit 2 x 10(-7) mol l(-1)), with an average recovery of 99.99% (RSD=0.05%). The enantioselectivity was determined over R-captopril and D-proline. The response characteristics of the enantioselective, potentiometric membrane electrode were determined also for R-captopril. It was shown that only L-proline is the main interfering compound. The surface of the electrode can be regenerated by simply polishing, obtaining fresh surface ready to be used in a new assay. PMID:18967558

Stefan, R I; van Staden, J K; Aboul-Enein, H Y

1999-05-01

366

Potentiometric and solubility studies of association quotients of aluminum malonate complexation in NaCl media to 75 C  

SciTech Connect

A potentiometric method was used to determine the formation quotients for aluminum-malonate (Al(Ma){sub y}{sup 3{minus}2y}, Ma = CH{sub 2}(CO{sub 2}){sub 2}{sup 2{minus}}) complexes from 5 to 75 C at four ionic strengths from 0.1 to 1.0 molal in aqueous NaCl media. Two mononuclear aluminum-malonate species, Al(Ma){sup +} and Al(Ma){sub 2}{sup {minus}}, were identified, and the formation quotients for these species were modeled by empirical equations to describe their temperature and ionic strength dependencies. Differentiation of the two empirical equations with respect to temperature provided thermodynamic quantities for the Al-malonate complexes. The thermodynamic quantities obtained for Al(Ma){sup +} and for Al(Ma){sub 2}{sup {minus}} indicate that Al(Ma){sup +}, a chelate complex, is much more stable than the equivalent monodentate Al-diacetate complex (Al(Ac){sub 2}{sup +}). A solubility study, which was undertaken to verify the 50 C potentiometric data, was performed by reacting powdered gibbsite (Al(OH){sub 3}) with malonic acid solutions at 0.1 molal ionic strength in aqueous NaCl media. The results of the solubility study are in excellent agreement with the potentiometric data.

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; Palmer, D.A.; Wesolowski, D.J. [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.] [Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.

1998-07-01

367

TITRATION OF A BRUCELLA PROTEIN ALLERGEN IN SHEEP SENSITIZED WITH BRUCELLA MELITENSIS  

E-print Network

TITRATION OF A BRUCELLA PROTEIN ALLERGEN IN SHEEP SENSITIZED WITH BRUCELLA MELITENSIS Lois M. JONES. INTRODUCTION A protein allergen extracted from a rough strain of B. melitensis was a highly potent agent in eliciting delayed hypersensitivity reactions in guinea pigs (JONES, DIAZ and TAYLOR, ig73). This allergen

Paris-Sud XI, Université de

368

An improved telemedicine system for remote titration and optimization of Home Mechanical Ventilation  

Microsoft Academic Search

Home Mechanical Ventilation is applied to patients with different chronic respiratory diseases and, in order to be effective, it requires accurate individual titration. Nowadays this can be obtained only in the hospital during day or night visits, and this is associated with long waiting lists and high costs. The aim of this work was to realize and test a simple

Leonardo Govoni; R. Farre?; Antonio Pedotti; Josep M. Montserrat; Raffaele L. Dellaca

2010-01-01

369

Titrating Steroids on Exhaled Nitric Oxide in Children with Asthma A Randomized Controlled Trial  

Microsoft Academic Search

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,

Marielle W. Pijnenburg; E. Marije Bakker; Wim C. Hop; Johan C. De Jongste

370

A spectroelectrochemical cell designed for low temperature electron paramagnetic resonance titration of oxygen-sensitive proteins.  

PubMed

In this paper we describe an anaerobic titrator made virtually from glass with a small amount of high vacuum epoxy mounted directly to a quartz EPR tube. A complete titration may be carried out with as little as 600 microliters of sample. This cell features the anaerobic manipulation of an electrochemically poised solution from an electrochemical pouch to an EPR tube. The cell uses a gold foil working electrode and Ag/AgCl reference and counter electrodes. The reference and counter electrodes are isolated from the sample by leached Vycor glass. In the work reported here, we used this cell to determine the equilibrium redox potential of methyl viologen in an EPR titration. With methyl viologen as an indicator we found that the cell has a residual oxygen level of 1.5 microM with a leak rate of 0.005 nmol/min. After moving the solution into the EPR tube, freezing, performing EPR, and thawing, the potential of the methyl viologen solution drifted only 2 mV. During the titration, the poised potentials were stable, drifting only 1 mV/min. Formal potentials as low as -630 mV in a vitamin B12-type protein have been determined with this cell (S. R. Harder, W.-P. Lu, B. A. Feinberg, and S. W. Ragsdale (1989) Biochemistry, in press). PMID:2554761

Harder, S R; Feinberg, B A; Ragsdale, S W

1989-09-01

371

Photoelectric end-point determination in the titration of fluorides with thorium nitrate  

Microsoft Academic Search

A procedure used for the determination of fluorides in plant tissue and in air is described. A photoelectric filter photometer functioning as a comparator is used for the determination of the end point in the titration of fluorides (F) with thorium nitrate (Th(NOâ)â) in the presence of sodium alizarinsulfonate. It is a balance type instrument consisting of a nearly monochromatic

R. Mavrodineanu; J. Gwirtsman

2009-01-01

372

Coulometric Titration of Thiocyanate, Mercaptoacetic Acid, and ?-Mercaptopropionic Acid with Electrogenerated Hypobromite  

Microsoft Academic Search

Several sulfur containing ligands have been determined by coulometric titration using biamperometric end point detection. Satisfactory results were obtained for the direct determination of thiocyanate, mercaptoacetic acid and ?-mercaptopropionic acid. Silver has been determined by an indirect method involving the determination of excess precipitant.

R. J. Palma; H. K. L. Gupta; D. F. Boltz

1971-01-01

373

Titration of fluoride with lanthanum chloride applying the biamperometric and the bipotentiometric end-point detection  

Microsoft Academic Search

Die Möglichkeiten der biamperometrischen und der bipotentiometrischen Endpunktbestimmung bei der Kaliumfluoridtitration mit Lanthanchlorid wurden unter Anwendung von Antimon-, Wismut-, Zinn- und Chinhydronelektrodenpaaren (Metallphase Platinum, Palladium und Gold) untersucht. In ungepufferten Fluoridlösungen mit 75 % Äthanolgehalt am Titrationsendpunkt wurden 5,72 mg Kaliumfluorid mit einer mittleren Abweichung von <0,8% bestimmt. Die erhaltenen Ergebnisse stimmten gut mit denen von potentiometrischer Titration überein.

Ferenc F. Gaál; Ljiljana S. Jovanovi?; Velimir D. Cani?

1976-01-01

374

Water Research 39 (2005) 579588 A high-resolution titrator: a new approach to studying  

E-print Network

Water Research 39 (2005) 579­588 A high-resolution titrator: a new approach to studying binding groups for sorption and to determine their affinities by considering their partial or total ionization of protons and the sorption capacities of the selected bioorganic matters were established. Sorption of lead

Volesky, Bohumil

375

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

ERIC Educational Resources Information Center

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…

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

2011-01-01

376

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

E-print Network

commonly used analytical methods: ion-selective electrodes, anodic strip- ping voltammetry, fluorescence using ion-selective electrodes and fixed-potential ampero- metry. The results of these comparisons selective electrode and fluorescence quenching data and Waite and Morel (3) compared fulvic acid titrations

Morel, François M. M.

377

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

378

Determination of the Iodine Value of Selected Oils: An Experiment Combining FTIR Spectroscopy with Iodometric Titrations  

Microsoft Academic Search

An experiment has been developed that combines the FTIR analysis of oils and fats with an iodometric titration. While it is most appropriate for a sophomore or junior laboratory for majors, it also makes a suitable group project or demonstration for nonscience majors. Integration of the experiment into an upper-level biochemistry laboratory is described.

E. Eugene Gooch

2001-01-01

379

Iodometric titration for determining the oxygen content of samples doped with Fe and Co  

Microsoft Academic Search

Double iodometric titration is a method developed for high-Tc superconductivity. It has been widely used to determine the effective oxidation of copper and to figure out the oxygen content in a sample in the past years. If a sample is doped with some metals like iron and cobalt, these metal ions can interfere in experiment results. This is a major

W. M. Chen; W. Hong; J. F. Geng; X. S. Wu; W. Ji; L. Y. Li; L. Qui; X. Jin

1996-01-01

380

An accurate method of iodometric titration for determining oxygen content of superconducting cuprates  

Microsoft Academic Search

There are three problems existing in double iodometric titration. First, the calculating equation is too rough to obtain accurate results. Second, an error comes from iodine adsorbed by CuI. Third, when a sample is doped with iron-like elements, iron interferes with this method. The above problems were solved as following. We adopted a new equation, which may modify copper valence

W. M. Chen; N. L. Chen; C. C. Lam; J. Chen; X. S. Wu; X. Zhang; D. B. Chen; X. Jin

1997-01-01

381

Technical Note: How long can seawater oxygen samples be stored before titration?  

NASA Astrophysics Data System (ADS)

The concentration of dissolved oxygen in seawater is routinely measured using a standardized titration method that involves analysis shortly after the water sample has been collected. However, none of the existing procedural documents are specific about how soon after collection the titration has to be done. Here, we report on a small number of samples where duplicates were collected and one batch was titrated within days after collection, while the other batch was stored for several weeks before titration. In addition, for a subset of the samples a third batch was taken that was stored like the others but with a particular chemical already added before storage. Comparison between the batches confirms that there is no significant difference between the ones that were stored and the ones that were analyzed sooner, indicating that a month-long storage period is acceptable. The implication of this is that such oxygen samples do not necessarily have to be analyzed while still on the ship; instead, it is possible to transport them ashore for analysis there.

Lankhorst, M.; Chavez, G.; Nam, S. H.; Send, U.

2014-10-01

382

COMPLEXOMETRIC TITRATION OF YTTRIUM AND THE LANTHANONS. I. A COMPARISON OF DIRECT METHODS  

Microsoft Academic Search

A comparison was made of a number of direct complexometric titrations ; previously published ior the determination of yttrium and the lanthanons. ; Working and optimum pH ranges were obtained for what are considered to be the ; best indicators, Alizarin Red S screened with Methylene Blue, Eriochrome Black T, ; Copper-Naphthyl Azoxine, and Xylenol Orange. The precision and accuracy

S. J. Lyle

1963-01-01

383

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

ERIC Educational Resources Information Center

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…

Consumer Dynamics Inc., Rockville, MD.

384

proteinsSTRUCTURE O FUNCTION O BIOINFORMATICS Titration_DB: Storage and analysis of  

E-print Network

Science, Centre for Synthesis and Chemical Biology, UCD Conway Institute, University College Dublin properties of its folded versus unfolded states. The ionization of an isolated titratable group in a protein and Chemical Biology, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland. E

McIntosh, Lawrence P.

385

Determination of nitric acid in highly radioactive solutions by the method of coulometric titration  

Microsoft Academic Search

A procedure, a cell, and an electronic block have been developed for a long-distance determination of nitric acid in highly radioactive industrial solutions by coulometric titration under hot chamber conditions. A solution of a mixture of ammonium and potassium oxalates was used for the background and anoide electrolytes. This solution prevents the hydrolysis of the metal ions and appreciably decreases

V. S. Gromov; A. Ya. Kuperman; Yu. A. Smirnov

1988-01-01

386

A LABORATORY REFERENCE VACCINE TO TITRATE IMMUNOGENIC ACTIVITY OF ANTIBRUCELLA VACCINES IN MICE  

E-print Network

A LABORATORY REFERENCE VACCINE TO TITRATE IMMUNOGENIC ACTIVITY OF ANTIBRUCELLA VACCINES IN MICE Reproduction, Nouzilly, 37380 Monnaie, France Résumé UN VACCIN Ã?TALON POUR TITRER L'ACTIVITÃ? IMMUNOGÃ?NIQUE DES VACCINS ANTI-BRU- CELLA SUR LA SOURIS. ― Le nombre de Brucella dans la rate de souris, 15 jours

Boyer, Edmond

387

Prednisone for chronic active liver disease: dose titration, standard dose, and combination with azathioprine compared  

Microsoft Academic Search

Among 120 consecutive patients with chronic active liver disease (CALD) randomized to different treatments, those receiving maintenance doses of prednisone 20 mg daily (Pred), prednisone in doses given on alternate days and titrated to secure resolution of clinical and biochemical abnormalities (Pred-Titrad), or a combination of prednisone 10 mg and azathioprine 50 mg daily (Comb) survived and underwent resolution of

W H Summerskill; M G Korman; H V Ammon; A H Baggenstoss

1975-01-01

388

Titration of a Solid Acid Monitored by X-Ray Diffraction  

ERIC Educational Resources Information Center

An experiment is described to introduce students to an important class of solid-state reactions while reinforcing concepts of titration by using a pH meter and a powder X-ray diffractometer. The experiment was successful in teaching students the abstract concepts of solid-state structure and diffraction by applying the diffraction concepts learned…

Dungey, Keenan E.; Epstein, Paul

2007-01-01

389

USE OF 1,3-DIMETHYLVIOLURIC ACID IN SPECTROPHOTOMETRIC TITRATIONS OF ALKALI AND ALKALINE EARTH SALTS  

Microsoft Academic Search

A spectrophotometric study was made of the lithium, sodium, potassium, ; rubidium, cesium, beryllium, and magnesium salts of 1,3-dimethyl-5-; isonitrosobarbituric acid (1,3-dimethylvioluric acid, DMVA). The applicability ; of DMVA for the spectrophotometric titration of alkali and alkaline earth salts ; in aqueous solution was investigated. These metals were determined with an ; accuracy that ranged from 1 to 10 parts

M. E. Taylor; R. J. Robinson

1962-01-01

390

Potentiometric surface of the intermediate aquifer system, west- central Florida, May 1987  

USGS Publications Warehouse

The intermediate aquifer system within the Southwest Florida Water Management District underlies a 5,000 sq mi area of De Soto, Sarasota, Hardee, Manatee, and parts of Charlotte, Hillsborough, Highlands, and Polk Counties. The intermediate aquifer system occurs between the overlying surficial aquifer system and the underlying Floridan aquifer system, and consists of layers of sand, shell, clay, marl, limestone, and dolom of the Tamiami, Hawthorn, and Tampa Formations of late Tertiary age. The intermediate aquifer system contains one or more water-bearing units separated by discontinuous confining units. This aquifer system is the principal source of potable water in the southwestern part of the study area and is widely used as a source of water in other parts where wells are open to the intermediate aquifer system or to both the intermediate and Floridan aquifer systems. Yields of individual wells open to the intermediate aquifer system range from a few gallons to several hundred gallons per minute. The volume of water withdrawn from the intermediate aquifer system is considerably less than that withdrawn from the Floridan aquifer system in the study area. The surface was mapped by determining the altitude of water levels in a network of wells and is represented on maps by contours that connect points of equal altitude. The compos potentiometric surface of all water-bearing units within the intermediate aquifer system is shown. In areas where multiple aquifers exist, wells open to all aquifers were selected for water level measurements whenever possible. In the southwestern and lower coastal region of the study area, two aquifers and confining units are described for the intermediate aquifer system: the Tamiami-upper Hawthorn aquifer and the underlying lower Hawthorn-upper Tampa aquifer. The potentiometric surface of the Tamiami-upper Hawthorn aquifer is also shown. Water levels are from wells drilled and open exclusively to that aquifer. The exact boundary for the Tamiami-upper Hawthorn aquifer is undetermined because of limd geohydrologic data available from wells. (Lantz-PTT)

Lewelling, B. R.

1988-01-01

391

Hydrogen-ion titrations of amino acids and proteins in solutions containing concentrated electrolyte  

SciTech Connect

This report describes a first attempt to quantify the net charge as a function of solution pH for lysozyme and {alpha}-chymotrypsin at 0.1 M, 1.0 M and 3.0 M ionic strength, (IS). The calculations are based on the residue (titratable group) pK{sub a}`s in the amino-acid sequence of the protein. To determine these pK{sub a}`s, a simple theory was used which assumes that the pK{sub a}`s are independent from each other in the protein and are equal to their pK{sub a} values in free amino-acid solution (Independent-Site Theory, IST). Residue pK{sub a}`s were obtained from amino-acid hydrogen-ion titrations at three different KCl concentrations corresponding to 0.1M, 1.0M and 3.0M ionic strength. After construction of a suitable apparatus, the experimental procedure and data reduction were computerized to perform a large number of titrations. Most measured pK{sub a}`s showed high reproducibility (the difference of pK{sub a} values observed between two experiments was less than 0.05). For IS = 0.1M, observed pK{sub a}`s agreed with literature values to within a few hundredths of a pH unit. Furthermore, the ionic-strength dependence of the pK{sub a}`s followed the trends reported in the literature, viz. pK{sub a} values decrease with increasing ionic strength until they reach a minimum at about IS = 0.5M. At still higher IS, pK{sub a}`s increase as the ionic strength rises to 3M. The known pK{sub a}`s of all titratable groups in a protein were used with the IST to give a first approximation of how the protein net charge varies with pH at high ionic strength. A comparison of the titration curves based on the IST with experimental lysozyme and {alpha}-chymotrypsin titration data indicates acceptable agreement at IS = 0.1M. However, comparison of measured and calculated titration curves at IS = 1M and IS = 3M indicates only quantitative agreement.

Fergg, F. [Technische Universitaet Muenchen (Germany); Kuehner, D.E.; Blanch, H.W.; Prausnitz, J.M. [Lawrence Berkeley Lab., CA (United States)

1994-12-01

392

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

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)

Smith, Robert L.; Popham, Ronald E.

1983-01-01

393

On-line titration method for monitoring buffer capacity and total volatile fatty acid levels in anaerobic digesters.  

PubMed

The construction and use of an automatic on-line titration unit for routine or event- initiated monitoring of alkalinity, buffer capacity, and volatile fatty acid (VFA) levels is presented. Under computer control a sample of digester liquor is pumped into the titration vessel and weighed. A sequence of titration, sparging, and back-titration operations are then initiated during which the pH and weight are recorded continuously and a titration curve constructed. From the curve, estimates of the alkalinity, buffer capacity to any desired pH endpoint, and total VFA levels are computed. The data is stored to disk and output as hard copy together with the titration curve itself. Monitoring and control of the titration apparatus is effected by a microcomputer via two analog input lines and eight digital output lines, respectively. The system is suitable for downloading to a small, inexpensive dedicated microprocessor-based system. The apparatus is constructed from standard and widely available equipment and the titration sequence, being under software control, is fully adaptable to particular requirements. The use of this facility in the on-line monitoring, control and optimization of the anaerobic digestion process is discussed. PMID:18587953

Powell, G E; Archer, D B

1989-01-25

394

Cationic micellar nanoparticles for DNA and doxorubicin co-delivery.  

PubMed

Cationic micellar nanoparticles for chemotherapeutic drugs and therapeutic gene co-delivery were prepared based on a poly-(N-?-carbobenzyloxy-l-lysine) (PZLL) and dendritic polyamidoamine (PAMAM) block copolymer (PZLL-D3). PZLL-D3 was synthesized by a copper-catalyzed azide alkyne cyclization (click) reaction between ?-alkyne-PZLL and azide focal point PAMAM dendrons. Its structure was characterized by (1)H NMR and FTIR, and its buffering capability was determined by acid-base titration. MTT, agarose gel electrophoresis and flow cytometry studies showed that PZLL-D3 revealed low in vitro cytotoxicity, strong pDNA condensation ability, protection of pDNA against deoxyribonuclease I degradation and high gene transfection efficiency in 293T and HeLa cells. In addition, the micellar nanoparticles delivered pDNA and anticancer drug doxorubicin (DOX) simultaneously and efficiently to tumor cells, and the DOX loaded nanoparticles showed sustained in vitro release at pH=7.4 and 5.8. PMID:25280725

Lin, Jian-Tao; Zou, Ying; Wang, Chao; Zhong, Yue-Chun; Zhao, Yi; Zhu, Hui-Er; Wang, Guan-Hai; Zhang, Li-Ming; Zheng, Xue-Bao

2014-11-01

395

A Novel Potentiometric Sensor for Determination of Neurotoxin ?-N-Oxalyl-L-?, ?-Diaminopropionic Acid  

PubMed Central

A novel potentiometric sensor based on ionophore (Cd(NH2CH2CH2OCH2CH2OCH2CH2NH2)Ag3(CN)5) for the determination of ?-N-oxalyl-l-?, ?-diaminopropionic acid (ODAP) is developed. The ODAP-selective membrane sensor demonstrates high sensitivity and short response time. The detection limit of the ODAP-selective membrane sensor is about 2 × 10?6?mol?L-1 and the response time is shorter than 6?s. The linear dynamic range of the ODAP-selective membrane sensor is between ODAP concentrations of 1.0 × 10?2 and 1 × 10?6?mol?L-1. The ODAP-selective membrane sensor exhibits good operational stability for at least one week in dry conditions at 4–6°C. It has a reproducible and stable response during continuous work for at least 10?h with a relative standard deviation of 0.28% (n = 18). PMID:24971325

Isildak, Omer; Saymaz, Furkan; Karadag, Ahmet; Korkmaz, Nesrin Okumus; Attar, Azade

2014-01-01

396

Incorporating ?-Cyclodextrin with ZnO Nanorods: A Potentiometric Strategy for Selectivity and Detection of Dopamine  

PubMed Central

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

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

2014-01-01

397

Determination of l-carnitine using enantioselective, potentiometric membrane electrodes based on macrocyclic antibiotics.  

PubMed

In order to determine the enantiopurity of l-carnitine three enantioselective, potentiometric membrane electrodes were proposed for the assay of l-carnitine. The electrodes were designed using macrocyclic glycopeptide antibiotics-vancomycin and teicoplanin. Acetonitrile was added to the teicoplanine to design a modified teicoplanine based electrode. The linear concentration ranges for the proposed enantioselective membrane electrodes were 10(-4) to 10(-2)moll(-1) for electrodes based on vancomycin and teicoplanin and 10(-5) to 10(-2)moll(-1) for electrode based on teicoplanin modified with acetonitrile. The slopes of the electrodes were 56.5mV per pl-carnitine; 54.5mV per pl-carnitine and 58.3mV per pl-carnitine for vancomycin-, teicoplanin- and teicoplanin modified with acetonitrile-based electrodes, respectively. The enantioselectivity was determined over d-carnitine. The proposed electrodes could be employed reliably for the assay of l-carnitine raw material and its pharmaceutical formulation, Carnilean((R)) capsules. The surfaces of the electrodes are stable and easily renewable by polishing on alumina paper. PMID:18969462

Rat'ko, Alexander A; Stefan, Raluca-Ioana; van Staden, Jacobus Koos F; Aboul-Enein, Hassan Y

2004-06-17

398

A Potentiometric Formaldehyde Biosensor Based on Immobilization of Alcohol Oxidase on Acryloxysuccinimide-modified Acrylic Microspheres  

PubMed Central

A new alcohol oxidase (AOX) enzyme-based formaldehyde biosensor based on acrylic microspheres has been developed. Hydrophobic poly(n-butyl acrylate-N-acryloxy-succinimide) [poly(nBA-NAS)] microspheres, an enzyme immobilization matrix, was synthesized using photopolymerization in an emulsion form. AOX-poly(nBA-NAS) microspheres were deposited on a pH transducer made from a layer of photocured and self-plasticized polyacrylate membrane with an entrapped pH ionophore coated on a Ag/AgCl screen printed electrode (SPE). Oxidation of formaldehyde by the immobilized AOX resulted in the production of protons, which can be determined via the pH transducer. Effects of buffer concentrations, pH and different amount of immobilization matrix towards the biosensor’s analytical performance were investigated. The formaldehyde biosensor exhibited a dynamic linear response range to formaldehyde from 0.3–316.2 mM and a sensitivity of 59.41 ± 0.66 mV/decade (R2 = 0.9776, n = 3). The lower detection limit of the biosensor was 0.3 mM, while reproducibility and repeatability were 3.16% RSD (relative standard deviation) and 1.11% RSD, respectively (n = 3). The use of acrylic microspheres in the potentiometric formaldehyde biosensor improved the biosensor’s performance in terms of response time, linear response range and long term stability when compared with thick film immobilization methods. PMID:22163450

Ling, Yew Pei; Heng, Lee Yook

2010-01-01

399

Potentiometric surface and water quality in the Principal Aquifer, Mississippian Plateaus region, Kentucky  

USGS Publications Warehouse

The Mississippian Plateaus region is the outcrop area of rocks of Mississippian age which extends as a broad arcuate band around the Western Coal Field in westcentral Kentucky. Much of the area is characterized by plains of low relief containing numerous sinkholes, subsurface drainage, and a low density of surface streams. The principal aquifer consists of a thick sequence of limestones extending downward stratigraphically from the base of the Chesterian Series to the black shales at the top of the Devonian rocks. Well yields range from several gallons per minute to as much as 500 gallons per minute in some karst areas where secondary openings are well developed. The potentiometric map indicates that ground-water movement generally conforms to the surface drainage pattern. The actual direction of movement varies from river basin to river basin. Most water from the principal aquifer is a calcium magnesium bicarbonate type and is generally good relative to current drinking water standards. The lower St Louis Limestone, in places, yields a calcium magnesium sulfate water that is corrosive and has a strong hydrogen sulfide odor. The karst areas of the principal aquifer are vulnerable to contamination because of the well-developed subsurface drainage. Urban areas, industries, and agriculture are sources of contaminants that can be easily flushed into the ground-water system. (USGS)

Plebuch, R.O.; Faust, R.J.; Townsend, M.A.

1985-01-01

400

A potentiometric formaldehyde biosensor based on immobilization of alcohol oxidase on acryloxysuccinimide-modified acrylic microspheres.  

PubMed

A new alcohol oxidase (AOX) enzyme-based formaldehyde biosensor based on acrylic microspheres has been developed. Hydrophobic poly(n-butyl acrylate-N-acryloxy-succinimide) [poly(nBA-NAS)] microspheres, an enzyme immobilization matrix, was synthesized using photopolymerization in an emulsion form. AOX-poly(nBA-NAS) microspheres were deposited on a pH transducer made from a layer of photocured and self-plasticized polyacrylate membrane with an entrapped pH ionophore coated on a Ag/AgCl screen printed electrode (SPE). Oxidation of formaldehyde by the immobilized AOX resulted in the production of protons, which can be determined via the pH transducer. Effects of buffer concentrations, pH and different amount of immobilization matrix towards the biosensor's analytical performance were investigated. The formaldehyde biosensor exhibited a dynamic linear response range to formaldehyde from 0.3-316.2 mM and a sensitivity of 59.41 ± 0.66 mV/decade (R(2) = 0.9776, n = 3). The lower detection limit of the biosensor was 0.3 mM, while reproducibility and repeatability were 3.16% RSD (relative standard deviation) and 1.11% RSD, respectively (n = 3). The use of acrylic microspheres in the potentiometric formaldehyde biosensor improved the biosensor's performance in terms of response time, linear response range and long term stability when compared with thick film immobilization methods. PMID:22163450

Ling, Yew Pei; Heng, Lee Yook

2010-01-01

401

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

PubMed

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

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

2013-11-01

402

On the selective adsorption of cations in the cell wall of the green alga Valonia utricularis  

NASA Astrophysics Data System (ADS)

The selective adsorption of the cations Na+, K+, Mg++ and Ca++ by the cell wall of the Mediterranean alga Valonia utricularis (Siphonocladales, Chlorophyceae) from sea water of 40 %. S was investigated by extraction of cell-wall preparations, eluted before in 1.1 mol methanol (adjusted to pH 8) with 0.1 n formic acid in a Soxhlet apparatus. Na+ and K+ were determined by flame photometry, Mg++ and Ca++ by complexometric titration with EDTA. From calculation of the dry weight:fresh weight ratios and the chloride determinations in the eluates, the Donnan free-space fraction of the total cell-wall volume was calculated to about 35 %, and the analytical results of the cation concentrations in the extracts expressed as ?Val cm-3 DFS. This calculation is based on the assumption that the acidic groups of the noncellulosic matrix material, carrying negative charges by dissociation at the reaction of sea water (ph about 8) are responsible for the adsorption of cations by exhibition of a Donnan effect. The results obtained show clearly that besides the divalent cations Mg++ and Ca++, which according to the physico-chemical laws of the Donnan distribution must be relatively accumulated to the second power of the monovalent ones, potassium is also enriched by selective adsorption, and the K+:Na+ ratio increased significantly compared with that in sea water. This seems to indicate that the strength of attraction between the cations and the negative sites is dependent on the radii of the ions and the state of hydration and/or polarisation of the ions and binding sites.

Kesseler, H.

1980-06-01

403

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

PubMed

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

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

2014-05-21

404

Intraoperative management of heart-lung interactions: "from hypothetical prediction to improved titration".  

PubMed

Extensive literature describes the suitability of dynamic parameters to predict responsiveness in fluid. However, based on heart-lung interactions, these parameters can have serious limitations, including the use of protective lung ventilation. Although the latter seems to be beneficial for healthy patients undergoing high-risk surgery, the intraoperative interpretation of dynamic parameters to predict fluid responsiveness can be hazardous. In this context, the attending physician could, alternatively, titrate the need of fluids with a small fluid challenge, which remains unaffected by low tidal volume, the presence of arrhythmia, or the presence of spontaneous ventilation. When intraoperative prediction of fluid responsiveness is required in mechanically ventilated patients, "improved" titration should be preferred to a hypothetical prediction. PMID:25127853

Ouattara, A; Dewitte, A; Rozé, H

2014-01-01

405

Amperometry with two polarisable electrodes-XI Determination of bismuth by EDTA titration.  

PubMed

Optimum conditions have been found for a highly selective determination of bismuth via EDTA titration with biamperometric indication of the end-point. The influence of the applied potential, pH and stirring on the accuracy and selectivity of the determination has been studied. In a medium of 0.4M nitric acid only high concentrations of iron(III) and copper(II) interfere with the determination of bismuth. Zirconium, thallium(III) and indium interfere even in small concentrations. The average error of the determination of 5-100 mg of bismuth (when titrated with 0.05M EDTA solution) is +/-0-1 % rel. and for the determination of 0.5-10 mg it is +/-0.3% rel. (0.005M EDTA). The method has been verified by the analysis of a Wood's metal of known composition. PMID:18959921

Vydra, F; Vorlícek, J

1966-04-01

406

Rapid air titration method for determining SO/sub 2/ concentration in inhalation chambers  

SciTech Connect

A rapid air titration method for determining SO/sub 2/ concentration in inhalation chambers has been validated using the pararosaniline-formaldehyde (PRA) method of West and Gaeke. This air-titration (iodate) method is an adaptation of iodometric methods using a starch indicator. Potassium iodate and an excess of potassium iodide are used in the reaction. Sampling is completed in ten minutes or less and concentration is calculated by use of a simple formula. Linear equations were derived over the range of concentrations from 0.5 to 100 ppm SO/sub 2/ for uncorrected iodate bubbler results, data corrected for tandem bubbler concentrations and data corrected for mean iodate bubbler efficiency. Linear correlation with the PRA method over this range was 0.999 for all three sets of data.

Snyder, E.A.; Palmes, E.D.

1985-06-01

407

Investigation of the formation of peroxide in. gamma. -irradiated polyethylene by the method of iodometric titration  

SciTech Connect

The concentrations of hydroperoxides (HP) and dialkyl peroxides (DAP) in polyethylene (PE) powder, ..gamma.. irradiated in air at 295 K at a dose of 0.22-2.8 J/(kg x sec) up to doses of 16-300 kJ/kg, were determined by various methods of iodometric titration. Under the indicated conditions, the HP concentration reached 0.18 mole/kg, DPA 0.07 mole/kg, G /SUB HP/ was 8.3 1/100 eV; G /SUB GP/ ..integral..I /SUP -0.5/ . On the basis of the total absence of grafting of acrylamide onto ..gamma..-irradiated PE after reduction during titration of HP in it, it was concluded that grafted polymerization is initiated by the radicals of thermal decomposition of HP in PE.

Savost'yanov, V.S.; Kritskaya, D.A.; Ponomarev, A.N.

1986-09-01

408

Systemic Errors In Quantitative PCR Titration of Self-Complementary AAV Vectors and Improved Alternative Methods  

PubMed Central

Self-complementary AAV (scAAV) vector genomes contain a covalently closed hairpin derived from a mutated inverted terminal repeat which connects the two monomer single stranded genomes into a head-to-head or tail-to-tail dimer. We found that during quantitative PCR (qPCR) this structure inhibits the amplification of proximal amplicons and causes the systemic underreporting of copy number by as much as 10-fold. We show that cleavage of scAAV vector genomes with restriction endonuclease to liberate amplicons from the covalently closed terminal hairpin restores quantitative amplification, and we implement this procedure in a simple, modified qPCR titration method for scAAV vectors. Additionally, we developed and present an AAV genome titration procedure based on gel electrophoresis that requires minimal sample processing and has very low inter assay variability, and as such is well suited for the rigorous quality control demands of clinical vector production facilities. PMID:22428975

Fagone, Paolo; Wright, J. Fraser; Nathwani, Amit C.; Nienhuis, Arthur W.; Davidoff, Andrew M.; Gray, John T.

2013-01-01

409

Standard test method for aluminum in iron ores by complexometric titration  

SciTech Connect

This method covers the determination of aluminum in iron ores, concentrates, and agglomerates in the concentration range from 0.25 to 5% aluminium. The sample is fused in a zirconium crucible with a mixed flux of sodium carbonate and sodium peroxide. The fused mass is dissolved in dilute hydrochloric acid. The R/sub 2/O/sub 3/ hydroxides are precipitated with ammonia and redissolved in hydrochloric acid. Iron, titanium, etc., are removed with cupferron and chloroform. The aqueous phase is treated with nitric and perchloric acids and evaporated to dryness. After dissolving in dilute hydrochloric acid, the solution is filtered, and the filtrate is treated with an excess of ethylenediaminetetraacetic acid (EDTA). The excess EDTA is titrated with a standard zinc solution using xylenol orange indicator. Ammonium fluoride is added to release the EDTA bound to aluminum. This EDTA is then titrated with standard zinc solution, and the percent aluminum is calculated.

Not Available

1980-01-01

410

A rapid air titration method for determining SO2 concentration in inhalation chambers.  

PubMed

A rapid air titration method for determining SO2 concentration in inhalation chambers has been validated using the pararosaniline-formaldehyde (PRA) method of West and Gaeke. This air-titration (iodate) method is an adaptation of iodometric methods using a starch indicator. Potassium iodate and an excess of potassium iodide are used in the reaction. Sampling is completed in ten minutes or less and concentration is calculated by use of a simple formula. Linear equations were derived over the range of concentrations from 0.5 to 100 ppm SO2 for uncorrected iodate bubbler results, data corrected for tandem bubbler concentrations and data corrected for mean iodate bubbler efficiency. Linear correlation with the PRA method over this range was 0.999 for all three sets of data. PMID:4014008

Snyder, E A; Palmes, E D

1985-06-01

411

Flocculation of microalgae using cationic starch  

Microsoft Academic Search

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

Dries Vandamme; Imogen Foubert; Boudewijn Meesschaert; Koenraad Muylaert

2010-01-01

412

Mechanism of Oligonucleotide Release from Cationic Liposomes  

Microsoft Academic Search

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

Olivier Zelphati; Francis C. Szoka

1996-01-01

413

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

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

414

Hydrolysis-precipitation studies of aluminum (III) solutions. I. Titration of acidified aluminum nitrate solutions  

Microsoft Academic Search

Acidified aluminum nitrate solutions were titrated with alkali (NaOH or KOH) over a temperature range of 24°C to 90°C. A homogeneous distribution of added base was achieved by: (i) in situ decomposition of urea (90°C); and (ii) a novel method involving injection through a capillary submerged in the agitated salt solution.\\u000a\\u000aThe experimental pH curves are characterized by two plateaus

A. C. Vermeulen; John W. Geus; R. J. Stol; P. L. de Bruyn

1975-01-01

415

Investigation of the formation of peroxide in. gamma. -irradiated polyethylene by the method of iodometric titration  

Microsoft Academic Search

The concentrations of hydroperoxides (HP) and dialkyl peroxides (DAP) in polyethylene (PE) powder, ..gamma.. irradiated in air at 295 K at a dose of 0.22-2.8 J\\/(kg x sec) up to doses of 16-300 kJ\\/kg, were determined by various methods of iodometric titration. Under the indicated conditions, the HP concentration reached 0.18 mole\\/kg, DPA 0.07 mole\\/kg, G \\/SUB HP\\/ was 8.3

V. S. Savostyanov; D. A. Kritskaya; A. N. Ponomarev

1986-01-01

416

An accurate method of iodometric titration to measure copper valence of high- T c superconductors  

Microsoft Academic Search

The double iodometric titration is the method widely used to determine copper valence of high-T\\u000a c superconductors. There are some problems that remain to be solved, and certain procedures are used: adding KSCN to release\\u000a adsorbed iodine, adding HN4HF2 to eliminate the interference of some dopants, and using a new calculating equation to accurately calculate experiment results.\\u000a Al- and Fe-doped

W. M. Chen; X. S. Wu; J. F. Geng; J. Chen; D. B. Chen; X. Jin; S. S. Jiang

1997-01-01

417

Complexometric titration of copper(II) using nitrosochromotropic acid as a new metal indicator  

Microsoft Academic Search

Nitrosochromotropic acid gives a violet coloured soluble complex with CuII in ammonium chloride-ammonium hydroxide buffer solution, which is less stable than CuII-EDTA complex. When microquantities of CuII solution containing 1 or 2 drops of nitrosochromotropic acid in the ph range 7.25 to 8.00, are titrated with EDTA, a sharp colour change from violet to orange occurs at the end point.

C. S. Pande; T. S. Srivastava

1961-01-01

418

A Simple Karl Fischer Titration Technique for Measuring the Silanol Content of High Molecular Weight Polysiloxanes  

Microsoft Academic Search

This article presents a simple technique for measuring the silanol (SiOH) content of polysiloxanes having molecular weights of 26,000 amu or more. It extends an earlier procedure, in which 50°C methanol converts each silanol group into a methoxy group (SiOCH3) and the resulting water is measured by Karl Fischer titration. Unlike previous work, however, the present technique dissolves the high molecular

Louis A. Bloomfield

2012-01-01

419

The generalized lewis acid-base titration of palladium and niobium  

Microsoft Academic Search

The high thermodynamic stability of alloys composed of platinum group metals and group IVB and VB metals has been explained\\u000a by an electronic interaction analogous to the Lewis acid-base concept for nontransition elements. The analogy is further demonstrated\\u000a by the titration of palladium by addition of niobium. The activity of niobium in solid palladium was measured as a function\\u000a of

M. Cima; L. Brewer

1988-01-01

420

Determination of some antipsychotropic and anticholinergic phenothiazine drugs by vanadium (V) titration  

Microsoft Academic Search

Three simple, rapid and accurate titrimetric procedures using ammonium metavanadate have been developed for the determination of six phenothiazine drags in pure form and in dosage forms. The procedures are based on the oxidation of phenothiazines in acid medium to colourless sulphoxides via orange or purple coloured intermediates. In the first method, phenothiazines are titrated directly in H2SO4-H3PO4 medium to

K. Basavaiah; G. Krishnamurthy

1999-01-01

421

Micellization of Bovine ?-Casein Studied by Isothermal Titration Microcalorimetry and Cryogenic Transmission Electron Microscopy  

Microsoft Academic Search

The association behavior, critical micellization concentration (CMC), and enthalpy of demicellization (¢Hdemic) of bovine ‚-casein were studied, for the first time by isothermal titration calorimetry, in a pH 7.0 phosphate buffer with 0.1 ionic strength and in pure water. In the buffer solutions, the CMC decreased asymptotically from 0.15 to 0.006 mM as the temperature was raised from 16 to

Irina Portnaya; Uri Cogan; Yoav D. Livney; Ory Ramon; Karin Shimoni; Moshe Rosenberg; Dganit Danino

2006-01-01

422

On the total CO2-titration alkalinity-oxygen system in the Pacific Ocean  

Microsoft Academic Search

Decomposition of organic matter changes the concentrations of carbon, nitrogen, phosphorus, oxygen and titration alkalinity (TA) in the ratio 106:16:1:138:-17 (refs 1-3), so the combined effect of decomposing x mol of CaCO3 and y mol of organic matter in 1 kg of seawater on the preformed total CO2 (SigmaCO2 0), preformed TA (TA0), biogenerated SigmaCO2 [DeltaSigmaCO2(biol)] and the apparent oxygen

Chen-Tung A. Chen; Ricardo M. Pytkowicz

1979-01-01

423

Polyelectrolyte Condensation Induced by Linear Cations  

E-print Network

We examine the role of the condensing agent in the formation of polyelectrolyte bundles, via grand-canonical Monte Carlo simulations. Following recent experiments we use linear, rigid divalent cations of various lengths to induce condensation. Our results clarify and explain the experimental results for short cations. For longer cations we observe novel condensation behavior owing to alignment of the cations. We also study the role of the polyelectrolyte surface charge density, and find a nonmonotonic variation in bundle stability. This nonmonotonicity captures two trends that have been observed in separate experiments.

Camilo Guáqueta; Erik Luijten

2007-09-21

424

Potentiometric surface of the upper Floridan aquifer system, west-central Florida, May 1993  

USGS Publications Warehouse

The Floridan aquifer system consists of the Upper and Lower Floridan aquifers separated by a middle confining unit. The potentiometric surface of the Upper Floridan aquifer was mapped by determining the altitude of water levels in a network of wells and represented on a map by contours that connect points of equal altitude. This map represents water-level conditions near the end of the spring dry season when groundwater withdrawals for agricultural use were high. The cumulative rainfall for the study area was 4.84 inches above normal for the period from June 1992 to May 1993. Hydrographs of selected wells generally indicated that water levels in wells north of the Hillsborough/Pasco County line (northern area), where the aquifer generally is unconfined and groundwater withdrawals are relatively small, remained fairly uniform from year to year and season to season, whereas water levels south of the county line (southern area), where the aquifer is confined and withdrawals are relatively large, showed large year-to-year and seasonal fluctuations. Maximum daily water levels for selected wells from May 1992 through May 1993 showed that water levels were relatively stable during May 1993 in the northern part of the study area, but were declining rapidly in the southern part. Water levels in most wells measured in May 1993 were lower than those measured in September 1992. The greatest decline in water levels occurred in southern Hillsborough, central Manatee, and northern Sarasota Counties as a result of heavy seasonal groundwater withdrawals for irrigation. Water levels measured in May 1993 were generally higher than those reported for May 1992. The general increase in water levels during this period was largely the result of above-normal rainfall that resulted in below-average seasonal groundwater withdrawals from the aquifer.

Mularoni, R. A.

1994-01-01

425

Inward rectification in the transverse tubular system of frog skeletal muscle studied with potentiometric dyes.  

PubMed Central

The non-penetrating potentiometric dyes NK2367 and WW375 were used to investigate the effect of inward rectification on the weighted-average tubular membrane potential in single frog muscle fibres voltage clamped using a three-Vaseline-gap method. In 100 mM-K solution, when inward rectification was activated by hyperpolarization the steady-state amplitude of the transverse tubular system (T-system) optical signal was reduced, and its rise time was faster than that recorded for an equivalent depolarization. The voltage dependence of the optical attenuation followed that of inward rectification, increasing with increasing hyperpolarization. For a voltage-clamp step of -140 mV the optical attenuation was 0.72 which corresponds to a weighted-average T-system potential change of 100 mV. When inward rectification was blocked in a Cs, TEA solution the optical attenuation was also abolished. The voltage dependence of the block of the inward currents in solutions containing low concentrations of Cs was also reflected in the T-system optical signals. Our results were satisfactorily predicted by a radial cable model of the T-system, assuming the same specific inward rectifier conductance in surface and tubular membranes. This analysis predicts that the measured optical attenuation corresponds to a decrease in the tubular space constant, lambda T, from 120 micron under passive conditions to about 40 micron when inward rectification is fully, activated. The voltage dependence of inward rectification measured at the surface membrane was reasonably well predicted by assuming that the specific conductance obeyed a Boltzmann type of voltage dependence; the major effect of tubular decrements was to reduce the steepness of the total (surface + T-system) conductance-voltage relation. PMID:3873536

Ashcroft, F M; Heiny, J A; Vergara, J

1985-01-01

426

New organotin(IV) ascorbates: synthesis, spectral characterization, biological and potentiometric studies  

NASA Astrophysics Data System (ADS)

New organotin(IV) ascorbates of the general formulae R 3Sn(HAsc) (where R=Me, n-Pr, n-Bu and Ph) and R 2Sn(Asc) (where R= n-Bu and Ph) have been synthesized by the reaction of R nSnCl 4- n (where n=2 or 3) with monosodium- L-ascorbate. The bonding and coordination behaviour in these complexes are discussed on the basis of UV-Vis, IR, Far-IR, 1H and 13C NMR, and 119Sn Mössbauer spectroscopic studies. L-Ascorbic acid acts as a monoanionic bidentate ligand in R 3Sn(HAsc) coordinating through O(1) and O(3). The Mössbauer studies together with IR and NMR studies suggest that for these polymeric derivatives, the polyhedron is trigonal bipyramidal around tin with three organic groups in the equatorial positions. In R 2Sn(Asc), L-ascorbic acid acts as dianionic tetradentate ligand and a polymeric structure with octahedral geometry around tin with trans organic groups has been tentatively proposed. The complexes have been assayed for their anti-inflammatory and cardiovascular activity. Ph 2Sn(Asc) has been found to show the highest activity among the studied complexes. It is suggested on the basis of potentiometric studies of Me 2Sn(IV) and Me 3Sn(IV) systems with L-ascorbic acid that under physiological conditions (pH=7.0) Me 2Sn(HAsc)(OH) (˜60%), Me 2Sn(OH) 2 (˜40%) and Me 3Sn(HAsc) (˜60%), Me 3Sn(OH) (˜40%), respectively, are existing, which may be responsible for their biological activities.

Nath, Mala; Jairath, Ruchi; Eng, George; Song, Xueqing; Kumar, Ashok

2005-01-01

427

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

SciTech Connect

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

Wang, Y.; Zhang, Z; Jain, V; Yi, J; Mueller, S; Sokolov, J; Liu, Z; Levon, K; Rigas, B; Rafailovich, M

2010-01-01

428

Potentiometric Sensor for Real-Time Monitoring of Multivalent Ion Concentrations in Molten Salt  

SciTech Connect

Electrorefining of spent metallic nuclear fuel in high temperature molten salt systems is a core technology in pyroprocessing, which in turn plays a critical role in the development of advanced fuel cycle technologies. In electrorefining, spent nuclear fuel is treated electrochemically in order to effect separations between uranium, noble metals, and active metals, which include the transuranics. The accumulation of active metals in a lithium chloride-potassium chloride (LiCl-KCl) eutectic molten salt electrolyte occurs at the expense of the UCl3-oxidant concentration in the electrolyte, which must be periodically replenished. Our interests lie with the accumulation of active metals in the molten salt electrolyte. The real-time monitoring of actinide concentrations in the molten salt electrolyte is highly desirable for controlling electrochemical operations and assuring materials control and accountancy. However, real-time monitoring is not possible with current methods for sampling and chemical analysis. A new solid-state electrochemical sensor is being developed for real-time monitoring of actinide ion concentrations in a molten salt electrorefiner. The ultimate function of the sensor is to monitor plutonium concentrations during electrorefining operations, but in this work gadolinium was employed as a surrogate material for plutonium. In a parametric study, polycrystalline sodium beta double-prime alumina (Na-ß?-alumina) discs and tubes were subject to vapor-phase exchange with gadolinium ions (Gd3+) using a gadolinium chloride salt (GdCl3) as a precursor to produce gadolinium beta double-prime alumina (Gd-ß?-alumina) samples. Electrochemical impedance spectroscopy and microstructural analysis were performed on the ion-exchanged discs to determine the relationship between ion exchange and Gd3+ ion conductivity. The ion-exchanged tubes were configured as potentiometric sensors in order to monitor real-time Gd3+ ion concentrations in mixtures of gadolinium chloride (GdCl3) in LiCl-KCl eutectic molten salts through measurement of the potential difference between a reference and working electrode.

Peter A. Zink; Jan-Fong Jue; Brenda E. Serrano; Guy L. Fredrickson; Ben F. Cowan; Steven D. Herrmann; Shelly X. Li

2010-07-01

429

Statistical mechanical model of coupled transcription from multiple promoters due to transcription factor titration  

PubMed Central

Transcription factors (TFs) with regulatory action at multiple promoter targets is the rule rather than the exception, with examples ranging from the cAMP receptor protein (CRP) in E. coli that regulates hundreds of different genes simultaneously to situations involving multiple copies of the same gene, such as plasmids, retrotransposons, or highly replicated viral DNA. When the number of TFs heavily exceeds the number of binding sites, TF binding to each promoter can be regarded as independent. However, when the number of TF molecules is comparable to the number of binding sites, TF titration will result in correlation (“promoter entanglement”) between transcription of different genes. We develop a statistical mechanical model which takes the TF titration effect into account and use it to predict both the level of gene expression for a general set of promoters and the resulting correlation in transcription rates of different genes. Our results show that the TF titration effect could be important for understanding gene expression in many regulatory settings. PMID:24580252

Rydenfelt, Mattias; Cox, Robert Sidney; Garcia, Hernan; Phillips, Rob

2014-01-01

430

Within-Subject Comparison of Degree of Delay Discounting Using Titrating and Fixed Sequence Procedures  

PubMed Central

Different procedures are often used across experiments to estimate the degree of delay discounting, a common measure of impulsivity. In all procedures, participants indicate their choice between a reward available immediately and one available after a delay. The present experiment determined whether there are differences in the degree of discounting for a hypothetical $100 produced by a procedure that titrates the immediate amount (titrating sequence procedure) versus a procedure that presents a fixed sequence of immediate amounts (fixed sequence procedure) using a within-subject design. The adult human participants showed no significant differences in degree of discounting between procedures as assessed by a hyperboloid model and the Area Under the Curve. Furthermore, the Area Under the Curve values from the two procedures showed a strong positive correlation. These findings suggest there may be no systematic difference between the degree of delay discounting as estimated by the titrating sequence and fixed sequence procedures. Given the apparent similarities in the results, it appears researchers may be justified in basing their choice of which procedure to use on convenience. PMID:20932882

Rodzon, Katrina; Berry, Meredith S.; Odum, Amy L.

2014-01-01

431

Statistical mechanical model of coupled transcription from multiple promoters due to transcription factor titration  

NASA Astrophysics Data System (ADS)

Transcription factors (TFs) with regulatory action at multiple promoter targets is the rule rather than the exception, with examples ranging from the cAMP receptor protein (CRP) in E. coli that regulates hundreds of different genes simultaneously to situations involving multiple copies of the same gene, such as plasmids, retrotransposons, or highly replicated viral DNA. When the number of TFs heavily exceeds the number of binding sites, TF binding to each promoter can be regarded as independent. However, when the number of TF molecules is comparable to the number of binding sites, TF titration will result in correlation (“promoter entanglement”) between transcription of different genes. We develop a statistical mechanical model which takes the TF titration effect into account and use it to predict both the level of gene expression for a general set of promoters and the resulting correlation in transcription rates of different genes. Our results show that the TF titration effect could be important for understanding gene expression in many regulatory settings.

Rydenfelt, Mattias; Cox, Robert Sidney, III; Garcia, Hernan; Phillips, Rob

2014-01-01

432

Iodometric titration for determining the oxygen content of samples doped with Fe and Co  

NASA Astrophysics Data System (ADS)

Double iodometric titration is a method developed for high- Tc superconductivity. It has been widely used to determine the effective oxidation of copper and to figure out the oxygen content in a sample in the past years. If a sample is doped with some metals like iron and cobalt, these metal ions can interfere in experiment results. This is a major defect for iodometric titration. To solve this problem, we introduce ammonium hydrogen fluoride as a complex agent into the method. The agent can prevent the interference of ions of iron and cobalt. For samples LaBa 2Cu 3- xFe xO y and YBa 2Cu 3- xCo xO y, we determine the oxygen content by an improved double iodometric titration in which the ammonium hydrogen fluoride is used as an interference-free agent. For samples doped with a small amount of Fe or Co, experiment results agree well with those of other researchers. As to samples doped with a large amount of Fe or Co, we determine their values of oxygen content and the results are reasonable.

Chen, W. M.; Hong, W.; Geng, J. F.; Wu, X. S.; Ji, W.; Li, L. Y.; Qui, L.; Jin, X.

1996-02-01

433

Chaotic dynamics of resting ventilatory flow in humans assessed through noise titration  

E-print Network

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.

Marc Wysocki; Marie-Noelle Fiamma; Christian Straus; Chi-Sang Poon; Thomas Similowski

2006-06-12

434

Calorimetry, activity, and micro-FTIR analysis of CO chemisorption, titration, and oxidation on supported Pt  

NASA Technical Reports Server (NTRS)

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.

Sermon, Paul A.; Self, Valerie A.; Vong, Mariana S. W.; Wurie, Alpha T.

1990-01-01

435

Automated spectrophotometric analyzer for rapid single-point titration of seawater total alkalinity.  

PubMed

An automated analyzer was developed to achieve fast, precise, and accurate measurements of seawater total alkalinity (AT) based on single-point titration and spectrophotometric pH detection. The single-point titration was carried out in a circulating loop, which allowed the titrant (hydrochloric acid and bromocresol green solution) and a seawater sample to mix at a constant volume ratio. The dissolved CO2 in the sample-titrant mixture was efficiently removed by an inline CO2 remover, which consists of a gas-permeable tubing (Teflon AF2400) submerged in a sodium hydroxide (NaOH) solution. The pH of the mixture was then measured with a custom-made spectrophotometric detection system. The analyzer was calibrated against multiple certified reference materials (CRMs) with different AT values. The analyzer features a sample throughput time of 6.5 min with high precision (±0.33-0.36 ?mol kg(-1); n = 48) and accuracy (-0.33 ± 0.99 ?mol kg(-1); n = 10). Intercomparison to a traditional open-cell AT titrator showed overall good agreement of 0.88 ± 2.03 ?mol kg(-1) (n = 22). The analyzer achieved excellent stability without recalibration over 11 days, during which time 320 measurements were made with a total running time of over 40 h. Because of its small size, low power consumption requirements, and its ability to be automated, the new analyzer can be adapted for underway and in situ measurements. PMID:23968512

Li, Quanlong; Wang, Fengzhen; Wang, Zhaohui Aleck; Yuan, Dongxing; Dai, Minhan; Chen, Jinshun; Dai, Junwei; Hoering, Katherine A

2013-10-01

436

Potentiometric and solubility studies of association quotients of aluminum malonate complexation in NaCl media to 75°C  

NASA Astrophysics Data System (ADS)

A potentiometric method was used to determine the formation quotients for aluminum-malonate (Al(Ma) y3-2y, Ma ? CH 2(CO 2) 22-) complexes from 5 to 75°C at four ionic strengths from 0.1 to 1.0 molal in aqueous NaCl media. Two mononuclear aluminum-malonate species, Al(Ma) + and Al(Ma) 2-, were identified, and the formation quotients for these species were modeled by empirical equations to describe their temperature and ionic strength dependencies. Differentiation of the two empirical equations with respect to temperature provided thermodynamic quantities for the Al-malonate complexes. The thermodynamic quantities obtained for Al(Ma) + at 25°C and infinite dilution are: log K 1 = 7.49 ± 0.18, ?H °1 = 19 ± 5 kJ · mol -1, ?S °1 = 208 ± 18 J · K -1 · mol -1 and ?C °p1 = 331 ± 120 J · K -1 · mol -1; whereas the values for Al(Ma) 2- are: log K 2 = 12.62 ± 0.40, ?H °2 = 29 ± 10 kJ · mol -1, ?S °2 = 340 ± 36 J · K -1 mol -1 and ?C °p2 = 575 ± 230 J · K -1 mol -1. These thermodynamic values indicate that Al(Ma) +, a chelate complex, is much more stable than the equivalent monodentate Al-diacetate complex (Al(Ac) 2+) (Palmer and Bell, 1994). A solubility study, which was undertaken to verify the 50°C potentiometric data, was performed by reacting powdered gibbsite (Al(OH) 3) with malonic acid solutions at 0.1 molal ionic strength in aqueous NaCl media. The results of the solubility study are in excellent agreement with the potentiometric data.

Ridley, Moira K.; Palmer, Donald A.; Wesolowski, David J.; Kettler, Richard M.

1998-07-01

437

Group Communication Speci cations: A Comprehensive Study  

E-print Network

, and Roman Vitenberg The Technion Department of Computer Science. View-oriented group communication light on the usefulness of the presented speci#12;cations. This paper is aimed at both system builders and theoretical researchers. The speci#12;cation framework presented in this paper will help builders of group

Keidar, Idit

438

Effects of Organic and Inorganic Polyamine Cations  

E-print Network

of spermine, spermidine, putrescine, and cobalt [Co(III)]­hexamine cations on the solution structure of HSA cation: spermine Co(III)­hexamine spermidine putrescine. The overall binding constants are 1.7 104 , 1 of the interaction of HSA with sperm- ine, spermidine, putrescine, and cobalt­hexamine cat- ions with the following

Carpentier, Robert

439

Representing Face Images for Emotion Classi cation  

E-print Network

" smile. The quality of the displayed emotion is one of the reasons cited by Cottrell and MetcalfeRepresenting Face Images for Emotion Classi cation Curtis Padgett Department of Computer Science of three distinct rep- resentation schemes for facial emotions using a single classi cation strategy neural

Cottrell, Garrison W.

440

Determination of NO/sub 2//sup -//NO/sub 3//sup -/ mixtures by titration with ascorbic acid  

SciTech Connect

The analysis of nitrite-nitrate mixtures by indirect titration with ascorbic acid performed before and after passage through a reducing Cd column is proposed and discussed with particular reference to experimental conditions, calculation scheme and concentration ranges.

Campanella, L.; Paoletti, A.M.

1982-01-01

441

Cation Enhancement of Internally Coated Metal Container Corrosion Failure  

Microsoft Academic Search

The effect of different cations on corrosion rates of internally coated metal containers at rest potential was studied. Time before the failure of 30% of the internally coated metal containers (T[sub 30]) decreased in the order: deionized water > lithium cation > sodium cation > potassium cation > calcium cation for salt concentrations from 0.0 M to 0.1 M. This

W. S. Tait; K. A. Handrich

1994-01-01

442

Synthesis and characterization of a novel hybrid nano composite cation exchanger poly-o-toluidine Sn(IV) tungstate: Its analytical applications as ion-selective electrode  

NASA Astrophysics Data System (ADS)

A novel organic-inorganic nano composite cation exchanger poly-o-toluidine Sn(IV) tungstate has been synthesized by incorporation of a polymer material into inorganic precipitate. The material is a class of hybrid ion-exchanger with good ion-exchange properties, reproducibility, stability and good selectivity for heavy metals. The physico-chemical properties of this nano composite material were characterized by using XRD, TGA, FTIR, SEM and TEM. The ion-exchange capacity, pH titrations, elution behavior and chemical stability were also carried out to study ion-exchange properties of the material. Distribution studies for various metal ions revealed that the nano composite is highly selective for Cd(II). An ion-selective membrane electrode was fabricated using this material for the determination of Cd(II) ions in solutions. The analytical utility of this electrode was established by employing it as an indicator electrode in electrometric titrations.

Khan, Asif Ali; Shaheen, Shakeeba

2013-02-01

443

A Full Automatic Device for Sampling Small Solution Volumes in Photometric Titration Procedure Based on Multicommuted Flow System  

PubMed Central

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

Borges, Sivanildo S.; Vieira, Glaucia P.; Reis, Boaventura F.

2007-01-01

444

Ultrasensitive and real-time detection of proteins in blood using a potentiometric carbon-nanotube aptasensor.  

PubMed

Potentiometric sensing represents the preferred technique in many routine measurements of pH and ions. Unfortunately, the simplicity of the technique has not been exploited so far in high throughput biomolecular sensing. In this work, we demonstrate the capabilities of the hybrid functional material carbon nanotubes/aptamer for the creation of a new generation of nuclease-resistant aptasensors using the potentiometric transduction capabilities of single-walled carbon nanotubes in combination with the recognition capabilities of a protein-specific RNA aptamer. The aptasensor was used to detect and identify disease-related proteins at attomolar concentration values in a rapid and non-expensive way. The variable surface glycoprotein from African Trypanosomes was chosen as an ideal model system for a pathogenic exoantigen protein in a clinical sample. Variations in the electromotive force are achieved in real-time upon the direct addition of diluted real blood samples containing the target protein thus eliminating the need of preliminary matrix removal. This work would open the door to real-time diagnostic assays for a wide range of diseases, but also to the rapid molecular detection of several proteins in truly customizable protein biosensing platforms. PMID:23017685

Zelada-Guillén, Gustavo A; Tweed-Kent, Ailis; Niemann, Moritz; Göringer, H Ulrich; Riu, Jordi; Rius, F Xavier

2013-03-15

445

SIA system employing the transient response from a potentiometric sensor array--Correction of a saline matrix effect.  

PubMed

A Sequential Injection Analysis (SIA) system and an 8-potentiometric all-solid-state sensor array were coupled in a simple and automated electronic tongue device. The potentiometric sensors used were planar microfabricated structures with standard PVC membranes deposited onto a gold contact. The SIA system permitted the automated operation and generation of the calibration data, needed to build an Artificial Neural Network model, thanks to the precise dosing and mixing of volumes of stock solutions. The resolution of a four-ion mixture, i.e. ammonium, sodium, nitrate and chloride was the study case used for characterization of the system. Two different variants for signal acquisition, steady-state and transient recording, were arranged and compared. The dynamic treatment is shown to offer improved performance thanks to the benefits of the kinetic resolution. For this, it first extracts meaningful data from a FFT transform of each sensor's transient, which is then fed to an ANN model for estimation of each concentration in the four-ion mixture. While in a standard laboratory situation there was no difference between the two approaches, the dynamic treatment allowed the correction of a matrix effect in the case study, where an uncontrolled saline effect could be counterbalanced. PMID:20678648

Mimendia, A; Gutiérrez, J M; Opalski, L J; Ciosek, P; Wróblewski, W; del Valle, M

2010-08-15

446

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

PubMed

A standard addition method was implemented by using a flow manifold able to perform automatically multiple standard additions and in-line sample treatment. This analytical strategy was based on the in-line mixing of sample and standard addition solutions, using a merging zone approach. The flow system aimed to exploit the standard addition method to quantify the target analyte particularly in cases where the analyte concentration in the matrix is below the lower limit of linear response of the detector. The feasibility of the proposed flow configuration was assessed through the potentiometric determination of fluoride in sea salts of different origins and different types of coffee infusions. The limit of quantification of the proposed manifold was 5×10(-6)molL(-1), 10-fold lower than the lower limit of linear response of the potentiometric detector used. A determination rate of 8samplesh(-1) was achieved considering an experimental procedure based on three standard additions per sample. The main advantage of the proposed strategy is the simple approach to perform multiple standard additions, which can be implemented with other ion selective electrodes, especially in cases when the primary ion is below the lower limit of linear response of the detector. PMID:25435218

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

2015-02-01

447

Potentiometric Surface in the Sparta-Memphis Aquifer of the Mississippi Embayment, Spring 2007  

USGS Publications Warehouse

The most widely used aquifer for industry and public supply in the Mississippi embayment in Arkansas, Louisiana, Mississippi, and Tennessee is the Sparta-Memphis aquifer. Decades of pumping from the Sparta-Memphis aquifer have affected ground-water levels throughout the Mississippi embayment. Regional assessments of water-level data from the aquifer are important to document regional water-level conditions and to develop a broad view of the effects of ground-water development and management on the sustainability and availability of the region's water supply. This information is useful to identify areas of water-level declines, identify cumulative areal declines that may cross State boundaries, evaluate the effectiveness of ground-water management strategies practiced in different States, and identify areas with substantial data gaps that may preclude effective management of ground-water resources. A ground-water flow model of the northern Mississippi embayment is being developed by the Mississippi Embayment Regional Aquifer Study (MERAS) to aid in answering questions about ground-water availability and sustainability. The MERAS study area covers parts of eight states including Alabama, Arkansas, Illinois, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee and covers approximately 70,000 square miles. The U.S. Geological Survey (USGS) and the Mississippi Department of Environmental Quality Office of Land and Water Resources measured water levels in wells completed in the Sparta-Memphis aquifer in the spring of 2007 to assist in the MERAS model calibration and to document regional water-level conditions. Measurements by the USGS and the Mississippi Department of Environmental Quality Office of Land and Water Resources were done in cooperation with the Arkansas Natural Resources Commission; the Arkansas Geological Survey; Memphis Light, Gas and Water; Shelby County, Tennessee; and the city of Germantown, Tennessee. In 2005, total water use from the Sparta-Memphis aquifer in the Mississippi embayment was about 540 million gallons per day (Mgal/d). Water use from the Sparta-Memphis aquifer was about 170 Mgal/d in Arkansas, about 68 Mgal/d in Louisiana, about 97 Mgal/d in Mississippi, and about 205 Mgal/d in Tennessee. The author acknowledges, with great appreciation, the efforts of the personnel in the U.S. Geological Survey Water Science Centers of Arkansas, Kentucky, Louisiana, Mississippi, Missouri, and Tennessee, and the Mississippi Department of Environmental Quality Office of Land and Water Resources that participated in the planning, water-level measurement, data evaluation, and review of the potentiometric-surface map. Without the contribution of data and the technical assistance of their staffs, this report would not have been completed.

Schrader, T.P.

2008-01-01

448

Speci cation and Veri cation of a Steam-Boiler with Signal-Coq Micka l Kerb uf1  

E-print Network

Speci cation and Veri cation of a Steam-Boiler with Signal-Coq Micka l Kerb uf1 , David Nowak2 assistant, Coq, for the speci cation and the veri cation of co-inductive properties of the well-known steam-boiler cation tools. Keywords: synchronous programming, theorem proving, the steam- boiler problem. 1

Boyer, Edmond

449

A partially substituted calix[4]resorcarene receptor and its selective recognition for soft metal cations (silver and mercury).  

PubMed

A partially substituted calix[4]resorcarene receptor, namely, 5,17-ethylthiomethylated calix[4]resorcarene, 1, has been synthesized and characterized by 1H NMR in CD3OD, CDCl3, and CD3CN and 13C NMR in CD3OD, as well as by 2D NMR. Partition data in the methanol-hexane and acetonitrile-hexane solvent systems show that the monomeric species are predominant in these solvents. The solubility of 1 in various solvents was determined at 298.15 K. These data were used to calculate the standard solution Gibbs energy of 1 in these solvents. Taking hexane as the reference solvent, the standard transfer Gibbs energy of 1 to various solvents was calculated. Good agreement is found between the DeltatG(o) values in the hexane-methanol and hexane-acetonitrile and the DeltapG(o) values of this ligand in these solvent systems. The higher partition constant of 1 in the hexane-methanol relative to the hexane-acetonitrile solvent system contrasts with corresponding data for the fully functionalized receptor, 2. This is explained in terms of the solvation differences of these receptors in these solvents as reflected in the DeltatG(o) values. The cation complexing properties of this receptor were investigated through 1H NMR, conductance, calorimetric, and potentiometric methods. Among the metal cations (alkali, alkaline earth, heavy, and transition), 1 interacts only with Ag+ in methanol and Hg2+ in propylene carbonate, acetonitrile, methanol, and N,N-dimethylformamide. While 1 forms a 1:1 complex with Ag+ in methanol, the hosting ability of the receptor for the mercury cation is enhanced in methanol, acetonitrile, and N,N-diethylformamide. Thus, Hg2+ complexes of 1:2 (ligand:metal cation) stoichiometry are found in these solvents. In moving to propylene carbonate, the composition of the mercury complex is altered from 1:2 to 1:1. The results are compared with corresponding data for 2 and these metal cations in the appropriate solvents. The lack of stability observed for 2 and Hg2+ in acetonitrile resulting from the departure of pendant arms from the resorcarene backbone greatly contrasts with the high stability observed for 1 and this metal cation in the various solvents. Preliminary results on the extraction of silver picrate by this ligand in the water-dichloromethane solvent system are reported. Final conclusions are given. PMID:18220386

Danil de Namor, Angela F; Chaaban, Jinane K

2008-02-21

450

Non-damaging laser therapy of the macula: Titration algorithm and tissue response  

NASA Astrophysics Data System (ADS)

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.

Palanker, Daniel; Lavinsky, Daniel; Dalal, Roopa; Huie, Philip

2014-02-01

451

Molecular Dynamics Simulation of the Titration of Polyoxocations in Aqueous Solution  

SciTech Connect

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.

Rustad, James R.

2005-09-01

452

Cationic phospholipids: structure?transfection activity relationships  

SciTech Connect

Synthetic cationic lipids are presently the most widely used non-viral gene carriers. Examined here is a particularly attractive cationic lipid class, triester phosphatidylcholines (PCs) exhibiting low toxicities and good transfection efficiency. Similarly to other cationic lipids, they form stable complexes (lipoplexes) with the polyanionic nucleic acids. A summary of studies on a set of {approx}30 cationic PCs reveals the existence of a strong, systematic dependence of their transfection efficiency on the lipid hydrocarbon chain structure: transfection activity increases with increase of chain unsaturation from 0 to 2 double bonds per lipid and decreases with increase of chain length in the range {approx}30-50 total number of chain carbon atoms. Maximum transfection was observed for ethyl phosphate PCs (EPCs) with monounsaturated 14:1 chains (total of 2 double bonds and 30 chain carbon atoms). Lipid phase behavior is known to depend strongly on the chain molecular structure and the above relationships thus substantiate a view that cationic PC phase propensities are an important determinant of their activity. Indeed, X-ray structural studies show that the rate of DNA release from lipoplexes as well as transfection activity well correlate with non-lamellar phase progressions observed in cationic PC mixtures with membrane lipids. These findings appear to be of considerable interest because, according to current views, key processes in lipid-mediated transfection such as lipoplex disassembly and DNA release within the cells are believed to take place upon cationic lipid mixing with cellular lipids.

Koynova, Rumiana; Tenchov, Boris; (NWU)

2010-01-18

453

Inclusion complex of benzocaine and ?-cyclodextrin: 1H NMR and isothermal titration calorimetry studies  

NASA Astrophysics Data System (ADS)

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.

Mic, Mihaela; P?rn?u, Adrian; Bogdan, Mircea; Turcu, Ioan

2013-11-01

454

Complexometric titration of calcium in the presence of larger amounts of magnesium.  

PubMed

A simple and accurate titrimetric determination of calcium in the presence of larger amounts of magnesium is proposed. Calcium is extracted into a small volume of organic solvent as its glyoxal-bis(2-hydroxyanil) complex, and the calcium is titrated with EGTA. The end-point is sharp, and occurs when the red colour of the organic layer vanishes. This method has been successfully applied to the determination of calcium in sea-water with an error less than 0.1%. PMID:18960309

Tsunogai, S; Nishimura, M; Nakaya, S

1968-04-01

455

DNA bending by small, mobile multivalent cations.  

PubMed

We propose a purely electrostatic mechanism by which small, mobile, multivalent cations can induce DNA bending. A multivalent cation binds at the entrance to the B-DNA major groove, between the two phosphate strands, electrostatically repelling sodium counterions from the neighboring phosphates. The unscreened phosphates on both strands are strongly attracted to the groove-bound cation. This leads to groove closure, accompanied by DNA bending toward the cationic ligand. We explicitly treat the dynamic character of the cation-DNA interaction using an adiabatic approximation, noting that DNA bending is much slower than the diffusion of nonspecifically bound, mobile cations. We make semiquantitative estimates of the free energy components of bending-electrostatic (with a sigmoidal distance-dependent dielectric function), elastic, and entropic cation localization-and find that the equilibrium state is bent B-DNA stabilized with a self-localized cation. This is a bending polaron, formation of which should be critically dependent on the strength of electrostatic interaction and the concentration of highly mobile cations available for self-localization. We predict that the resultant bend will be large (approximately 20-40 degrees), smooth (because it is spread over 6 bp), and infrequent. The stability of such a bend can be variable, from transient to highly stable (static) bending, observable with standard curvature-measuring techniques. We further predict that this bending mechanism will have an unusual sequence dependence: sequences with less binding specificity will be more bent, unless the specific binding site is in the major groove. PMID:9635768

Rouzina, I; Bloomfield, V A

1998-06-01

456

Collisionally activated dissociation of N-acylpyridinium cations  

Microsoft Academic Search

1 ions with activation energies which are strongly decreased\\/increased by stabilizing\\/destabilizing electron-donor\\/ acceptor substituents in the aroyl group. N-Alkylcarbonyl- and N-phenoxycarbonyl-pyridinium cations fragment via ion molecule complexes which dissociate to pyridinium cation and ketene or CO2 1 aryne. N-Alkoxycarbonylpyridinium cations form pyridinium cations via detectable N-carboxypyridinium cations. The propensity of those cations to undergo SN1 or SN2 reactions is discussed.

Alan R. Katritzky; Richard D. Burton; Petia A. Shipkova; Ming Qi; Clifford H. Watson; John R. Eyler

1998-01-01

457

Spontaneous aggregate transition in mixtures of a cationic gemini surfactant with a double-chain cationic surfactant.  

PubMed

Controllable aggregate transitions were realized by mixing two kinds of cationic surfactants, hexylene-1,6-bis(dodecyldimethylammonium bromide) (C(12)C(6)C(12)Br(2)) and didodecyldimethylammonium bromide (DDAB). It was found that two parameters are the main factors determining the aggregation behavior of the mixed system, the total concentration of DDAB and C(12)C(6)C(12)Br(2) (C(T)), and the mole fraction of DDAB in the mixtures of DDAB and C(12)C(6)C(12)Br(2) (X(DDAB)). How these two parameters act on the aggregate transitions was studied in detail by various measurements including surface tension, turbidity, electrical conductivity, ? potential, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and (1)H NMR. When C(T) was constant, spontaneous vesicle-to-micelle transitions were found with decreasing X(DDAB) at high C(T). When X(DDAB) was constant, aggregate transitions were generated by gradually increasing C(T), depending on different X(DDAB) ranges. At X(DDAB) < 0.6, small spherical aggregates formed first and then transferred to vesicles, and finally the vesicles transitioned to micelles. At X(DDAB) ? 0.6, the progressive increase in C(T) led to aggregate transitions on the order of the arising of vesicles, the continuous growth of vesicles, the disruption of vesicles into micelles, and the final coexistence of vesicles and micelles. The hydrophobic interaction and electrostatic repulsion between DDAB and C(12)C(6)C(12)Br(2) together with the related degree of ionization and hydration of the surfactants were gradually adjusted by changing the ratio and the total concentration of these two surfactants, which should be responsible for the complicated aggregation behavior. PMID:22827887

Tian, Maozhang; Fan, Yaxun; Ji, Gang; Wang, Yilin

2012-08-21

458

THE PENETRATION OF SOME CATIONS INTO MUSCLE  

PubMed Central

The influx of Na+, K+, Rb+, and Cs+ into frog sartorius muscle has been followed. The results show that a maximum rate is found for K+, while Na+ and Cs+ penetrate much more slowly. Similar measurements with Ca++, Ba++, and Ra++ show that Ba++ penetrates at a rate somewhat greater than that of either Ca++ or Ra++. All these divalent cations, however, penetrate at rates much slower than do the alkali cations. The results obtained are discussed with reference to a model that has been developed to explain the different penetration rates for the alkali cations. PMID:13631206

Mullins, L. J.

1959-01-01

459

A single-beam titration method for the quantification of open-path Fourier transform infrared spectroscopy  

NASA Astrophysics Data System (ADS)

This study introduced a quantitative method that can be used to measure the concentration of analytes directly from a single-beam spectrum of open-path Fourier Transform Infrared Spectroscopy (OP-FTIR). The peak shapes of the analytes in a single-beam spectrum were gradually canceled (i.e., "titrated") by dividing an aliquot of a standard transmittance spectrum with a kn