scholarly journals Speciation Studies of L-Histidine Complexes of Pb(II), Cd(II), and Hg(II) in DMSO-Water Mixtures

2012 ◽  
Vol 2012 ◽  
pp. 1-9
Author(s):  
K. Bharath Kumar Naik ◽  
B. Ananda Kumar ◽  
S. Raju ◽  
G. Nageswara Rao
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Complex Formation ◽  
Species Distribution ◽  
Statistical Parameters ◽  
Experimental Conditions ◽  
Equilibrium Study ◽  
Predominant Species ◽  
Chemical Models ◽  
Best Fit

Equilibrium study on complex formation of L-histidine with Pb(II), Cd(II), and Hg(II) has been investigated pH metrically in DMSO-water mixtures (0–60% v/v) at 303 K and 0.16 mol L−1 ionic strength. The predominant species detected for Pb(II) and Cd(II) are ML2H4, ML2H3, ML2H2, ML2H, and ML2 and those for Hg(II) are ML2H4, ML2H3, ML2, and ML. The appropriateness of experimental conditions is verified by introducing errors intentionally in the concentrations of ingredients. The models containing different numbers of species were refined by using the computer program MINIQUAD75. The best-fit chemical models were arrived at based on statistical parameters. The trend in variation of stability constants of the complexes with dielectric constant of the medium is attributed to the electrostatic and nonelectrostatic forces. The species distribution and the plausible equilibria for the formation of the species are also presented.

Effect of Solvent on Protonation Equilibria of L-Serine and L-Tryptophan in Ethylene Glycol-Water Mixtures

2021 ◽  
Vol 25 (7) ◽  
pp. 124-129
Author(s):  
Ch. Sudhakar ◽  
Allabakshu Shaik ◽  
M. Ramanaiah ◽  
Ch. Nageswara Rao
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Protonation Constants ◽  
Statistical Parameters ◽  
Protonation Equilibria ◽  
Effect Of Solvent ◽  
R Factor ◽  
Chemical Models ◽  
Best Fit ◽  
Skewness And Kurtosis

Protonation equilibria of L-serine and L-tryptophan in varying compositions (0.0-50.0 % v/v) of ethylene glycol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1 using sodium chloride. The protonation constants have been calculated with the computer program MINIQUAD 75 and are selected based on statistical parameters. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, χ2, skewness and kurtosis. The protonation constants of L-serine and L-tryptophan change linearly with increasing ethylene glycol content. This is attributed to the dielectric constant of the medium.

scholarly journals Effect of Solvent on Protonation Equilibria ofL-Proline andL-Valine in 1, 2-Propanediol-Water Mixtures

2012 ◽  
Vol 9 (2) ◽  
pp. 517-524 ◽  
Author(s):  
P. Bhushanavathi ◽  
B. Veeraswamy ◽  
G. Nageswara Rao ◽  
U. Viplavaprasad
Keyword(s):  
Dielectric Constant ◽  
Sodium Chloride ◽  
Ionic Strength ◽  
Protonation Constants ◽  
Protonation Equilibria ◽  
Effect Of Solvent ◽  
R Factor ◽  
Chemical Models ◽  
Best Fit ◽  
Skewness And Kurtosis

Protonation equilibria ofL-proline and L-valine in varying compositions (0.0-60.0% v/v) of 1, 2-Propanediol-water mixtures were investigated pH-metrically. Titrations were performed at 303.0 K and the ionic strength of the medium was maintained at 0.16 mol L-1using sodium chloride. The best fit chemical models of the protonation equilibria were based on crystallographic R-factor, Χ2, skewness, and kurtosis. All the protonation constants of proline and valine increased with increasing propanediol content. This is attributed to the dielectric constant of the medium.

scholarly journals Mononuclear Binary Complex Formation Equilibria of L-Ornithine with Biologically Essential Metals in TBAB Micellar Media

2019 ◽  
Vol 31 (6) ◽  
pp. 1383-1388
Author(s):  
A.G. ATNAFU ◽  
R. SRINIVASU ◽  
P. SHYAMALA ◽  
G. NAGESWARA RAO
Keyword(s):  
Ionic Strength ◽  
Tetrabutylammonium Bromide ◽  
Binary Complex ◽  
Statistical Parameters ◽  
Complex Formation Equilibria ◽  
Surfactant Micelle ◽  
Ph Values ◽  
Chemical Models ◽  
Formation Equilibria ◽  
Best Fit

Investigation of mononuclear complex of L-ornithine in tetrabutylammonium bromide (TBAB, a cationinc surfactant) micelle media has been made pH metrically at constant temperature and ionic strength in different percentage of micellar solutions (0.0-2.5 %). Stability constants and best fit model for metal complexes were obtained by MINIQUAD75 computer program on the basis of the analysis of residues and other statistical parameters. Accordingly, ML, ML2, MLH and ML2H for both Co(II) and Cu(II) and ML2 and ML2H for Ni(II) mononuclear chemical models were obtained. The stabilization/destabilization equilibria of the binary system for the model species with percentage composition of micelles at constant ionic strength and temperature could be attributed to dielectric constant and other intrinsic interaction properties of tetrabutylammonium bromide micelle with ligands and metal ions. The plot of percentage of species against pH values has been generated from SIM refined data using origin85 software.

scholarly journals Understanding the Solution Behavior of Epinephrine in the Presence of Toxic Cations: A Thermodynamic Investigation in Different Experimental Conditions

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 511 ◽  
Author(s):  
Francesco Crea ◽  
Concetta De Stefano ◽  
Anna Irto ◽  
Gabriele Lando ◽  
Stefano Materazzi ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Formation Constants ◽  
Titration Calorimetry ◽  
Interaction Theory ◽  
Thermodynamic Investigation ◽  
Experimental Conditions ◽  
Complex Formation Constants ◽  
Specific Ion Interaction Theory ◽  
Enthalpy Changes

The interactions of epinephrine ((R)-(−)-3,4-dihydroxy-α-(methylaminomethyl)benzyl alcohol; Eph−) with different toxic cations (methylmercury(II): CH3Hg+; dimethyltin(IV): (CH3)2Sn2+; dioxouranium(VI): UO22+) were studied in NaClaq at different ionic strengths and at T = 298.15 K (T = 310.15 K for (CH3)2Sn2+). The enthalpy changes for the protonation of epinephrine and its complex formation with UO22+ were also determined using isoperibolic titration calorimetry: ΔHHL = −39 ± 1 kJ mol−1, ΔHH2L = −67 ± 1 kJ mol−1 (overall reaction), ΔHML = −26 ± 4 kJ mol−1, and ΔHM2L2(OH)2 = 39 ± 2 kJ mol−1. The results were that UO22+ complexation by Eph− was an entropy-driven process. The dependence on the ionic strength of protonation and the complex formation constants was modeled using the extended Debye–Hückel, specific ion interaction theory (SIT), and Pitzer approaches. The sequestering ability of adrenaline toward the investigated cations was evaluated using the calculation of pL0.5 parameters. The sequestering ability trend resulted in the following: UO22+ >> (CH3)2Sn2+ > CH3Hg+. For example, at I = 0.15 mol dm−3 and pH = 7.4 (pH = 9.5 for CH3Hg+), pL0.5 = 7.68, 5.64, and 2.40 for UO22+, (CH3)2Sn2+, and CH3Hg+, respectively. Here, the pH is with respect to ionic strength in terms of sequestration.

scholarly journals Mixed ligand complexes of essential metal ions with L-glutamine and succinic acid in SLS-water mixtures

2012 ◽  
Vol 77 (4) ◽  
pp. 453-463 ◽  
Author(s):  
Hima Bindu ◽  
Nageswara Rao
Keyword(s):  
Succinic Acid ◽  
Electrostatic Interactions ◽  
Ternary Complexes ◽  
Mixed Ligand ◽  
Mixed Ligand Complexes ◽  
Statistical Parameters ◽  
Chemical Models ◽  
Chelate Effect ◽  
Binary Complexes ◽  
Best Fit

Speciation of mixed ligand complexes of Co(II), Ni(II) and Cu(II) with L-glutamine and succinic acid was studied in varying amounts (0.0-2.5% w/v) of sodium lauryl sulphate in aqueous solutions maintaining an ionic strength of 0.16 mol L-1 (NaCl) at 303.0 K. Titrations were carried out in the presence of different relative concentrations (M : L : X = 1 : 2 : 2, 1 : 4 : 2, 1 : 2 : 4) of metal (M) to L-glutamine (L) to succinic acid (X) with sodium hydroxide. Stability constants of ternary complexes were refined with MINIQUAD75. The best-fit chemical models were selected based on statistical parameters and residual analysis. The species detected were ML2X, MLX, MLXH and MLXH2 for Co(II), Ni(II) and Cu(II). Extra stability of ternary complexes compared to their binary complexes was believed to be due to electrostatic interactions of the side chains of ligands, charge neutralization, chelate effect, stacking interactions and hydrogen bonding. The species distribution with pH at different compositions of SLS and plausible equilibria for the formation of species were also presented.

scholarly journals Kinetics and mechanism of the oxidation of some substituted aldonitrones by quinolinium chlorochromate in aqueous DMF medium in the absence and presence of oxalic acid

2009 ◽  
Vol 74 (2) ◽  
pp. 171-182 ◽  
Author(s):  
Govindasamy Rajarajan ◽  
Natesan Jayachandramani ◽  
Subramanian Manivarman ◽  
Jayaraman Jayabharathi ◽  
Venugopal Thanikachalam
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Oxalic Acid ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Experimental Conditions ◽  
First Order ◽  
Discernible Effect ◽  
Reactive Oxidant ◽  
Kinetics Of

The kinetics of the oxidation of aldonitrones (nitrone) by quinolinium chlorochromate (QCC) was determined in 50 % DMF-water in the absence and presence of oxalic acid in order to study the effect of oxalic acid. It was considered worthwhile to investigate whether it undergoes co-oxidation or just functions as a catalyst in the reaction. The reaction was followed iodometrically. Under the employed experimental conditions, the reaction is first order each with respect to concentration of nitrone, QCC, and oxalic acid and fractional order with respect to H+ concentration. There was no discernible effect with increasing in ionic strength but the rate of oxidation decreased with decreasing dielectric constant of the medium. Addition of MnSO4 had a significant and acrylonitrile no effect on the reaction rate. A mechanism involving protonated nitrone and QCC as the reactive oxidant is proposed. The activation parameters were calculated and are presented.

scholarly journals Protonation Equilibria of L-Aspartic, Citric and Succinic Acids in Anionic Micellar Media

2009 ◽  
Vol 6 (2) ◽  
pp. 561-568 ◽  
Author(s):  
P. Srinivasa Rao ◽  
B. Srikanth ◽  
V. Samba Siva Rao ◽  
C. Kamala Sastry ◽  
G. Nageswara Rao
Keyword(s):  
Citric Acid ◽  
Ionic Strength ◽  
Computer Program ◽  
Succinic Acid ◽  
Protonation Constants ◽  
Micellar Media ◽  
Statistical Parameters ◽  
Protonation Equilibria ◽  
The Impact ◽  
Best Fit

The impact of sodium lauryl sulphate (SLS) on the protonation equilibria ofL-aspartic acid, citric acid and succinic acid has been studied in various concentrations (0.5-2.5%w/v) of SLS solution maintaining an ionic strength of 0.16 mol dm-3at 303 K. The protonation constants have been calculated with the computer program MINIQUAD75 and the best fit models have been calculated based on statistical parameters. The trend of log values of step-wise protonation constants with mole fraction of the medium has been explained based on electrostatic and non-electrostatic forces operating on the protonation equilibria. The effects of errors on the protonation constants have also been presented.

scholarly journals The Effect of pH, Ionic Strength and the Presence of PbII on the Formation of Calcium Carbonate from Homogenous Alkaline Solutions at Room Temperature

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 783
Author(s):  
Fulvio Di Lorenzo ◽  
Kay Steiner ◽  
Sergey V. Churakov
Keyword(s):  
Ionic Strength ◽  
Deep Understanding ◽  
Inhibitory Effect ◽  
Alkaline Solutions ◽  
Nucleation Kinetics ◽  
Experimental Conditions ◽  
Calcium Carbonates ◽  
Natural Systems ◽  
Geological Processes ◽  
System Variables

Precipitation of calcium carbonates in aqueous systems is an important factor controlling various industrial, biological, and geological processes. In the first part of this study, the well-known titration approach introduced by Gebauer and coworkers in 2008 s used to obtain reliable experimental dataset for the deep understanding of CaCO3 nucleation kinetics in supersaturated solutions over a broad range of pH and ionic strength conditions. In the second part, the effect of impurities, i.e., 1 mol% of Pb2+, was assessed in the same range of experimental conditions. Divalent lead has been shown to have an inhibitory effect in all ranges of the conditions tested except for pH 8 and low ionic strength (≤0.15 mol/L). Future investigations might take advantage of the methodology and the data provided in this work to investigate the effect of other system variables. The investigation of all the major variables and the assessment of eventual synergic effects could improve our ability to predict the formation of CaCO3 in complex natural systems.

The diffusion of 75Se(IV) in Beishan granite – temperature, oxygen condition and ionic strength effects

2018 ◽  
Vol 107 (1) ◽  
pp. 39-54
Author(s):  
Chunli Wang ◽  
Xiaoyu Yang ◽  
Jiangang He ◽  
Fangxin Wei ◽  
Zhong Zheng ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Effective Diffusion ◽  
Aerobic Condition ◽  
Double Layers ◽  
Solution Viscosity ◽  
Formation Factor ◽  
Experimental Conditions ◽  
Beishan Granite ◽  
Oxygen Condition ◽  
The Difference

Abstract To explore the diffusion behavior of 75Se(IV) in Beishan granite (BsG), the influences of temperature, oxygen condition and ionic strength were investigated using the through-diffusion experimental method. The effective diffusion coefficient De of 75Se(IV) in BsG varied from 4.21×10−14 m2/s to 3.19×10−13 m2/s in our experimental conditions, increased with increasing temperature. The formation factor Ff of BsG was calculated to be nearly constant in the range of temperatures investigated, suggesting that the inner structure of BsG had no significant change in the temperature range of 20–55°C. Meanwhile, the De values of 75Se(IV) in BsG under anaerobic condition was significantly larger than that under aerobic condition, which may be attributed to the difference in the sorption characteristics and species distribution of Se and pH values. Moreover, the diffusion of 75Se(IV) was promoted with ionic strength increased from 0.01 M to 0.1 M, and then decreased at 0.5 M, mainly due to the combined effects of reduced double layers with increased ionic strength and increase of the solution viscosity at higher ionic strength.

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