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1

Modeling potentiometric titration behavior of glauconite  

Microsoft Academic Search

Potentiometric titration behavior and the effects of dissolution on the titration experiment of a complex natural clay mineral, glauconite, were investigated and interpreted according to surface complexation theory. Considerable dissolution was detected in the time frame of the titration experiments, with the amount of individual cations released from glauconite a function of solution variables and dissolution kinetics. Dissolution effects can

Weiping Lu; Edward H. Smith

1996-01-01

2

Simple sensor for potentiometric titrations  

SciTech Connect

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

Selig, W.

1982-01-01

3

Potentiometric titration of metal ions in ethanol.  

PubMed

The potentiometric titrations of Zn2+, Cu2+ and 12 Ln3+ metal ions were obtained in ethanol to determine the titration constants (defined as the at which the [-OEt]/[Mx+]t ratios are 0.5, 1.5, and 2.5) and in two cases (La3+ and Zn2+) a complete speciation diagram. Several simple monobasic acids and aminium ions were also titrated to test the validity of experimental titration measurements and to establish new constants in this medium that will be useful for the preparation of buffers and standard solutions. The dependence of the titration constants on the concentration and type of metal ion and specific counterion effects is discussed. In selected cases, the titration profiles were analyzed using a commercially available fitting program to obtain information about the species present in solution, including La3+ for which a dimer model is proposed. The fitting provides the microscopic values for deprotonation of one to four metal-bound ethanol molecules. Kinetics for the La3+-catalyzed ethanolysis of paraoxon as a function of are presented and analyzed in terms of La3+ speciation as determined by the analysis of potentiometric titration curves. The stability constants for the formation of Zn2+ and Cu2+ complexes with 1,5,9-triazacyclododecane as determined by potentiometric titration are presented. PMID:16961382

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

2006-09-18

4

Potentiometric titrations using pencil and graphite sensors  

SciTech Connect

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

Selig, W.S.

1984-01-01

5

Potentiometric Titrations in a Poly(dimethylsiloxane)-Based Microfluidic Device  

E-print Network

Potentiometric Titrations in a Poly(dimethylsiloxane)-Based Microfluidic Device Rosaria Ferrigno device, fabricated in poly(dimethylsiloxane), that is used for potentiometric titrations. This system and characterize a microfluidic device that carries out potentiometric titrations and that uses serial dilution

Prentiss, Mara

6

Cetylpyridinium–iodomercurate PVC membrane ion selective electrode for the determination of cetylpyridinium cation in Ezafluor mouth wash and as a detector for some potentiometric titrations  

Microsoft Academic Search

A potentiometric method is described for the determination of cetylpyridinium (CP) cation using a polyvinyl chloride powder (PVC) membrane sensor based on CP–iodomercurate ion pair as an electroactive material. The sensor shows a linear response for CP ion over the concentration range of 2×10?6–1×10?3 M at 25°C. The electrode posses a sub-Nernstian slope of 29.0±0.4 mV decade?1, which has been

M. N Abbas; G. A. E Mostafa; A. M. A Homoda

2000-01-01

7

The use of graphite electrodes in potentiometric titrations  

SciTech Connect

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

Selig, W.S.

1987-04-01

8

Potentiometric titrations of rutile suspensions to 250 C  

SciTech Connect

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

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

1998-04-15

9

Potentiometric Titrations of Rutile Suspensions to 250°C  

Microsoft Academic Search

A stirred hydrogen electrode concentration cell was used to conduct potentiometric titrations of rutile suspensions from 25 to 250°C in NaCl and tetramethylammonium chloride media (0.03 to 1.1m). Hydrothermal pretreatment of the rutile improved titration reproducibility, decreased titration hysteresis, and facilitated determination of the point of zero net proton charge (pHznpc). These pHznpc values are 5.4, 5.1, 4.7, 4.4, 4.3

Michael L Machesky; David J Wesolowski; Donald A Palmer; Ken Ichiro-Hayashi

1998-01-01

10

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

E-print Network

POTENTIOMETRIC TITRATION OF AN ACID MIXTURE Background Reading: Harris, 7th ed., Chapter 11. Skoog equivalence point to permit estimation with visual indicators, a potentiometric titration with a pH meter added. The titration may be terminated at pH 11. #12;Potentiometric Titration of an Acid Mixture, Page 2

McQuade, D. Tyler

11

Symmetry Properties of Potentiometric Titration Curves.  

ERIC Educational Resources Information Center

Demonstrates how the symmetry properties of titration curves can be efficiently and rigorously treated by means of a simple method, assisted by the use of logarithmic diagrams. Discusses the symmetry properties of several typical titration curves, comparing the graphical approach and an explicit mathematical treatment. (Author/JM)

Macca, Carlo; Bombi, G. Giorgio

1983-01-01

12

Surface properties of red mud particles from potentiometric titration  

Microsoft Academic Search

Acid\\/basic potentiometric titration has been used to obtain data on the surface charge and the amount of surface hydroxyl groups on red mud particles generated from different bauxite sources. It has been demonstrated that this can be used to quantify the surface properties of red mud particles. Red mud particles carry a significant negative charge under the basic conditions that

D Chvedov; S Ostap; T Le

2001-01-01

13

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

14

Potentiometric titration of gold, platinum, and some other precious metals  

SciTech Connect

Gold, platinum, and several other platinum metals can be determined by titration with cetylpyridinium chloride (CPC). CPC forms a precipitate with AuCl{sub 4}{sup {minus}} and PtCl{sub 6}{sup 2{minus}}. Differentiation of AuCl{sub 4{minus}} and PtCl{sub 6}{sup 2{minus}} with this titrant is not possible; however, their sum can be determined. Titration with tetraphenylarsonium chloride at pH 1 is selective for tetrachloroaurate, which thus can be determined in the presence of hexachloroplatinate. Hexachloroosmate(IV), tetrachloroplatinite(II), tetrachloropalladate(II), hexachloropalladate(IV), and hexachloroiridate(IV) can also be determined potentiometrically vs. CPC. The indicating electrode is prepared by coating a spectroscopic graphite rod with a solution of poly(vinyl chloride) (PVC) and dioctylphthalate (DOP) in tetrahydrofuran (THF). Gold in gold cyanide plating baths and in potassium aurocyanide can be determined by potentiometric titration vs standard silver nitrate, using a silver ion-selective indicating electrode. The monovalent gold need not be converted to the trivalent state with aqua regia, resulting in a considerable saving of time and effort. Free cyanide and aurocyanide can be titrated sequentially by this method. Chloride does not interfere and can, in fact, also be sequentially determined. 17 refs., 2 figs., 3 tabs.

Selig, W.S.

1991-02-04

15

Derivative analysis of potentiometric titration data to obtain protonation constants  

SciTech Connect

A methodology is described to calibrate glass electrodes and to analyze potentiometric titration data to calculate protonation constants. The analysis uses the variation of dV/dpH with titrant addition in terms of two physical parameters which involve the concentrations of H{sup +}, OH{sup -}, and H{sub m}A. The data for titration of acetic acid and 8-hydroxyquinoline in 0.10-5.0 m NaCl media are analyzed by this method to obtain the stoichiometric protonation constants of the acids, the ionization constants of water, and the parameters s and b in the pH electrode calibration equation, pcH = spH{sub m} + b, where pcH = -log[H{sup +}], pH{sub m} is the pH meter reading. 31 refs., 3 figs., 6 tabs.

Chen, J.F.; Xia, Y.X.; Choppin, G.R. [Florida State Univ., Tallahassee, FL (United States)] [Florida State Univ., Tallahassee, FL (United States)

1996-11-15

16

Computer-processed potentiometric titration for the determination of calcium and magnesium in sea water  

Microsoft Academic Search

An improved potentiometric titration method for the determination of calcium and magnesium in sea water has been newly devised. In this method, a mini-computer is used for the automation of titrations, and ion-selective electrodes are used as an end-point detector. Calcium is determined by titration with EGTA, and total alkaline earth metals (magnesium + calcium + strontium) by titration with

Satoru Kanamori; Hisashi Ikegami

1980-01-01

17

Continuous on-line true titrations by feedback based flow ratiometry: application to potentiometric acid–base titrations  

Microsoft Academic Search

We applied the methodology of continuous titrations by feedback-based flow ratiometry and the principle of compensating errors [Anal. Chem. 72 (2000), 4713] to potentiometric acid–base titrations. In a typical case, the titrant (a standard base) flow (FB) is varied in response to a controller output voltage, while the total flow (FT, consisting of an acid sample and the titrant flow)

Purnendu K Dasgupta; Hideji Tanaka; Kyoo Dong Jo

2001-01-01

18

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

Microsoft Academic Search

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

Katsutoshi Sakurai; Yohichi Ohdate; Kazutake Kyuma

1989-01-01

19

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

20

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

21

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

Microsoft Academic Search

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

Katsutoshi Sakurai; Yohichi Ohdate; Kazutake Kyuma

1988-01-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

23

Differential potentiometric titration: development of a methodology for determining the point of zero charge of metal (hydr)oxides by one titration curve.  

PubMed

A new methodology is presented, called differential potentiometric titration (DPT), which allows the determination of the point of zero charge (pzc) of metal (hydr)oxides using only one potentiometric curve. By performing extensive simulations of potentiometric titrations for various model (hydr)oxides, we found that an inflection point in a H+(cons,surf) versus pH potentiometric curve (H+(cons,surf): hydrogen ions consumed on the surface of the (hydr)oxide) and a peak in the corresponding differential curve, dH+(cons,surf)/dpH versus pH, appear at a pH equal to the pzc assumed for a model (hydr)oxide. This distinguishable peak appears at the same position irrespective of the surface ionization and the interfacial model adopted as well as the assumed ionic strength. It was found that the aforementioned peak also appears in the high-resolution differential potentiometric curves experimentally determined for four oxides (SiO2, TiO2, gamma-Al2O3, and MgO) that are widely used in various environmental and other technological applications. The application of DPT to the above-mentioned oxides provided practically the same pzc values as the corresponding ones achieved by using four different techniques as well as the corresponding isoelectric point (iep) values determined by microelectrophoresis. Differences between the pzc and iep values determined using various techniques in the case of MgO were attributed to the increasing dissolution of this oxide as pH decreases and the adsorption of cations (Mg2+, Na+) on the MgO/electrolytic solution interface. PMID:15984788

Bourikas, Kyriakos; Kordulis, Christos; Lycourghiotis, Alexis

2005-06-01

24

Reliable pKw values from potentiometric titrations: the striking effect of the titration final added volume.  

PubMed

Errors affecting the estimation of the ionic product of water from the potentiometric titration of weak acids have been analysed. A Fortran programme has been developed in order to simulate experimental titration data sets. This programme allows one to isolate experimental error sources and analyse their effect upon the final fitted equilibrium constant. pKw dependence with titration final added volume and the pK value of the weak acid, predicted with the simulation programme are coincident with experimental data, suggesting that obtaining reliable pKw values entails using experimental data of titrations up to a sufficiently large hydroxyl concentration which depends on the value of pK. PMID:11770160

Brandariz, I; Vilariño, T; Barriada, J L; Sastre De Vicente, M E

2001-01-01

25

Artificial neural networks applied to potentiometric acid–base flow injection titrations  

Microsoft Academic Search

Artificial neural network (ANN) was applied for data treatment as a multivariate calibration tool in a potentiometric acid–base flow injection titration. A multilayer feed-forward ANN model, with Levenberg–Marquardt weight error correction was used for data modeling. The neural network parameter architecture was optimized to establish a relationship between the titration profile and the acid concentration. Citric and malic acids in

Cleidiane G Zampronio; Jarbas J. R Rohwedder; Ronei J Poppi

2002-01-01

26

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

27

Potentiometric titration of bisarenechromium compounds with an ion-selective electrode  

SciTech Connect

A liquid-membrane ion-selective electrode was developed for determining bisbenzene-chromium and its electrochemical and analytical characteristics studied. Methods have also been developed for determining bisarenechromium compounds in the industrial product and its waste waters by potentiometric titration with sodium tetraphenylborate solution.

Gur'ev, I.A.; Gur'eva, Z.M.; Sankova, E.V.; Sirotkin, N.I.

1986-06-10

28

A new linear potentiometric titration method for the determination of deacetylation degree of chitosan  

Microsoft Academic Search

The degree of deacetylation (DD) is one of the most important properties of chitosan. Therefore, a simple, rapid and reliable method for the determination of DD of chitosan is essential. In this report, two new potentiometric titration functions are derived for the determination of DD of chitosan. The effects of the precipitation and the errors induced in pH measurement are

Xuan Jiang; Lirong Chen; Wei Zhong

2003-01-01

29

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

Microsoft Academic Search

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

1977-01-01

30

Potentiometric Measurement of Transition Ranges and Titration Errors for Acid/Base Indicators  

NASA Astrophysics Data System (ADS)

Sophomore analytical chemistry courses typically devote a substantial amount of lecture time to acid/base equilibrium theory, and usually include at least one laboratory project employing potentiometric titrations. In an effort to provide students a laboratory experience that more directly supports their classroom discussions on this important topic, an experiment involving potentiometric measurement of transition ranges and titration errors for common acid/base indicators has been developed. The pH and visually-assessed color of a millimolar strong acid/base system are monitored as a function of added titrant volume, and the resultant data plotted to permit determination of the indicator's transition range and associated titration error. Student response is typically quite positive, and the measured quantities correlate reasonably well to literature values.

Flowers, Paul A.

1997-07-01

31

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

32

Potentiometric titration of sulfate with lead and barium ions with various indicating electrodes  

SciTech Connect

Several types of graphite were used as sensors in the potentiometric titration of 25 to 75 ..mu..mol of sulfate vs. lead(II) and barium(II) and compared with titrations obtained with a lead ion-selective electrode (ISE). Pyrolytic graphite and high-density graphite, conditioned in neutral potassium permanganate, were found to be good alternatives to the lead ISE. A qualitative study was made of a variety of commercially available ISE's and other materials as sensors in the titration of 5 ..mu..mol of sulfate vs lead(II). Every ISE and conducting material tested yielded a usable response. While that of the commonly used lead ISE was largest, some other ISE's and metal rods also function satisfactorily as sensors in this titration. All titrations were carried out in a partially nonaqueous medium, which is required even for the lead ISE at the low sulfate levels investigated. 18 references, 4 figures, 5 tables.

Selig, W.S.

1984-01-01

33

Nonaqueous potentiometric titration and elemental analysis of high-boiling distillates of Saudi Arabian crude oils  

SciTech Connect

Nonaqueous potentiometric titration and elemental analysis were used to study basic and nonbasic functionalities present in high-boiling distillates of four Saudi Arabian crude oils. Model nitrogen compounds were titrated under similar titration conditions to differentiate them into strong, weak and nonbasic species. The strong bses titrated were due to the presence of of pyridine and its benzologs like acridines, phenanthridines and quionolines. The weak bases titrated were due to phenazxines and amides whereas the pyrroles, indoles and carbazoles were found to be nonbasic in nature. The total nitrogen and the total basic nitrogen compounds were generally found to be in very low concentration in the four crude oil distillates. A gradual decrease in the basicity of the distillates was found from Arab Heavy to Arab Extra Light through Arab Medium and Arab Light crude oils.

Ali, M.F.; Ali, M.A. (Dept. of Chemistry, King Fahd Univ. of Petroleum and Minerals, Dhahran 31261 (SA))

1988-12-01

34

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

PubMed

In the present paper, the utility of a special potentiometric titration approach for recognition and calculation of biomolecule/small-molecule interactions is reported. This approach is fast, sensitive, reproducible, and inexpensive in comparison to the other methods for the determination of the association constant values (Ka) and the interaction energies (?G). The potentiometric titration measurement is based on the use of a classical polymeric membrane indicator electrode in a solution of the small-molecule ligand. The biomolecule is used as a titrant. The potential is measured versus a reference electrode and transformed into a concentration-related signal over the entire concentration interval, also at low concentrations, where the millivolt (y-axis) versus log canalyte (x-axis) potentiometric calibration curve is not linear. In the procedure, Ka is calculated for the interaction of cocaine with a cocaine binding aptamer and with an anticocaine antibody. To study the selectivity and cross-reactivity, other oligonucleotides and aptamers are tested, as well as other small ligand molecules such as tetrakis(4-chlorophenyl)borate, metergoline, lidocaine, and bromhexine. The calculated Ka compared favorably to the value reported in the literature using surface plasmon resonance. The potentiometric titration approach called "concentration-related response potentiometry" is used to study molecular interaction for seven macromolecular target molecules and four small-molecule ligands. PMID:25390494

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

2014-12-16

35

Stabilization of the initial electrochemical potential for a metal-based potentiometric titration study of a biosorption process.  

PubMed

An interactive metal-based potentiometric titration method has been developed using an ion selective electrode for studying the sorption of metal cations. The accuracy of this technique was verified by analyzing the metal sorption mechanism for the biomass of Rhizopus arrhizus fungus and diatomite, two dissimilar materials (organic and mineral, strong sorbent and weak sorbent) of a different order of cation exchange capacity. The problem of the initial electrochemical potential was addressed identifying the usefulness of a Na-sulfonic resin as a strong chelating agent applied before the beginning of sorption titration experiments so that the titration curves and the sorption uptake could be quantitatively compared. The resin stabilized the initial electrochemical potential to -405+/-5 mV corresponding to 2 micro gl(-1) of lead concentration in solution. The amounts of lead sorbed by R. arrhizus biomass and diatomite were 0.9 mmol g(-1) (C(e)=5.16 x 10(-2)mM) and 0.052 mmol g(-1) (C(e)=5.97 x 10(-2) mM), respectively. Lead sorption by the fungal biomass was pinpointed to at least two types of chemical active sites. The first type was distinguished by high reactivity and a low number of sites whereas the other was characterized by their higher number and lower reactivity. PMID:16325652

Naja, Ghinwa; Mustin, Christian; Volesky, Bohumil; Berthelin, Jacques

2006-01-01

36

The potentiometric titration of fluoride using pH electrodes  

SciTech Connect

Sodium fluoride solutions with an initial pH of 4.46 yielded poorly defined endpoint breaks with a pH electrode system and Ce(III) or La(III) as titrants. At this initial pH, however, the fluoride ISE yielded acceptable S-shaped titration curves. At an initial pH of 6.30, both electrode systems and titrant combinations yielded acceptable endpoint breaks and titration curves. While a partially nonaqueous medium (50% methanol) enhanced the steepness of the endpoint breaks, the standard deviation also increased. This was possibly caused by evaporation of some of the solvent. We therefore do not see the necessity for, nor recommend a partially nonaqueous medium. There is no advantage in using Ce(III) rather than La(III) as titrant. Increasing the initial pH from 4.46 to 6.3 decreased the mean normality of the titrant (or increased the titration volume) for both electrode systems and titrants. We therefore recommend that the sodium fluoride standard solutions be adjusted to the same pH as the samples to be determined. For the most accurate results, the standardization should be done with a good approximation of the salt content of the unknown solution.

Selig, W.S.

1987-07-01

37

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

PubMed

A method was developed to analyze the distribution of sulfur compounds in model sulfur compounds by potentiometric titration, and applied to analyze hydrotreated transformer base oil. Model thioethers were oxidized to corresponding sulfoxides by tetrabutylammonium periodate and sodium metaperiodate, respectively, and the sulfoxides were titrated by perchloric acid titrant in acetic anhydride. The contents of aliphatic thioethers and total thioethers were then determined from that of sulfoxides in solution. The method was applied to determine the organic sulfur compounds in hydrotreated transformer base oil. PMID:15984215

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

2005-06-01

38

Potentiometric Titration of Industrial Samples—End-point Detection by Means of Wavelets  

NASA Astrophysics Data System (ADS)

A continuous wavelet transform with a specially defined dedicated mother wavelet is applied for data treatment as a signal-processing tool in a potentiometric titration. The inflection points of the titration curve are localized in one step of the calculations. The imperfection of signal, random noise, or spikes has no influence on the operation of the procedure. The proposed algorithm does not require any prior information about the nature or the type of analyte and/or the shape of the titration curve. Although the optimization of transformation parameters should be done, they may be chosen from a wide interval. The accuracy and precision of the proposed end-point estimation is examined on several simulated curves and instrumental potentiometric titrations. Under normal working conditions, analyte concentrations with variation coefficients between 1% and 5% have been determined. The procedure based on the wavelets provides an objective criterion for the determination of the end point. It can be reproduced and fully automated, thus contributing to a more versatile titration analysis.

Jakubowska, M.; Ba?, B.; Niewiara, E.; Reczy?ski, W.; Kubiak, W. W.

2009-08-01

39

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

40

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

41

Persistence length of carboxymethyl cellulose as evaluated from size exclusion chromatography and potentiometric titrations  

Microsoft Academic Search

The intrinsic persistence length of carboxymethyl cellulose (CMC) is determined by size exclusion chromatography in combination with multiangle laser light scattering (SEC-MALLS) as well as from potentiometric titrations. Samples with degree of substitution (ds) ranging from 0.75 to 1.25 were investigated. The relation between molar mass M and radius of gyration Rg as obtained by SEC-MALLS is determined in 0.02,

C. W. Hoogendam; A. de Keizer; M. A. Cohen Stuart; B. H. Bijsterbosch; J. A. M. Smit; Dijk van J. A. P. P; Horst van der P. M; J. G. Batelaan

1998-01-01

42

Thermodynamic dissociation constants of codeine, ethylmorphine and homatropine by regression analysis of potentiometric titration data  

Microsoft Academic Search

Concentration and mixed dissociation constant(s) of three drug acids HJL, codeine, ethylmorphine and homatropine, at various ionic strengths I in the range of 0.03–0.81 have been determined with the use of regression analysis of potentiometric titration data when common parameters (pKa,j, j=1,…,J), and group parameters (E0?, L0, HT) are simultaneously refined. Reliability of the dissociation constant(s) should be proven because

Milan Meloun; Marta Pluha?ová

2000-01-01

43

Optimization of a novel two-phase potentiometric titration method of barbiturates with mercury (II). Part II: Experimental evaluation.  

PubMed

A two-phase potentiometric titration procedure of barbiturates with mercury(II) was developed. The composition of the formed mercury-barbiturate complexes was elucidated by infrared spectrometry. In the new titration procedure the barbituric acid derivative is dissolved in an aqueous borate buffer. An organic phase consisting of chloroform and benzyl alcohol is added, and the vigorously stirred contents of the titration vessel are titrated by a mercury(II) nitrate solution. In the potentiometric determination of the end-point a rotating mercury electrode is used as an indicator electrode that also serves as an efficient stirrer. The two-phase procedure was compared with a one-phase mercurimetric potentiometric titration in borate buffer and with the potentiometric titration by sodium hydroxide in an ethanol-water solution. The proposed two-phase procedure is superior to both methods because lower concentrations of barbiturates (10(-3) - 10(-4) M) can be determined successfully. The one-phase procedure suffers from systematic errors, while the titration with sodium hydroxide is less precise at concentration levels of the barbiturates prevailing in content uniformity studies. By the two-phase procedure the direct titration of phenobarbital and mephobarbital in a dry mix of tablet excipients was possible with a relative standard deviation smaller than 1.5 percent. PMID:6646992

Coenegracht, P M; Metting, H J; Doornbos, D A

1983-10-21

44

Simultaneous determination of equivalence volumes and acid dissociation constants from potentiometric titration data.  

PubMed

New iterative methods for analysis of potentiometric titration data of (a) mixtures of weak monoprotic acids with their conjugate bases, (b) solutions of polyprotic (di- and triprotic) acids, and (c) mixtures of two diprotic acids are presented. These methods, using data exclusively resulting from the acidic region of the titration curve permits the accurate determination of the analytical concentration of one or more acids even if the titration is stopped well before the end point of the titration. For the titration of a solution containing a conjugate acid/base pair, the proposed procedure enables the extraction of the initial composition of the mixture, as well as the dissociation constant of the concerned acid. Thus, it is possible by this type of analysis to distinguish whether a weak acid has been contaminated by a strong base and define the extent of the contamination. On the other hand, for the titration of polyprotic acids, the proposed approach enables the extraction of the accurate values of the equivalence volume and the dissociation constants K(i) even when the ionization stages overlap. Finally, for the titration of a mixture of two diprotic acids the proposed procedure enables the determination of the composition of the mixture even if the sum of the concentrations of the acids is not known. This method can be used in the analysis of solutions containing two diastereoisomeric forms of a weak diprotic acid. The test of the proposed procedures by means of ideal and Monte Carlo simulated data revealed that these methods are fairly applicable even when the titration data are considerably obscured by 'noise' or contain an important systematic error. The proposed procedures were also successfully applied to experimental titration data. PMID:18966298

Papanastasiou, G; Ziogas, I

1995-06-01

45

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

Microsoft Academic Search

To provide constraints on the speciation of bacterial surface functional groups, we have conducted potentiometric titrations using the gram-positive aerobic species Bacillus subtilis, covering the pH range 2.1 to 9.8. Titration experiments were conducted using an auto-titrator assembly, with the bacteria suspended in fixed ionic strength (0.01 to 0.3 M) NaClO4 solutions. We observed significant adsorption of protons over the

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

2005-01-01

46

Physicochemical studies on BELGARD EV and BELGARD EV 2000 solutions. Part II. Potentiometric and conductometric acid-base titrations  

Microsoft Academic Search

The two anti-scale agents BELGARD EV (BELEV) and BELGARD EV 2000 (BELEV 2) are titrated against standard NaOH solution. Both the potentiometric (pH metric) and the conductometric titration techniques are used. For the sake of comparison the reaction of the monomer (maleic acid, H2M) is also investigated. The two titration techniques reveal that H2M neutralizes along two equal steps. The

A. M. Shams El Din; R. A. Mohammed

1996-01-01

47

Standard test method for total base number of petroleum products by potentiometric perchloric acid titration  

SciTech Connect

This method covers the determination of basic constituents in petroleum products by titration with perchloric acid. For many materials the results obtained by this method will be similar to those obtained by Method D 664-IP 177. With certain compounds such as strongly overbased oil additives and nitrogenous polymeric compounds, higher results may be obtained. Summary of method: the sample is dissolved in an essentially anhydrous mixture of chlorobenzene and glacial acetic acid and titrated with a solution of perchloric acid in glacial acetic acid with a potentiometric titrimeter. A glass indicating electrode and a calomel reference electrode are used, the latter being connected with the sample solution by means of a salt bridge. The meter readings are plotted against the respective volumes of titrating solution, and the end point is taken at the inflection in the resulting curve. Occasionally certain used oils give no inflection in the standard titration, in which case a back titration modification with sodium acetate titrant is employed. Total base number is the quantity of perchloric acid expressed in terms of the equivalent number of milligrams of potassium hydroxide that is required to neutralize all basic constituents present in 1 g of sample.

Not Available

1980-01-01

48

Studies on fluorescein-III The acid strengths of fluorescein as shown by potentiometric titration.  

PubMed

Potentiometric back-titration of yellow solid fluorescein (H(2)Fl) and of red solid fluorescein in alkali with acid yielded titration curves that were practically identical in shape and position. The end-points at pH 8.5, 5.40 and 3.3 corresponded, respectively, to titration of the excess of standard alkali, and the successive protonations Fl(2-) + H(+) = HFl(-) and HFl(-) + H(+) = H(2)Fl. The pH at the mid-point of the first protonation yielded a value of 6.36 for pK(HFl) (ionic strength 0.10). Because of precipitation of yellow fluorescein during the second protonation step, a value for pK(H(2)Fl) could not be obtained. The total concentration of fluorescein at the first appearance of the precipitate fell on the curve for the solubility of yellow fluorescein as a function of pH. The titrations and the pK values found for the three acid groups of protonated fluorescein (H(3)Fl(+)) have been interpreted on the basis that in water fluorescein exists in only one structural form the yellow zwitterion. Similar back-titrations of alkalinized solutions of yellow or red fluorescein in 50% aqueous ethanol showed that in this medium fluorescein is present in only one form, presumably the quinonoid structure, with much weaker apparent acid functions, pK'(1) = 6.38 and PK'(2) = 7.16 (ionic strength 0.10). PMID:18964223

Diehl, H; Horchak-Morris, N; Hefley, A J; Munson, L F; Markuszewski, R

1986-11-01

49

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

PubMed

A simple and rapid potentiometric method for the estimation of ascorbic acid in pharmaceutical dosage forms has been developed. The method is based on treating ascorbic acid with iodine and titration of the iodide produced equivalent to ascorbic acid with silver nitrate using Copper Based Mercury Film Electrode (CBMFE) as an indicator electrode. Interference study was carried to check possible interference of usual excipients and other vitamins. The precision and accuracy of the method was assessed by the application of lack-of-fit test and other statistical methods. The results of the proposed method and British Pharmacopoeia method were compared using F and t-statistical tests of significance. PMID:14709865

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

2004-01-01

50

The binding of aluminum to mugineic acid and related compounds as studied by potentiometric titration.  

PubMed

The phytosiderophores, mugineic acid (MA) and epi-hydroxymugineic acid (HMA), together with a related compound, nicotianamine (NA), were investigated for their ability to bind Al(III). Potentiometric titration analysis demonstrated that MA and HMA bind Al(III), in contrast to NA which does not under normal physiological conditions. With MA and HMA, in addition to the Al complex (AlL), the protonated (AlLH) and deprotonated (AlLH(-1)) complexes were identified from an analysis of titration curves, where L denotes the phytosiderophore form in which all the carboxylate functions are ionized. The equilibrium formation constants of the Al(III) phytosiderophore complexes are much smaller than those of the corresponding Fe(III) complexes. The higher selectivity of phytosiderophores for Fe(III) over Al(III) facilitates Fe(III) acquisition in alkaline conditions where free Al(III) levels are higher than free Fe(III) levels. PMID:21350950

Yoshimura, Etsuro; Kohdr, Hicham; Mori, Satoshi; Hider, Robert C

2011-08-01

51

Potentiometric study of reaction between periodate and iodide as their tetrabutylammonium salts in chloroform. Application to the determination of iodide and potentiometric detection of end points in acid-base titrations in chloroform  

Microsoft Academic Search

A potentiometric method for the titration of tetrabutylammonium iodide (TBAI) in chloroform using tetrabutylammonium periodate (TBAPI) as a strong and suitable oxidizing reagent is described. The potentiometric conditions were optimized and the equilibrium constants of the reactions occurring during the titration were determined. The method was used for the determination of iodide both in chloroform and aqueous solutions after extraction

M. H. Pournaghi-Azar; Kh. Farhadi

1995-01-01

52

Spectrophotometric study and potentiometric titration between sulfite and nitrite ions using acetaldehyde complex of nitroprusside as a carrier  

SciTech Connect

A complex between sodium nitroprusside (NP) and acetaldehyde of 1:1 in aqueous solution of pH 10 has been prepared and used as an analytical reagent for the spectrophotometric determination of sulfite and nitrite ions. Nitrite ion can be titrated against sulfite ion and vise versa in equivalent amounts with high accuracy in the presence of the acetaldehyde complex of nitroprusside as a carrier using a potentiometric titration technique. 9 references, 3 figures, 2 tables.

Ahmed, Y.Z.; Abd-Elmottalb, M.

1985-11-01

53

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

SciTech Connect

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

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

1997-03-01

54

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

SciTech Connect

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

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

2013-02-01

55

Surface Chemistry of Activated Carbons: Combining the Results of Temperature-Programmed Desorption, Boehm, and Potentiometric Titrations  

Microsoft Academic Search

Three samples of activated carbon were used for this study: two of wood and one of coal origin. The samples were further oxidized to study the effect of oxidation on the surface chemistry. The surface chemistry was characterized by using Boehm and potentiometric titrations, temperature-programmed desorption (TPD), and DRFTS. The results showed that oxidation introduces a variety of functional groups

Issa I. Salame; Teresa J. Bandosz

2001-01-01

56

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

PubMed

A chemically modified electrode (CME) was prepared and studied as a potentiometric sensor for the end-point detection in the automatic titration of vanadium(V) with EDTA. The CME was constructed with a paste prepared by mixing spectral-grade graphite powder, Nujol oil and N-2-naphthoyl-N-p-tolylhydroxamic acid (NTHA). Buffer systems, pH effects and the concentration range were studied. Interference ions were separated by applying a liquid-liquid extraction procedure. The CME did not require any special conditioning before using. The electrode was constructed with very inexpensive materials and was easily made. It could be continuously used, at least two months without removing the paste. Automatic potentiometric titration curves were obtained for V(V) within 5 x 10(-5) to 2 x 10(-3)M with acceptable accuracy and precision. The developed method was applied to V(V) determination in alloys for hip prosthesis. PMID:18970248

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

2005-10-15

57

Near infrared spectral changes of cytochrome aa3 during potentiometric titrations.  

PubMed Central

Singular value decomposition (SVD) was used to deconvolute the spectral changes occurring in the near infrared region during potentiometric titrations of cytochrome aa3. Overall oxidized minus reduced difference spectra revealed a broad absorbance feature centered near 830 nm with an apparent Em near 250 mV. However, SVD did not isolate any spectral species with an absorbance centered near 830 nm. It was found that the spectral changes occurring in the wavelength region from 650 to 950 nm were associated mainly with cytochromes a and a3. It was concluded that the absorbance at 830 nm should not be used as an independent measure of the concentration of CuA in cytochrome aa3. PMID:7696488

Hendler, R W; Harmon, P A; Levin, I W

1994-01-01

58

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

PubMed

A FIA system using a pH-sensitive detector based on a graphite/quinhydrone/silicone composite electrode was applied to determine sequentially the titratable acidity and the pH of wine, as well as the sum of calcium and magnesium ions. For all measurements the same FIA configuration was used employing different carrier solutions. The results for the determination of acidity and pH are in good agreement with those obtained by classical potentiometric titrations and by pH measurements using a conventional glass electrode. The standard deviation was less than 1.5% for both kinds of measurements and the sample volume was 150 ?L. The method allows about 40 determinations of titratable acidity per hour and 30 pH measurements per hour. The titration method can be adjusted to the legal requirements in USA and Europe. PMID:23622536

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

2013-07-15

59

Comparison of HPLC, UV spectrophotometry and potentiometric titration methods for the determination of lumefantrine in pharmaceutical products.  

PubMed

This paper describes the development and evaluation of a HPLC, UV spectrophotometry and potentiometric titration methods to quantify lumefantrine in raw materials and tablets. HPLC analyses were carried out using a Symmetry C(18) column and a mobile phase composed of methanol and 0.05% trifluoroacetic acid (80:20), with a flow rate of 1.0ml/min and UV detection at 335nm. For the spectrophotometric analyses, methanol was used as solvent and the wavelength of 335nm was selected for the detection. Non-aqueous titration of lumefantrine was carried out using perchloric acid as titrant and glacial acetic acid/acetic anhydride as solvent. The end point was potentiometrically determined. The three evaluated methods showed to be adequate to quantify lumefantrine in raw materials, while HPLC and UV methods presented the most reliable results for the analyses of tablets. PMID:18571353

da Costa César, Isabela; Nogueira, Fernando Henrique Andrade; Pianetti, Gérson Antônio

2008-09-10

60

Analysis of acid-soluble chloride in cement, mortar, and concrete by potentiometric titration without filtration steps  

Microsoft Academic Search

A potentiometric titration procedure that makes use of Gran’s method for end-point detection has been developed to analyze acid-soluble chloride in cement, mortar, and concrete, eliminating the filtration steps performed in habitual laboratory reference methods. The accuracy and reliability of the proposed analytical technique has been checked against a standard method, such as Volhard’s, by analyzing duplicate samples of cements,

Miguel A. Climent; Estanislao Viqueira; Guillem de Vera; M. M. López-Atalaya

1999-01-01

61

Use of liquid ion-selective electrodes for the potentiometric titration of Ag(CN)/sub 2//sup -/ and Au(CN)/sub 2//sup -/  

SciTech Connect

During investigation of the effects of various cellulose films used in the construction of ion-selective electrodes (ISE) on the results from the determination of Ag(CN)/sub 2//sup -/ and Au(CN)/sub 2//sup -/ by precipitation potentiometric titration, it was established that the degree to which the cationic function of the ISE shows up increases and the potential drop increases with decrease in the thickness of the cellulose film. This makes it possible to determine the equivalence point and the concentrations of Ag(CN)/sub 2//sup -/ and Au(CN)/sub 2//sup -/ more accurately. Hydrated cellulose films produced from solutions of cellulose in ethyl acetate with thicknesses of 10-16 ..mu.. are the most suitable for the rapid analysis of silver-plating and gold-plating electrolytes.

Kaputskii, F.N.; Grinshpan, D.D.; Rakhman'ko, E.M.; Starobinets, G.L.; Sloboda, N.A.; Savitskaya, T.A.; Borovskii, E.S.

1986-12-20

62

Effect of dissolved oxygen on two bacterial pathogens examined using ATR-FTIR spectroscopy, microelectrophoresis, and potentiometric titration.  

PubMed

The effects of dissolved oxygen tension during bacterial growth and acclimation on the cell surface properties and biochemical composition of the bacterial pathogens Escherichia coli O157:H7 and Yersinia enterocolitica are characterized. Three experimental techniques are used in an effort to understand the influence of bacterial growth and acclimation conditions on cell surface charge and the composition of the bacterial cell: (i) electrophoretic mobility measurements; (ii) potentiometric titration; and (iii) ATR-FTIR spectroscopy. Potentiometric titration data analyzed using chemical speciation software are related to measured electrophoretic mobilities at the pH of interest. Titration of bacterial cells is used to identify the major proton-active functional groups and the overall concentration of these cell surface ligands at the cell membrane. Analysis of titration data shows notable differences between strains and conditions, confirming the appropriateness of this tool for an overall charge characterization. ATR-FTIR spectroscopy of whole cells is used to further characterize the bacterial biochemical composition and macromolecular structures that might be involved in the development of the net surficial charge of the organisms examined. The evaluation of the integrated intensities of HPO(2)(-) and carbohydrate absorption bands in the IR spectra reveals clear differences between growth protocols. Taken together, the three techniques seem to indicate that the dissolved oxygen tension during cell growth or acclimation can noticeably influence the expression of cell surface molecules and the measurable cell surface charge, though in a strain-dependent fashion. PMID:20438073

Castro, Felipe D; Sedman, Jacqueline; Ismail, Ashraf A; Asadishad, Bahareh; Tufenkji, Nathalie

2010-06-01

63

The determination of binding constants with a differential thermal and potentiometric titration apparatus. II. EDTA, EGTA and calcium.  

PubMed

A differential pH and thermal titrimeter has been used to determine the ionization constants of EDTA and EGTA as well as their calcium complexes. The intrinsic heat of binding is a constant for the pH range 2-11.5 for both substances and is found to be -5.4 kcal mol for EDTA and -7.9 kcal mol-1 for EGTA. The binding constants evaluated by fitting to the potentiometric curves and expressed as the log are 10.25 and 11.0, respectively. These values compare reasonably well to those reported in the literature. We have proposed that the binding of calcium occurs even at acid pH based on the pH drop observed at pH 2 when calcium is added, the reversibility of the thermal and the potentiometric curves, the lack of hysteresis upon rapid titration, the constancy of the intrinsic heat of binding and fitting of the entire potentiometric curves using the appropriate binding constants. PMID:3086421

Marini, M A; Evans, W J; Berger, R L

1986-03-01

64

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

SciTech Connect

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

Zarzycki, Piotr P.; Rosso, Kevin M.

2009-06-16

65

Uptake of metal ions by a new chelating ion exchange resin. Part 3: Protonation constants via potentiometric titration and solid state [sup 31]P NMR spectroscopy  

SciTech Connect

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 increasing hydrophilicity of the resin pores. In the present investigation, the protonation equilibria of the phosphonate groups in the resin are investigated via potentiometric titration and solid-state [sup 31]P NMR spectroscopy of the resin. Intrinsic equilibrium constants for the first two diphosphonate protonation reactions are pK[sub 4] = 10.47 and pK[sub 3] = 7.24. The last two protons added to the diphosphonate group are acidic having pK[sub a] values less than 2.5. These protonation constants are consistent with those reported previously for monomer analog 1,1-diphosphonic acids. This result implies that thermodynamic data available in the literature can be used to predict the relative affinity of the resin for polyvalent cations. 17 refs., 2 figs., 3 tabs.

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

1994-01-01

66

Potentiometric titrations in acetonitrile–water mixtures: evaluation of aqueous ionisation constant of ketoprofen  

Microsoft Academic Search

Non ideality of acetonitrile–water mixtures was studied from data on the excess of molar volumes and viscosities. pH and autoprotolisis constants were evaluated at the standard state of the mixed solvent from titrations of a strong acid with a strong base. In order to illustrate the evaluation of the aqueous ionisation constant of water insoluble compounds from pH titrations in

M. Ángeles Herrador; A. Gustavo González

2002-01-01

67

Automated Potentiometric Titrations in KCl/Water-Saturated Octanol: Method for Quantifying Factors Influencing Ion-Pair Partitioning  

PubMed Central

The knowledge base of factors influencing ion pair partitioning is very sparse, primarily because of the difficulty in determining accurate log PI values of desirable low molecular weight (MW) reference compounds. We have developed a potentiometric titration procedure in KCl/water-saturated octanol that provides a link to log PI through the thermodynamic cycle of ionization and partitioning. These titrations have the advantage of being independent of the magnitude of log P, while maintaining a reproducibility of a few hundredths of a log P in the calculated difference between log P neutral and log P ion pair (diff (log PN???I)). Simple model compounds can be used. The titration procedure is described in detail, along with a program for calculating pKa?? values incorporating the ionization of water in octanol. Hydrogen bonding and steric factors have a greater influence on ion pairs than they do on neutral species, yet these factors are missing from current programs used to calculate log PI and log D. In contrast to the common assumption that diff (log PN???I) is the same for all amines, they can actually vary more than 3 log units, as in our examples. A major factor affecting log PI is the ability of water and the counterion to approach the charge center. Bulky substituents near the charge center have a negative influence on log PI. On the other hand, hydrogen bonding groups near the charge center have the opposite effect by lowering the free energy of the ion pair. The use of this titration method to determine substituent ion pair stabilization values (IPS) should bring about more accurate log D calculations and encourage species-specific QSAR involving log DN and log DI. This work also brings attention to the fascinating world of nature’s highly stabilized ion pairs. PMID:19265385

2009-01-01

68

Hydrogen bonding and molecular association in 2-(quinuclidinium)-butyric acid bromide hydrate studied by X-ray diffraction, DFT calculations, FTIR and NMR spectroscopy, and potentiometric titration  

NASA Astrophysics Data System (ADS)

The structure of 2-(quinuclidinium)-butyric acid bromide hydrate (QNBu·H 2O·HBr, 3) has been determined by X-ray diffraction, DFT calculations and characterized by FTIR and NMR spectroscopy. Crystals of 3 are monoclinic, space group P2 1. The water molecule interacts with the carboxylic group of 2-(quinuclidinium)-butyric acid and with the bromide anion by the COOH⋯OH 2 and HOH⋯Br hydrogen bonds of 2.575(3) and 3.293(2) Å, respectively. The structures of monomer ( 4) and dimeric cation ( 5) of the title complex have been optimized by the B3LYP/6-31G(d,p) approach, yielding conformations consistent with this in the crystal. The solid-state FTIR spectra of 3 and its deuterated analogue have been measured and compared with the theoretical spectrum of 4. The assignments of the observed and predicted bands have been proposed. The molecule of 3 has a chiral center at the C(9) atom, which is responsible for the non-magnetically equivalence of the ?-ring and C(11)H 2 methylene protons in 1H NMR spectrum. The values of p Ka of quinuclidinium-acetate (quinuclidine betaine), 2-(quinuclidinium)-propionate and 2-(quinuclidinium)-butyrate have been determined by the potentiometric titration of their hydrohalides.

Dega-Szafran, Z.; Katrusiak, A.; Szafran, M.; Barczy?ski, P.

2010-06-01

69

Determination of sulphated glycosaminoglycans by automated potentiometric titration with simple coated-wire electrodes.  

PubMed

A method for the determination of sulphated glycosaminoglycans is based on their precipitation with (1-ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex), the excess of which is back-titrated with sodium tetraphenylborate. The titration is monitored by a simple coated-wire ion-selective electrode with a plasticized poly(vinyl chloride) membrane on aluminium wire. Under certain conditions the results are almost independent of the relative molecular mass of glycosaminoglycans. The method has been applied to the determination of the active ingredient in the pharmaceutical preparation, heparon injection. PMID:2490091

Dohnal, J; Vytras, K; Roubal, Z; Zemanová, I

1989-01-01

70

Determination of different valence forms of cerium in glasses using potentiometric titration  

SciTech Connect

This paper describes a potentiometric method for the quantitative determination of two cerium oxide forms--cerium dioxide and dicerium trioxide--in glasses where the oxides form a major constituent. The method uses hydroquinone as a reducing agent. Cerium valences are also determined. The sensitivity of the method is tested by analyzing known synthetic mixtures simulating the composition of the glasses. The method has been used to determine the total concentration of cerium and to monitor the redox regime in glass melting furnaces during the melting of cerium-containing glasses.

Chesnokova, S.M.; Danilova, I.Yu.; Andreev, P.A.

1987-09-01

71

An automated differential thermal and potentiometric titration apparatus for binding studies.  

PubMed

A differential pH-thermal titration apparatus is described which can detect pH differences with a sensitivity of +/- 0.0001 pH units and a thermal sensitivity of +/- 0.00002 degree C at a time constant of 0.1 s. With a reaction which yields 1 kcal mol-1, the current system can detect concentrations as low as 4 X 10(-6) M or, in a 2 ml volume, a total amount of 40 nmol. With a time constant of 0.1 s, the sensitivity is 20 +/- 4 micro degrees C. The experimental protocol is specified by a microprocessor and three modes of operation are possible: titration at constant rate of reagent addition, titration at variable rates of addition so that the contents of both cells are at either constant pH or at a constant temperature and variable rate when a rate of change is specified. Experimental data are collected in files, corrected for heat loss, initial baseline drift, and changes in volume. The final corrected data from the standardized run of 0.01338 M HCl in 0.2 M KCl at 25 degrees C calibrate the pH scale and yield the calorimetric conversion constants and pKw which are calculated and stored for subsequent corrections for the titration of an unknown acid or the measurement of binding constants and heats. PMID:3998380

Berger, R L; Cascio, H E; Davids, N; Gibson, C G; Marini, M; Thiebault, L

1985-03-01

72

Development of quinhydrone electrode in chloroform. Application to the determination of equilibrium constants of acid-base reactions and potentiometric titration of some amine drugs.  

PubMed

The optimum conditions for the functioning of quinhydrone electrode as acid indicator in chloroform was determined by voltammetric and potentiometric studies. This electrode was used for the determination of equilibrium constants of acid-base reactions and the potentiometric determination of the end point of acidimetric titrations of some amine drugs such as phenothiazinic derivatives in pharmaceutical preparations, after extraction into chloroform. The relative standard deviations of 20 mg of aliphatic amines, piperidine and piperazine substituted phenothiazines were 0.5, 0.7 and 1 % respectively. PMID:18965971

Pournaghi-Azar, M H; Ordoukhanian, J

1994-04-01

73

Titration  

NSDL National Science Digital Library

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.

David Smith

74

Hydrogen-Aluminum Clays: A Third Buffer Range Appearing in Potentiometric Titration  

Microsoft Academic Search

Wyoming montmorillonite (bentonite, particles 2 to 0.2 mu in diameter) treated with hydrogen-ion-saturated resin shows, on titration in 1N KNO3 with NaOH by a continuously recording instrument, a third buffer range between pH 5.5 and 7.6 in addition to the first range where exchangeable hydronium is neutralized and the second range where a reaction with exchangeable aluminohexahydronium, Al(OH2)6{}3+, occurs. The

U. Schwertmann; M. L. Jackson

1963-01-01

75

Study of Some Physicochemical Properties of Pillared Montmorillonites: AcidBase Potentiometric Titrations and Electrophoretic Measurements  

Microsoft Academic Search

The surface charges and the zeta potential ofa Na-montmorillonite (Na-mont) and two pillared montmorillonite (MP1 and MP2) samples with different aluminum contents were determined by poten- tiometric titrations and electrophoretic measurements. At pH > 9 the two pillared montmorillonite sam- ples showed zeta potentials similar to those of Na-mont, but at pH <8, the negative zeta potential shifted to lower

Marcelo J. Avena; RAOL CABROL; CARLOS P. DE PAULI

1990-01-01

76

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

77

A study of surface properties of calcium phosphate by means of photoacoustic spectroscopy (FT-IR/PAS), potentiometric titration and electrophoretic measurements  

NASA Astrophysics Data System (ADS)

The surface charge at the calcium phosphate/electrolyte interface is created as a result of the various reactions of surface groups and unequal adsorption of ions of an opposite charge from the solution. Photoacoustic spectroscopy (FT-IR/PAS) has been used for identification of different groups of hydroxy- apatite samples. A complementary study of electrical double layer properties was carried out using potentiometric titration and electrophoretic measurements.

Janusz, W.; Skwarek, E.; Pasieczna-Patkowska, S.; Slosarczyk, A.; Paszkiewicz, Z.; Rapacz-Kmita, A.

2008-02-01

78

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

79

Some aspects of the use of heteropoly anions in elemental analysis by simple potentiometric ion-pair formation-based titration.  

PubMed

The possibility of the use of heteropoly anions formed by addition of phosphate to the solutions of either molybdate or tungstate in the determination of phosphorus by the simple method of potentiometric titration was studied. The heteropoly anions are titrated on the ion-pairing principle using a titrant containing a lipophilic counter-ion, i.e. 1-(ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex), the titration being monitored by carbon paste electrode, although other liquid membrane-based electrodes can also be used. Calibration plots of the titrant end-point consumption vs. concentration are not linear, but allow one to evaluate the content of phosphorus. Similar procedures, when optimized, should be elaborated for determination of numerous other elements forming heteropoly anions. PMID:18967295

Vytras, K; Jezková, J; Skorepa, J

1998-08-01

80

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

81

Liquid-liquid interfaces as potentiometric ion-sensors-I The n-butanol-water interface as indicating sensor for the potentiometric titration of some acids and bases.  

PubMed

The property that liquid-liquid interfaces modify their electrical charge as a function of the composition of the two phases in contact has been used to detect the end-points in a series of acid-base titrations in the aqueous phase. Although the titration curves are not classical in shape, the equivalence points can be located if the solutions are not too dilute. Good results for concentrations down to 10(-3)N have been obtained. The electrode has a fast response. The influence of surface-active substances on the titration has also been investigated. PMID:18961135

Liteanu, C; Mio?cu, M

1972-07-01

82

Alkylated lariat ethers as solvent extraction reagents: Surveying the extraction of alkali metals by bis-t-octylbenzo-14-crown-4-acetic acid by use of potentiometric two-phase titration  

SciTech Connect

Two-phase potentiometric titrimetry was used to survey the extraction of alkali metal cations from aqueous chloride solution by the lipophilic, ionizable lariat ether bis-(t-octylbenzo)-14-crown-4-acetic acid (BOB14C4AA) in o-xylene. Analysis of the data indicates that ion-exchange extraction by the crown-carboxylic acid at low loading (i.e., low conversion of BOB14C4AA to its salt form) is stronger for lithium ion than for the other alkali metals. Little or no selectivity occurs at high loadings. In comparison with the long-chain carboxylic acid 2-methyl-2-heptylnonanoic acid (HMHN), BOB14C4AA extracts lithium and sodium at significantly lower pH; in the loading range of 0.1 to 0.7, the pH shift is 1.4-1.8 pH units for sodium ion and 1.7-2.3 pH units for lithium ion. The titration data are interpreted in terms of aggregated organic-phase species. In the case of lithium extraction, clear evidence was found for a species in which neutral BOB14C4AA participates in the organic-phase complexation of the metal cation.

Sachleben, R.A.; Moyer, B.A.; Case, F.I.; Garmon, S.A. [Oak Ridge National Lab., TN (United States)

1993-01-01

83

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

PubMed

Based on precise analysis of the acid-base equilibrium, a new approach in the treatment of experimental data from a potentiometric titration is proposed. A new general formula giving explicitly the relation V=f([H(+)]) is derived, valid for every acid-base titration, which includes mono- and polyfunctional protolytes and their mixtures. The present study is the first practical application of this formula for the simplest case, the analysis of one monofunctional protolyte. The collected mV data during the titration are converted into pH-values by means of an auto pH-calibration procedure, thus avoiding preliminary preparation of the measuring system. The mentioned pH-calibration method is applicable also in water-organic mixtures and allows the quantitative determination of sparingly soluble substances (particularly pharmaceuticals). The treatment of the data is performed by means of ready-to-use software products, which makes the proposed approach accessible for a wide range of applications. PMID:12560965

Maslarska, Vania; Tencheva, Jasmina; Budevsky, Omortag

2003-01-01

84

Potentiometric titration of fluoride without fluoride ion-selective electrodes. [Investigation of a variety of graphite materials and platinum as sensors  

SciTech Connect

Graphite and platinum sensors were investigated as indicators in the potentiometric titration of fluoride vs lanthanum(III) and thorium(IV). In every case a partially nonaqueous medium (60% methanol) yielded larger breaks than in aqueous solution, similar to the fluoride electrode. All the sensors yielded endpoint breaks which were smaller than those obtained with the vitreous carbon, pyrolytic graphite, and platinum sensors. Conditioning in neutral permanganate solution significantly enhanced the breaks for all types of graphite, except vitreous carbon. The break obtained with the platinum electrode can be enhanced by application of a polarizing current of 2.0 ..mu..A in the reducing direction. 18 references, 2 figures, 6 tables.

Selig, W.S.

1983-01-01

85

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

SciTech Connect

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

Kwok, Y.M.

1980-07-31

86

Humic substance charge determination by titration with a flexible cationic polyelectrolyte  

NASA Astrophysics Data System (ADS)

The anionic charge of humic substances (HS) plays a major role in the interaction of HS with other components. Therefore, the potential of the polyelectrolyte titration technique to obtain the charge density of HS in simple 1-1 electrolyte solutions has been investigated. Titrations are carried out with an automatic titrator combined with the "Mütek particle charge detector" which allows determination of the Mütek potential and the pH as a function of the added amount of titrant which is a solution of poly-diallyldimethylammonium chloride (polyDADMAC), a cationic strong polyelectrolyte. When the Mütek potential reverses its sign the iso-electric point (IEP) of the polyDADMAC-HS complex is reached. The polyDADMAC/HS mass ratio at the IEP gives information on the HS charge density and from the pH changes in solution an estimate of the charge regulation in the HS-polyDADMAC complex can be obtained. In general, for polyDADMAC-HS complexes an increase in the dissociation of the acid groups of HS is found (charge regulation). The charge regulation decreases with increasing concentration of 1-1 background electrolyte. Cation incorporation can be neglected at 1-1 electrolyte concentrations ? 1 mmol L -1 and a 1-1 stoichiometry exists between the polyDADMAC and HS charge. However, at these low salt concentrations the charge regulation is substantial. A detailed analysis of purified Aldrich humic acid (PAHA) at pH 5 and a range of KCl concentrations reveals that the anionic charge of PAHA in the complex increases at 5 mmol L -1 KCl by 30% and at 150 mmol L -1 KCl by 12%. On the other hand, increasing amounts of K + become incorporated in the complex: at 5 mmol L -1 KCl 5% and at 150 mmol L -1 KCl 24% of the PAHA charge is balanced by K +. By comparing at pH 5 the mass ratios polyDADMAC/PAHA in the complex at the IEP with the theoretical mass ratios of polyDADMAC/PAHA required to neutralize PAHA in the absence of charge regulation and K + incorporation, it is found that at 50 mmol L -1 KCl the extra negative charge due to the interaction between polyDADMAC and PAHA is just compensated by K + incorporation in the complex. Therefore, a pseudo 1-1 stoichiometry exists at about 50 mmol L -1 1-1 electrolyte concentration and only at this salt concentration polyDADMAC titrations and conventional proton titrations give identical results. Most likely this is also true for other HA samples and other pH values. For FA further study is required to reveal the conditions for which polyDADMAC and proton titrations give identical results.

Tan, Wen-Feng; Norde, Willem; Koopal, Luuk K.

2011-10-01

87

Color Indicator System for Acid–Base Titration in Aqueous Micellar Solutions of the Cationic Surfactant Tridecylpyridinium Bromide  

Microsoft Academic Search

Acid–base properties of sulfophthalein indicators were studied in aqueous micellar solutions of the cationic surfactant tridecylpyridinium bromide (TDPB). A multiple linear regression was proposed for predicting protolytic properties of the reagents of this series in micellar TDPB solutions. Conditions were found for the titrimetric determination of long-chain aliphatic carboxylic acids with the use of Xylenol Blue for detecting the titration

S. A. Kulichenko; S. A. Fesenko; N. I. Fesenko

2001-01-01

88

The Determination of the pKaof Multiprotic, Weak Acids by Analyzing Potentiometric Acid Base Titration Data with Difference Plots  

Microsoft Academic Search

This paper discusses the pKa determination of mono-, di-, and triprotic weak acids with the help of difference (Bjerrum) plots, and the effect of strong acid base concentration errors, ligand weight errors, and nonlinear electrode response. Experimental examples are given for the titration of an acidic heterocycle, as well as glycine, ethylenediamine, and tris(2-aminoethyl)amine (the last two after addition of

Arno Kraft

2003-01-01

89

Potentiometric Analysis of a Reaction System of Organic Acids  

Microsoft Academic Search

A new potentiometric titration method for the quantitative analysis of a reaction system of diprotonic organic acids is presented. The method uses the individual potentiometric titration data for cal- culating the dissociation constants. With this information a set of \\

Agustín Jaime Castro-Montoya; Manuel Herrera-Solano; Pedro Alberto Quintana-Hernández; Medardo Serna-González; Facultad de Ingeniería Química

2003-01-01

90

Potentiometric and voltammetric determination of methimazole  

Microsoft Academic Search

The determination of methimazole was investigated by potentiometric titration in an alkaline medium involving its reaction with iodine and square wave voltammetry (SWV) in 0.1 mol\\/l Tris–HCl buffer at pH 7.2. In potentiometric titration, the range of determination was 10–500 ?mol. A stoichiometric reaction was obtained within the concentration range 0.75–1.25 mol\\/l of sodium hydroxide by potentiometric titration. A linear

Mehmet Aslanoglu; Nesrin Peker

2003-01-01

91

Potentiometric determination of potassium cations using a nickel(II) hexacyanoferrate-modified electrode.  

PubMed

Electroactive nickel(II) hexacyanoferrate (NiHCF) thin film modified electrodes are effective potentiometric sensors for the determination of potassium ions. The NiHCF films are deposited onto glassy carbon electrodes by repetitive potential cycling in K(3)Fe(CN)(6)/NaNO(3)/Ni(NO(3))(2) solution. The modified electrodes exhibit a linear response to potassium ions in the concentration range 1x10(-3) to 2.0 mol dm(-3), with a near-Nernstian slope (45-49 mV per decade) at 25 degrees C. In the determination of potassium ion in syrups used for treatment of potassium deficiency, the NiHCF-modified electrode gave comparable results to those obtained using flame emission spectrophotometry. PMID:18967597

Mortimer, R J; Barbeira, P J; Sene, A F; Stradiotto, N R

1999-06-14

92

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

93

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

E-print Network

November 2004 Abstract The high-resolution potentiometric titration was used as a physico-chemical method Ltd. All rights reserved. Keywords: Gran's method; High-resolution potentiometric titration; Acidic and their polyelec- trolyte nature call for the application of the acid­base potentiometric titration method

Volesky, Bohumil

94

Determination of nickel by direct automatic potentiometric titration with EDTA and a chemically modified electrode based on a strong acid ion exchanger containing 4-(3,5-dichloro-2-pyridylazo)-1,3-diaminobenzene.  

PubMed

A chemically modified electrode (CME) was constructed and evaluated for use as an end-point indicator in the automatic titration of Ni(II) with EDTA. The CME consisted of a graphite paste prepared by mixing a strong acid ion exchanger containing 4-(3,5-dichloro-2-pyridylazo)-1,3-diaminobenzene and graphite powder-Nujol paste. This mixture showed high mechanical resistance in strongly acidic and alkaline solutions (6 M HCl-pH 12). The CME did not require any special conditioning prior to use. It could be used over long periods (5-6 months) of continuous work without renewing either the electroactive surface or paste. In buffered solutions (pH 3-4.5), automatic direct potentiometric titrations could be carried out over a wide interval of Ni(II) concentrations, ranging from 3 to 6000 ppm, with satisfactory accuracy and precision. For practical analysis, the electrode was applied to the determination of nickel in two certified composition alloys. Interferent ions were previously separated by applying an ion-exchange procedure. PMID:18966712

González, P S; Fontán, C A; Cortínez, V A

1997-01-01

95

FIA potentiometric and solvent extraction studies of alkali metal and alkaline earth cation complexation by bis(tert-butylbenzo)-21-crown-7  

SciTech Connect

A flow injection analysis study of the potentiometric selectivity of bis[4(5)-tert-butylbenzo]-21-crown-7 (D(tBB)21C7) for cesium over the other alkali metal cations and three alkaline earth cations has been conducted. A PVC matrix membrane containing D(tBB)21C7 as an ionophore was coated on the tip of a silver wire incorporated in a flow cell. No selectivity for cesium over rubidium and only low selectivity over potassium were noted. However, very high selectivities for cesium over sodium, lithium, strontium, calcium, and magnesium were observed. Selectivity of D(tBB)21C7 in the solvent extraction of alkali metal cations was determined by the picrate extraction method. The percent extraction into deuteriochloroform decreased in the order cesium, rubidium > potassium >> sodium >> lithium. Thus good agreement was observed between the responses of D(tBB)21C7 towards alkali metal cations in polymeric membrane electrodes and in solvent extraction. 19 refs., 1 fig., 3 tabs.

Attiyat, A.S. (Yarmouk Univ., Irbid (Jordan)); Christian, G.D. (Univ. of Washington, Seattle, WA (United States)); McDonough, J.A.; Strzelbicka, B.; Goo, M.J.; Yu, Z.Y.; Bartsch, R.A. (Texas Tech Univ., Lubbock, TX (United States))

1993-07-01

96

Determination of total fluoride in HF/HNO3/H2SiF6 etch solutions by new potentiometric titration methods.  

PubMed

In the photovoltaic industry the etching of silicon in HF/HNO(3) solutions is a decisive process for cleaning wafer surfaces or to produce certain surface morphologies like polishing or texturization. With regard to cost efficiency, a maximal utilisation of etch baths in combination with highest quality and accuracy is strived. To provide an etch bath control realised by a replenishment with concentrated acids the main constituents of these HF/HNO(3) etch solutions including the reaction product H(2)SiF(6) have to be analysed. Two new methods for the determination of the total fluoride content in an acidic etch solution based on the precipitation titration with La(NO(3))(3) are presented within this paper. The first method bases on the proper choice of the reaction conditions, since free fluoride ions have to be liberated from HF and H(2)SiF(6) at the same time to be detected by a fluoride ion-selective electrode (F-ISE). Therefore, the sample is adjusted to a pH of 8 for total cleavage of the SiF(6)(2-) anion and titrated in absence of buffers. In a second method, the titration with La(NO(3))(3) is followed by a change of the pH-value using a HF resistant glass-electrode. Both methods provide consistent values, whereas the analysis is fast and accurate, and thus, applicable for industrial process control. PMID:19071540

Weinreich, Wenke; Acker, Jörg; Gräber, Iris

2007-03-30

97

Hydrous ferric oxide: evaluation of Cd–HFO surface complexation models combining Cd K EXAFS data, potentiometric titration results, and surface site structures identified from mineralogical knowledge  

Microsoft Academic Search

The surface properties of ferrihydrite were studied by combining wet chemical data, CdK EXAFS data, and a surface structure and protonation model of the ferrihydrite surface. Acid–base titration experiments and Cd(II)–ferrihydrite sorption experiments were performed within 3

Lorenzo Spadini; Paul W. Schindler; Laurent Charlet; Alain Manceau

2003-01-01

98

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

99

LABORATORY EXPERIMENT 5 PRECIPITATION TITRATION WITH SILVER NITRATE.  

E-print Network

solution can be used for various titrations. I. Potentiometric Halide Titration with Ag+ MixturesLABORATORY EXPERIMENT 5 PRECIPITATION TITRATION WITH SILVER NITRATE. The AgNO3 solution (~0.02 M method with adsorption indicator and using Mohr method with chromate indicator. Both titrations

Nazarenko, Alexander

100

LABORATORY EXPERIMENT 4 Alkalimetric Titration of an Acid Mixture  

E-print Network

to semi-automatic volumetric analysis and potentiometric titrations. Phosphoric Acid, H3PO4 (pK1= 2.16, pLABORATORY EXPERIMENT 4 Alkalimetric Titration of an Acid Mixture In this experiment triprotic acid (H3PO4) will be determined by pH- potentiometric methods. This experiment will introduce you

Nazarenko, Alexander

101

Effect of different experimental parameters on the potentiometric evaluation of blood electrolytes using K+ as a test cation.  

PubMed

Potentiometric evaluation of ionic concentrations in physiological media has been reported to be significantly affected by the albumin containing matrix. Previous studies have attempted to clarify the origin of different patterns of variation of E versus albumin concentration at a constant 0.01 mol dm-3 KCl, depending on the experimental methodologies. This paper reports on measurements of K+ in albumin (BSA) containing KCl solutions, which have been pursued following different methodologies concerning the sequence of measurements, i.e., starting either from the most concentrated solution (100 g dm-3) (A) or from the most dilute solution (20 g dm-3) (B), and solution preparation, (a) dilution of an initial 100 g dm-3 albumin solution by successive addition of 0.01 mol dm-3 KCl, (b) concentration of an initial 20 g dm-3 albumin solution by addition of solid substance, (c) independent preparation of each albumin solution (20, 40, 60, 80 and 100 g dm-3) or (d) preparation of each albumin solution from direct dilution of a 100 g dm-3 stock solution with 0.01 mol dm-3 KCl. Convenient calculations were made and showed a significant contribution of albumin to the liquid-liquid junction potential. The variation of potential with albumin concentration is smaller for hypertonic than for isotonic bridge solutions, both for the dilution series (A,a and A,d) and for the concentration series (B,c and B,d). When the method for increasing the concentration is performed by addition of a solid substance to an initially diluted albumin (B,b), the slope of the E versus albumin concentration plot is larger for hypertonic than for isotonic reference electrolytes. This latter finding is in agreement with Payne's results when ultrafiltration was used to concentrate a protein solution. These observations are a clear indication that the method of preparation of concentrated protein solutions may significantly affect the results. PMID:9008407

Oliveira, C M; Rebelo, M J; Camões, M F

1996-12-01

102

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

103

Precipitation titration of perchlorate using new titrants  

SciTech Connect

We have evaluated the following new titrants for the potentiometric precipitation titration of perchlorate: cetyltrimethylammonium chloride (CETAC), cetyltrimethylammonium bromide (CETAB), cetylpyridinium chloride (CPC), and benzyldimethyltetradecylammonium chloride (BDTAC). Titrations were monitored with a fluoroborate ion-selective electrode (ISE) and a double-junction reference electrode. The titration system was controlled by a Tektronix 4051 graphics system. The perchlorate, nitrate, and calcium ISE may also be used to monitor emf's. 7 tables, 2 figures.

Selig, W.

1980-05-01

104

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

E-print Network

by potentiometric titration of ion-exchanged Hp. Conditions for complex formation with SA were qualitativelyBinding of Bovine Serum Albumin to Heparin Determined by Turbidimetric Titration and Frontal

Dubin, Paul D.

105

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

PubMed

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 potentiometric titrations were carried out on the montmorillonite fractions extracted from two bentonites (MX80 and SWy2) to quantify their protolytic charge. The effects of equilibration time (24 h and 7 days), pH from 4 to 10, and ionic strength (0.1 and 0.01 mol L(-1)) were extensively studied for the MX80 sample. Quantification of dissolution was achieved by analysis of the equilibrium solutions for dissolved species and by La(3+) exchange of the readsorbed species. The results clearly show that secondary phases such as iron- or silica-rich minerals contribute to the dissolved species, according to the nature of the raw bentonite. Furthermore, readsorption affects significant amounts of dissolved species. The overconsumption of proton/hydroxide due to dissolution, readsorption, and hydrolysis of dissolved species was evaluated using a self-consistent thermodynamic calculation. The ability of such calculation to correct the raw titration curves in order to extract the titrable surface charge of montmorillonite was evaluated by comparison with the continuous titration procedure. Especially in the alkaline domain, correcting the raw batch titration curves for the measured side reactions failed to reproduce the continuous titration curves. These observations demonstrate the limitations of the batch titration method and the superiority of fast, continuous methods for quantifying the dissociable surface charge of clays. PMID:16777124

Duc, Myriam; Thomas, Fabien; Gaboriaud, Fabien

2006-08-15

106

A hot-cell titration system  

SciTech Connect

Operation of nuclear fuel reprocessing plant requires an analytical support laboratory capable of meeting the process control, product quality, and nuclear safeguard requirements. Because of the radioactivity accompanying many of the samples, the analytical instruments must be selected, modified, or specifically developed for use in hot cells. Titrimetric procedures have been successfully used in hot cells and are generally immune to radiation induced bias. This report describes a titration system designed for operation in a hot-cell environment. The potentiometric titration system has operated successfully for four years in support of nuclear fuel reprocessing research and development activities. Details of the hardware, electronic, and software control and data analysis systems are presented. Interchangeable burets with a capacity of 5, 10, and 25 mL are available; the means of the absolute error in delivered volume for these burets are 0.9, 1.1, and 1.8 ..mu..L, respectively. Results of evaluation studies how that the accuracy and precision of analysis results obtained with the potentiometric system are limited by statistical uncertainties associated with the standard titrant, sample preparation procedure, and the equilibrium constant of the titration reaction and not by titrator performance factors. The system is also capable of performing amperometric titrations. Changing between the potentiometric and amperometric modes of operation involves changing the in-cell transducers, the in-cell electronics, and the titrator control program. 22 refs., 13 figs., 9 tabs.

Klatt, L.N.

1988-07-01

107

Linear titration plots for polyfunctional weak acids and bases.  

PubMed

Procedures are derived for obtaining the equivalence volumes in the potentiometric titrations of polyfunctional weak acids and weak bases by a linear titration plot method. The effect of errors in the equilibrium constants on the accuracy is considered. A Fortran program is available to do the calculations. PMID:18961862

Midgley, D; McCallum, C

1976-04-01

108

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

109

Titration Techniques  

NASA Astrophysics Data System (ADS)

Significant attention is paid to the proper technique for reading a meniscus. Video shows meniscus-viewing techniques for colorless and dark liquids and the consequences of not reading a meniscus at eye level. Lessons are provided on approaching the end point, focusing on end point colors produced via different commonly used indicators. The concept of a titration curve is illustrated by means of a pH meter. Carefully recorded images of the entire range of meniscus values in a buret, pipet, and graduated cylinder are included so that you can show your students, in lecture or pre-lab discussion, any meniscus and discuss how to read the buret properly. These buret meniscus values are very carefully recorded at the rate of one video frame per hundredth of a milliliter, so that an image showing any given meniscus value can be obtained. These images can be easily incorporated into a computer-based multimedia environment for testing or meniscus-reading exercises. Two of the authors have used this technique and found the exercise to be very well received by their students. Video on side two shows nearly 100 "bloopers", demonstrating both the right way and wrong ways to do tasks associated with titration. This material can be used in a variety of situations: to show students the correct way to do something; to test students by asking them "What is this person doing wrong?"; or to develop multimedia, computer-based lessons. The contents of Titration Techniques are listed below: Side 1 Titration: what it is. A simple titration; Acid-base titration animation; A brief redox titration; Redox titration animation; A complete acid-base titration. Titration techniques. Hand technique variations; Stopcock; Using a buret to measure liquid volumes; Wait before reading meniscus; Dirty and clean burets; Read meniscus at eye level (see Fig. 1); Meniscus viewing techniques--light colored liquids; Meniscus viewing techniques--dark liquids; Using a magnetic stirrer; Rough titration; Significant figures; Approaching the end point; End point colors; Titration with a pH meter; Titration curves; Colors of indicators. Meniscus values. Buret meniscus values; Pipet meniscus values; Graduated cylinder meniscus values. Side 2"Bloopers". Introducing the people; Titration animation; Inspecting the buret; Rinsing the buret with water; Preparing a solid sample; Obtaining a liquid sample; Delivering a liquid sample with a Mohr pipet; Pipetting a liquid sample with a Mohr pipet; Rinsing the Mohr pipet with sample; Using the Mohr pipet to transfer sample; Delivering a liquid sample with a volumetric pipet; Pipetting a liquid sample with a volumetric pipet; Rinsing the volumetric pipet with sample; Using the volumetric pipet to transfer sample; Obtaining the titrant; Rinsing the buret with titrant; Filling the buret with titrant; Adding the indicator; The initial reading; Beginning the titration; Delivering titrant; The final reading. Figure 3. Near the end point a single drop of titrant can cause a lasting color change.

Jacobsen, Jerrold J.; Houston Jetzer, Kelly; Patani, Néha; Zimmerman, John; Zweerink, Gerald

1995-07-01

110

Titration Techniques  

Microsoft Academic Search

Significant attention is paid to the proper technique for reading a meniscus. Video shows meniscus-viewing techniques for colorless and dark liquids and the consequences of not reading a meniscus at eye level. Lessons are provided on approaching the end point, focusing on end point colors produced via different commonly used indicators. The concept of a titration curve is illustrated by

Jerrold J. Jacobsen; Kelly Houston Jetzer; Néha Patani; John Zimmerman; Gerald Zweerink

1995-01-01

111

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

112

Microscale Titration in Schools Titration Competition.  

ERIC Educational Resources Information Center

Reviews the requirements of the National Titration Competition and describes how a team in a local competition used the technique. Compares microscale titration to conventional titration. Outlines the benefits of employing microscale techniques. (DDR)

Clark, Michael J.

1998-01-01

113

Potentiometric Studies of the Interaction of Bovine Serum Albumin and Poly(dimethyldiallylammonium chloride)  

E-print Network

: Potentiometric and turbidimetric titrations were used to study the interaction between bovine serum albumin (BSAPotentiometric Studies of the Interaction of Bovine Serum Albumin and PolyH. In the range of pHc titration and turbidimetry reveal the formation of soluble complexes. However

Dubin, Paul D.

114

Rapid determination of the equivalence volume in potentiometric acid-base titrations to a preset pH-II Standardizing a solution of a strong base, graphic location of equivalence volume, determination of stability constants of acids and titration of a mixture of two weak acids.  

PubMed

A newly proposed method of titrating weak acids with strong bases is applied to standardize a solution of a strong base, to graphic determination of equivalence volume of acetic acid with an error of 0.2%, to calculate the stability constants of hydroxylammonium ion, boric acid and hydrogen ascorbate ion and to analyse a mixture of acetic acid and ammonium ion with an error of 0.2-0.7%. PMID:18961474

Ivaska, A

1974-06-01

115

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

PubMed Central

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

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

2004-01-01

116

Potentiometric determination of anhydrous aluminum chloride  

SciTech Connect

Anhydrous aluminum chloride is a strong Lewis acid, widely used as a catalyst, in the synthesis and analysis of organic products. The aim of this article is to develop a potentiometric method of determining anhydrous AlCl/sub 3/. To estimate the validity of the results of the determination, use was made of French, Japanese, and Soviet samples of AlCl/sub 3/ with a known content of the main substance. The titration was performed in ethylene glycol. The procedure makes it possible to investigate the activity of AlCl/sub 3/ as a catalyst in different organic solvents

Kofman, A.G.; Chernysh, G.V.; Vorozhtsov, G.N.

1987-12-20

117

Interference by acetylated aminoacetic acid in nonaqueous titration of nicotinic acid.  

PubMed

A nonaqueous titration procedure is described for determining aminoacetic acid and nicotinic acid in mixtures and elixirs. The effect of acetylated aminoacetic acid on the potentiometric titration of nicotinic acid is discussed. Above a 2:1 ration of aminoacetic acid to nicotinic acid, the former interferes with titration. The titration curve of nicotinic acid becomes progressively flatter with increasing amounts of the acetylated compound. Above this ratio, nicotinic acid had to be separated from the mixture by dissolving in ethanol for a successful titration. PMID:893322

Soliman, S A; Abdine, H; Morcos, M G

1977-09-01

118

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

119

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

PubMed Central

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

120

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

121

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

122

Modern Directions for Potentiometric Sensors  

PubMed Central

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

2009-01-01

123

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

124

Potentiometric PVC membrane sensor for the determination of scopolamine in some pharmaceutical formulations.  

PubMed

A novel PVC membrane electrode for the determination of scopolamine ion based on the formation of an ion-association complex of scopolamine with the phosphotungstate counter anion as an electroactive material dispersed in a PVC matrix is described. The sensor shows a fast, stable, near-Nenstian response for 1 x 10(-2) mol dm(-3) to 1 x 10(-6) mol dm(-3) scopolamine at 25 degrees C over the pH range of 3 - 7 with a cationic slope of 54.5 +/- 0.5 mV/decade. The lower detection limit is 8 x 10(-7) mol dm(-3) and the response time is 15 -45 s. The selectivity coefficients for scopolamine relative to the number of interfering substances were investigated. There was negligible interference from the studied cations, anions, and pharmaceutical excipients. The determination of scopolamine in aqueous solution shows an average recovery of 100.0% and a mean relative standard deviation (RSD) of 1.5% at 500 microg/cm3. The direct determination of scopolamine in some formulations (scopolamine injection and eye drops) gave results that compare favorably with those obtained by the United State of Pharmacopoeia method. Potentiometric titration of scopolamine with sodium tetraphenylborate and phosphotungstic acid as a titrant was monitored with the developed scopolamine electrode as an end point indicator electrode. PMID:12502085

Mostafa, Gamal Abdel El-Hafeez

2002-12-01

125

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

126

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

127

ChemTeacher: Titration  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Titration page includes resources for teaching students about the theory and applications of titrations.

2012-07-24

128

Acid-base properties of the alumina surface: influence of the titration procedures on the microcalorimetric results.  

PubMed

The enthalpy changes associated with the protonation and deprotonation of an alumina surface have been determined on the basis of microcalorimetry experiments and acid-base potentiometric titrations at 25 degrees C. It has been shown that the results may vary significantly according to the experimental procedure. In order to do so, the potentiometric and microcalorimetric titrations have been carried out first from an acidic pH to basic pH and second from a pH near the pH(zpc) of alumina to acidic or basic pH. It has been demonstrated that the pK(a) values deduced from the potentiometric titrations are the same whatever the experimental protocol whereas the only way to obtain meaningful enthalpies of proton exchange is to carry out microcalorimetric titrations by starting around the point of zero charge. PMID:19643428

Morel, Jean-Pierre; Marmier, Nicolas; Hurel, Charlotte; Morel-Desrosiers, Nicole

2009-10-01

129

ACIDBASE TITRATION NUMERICAL SIMULATOR  

Microsoft Academic Search

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

Lorentz JÄNTSCHI; Delia GLIGOR; Mihaela Ligia

2003-01-01

130

[Potentiometric determination of halide ions in blood].  

PubMed

The authors have studied the possibility of using ion-selective electrodes Kritus (Czecho-Slovakia) for analysis of whole blood and serum without preliminary labor-consuming sample preparation. Chloride ions were found to be detectable in the blood serum by potentiometric titration with Ag nitrate solution making use of a pAg-CE-pF-CE pair in ethanol, acetone, or acetic acid medium. Active concentrations of whole blood and serum bromide- and iodide ions may be measured by direct potentiometry with pBr-CE-pF-CE and pI-CE-pF-CE pairs, respectively, against the background of 1 M potassium (or sodium) nitrate solution providing the constancy of solution ionic strength. PMID:7953129

Arkhangel'skaia, A S; Khomik, L I

1994-01-01

131

Acid — base titrations of barbiturates in aqueous micellar Media  

Microsoft Academic Search

Some barbiturates have been determined in cationic micellar systems by acid-base titrimetry, using both visual and potentiometric end-point detection. The method is shown to be a convenient alternative for the direct accurate and precise assay of microgram amounts of barbiturates.

Rudolf Staro?cik; Ewa Maskiewicz; Feliks Malecki

1987-01-01

132

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

PubMed

Al(3+) selective sensor has been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier morin as ionophore. Best performance was exhibited by the membrane having composition as morin:PVC:sodium tetraphenyl borate:tri-n-butylphosphate in the ratio 5:150:5:150 (w/w, mg). This membrane worked well over a wide activity range of 5.0x10(-7) to 1.0x10(-1)M of Al(3+) with a Nernstian slope of 19.7+/-0.1mV/decade of Al(3+) activity and a limit of detection 3.2x10(-7)M. The response time of the sensor is approximately 5s and membrane could be used over a period of 2 months with good reproducibility. The proposed sensor works well over a pH range (3.5-5.0) and demonstrates good discriminating power over a number of mono-, di- and trivalent cations. The sensor can also be used in partially non-aqueous media having up to 20% (v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working activity range. The sensor has also been used in the potentiometric titration of Al(3+) with EDTA and for its determination in zinc plating mud and red mud. PMID:19071785

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

2007-06-15

133

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

134

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

135

Lead biosorption study with Rhizopus arrhizus using a metal-based titration technique  

Microsoft Academic Search

Acid–base and metal-based potentiometric titration methods were used to analyze sorption mechanisms of lead by Rhizopus arrhizus fungal biomass. Biosorption was not considered globally but as the result of successive sorption reactions on various binding sites with different selectivities. Precipitation occurred rapidly when lead concentration increased. Lead was sorbed essentially by carboxylic groups and by phosphates and sulfonates (less abundant)

Ghinwa Naja; Christian Mustin; Jacques Berthelin; Bohumil Volesky

2005-01-01

136

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

137

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

138

Characterization of petroleum sulfonates by a nonaqueous titration method  

SciTech Connect

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 calculated from the grams of sample titrated and the moles of acid used. The potentiometric titration can be carried out in less than 10 minutes and can be done with 10 to 100 mg of sample. The accuracy and precision of the procedure were examined by the titration of sodium salts of p-toluene sulfonate, 2-naphthalene sulfonate, and petroleum sulfonates. In general, values for the equivalent weight were within 2% of those values determined by the Epton titration, by wet ashing methods, or from the theoretical value. The relative standard deviation (RSD) for the procedure is estimated to be 0.5%. For p-toluene sulfonate, an RSD of 0.15% was calculated. Petroleum sulfonates are used to liberate a residual oil from a porous medium in a tertiary oil-recovery process. 24 refs.

Voss, K.R.; Bricker, C.E.; Michnick, M.J.; Willhite, G.P.

1981-12-01

139

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

PubMed

With an aim to characterize the micellar aggregates of imidazolium based ionic liquids, a new potentiometric PVC sensor based on neutral ion-pair complexes of dodecylmethylimidazolium bromide-sodium dodecylsulfate (C12MeIm(+)DS(-)) has been developed. The electrode exhibited a linear response for the concentration range of 7.9×10(-5)-9.8×10(-3) M with a super-Nernstian slope of 92.94 mV/decade, a response time of 5 s and critical micellar concentration (cmc) of 10.09 mM for C12MeImBr. The performance of the electrode in investigating the cmc of C12MeImBr in the presence of two drugs [promazine hydrochloride (PMZ) and promethazine hydrochloride (PMT)] and three triblock copolymers (P123, L64 and F68) has been found to be satisfactory on comparison with conductivity measurements. Various micellar parameters have been evaluated for the binary mixtures of C12MeImBr with drugs and triblock copolymers using Clint's, Rubingh's, and Motomura's approach. Thus the electrode offers a simple, straightforward and relatively fast technique for the characterization of micellar aggregates of C12MeImBr, complementing existing conventional techniques. Further, the analytical importance of proposed C12MeIm(+)-ISE as end point indicator in potentiometric titrations and for direct determination of cationic surfactants [cetylpyridinium chloride (CPC), tetradecyltrimethylammonium bromide (TTAB), benzalkonium chloride (BC)] in some commercial products was judged by comparing statistically with classical two-phase titration methods. PMID:23375810

Sanan, Reshu; Mahajan, Rakesh Kumar

2013-03-15

140

Using spectrophotometric titrations to characterize humic acid reactivity at environmental concentrations.  

PubMed

Potentiometric titration is a common method to characterize dissolved organic matter (DOM) reactivity. Because of the sensitivity of pH electrodes, it is necessary to work with very high DOM (>1 g/L) concentrations that are unrealistic compared to those found in natural waters (0.1 to 100 mg/L). To obtain proton binding data for concentrations closer to environmental values, spectroscopic titration methodology is a viable alternative to traditional potentiometric titrations. Spectrophotometric titrations and UV-visible spectra of a diluted solution of purified Aldrich humic acid (5 mgDOC/L) are used to estimate changes in proton binding moieties as function of pH and ionic strength after calculation of differential absorbance spectra variations. After electrostatic correction of spectrophotometric data, there is a linear operational correlation between spectrophotometric and potentiometric data which can be used as a transfer function between the two properties. Spectrophotometric titrations are then used to determine the changes of humic acid protonation after adsorption onto alpha-alumina. PMID:20698549

Janot, Noémie; Reiller, Pascal E; Korshin, Gregory V; Benedetti, Marc F

2010-09-01

141

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

142

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

PubMed

A screen-printed electrode (SPE) was fabricated for the determination of 1-(ethoxycarbonyl)pentadecyltrimethylammonium bromide (Septonex) based on the use of Septonex-tetraphenylborate as the electroactive substance, and o-nitrophenyloctylether (o-NPOE) as the plasticizing agent. The electrode passes a near-Nernstian cationic slope of 59.33 ± 0.85 mV from activity between pH values of 2 to 9 with a lower detection limit of 9×10(-7) M and response time of about 5 s and exhibits an adequate shelf-life of 6 months. The method was applied for the determination of Septonex in pharmaceutical preparations. A percentage recovery of 99.88% was obtained with RSD=1.24%. The electrode was successfully applied in the determination of Septonex in laboratory-prepared samples by direct potentiometric, calibration curve and standard addition methods. Potentiometric titration of Septonex with sodium tetraphenylborate and phosphotungstic acid as a titrant was monitored with the modified screen-printed electrode as an end-point indicator electrode. Selectivity coefficients for Septonex relative to a number of potential interfering substances were determined. The sensor was highly selective for Septonex over a large number of compounds. Selectivity coefficient data for some common ions show negligible interference; however, cetyltrimethylammonium bromide and iodide ions interfere significantly. The analytical usefulness of the proposed electrode was evaluated by its application in the determination of Septonex in laboratory-prepared pharmaceutical samples with satisfactory results. The results obtained with the fabricated sensor are comparable with those obtained by the British Pharmacopeia method. PMID:21286616

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

2011-04-01

143

Micromechanical potentiometric sensors  

DOEpatents

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

Thundat, Thomas G. (Knoxville, TN)

2000-01-01

144

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

PubMed

A simple, general and label-free potentiometric method to measure nuclease activities and oxidative DNA damage in a homogeneous solution using a polycation-sensitive membrane electrode is reported. Protamine, a linear polyionic species, is used as an indicator to report the cleavage of DNA by nucleases such as restriction and nonspecific nucleases, and the damage of DNA induced by hydroxyl radicals. Measurements can be done with a titration mode or a direct detection mode. For the potentiometric titration mode, the enzymatic cleavage dramatically affects the electrostatical interaction between DNA and protamine and thus shifts the response curve for the potentiometric titration of the DNA with protamine. Under the optimized conditions, the enzyme activities can be sensed potentiometrically with detection limits of 2.7×10(-4)U/µL for S1 nuclease, and of 3.9×10(-4)U/µL for DNase I. For the direct detection mode, a biocomplex between protamine and DNA is used as a substrate. The nuclease of interest cleaves the DNA from the protamine/DNA complex into smaller fragments, so that free protamine is generated and can be detected potentiometrically via the polycation-sensitive membrane electrode. Using a direct measurement, the nuclease activities could be rapidly detected with detection limits of 3.2×10(-4)U/µL for S1 nuclease, and of 4.5×10(-4)U/µL for DNase I. Moreover, the proposed potentiometric assays demonstrate the potential applications in the detection of hydroxyl radicals. It is anticipated that the present potentiometric strategy will provide a promising platform for high-throughput screening of nucleases, reactive oxygen species and the drugs with potential inhibition abilities. PMID:23665129

Ding, Jiawang; Qin, Wei

2013-09-15

145

Effects of metal cations and fulvic acid on the adsorption of ciprofloxacin onto goethite.  

PubMed

Ciprofloxacin (CIP) can be strongly adsorbed by ferric oxides, but some influencing factors, such as multivalent cations and soil organic matter, have not been evaluated extensively. In this study, the interaction between CIP and four divalent metals (Ca, Cd, Cu, and Pb) was investigated using potentiometric titration and the results indicated that CIP can bind to the divalent metals in the following affinity order: Cu(II)?>?Pb(II)?>?Cd(II)?>?Ca(II). The effects of metals and fulvic acid (FA) on the adsorption behavior of CIP onto goethite surfaces were also examined using batch experiments. It was found that metal cations enhanced the CIP retention on goethite surfaces in the same order as the affinity order with CIP, indicating that metals likely increased CIP retention through cation bridging. FA was found to promote CIP sorption rather than compete with it, and the coexistence of FA and Cu(II) in the system exhibited an addictive effect with CIP sorption, indicating that they might influence the sorption separately under the studied loading condition. Taken together, our results suggested that the coexistence of divalent cations or soil organic matter will enhance CIP sorption on goethite surfaces, hence reducing its mobility and bioavailability in the environment. PMID:25096489

Tan, Yinyue; Guo, Yong; Gu, Xueyuan; Gu, Cheng

2015-01-01

146

Potentiometric and dynamic light scattering investigation of the precipitation of lanthanum fluoride  

Microsoft Academic Search

Precipitation processes were characterised in an aqueous solution of La(NO3)3-KF at 25 °C using a light scattering method and potentiometric pH and pF titrations with a fluoride ion selective electrode.\\u000a Two processes are taking place according to the precipitation diagram: (I) a neutralisation process at high concentrations\\u000a of precipitation components in the ratio 1:3 and with the attained pH at

N. Stubi?ar

147

A new Zn(II)-selective potentiometric sensor based on 4-tert-butylcalix[4]arene in PVC matrix.  

PubMed

Poly(vinyl chloride) (PVC) based membranes containing 4-tert-butylcalix[4]arene (I) as an electroactive material along with anion excluder sodiumtetraphenylborate (NaTPB) and plasticizer tri-butylphosphate (TBP) have been developed to fabricate a new zinc-selective sensor. Out of various compositions, the best performance was exhibited by the membrane having I, NaTPB, TBP and PVC in the ratio 8:5:100:200 (w/w). The sensor works well in the concentration range 9.8 x 10(-6) to 1.0 x 10(-1) mol dm(-3) with a near-Nernstian slope of 28.0+/-1.0 mV/decade of activity. The detection limit is down to 5.0 x 10(-7) mol dm(-3). The working pH range of this sensor is 2.5-4.3 and it works well in partially non-aqueous medium up to 15% (v/v) (methanol, ethanol and acetone). It exhibits a fast response time of 30s and could be used for more than four months without any considerable change in response characteristics. It has excellent selectivity for Zn(II) over other mono-, bi- and trivalent cations which have been reported to cause interference in the working of other sensors. It has been successfully used as an indicator electrode in the potentiometric titration of Zn(II) against EDTA and also to estimate zinc ions in industrial waste waters. PMID:18970696

Gupta, V K; Goyal, R N; Al Khayat, M; Kumar, P; Bachheti, N

2006-07-15

148

Preparation of ethambutol-copper(II) complex and fabrication of PVC based membrane potentiometric sensor for copper.  

PubMed

Copper(II) complex of ethambutol (I) was prepared and used in the fabrication of Cu(2+) selective ISE membrane. The membrane having Cu(II)-ethambutol complex (I) as electroactive material, along with sodium tetraphenylborate (NaTPB) as anion discriminator, dioctylphthalate (DOP) as plasticizer in poly(vinyl chloride) (PVC) matrix in the percentage ratio 6:2:190:200 (I:NaTPB:DOP:PVC) (w/w) gave a linear response in the concentration range 7.94x10(-6) to 1.0x10(-1) M of Cu(2+) with a slope of 29.9+/-0.2 mV per decade of activity and a fast response time of 11+/-2 s. The sensor works well in the pH range 2.1-6.3 and could be satisfactorily used in presence of 40% (v/v) methanol, ethanol and acetone and is selective for copper over a large number of cations with slight interference from Na(+) and Co(2+) if present at a level 1.5x10(-5) and 6.5x10(-5) M, respectively. It works well over a period of 6 months and can also be used as indicator electrode for the end point determination in the potentiometric titration of Cu(2+) against EDTA as well as in the determination of Cu(2+) in real samples. PMID:18969035

Gupta, Vinod K; Prasad, Rajendra; Kumar, Azad

2003-05-28

149

Filtrates & Residues: Olfactory Titration.  

ERIC Educational Resources Information Center

Presents an experiment that uses a unique acid-base indicator--the odor of raw onion--to indicate the end point of the titration of sodium hydroxide with hydrochloric acid. Allows the student to detect the completion of the neutralization reaction by olfaction rather than sight. (JRH)

Wood, John T.; Eddy, Roberta M.

1996-01-01

150

Theoretical problems associated with the use of acetic anhydride as a co-solvent for the non-aqueous titration of hydrohalides of organic bases and quaternary ammonium salts.  

PubMed

A potentiometric titration study of organic base hydrohalides and quaternary ammonium salts using perchloric acid as the titrant and a mixture of acetic anhydride and acetic acid as the solvent was carried out and the titration mixture was analysed by NMR in order to clarify the chemistry of the reactions involved. It was found that in contrast to the general belief the formation of acetyl halides and titratable free acetate ion does not take place prior to the titration but NMR spectra proved the formation of acetyl halides in the course of the titration. This observation and the fact that the shape of the titration curves depends on the nature of the hydrohaloic acid bound to the base or of the anion in the quaternary ammonium salts led to the conclusion that the titrating agent is acetyl perchlorate formed in situ during the titration. Equations of the reactions involved in the titration process are shown in the paper. PMID:19682817

Völgyi, Gergely; Béni, Szabolcs; Takács-Novák, Krisztina; Görög, Sándor

2010-01-01

151

Titration Curves: Fact and Fiction.  

ERIC Educational Resources Information Center

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

Chamberlain, John

1997-01-01

152

Studies on the acidity of mordenite and ZSM-5. 1. Determination of Broensted acid site concentrations in mordenite and ZSM-5 by conductometric titration  

SciTech Connect

The Broensted acidity of H-mordenite and H-ZSM-5 samples of varying proton concentration has been studied using aqueous conductometric titration, IR spectroscopy, and aqueous potentiometric titration. Good agreement is observed between Broensted acid site concentrations determined by conductometric titration and IR measurements, while indirect potentiometric titration affords acid site concentrations consistently lower than those measured using the conductometric technique. This finding is rationalized on the basis that, in a conductometric titration, all the accessible Broensted acid sites are direct;y titrated, whereas in the potentiometric procedure utilized, only those protons which can be ion-exchanged out of the zeolite are titrated. After allowing for the presence of extraframework aluminum in the zeolites (determined by [sup 27]Al NMR), the measured acidity for H-mordenite is found to increase linearly with increasing Al content within the range 0-1.5 mmol Al/g but appears to reach a limiting value at higher Al concentrations. For H-ZSM-5, the experimentally determined number of Broensted acid sites is also found to be linearly dependent on the Al molar fraction within the range measured (0-1.20 mmol Al/g). For both series of zeolite samples, the measured acidity is generally found to be less than the theoretical maximum calculated on the basis of an H[sup +]/Al ratio of 1. 43 refs., 10 figs., 4 tabs.

Crocker, M.; Herold, R.H.M.; Sonnemans, M.H.W.; Emeis, C.A.; Wilson, A.E.; Moolen, J.N. van der (Koninklijke/Shell-Laboratorium, Amsterdam (Netherlands))

1993-01-14

153

[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

154

Acid-base titration curves for acids with very small ratios of successive dissociation constants.  

PubMed

The shapes of the potentiometric acid-base titration curves obtained in the neutralizations of polyfunctional acids or bases for which each successive dissociation constant is smaller than the following one are examined. In the region 0 < < 1 (where is the fraction of the equivalent volume of reagent that has been added) the slope of the titration curve decreases as the number j of acidic or basic sites increases. The difference between the pH-values at = 0.75 and = 0.25 has (1 j)log 9 as the lower limit of its maximum value. PMID:18961431

Campbell, B H; Meites, L

1974-02-01

155

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

156

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

PubMed

This paper describes the development of screen-printed (SPE) and carbon paste (CPE) sensors for the rapid and sensitive quantification of naphazoline hydrochloride (NPZ) in pharmaceutical formulations. This work compares the electroactivity of conventional carbon paste and screen-printed carbon paste electrodes towards potentiometric titration of NPZ. The repeatability and accuracy of measurements performed in the analysis of these pharmaceutical matrices using new screen printed sensors were evaluated. The influence of the electrode composition, conditioning time of the electrode and pH of the test solution, on the electrode performance were investigated. The drug electrode showed Nernstain responses in the concentration range from 1 × 10(-6) to 1 × 10(-2) mol L(-1) with slopes of 57.5 ± 1.3 and 55.9 ± 1.6 mV per decade for SPE and CPE, respectively, and was found to be very precise and usable within the pH range 3-8. These sensors exhibited a fast response time (about 3 s for both SPE and CPE, respectively), a low detection limit (3.5 × 10(-6) and 1.5 × 10(-6) M for SPE and CPE, respectively), a long lifetime (3 and 2 months for SPE and CPE, respectively) and good stability. The selectivity of the electrode toward a large number of inorganic cations, sugars and amino acids was tested. It was applied to potentiometric determination of NPZ in pure state and pharmaceutical preparation under batch conditions. The percentage recovery values for the assay of NPZ in tablets (relative standard deviations ?0.3% for n = 4) were compared well with those obtained by the official method. PMID:20959926

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

2011-01-21

157

Potentiometric studies on the formation equilibria of binary and ternary complexes of cobalt(II) with adenosine-5?-mono-, -di-, and -triphosphate and some biologically important polybasic oxygen acids  

Microsoft Academic Search

Potentiometric equilibrium measurements have been made for the interaction of adenosine-5'-mono-,-di-, and -triphosphate, and Co(II) with biologically important secondary ligands (malic, maleic, succinic, tartaric, citric, and oxalic acid). The formation of various 1:1:1 mixed ligand complexes inferred from the potentiometric titration curves. Initial estimates of the formation constants of the resulting species and the acid dissociation constants ofAMP,ADP,ATP and the

H. A. Azab; A. M. El-Nady; A. Hassan; R. S. A. Azkal

1994-01-01

158

Application of a new multivariate curve resolution procedure to the simultaneous analysis of several spectroscopic titrations of the copper(II)—polyinosinic acid system  

Microsoft Academic Search

The acid-base properties and the copper(II)-complexing behaviour of the polynucleotide polyinosinic acid have been studied by means of potentiometric and spectrophotometric titrations. Spectrophotometric data have been treated with a new multivariate curve resolution procedure that allows to analyze simultaneously different sets of spectroscopic titrations of the same multi-equilibria system. The results obtained give a real proof of the advantages of

R. Tauler; A. Izquierdo-Ridorsa; R. Gargallo; E. Casassas

1995-01-01

159

Potentiometric determination of the 'formal' hydrolysis ratio of aluminium species in aqueous solutions.  

PubMed

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 to calculate the initial formal hydrolysis ratio of hydrolysed aluminium-ion solutions. Several solutions of pure hydrolytic species including aluminium monomers (AlCl3), Al13 polynuclear cluster ([Al13O4(OH)24(H2O)12]7+), Al30 polynuclear cluster ([Al30O8(OH)56(H2O)26]18+) and a suspension of nanoparticulate aluminium hydroxide have been used as 'reference standards' to validate the proposed potentiometric method. Other important variables in the potentiometric determination of the hydrolysis ratio have also been optimised including the concentration of aluminium and the type and strength of alkali (Trizma-base, NH3, NaHCO3, Na2CO3 and KOH). The results of the potentiometric analysis have been cross-verified by quantitative 27Al solution nuclear magnetic resonance (27Al NMR) measurements. The 'formal' hydrolysis ratio of a commercial basic aluminium chloride has been measured as an example of a practical application of the developed technique. PMID:18155411

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

2008-01-21

160

Design and construction of new potentiometric sensors for determination of Al(3+) ion based on (Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine.  

PubMed

(Z)-2-(2-methyl benzylidene)-1-(2,4-dinitrophenyl) hydrazine (L) was used as an active component of PVC membrane electrode (PME), coated graphite electrode (CGE) and coated silver wire electrode (CWE) for sensing Al(3+) ion. The electrodes exhibited linear Nernstian responses to Al(3+) ion in the concentration range of 1.0×10(-6) to 1.0×10(-1)M (for PME, LOD=8.8×10(-7)M), 5.5×10(-7) to 2.0×10(-1)M (for CWE, LOD=3.3×10(-7)M) and 1.5×10(-7) to 1.0×10(-1)M (for CGE, LOD=9.2×10(-8)M). The best performances were observed with the membranes having the composition of L:PVC:NPOE:NaTPB in the ratio of 5:35:57:3 (w/w; mg). The electrodes have a response time of 6s and an applicable pH range of 3.5-9.1. The sensors have a lifetime of about 15weeks and exhibited excellent selectivity over a number of mono-, bi-, and tri-valent cations including alkali, alkaline earth metal, heavy and transition metal ions. Analytical utility of the proposed sensor has been further tested by using it as an indicator electrode in the potentiometric titration of Al(3+) with EDTA. The electrode was also successfully applied for the determination of Al(3+) ion in real and pharmaceutical samples. PMID:25687018

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

2015-04-01

161

APAP and Alternative Titration Methods.  

PubMed

PURPOSE OF REVIEW: Positive airway pressure therapy (PAP) is commonly prescribed treatment for obstructive sleep apnea (OSA). Traditionally, the determination of the optimal pressure for treatment of sleep-disordered breathing was made by manual titration of the device by a sleep technician in attendance during polysomnography. However, the advent of alternative methods for determination of optimal PAP - such as auto-titrating PAP (APAP) - has seen tremendous growth over the past decade. The purpose of this review is to improve our understanding of the currently available alternative methods for titration of PAP in patients with sleep-disordered breathing (SDB) with special emphasis on obstructive sleep apnea. RECENT FINDINGS: Recent prospective-randomized studies of alternative methods of titration suggest that pressure determinations made by such devices are comparable to traditional manual titrations made in the sleep laboratory. Obstacles to the adoption of such alternative modes of titration into day-to-day practice may be attributable to issues surrounding appropriate patient selection, differences between devices, re-imbursement policies of third party payors, consensus amongst sleep experts, and individual physicians' practice patterns and volumes. While newer generations and types of auto-titrating PAP devices are entering the sleep field constantly, providers' knowledge and time availability remain limiting factors. SUMMARY: There is tremendous growth in the technology and scientific evidence in support of alternative modes of PAP titration for sleep-disordered breathing, but barriers to implementation remain. PMID:20806054

Ahmed, Omer; Parthasarathy, Sairam

2010-09-01

162

APAP and Alternative Titration Methods  

PubMed Central

Purpose of review Positive airway pressure therapy (PAP) is commonly prescribed treatment for obstructive sleep apnea (OSA). Traditionally, the determination of the optimal pressure for treatment of sleep-disordered breathing was made by manual titration of the device by a sleep technician in attendance during polysomnography. However, the advent of alternative methods for determination of optimal PAP – such as auto-titrating PAP (APAP) – has seen tremendous growth over the past decade. The purpose of this review is to improve our understanding of the currently available alternative methods for titration of PAP in patients with sleep-disordered breathing (SDB) with special emphasis on obstructive sleep apnea. Recent Findings Recent prospective-randomized studies of alternative methods of titration suggest that pressure determinations made by such devices are comparable to traditional manual titrations made in the sleep laboratory. Obstacles to the adoption of such alternative modes of titration into day-to-day practice may be attributable to issues surrounding appropriate patient selection, differences between devices, re-imbursement policies of third party payors, consensus amongst sleep experts, and individual physicians’ practice patterns and volumes. While newer generations and types of auto-titrating PAP devices are entering the sleep field constantly, providers’ knowledge and time availability remain limiting factors. Summary There is tremendous growth in the technology and scientific evidence in support of alternative modes of PAP titration for sleep-disordered breathing, but barriers to implementation remain. PMID:20806054

Ahmed, Omer; Parthasarathy, Sairam

2010-01-01

163

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

164

Investigations of new potentiometric gas sensing systems  

SciTech Connect

Research concerning the development of new and/or improved potentiometric gas sensing systems is described. Studies relating to the development of reversible potentiometric oxygen sensors based on polymeric and metallic film electrodes are presented. In addition, the design and analytical utility of a novel differential ion-selective membrane electrode-based potentiometric gas sensing cell with enhanced sensitivity is documented. The performance of a reversible potentiometric oxygen gas sensor based on a polymeric membrane doped with cobalt-complexes is described. For such sensors, the potentiometric oxygen response is attributed to a mixed potential originating from the underlying platinum electrode surface as well as the Co(II)-tetren doped film. This leads to a short term oxygen response of nearly the theoretical slope value of 118 mV/decade, below 10% O[sub 2]. In the presence of the Co(II)-tetren/PVC film, an analytically useful response is observed for approx. 6-8 days. Thin films of metallic copper, electrochemically deposited on platinum and sputtered on a single crystal silicon wafer, are also examined for reversible potentiometric oxygen sensing. The long-term reversibility and potentiometric stability of such copper film-based sensors is enhanced (up to one month) by preventing the formation of cuprous oxide on the surfaces via the application of an external non-polarizing cathodic current through the working electrode, or by specifically using sputtered copper films that have [100] crystal structures as determined by X-ray diffraction. Finally, the development and application of a differential ion-selective membrane electrode-based potentiometric gas sensing cell is described. The prospects of fabricating differential detection arrangements for CO[sub 2], NO[sub 2], and SO[sub 2], NH[sub 3] are also discussed.

Yim, Hyoung-Sik

1992-01-01

165

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

Microsoft Academic Search

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

Bart Baeyens; Michael H. Bradbury

1997-01-01

166

Amperometric, Bipotentiometric, and Coulometric Titration.  

ERIC Educational Resources Information Center

Discusses recent review articles in various kinds of titration. Also discusses new research in apparatus and methodology, acid-base reactions, precipitation and complexing reactions, oxidation-reduction reactions, and nomenclature. Cites 338 references. (CS)

Stock, John T.

1980-01-01

167

Potentiometric membrane sensor based on 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene for detection of Sn(II) in real samples.  

PubMed

A Sn2+ ion-selective electrode which was prepared with a polymeric membrane based on 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene (NDDBH) as a ionophore. Effects of experimental parameters such as membrane composition, nature and amount of plasticizer, the amount of additive and concentration of internal solution on the potential response of Sn2+ sensor were investigated. The electrode exhibited a Nernstian slope of 28.8+/-1.1 mV/decade of Sn2+ over a concentration range of 1.0 x 10(-5) to 1.0 x 10(-1) M of Sn2+ in an acidic solution (pH 1). The limit of detection was 4.0 x 10(-6) M. The results show that this electrode can be used in ethanol media until 20% (v/v) concentration without interference. It can be used for more than 6 weeks without any considerable divergence in the potentials. The proposed membrane electrode revealed very good selectivity for Sn(II) ions over a wide variety of other cations and could be used in acidic media. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal coefficient of the electrode. The stability constant (log K(s)) of the Sn(II)-ionophore complex was determined at 25 degrees C by potentiometric titration in mixed aqueous solution. It was used as indicator electrode in potentiometric determination of Sn(II) ion in real samples. PMID:17723734

Arvand, Majid; Moghimi, A Majid; Afshari, Anoosheh; Mahmoodi, Nosratollah

2006-10-01

168

The potentiometric determination of stability constants for zinc acetate complexes in aqueous solutions to 295C  

SciTech Connect

A potentiometric method was used to determine the formation quotients of zinc acetate complexes in aqueous solutions from 50 to 295C at ionic strengths of 0.03, 0.3, and 1.0 m. The potentiometric titrations were carried out in an externally heated, Teflon-lined concentration cell fitted with hydrogen electrodes. Formal sodium acetate concentrations of the experimental solutions ranged from 0.001 to 0.1 m with acetic acid to sodium acetate ratios ranging from 30 to 300. Sodium trifluoromethanesulfonate (F{sub 3}CSO{sub 3}Na) was used as a supporting electrolyte. Stoichiometries and formation quotients for the complexes ZnCH{sub 3}COO{sup +}, Zn(CH{sub 3}COO){sub 2}, and Zn(CH{sub 3}COO){sub 3}{sup {minus}} were derived from the titration data by regression analysis. Stability constants at infinite dilution (K{sub n}) and other relevant thermodynamic quantities were calculated for these three complexes. Calculations of zinc speciation in acetate-chloride solutions show that zinc acetate complexes should have an importance similar to zinc chloride complexes in high acetate waters where chloride to acetate molal ratios are less than about 10.

Giordano, T.H. (New Mexico State Univ., Las Cruces (United States)); Drummond, S.E. (Oak Ridge National Lab., TN (United States))

1991-09-01

169

ANTIBODY TITRATION PROTOCOL NOTE: When titrating an antibody for use in flow cytometry, you should  

E-print Network

ANTIBODY TITRATION PROTOCOL NOTE: When titrating an antibody for use in flow cytometry, you should attempt to titrate it under the same conditions in which it will be used during your experimental cell're titrating. You should titrate each new vial of antibody you receive in your lab, even if you've used

Oliver, Douglas L.

170

[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

171

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

172

Mass spectrometric-potentiometric titration analyses of nitrogen concentrates from shale oils  

SciTech Connect

Nitrogen-rich fractions from retorted and hydroprocessed shale oils have been analyzed by high resolution mass spectrometry. The results from this analysis are compared to the results from titrimetric measurements on the same samples. The comparison shows good agreement except in fractions where the pyrrole and arylamine compound types are concentrated. The use of adequate chromatographic procedures and high resolution mass spectrometry enables the semi-quantitative determination of nitrogen compound types in retorted shale oils and intermediate refined products. From a comparison of the nitrogen compound type distributions in retorted and hydroprocessed shale oils, the effect of catalytic hydrotreatment on nitrogen compound types can be studied. Evidence for the formation of reaction intermediates during hydroprocessing was obtained. The intermediates are similar to those identified in model compound studies.

Heppner, R.A.; Holmes, S.A.

1983-01-01

173

31P NMR, potentiometric and spectrophotometric studies of phytic acid ionization and complexation properties toward Co 2+, Ni 2+, Cu 2+, Zn 2+ and Cd 2+  

Microsoft Academic Search

Acido-basic properties of phytic acid as well as its binding properties toward five bivalent metal ions (Co2+, Ni2+, Cu2+, Zn2+ and Cd2+) were investigated. Potentiometric titration curves refined with the program PROTAF allowed the determination of acidity constants of the ligand as well as complexation constants with the considered metal ions for systems containing ligand-to-metal ratios over unity. The chelating

A. Bebot-Brigaud; C. Dange; N. Fauconnier; C. Gérard

1999-01-01

174

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

175

High-sensitivity titration microcalorimeter  

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

176

Polyelectrolyte Titration: Theory and Experiment  

E-print Network

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

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

2000-05-18

177

Potentiometric sensors for trace-level analysis  

PubMed Central

This review summarizes recent progress in the development and application of potentiometric sensors with limits of detection (LODs) in the range 10?8–10?11 M. These LODs relate to total sample concentrations and are defined according to a definition unique to potentiometric sensors. LODs calculated according to traditional protocols (three times the standard deviation of the noise) yield values that are two orders of magnitude lower. We are targeting this article at analytical chemists who are non-specialists in the development of such sensors so that this technology may be adopted by a growing number of research groups to solve real-world analytical problems. We discuss the unique response features of potentiometric sensors and compare them to other analytical techniques, emphasizing that the choice of the method must depend on the problem of interest. We discuss recent directions in sensor design and development and present a list of 23 sensors with low LODs, with references. We give recent examples where potentiometric sensors have been used to solve trace-level analytical problems, including the speciation of lead and copper ions in drinking water, the measurement of free copper in sea water, and the uptake of cadmium ions by plant roots as a function of their speciation. PMID:16642205

Bakker, Eric; Pretsch, Ernö

2005-01-01

178

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

179

ChemTeacher Resource: Acid Base Titration  

NSDL National Science Digital Library

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

University of Southern California

2011-01-01

180

Actinide cation-cation complexes  

SciTech Connect

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

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

1994-12-01

181

Titration of an Unknown Acid or Base  

NSDL National Science Digital Library

This website contains a JAVA applet that simulates the titration of an unknown acid or base, and provides a graphical output of the titration curve. The unknown compounds are taken from a list of amino acids. Students set up the parameters of the titration, and then create a simulated pH curve. From this they are able to identify the unknown compound from the list, and determine the acid dissociation constant(s) from the titration data.

Blauch, David N.

182

Alternative methods for titratable acidity determination  

Microsoft Academic Search

Methods for determination of titratable acidity, other than traditional titration, i.e. methods without titration, are considered. A number of them use analytical acid-base reagents which quickly convert a mixture of strong and weak acids into a new system. This conversion makes it possible to obtain directly the analytical signal (pH, optical density, etc.) for titratable acidity calculation. These methods in

O. Yu. Berezin; Ya. I. Tur'yan; I. Kuselman; A. Shenhar

1995-01-01

183

Colorblindness and Titrations with Visual Indicators.  

ERIC Educational Resources Information Center

Discusses various issues related to colorblind students performing titrations with visual indicators. Includes tables showing precisions in the titration of a weak acid by colorblind students using phenolphthalein and thymolphthalein and in the titration of a weak base by colorblind persons using methyl red and bromcresol green. (JN)

Diehl, Harvey; And Others

1985-01-01

184

Fluorapatite surface composition in aqueous solution deduced from potentiometric, electrokinetic, and solubility measurements, and spectroscopic observations  

NASA Astrophysics Data System (ADS)

The surface chemistry of fluorapatite in aqueous solution was investigated using electrokinetic techniques, potentiometric titrations, solubility measurements, and attenuated total reflection infrared spectroscopy. All methods indicate the formation of Ca/F depleted, P enriched altered layer via exchange reactions between H + and Ca 2+, and OH - and F - at the fluorapatite (FAP) surface. Observations suggest that this leached layer has a di-calcium phosphate (CaHPO 4) composition and that it controls the apparent solubility of FAP. Electrokinetic measurements yield an iso-electric point value of 1 ± 0.5 consistent with a negatively charged FAP surface at pH > 1. In contrast, surface titrations give an apparent pH of point of zero charge of ˜7.7, consistent with a positively charged surface at pH < 7.7. These differences are shown to stem from proton consumption by both proton exchange and dissolution reactions at the FAP surface. After taking account for these effects, FAP surface charge is shown to be negative to at least pH 4 by surface titration analysis.

Chaïrat, Claire; Oelkers, Eric H.; Schott, Jacques; Lartigue, Jean-Eric

2007-12-01

185

Titration (ChemPages Lab)  

NSDL National Science Digital Library

Titration: this is a resource in the collection "ChemPages Laboratory Resources". A titration is a laboratory procedure for quantitative analysis. Titrametric analysis is used to determine the concentration of an analyte in solution, the stoichiometry of a reaction, the number of electrons gained or accepted in a redox reaction and the solubility products. The ChemPages Laboratory Resources are a set of web pages that include text, images, video, and self check questions. The topics included are those that are commonly encountered in the first-year chemistry laboratory. They have been put together for use as both a pre-laboratory preparation tool and an in-laboratory reference source.

186

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

187

Precise coulometric titration of precious metals III. Determination of gold (III) with electrogenerated chlorocuprous ion in KCl-Cu-EDTA buffer medium.  

PubMed

A method for the precise coulometric titration of gold (III) with electrogenerated chlorocuprous ion in KCl-Cu-EDTA buffer medium is described. 7.45-16.8 mg of gold can be determined with potentiometric end-point detection (RSD = 0.04%). The method is applied to precise analysis of gold in pure gold, jewellery and gold alloys with good selectivity. The mechanism of electron exchange at the gold-plated platinum cathode-electrolyte interface during the process of titration and the reversibility of the electrode in the proposed electrolyte are discussed. PMID:18966587

Dong, S; Yang, X

1996-07-01

188

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

189

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

PubMed

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

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

2011-01-01

190

High-temperature carbon monoxide potentiometric sensor  

Microsoft Academic Search

These sensors have been used in industrial alarm and control systems for monitoring and control of the oxygen concentration in a gas stream and for the control of air-fuel ratio in internal combustion engines as in automobiles. A high-temperature potentiometric CO sensor was developed by coating a mixture of CuO\\/ZnO over one of the platinum electrodes of a cell with

N. Li; T. C. Tan; H. C. Zeng

1993-01-01

191

Aluminum(III) speciation with acetate and oxalate. A potentiometric and sup 27 Al NMR study  

SciTech Connect

Aluminum (III) hydrolysis and precipitation in the presence of acetic acid and oxalic acid have been studied by combining potentiometric titration and liquid-state {sup 27}Al NMR. The main aluminum species have thus been identified and quantified: unreacted hydrolyzed, complexed monomers, and the Al{sub 13} tridecamer. A solid species appeared when precipitation occurred and was quantified by difference with the other species. The quantitative evolution of these species was followed for pH values up to 5. Acetate forms weak complexes with aluminum. The precipitated phase was hypothesized to be aggregated Al{sub 13}. Oxalate forms strong multiligand complexes to form Al{sub 13} requires higher hydroxyl content. High oxalate contents (L/M > 1) inhibit tridecamer formation and precipitation occurs only at high pH values. With oxalate the precipitated phase seems to be devoid of Al{sub 13} and of a more condensed nature than it is with acetate.

Thomas, F.; Rouiller, J.; Genevrier, F.; Boudot, D. (Univ. Nancy, Vandoeuvre (France)); Masion, A.; Bottero, J.Y. (Centre de Recherches sur la Valorisation des Minerais, Vandoeuvre (France))

1991-09-01

192

Differential potentiometric determination of perchlorate and iodide ions in industrial wastes  

SciTech Connect

The determination of perchlorates and iodides present together in industrial wastes is hampered by the fact that these anions either are precipitated by the same organic reagents or form colored complexes with similar absorption maxima. Determining them by separation or by deducting one from their sum is a multi-step analysis which takes more time and decreases accuracy. In this paper, the authors report a rapid, single-step determination of co-present perchlorate and iodide by precipitative titration with nitron solution and potentiometric indication of the equivalence point by a perchlorate-selective membrane electrode. The perchlorate and iodide determinations were unaffected by surfactant, suspensions, and ions not precipitated with nitron. A single analysis takes 15-20 minutes. This method may also be used for analyzing single salts.

Kolbyagin, N.P.; Vlasova, E.G.; Zhilina, O.D.; Renkova, Z.S.

1986-12-01

193

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

194

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

PubMed

A potentiometric Pb(II)-selective sensor was fabricated by a combinatorial screening of electrically conducting polysulfoaminoanthraquinone (PSA) nanoparticles as a solid ionophore, ion exchangers (oleic acid (OA) and NaTPB), plasticizers in a polyvinyl chloride (PVC) matrix, membrane thickness, inner filling ion species, and concentration. The membrane sensor with the composition of PSA/PVC/DOP (dioctyl phthalate)/OA (1.0:33:61:5.0) exhibited the best performance, including a slope of 29.3 mV decade(-1) in the concentration range 10(-6.3)-10(-1.6) M, detection limit of 1.6 × 10(-7) M, response time of 16 s, lifetime of five months, and good response reversibility. The proposed sensor has demonstrated good selectivity for Pb(II) over other monovalent, divalent and trivalent interfering ions, and could be used in a pH range of 3.62-5.22. The Pb(II) sensor has been successfully applied for the determination of Pb(II) concentration in real-world samples and also as an indicator electrode for potentiometric titration of lead ions. PMID:24512280

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

2014-03-10

195

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

SciTech Connect

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

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

1982-02-01

196

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

PubMed

New PVC-membrane electrodes were prepared by using 2-((thiazol-2-ylimino)methyl)phenol (L1) and 2-((thiazol-2-ylamino)methyl)phenol (L2) and explored as Co(II) selective electrodes. The effect of various plasticizers and anion excluder was studied in detail and improved performance was observed. It was found that the electrode based on L1 shows better response characteristics in comparison to L2. Optimum performance was observed for the membrane electrode having a composition of L1:NaTPB:DBP:PVC?2:8:78:62 (w/w, mg). The performance of PME based on L1 was compared with that of CGE. The electrodes exhibit Nernstian slope for Co(II) ions with a limit of detection of 6.91×10(-7) mol L(-1) for PME and 7.94×10(-8) mol L(-1) for CGE. The response time for PME and CGE was found to be 15s and 12 s respectively. The potentiometric responses are independent in the pH range 3.0-9.0 for CGE. The CGE could be used for a period of 90 days. The CGE was used as an indicator electrode in potentiometric titration of EDTA with Co(2+) ion. Further the selectivity of the L1 and L2 was also confirmed by the UV-vis and colorimetric studies and found that L1 is more selective for Co(II) ion. PMID:25491823

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

2014-12-01

197

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

198

Beer classification by means of a potentiometric electronic tongue.  

PubMed

In this work, an electronic tongue (ET) system based on an array of potentiometric ion-selective electrodes (ISEs) for the discrimination of different commercial beer types is presented. The array was formed by 21 ISEs combining both cationic and anionic sensors with others with generic response. For this purpose beer samples were analyzed with the ET without any pretreatment rather than the smooth agitation of the samples with a magnetic stirrer in order to reduce the foaming of samples, which could interfere into the measurements. Then, the obtained responses were evaluated using two different pattern recognition methods, principal component analysis (PCA), which allowed identifying some initial patterns, and linear discriminant analysis (LDA) in order to achieve the correct recognition of sample varieties (81.9% accuracy). In the case of LDA, a stepwise inclusion method for variable selection based on Mahalanobis distance criteria was used to select the most discriminating variables. In this respect, the results showed that the use of supervised pattern recognition methods such as LDA is a good alternative for the resolution of complex identification situations. In addition, in order to show an ET quantitative application, beer alcohol content was predicted from the array data employing an artificial neural network model (root mean square error for testing subset was 0.131 abv). PMID:23870992

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

2013-12-01

199

pH and Titratable Acidity  

NASA Astrophysics Data System (ADS)

There are two interrelated concepts in food analysis that deal with acidity: pH and titratable acidity. Each of these quantities is analytically determined in separate ways and each has its own particular impact on food quality. Titratable acidity deals with measurement of the total acid concentration contained within a food (also called total acidity). This quantity is determined by exhaustive titration of intrinsic acids with a standard base. Titratable acidity is a better predictor of acid's impact on flavor than pH.

Sadler, George D.; Murphy, Patricia A.

200

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

201

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

PubMed

In this approach, a new chemically modified carbon paste electrode was assembled for potentiometric assay of mercury(II) ion in the aqueous environments. Hereby, MWCNTs were used in the carbon paste composition to meliorate the electrical conductivity and sensitivity of the carbon paste owing to its exceptional physicochemical characteristics. Likewise, participation of the BEPT as a super-selective ionophore in the carbon paste composition boosted significantly the selectivity of the modified electrode towards Hg(II) ions over a wide concentration range of 4.0 × 10(-9)-2.2 × 10(-3) mol L(-1) with a lower detection limit of 3.1 × 10(-9) mol L(-1). Besides, Nernstian slope of the proposed sensor was 28.9(± 0.4)mV/decade over a pH range of 3.0-5.2 with potentiometric short response time of 10s. In the interim, by storing in the dark and cool dry place during non-usage period, the electrode can be used for at least 30 days without any momentous divergence of the potentiometric response. Eventually, to judge about its practical efficiency, the arranged sensor was utilized successfully as an indicator electrode for potentiometric titration of mercury(II) with standard solution of EDTA. As well, the quantitative analysis of mercury(II) ions in some aqueous samples with sensible accuracy and precision was satisfactorily performed. PMID:25492198

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

2015-02-01

202

Isothermal Titration Calorimetry of RNA  

PubMed Central

Isothermal titration calorimetry (ITC) is a fast and robust method to study the physical basis of molecular interactions. A single well-designed experiment can provide complete thermodynamic characterization of a binding reaction, including Ka, ?G, ?H, ?S and reaction stoichiometry (n). Repeating the experiment at different temperatures allows determination of the heat capacity change (?CP) of the interaction. Modern calorimeters are sensitive enough to probe even weak biological interactions making ITC a very popular method among biochemists. Although ITC has been applied to protein studies for many years, it is becoming widely applicable in RNA biochemistry as well, especially in studies which involve RNA folding and RNA-interactions with small molecules, proteins and with other RNAs. This review focuses on best practices for planning, designing, and executing effective ITC experiments when one or more of the reactants is an RNA. PMID:18835447

Salim, Nilshad N.; Feig, Andrew L.

2009-01-01

203

Dissolved oxygen: method comparison with potentiometric stripping analysis  

SciTech Connect

Three methods for determination of dissolved oxygen in samples of natural water are compared; potentiometric stripping analysis, PSA compares well with oxygen selective electrodes. Although potentiometric stripping analysis and oxygen selective electrode methods are found to be simple, rapid and of higher reproducibility than the usual Winkler procedure, the use of oxygen selective electrodes has many disadvantages.

Fayyad, M.; Tutunji, M.; Ramakrishna, R.S.; Taha, Z.

1987-04-01

204

A Tabular Approach to Titration Calculations  

ERIC Educational Resources Information Center

Titrations are common laboratory exercises in high school and university chemistry courses, because they are easy, relatively inexpensive, and they illustrate a number of fundamental chemical principles. While students have little difficulty with calculations involving a single titration step, there is a significant leap in conceptual difficulty…

Lim, Kieran F.

2012-01-01

205

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

USGS Publications Warehouse

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

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

1996-01-01

206

Prediction of aluminum, uranium, and co-contaminants precipitation and adsorption during titration of acidic sediments.  

PubMed

Batch and column recirculation titration tests were performed with contaminated acidic sediments. A generic geochemical model was developed combining precipitation, cation exchange, and surface complexation reactions to describe the observed pH and metal ion concentrations in experiments with or without the presence of CO2. Experimental results showed a slow pH increase due to strong buffering by Al hydrolysis and precipitation and CO2 uptake. The cation concentrations generally decreased at higher pH than those observed in previous tests without CO2. Using amorphous Al(OH)3 and basaluminite precipitation reactions and a cation exchange selectivity coefficient K(Na\\Al) of 0.3, the model approximately described the observed (1) pH titration curve, (2) Ca, Mg, and Mn concentration by cation exchange, and (3) U concentrations by surface complexation with Fe hydroxides at pH < 5 and with liebigite (Ca2UO2(CO3)3·10H2O) precipitation at pH > 5. The model indicated that the formation of aqueous carbonate complexes and competition with carbonate for surface sites could inhibit U and Ni adsorption and precipitation. Our results suggested that the uncertainty in basaluminite solubility is an important source of prediction uncertainty and ignoring labile solid phase Al underestimates the base requirement in titration of acidic sediments. PMID:23641798

Tang, Guoping; Luo, Wensui; Watson, David B; Brooks, Scott C; Gu, Baohua

2013-06-01

207

Potentiometric determination of acid dissociation constants (pKa) for human and veterinary antibiotics.  

PubMed

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 (delta2pH/deltaV2) method was primarily applied to determining pKa's from titration curves for most antibiotics due to its convenience and accuracy. For tetracyclines, however, a least-square non-linear regression method was developed to determine their pKa's because the second-derivative method cannot well distinguish the pKa,2 and pKa,3 of tetracyclines. Results indicate that the pKa values are approximately 2 and 5-7.5 for sulfonamides; 7.5-9 for macrolides; 3-4, 7-8 and 9-10 for tetracyclines; 3-4, 6, 7.5-9 and 10-11 for fluoroquinolones; while compound-specific for other miscellaneous antibiotics. The moieties corresponding to specific pKa's were identified based on chemical structures of antibiotics. In addition, the pKa's available in literature determined by various techniques are compiled in comparison with the values of this work. These results are expected to essentially facilitate the research on occurrence, fate and effects, analysis methods development, and control of antibiotics in various treatment operations. PMID:15223282

Qiang, Zhimin; Adams, Craig

2004-07-01

208

Potentiometric analysis using solutions of cerium sulfates  

SciTech Connect

In a previous work the authors outlined the bases of a new method of instrumental determination of the chemical oxygen consumption (COC): The analysis is performed within the framework of the umpire analysis of COC, but the consumption of the oxidizing agent is continuously recorded according to the change in the emf of the galvanic cell (glass pH-metric electrode; cerium (IV,III) sulfates, potassium bichromate, 7.5 M H/sub 2/SO/sub 4/; and glass redoximetric electrode EO-021. The authors contend that potentiometric recording permits not only a simplication of the determination of COC but also the removal of the rigid limitations on the time of boiling of the sample. Additional information may be obtained on the corresponding and difficultly oxidized substances in the sample to be analyzed. It is noted after a discussion of main peculiarities of the cell that the selection of the conditions of analysis is dictated largely by the requirements set in the determinations of COC which permits a number of shortcomings of the potentiometric method to be determined.

Pugin., G.V.; Pisarevskii, A.M.; Polozova, I.P.; Shults, M.M.

1986-06-01

209

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

NASA Astrophysics Data System (ADS)

The speciation and molal formation quotients for the complexation of aluminum with sulphate were measured based on potentiometric and solubility experiments. Potentiometric titrations, utilizing a hydrogen-electrode concentration cell, were performed from 50 to 125°C at ionic strengths of 0.1, 0.3 and 1.0 molal in aqueous NaCl media. Two aluminum-sulphate species, AlSO 4+and Al(SO 4) 2-, were identified from the titration data and the formation quotients for these species were modeled by empirical equations to describe their temperature and ionic strength dependencies. Thermodynamic parameters for the complexation reactions were obtained by differentiating the empirical equations with respect to temperature. The thermodynamic quantities obtained for the formation of AlSO 4+ at 50°C and infinite dilution are: logK 1 = 3.7 ± 0.4, ?H 1° = -10 ± 30 kJ · mol -1, ?S 1° = 40 ± 100 J · K -1 · mol -1 and ?C° p1 = 1900 ± 800 J · K -1 · mol -1; whereas the values for Al(SO 4) 2- are: logK 2 = 5.6 ± 0.7, ?H 2° = 10 ± 50 kJ · mol -1, ?S 2° = 100 ± 100 J · K -1 · mol -1 and ?C° p2 = 2800 ± 800 J · K -1 · mol -1. A solubility study, which was undertaken to verify the 50°C potentiometric data, was performed by reacting powdered gibbsite (Al(OH) 3) with sulphate solutions at 10 -3.5 and 10 -4 molal H +, total sulphate concentrations from 0.005 to 0.080 molal, and 0.1 and 1.0 molal ionic strength in aqueous NaCl media. The results of the solubility study are in good agreement with the potentiometric data and establish that Al-sulphate complexation substantially enhances the equilibrium solubility of gibbsite.

Ridley, Moira K.; Wesolowski, David J.; Palmer, Donald A.; Kettler, Richard M.

1999-02-01

210

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

2014-01-01

211

Linear Titration Curves of Acids and Bases.  

PubMed

The Henderson-Hasselbalch equation, by a simple transformation, becomes pH - pK = pA - pB, where pA and pB are the negative logarithms of acid and base concentrations. Sigmoid titration curves then reduce to straight lines; titration curves of polyelectrolytes, to families of straight lines. The method is applied to the titration of the dipeptide glycyl aminotricarballylic acid, with four titrable groups. Results are expressed as Cartesian and d'Ocagne nomograms. The latter is of a general form applicable to polyelectrolytes of any degree of complexity. PMID:17738750

Joseph, N R

1959-05-29

212

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

SciTech Connect

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

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

1995-12-01

213

Nanopore back titration analysis of dipicolinic acid.  

PubMed

Here, we report a novel label-free nanopore back titration method for the detection of dipicolinic acid, a marker molecule for bacterial spores. By competitive binding of the target analyte and a large ligand probe to metal ions, dipicolinic acid could be sensitively and selectively detected. This nanopore back titration approach should find useful applications in the detection of other species of medical, biological, or environmental importance if their direct detection is difficult to achieve. PMID:25074707

Han, Yujing; Zhou, Shuo; Wang, Liang; Guan, Xiyun

2015-02-01

214

Use of potentiometric fluorophores in the measurement of mitochondrial reactive oxygen species.  

PubMed

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

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

2014-01-01

215

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 titrations are to be done in triplicate. I. Standardization of AgNO3 solution 1. The Determination of Chloride by Titration with an Adsorption Indicator Discussion In this titration, the anionic adsorption

Nazarenko, Alexander

216

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

SciTech Connect

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

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

1988-05-01

217

Title: Titration_DB: Storage and Analysis of NMR-monitored Protein pH Titration Curves  

E-print Network

1 Title: Titration_DB: Storage and Analysis of NMR- monitored Protein pH Titration Curves' pKa values from the titration database for 1 H data........................2 Table 2: List of all ..................................................................................................................................................22 #12;2 Tables Table 1: List of all extracted `primary' pKa values from the titration database for 1

McIntosh, Lawrence P.

218

A high-resolution titrator: a new approach to studying binding sites of microbial biosorbents.  

PubMed

The high-resolution potentiometric titration was used as a physico-chemical method to study the acid properties of selected biosorbent materials in order to quantify the functional acidic groups for sorption and to determine their affinities by considering their partial or total ionization equilibrium reactions. The Gran's method and the Henderson-Hasselbach's equation were employed in establishing the partition of the total acidity as associated with strong, weak and very weak acidic chemical active groups. The differences in the total organic acidity (A(TO)) for the two selected types of bacteria and two mycelia revealed by this method were explained by the chemical composition of their cell walls. The total organic acidities obtained were 3.87 me g(-1) for Thiobacillus ferrooxidans, 1.31 me g(-1) for Corynebacterium glutamicum, 0.81 me g(-1) for Aspergillus niger and 2.54 me g(-1) for Rhizopus arrhizus. The links between the activity of protons and the sorption capacities of the selected bioorganic matters were established. Sorption of lead by C. glutamicum and R. arrhizus biomass indicated an optimum pH of 6. It appeared that 64% (Pb(uptake)=0.48 me g(-1)) and 38% (Pb(uptake)=0.28 me g(-1)) of A(TO) were involved during lead sorption onto R. arrhizus and C. glutamicum, respectively. The applications of titration techniques become a powerful tool for the characterization of heterogeneous materials involved in biosorption and bioremediation processes. PMID:15707630

Naja, Ghinwa; Mustin, Christian; Volesky, Bohumil; Berthelin, Jacques

2005-02-01

219

Potentiometric determination of the dissociation constants of L-histidine, proline and tryptophane in various hydroorganic media.  

PubMed

The dissociation constant values of L-histidine, proline and tryptophane were determined at 25 +/- 0.1 degrees C by potentiometric pH titration in pure water and different hydroorganic solvent media. The organic solvents used were methanol, ethanol, N,N-dimethylformamide, dimethyl sulfoxide, acetone and dioxane. Initial estimates of the dissociation constant values of the different amino acids studied have been refined with ESAP2M computer program. It was observed that changing the medium permittivity as the solvent is enriched in methanol or ethanol has little influence on the pK*(a) values of the amino acids studied. The results obtained are discussed in terms of average macroscopic properties of the mixed solvents and the possible variation in microheterogeneity of the salvation shells around the solute. PMID:18966065

Azab, H A; El-Nady, A M; El-Shatoury, S A; Hassan, A

1994-08-01

220

High-temperature carbon monoxide potentiometric sensor  

SciTech Connect

These sensors have been used in industrial alarm and control systems for monitoring and control of the oxygen concentration in a gas stream and for the control of air-fuel ratio in internal combustion engines as in automobiles. A high-temperature potentiometric CO sensor was developed by coating a mixture of CuO/ZnO over one of the platinum electrodes of a cell with a yttria-stabilized zirconia solid electrolyte. It showed good CO sensing characteristics over the temperature range of 450-550 C and concentration range of 0-10,000 ppm of CO in air. In particular, high sensitivity coupled with reasonably fast response and baseline recovery characteristics were observed at 450 C for CO concentration below 3,000 ppm. The sensing mechanism and operating system were adequately described by a proposed mathematical model. The model relates the induced cell EMF to the various rate phenomena occurring in the oxide layer such as diffusion, adsorption, and surface catalytic oxidation of the adsorbed carbon monoxide by the gaseous oxygen.

Li, N.; Tan, T.C.; Zeng, H.C. (National Univ. of Singapore (Singapore))

1993-04-01

221

Cell surface groups of two picocyanobacteria strains studied by zeta potential investigations, potentiometric titration, and infrared spectroscopy  

Microsoft Academic Search

In order to clarify the role of picocyanobacteria in aquatic biogeochemical processes (e.g., calcite precipitation), cell surface properties need to be investigated. An experimental study of the cell surface characteristics of two Synechococcus-type unicellular autotrophic picocyanobacterial strains was carried out. One strain was isolated from Lake Plön and contained phycocyanin, the other strain came from Lago Maggiore and was rich

Maria Dittrich; Sabine Sibler

2005-01-01

222

Interbiopolymer complexing between ?-lactoglobulin and low- and high-methylated pectin measured by potentiometric titration and ultrafiltration  

Microsoft Academic Search

The interactions between proteins and polysaccharides are of great interest to the food industry. Few studies have been carried out on diluted ?-lactoglobulin\\/pectin systems and none has provided a complete investigation on the nature of the interactions involved. The two main objectives of this study were to determine the conditions for the formation of complexes and to identify the type

Maude Girard; Sylvie L Turgeon; Sylvie F Gauthier

2002-01-01

223

Student Construction of a Gel-Filled Ag/AgCl Reference Electrode for Use in a Potentiometric Titration  

NASA Astrophysics Data System (ADS)

Electrochemistry can be one of the more difficult subjects in chemistry, especially for high school students. Tools are needed to help illustrate the practical use of the Nernst equation, half-cell voltages, redox reactions, etc. Instructions for the preparation of a Ag/AgCl "reference"-type electrode that uses a gel-type matrix are given. The construction steps for the reference electrode have been used successfully by our students to construct their own electrodes. In addition, construction steps are provided for a very sturdy Pt-nichrome "inert" electrode, which can be used many times. Together, these two electrodes, along with a multivoltmeter, have been used successfully by our students to determine the percent of iron in Fe(NH4)2(SO4)2 and in Fe2O2 unknowns purchased commercially.

Thomas, James M.

1999-01-01

224

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

225

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

226

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

227

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

228

Acid Rain Analysis by Standard Addition Titration.  

ERIC Educational Resources Information Center

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

Ophardt, Charles E.

1985-01-01

229

Potentiometric surface of the middle Potomac Aquifer in Virginia 1993  

USGS Publications Warehouse

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

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

1994-01-01

230

Potentiometric surface of the lower Potomac Aquifer in Virginia 1993  

USGS Publications Warehouse

Ground-water level measurements from 17 wells in the lower Potomac aquifer in the Coastal Plain Physiographic Province of Virginia in 1993 were used to prepare a map of the potentiometric surface of the aquifer. The map shows the potentiometric surface of the lower Potomac aquifer indicating a regional trend toward the Chesapeake Bay and Atlantic Ocean. The potentiometric-surface data indicate that there are two cones of depression, one around well fields in Henrico County and the other around large well fields in Isle of Wight County and Franklin, Virginia. The highest ground-water-level measurement was 47 feet above sea level in southeast Southampton County, and the lowest ground-water-level measurement was 161 feet below sea level in the southeast area of Isle of Wight County near Franklin, Virginia.

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

1994-01-01

231

Potentiometric and spectroscopic studies on aluminium(III) complexes of some catechol derivatives.  

PubMed

The interactions of aluminium(III) ion with the triprotic catechol derivatives (H3L), 2,3-dihydroxybenzoic acid (2,3-DHBA), 3,4-dihydroxyphenylacetic acid (3,4-DHPA), 3,4-dihydroxybenzoic acid (3,4-DHBA), and 3,4-dihydroxyhydrocinnamic acid (3,4-DHHCA) were investigated in aqueous solution at 25.0 degrees C. The Calvin-Bjerrum titration method was adopted for the determination of formation constants of proton-ligand and aluminium(III)-ligand complexes. Potentiometric and spectroscopic results indicated that these catechol derivatives exhibit a true bidentate character. The chelation occurs via their catecholate sites, with the exception of 2,3-DHBA. In the case of 2,3-DHBA complexes, the dominant species are either the salicylate type (COO-, O-) or catecholate type (O-, O-) complex. The protonation constants of ligands and their formation constants of Al(III) complexes were also correlated. The order of decreasing stabilities of complexes is: 3,4-DHPA>3,4-DHBA>3,4-DHHCA>2,3-DHBA. PMID:15304983

Türkel, Naciye; Berker, Melek; Ozer, Ulviye

2004-08-01

232

Potentiometric sensing utilizing paper-based microfluidic sampling.  

PubMed

A new approach to potentiometric sensing utilizing paper-based microfluidic sampling is studied in this work. A solid-contact ion-selective electrode and a solid-contact reference electrode are pressed against a filter paper into which the sample solution is absorbed. The filter paper acts simultaneously as a sampling unit and as a sample container during potentiometric sensing. The paper substrates containing standard and sample solutions are disposable, while the sensors are used multiple times. The analytical method presented here opens new possibilities for economically and ecologically sound measurements of ions in various samples. PMID:24647405

Cui, Jingwen; Lisak, Grzegorz; Strzalkowska, Sylwia; Bobacka, Johan

2014-05-01

233

Microculture virus titration--a simple colourimetric assay for influenza virus titration.  

PubMed

Influenza antigens can be detected by several well established methods. However, when it is important to determine the titre of infective virions, a bioassay should be employed. The standard and the most widely used tests for influenza infectivity are titration carried out in embryonated hen eggs, or the plaque assay employing tissue culture techniques. A simple colourimetric assay for influenza virus detection and titration is described. Samples of allantoic fluid or mice lung homogenates were used to infect MDCK cultures in microplate wells. After an incubation period, the tetrazolium (MTT) colourimetric assay was used to determine cell viability, and when compared to untreated culture control enabled the detection and titration of several influenza strains. When samples were assayed simultaneously in embryonated eggs and by the MCVT method, good correlation in determined titres was obtained. The availability of an additional method for influenza titration allows more flexibility in the choice of titration method according to the specific needs of the study. Furthermore, this method lends itself to full automatization. Similar procedures should also be applicable to titration of other cytopathic viruses. PMID:7769039

Levi, R; Beeor-Tzahar, T; Arnon, R

1995-03-01

234

An Olfactory Indicator for Acid-Base Titrations.  

ERIC Educational Resources Information Center

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

Flair, Mark N.; Setzer, William N.

1990-01-01

235

Simple and Automated Coulometric Titration of Acid Using Nonisolated Electrodes  

ERIC Educational Resources Information Center

Coulometric titrations involve the quantification of analyte by measurements of current and time. In most coulometric titrations, the anode and cathode are placed in isolated cells that are connected by a salt bridge. By contrast, the experiments described here involve coulometric titrations (of acidic protons in solution) using a silver anode and…

Kuntzleman, Thomas S.; Kenney, Joshua B.; Hasbrouck, Scott; Collins, Michael J.; Amend, John R.

2011-01-01

236

Titration of dengue viruses by immunofluorescence in microtiter plates.  

PubMed Central

A fast, reliable, and inexpensive method was developed for titration of dengue viruses in microtiter plates with an indirect fluorescent-antibody technique. No significant differences were found in median infectious dose endpoints of samples titrated in microtiter plates as compared with titrations in multichambered slides. Images PMID:6392318

Schoepp, R J; Beaty, B J

1984-01-01

237

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

238

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 and calibrate a computational model­based titration algorithm for predictable laser dosimetry ranging from damage at different percentages of a reference titration energy dose. Experimental verification

Palanker, Daniel

239

Catalytic Methanol Oxidation Site Titration with Organic Bases During  

E-print Network

Catalytic Methanol Oxidation Site Titration with Organic Bases During Catalysis: Selectivity titration of protons with organic bases to control the densities of acid sites in Keggin clusters of Keggin structures was measured by titration of Brønsted acid sites with a sterically hindered pyridine (2

Iglesia, Enrique

240

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

PubMed Central

Manganese(III) complexes of three fluorophilic salen derivatives were used to prepare ion-selective electrodes (ISEs) with ionophore-doped fluorous sensing membranes. Because of their extremely low polarity and polarizability, fluorous media are not only chemically very inert but also solvate potentially interfering ions poorly, resulting in a much improved discrimination of such ions. Indeed, the new ISEs exhibited selectivities for CO32? that exceed those of previously reported ISEs based on non-fluorous membranes by several orders of magnitude. In particular, the interference from chloride and salicylate was reduced by two and six orders of magnitude, respectively. To achieve this, the selectivities of these ISEs were fine-tuned by addition of non-coordinating hydrophobic ions (i.e., ionic sites) into the sensing membranes. Stability constants of the anion–ionophore complexes were determined from the dependence of the potentiometric selectivities on the charge sign of the ionic sites and the molar ratio of ionic sites and the ionophore. For this purpose, a previously introduced fluorophilic tetraphenylborate and a novel fluorophilic cation with a bis(triphenylphosphoranylidene)ammonium group, (Rf6(CH2)3)3PN+P(Rf6(CH2)3)3, were utilized. The optimum CO32? selectivities were found for sensing membranes composed of anionic sites and ionophore in a 1:4 molar ratio, which results in the formation of 2:1 complexes with CO32? with stability constants up to 4.1 × 1015. As predicted by established theory, the site-to-ionophore ratios that provide optimum potentiometric selectivity depend on the stoichiometries of the complexes of both the primary and the interfering ions. However, the ionophores used in this study give examples of charges and stoichiometries previously neither explicitly predicted by theory nor shown by experiment. The exceptional selectivity of fluorous membranes doped with these carbonate ionophores suggests their use not only for potentiometric sensing but also for other types of sensors, such as the selective separation of carbonate from other anions and the sequestration of carbon dioxide. PMID:22070518

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

2011-01-01

241

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

242

Porous silicon as a substrate material for potentiometric biosensors  

Microsoft Academic Search

For the first time porous silicon has been investigated for the purpose of application as a substrate material for potentiometric biosensors operating in aqueous solutions. Porous silicon was prepared from differently doped silicon substrates by a standard anodic etching process. After oxidation, penicillinase, an enzyme sensitive to penicillin, was bound to the porous structure by physical adsorption. To characterize the

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

1996-01-01

243

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

244

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

SciTech Connect

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

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

1999-02-01

245

Fluorescent cationic probes of mitochondria. Metrics and mechanism of interaction.  

PubMed Central

Mitochondria strongly accumulate amphiphilic cations. We report here a study of the association of respiring rat liver mitochondria with several fluorescent cationic dyes from differing structural classes. Using gravimetric and fluorometric analysis of dye partition, we find that dyes and mitochondria interact in three ways: (a) uptake with fluorescence quenching, (b) uptake without change in fluorescence intensity, and (c) lack of uptake. For dyes that quench upon uptake, the extent of quenching correlates with the degree of aggregation of the dye to dimers, as predicted by theory (Tomov, T.C. 1986. J. Biochem. Biophys. Methods. 13:29-38). Also predicted is the relationship observed between quenching and the mitochondria concentration when constant dye is titrated with mitochondria. Not predicted is the relationship observed between quenching and dye concentration when constant mitochondria are titrated with dye. Because a limit to dye uptake exists, in this case, the degree of quenching decreases as dye is added. A Langmuir isotherm analysis gives phenomenological parameters that predict quenching when it is observed as a function of dye concentration. By allowing for a decrease in membrane potential, caused by incorporation of cationic dye into the lipid bilayer, a modification of the Tomov theory predicts the dye titration data. We present a model of cationic dye-mitochondria interaction and discuss the use of these as probes of mitochondrial membrane potential. PMID:2605307

Bunting, J R; Phan, T V; Kamali, E; Dowben, R M

1989-01-01

246

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

247

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

248

Protein detection with potentiometric aptasensors: a comparative study between polyaniline and single-walled carbon nanotubes transducers.  

PubMed

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

Düzgün, Ali; Imran, Hassan; Levon, Kalle; Rius, F Xavier

2013-01-01

249

Determination of protonation constants by coulometric titration.  

PubMed

Application of coulometric titration to the determination of the protonation constants of acids and bases offers several advantages because of its simplicity, precision and accuracy. This procedure is rapid and requires only one calibration solution of strong acid in the same solvent and at the same ionic strength as the solution of acid (or base) being investigated. The procedure seems to be especially advantageous in the case of non-aqueous or mixed solvents having amphiprotic character. The validity of the method has been checked with several substances in water, 95% ethanol and ethylene glycol. PMID:18964325

G?ab, S; Skrzydlewska, E; Hulanicki, A

1987-04-01

250

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.; Dixon, Joann F.

2009-01-01

251

A potentiometric protein sensor built with surface molecular imprinting method.  

PubMed

Surface molecular imprinting, as compared to molecular imprinted bulk polymers, has the advantages of higher re-occupation percentage of the reception sites, fast response, integration of sensing element and transducer, etc. In this study, a potentiometric protein sensor was developed based on the surface molecular imprinting technique. Using the self-assembled monolayers of alkanethiol with hydroxyl terminal groups as the matrix material, and target protein molecules as the template, the sensing layer was created on the surface of the gold-coated silicon chip-an electrochemical transducer. Potentiometric measurement demonstrated that the sensor could selectively detect myoglobin or hemoglobin molecules, either with or without the presence of other protein molecules in the same solution. PMID:18514502

Wang, Yantian; Zhou, Yanxiu; Sokolov, Jonathon; Rigas, Basil; Levon, Kalle; Rafailovich, Miriam

2008-09-15

252

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

PubMed

A simple and generalized approach to build electrochemical sensors for wearable devices is presented. Commercial cotton yarns are first turned into electrical conductors through a simple dyeing process using a carbon nanotube ink. These conductive yarns are then partially coated with a suitable polymeric membrane to build ion-selective electrodes. Potentiometric measurements using these yarn-potentiometric sensors are demonstrated. Examples of yarns that can sense pH, K(+) and NH4(+) are presented. In all cases, these sensing yarns show limits of detection and linear ranges that are similar to those obtained with lab-made solid-state ion-selective electrodes. Through the immobilization of these sensors in a band-aid, it is shown that this approach could be easily implemented in a wearable device. Factors affecting the performance of the sensors and future potential applications are discussed. PMID:23775189

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

2013-09-21

253

Lead biosorption study with Rhizopus arrhizus using a metal-based titration technique.  

PubMed

Acid-base and metal-based potentiometric titration methods were used to analyze sorption mechanisms of lead by Rhizopus arrhizus fungal biomass. Biosorption was not considered globally but as the result of successive sorption reactions on various binding sites with different selectivities. Precipitation occurred rapidly when lead concentration increased. Lead was sorbed essentially by carboxylic groups and by phosphates and sulfonates (less abundant) of the organic matter. The lead affinity to carboxylic, sulfonate and phosphate binding sites depended on the association coefficient with proton or counter-ion and on the spatial distribution of the surface sites promoting the formation of mono- or bi-dentate complexes. Chemical bonds and binding sites were confirmed using microscopic and spectroscopic techniques (IR, MET-EDAX). It appeared that although the total organic acidity was reached, number of ionized and free carboxylic groups were not involved in lead sorption reactions. In spite of lead speciation in the solution, surface micro-precipitation was observed and the two processes, surface adsorption and micro-precipitation, are sequential and possibly overlapping. At low concentrations (<10(-6) M) adsorption is the dominant phenomenon and beyond (>10(-5) M) surface clusters appeared before the predicted solution precipitation phenomenon. PMID:15979634

Naja, Ghinwa; Mustin, Christian; Berthelin, Jacques; Volesky, Bohumil

2005-12-15

254

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

255

Porous silicon as a substrate material for potentiometric biosensors  

NASA Astrophysics Data System (ADS)

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

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

1996-01-01

256

Ciprofloxacin-imprinted polymeric receptors as ionophores for potentiometric transduction  

Microsoft Academic Search

A 3D-mirror synthetic receptor for ciprofloxacin host–guest interactions and potentiometric transduction is presented. The host cavity was shaped on a polymeric surface assembled with methacrylic acid or 2-vinyl pyridine monomers by radical polymerization. Molecularly imprinted particles were dispersed in 2-nitrophenyl octyl ether and entrapped in a poly(vinyl chloride) matrix. The sensors exhibited a near-Nernstian response in steady state evaluations. Slopes

Helena M. V. Oliveira; Felismina T. C. Moreira; M. Goreti F. Sales

2011-01-01

257

Bivoltametric titrations using electrodes with innovative geometry.  

PubMed

Electrodes with different surface areas were investigated for the determination of reversible, quasireversible, irreversible or electroinactive substrates. Two kinds of electrodes were constructed, a helical electrode with a given asymmetry and a platinum array electrode with a variable area. These electrodes were applied for the cerimetry of ammonium iron(II) sulfate and for the bromatometry of various organic substances. The theoretically derived effects on the shape of the voltametric titration curve are verified experimentally. It is possible to sharpen one side of the peak and to broaden the other side, depending on the system and the side of the peak one is interested in. It is possible to improve the bivoltametric determination of hydroquinone, benzocaine and sulfaguanidine by bromatometry by the directed employment of electrodes of different areas. For the bromatometric determination of electrochemically irreversible substrates the use of the electrode geometries proposed is a way to obtain a sharp bend and a steep decrease of titration curves with low values of the constant current which is a basic requirement for the accuracy. PMID:15048351

Surmann, P; Peter, B; Stark, C

1996-09-01

258

Titration of chaos with added noise  

PubMed Central

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

Poon, Chi-Sang; Barahona, Mauricio

2001-01-01

259

A dipstick sensor for coulometric acid-base titrations  

Microsoft Academic Search

By performing an acid-base titration by coulometric generation of OH? or H+ ions at an inert electrode in close proximity to the pH-sensitive gate of an ISFET, it is possible to determine the acid or base concentration of a solution using the ISFET as an indicator device for the equivalence point in the titration curve. Typical values for the titration

W. Olthuis; Schoot van der B. H; F. Chavez; P. Bergveld

1989-01-01

260

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

261

High throughput continuous titration based on a flow ratiometry controlled with feedback-based variable triangular waves and subsequent fixed triangular waves.  

PubMed

We propose a new approach for high-throughput continuous titration based on a flow ratiometry. The method was applied to potentiometric titrations of acids and bases. A base solution, the flow rate F(B) of which was varied in response to controller output voltage V(c), was merged with an acid solution under constant total (acid+base) flow rate. Downstream, the pH of the mixed solution was measured with a flow-through glass electrode. Initially, V(c), and thus F(B) was increased linearly. At the instant the equivalence point (EP) was sensed, the ramp direction of V(c) was reversed from upward to downward. The direction was reversed to upward when EP was sensed again. Such the feedback-based operation gives a triangular waveform of V(c), because there is a delay corresponding mainly to the transit time of merged solutions to reach the sensor. The value of V(c) that gives EP composition, V(E), was estimated by averaging the most recent maximum and minimum values of V(c). Next, fixed triangular waves of V(c) was used to control F(B). The amplitude and the scan rate of the waves were fixed narrower and faster, respectively, than those in the feedback-based operation in order to improve the throughput rate. The EP can be located as long as the scan range covers V(E). These automated processes limited the titration to just the narrow range around EP, and thus realized extremely high throughput rate of maximally 17.6 titrations per minute (=3.4s per titration) at R.S.D.=0.35%. PMID:18970249

Tanaka, Hideji; Baba, Tsutomu

2005-10-15

262

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

SciTech Connect

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

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

1993-09-01

263

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

264

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

265

On the invention of conductimetric titration.  

PubMed

In contrast to the earlier statement of one of the authors according to which conductimetric titration was invented by Küster and Grüters in 1903, it is shown that Ostwald made use of this analytical method as early as the nineties of the past century. Prior to Ostwald's work, however, papers appeared in which conductimetric curves were shown, with statements about their different characteristics in the case of reaction between weak and strong acids and bases. The first of these seems to be due to Kohlrausch [together with one of his co-workers, Kreichgauer (1885)]. It does not seem to have occurred to them, however, to use this phenomenon for the purposes of analytical chemistry, namely for titrimetry. PMID:18963516

Szabadváry, F; Chalmers, R A

1983-12-01

266

Infrared titration of aqueous sulfuric acid  

SciTech Connect

This paper presents the infrared (IR) titration of aqueous sulfuric acid solutions (0.50 M) obtained by the attenuated total reflection (ATR) sampling technique. After subtracting the water spectra, the spectra of the ionic species of H{sub 2}SO{sub 4} in the 0--14 pH range were separated by factor analysis (FA) which also gave their abundance. The results were in agreement with the theoretical calculation of the distribution of the species. Three sulfate species were found: HSO{sub 4}{sup {minus}}, SO{sub 4}{sup 2{minus}}, and HSO{sub 4}{sup {minus}}/HCl. The latter stands for the bisulfate--hydronium complex formed by the addition of HCl to obtain measurements in the 0--0.47 pH range. For 0.50 M sulfuric acid, the comparison between the experimentally IR-determined quantities and the theoretical values gave a mean activity coefficient of 0.12 {+-} 0.04, a value comparable to that from electrochemical measurements. Three types of water were quantitatively determined in the solutions: acidic water, basic water, and neutral water. The latter is always present while the two others are present in the low and high pH range, respectively. Another type of water strongly associated with the sulfates is also present. Moreover, knowledge of the behavior of the different types of water as the titration proceeded permitted us to give the details of the neutralization reactions of aqueous sulfuric acid by sodium hydroxide.

Max, J.J.; Menichelli, C.; Chapados, C.

2000-03-30

267

Continuous on-line feedback based flow titrations. Complexometric titrations of calcium and magnesium.  

PubMed

The methodology of continuous feedback-based flow titrations and the principle of compensating errors [Anal. Chem. 72 (2000) 4713; Anal. Chim. Acta 435 (2001) 289] were applied to the determination of calcium and magnesium ions with EDTA. The flow of the titrant, EDTA, varied linearly in response to a controller output voltage while the total flow (F(T), the sum of the metal ion sample flow and the titrant flow) was held constant. The sample was pre-doped with a metal ion indicator; the status of the indicator color in the mixed stream was monitored by an optical detector and was used for governing the controller output as well as for interpreting the results of the titrations. The titrant flow initially ramped upward linearly. As a change in the color corresponding to the equivalence point was sensed by the detector, the controller output (instantaneous value V(H)) reversed its ramp direction, thus decreasing the titrant flow linearly at the same ramp rate. When the predefined absorbance corresponding to the equivalence point was sensed again, the controller voltage (instantaneous value V(L)) was ramped in reverse once more, going upward. Because of the lag time between a change in the controller output and its effect being sensed by the detector, the controller voltage corresponding to the actual equivalence point was the average of V(H) and V(L). Continuous sensor-governed operation of the controller resulted in a triangular waveform. The mean of this waveform during any cycle gives the equivalence point controller voltage V(E). This principle allowed true titrations with good reproducibility (0.2-0.7% R.S.D.) and throughput (33-42 s per titration). PMID:18969033

Jo, Kyoo Dong; Dasgupta, Purnendu K

2003-05-28

268

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

269

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

270

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

271

pH Static Titration: A Quasistatic Approach  

ERIC Educational Resources Information Center

The pH-static titration is applicable to those systems where at least two types of reactions occur in comparable intensities. The commonalities in titrimetric procedure realized according to pH-static titration, irrespective of the kind of chemical processes occurring are discussed.

Michalowski, Tadeusz; Toporek, Marcin; Rymanowski, Maciej

2007-01-01

272

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

273

Students' integration of multiple representations in a titration experiment  

NASA Astrophysics Data System (ADS)

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

Kunze, Nicole M.

274

Calculation of titratable acidity from urinary stone risk factors  

Microsoft Academic Search

Calculation of titratable acidity from urinary stone risk factors. Using urine samples and standard solutions, this study demonstrates that the existing procedure for measuring titratable acidity in the urine is not reliable and may result in overestimates of up to 25%. The accuracy is affected by loss of CO2, the presence of uric acid crystals, and the precipitation of calciumphosphate

Dirk J Kok; John Poindexter; Charles Y C Pak

1993-01-01

275

SIMULTANEOUS TITRIMETRIC DETERMINATION OF BICARBONATE AND TITRATABLE ACID OF URINE  

Microsoft Academic Search

An acid-titration method for the determination of bicarbonate and titratable acid in the one sample of urine is described. The method needs only one manipulation of the sample of urine, and was devised to simplify routine laboratory methodology. The accuracy and precision of the urinary bicarbonate method during routine laboratory use is comparable to that obtained by using the Van

AZ Györy; KDG Edwards

1967-01-01

276

A potentiometric biosensor for d-amygdalin based on a consolidated biocomposite membrane  

Microsoft Academic Search

A new potentiometric biosensor for d-amygdalin based on a consolidated biocomposite membrane has been designed. The manufacturing technique involved a simple compression of dry components presenting an ideal technology for the mass production of potentiometric biosensor devices. The effect of high pressures applied during the preparation of a d-amygdalin biosensor membrane was studied. The immobilisation of ?-glucosidase was improved by

Arben Merkoçi; Susana Braga; Esteve Fàbregas; Salvador Alegret

1999-01-01

277

Determination of Orciprenaline Using a Flow Injection Analysis System with Sequential Potentiometric and Spectrophotometric Detection  

Microsoft Academic Search

This work describes an attempt to have a flow injection analysis (FIA) system for Orciprenaline with potentiometric and spectrophotometric detectors working sequentially. The potentiometric detection was performed using an orciprenaline ion-selective electrode made of orciprenaline ion-associate with phosphotungstic acid incorporated in a PVC matrix membrane, followed by sequential spectrophotometric detection of the same sample using the reaction of orciprenaline with

Rasha Mohamed El Nashar

2008-01-01

278

Linking bacteria-metal interactions to mineral attachment: A role for outer sphere complexation of cations?  

E-print Network

of hard acid divalent cations with bacterial cells walls may influence the mechanisms and extent these models characterize the reactivity of the bacterial cell wall via acid-base titrations that are utilized laboratory based studies have found little reactivity between bacteria and quartz surfaces (e.g. Yee et al

Roberts, Jennifer A.

279

Potentiometric and spectrophotometric pKa determination of water-insoluble compounds: validation study in a new cosolvent system.  

PubMed

In this paper the validation of pKa determination in MDM-water mixtures is presented. The MDM-water mixture is a new multicomponent cosolvent mixture (consisting of equal volumes of methanol, dioxane and acetonitrile, as organic solvents) that dissolves a wide range of poorly water-soluble compounds. The cosolvent dissociation constants (p(s)Ka) of 50 chemically diverse compounds (acids, bases and ampholytes) were measured in 15-56 wt% MDM-water mixtures by potentiometric or spectrophotometric titration and the aqueous pKa values obtained by extrapolation. Three different extrapolation procedures were compared in order to choose the best extrapolation in MDM-water mixture using a sub-set of 30 water-soluble compounds. The extrapolated results are in good agreement with pKa values measured in aqueous medium. No significant difference was found among these extrapolation procedures thus the widely used Yasuda-Shedlovsky plot was proposed for MDM cosolvent also. Further we also present that the single point estimation based on measurement in 20%/v MDM-mixture using a general calibration equation may be suitable for rapid pKa determination in the early phase of drug research. PMID:17386575

Völgyi, Gergely; Ruiz, Rebeca; Box, Karl; Comer, John; Bosch, Elisabeth; Takács-Novák, Krisztina

2007-02-01

280

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

281

Geochemical reactions and dynamics during titration of a contaminated groundwater with high uranium, aluminum, and calcium  

NASA Astrophysics Data System (ADS)

This study investigated possible geochemical reactions during titration of a contaminated groundwater with a low pH but high concentrations of aluminum, calcium, magnesium, manganese, and trace contaminant metals/radionuclides such as uranium, technetium, nickel, and cobalt. Both Na-carbonate and hydroxide were used as titrants, and a geochemical equilibrium reaction path model was employed to predict aqueous species and mineral precipitation during titration. Although the model appeared to be adequate to describe the concentration profiles of some metal cations, solution pH, and mineral precipitates, it failed to describe the concentrations of U during titration and its precipitation. Most U (as uranyl, UO 22+) as well as Tc (as pertechnetate, TcO 4-) were found to be sorbed and coprecipitated with amorphous Al and Fe oxyhydroxides at pH below ˜5.5, but slow desorption or dissolution of U and Tc occurred at higher pH values when Na 2CO 3 was used as the titrant. In general, the precipitation of major cationic species followed the order of Fe(OH) 3 and/or FeCo 0.1(OH) 3.2, Al 4(OH) 10SO 4, MnCO 3, CaCO 3, conversion of Al 4(OH) 10SO 4 to Al(OH) 3,am, Mn(OH) 2, Mg(OH) 2, MgCO 3, and Ca(OH) 2. The formation of mixed or double hydroxide phases of Ni and Co with Al and Fe oxyhydroxides was thought to be responsible for the removal of Ni and Co in solution. Results of this study indicate that, although the hydrolysis and precipitation of a single cation are known, complex reactions such as sorption/desorption, coprecipitation of mixed mineral phases, and their dissolution could occur simultaneously. These processes as well as the kinetic constraints must be considered in the design of the remediation strategies and modeling to better predict the activities of various metal species and solid precipitates during pre- and post-groundwater treatment practices.

Gu, Baohua; Brooks, Scott C.; Roh, Yul; Jardine, Philip M.

2003-08-01

282

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

SciTech Connect

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

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

2012-07-01

283

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

284

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

285

Novel titration method for surface-functionalised silica  

NASA Astrophysics Data System (ADS)

This paper describes three inexpensive and fast analytical methods to characterise grafted particle surfaces. The reaction of silica with (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane and N-(phosphonomethyl)iminodiacetic acid hydrate, respectively, leads to NH2-, SO3H- or COOH-functionalised silica, which were characterised by X-ray photoelectron spectrometry and titration in nonaqueous media as well as with two titration methods in a water-based environment. In the work presented, factors influencing the titrations are pointed out and solutions are presented to overcome these limiting factors are shown.

Hofen, Kai; Weber, Siegfried; Chan, Chiu Ping Candace; Majewski, Peter

2011-01-01

286

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

287

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

Buschmann, Michael

288

Total Acid Value Titration of Hydrotreated Biomass Fast Pyrolysis Oil: Determination of Carboxylic Acids and Phenolics with Multiple End-Point Detection  

SciTech Connect

Total acid value titration has long been used to estimate corrosive potential of petroleum crude oil and fuel oil products. The method commonly used for this measurement, ASTM D664, utilizes KOH in isopropanol as the titrant with potentiometric end point determination by pH sensing electrode and Ag/AgCl reference electrode with LiCl electrolyte. A natural application of the D664 method is titration of pyrolysis-derived bio-oil, which is a candidate for refinery upgrading to produce drop in fuels. Determining the total acid value of pyrolysis derived bio-oil has proven challenging and not necessarily amenable to the methodology employed for petroleum products due to the different nature of acids present. We presented an acid value titration for bio-oil products in our previous publication which also utilizes potentiometry using tetrabutylammonium hydroxide in place of KOH as the titrant and tetraethylammonium bromide in place of LiCl as the reference electrolyte to improve the detection of these types of acids. This method was shown to detect numerous end points in samples of bio-oil that were not detected by D664. These end points were attributed to carboxylic acids and phenolics based on the results of HPLC and GC-MS studies. Additional work has led to refinement of the method and it has been established that both carboxylic acids and phenolics can be determined accurately. Use of pH buffer calibration to determine half-neutralization potentials of acids in conjunction with the analysis of model compounds has allowed us to conclude that this titration method is suitable for the determination of total acid value of pyrolysis oil and can be used to differentiate and quantify weak acid species. The measurement of phenolics in bio-oil is subject to a relatively high limit of detection, which may limit the utility of titrimetric methodology for characterizing the acidic potential of pyrolysis oil and products.

Christensen, E.; Alleman, T. L.; McCormick, R. L.

2013-01-01

289

Modeling Precipitation and Sorption of Al, U and Co-contaminants during Titration of Acidic Sediments in Recirculation Flow-Through Experiments  

SciTech Connect

We conducted batch and recirculating column titration tests with contaminated acidic sediments with controlled CO2 in the headspace, and extended the geochemical model by Gu et al. (2003, GCA) to better understand and quantify the reactions governing trace metal fate in the subsurface. The sediment titration curve showed slow pH increase due to strong buffering by Al precipitation and CO2 uptake. Assuming precipitation of basaluminite at low saturation index (SI=-4), and decreasing cation exchange selectivity coefficient (kNa\\Al=0.3), the predictions are close to the observed pH and Al; and the model explains 1) the observed Ca, Mg, and Mn concentration decrease by cation exchange with sorbed Al, and 2) the decrease of U by surface complexation with Fe hydroxides at low pH, and precipitation as liebigite (Ca2UO2(CO3)3:10H2O) at pH>5.5. Without further adjustment geochemical parameters, the model describes reasonably well previous sediment and column titration tests without CO2 in the headspace, as well as the new large column test. The apparent inhibition of U and Ni decrease in the large column can be explained by formation of aqueous carbonate complexes and/or competition with carbonate for surface sites. These results indicated that ignoring labile solid phase Al would underestimate base requirement in titration of acidic aquifers.

Tang, Guoping [ORNL; Luo, Wensui [Institute of Urban Environment, Chinese Academy of Sciences; Brooks, Scott C [ORNL; Watson, David B [ORNL; Gu, Baohua [ORNL

2013-01-01

290

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

SciTech Connect

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

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

1999-06-16

291

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

292

The cation-? interaction.  

PubMed

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 forego 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 lysine or arginine side chains interact with phenylalanine, tyrosine, or tryptophan. In addition, countless studies have established the importance of the 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

2013-04-16

293

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

294

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

295

Titration Microcalorimetry Study: Interaction of Drug and Ionic Microgel System  

E-print Network

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

Tian, Y.

296

Cation-alkane interaction.  

PubMed

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

Premkumar, J Richard; Sastry, G Narahari

2014-12-01

297

Acid–base titration curves of solid humic acids  

Microsoft Academic Search

A direct discontinuous titration method with NaOH was developed to characterize the acid–base properties of complex natural polyelectrolytes, such as humic substances (HS). The classical batch procedure, suggested originally for examinations of resin-based ion exchanger, was modified to be applicable to HS; the modified method is suitable especially for the measurements of the titration curves of solid humic acids (HA).

Pavel Janoš; Sylvie K?íženecká; Libuše Madronová

2008-01-01

298

Retention of Cationic Starch onto Cellulose Fibres  

NASA Astrophysics Data System (ADS)

Three methods of cationic starch titration were used to quantify its retention on cellulose fibres, namely: (i) the complexation of CS with iodine and measurement of the absorbency of the ensuing blue solution by UV-vis spectroscopy; (ii) hydrolysis of the starch macromolecules followed by the conversion of the resulting sugars to furan-based molecules and quantifying the ensuing mixture by measuring their absorbance at a ? of 490 nm, using the same technique as previous one and; finally (iii) hydrolysis of starch macromolecules by trifluoro-acetic acid and quantification of the sugars in the resulting hydrolysates by high performance liquid chromatography. The three methods were found to give similar results within the range of CS addition from 0 to 50 mg per g of cellulose fibres.

Missaoui, Mohamed; Mauret, Evelyne; Belgacem, Mohamed Naceur

2008-08-01

299

Potentiometric analysis of water soluble cutting fluid-metal combinations  

SciTech Connect

The results of corrosion studies conducted by the University of Kansas under Contract G257763 for Allied-Signal Inc., Kansas City Division (KCD), are given. These potentiometric studies evaluate the corrosivity of two water soluble cutting fluids at varying concentrations on samples of 304 stainless steel, 6061-T6 aluminum, and beryllium copper. This testing serves two purposes: (1) to develop effective test procedures adaptable to existing KCD corrosion measurement equipment for corrosion analysis of cutting fluid-metals combinations, and (2) to understand the relative corrosiveness of the varying water soluble cutting fluids on different metals. The tests used were adapted from the American Society of Testing Materials (ASTM). Future testing will identify polarization techniques for establishing corrosion rates which will be used in evaluating both water soluble cutting fluids and other aqueous solutions used at KCD.

Kelley, E.E.

1991-12-01

300

CO2 Selective Potentiometric Sensor in Thick-film Technology  

PubMed Central

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

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

2008-01-01

301

Chromium(III) removal from water and wastewater using a carboxylate-functionalized cation exchanger prepared from a lignocellulosic residue.  

PubMed

This study concerns with the development of a new cation exchanger (SDGPMASPCOOH) carrying spacer (SP) group [CONH(CH(2))(2)NHCO(CH(2))(2)] and carboxylate functional group at the chain end. The preparation process was carried out through graft copolymerization of methacrylic acid onto sawdust, SD (a lignocellulosic residue) using ceric ammonium nitrate as an initiator. The poly(methacrylic acid) grafted SD (SDGPMA) was subsequently treated with thionyl chloride followed by ethylenediamine (transmidation) and succinic anhydride (carboxyfunctionalization) treatments. Infrared spectroscopy and potentiometric titrations were used to confirm graft copolymer formation and carboxylate functionalization. The effectiveness of the SDGPMASPCOOH in removing Cr(III) from water and wastewater was evaluated by the batch technique. The influence of different experimental parameters such as solution pH, contact time, absorbent dose, Cr(III) concentration and temperature on removal process was evaluated. The maximum Cr(III) removal was observed at the initial pH of 7.0. The Cr(III) was removed by SDGPMASPCOOH up to 99.3 and 92.6% from an initial concentration of 10 and 25 mg/L, respectively, at pH 7.0. Equilibrium time was reached within 4 h. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and Elovich equations. The data fitted very well to the pseudo-second-order rate expression. The Langmuir, Freundlich and Temkin equations were applied to the experimental isotherm data and the Langmuir model was found to be in better correlation with the experimental data. The monolayer adsorption capacity for Cr(III) removal was found to be 36.63 mg/g. The adsorption efficiency towards Cr(III) removal was tested using simulated tannery wastewater. The adsorbed Cr(III) on SDGPMASPCOOH can be recovered by treating with 0.1 M HCl. Four adsorption/desorption cycles were performed without significant decrease in removal capacity. The results showed that SDGPMASPCOOH developed in this study exhibited considerable adsorption potential for application in removal of Cr(III) from water and wastewaters. PMID:17905262

Anirudhan, T S; Radhakrishnan, P G

2007-12-15

302

Titration Force Microscopy on Supported Lipid Sergi Garcia-Manyes, Pau Gorostiza, and Fausto Sanz*,  

E-print Network

Titration Force Microscopy on Supported Lipid Bilayers Sergi Garcia-Manyes, Pau Gorostiza titration where the titration agent is a weak acid (attached to the AFM tip) with the particularity of being to the pKa of the surface under study and the other to the pKa of the titrating probe attached to the tip

Fernandez, Julio M.

303

Nano- and microsized zeolites as a perspective material for potentiometric biosensors creation  

NASA Astrophysics Data System (ADS)

A number of potentiometric biosensors based on coimmobilization of enzymes with different types of zeolite on pH-ion-sensitive field-effect transistor (ISFET) have been developed. Their working characteristics have been determined and compared.

Soldatkin, Oleksandr O.; Shelyakina, Margaryta K.; Arkhypova, Valentyna N.; Soy, Esin; Kirdeciler, Salih Kaan; Ozansoy Kasap, Berna; Lagarde, Florence; Jaffrezic-Renault, Nicole; Akata Kurç, Burcu; Soldatkin, Alexei P.; Dzyadevych, Sergei V.

2015-02-01

304

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

305

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

PubMed Central

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

Ismail, Fatma; Adeloju, Samuel B.

2010-01-01

306

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

E-print Network

transducers for highly sensitive potentiometric detection of protein immunoassays8 or DNA hybridization,7 immunoassays were developed earlier on the basis of liposomes containing fluorescent dyes13 or electroactive

Zhang, Liangfang

307

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

SciTech Connect

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

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

2008-01-01

308

The fluorenyl cation.  

PubMed

The fluorenyl cation is a textbook example for a 4? antiaromatic cation. However, contrasting results have been published on how the annelated benzene rings compensate the destabilizing effect of the 4? antiaromatic five-membered ring in its core. Whereas previous attempts to synthesize this cation in superacidic media resulted in undefined polymeric material only, we herein report that it can be generated and isolated in amorphous water ice at temperatures below 30?K by photolysis of diazofluorene. Under these conditions, the fluorenylidene is protonated by water to give the fluorenyl cation, which could be characterized spectroscopically. Its absorption in the visible-light range matches that previously obtained by ultrafast absorption spectroscopy, and furthermore, its IR spectrum could be recorded. The IR bands in amorphous ice very nicely match predictions from DFT and DFT/MM calculations, suggesting the absence of strong interactions between the cation and surrounding water molecules. PMID:25656782

Costa, Paolo; Trosien, Iris; Fernandez-Oliva, Miguel; Sanchez-Garcia, Elsa; Sander, Wolfram

2015-02-23

309

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

310

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

311

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

312

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

SciTech Connect

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

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

2010-01-01

313

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

PubMed

This study investigates uranium and technetium sorption onto aluminum and iron hydroxides during titration of acidic groundwater. The contaminated groundwater exhibits oxic conditions with high concentrations of NO(3)(-), SO(4)(2-), U, Tc, and various metal cations. More than 90% of U and Tc was removed from the aqueous phase as Al and Fe precipitated above pH 5.5, but was partially resolublized at higher pH values. An equilibrium hydrolysis and precipitation reaction model adequately described variations in aqueous concentrations of metal cations. An anion exchange reaction model was incorporated to simulate sulfate, U and Tc sorption onto variably charged (pH-dependent) Al and Fe hydroxides. Modeling results indicate that competitive sorption/desorption on mixed mineral phases needs to be considered to adequately predict U and Tc mobility. The model could be useful for future studies of the speciation of U, Tc and co-existing ions during pre- and post-groundwater treatment practices. PMID:20116923

Zhang, Fan; Parker, Jack C; Brooks, Scott C; Watson, David B; Jardine, Philip M; Gu, Baohua

2010-06-15

314

Fluorescence anisotropy-based salt-titration approach to characterize protein-nucleic acid interactions.  

PubMed

Many proteins bind nucleic acids (NA) via cationic residues that interact electrostatically with the anionic phosphate backbone of RNA or DNA. These electrostatic interactions are often insensitive to NA sequence and structure, but confer strong salt dependence to the binding interactions. In contrast, salt-independent non-electrostatic contacts reflect more specific binding interactions. Proteins with multiple cationic NA-binding domains connected by flexible linkers, such as the HIV-1 Gag polyprotein, may bind different NA molecules in distinct ways. For example, Gag binding to the Psi-packaging signal of the HIV-1 RNA genome optimizes the specific non-electrostatic binding component of this protein-RNA interaction. In contrast, Gag binding to a non-psi RNA optimizes the electrostatic interactions at the expense of specific contacts. Here, we describe a fluorescence anisotropy-based salt-titration approach that allows complete characterization of both electrostatic and non-electrostatic binding components for any protein-NA complex in a quantitative manner within a single assay. PMID:25579598

Rye-McCurdy, Tiffiny; Rouzina, Ioulia; Musier-Forsyth, Karin

2015-01-01

315

Cation binding by bacteriorhodopsin  

SciTech Connect

It was found that extensively washed purple membrane has about 1 calcium and 3-4 magnesium ions bound per bacteriorhodopsin molecule. When these divalent cations are removed by any of a variety of means, the pigment changes its color from purple to blue (lambda/sub max/ approx. = 600 nm). This blue pigment, which can be formed at near neutral pH, is probably very similar to blue species formed when the pH of a purple membrane sample is lowered to approx. = 2. When any of a wide variety of cations are added to a blue membrane preparation, the characteristic purple color of bacteriorhodopsin returns. Divalent and trivalent cations are much more efficient than monovalent cations in restoring the purple color and are effective at a ratio approaching one cation per pigment molecule. Besides shifting the absorption spectrum, removal of the divalent cations drastically alters the photochemical cycle of bacteriorhodopsin, including abolishing the unprotonated Schiff base (M-type) intermediate. Finally, lanthanum not only displaces the divalent cations normally bound to the purple membrane but also greatly reduces both the rate of decay of the M412 intermediate and proton uptake.

Chang, C.H.; Chen, J.G.; Govindjee, R.; Ebrey, T.

1984-01-01

316

The cyclopropyl cation  

E-print Network

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

Hampton, Loyd Ernest

1969-01-01

317

Determination of liposome partitioning of ionizable drugs by titration.  

PubMed

Drug partitioning to liposomes has been suggested as a model for partitioning to biomembranes but has been lacking a rapid analytical assay useful for drug screening. A fast pH-metric titration method for the determination of liposome partitioning of ionizable drugs using small unilamellar phosphatidylcholine vesicles prepared by sonic homogenization has been successfully developed, enabling the use of high lipid-to-drug ratios. Liposome-water partition coefficients of diclofenac and propranolol were determined to study the impact of varying titration parameters, temperature, equilibration time, lipid, and liposome types on the partitioning. To validate this method, the results were compared to literature values generated with different techniques and to pH-metric titration results with large unilamellar vesicles. The rapid pH-metric assay gave liposome partitioning data for the two model compounds which were consistent with other analytical techniques and liposome types. PMID:10430546

Balon, K; Riebesehl, B U; Müller, B W

1999-08-01

318

Calcium adsorption at the rutile-water interface: A potentiometric study in NaCl media to 250 C  

SciTech Connect

Calcium adsorption by rutile was studied potentiometrically from 25 to 250 C, at ionic strengths of 0.03 and 0.30 m in NaCl media, using two complementary experimental methodologies. In the first, net proton adsorption in the presence and absence of Ca{sup 2+} was monitored, and in the second, samples were periodically withdrawn during the course of a titration to determine Ca{sup 2+} adsorption directly. These experiments revealed that Ca{sup 2+} adsorption systematically increased with temperature relative to the pH of zero net proton charge in NaCl media alone (pH{sub znpc(NaCl)} - pH). That is, as temperature increased, Ca{sup 2+} adsorption commenced at progressively more positive pH{sub znpc(NaCl)} - pH values. Increasing ionic strength from 0.03 to 0.30 m NaCl suppressed Ca{sup 2+} adsorption at all temperatures as a result of either increased competition from Na{sup +} or greater complexation of Ca{sup 2+} by Cl{sup {minus}}. Finally, there was no apparent trend in the proton stoichiometric ratios (moles H{sup +} released/moles Ca{sup 2+} adsorbed) with increasing temperature. This suggests that the electrostatic and/or chemical processes involved in Ca{sup 2+} adsorption do not change greatly with increasing temperature. Favorable entropic effects, related to the increasing ease of releasing Ca{sup 2+} waters of hydration, are believed to be primarily responsible for the increase in adsorption with temperature.

Ridley, M.K.; Machesky, M.L.; Wesolowski, D.J.; Palmer, D.A.

1999-10-01

319

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

320

Constant-Current Coulometric Titration of Hydrochloric Acid  

NASA Astrophysics Data System (ADS)

The titration of a strong acid with a strong base and the electrolysis of water are two classic laboratory exercises that are either performed or demonstrated in secondary school classrooms in order to introduce two important areas of chemsitry: acid-base chemistry and electrochemistry. In this experiment we have combined these two classical experiments into one complete laboratory experience. Here we report how the elctrolysis of an aqueous solution can be used to determine the concentration of hydrochloric acid in a coulometric titration.

Swim, James; Earps, Edward; Reed, Laura M.; Paul, David

1996-07-01

321

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

PubMed

In this study, macroscopic and spectroscopic data were combined to develop a surface complexation model that describes the acid-base properties of Bacillus subtilis. The bacteria were freeze-dried and then resuspended in 0.1 M NaCl ionic medium. Macroscopic measurements included potentiometric acid-base titrations and electrophoretic mobility measurements. In addition, ATR-FTIR spectra of wet pastes from suspensions of Bacillus subtilis at different pH values were collected. The least-squares program MAGPIE was used to generate a surface complexation model that takes into account the presence of three acid-base sites on the surface: tripple bond COOH, tripple bond NH+, and tripple bond PO-, which were identified previously by XPS measurements. Both potentiometric titration data and ATR-FTIR spectra were used quantitatively, and electrostatic effects at the charged bacterial surface were accounted for using the constant capacitance model. The model was calculated using two different approaches: in the first one XPS data were used to constrain the ratio of the total concentrations of all three surface sites. The capacitance of the double layer, the total buffer capacity, and the deprotonation constants of the tripple bond NH+, tripple bond POH, and tripple bond COOH species were determined in the fit. A second approach is presented in which the ratio determined by XPS of the total concentrations of tripple bond NH+ to tripple bond PO- sites is relaxed. The total concentration of tripple bond PO- sites was determined in the fit, while the deprotonation constant for tripple bond POH was manually varied until the minimization led to a model which predicted an isoelectric point that resulted in consistency with electrophoretic mobility data. The model explains well the buffering capacity of Bacillus subtilis suspensions in a wide pH range (between pH=3 and pH=9) which is of considerable environmental interest. In particular, a similar quantitative use of the IR data opens up possibilities to model other bacterial surfaces at the laboratory scale and help estimate the buffering capacity of carboxylate-containing compounds in natural samples. PMID:17948795

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

2007-09-15

322

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.; Dixon, Joann F.

2009-01-01

323

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.; Dixon, Joann F.

2007-01-01

324

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.; Dixon, Joann F.

2008-01-01

325

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.

2006-01-01

326

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.

327

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

E-print Network

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

Russell, William Kent

1996-01-01

328

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

329

Investigation of the interaction between sodium dodecyl sulfate and cationic polymers.  

PubMed

Aggregation properties of sodium dodecyl sulfate (SDS) on a cationic hydroxyethyl cellulose, Polyquaternium-10 (PQ-10), of low charge density were studied by potentiometric and pyrene fluorescence methods and compared with those of poly(diallyldimethylammomium chloride) (PDADMAC) of high charge density. The critical aggregation concentration (cac) was measured with the potentiometric method and further confirmed with the fluorescence method. The former was found to be more accurate. The value of the cac for the SDS/PQ-10 system was measured at 100, 200, and 400 ppm polymer and at 288.2,298.2, and 308.2 K. They showed almost the same cac value, 0.04 mmol dm-3. The I1/I3 value of the pyrene fluorescence spectrum in the SDS/PQ-10 system at higher SDS concentration was smaller than that in SDS/PDADMAC solution and much larger than that of water. From the binding isotherm by the potentiometric method, the free DS- concentration (Cf) and the bound DS- concentration (Cb) could be evaluated with ease over the SDS concentration range above the cac. The aggregation number of DS- aggregates for both the above polymers was evaluated from the fluorescence quenching method using the values of Cf and Cb from the potentiometric method. Because Cf in the SDS/PQ-10 system above the cac did not maintain a constant value contrary to that in the SDS/PDADMAC system but increased quite a lot, Cb should not be regarded as [SDS] - cac above the cac. The aggregation number in the SDS/PQ-10 system increased almost linearly with increasing total concentration of SDS, while that in the SDS/PDADMAC system reached a plateau. With increasing temperature, the aggregation number of the SDS/PDADMAC system decreased more rapidly than that of the SDS/PQ-10 system. PMID:15969141

Lee, Jungno; Moroi, Yoshikiyo

2004-05-25

330

LABORATORY EXPERIMENT 3 Alkalimetric Titration of an Acid  

E-print Network

LABORATORY EXPERIMENT 3 Alkalimetric Titration of an Acid A carbonate-free sodium hydroxide goal is to prepare a carbonate-free sodium hydroxide solution and standardize it. Sodium hydroxide solution is prepared and standardized. Preparation and standardization of sodium hydroxide solution. Our

Nazarenko, Alexander

331

Titrating-Delay Matching-to-Sample in the Pigeon  

ERIC Educational Resources Information Center

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

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

2010-01-01

332

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

333

Determination of Acidity Constants by Gradient Flow-Injection Titration  

ERIC Educational Resources Information Center

A three-hour laboratory experiment, designed for an advanced undergraduate course in instrumental analysis that illustrates the application of the gradient chamber flow-injection titration (GCFIT) method with spectrophotometric detection to determine acidity constants is presented. The procedure involves the use of an acid-base indicator to obtain…

Conceicao, Antonio C. L.; Minas da Piedade, Manuel E.

2006-01-01

334

Acid Base Titrations in Nonaqueous Solvents and Solvent Mixtures  

Microsoft Academic Search

The acid base determination of different substances by nonaqueous titrations is highly preferred in pharmaceutical analyses since the method is quantitative, exact, and reproducible. The modern interpretation of the reactions in nonaqueous solvents started in the last century, but several inconsistencies and unsolved problems can be found in the literature. The acid base theories of Brønsted Lowry and Lewis as

Lajos Barcza; Ágnes Buvári-Barcza

2003-01-01

335

Titration of Isolated Cell Walls of Lemna minor L.  

PubMed

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

Morvan, C; Demarty, M; Thellier, M

1979-06-01

336

Direct measurement of protein binding energetics by isothermal titration calorimetry  

Microsoft Academic Search

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

Stephanie Leavitt; Ernesto Freire

2001-01-01

337

Using Spreadsheets to Produce Acid-Base Titration Curves.  

ERIC Educational Resources Information Center

Describes two spreadsheets for producing acid-base titration curves, one uses relatively simple cell formulae that can be written into the spreadsheet by inexperienced students and the second uses more complex formulae that are best written by the teacher. (JRH)

Cawley, Martin James; Parkinson, John

1995-01-01

338

The ion-sensitive field effect transistor in rapid acid-base titrations  

Microsoft Academic Search

Ion-sensitive field effect transistors (ISFETs) are used as the pH sensor in rapid acid—base titrations. Titration speeds at least five times greater than those with glass electrodes are possible for accuracies better than ±1%.

M. Bos; P. Bergveld; Veen-Blaauw van A. M. W

1979-01-01

339

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.; Dixon, Joann F.

2007-01-01

340

Potentiometric determination of percent porosity in nickel electroplates on uranium metal  

SciTech Connect

A potentiometric procedure has been developed to determine the percent porosity of nickel electroplates on uranium metal. In this case, percent porosity is defined as the ratio of the exposed uranium surface to the nickel electroplate surface times 100. Basically, this procedure exploits the high chemical reactivity between uranium metal and chloride ions in aqueous solution. It involves the potentiometric measurement of the corrosion potentials of coupled uranium/nickel metal electrodes in 0.01 molar potassium chloride solution versus a double-junctioned calomel electrode. A mathematical treatment of observed potentiometric measurements from a two-point calibration technique permits a best-fit calibration for a particular porosity determination on the same nickel-plated sample.

Dietrich, W.C.; Johnson, E.E.

1982-01-01

341

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

342

Potentiometric surface of the Brightseat-upper Potomac Aquifer in Virginia 1993  

USGS Publications Warehouse

Ground-water level measurements from 30 wells in the Brightseat-upper Potomac aquifer in the Coastal Plain Physiographic Province of Virginia in 1993 were used to prepare a map of the potentiometric surface of the aquifer. The map shows the potentiometric surface of the Brightseat-upper Potomac aquifer indicating a regional trend toward the Chesapeake Bay and Atlantic Ocean. The potentiometric-surface data indicate that cones of depression are apparent around West Point and in southeastern Isle of Wight County near Franklin, Virginia. The highest ground-water-level measurement was 4 feet above sea level in northern Accomack County, and the lowest ground-water-level measure- ment was 117 feet below sea level in Franklin, Virginia.

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

1994-01-01

343

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

NASA Astrophysics Data System (ADS)

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

Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

2013-11-01

344

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

345

Aluminum speciation and equilibria in aqueous solution: III. Potentiometric determination of the first hydrolysis constant of aluminum(III) in sodium chloride solutions to 125°C  

NASA Astrophysics Data System (ADS)

The first molal hydrolysis quotient of aluminum(III) was measured potentiometrically from 25 to 125°C at 25° intervals at ionic strengths of 0.1, 0.3, 1.0 and 5 mol · kg -1 with sodium chloride as the supporting electrolyte. The experimental method involved using a hydrogen-electrode concentration cell modified to compensate for any intrinsic potential offset between the two electrodes. The initial concentration of Al 3+ was varied to test for the presence of multinuclear aluminum species while being kept to a maximum of 10 -3 mol · kg -1 to minimize their occurrence. Similarly, the maximum degree of hydrolysis of Al 3+ reached in each titration was ca. 30%, after which polymerization and/or precipitation became apparent. The equilibrium quotients obtained in this study and selected values from the literature were fitted by an empirical equation incorporating a linear dependence of log K1,1 on the reciprocal temperature (Kelvins) over the range 10-200°C and three ionic-strength-dependent parameters. Comparisons are made between the results of this study and the literature values.

Palmer, Donald A.; Wesolowski, David J.

1993-07-01

346

Hydroxy-thioxanthones as suitable neutral ionophores for the preparation of PVC-membrane potentiometric sensors for Al(III) ion.  

PubMed

The complexation of five recently synthesized hydroxy-thioxanthone derivatives with Al3+ ion was studied in a methanol solution spectrophotometrically, and the stepwise formation constants of the resulting 1:1 and 2:1 (ligand-to-metal) complexes were evaluated. The suitability of the thioxanthone derivatives as neutral ionophores for the preparation of a new Al3+ ion-selective PVC-membrane electrode was investigated, and 1-hydroxy-3-methyl-thiocanthone was selected as the best compound for this purpose. The prepared electrode exhibits a Nernstian response for Al3+ ions over a wide concentration range (2.0 x 10(-2) to 2.0 x 10(-6) M), with a limit of detection of 1.0 x 10(-6) M. It has a very fast response time of about 5 s and can be used for at least 3 months without any considerable divergence in the potentials. The proposed membrane sensor revealed very good selectivities for Al3+ over a wide variety of other metal ions, and could be used at a working pH range of 3.4 - 5.0. It was used as an indicator electrode in potentiometric titration of aluminum ions with EDTA, and in the determination of Al3+ in different real samples. PMID:15055955

Shamsipur, Mojtaba; Ershad, Sohrab; Yari, Absollah; Sharghi, Hashem; Salimi, Ali Reza

2004-02-01

347

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

348

Scopolamine Effects Under a Titrating-Delayed-Nonmatching-to-Position Procedure  

ERIC Educational Resources Information Center

In a study of working memory, the performance of rats under titrating-delayed-nonmatching- to-position (TDNMTP) procedures was examined. Overall accuracy and the number of trials completed were inversely related to titration value, whereas the highest delay attained was directly related to titration value. When given intraperitoneally,…

Porritt, M.; Poling, A.

2008-01-01

349

The possibility of determining the activity coefficients of individual ions from acid-base titration data  

Microsoft Academic Search

A method is described for obtaining the activity coefficients of individual ions from experimental titration data. For this purpose, a general polyprotic acid-base-titration-curve equation is derived. The equation allows obtaining the dissociation equilibrium constants of the acid and the ratio of the activity coefficient of each ion to the activity coefficient of the undissociated acid directly from the titration data.

I. Jano; J. E. Hardcastle

1998-01-01

350

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

Microsoft Academic Search

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

Lorentz JÄNTSCHI; Horea Iustin

2002-01-01

351

SR-FTIR Study of Bacteria-Water Interactions: Acid-base Titration and Silification Experiments  

E-print Network

SR-FTIR Study of Bacteria-Water Interactions: Acid-base Titration and Silification Experiments/base titration and Si precipitation experiments. The objectives of this research are to identify the reactive through fluid cell with BaF2 and ZnSe windows separated by a 6 um mylar spacer. Acid-base titration and Si

352

Relations between Protonation Constants and Titration Curves in Polyprotic Acids: A Critical View  

E-print Network

Relations between Protonation Constants and Titration Curves in Polyprotic Acids: A Critical View G. In this paper, the relation between these pKa values and their relation to titration curves is discussed. Often inflection points of total and individual titration curves or the pH value where the proton binding site

Ullmann, G. Matthias

353

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.1 pseudoknot is the limiting step of the molecular mechanism. Last, as illustrated here, isothermal titration

Perreault, Jean-Pierre

354

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

E-print Network

Comparison 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 titration, whereas the so-called zeta potential is generally determined by electrokinetic techniques (e

Attard, Phil

355

Journal of Electroanalytical Chemistry 512 (2001) 8391 Faradaic impedance titration of pure 3-mercaptopropionic acid  

E-print Network

Journal of Electroanalytical Chemistry 512 (2001) 83­91 Faradaic impedance titration of pure 3-assembled monolayers (SAMs) have been studied using the faradaic impedance titration method. The Fe(CN)6 3- is used strength. The in-plane electrostatic force effect, which causes a broadening of the titration curves

Kwak, Juhyoun

356

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

E-print Network

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

Morel, François M. M.

357

NATURE BIOTECHNOLOGY VOLUME 24 NUMBER 9 SEPTEMBER 2006 1123 Using RNA sample titrations to assess  

E-print Network

NATURE BIOTECHNOLOGY VOLUME 24 NUMBER 9 SEPTEMBER 2006 1123 Using RNA sample titrations to assess assessed the utility of RNA titration samples for evaluating microarray platform performance and the impact samples and two titration mixtures of these samples. Focusing on 12,091 genes common across all platforms

Cai, Long

358

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'expression de l'activité par rapport à un système unitaire. Titration of immunogenic activity of anti-Bru- cella reference vaccine. We describe here prepara- tion and titration of this vaccine. Materials and Methods

Boyer, Edmond

359

Linking Surface Potential and Deprotonation in Nanoporous Silica: Second Harmonic Generation and Acid/Base Titration  

E-print Network

and Acid/Base Titration R. Kramer Campen,,,§ Allison K. Pymer,,| Satoshi Nihonyanagi,, and Eric Borguet development in nanoporous silica. We do so using conventional titration techniques and a noninvasive, all by internal surface sites. Such a threshold pH, above which acid/base or ion titration curves of porous

Borguet, Eric

360

Dissecting electrostatic interactions in Bacillus circulans xylanase through NMR-monitored pH titrations  

E-print Network

-monitored pH titrations Lawrence P. McIntosh · Daigo Naito · Simon J. Baturin · Mark Okon · Manish D. Joshi.V. 2011 Abstract NMR-monitored pH titration curves of proteins provide a rich source of structural to analyze the biphasic titrations exhibited by the side chain 13 Cc nuclei of the nucleophilic Glu78

McIntosh, Lawrence P.

361

On-Chip Titration of an Anticoagulant Argatroban and Determination of the Clotting Time within  

E-print Network

On-Chip Titration of an Anticoagulant Argatroban and Determination of the Clotting Time within was developed to titrate an anticoagulant (argatroban) into blood samples and to measure the clotting time using) titration of argatroban (0-1.5 µg/mL) into plugs and measurement of the resulting APTTs at room temperature

Ismagilov, Rustem F.

362

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

E-print Network

Polyelectrolyte Titration: Theory and Experiment Itamar Borukhov,*, David Andelman,,| Regis Borrega; In Final Form: July 31, 2000 Titration of methacrylic acid/ethyl acrylate copolymers is studied experimentally and theoretically. At low salt concentrations, this polyacid exhibits a plateau in the titration

Andelman, David

363

Titrating PolyelectrolytessVariational Calculations and Monte Carlo Simulations Bo Jo1nsson*, and Magnus Ullner  

E-print Network

Titrating PolyelectrolytessVariational Calculations and Monte Carlo Simulations Bo Jo1nsson Variational methods are used to calculate structural and thermodynamical properties of a titrating; i.e., titratable groups in a polymer will exchange protons with the solution and the polymer net

Peterson, Carsten

364

New Concepts A Novel View of pH Titration in Biomolecules  

E-print Network

New Concepts A Novel View of pH Titration in Biomolecules Alexey Onufriev, David A. Case,* and G 31, 2001 ABSTRACT: When individual titratable sites in a molecule interact with each other, their pH titration can be considerably more complex than that of an independent site described by the classical

Onufriev, Alexey

365

proteinsSTRUCTURE O FUNCTION O BIOINFORMATICS Titration_DB: Storage and analysis of  

E-print Network

proteinsSTRUCTURE O FUNCTION O BIOINFORMATICS Titration_DB: Storage and analysis of NMR-monitored protein pH titration curves Damien Farrell,1 Emanuel Sa´ Miranda,1 Helen Webb,1 Nikolaj Georgi,1 Peter B display pH-dependent properties due to titration of amino acid side chains and termini, coupled

McIntosh, Lawrence P.

366

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

E-print Network

1 Age adapted morphine titration produces equivalent analgesia and side effects in younger: To determine efficacy and safety of postoperative titrated morphine in elderly patients when intravenous complaining of pain received morphine until adequate pain relief. Intravenous morphine was titrated as 3 mg

Boyer, Edmond

367

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

E-print Network

Age-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 was titrated as 3 mg boluses for young (age 65 yrs) and 2 mg for elderly patients (> 65 yrs) respectively

Paris-Sud XI, Université de

368

Relations between Protonation Constants and Titration Curves in Polyprotic Acids: A Critical View  

E-print Network

Relations between Protonation Constants and Titration Curves in Polyprotic Acids: A Critical View G. B November 20, 2002 Supporting information 1 #12;1. Inflection Points of Titration Curves Monoprotic Acid. The titration curve of a monoprotic acid is given by eq 1 which is algebraically equivalent

Ullmann, G. Matthias

369

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

370

Potentiometric surface of the Floridan aquifer in the Northwest Florida Water Management District, May 1980  

USGS Publications Warehouse

A May 1980 potentiometric surface map of the Northwest Florida Water Management District depicts water levels in wells tapping the Floridan aquifer prior to summer pumpage. Compared to earlier potentiometric maps of the area, there are no significant differences in the 1980 map that are the result of hydrologic conditions. The addition of numerous new monitor wells in Jackson, Calhoun, Gadsden, and Liberty Counties, however, permitted refinement or better delineation of contours and a separation of water-bearing zones of the Floridan aquifer in the latter two counties. (USGS)

Rosenau, J.C.; Milner, R.S.

1981-01-01

371

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

PubMed Central

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

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

2011-01-01

372

New developments for the numerical analysis of spectrophotometric titrations  

Microsoft Academic Search

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

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

1999-01-01

373

A high frequency titration of indium with benzenephosphinic acid  

E-print Network

for iron. Banks, pennell, and gkoog (3) followed this with a publication of results obtained in determining what other ious would effect the iron determination by precipitation, or by coprecipitation, or by complex foramtion with benseaephosphinic acid... that there is no coprecipitation. The 25T, excess of the acid shows that essentially the precipitation of indium as indium benzene- pbosphinate is complete at a stoichiometric point. Benzenephosphinic acid should serve as a precipitating agent in a volumetric titration...

Keilt, Francis Xavier

1960-01-01

374

Lab on paper: iodometric titration on a printed card.  

PubMed

A paper test card has been engineered to perform an iodometric titration, an application that requires storage and mixing on demand of several mutually incompatible reagents. The titration is activated when a user applies a test solution to the test card: the dried reagents are reconstituted and combined through a surface-tension-enabled mixing (STEM) mechanism. The device quantifies 0.8-15 ppm of iodine atoms from iodate in aqueous solutions. This is useful, for example, to quantify iodine levels in fortified salt. A blinded internal laboratory validation established the accuracy as 1.4 ppm I and the precision as 0.9 ppm I when the test card was read by newly trained users. Using computer software to process images, the accuracy and precision both improved to 0.9 ppm I. The paper card can also detect substandard ? lactam antibiotics using an iodometric back-titration. When used to quantify amoxicillin, good distinction is achieved between solutions that differ by 0.15 mg/mL over a working range of 0-0.9 mg/mL. The test card was designed to meet the World Health Organization ASSURED criteria for use in low resource settings, where laboratory-based analytical procedures are often not available. PMID:25711696

Myers, Nicholas M; Kernisan, Emalee N; Lieberman, Marya

2015-04-01

375

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

376

Potentiometric measurement of polymer-membrane electrodes based on lanthanum  

NASA Astrophysics Data System (ADS)

Quantitative analysis of rare earth elements which are considered as the standard method that has a high accuracy, and detection limits achieved by the order of ppm is inductively coupled plasma atomic emission spectroscopy (ICPAES). But these tools are expensive and valuable analysis of the high cost of implementation. In this study be made and characterized selective electrode for the determination of rare earth ions is potentiometric. Membrane manufacturing techniques studied is based on immersion (liquid impregnated membrane) in PTFE 0.5 pore size. As ionophores to be used tri butyl phosphate (TBP) and bis(2-etylhexyl) hydrogen phosphate. There is no report previously that TBP used as ionophore in polymeric membrane based lanthanum. Some parameters that affect the performance of membrane electrode such as membrane composition, membrane thickness, and types of membrane materials studied in this research. Manufacturing of Ion Selective Electrodes (ISE) Lanthanum (La) by means of impregnation La membrane in TBP in kerosene solution has been done and showed performance for ISE-La. FTIR spectrum results for PTFE 0.5 pore size which impregnated in TBP and PTFE blank showed difference of spectra in the top 1257 cm-1, 1031 cm-1 and 794.7 cm-1 for P=O stretching and stretching POC from group -OP =O. The result showed shift wave number for P =O stretching of the cluster (-OP=O) in PTFE-TBP mixture that is at the peak of 1230 cm-1 indicated that no interaction bond between hydroxyl group of molecules with molecular clusters fosforil of TBP or R3P = O. The membrane had stable responses in pH range between 1 and 9. Good responses were obtained using 10-3 M La(III) internal solution, which produced relatively high potential. ISE-La showed relatively good performances. The electrode had a response time of 29±4.5 second and could be use for 50 days. The linear range was between 10-5 and 10-1 M.

Saefurohman, Asep; Buchari, Noviandri, Indra; Syoni

2014-03-01

377

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

PubMed

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

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

2014-04-10

378

Chain stiffness, salt valency, and concentration influences on titration curves of polyelectrolytes: Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Monte Carlo simulations have been used to study two different models of a weak linear polyelectrolyte surrounded by explicit counterions and salt particles: (i) a rigid rod and (ii) a flexible chain. We focused on the influence of the pH, chain stiffness, salt concentration, and valency on the polyelectrolyte titration process and conformational properties. It is shown that chain acid-base properties and conformational properties are strongly modified when multivalent salt concentration variation ranges below the charge equivalence. Increasing chain stiffness allows to minimize intramolecular electrostatic monomer interactions hence improving the deprotonation process. The presence of di and trivalent salt cations clearly promotes the chain degree of ionization but has only a limited effect at very low salt concentration ranges. Moreover, folded structures of fully charged chains are only observed when multivalent salt at a concentration equal or above charge equivalence is considered. Long-range electrostatic potential is found to influence the distribution of charges along and around the polyelectrolyte backbones hence resulting in a higher degree of ionization and a lower attraction of counterions and salt particles at the chain extremities.

Carnal, Fabrice; Stoll, Serge

2011-01-01

379

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

380

BIOSENSOR FOR DIRECT DETERMINATION OF ORGANOPHOSPHATE NERVE AGENTS. 1. POTENTIOMETRIC ENZYME ELECTRODE. (R823663)  

EPA Science Inventory

A potentiometric enzyme electrode for the direct measurement of organophosphate (OP) nerve agents was developed. The basic element of this enzyme electrode was a pH electrode modified with an immobilized organophosphorus hydrolase (OPH) layer formed by cross-linking OPH ...

381

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.; Sýkora, D.; Sessler, J.L.; Král, V.

2007-01-01

382

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

E-print Network

in mixed potential NOx and CO sensors [5]. The output voltage of these sensors is determined by the mixedSensors and Actuators B 113 (2006) 162­168 Dependence of potentiometric oxygen sensing for Industrial Sensors and Measurements (CISM), Department of Materials Science and Engineering, 2041 College

Dutta, Prabir K.

2006-01-01

383

Vanadyl(IV) Complexes of Lactobionic Acid: Potentiometric and Spectroscopic Studies  

Microsoft Academic Search

Potentiometric and spectroscopic studies have shown that in the VO(IV)-lactobionic acid system five different species are involved in coordination equilibria. All complexes consist of one metal ion and two ligand molecules. Stability constants for the vanadyl complexes with lactobionic acid are considerably higher than those for uronic acids, although the donor atoms involved in metal ion coordination are exactly the

Henryk Kozlowski; Saad Bouhsina; Patrick Decock; Giovanni Micera; Jolanta Swiatek

1991-01-01

384

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

385

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

PubMed

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

Yim, H S; Meyerhoff, M E

1992-09-01

386

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

PubMed

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 (pK(B1)) and 3.3-3.8 (pK(B2)). 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; Sýkora, D; Sessler, J L; Král, V

2007-03-28

387

An electrochemical time-of-flight technique with galvanostatic generation and potentiometric sensing  

E-print Network

An electrochemical time-of-flight technique with galvanostatic generation and potentiometric simulated E vs t transients. Digital simulations were based on simple hemi-cylindrical diffusion between January 2003 Abstract A variation of an electrochemical time-of-flight (ETOF) technique is described

Majda, Marcin

388

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

389

Potentiometric pH Measurements of Acidity Are Approximations, Some More Useful than Others  

ERIC Educational Resources Information Center

A recent article by McCarty and Vitz "demonstrating that it is not true that pH = -log[H+]" is examined critically. Then, the focus shifts to underlying problems with the IUPAC definition of pH. It is shown how the potentiometric method can provide "estimates" of both the IUPAC-defined hydrogen activity "and" the hydrogen ion concentration, using…

de Levie, Robert

2010-01-01

390

The specific interaction between two C:C mismatch base pairs and silver (I) cation.  

PubMed

We have already found that a single silver (I) cation specifically binds to a single C:C mismatch base pair in heteroduplex, which increases the melting temperature of heteroduplex involving a single C:C mismatch base pair by about 4 degrees C. Here, to examine the thermodynamic properties involving two C:C mismatch base pairs, we analyzed the interaction between silver (I) cations and heteroduplex involving two C:C mismatch base pairs by isothermal titration calorimetry. The difference in the positions of the two C:C mismatch base pairs did not significantly affect the magnitudes of the stoichiometry and the thermodynamic parameters for the interaction between silver (I) cations and the two C:C mismatch base pairs. Two silver (I) cations bind with two C:C mismatch base pairs. The binding affinity for the second silver (I) cation was similar to that for the first silver (I) cation. Our results certainly support the idea that addition of the silver (I) cation is a promising strategy for the C:C mismatch base pair detection in the heteroduplex analysis and may eventually lead to progress in SNP genotyping. PMID:18029647

Torigoe, Hidetaka; Kozasa, Tetsuo; Ono, Akira

2007-01-01

391

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

USGS Publications Warehouse

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

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

1989-01-01

392

A titration model for evaluating calcium hydroxide removal techniques  

PubMed Central

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

PHILLIPS, Mark; McCLANAHAN, Scott; BOWLES, Walter

2015-01-01

393

PAPER www.rsc.org/pps | Photochemical & Photobiological Sciences Theoretical investigation of the behavior of titratable groups in proteins  

E-print Network

of the behavior of titratable groups in proteins Astrid R. Klingen,a Elisa Bombardaa,b and G. Matthias Ullmann April 2006 DOI: 10.1039/b515479k This paper presents a theoretical analysis of the titration behavior of strongly interacting titratable residues in proteins. Strongly interacting titratable residues exist

Ullmann, G. Matthias

394

High frequency titration of amines in nonaqueous solutions  

E-print Network

appeared to be more gradual than in the previous instances. Por this reason the high frequency end pbint was assumed to be the correct once Attempts were made to titrate both ortho- and ~ara-nitroaniline, but they were unsuccessful. This was apparently... were obtained, for n-propylamine, di-n-propylamine, triethylamine, ethanol- amine, and pyridine. Pair results were obt aimed for aniline and m-bromoaniline; however, ortho- and para- nitroaniline could not be titra*ed by this method. An attempt...

Witmer, William Byron

1958-01-01

395

Succinylated machined corncobs: Titration and heavy metal ion binding characteristics  

SciTech Connect

The use of inexpensive natural materials for waste water treatment is economically attractive. In this study chemical modifications of an agricultural by-product, Lite-R-Cobs, were explored to increase its utility for reduction of metal ions in waste water effluent. Corn cob particles have been succinylated to increase their capacity for binding heavy metal ions. The carboxyl groups introduced into this cellulosic material were quantitated by base titration. Equilibrium metal ion binding characteristics of the material was studied for Cu{sup 2+}, Cd{sup 2+}, and Ni{sup 2+} ions.

McCall, R.C.; Getman, T.D.; Hunsley, J.R. [Southern Illinois Univ., Edwardsville, IL (United States)

1996-10-01

396

Isothermal Titration Calorimetry of Membrane Proteins – Progress and Challenges  

PubMed Central

Summary Integral membrane proteins, including G protein-coupled receptors (GPCR) and ion channels, mediate diverse biological functions that are crucial to all aspects of life. The knowledge of the molecular mechanisms, and in particular, the thermodynamic basis of the binding interactions of the extracellular ligands and intracellular effector proteins is essential to understand the workings of these remarkable nanomachines. In this review, we describe how isothermal titration calorimetry (ITC) can be effectively used to gain valuable insights into the thermodynamic signatures (enthalpy, entropy, affinity, and stoichiometry), which would be most useful for drug discovery studies, considering that more than 30% of the current drugs target membrane proteins. PMID:23747362

Rajarathnam, Krishna; Rösgen, Jörg

2013-01-01

397

A Dibasic Acid Titration for the Physical Chemistry Laboratory  

NASA Astrophysics Data System (ADS)

A physical chemistry laboratory experiment is described in which both pK, and pK2 are determined for weak dibasic acids with closely spaced acid dissociation constants. The method is acid-base titration. Data are acquired by a computer interfaced to a pH meter, however emphasis on experimental technique is retained by requiring students to manipulate a buret, read it, and manually enter the volumes into the computer. The computer is then used to ease the burden of tedious and repetitious calculations which yield the two pKa values.

Brabson, G. D.; Clay, J. T.; Walters, E. A.

1995-07-01

398

Applications of Isothermal Titration Calorimetry in RNA Biochemistry and Biophysics  

PubMed Central

Isothermal titration calorimetry (ITC) has been applied to the study of proteins for many years. Its use in the biophysical analysis of RNAs has lagged significantly behind its use in protein biochemistry, however, in part because of the relatively large samples required. As the instrumentation has become more sensitive, the ability to obtain high quality data on RNA folding and RNA ligand interactions has improved dramatically. This review provides an overview of the ITC experiment and describes recent work on RNA systems that have taken advantage of its versatility for the study of small molecule binding, protein binding, and the analysis of RNA folding. PMID:17671974

Feig, Andrew L.

2008-01-01

399

Determination of penicillins by desulphurization with lead and edta titration.  

PubMed

A new, simple, accurate and rapid method is described for the determination of total penicillins in pharmaceutical preparations. The method is based on desulphurization with potassium plumbite whereby one mole of lead sulphide is formed per mole of penicillin. The excess of lead ions is titrated with EDTA at pH 4.5, with use of the lead ion-selective electrode. Results are reproducible within +/- 0.5% and compare favourably with those obtained by the procedures of the United States and British Pharmacopoeias. PMID:18962387

Hassan, S S; Zaki, M T; Eldesouki, M H

1979-02-01

400

Analysis of chromite by cation-exchange using ethylenediaminetetra-acetic acid.  

PubMed

A method for the separation and determination of five major elements in chromite ore (and chrome-bearing refractories), based on complexation of the metals with EDTA is described. After removal of silica, the cations are separated into two groups by passing the solution through a cation-exchange resin (Dowex 50W-X8, in Na-form) in the presence of an excess of the complexing agent. The optimum conditions for the separation are discussed on the basis of exchange constants that were either known or determined. The first group contains Cr and Fe, which emerge in the filtrate at pH between 1.5 and 2.1, whereas A1, Mg and Ca, which are adsorbed on the resin, form another group. Complexometric titrations are used for the subsequent determination of the cations in each group. The method is simpler and more rapid and accurate for routine analysis than the current methods. PMID:18961783

Jawaid, M; Ingman, F

1975-12-01

401

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

402

Constant-pH molecular dynamics using stochastic titration  

NASA Astrophysics Data System (ADS)

A new method is proposed for performing constant-pH molecular dynamics (MD) simulations, that is, MD simulations where pH is one of the external thermodynamic parameters, like the temperature or the pressure. The protonation state of each titrable site in the solute is allowed to change during a molecular mechanics (MM) MD simulation, the new states being obtained from a combination of continuum electrostatics (CE) calculations and Monte Carlo (MC) simulation of protonation equilibrium. The coupling between the MM/MD and CE/MC algorithms is done in a way that ensures a proper Markov chain, sampling from the intended semigrand canonical distribution. This stochastic titration method is applied to succinic acid, aimed at illustrating the method and examining the choice of its adjustable parameters. The complete titration of succinic acid, using constant-pH MD simulations at different pH values, gives a clear picture of the coupling between the trans/gauche isomerization and the protonation process, making it possible to reconcile some apparently contradictory results of previous studies. The present constant-pH MD method is shown to require a moderate increase of computational cost when compared to the usual MD method.

Baptista, António M.; Teixeira, Vitor H.; Soares, Cláudio M.

2002-09-01

403

Organic cation transporters.  

PubMed

1. Organic cation transporters (OCTs) translocate endogenous (e.g. dopamine) and exogenous (e.g. drugs) substances of cationic nature and, therefore, play an important role in the detoxification of exogenous compounds. This review aims to furnish essential information on OCTs, with an emphasis on pharmacological aspects. 2. Analysis of the literature on OCTs makes clear that there is a species- and organ-specific distribution of the different isoforms, which can also be differentially regulated. OCTs are responsible for the excretion and/or distribution of many drugs and also for serious tissue-specific side-effects such as cisplatin-induced nephrotoxicity. The presence of single nucleotide polymorphisms in these transporters significantly influences the response of patients to medication, as demonstrated for the antidiabetic drug metformin. 3. A substantial amount of research has to be undertaken to clarify further the OCT structure-function relationships specifically to define the role of oligomerization on their activity and regulation, to identify intracellular interaction partners of OCTs, and to characterize their pharmacogenetic aspects. PMID:18668435

Ciarimboli, G

2008-07-01

404

Potentiometric Multisensor Based on Ruthenium Dioxide Thin Film With a Bluetooth Wireless and Web-Based Remote Measurement System  

Microsoft Academic Search

This study reports the preparation and analysis of a potentiometric multisensor for detecting pH, uric acid, and glucose levels. The pH sensor was based on a ruthenium dioxide (RuO2) sensing membrane. The potentiometric uric acid and glucose biosensors consisted of immobilized uricase and glucose oxidase (GOD) enzymes on the RuO2 sensing membrane. The ruthenium dioxide sensing membrane was first deposited

Yi-Hung Liao; Jung-Chuan Chou

2009-01-01

405

Potentiometric surface of the Floridan aquifer in the Suwannee River Water Management District, north Florida, May 1980  

USGS Publications Warehouse

A May 1980 potentiometric surface map of the Suwannee River Water Management District area, Florida, depicts water levels in wells tapping the Floridan aquifer. Compared to the May 1976 potentiometric map of the area, there are no significant differences in the general appearance of the contours. Water levels, however, are generally about 10 feet higher than in 1976 along the Suwannee River and for some 20 miles west of the river and in Gilchrist and Levy Counties to the east. (USGS)

Rosenau, J.C.; Milner, R.S.

1981-01-01

406

The adsorption of cationic and amphoteric copolymers on glass surfaces: zeta potential measurements, adsorption isotherm determination, and FT Raman characterization.  

PubMed

The adsorption of cationic and amphoteric copolymers onto controlled pore glass (CPG) powders has been studied by measurement of the powder particle zeta (zeta) potential, by determination of the adsorption isotherm, and by FT Raman measurements of the polymer-coated powder. The cationic polymers consisted chiefly of homopolymers of dimethyldiallylammonium chloride (DMDAAC) or copolymers of DMDAAC and acrylamide. The amphoteric polymers studied included copolymers of DMDAAC and acrylic acid. The comonomer ratio was varied to explore the dependence of cationic charge density on the extent and effect of adsorption. Both types of polymers adsorb onto the anionic glass surface via an ion-exchange mechanism. Consequently, a correspondingly higher mass of a low-charge-density copolymer adsorbs than of a cationic homopolymer. The presence of the anionic portion in the amphoteric polymers does not significantly alter this picture. The zeta potential, however, reflects the overall nature of the polymer. Cationic polymers effectively neutralize the glass surface, while amphoteric polymers leave the zeta potential net negative. Adsorption isotherms, determined via the depletion technique using colloidal titration, were used to "calibrate" a FT Raman method. The latter was used to determined the amount of adsorbed polymer under solution conditions in which colloidal titration could not be performed. PMID:12909030

Tartakovsky, Alla; Drutis, Dane M; Carnali, Joseph O

2003-07-15

407

Geostatistical analysis of potentiometric data in the Pennsylvanian aquifer of the Palo Duro Basin, Texas  

SciTech Connect

This report details a geostatistical analysis of potentiometric data from the Pennsylvanian aquifer in the Palo Duro Basin, Texas. Such an analysis is a part of an overall uncertainty analysis for a high-level waste repository in salt. Both an expected potentiometric surface and the associated standard error surface are produced. The Pennsylvanian data are found to be well explained by a linear trend with a superimposed spherical semivariogram. A cross-validation of the analysis confirms this. In addition, the cross-validation provides a point-by-point check to test for possible anomalous data. The analysis is restricted to that portion of the Pennsylvanian aquifer that lies to the southwest of the Amarillo Uplift. The Pennsylvanian is absent is some areas across the uplift and data to the northeast were not used in this analysis. The surfaces produced in that analysis are included for comparison. 9 refs., 15 figs.

Harper, W.V.; Basinger, K.L.; Furr, J.M.

1988-01-01

408

Nano- and microsized zeolites as a perspective material for potentiometric biosensors creation.  

PubMed

A number of potentiometric biosensors based on coimmobilization of enzymes with different types of zeolite on pH-ion-sensitive field-effect transistor (ISFET) have been developed. Their working characteristics have been determined and compared. It was shown that clinoptilolite and zeolite Beta polymorph A (BEA) are more promising for creating biosensors than zeolite A. Changing the concentration of zeolite BEA in membranes, it is possible to extend the biosensor linear measurement range. The two-layer method of deposition of the enzyme with clinoptilolite was found to provide a significant increase in the biosensor sensitivity to substrates, whereas thermal modification of the zeolite BEA crystals can improve analytical characteristics of potentiometric biosensors for detection of toxic substances. These results show that it is possible to regulate the ISFET characteristics for different enzyme-based biosensors by tailoring the electrode surfaces via different zeolites. This makes zeolites strong candidates for integration into biosensors as ISFET modifiers. PMID:25852356

Soldatkin, Oleksandr O; Shelyakina, Margaryta K; Arkhypova, Valentyna N; Soy, Esin; Kirdeciler, Salih Kaan; Ozansoy Kasap, Berna; Lagarde, Florence; Jaffrezic-Renault, Nicole; Akata Kurç, Burcu; Soldatkin, Alexei P; Dzyadevych, Sergei V

2015-01-01

409

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

PubMed

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

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

2003-09-01

410

Development of a potentiometric catechol biosensor by entrapment of tyrosinase within polypyrrole film  

Microsoft Academic Search

A method is described for the construction of a potentiometric catechol biosensor by entrapment of tyrosinase (polyphenol oxidase; PPO) into a conducting polypyrrole film on a platinum electrode. The optimum conditions for the formation of the PPy–Tyr (polypyrrole–tyrosinase) film include a current density of 0.5mAcm?2, a polymerization period of 150s, 0.1M pyrrole and 50UmL?1 tyrosinase. The presence of tyrosinase in

Qaisar Ameer; Samuel B. Adeloju

2009-01-01

411

Rapid determination of fluoride in potable waters by potentiometric flow injection analysis  

SciTech Connect

A potentiometric flow injection analysis system is described, enabling tap water and other fluoride-bearing matrices of low interferent level to be determined at the rate of 360 samples per hour using an electrode polished with slurried alumina. Important parameters, such as carrier stream composition, sample volume and detector cell design are discussed with respect to their system. Fluoride electrodes regenerated with silver fluoride and silver epoxy are evaluated in flow injection mode, both before and after polishing.

Davey, D.E.; Mulcahy, D.E.; O'Connell, G.R.

1986-01-01

412

Sensing properties and selectivities of a WO 3\\/YSZ\\/Pt potentiometric NO x sensor  

Microsoft Academic Search

Sensing properties of a WO3-based potentiometric NOx sensor were investigated in both N2 and simulated exhaust gas. A positive voltage response was obtained for NO2 but negative for NO at 650°C with the n-type semiconducting WO3-based sensor. The sensor was able to selectively detect NO in the presence of CO2 in 3% O2 and at 650°C. The NO sensitivity, however,

Jiho Yoo; Suman Chatterjee; Eric D. Wachsman

2007-01-01

413

Mathematical modelling of YSZ-based potentiometric gas sensors with oxide sensing electrodes  

Microsoft Academic Search

An analysis of transport phenomena through thin-film electrodes for a potentiometric nitrogen oxide (NOx) sensor based on yttria-stabilized zirconia (YSZ) is presented with a focus on the modelling and assessment of non-isothermal and non-isobaric effects (Soret effect) that have not been taken into analysis in previous studies. A mathematical model is formulated for a thin-film planar ZrO2 sensor with Pt

Serge Zhuiykov

2006-01-01

414

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

415

Formation and stability of nucleotide complexes: Raman titration investigation  

NASA Astrophysics Data System (ADS)

In order to monitor the formation of complexes between modified and wild type nucleotides, a concept based on spectroscopic titration combined with factor analysis data treatment has been developed. A set of samples containing two homopolynucleotides with complementary bases at various concentration ratios has been prepared. Other conditions, i.e. total nucleotide concentration, temperature, ionic strength, divalent ions percentage and pH, were conserved. The series of Raman and UV-absorption spectra obtained from these samples have been treated by factor analysis and the results then fitted to the equilibrium equations of 1 : 1 and 1 : 2 complexes. By this way, spectra of individual unpaired nucleotides, 1 : 1 and 1 : 2 complexes, and values of the stability constants can be determined at the same time. While the former characterise the structure of the individual species, the latter parameters implicate their percentage in each sample. The approach has been tested on a poly(rA)-poly(rU) model system.

Hanuš, J.; Št?pánek, J.; Turpin, P.-Y.; Bok, J.

1999-05-01

416

Ultrasensitivity by molecular titration in spatially propagating enzymatic reactions.  

PubMed

Delineating design principles of biological systems by reconstitution of purified components offers a platform to gauge the influence of critical physicochemical parameters on minimal biological systems of reduced complexity. Here we unravel the effect of strong reversible inhibitors on the spatiotemporal propagation of enzymatic reactions in a confined environment in vitro. We use micropatterned, enzyme-laden agarose gels which are stamped on polyacrylamide films containing immobilized substrates and reversible inhibitors. Quantitative fluorescence imaging combined with detailed numerical simulations of the reaction-diffusion process reveal that a shallow gradient of enzyme is converted into a steep product gradient by addition of strong inhibitors, consistent with a mathematical model of molecular titration. The results confirm that ultrasensitive and threshold effects at the molecular level can convert a graded input signal to a steep spatial response at macroscopic length scales. PMID:23972857

Semenov, Sergey N; Markvoort, Albert J; Gevers, Wouter B L; Piruska, Aigars; de Greef, Tom F A; Huck, Wilhelm T S

2013-08-20

417

Isothermal titration calorimetry of ion-coupled membrane transporters.  

PubMed

Binding of ligands, ranging from proteins to ions, to membrane proteins is associated with absorption or release of heat that can be detected by isothermal titration calorimetry (ITC). Such measurements not only provide binding affinities but also afford direct access to thermodynamic parameters of binding - enthalpy, entropy and heat capacity. These parameters can be interpreted in a structural context, allow discrimination between different binding mechanisms and guide drug design. In this review, we introduce advantages and limitations of ITC as a methodology to study molecular interactions of membrane proteins. We further describe case studies where ITC was used to analyze thermodynamic linkage between ions and substrates in ion-coupled transporters. Similar type of linkage analysis will likely be applicable to a wide range of transporters, channels, and receptors. PMID:25676707

Boudker, Olga; Oh, SeCheol

2015-04-01

418

Neurons limit angiogenesis by titrating VEGF in retina.  

PubMed

Vascular and nervous systems, two major networks in mammalian bodies, show a high degree of anatomical parallelism and functional crosstalk. During development, neurons guide and attract blood vessels, and consequently this parallelism is established. Here, we identified a noncanonical neurovascular interaction in eye development and disease. VEGFR2, a critical endothelial receptor for VEGF, was more abundantly expressed in retinal neurons than in endothelial cells, including endothelial tip cells. Genetic deletion of VEGFR2 in neurons caused misdirected angiogenesis toward neurons, resulting in abnormally increased vascular density around neurons. Further genetic experiments revealed that this misdirected angiogenesis was attributable to an excessive amount of VEGF protein around neurons caused by insufficient engulfment of VEGF by VEGFR2-deficient neurons. Moreover, absence of neuronal VEGFR2 caused misdirected regenerative angiogenesis in ischemic retinopathy. Thus, this study revealed neurovascular crosstalk and unprecedented cellular regulation of VEGF: retinal neurons titrate VEGF to limit neuronal vascularization. PAPERFLICK: PMID:25417109

Okabe, Keisuke; Kobayashi, Sakiko; Yamada, Toru; Kurihara, Toshihide; Tai-Nagara, Ikue; Miyamoto, Takeshi; Mukouyama, Yoh-suke; Sato, Thomas N; Suda, Toshio; Ema, Masatsugu; Kubota, Yoshiaki

2014-10-23

419

Ultrasensitivity by Molecular Titration in Spatially Propagating Enzymatic Reactions  

PubMed Central

Delineating design principles of biological systems by reconstitution of purified components offers a platform to gauge the influence of critical physicochemical parameters on minimal biological systems of reduced complexity. Here we unravel the effect of strong reversible inhibitors on the spatiotemporal propagation of enzymatic reactions in a confined environment in vitro. We use micropatterned, enzyme-laden agarose gels which are stamped on polyacrylamide films containing immobilized substrates and reversible inhibitors. Quantitative fluorescence imaging combined with detailed numerical simulations of the reaction-diffusion process reveal that a shallow gradient of enzyme is converted into a steep product gradient by addition of strong inhibitors, consistent with a mathematical model of molecular titration. The results confirm that ultrasensitive and threshold effects at the molecular level can convert a graded input signal to a steep spatial response at macroscopic length scales. PMID:23972857

Semenov, Sergey N.; Markvoort, Albert J.; Gevers, Wouter B.L.; Piruska, Aigars; de Greef, Tom F.A.; Huck, Wilhelm T.S.

2013-01-01

420

Determination of sulphate by pH titration.  

PubMed

A simple and inexpensive method has been developed for the determination of sulphate and other very weak bases and acids. It utilizes the partial protonation of the weak base or the partial dissociation of the weak acid, which has not been exploited for analytical purposes thus far. The procedure consists of three pH titrations: one with a test solution of known sulphate content, the second with the sulphate sample, and the third with a blank. This method can be used in the presence of several inorganic ions and organic matrices, including non-aqueous solvents. In aqueous medium sulphate contents above 10(-3)M can be determined. The use of solvent mixtures may increase the sensitivity of the method by two orders of magnitude. PMID:18964322

Noszál, B; Juhász, M

1987-04-01

421

Development and certification of an automated differential titration photocalorimeter  

NASA Astrophysics Data System (ADS)

An automated differential titration photocalorimeter (ADTPC) has been designed for investigating photoinduced processes. This instrument provides means to record thermal and spectral (absorbance) changes in a calorimetric cell. Metrological characteristics of the described ADTPC are detection limit, 0.001 J with a reproducibility of 0.0002 J or better; short-duration noise level, ±5 rel. units; long-duration noise level, ±29 rel. units. ADTPC has been certified against the heats of mixing of solvents and the heat of neutralization reaction between tris(hydroxymethyl)aminomethane and HCl. The photocalorimetric unit of the device has additionally been certified against the heat of photolysis of K3[Fe(C2O4)3] and the heat of isomerization of azobenzene in heptane. Within the claimed errors, the heats measured with ADTPC are in agreement with the values recommended for the above systems.

Gubarev, Yu. A.; Lebedeva, N. Sh.; V'yugin, A. I.; Golubev, S. N.

2015-04-01

422

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

NASA Astrophysics Data System (ADS)

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

Stefánsson, Andri; Bénézeth, Pascale; Schott, Jacques

2014-08-01

423

Potentiometric determination of trace amounts of aluminium utilizing polyvinyl chloride membrane and coated platinum sensors based on E-N'-(2-hydroxy-3-methoxybenzylidene) benzohydrazide.  

PubMed

This paper describes the construction and performance characteristics of novel polyvinyl chloride membrane (PME) and coated platinum (CPtE) aluminium (Al) ion selective electrodes based on E-N'-(2-hydroxy-3-methoxybenzylidene) benzohydrazide. The electrodes exhibited linear responses with near Nernstian slopes of 19.9 +/- 0.3 (PME) and 20.1 +/- 0.4 (CPtE) mV/decade of activity within the Al3+ ion concentration range of 3.0 x 10(-7) to 1.0 x 10(-2) M for the PME and 1.0 x 10(-7)-1.0 x 10(-2) M for the CPtE. These sensors were applicable in a pH range of 3.0 to 7.0. The LODs of the PME and CPtE were 1.7 x 10(-7) and 5.6 x 10(-8) M, respectively. They had a response time of less than 10 s and could be used practically for a period of at least 2 months without measurable divergence in results. The isothermal temperature coefficient of the PME was 1.12 x 10(-3) V/degrees C, and it can tolerate partially nonaqueous media up to 25%. The electrodes showed excellent selectivity towards Al3+ ions in the presence of a wide range of alkali, alkaline earth, and transition metals ions. They were successfully applied for the direct determination of Al3+ ions in tap water, aqueduct water, mineral water, and Al-Mg syrup and as indicator electrodes in potentiometric titration of Al ions with EDTA. PMID:23513978

Tajik, Somayeh; Taher, Mohammad Ali; Sheikhshoaie, Iran

2013-01-01

424

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

USGS Publications Warehouse

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

Kinnaman, Sandra L.; Dixon, Joann F.

2008-01-01

425

Attacking Class Certifi cation Motions  

Microsoft Academic Search

Two recent post-Tobacco II Court of Appeal cases suggest that such reliance cannot necessarily be presumed. Two Court of Appeal panels in Southern California affi rmed trial court orders denying class certifi cation, drawing a distinction between the standing requirements and the other requirements for class certifi cation. The Court of Appeal for the 2nd Appellate District issued a decision

Charles T. Munger; Gerald L. Salzman; David Houston

2009-01-01

426

Biotite surface chemistry as a function of aqueous fluid composition  

E-print Network

derived via zeta potential measurements and potentiometric titrations performed for 20 and 60 min in batch potentiometric titrations yielded a pH of immersion of 9.66 (S.D. 0.24). From batch potentiometric titrations we to phyllosilicates, we have performed a series of batch potentiometric titration experiments and electrokinetic

Benning, Liane G.

427

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

428

Acid–Base Titration: Analysis of Phosphoric Acid Anodizing Solutions. A Problem-Based Learning Approach  

Microsoft Academic Search

Phosphoric acid anodizing solutions are routinely titrated to monitor their concentrations; however, after successive anodizations of aluminum metal, increasing amounts of dissolved aluminum interfere with the neutralization titration. The true concentration of phosphoric acid is determined by a correction factor based on the concentration of the dissolved aluminum, which is determined industrially by flame atomic absorption spectrometry. The academic determination

Marina C. Koether; Charles R. Munafo

2002-01-01

429

Modeling and Graphic Presentation of Acid–Base Titration Curves. Presentation of an Alternative Method  

Microsoft Academic Search

Titration curves for the acid—base–titration of polyvalent acids and bases and their mixtures can be created in a simple way and presented graphically. The method, an alternative to the existing procedures, shall be presented here for discussion. With the described method it is possible in an easy manner and for didactic purposes to show how the boundary conditions, such as

Günter Heil; Horst Schäfer

2002-01-01

430

A knowledge based advisory system for acid\\/base titrations in non-aqueous solvents  

Microsoft Academic Search

A computer program was developed that could advice on the choice of solvent and titrant for acid\\/base titrations in nonaqueous media. It is shown that the feasibility of a titration in a given solvent can be calculated from solvent properties and intrinsic acid\\/base properties of the sample components. A consistent set of properties for various solvents and a large number

M. Bos; W. E. van der Linden

1996-01-01

431

A Laser-Pointer-Based Spectrometer for Endpoint Detection of EDTA Titrations  

ERIC Educational Resources Information Center

A laser spectrometer for the ethylenediaminetetra-acetic acid (EDTA) titration of magnesium or calcium ions that is designed around a handheld laser pointer as the source and a photoresistor as the detector is developed. Findings show that the use of the spectrometer reduces the degree of uncertainty and error in one part of the EDTA titrations,…

Dahm, Christopher E.; Hall, James W.; Mattioni, Brian E.

2004-01-01

432

An Isothermal Titration Calorimetric Method to Determine the Kinetic Parameters of Enzyme Catalytic Reaction  

E-print Network

of enzyme. The molar reaction heat was calculated from the titration peak area divided by substrate moles per titration, and the initial catalytic reaction rate in the presence of vari- ous concentrations of product can be calculated from the peak height and the molar reaction heat. From Michaelis­Menten function

Luhua, Lai

433

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

Microsoft Academic Search

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

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

2006-01-01

434

Potentiometric surface of the upper Floridan Aquifer in the St. Johns River Water Management District and vicinity, May 1995  

USGS Publications Warehouse

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for May 1995. The map is based on water-level measurements made at more than 900 wells and springs. Approximately 30 new wells were added to better define the potentiometric surface mainly in the northwest area of the map. Data on the map were contoured using 5-foot contour intervals in most areas. Two new wells located north of Rainbow Springs indicate a slight northward extension of the depressed area surrounding the springs. Several new wells in Bradford County indicate a slight reduction in the size of the potentiometric-surface high along the northwest edge of the county. The potentiometric surface of this karstic aquifer generally reflects land surface topography. Potentiometric-surface highs often correspond to topographic highs, which are areas of recharge to the Upper Floridan aquifer. Springs within topographic lows along with areas of more diffuse upward leakage are natural zones of discharge. Municipal, agricultural, and industrial withdrawals have lowered the potentiometric surface in some areas. The potentiometric surface ranged from 127 feet above sea level in Polk County to 84 feet below sea level in southeast Georgia near the St. Marys River. Water levels measured in May 1995 generally were about 0 to 4 feet higher than those measured in May 1994 except in St. Lucie County and near Rainbow Springs, where levels were 1 to 3 feet lower. Generally, May 1995 water levels were 0 to 5 feet lower than levels in September 1994, except near Orlando, where levels were 6 to 12 feet lower, and across the northwest corner of the map area which includes Marion, Alachua, Bradford, Baker, and Nassau Counties, north and west Duval County, and south Georgia. (USGS)

Knowles, Leel, Jr.; O'Reilly, A. M.; Phelps, G.G.; Bradner, L.A.

1995-01-01

435

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

E-print Network

Entropic Effects and Slow Kinetics Revealed in Titrations of D2O-H2O Solutions with Different D titration calorimetry (ITC) to investigate the enthalpy of titration of D2O-H2O solutions with different D to the computed enthalpy for the limit of ideal mixing both for dilution titration and for concentration titration

Jacob, Eshel Ben

436

Kinetic and chemical mechanisms for the effects of univalent cations on the spectral properties of aromatic amine dehydrogenase.  

PubMed Central

Univalent cations and pH influence the UV-visible absorption spectrum of the tryptophan tryptophylquinone (TTQ) enzyme, aromatic amine dehydrogenase (AADH). Little spectral perturbation was observed when pH was varied in the absence of univalent cations. The addition of alkali metal univalent cations (K+, Na+, Li+, Rb+ or Cs+) to oxidized AADH caused significant changes in its absorption spectrum. The apparent Kd for each cation, determined from titrations of the spectral perturbation, decreased with increasing pH. Transient kinetic studies involving rapid mixing of AADH with cations and pH jump revealed that the rate of the cation-induced spectral changes initially decreased with increasing cation concentration to a minimum value, then increased with increasing cation concentration. A kinetic model was developed to fit these data, determine the true pH-independent Kd values for K+ and Na+, and explain the pH-dependence of the apparent Kd. A chemical reaction mechanism, based on the kinetic data, is presented in which the metallic univalent cation facilitates the chemical modification of the TTQ prosthetic group to form an hydroxide adduct which gives rise to the spectral change. Addition of NH4(+)/NH3 to AADH caused changes in the absorption spectrum which were very different form those caused by addition of the metallic univalent cations. The kinetics of the reaction induced by addition of NH4+/NH3 were also different, being simple saturation kinetics. Another reaction mechanism is proposed for the NH4+/NH3-induced spectral change that involves nucleophilic addition of the unprotonated NH3 to TTQ. The general relevance of these data and models to the physiological reactions of TTQ-dependent enzymes and to the roles of univalent cations in modulating enzyme activity are discussed. PMID:9405291

Zhu, Z; Davidson, V L

1998-01-01

437

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

438

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

USGS Publications Warehouse

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

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

1994-01-01

439

Apparent Cooperative Assembly of the Bacterial Cell Division Protein FtsZ Demonstrated by Isothermal Titration Calorimetry*  

E-print Network

by Isothermal Titration Calorimetry* Received for publication, January 27, 2003 Published, JBC Papers in Press isothermal titration calorim- etry (ITC) to measure the heat of FtsZ self-association under various

Erickson, Harold P.

440

Volume 177, number 2 CHEMICAL PHYSICS LETTERS 15 February 1991 Cu titration of tilted CO on a MO( 110) surface  

E-print Network

Volume 177, number 2 CHEMICAL PHYSICS LETTERS 15 February 1991 Cu titration of tilted CO on a MO-reflection-ab- sorption-spectroscopy (IRAS), Auger electron spec- troscopy (AES), as well as Cu titration. As will be seen

Goodman, Wayne

441

Structures of Prolyl Oligopeptidase Substrate/Inhibitor Complexes USE OF INHIBITOR BINDING FOR TITRATION OF THE CATALYTIC HISTIDINE RESIDUE*  

E-print Network

FOR TITRATION OF THE CATALYTIC HISTIDINE RESIDUE* Received for publication, August 3, 2000, and in revised form- teases. The new titration method gave a single pKa for prolyl oligopeptidase, whose reaction exhibited

Fülöp, Vilmos

442

Acid-base titrations by stepwise addition of equal volumes of titrant with special reference to automatic titrations-II Theory of titration of mixtures of acids, polyprotic acids, acids in mixture with weak bases, and ampholytes.  

PubMed

A general method for evaluating titration data for mixtures of acids and for acids in mixture with weak bases is presented. Procedures are given that do not require absolute [H]-data, i.e., relative [H]-data may be used. In most cases a very rough calibration of the electrode system is enough. Further, for simple systems, very approximate values of the stability constants are sufficient. As examples, the titration of the following are treated in some detail: a mixture of two acids, a diprotic acid, an acid in presence of its conjugate base, and an ampholyte. PMID:18961983

Pehrsson, L; Ingman, F; Johansson, S

443

Binding isotherms for soluble immobilized affinity ligands from spectral titration.  

PubMed

The method of spectral titration has been applied to binding equilibria between proteins and soluble immobilized ligands and evaluated using the interaction between Cibacron blue-dextran conjugates and lysozyme. The method is both simple and rapid and provides a convenient screening technique for characterization of soluble adsorbents designed for use in aqueous two-phase affinity extraction or as liquid-phase models for affinity chromatography systems. The results indicate that regardless of ligand density a constant 28% of the total coupled dye is available for high-affinity protein binding at saturation. The dissociation constant for the dye-protein interaction, however, decreases with dye loading. The potential for kinetic investigations has been demonstrated using a stopped-flow apparatus. The results indicate that a simple rate equation is inadequate to describe the data for lysozyme binding to dye-dextran conjugates. A modified model, which better describes the data, was developed by including a second rate limiting process, the transition from stacked to unstacked dye ligands on the dextran backbone. This effect could have practical significance for protein binding kinetics in affinity chromatography, especially in high-performance liquid affinity chromatography applications where mass transfer is rapid. PMID:18601078

Mayes, A G; Eisenthal, R; Hubble, J

1992-12-01

444

Application of isothermal titration calorimetry in bioinorganic chemistry.  

PubMed

The thermodynamics of metals ions binding to proteins and other biological molecules can be measured with isothermal titration calorimetry (ITC), which quantifies the binding enthalpy (?H°) and generates a binding isotherm. A fit of the isotherm provides the binding constant (K), thereby allowing the free energy (?G°) and ultimately the entropy (?S°) of binding to be determined. The temperature dependence of ?H° can then provide the change in heat capacity (?C (p)°) upon binding. However, ITC measurements of metal binding can be compromised by undesired reactions (e.g., precipitation, hydrolysis, and redox), and generally involve competing equilibria with the buffer and protons, which contribute to the experimental values (K (ITC), ?H (ITC)). Guidelines and factors that need to be considered for ITC measurements involving metal ions are outlined. A general analysis of the experimental ITC values that accounts for the contributions of metal-buffer speciation and proton competition and provides condition-independent thermodynamic values (K, ?H°) for metal binding is developed and validated. PMID:20725755

Grossoehme, Nicholas E; Spuches, Anne M; Wilcox, Dean E

2010-11-01

445

Hot biological catalysis: isothermal titration calorimetry to characterize enzymatic reactions.  

PubMed

Isothermal titration calorimetry (ITC) is a well-described technique that measures the heat released or absorbed during a chemical reaction, using it as an intrinsic probe to characterize virtually every chemical process. Nowadays, this technique is extensively applied to determine thermodynamic parameters of biomolecular binding equilibria. In addition, ITC has been demonstrated to be able of directly measuring kinetics and thermodynamic parameters (kcat, KM, ?H) of enzymatic reactions, even though this application is still underexploited. As heat changes spontaneously occur during enzymatic catalysis, ITC does not require any modification or labeling of the system under analysis and can be performed in solution. Moreover, the method needs little amount of material. These properties make ITC an invaluable, powerful and unique tool to study enzyme kinetics in several applications, such as, for example, drug discovery. In this work an experimental ITC-based method to quantify kinetics and thermodynamics of enzymatic reactions is thoroughly described. This method is applied to determine kcat and KM of the enzymatic hydrolysis of urea by Canavalia ensiformis (jack bean) urease. Calculation of intrinsic molar enthalpy (?Hint) of the reaction is performed. The values thus obtained are consistent with previous data reported in literature, demonstrating the reliability of the methodology. PMID:24747990

Mazzei, Luca; Ciurli, Stefano; Zambelli, Barbara

2014-01-01

446

Colorimetric nanoplasmonic assay to determine purity and titrate extracellular vesicles.  

PubMed

Extracellular Vesicles (EVs) - cell secreted vesicles that carry rich molecular information of the parental cell and constitute an important mode of intercellular communication - are becoming a primary topic in translational medicine. EVs (that comprise exosomes and microvesicles/microparticles) have a size ranging from 40 nm to 1 ?m and share several physicochemical proprieties, including size, density, surface charge, and light interaction, with other nano-objects present in body fluids, such as single and aggregated proteins. This makes separation, titration, and characterization of EVs challenging and time-consuming. Here we present a cost-effective and fast colorimetric assay for probing by eye protein contaminants and determine the concentration of EV preparations, which exploits the synergy between colloidal gold nanoplasmonics, nanoparticle-protein corona, and nanoparticle-membrane interaction. The assay hits a limit of detection of protein contaminants of 5 ng/?L and has a dynamic range of EV concentration ranging from 35 fM to 35 pM, which matches the typical range of EV concentration in body fluids. This work provides the first example of the exploitation of the nanoparticle-protein corona in analytical chemistry. PMID:25674701

Maiolo, Daniele; Paolini, Lucia; Di Noto, Giuseppe; Zendrini, Andrea; Berti, Debora; Bergese, Paolo; Ricotta, Doris

2015-04-21

447

Probing lectin-mucin interactions by isothermal titration microcalorimetry.  

PubMed

Isothermal titration microcalorimetry (ITC) can directly determine the thermodynamic binding parameters of biological molecules including affinity constant, binding stoichiometry, and heat of binding (enthalpy) and indirectly the entropy and free energy of binding. ITC has been extensively used to study the binding of lectins to mono- and oligosaccharides, but limited applications to lectin-glycoprotein interactions. Inherent experimental challenges to ITC include sample precipitation during the experiment and relative high amount of sample required, but careful design of experiments can minimize these problems and allow valuable information to be obtained. For example, the thermodynamics of binding of lectins to multivalent globular and linear glycoproteins (mucins) have been described. The results are consistent with a dynamic binding mechanism in which lectins bind and jump from carbohydrate to carbohydrate epitope in these molecules leading to increased affinity. Importantly, the mechanism of binding of lectins to mucins appears similar to that for a variety of protein ligands binding to DNA. Recent results also show that high affinity lectin-mucin cross-linking interactions are driven by favorable entropy of binding that is associated with the bind and jump mechanism. The results suggest that the binding of ligands to biopolymers, in general, may involve a common mechanism that involves enhanced entropic effects that facilitate binding interactions. PMID:25253134

Dam, Tarun K; Brewer, C Fred

2015-01-01

448

Enzyme kinetics determined by single-injection isothermal titration calorimetry.  

PubMed

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

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

2015-04-01

449

Isothermal titration calorimetric analysis on solubilization of an octane oil-in-water emulsion in surfactant micelles and surfactant-anionic polymer complexes.  

PubMed

Polymers may alter the ability of surfactant micelles to solubilize hydrophobic molecules depending on surfactant-polymer interactions. In this study, isothermal titration calorimetry (ITC) was used to investigate the solubilization thermodynamics of an octane oil-in-water emulsion in anionic sodium dodecylsulphate (SDS), nonionic polyoxyethylene sorbitan monooleate (Tween 80), cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles and respective complexes formed by these micelles and an anionic polymer (carboxymethyl cellulose). Results indicated that the oil solubilization in single ionic micelles was endothermic, while in nonionic micelles or mixed ionic/nonionic micelles it was exothermic. The addition of carboxymethyl cellulose did not influence the solubilization behavior in these micelles, but affected the solubilization capacities of these systems. The solubilization capacity of cationic micelles or mixed cationic/nonionic micelles was enhanced while that of nonionic or anionic micelles was decreased. Based on the phase separation model, a molecular pathway mechanism driven by enthalpy was proposed for octane solubilization in surfactant micelles and surfactant-polymer complexes. PMID:25454419

Zhang, Hui; Zeeb, Benjamin; Salminen, Hanna; Weiss, Jochen

2015-01-15

450

On the virtue of acid–base titrations for the determination of basic sites in nitrogen doped carbon nanotubes  

Microsoft Academic Search

The basicity and nature of basic species in nitrogen containing carbon nanotubes (NCNT) prepared under different conditions were investigated by acid–base titrations. Proton uptake curves were derived from the titration data and were used to establish the basicity (pKa) ranges of nitrogen species present in NCNT. Based on the evolution of the titration curves upon acid addition the NCNT were

J. H. Bitter; S. van Dommele; K. P. de Jong

2010-01-01

451

Supplementary Material Figure S1: Result of combinatorial scan on the titration curves of Glu78 and Glu172  

E-print Network

Supplementary Material Figure S1: Result of combinatorial scan on the titration curves of Glu78: Global fit of NMR titration curves for FNfn10: Asp7: black curve, Glu9: blue curve, Asp23: red curve. NMR titration data is represented by dots. #12;Figure S4: Global fit of His12 (black curve) and His119 (blue

McIntosh, Lawrence P.

452

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

USGS Publications Warehouse

Water-level measurements were made in 84 wells open to the upper Cape Fear aquifer at the end of 1986 to determine the configuration of its potentiometric surface over an area of approximately 5,500 sq mi. The major feature of the potentiometric surface is the development of a large, almost circular cone of depression as a result of the merging of a number of smaller cones. The center of the large cone lies along an axis between Greenville and Kinston. The potentiometric surface in the upper Cape Fear is nearly 100 ft below sea level at Greenville; it is more than 100 ft above sea level south of the Neuse River near Colorado.

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

1989-01-01

453

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

E-print Network

are serried out bp setting the oscillator at one of these optimum frequencies ~ This fre- quenop is held oonstent Chroughout the titration. The end-point is shown bp an abrupt shape in the output of ths osoillator, This msp be produosd in several wars... disaypssrsnoe at ths end-point senses the ohange in the output. Titrations msp be serried out at frequenoies showing small differ- ences in absorption between the substanoes involved in the titration. Eowever at suoh frequenoies the sn4-point is mush less...

Griffin, James Hilton

1940-01-01

454

Ionic equilibria in neutral amphiprotic solvents of low dielectric constant: Titration curves.  

PubMed

Titration curves have been simulated for the titration of acids, bases and salts in neutral amphiprotic solvents such as isopropyl and tert-butyl alcohols. Ranges of pK values and acid concentrations have been examined. The incomplete dissociation of salts, which increases the acid or basic strength, has been found to be the major factor modifying the shape of the curve and the pH break. The theoretical predictions have been checked by titrating several series of acids and good agreement has been obtained between computed and experimental results. PMID:18964769

Bosch, E; Rosés, M

1989-06-01

455

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.

Durán, Alejandro; Cortina, Montserrat; Velasco, Lya; Rodríguez, José Antonio; Alegret, Salvador; del Valle, Manuel

2006-01-01

456

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

457

Potentiometric determination of free acidity and uranium in uranyl nitrate solutions  

Microsoft Academic Search

Free acid and uranium in uranyl nitrate solutions have been determined potentiometrically using Na2SO4–NaOH, Na2SO4–Na2CO3 and (NH4)2SO4–NaOH complexant-titrant combinations. The overall recovery of nitric acid varies in the range of 95.25 to 118.5%, depending upon the acid as well as the total uranium present, while that of uranium always a positive bias ranging from 100.2 to 106.4%. The results have

M. Anwar; D. Mohammad

1989-01-01

458

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

SciTech Connect

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

None

1996-12-01

459

Biomimetic norfloxacin sensors made of molecularly-imprinted materials for potentiometric transduction  

Microsoft Academic Search

A biomimetic sensor for norfloxacin is presented that is based on host-guest interactions and potentiometric transduction.\\u000a The artificial host was imprinted into polymers made from methacrylic acid and\\/or 2-vinyl pyridine. The resulting particles\\u000a were entrapped in a plasticized poly(vinyl chloride) (PVC) matrix. The sensors exhibit near-Nernstian response in steady state\\u000a evaluations, and detection limits range from 0.40 to 1.0 ?g?mL?1, respectively,

Felismina T. C. Moreira; Victor A. P. Freitas; Maria G. F. Sales

2011-01-01

460

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

461

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

462

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

463

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

SciTech Connect

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

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

2008-01-01

464

A note on the calculation of acid-base titration curves and their equivalence points.  

PubMed

An equation has been developed for the calculation of the titration curve of any mixture of acids and bases, and an alternative way of defining an equivalence point, suitable for computer calculations, is presented. PMID:18962361

Olin, A; Wallén, B

465

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

Code of Federal Regulations, 2010 CFR

...precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10...

2010-07-01

466

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

Code of Federal Regulations, 2012 CFR

...precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10...

2012-07-01

467

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

Code of Federal Regulations, 2011 CFR

...precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10...

2011-07-01

468

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

Code of Federal Regulations, 2013 CFR

...precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10...

2013-07-01

469

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

Code of Federal Regulations, 2014 CFR

...precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the determination (Charlot, “Ann. chim, anal,”, 1945, 27, 153; Booth; “J. Soc. Leather Trades' Chemists,” 1956, 40, 238). Apparatus Burrette, 10...

2014-07-01

470

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

471

A Computer-Based Simulation of an Acid-Base Titration  

ERIC Educational Resources Information Center

Reviews the advantages of computer simulated environments for experiments, referring in particular to acid-base titrations. Includes pre-lab instructions and a sample computer printout of a student's use of an acid-base simulation. Ten references. (PR)

Boblick, John M.

1971-01-01