scholarly journals Acid-base equilibria of 2,4-diiodo-6-methylphenylcarbamoylmethyl iminodiacetic acid and its labeling with technetium-99m

2006 ◽  
Vol 71 (1) ◽  
pp. 55-65 ◽  
Author(s):  
Jasmina Brboric ◽  
Mirjana Jovanovic ◽  
Gordana Popovic ◽  
Vera Kapetanovic ◽  
Sote Vladimirov
Keyword(s):  
Ionic Strength ◽  
Radiochemical Purity ◽  
Equilibrium Constants ◽  
Iminodiacetic Acid ◽  
Carboxylic Group ◽  
Acid Base ◽  
Acidity Constants ◽  
Technetium 99M ◽  
Ph Range ◽  
Influence Of Ph

The acid-base equilibria of a novel hepatobiliary imaging agent, 2,4-diiodo-6-methylphenylcarbamoylmethyl iminodiacetic acid (DIIODIDA) were studied. The potentiometrically determined acidity constants of the second carboxylic group, amino and amide groups were pK2 = 2.52 ? 0.02; pK3 = 5.86 ? 0.06 and pK4 = 10.9 ? 0.1. The determinations were performed at 25 ?C and an ionic strength of 0.1 mol/dm3 (NaCl). The acidity constants (pK1 = 1.3 ? 0.4) corresponding to the first carboxylic group was determined indirectly, on the basis of equilibrium constants obtained in a heterogeneous system, at 25 ?C and an ionic strength 1 mol/dm3 (HCl, NaCl). DIIODIDA was labeled with technetium-99m, and the influence of pH on the yield of labeling was investigated. It was found that labeling within the pH range from 5.5 to 6.5 provided a radiopharmaceutical of high radiochemical purity (>98 %).

Influence of pH on the Absorption and Fluorescence Spectra of 6,7-Dihydroxycoumarin in Aqueous Solution

1982 ◽  
Vol 37 (3) ◽  
pp. 262-265 ◽  
Author(s):  
Jerzy Grzywacz ◽  
Stanisława Taszner
Keyword(s):  
Aqueous Solution ◽  
Fluorescence Spectra ◽  
Singlet State ◽  
Ph Value ◽  
Emission Spectra ◽  
Excited Singlet ◽  
Acid Base ◽  
Wide Ph Range ◽  
Ph Range ◽  
Influence Of Ph

Abstract Absorption and emission spectra of 6,7-dihydroxycoumarin [6,7-DHC] in aqueous solution over a wide pH range are reported. The absorption spectra proved to be strongly sensitive to the pH-value of the solution, whereas the emission spectra change in this range only insignificantly. An interpretation is attempted on the basis of the differences of the acid-base properties of the 6,7-DHC molecule in its ground and excited singlet state. For this purpose the pKa's and pKax's values have been calculated. It has been stated that in the excited state the phototautomer form is very unlikely.

Acid−Base Equilibrium Constants for Glycine in NaClO4, KCl, and KBr at 298 K. Dependence on Ionic Strength

1998 ◽  
Vol 43 (5) ◽  
pp. 876-879 ◽  
Author(s):  
P. Alonso ◽  
J. L. Barriada ◽  
P. Rodríguez ◽  
I. Brandariz ◽  
M. E. Sastre de Vicente
Keyword(s):  
Ionic Strength ◽  
Equilibrium Constants ◽  
Acid Base ◽  
Base Equilibrium ◽  
Acid Base Equilibrium ◽  
Dependence On Ionic Strength

scholarly journals Protolytic equlibria of bromazepam

2002 ◽  
Vol 67 (3) ◽  
pp. 187-195 ◽  
Author(s):  
Lidija Pfendt ◽  
Gordana Popovic ◽  
Tatjana Damjanovic ◽  
Dusan Sladic
Keyword(s):  
Heterogeneous System ◽  
Nmr Spectra ◽  
Equilibrium Constants ◽  
Heterogeneous Systems ◽  
13C Nmr Spectra ◽  
Acidic Media ◽  
Acidity Constants ◽  
Protonation Site ◽  
Pyridine Nitrogen ◽  
Ph Range

The protolytic equilibria of bromazepam, an ampholyte sparingly soluble in water, in homogeneous and heterogeneous systems were studied in the pH range 0?14 at 25?C and at ionic strength of 0.1 mol/dm3 (NaCl). On the basis of 13C-NMR spectra, the protonation site was predicted ? in acidic media the pyridine nitrogen of bormazepam is protonated. The acidity constants of bromazepam were determined spectrophotometrically (pKa1 2.83 and pKa2 11.60) and potentiometrically (pKa1 2.99). In the heterogeneous system the following equilibrium constants were determined: Ks0 =[HA]?(pKs0 3.44), Ks1 =[H2A+]/[H3O+](pKs1 0.61), and Ks2 =[A-][H3O+](pKs2 15.04).

scholarly journals Acid-base equilibria of the Zn(II) and Fe(III) complexes with condensation products of 2-acetylpyridine and the dihydrazide of oxalic and malonic acid

2009 ◽  
Vol 74 (3) ◽  
pp. 269-277 ◽  
Author(s):  
Branka Drazic ◽  
Gordana Popovic ◽  
Ratomir Jelic ◽  
Dusan Sladic ◽  
Dragana Mitic ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Cytotoxic Activity ◽  
Malonic Acid ◽  
Equilibrium Constants ◽  
Aqueous Media ◽  
Constant Ionic Strength ◽  
Acid Base ◽  
Condensation Products

Acid-base equilibria of Zn(II) and Fe(III) complexes with N',N'2-bis- [(1E)-1-(2-pyridyl)ethylidene]ethanedihydrazide (ligand L1) and N',N'2-bis[(1E)- -1-(2-pyridyl)ethylidene]propanedihydrazide (ligand L2), i.e., [Fe(L1)Cl2(H2O)], [Fe(L2)Cl(H2O)]2+, [Zn(L1)(H2O)3]+ and [Zn(L2)(H2O)2]2+, which expressed cytotoxic activity, were investigated in aqueous media. The equilibrium constants were determined potentiometrically at 25?C at a constant ionic strength of 0.10 mol/dm3 (Na2SO4). The results showed that at pH < 8 both the Fe(III) complexes studied here have three, while [Zn(L1)(H2O)3]+ and [Zn(L2)(H2O)2]2+ have one and two titratable protons, respectively. Based on the obtained values for the equilibrium constants, protonation schemes of the examined complexes are proposed.

scholarly journals BUFFER SOLUTIONS BASED ON TAURINE

2021 ◽  
Vol 26 (1(77)) ◽  
pp. 48-64
Author(s):  
T. S. Ben’kovs’ka ◽  
R. E. Khoma ◽  
A. N. Chebotaryov ◽  
A. A.-A. Ennan ◽  
L. T. Osadchiy
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Buffer Capacity ◽  
Water System ◽  
Acid Base ◽  
Buffer Zones ◽  
Base Interaction ◽  
Temperature Range ◽  
Temperature Dependences ◽  
Ph Range

The acid-base interaction in the aminoethanesulfonic acid (taurine, Tau) – potassium aminoethanesulfonate – water system was studied by pH-, redox- and conductometric methods in the temperature range 293–313 K. The ion-molecular composition of NH2CH2CH2SO3H –NH2CH2CH2SO3K – H2O system was calculated. It is shown aminoethanesulfonic acid in aqueous solutions to exist at the ratio CKOH/QTau < 0.5 mainly in the zwitterion form similar to systems with glycine, aminomethanesulfonic acid and its N‑alkylated derivatives. The content of the aminoethanesulfonate anion is directly proportional to the CKOH/QGly ratio. The studied system ionic strength and acid-base dissociation constant for the second stage of the aminoethanesulfonic acid concentration and temperature dependences were determined. The ionic strength values at the isoelectric point (mi.p.)are directly proportional to С0Tau and practically do not depend on the temperature within the error for the same series С0Tau and С0KOH .The pH limits of the buffer action are determined and the buffer capacity of these systems is estimated. It has been established that effective buffer zones of Tau aqueous solutions can to maintain acidity in the higher then physiological pH range at temperature range 293–313 K. The buffer capacity of NH2CH2CH2SO3H – NH2CH2CH2SO3K – H2O system exceeds the analogous values of YNHCH2SO3H – YNHCH2SO3K – H2O (Y = H, CH3, CH2CH2OH, C(CH3)3 and C2H5C6H5) systems. The obtained data on the buffer capacity of the aminoethanesulfonic acid – potassium aminoethanesulfonate – water system can be used in chemical analysis, microbiological and biochemical studies, and the acidity data of the solutions studied can simulate the chemisorption of acid gases (carbon and sulfur dioxides).

scholarly journals Protolytic equilibria in homogeneous and heterogeneous systems of ketoconazole and its direct spectrophotometric determination in tablets

2005 ◽  
Vol 70 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Mirjana Vojic ◽  
Gordana Popovic ◽  
Dusan Sladic ◽  
Lidija Pfendt
Keyword(s):  
Ionic Strength ◽  
Spectrophotometric Determination ◽  
Spectrophotometric Method ◽  
Equilibrium Constants ◽  
Heterogeneous Systems ◽  
Water Systems ◽  
Acidity Constant ◽  
Acid Base ◽  
Protolytic Equilibria

The acid-base equilibria of a diprotic, slightly hydrosoluble base ketoconazole were studied in homogeneous and heterogeneous water systems. The determinations were performed at 25?C at a constant ionic strength of M(NaCl). The acidity constant Ka1 was determined by potentiometric (pKa1 3.20) and spectrophotometric (pKa1 3.26) methods. A pKa2 constant of 6.10 was obtained based on the equilibrium constants pKs0 4.84 and pKs1 -1.26, determined in a heterogeneous ketoconazole system. The obtained values of the constants served to calculate the solubility and the distribution of the equilibrium forms of ketoconazole as a function of pH. On the basis of the distribution of the equilibrium forms of ketoconazole, a spectrophotometric method for the determination of its content in commercial tablets was developed. The determinations were performed at 225 nm in 0.1 M HCl. The method is simple and rapid and enables the direct spectrophotometric determination of the content of ketoconazole without previous isolation.

The influence of pH in the tautomerism of 9,10-anthracenediols and 1,3-diketones

1986 ◽  
Vol 64 (1) ◽  
pp. 127-132
Author(s):  
John C. Anderson ◽  
A. Douglas Broadbent
Keyword(s):  
Total Concentration ◽  
Equilibrium Constants ◽  
Acid Base ◽  
Influence Of Ph

Equations have been derived to describe how the ratio of the total concentration of all keto forms to that of all enolic forms (K′) varies with changing pH, for a tautomeric system in which the enol and ketone are polyprotic acids. The influence of pH on the tautomerism of 2-amino-9,10-anthracenediol, 2,9,10-anthracenetriol, 2,4-pentanedione, and 1-(3-pyridyl)-1,3-butanedione was examined. The equilibrium constants for all the acid–base equilibria involved were calculated from the dependence of K′ on pH.

scholarly journals Acid-base behaviour of sanguinarine and dihydrosanguinarine

2009 ◽  
Vol 7 (4) ◽  
pp. 876-883 ◽  
Author(s):  
Helena Absolínová ◽  
Luděk Jančář ◽  
Irena Jančářová ◽  
Jaroslav Vičar ◽  
Vlastimil Kubáň
Keyword(s):  
Optical Properties ◽  
Acetic Acid ◽  
Ionic Strength ◽  
Equilibrium Constants ◽  
Ionic Species ◽  
Transport Proteins ◽  
Priority Effect ◽  
Acid Base ◽  
Strength Of Interaction ◽  
Transition Reaction

AbstractAcid-base and optical properties of sanguinarine and dihydrosanguinarine were studied in the presence of HCl, HNO3, H2SO4, H3PO4, CAPSO and acetic acid (HAc) of different concentrations and their mixtures. The equilibrium constants pKR+ of the transition reaction between an iminium cation Q+ of sanguinarine and its uncharged QOH (pseudo-base, 6-hydroxy-dihydroderivative) form were calculated. A numerical interpretation of the A-pH curves by a SQUAD-G computer program was used. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to alkaline medium were observed. The shifts depend on the type and concentration of inert electrolyte (the most remarkable for HNO3 and HCl). The corresponding pKR+ values ranged from 7.21 to 8.16 in the same manner (ΔpKR+ = 0.81 and 0.73 for HNO3 and HCl, respectively). The priority effect of ionic species and ionic strength was confirmed in the presence of NaCl and KCl. The strength of interaction of SA with bioactive compounds (i.e. receptors, transport proteins, nucleic acids etc.) may be affected because of the observed influence of both cations and anions of the inert electrolytes.

Beryllium-chrome-azurol-S complexes

1968 ◽  
Vol 21 (3) ◽  
pp. 603 ◽  
Author(s):  
WG Baldwin ◽  
DR Stranks
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Ion Exchange ◽  
Stability Constant ◽  
Anionic Complex ◽  
Acidity Constants ◽  
Chrome Azurol S ◽  
Major Species ◽  
The Stability ◽  
Ph Range

Complex formation between the aquated beryllium cation and the tetrabasic dyestuff chrome-azurol-S (H4CAS) has been studied by spectrophotometric, potentiometric, electrophoretic, and ion-exchange techniques. At least two complexes are shown to exist within the pH range 3-6. The major species is the anionic complex BeHCAS- for which log β11, = 4.66 � 0.08 at 25� and at ionic strength 0.lM (NaClO4) Coordination of beryllium is considered to occur at the quinonoid-,). carboxylato site in the HCAS8- ligand. The stability constant for the dinuclear species Be2CASO is shown to be log β21 = 15.8 � 0.1 under the same medium conditions. The dinuclear complex interferes with spectrophotometric measurements at beryllium concentrations exceeding 2.5 x 10-4. The acidity constants of H4CAS were determined at 25� and at an ionic strength 0.IM (NaClO,) as pK2a = 2.25 � 0.10,pK3a, = 4.88 � 0.05, pK4, = 11.75 � 0.05, whilst pK1a = -1.2 � 0.4.

scholarly journals Spectrophotometric study of time stability and acid-base characteristics of chelerythrine and dihydrochelerythrine

2010 ◽  
Vol 8 (3) ◽  
pp. 626-632 ◽  
Author(s):  
Helena Absolínová ◽  
Luděk Jančář ◽  
Irena Jančářová ◽  
Jaroslav Vičar ◽  
Vlastimil Kubáň
Keyword(s):  
Ionic Strength ◽  
Spectral Properties ◽  
Equilibrium Constants ◽  
Ionic Species ◽  
Spectrophotometric Study ◽  
Time Stability ◽  
Priority Effect ◽  
Acid Base ◽  
Strength Of Interaction ◽  
Transition Reaction

AbstractTime stability, acid-base and UV-VIS spectral properties of dihydrochelerythrine (DHCHE) were studied spectrophotometrically in water:methanol and water:ethanol media. DHCHE is stable in strongly acid milieu (pH HCl, HNO3, H2SO4, H3PO4 and their mixtures. Remarkable shifts of formation parts of absorbance-pH (A-pH) curves to the alkaline medium were observed depending on the type and concentration of inert electrolyte (most remarkable for HNO3 and HCl). The corresponding equilibrium constants pKR+ of the transition reaction between charged iminium Q+ and uncharged QOH (pseudo-base, 6-hydroxy-dihydro derivative) forms of chelerythine were calculated using a numerical interpretation of A-pH curves by a SQUAD-G computer program which ranged from 8.51–9.31. The highest changes of ΔpK R+ (0.75 and 0.53) were observed for H3PO4 and H2SO4, respectively. The priority effect of ionic species and ionic strength was confirmed in the presence of additions of NaCl and KCl. The strength of interaction of CHE with biomacromolecular compounds (i.e., peptides, proteins, nucleic acids etc.) may be affected because of the observed influence of both cation and anion of the inert electrolyte on acid-base behavior.

Sign in / Sign up

Export Citation Format

Share Document