Applying the least-squares method to determine the stability constants and molar extinction coefficients of complex compounds of the MA, MA2, ..., MAi types

1978 ◽  
Vol 14 (3) ◽  
pp. 330-332
Author(s):  
I. V. Khyarsing ◽  
Kh. Ya. Khyarsing ◽  
A. P. Filippov
Keyword(s):  
Least Squares ◽  
Stability Constants ◽  
Least Squares Method ◽  
Complex Compounds ◽  
Extinction Coefficients ◽  
The Stability ◽  
Molar Extinction Coefficients

Stability constants of three iron(III) salicylates

1970 ◽  
Vol 48 (16) ◽  
pp. 2574-2586 ◽  
Author(s):  
W. A. E. McBryde ◽  
Janet L. Rohr ◽  
J. S. Penciner ◽  
J. A. Page
Keyword(s):  
Stability Constants ◽  
Equilibrium Constants ◽  
Background Electrolyte ◽  
Aminosalicylic Acid ◽  
Sulfosalicylic Acid ◽  
Spectrophotometric Measurement ◽  
Acidity Constants ◽  
Extinction Coefficients ◽  
The Stability ◽  
Improved Methods

Stability constants of the iron(III) complexes of salicylic acid, sulfosalicylic acid, and 4-aminosalicylic acid, together with several of the acidity constants of these, have been determined at 25 °C and in solutions with 0.5 M background electrolyte. For the spectrophotometric measurement of the stability constants improved methods for determining the extinction coefficients of the first and second complexes are described. Protonated species appear only with the aminosalicylate complexes, and the site of this protonation is discussed. Previous values of these equilibrium constants have been collected and critically assessed.

scholarly journals Moving Least Squares Method for a One-Dimensional Parabolic Inverse Problem

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Baiyu Wang
Keyword(s):  
Inverse Problem ◽  
Least Squares ◽  
High Efficiency ◽  
Least Squares Method ◽  
Parabolic Problems ◽  
Moving Least Squares ◽  
One Dimensional ◽  
Moving Least Squares Method ◽  
The Stability

This paper investigates the numerical solution of a class of one-dimensional inverse parabolic problems using the moving least squares approximation; the inverse problem is the determination of an unknown source term depending on time. The collocation method is used for solving the equation; some numerical experiments are presented and discussed to illustrate the stability and high efficiency of the method.

scholarly journals STABILITY CONSTANTS OF L-ASPARAGINE AND L-LEUCINE COMPLEXES WITH SOME LANTHANIDE IN AQUEOUS SOLUTIONS AT 298.15 K

2017 ◽  
Vol 61 (1) ◽  
pp. 37
Author(s):  
Alexandr I. Lytkin ◽  
Natalya V. Chernyavskaya ◽  
Darya K. Smirnova
Keyword(s):  
Amino Acids ◽  
Aqueous Solutions ◽  
Stability Constants ◽  
Quantitative Estimation ◽  
A Priori ◽  
Complex Compounds ◽  
Complexing Agent ◽  
Stability Of Complexes ◽  
Biological Substrates ◽  
The Stability

Lanthanides have a high affinity toward ligands containing donor oxygen atoms, especially amino acids and complexons. The study of the processes of complexation of amino acids with f-element cations provides valuable information for solving problems of supramolecular chemistry, molecular recognition and chiral sensitivity of biological substrates. As a rule, f-elements are not components of biopolymers, but they are spectral label probes, which are important in the bioinorganic chemistry of metals. Quantitative estimation of the stability of complexes is necessary, first of all, to search for an internal connection between the constants themselves and then to find correlations between the stability of complexes and the properties of the complexing agent, the ligand, and the system as a whole. Such correlation dependencies make it possible to calculate a priori, or at least estimate the stability constants of new complexes, and also to better understand the influence of the nature of the chemical bond and the properties of the system as a whole on the formation and stability of complex compounds. In the present work, the complexation of neodymium, lanthanum with L-asparaginat ion and samarium, cerium with L-leucinat ion at 298.15 K and ionic strength values of 0.5 mol/l was studied by potentiometric titration and the stability constants of the complexes formed were determined. The values of the stability constants found allow us to perform rigorous thermodynamic calculations of the equilibria of these amino acids in salt solutions. The data obtained, in particular, can be used to reliably interpret the results of calorimetric studies of the complexation of lanthanides with the participation of the studied amino acids.Forcitation:Lytkin A.I., Chernyavskaya N.V., Smirnova D.K. Stability constants of L-asparagine and L-leucine complexes with some lanthanide in aqueous solutions at 298.15 K. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 1. P. 37-41

scholarly journals Equilibrium of aliphatic amino acids on ion exchangers forming complexes in the presence of copper (II) and nickel (II) cations

2019 ◽  
Vol 81 (3) ◽  
pp. 217-224
Author(s):  
L. P. Bondareva ◽  
Y. S. Peregudov ◽  
A. V. Astapov
Keyword(s):  
Amino Acids ◽  
Stability Constant ◽  
Stability Constants ◽  
Distribution Coefficients ◽  
Complex Compounds ◽  
Exchange Chromatography ◽  
Ion Exchanger ◽  
Ion Exchangers ◽  
Aliphatic Carboxylic Acid ◽  
The Stability

The task of isolating and separating amino acids from aqueous solutions exists in various industries. The traditional method of isolation is ligand exchange chromatography. When choosing a cation for ligand-binding chromatography based on its binding strength with the ion exchanger, often used as a sulfonated polystyrene ion exchanger keeps the copper (II) firmly enough, and therefore, it is easily replaced by other cations. Chelating ion exchangers charge cations of copper (II), which hold these ions firmly enough. In this case, separating a mixture of substances, it is due to differences in the constants of complexation agents and complexes distribution coefficients. The study of the interaction of amino acids with the aliphatic carboxylic acid, the exchange of phosphoric acid cations and the amino carboxylic and amino phosphonic polyampholytes has shown a significant effect of the pH of the medium on the nature of the sorption equilibria. Under certain conditions, in the phase of the ion exchanger in the form of complexing metal cations, the formation of new sorption centers is possible, which occur upon sorption of amino acids in the formation of mixed ligand compounds: the sorbent complex may simultaneously comprise amino acids and attached functional groups of the sorbent as ligands. The influence of the hydrogen index of the medium primarily affects the change in the nature of the formed complex compounds in the sorbent phase and the equilibrium solution and the ratio of their stability constants. If the stability constant of the ion exchanger complex is higher than the stability constant of the compound with a low molecular weight ligand, then the sorbed copper cations interact with incoming methionine ions without breaking the metal – functional group of the ion exchanger coordination bond. If the ratio of stability constants is the opposite, then the predominant elution of copper (II) cations occurs with the formation of complex compounds with an amino acid in an aqueous solution.

scholarly journals Interaction of Dioxovanadium (V) ion with L-alanine at Different Ionic Strengths

2009 ◽  
Vol 5 (1) ◽  
pp. 570-574
Author(s):  
Mohammad Hossein Fekri ◽  
F. Gharib ◽  
M. Darvishpour
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Stability Constants ◽  
Least Squares Method ◽  
Type Equation ◽  
Formation Constants ◽  
Amino Group ◽  
Fitting Method ◽  
The Stability ◽  
Curve Fitting Method

The formation constants of species formed in the system H+ + alanine and VO2+ +alanine have been determined in aqueous solution for 1.0<pH<7.0 and at different ionic strengths ranging from 0.1 to 1.0 mol dm-3 NaClO4, using a combination of potentiometric and spectrophotometric techniques.The compositions of the formd complexes and their stability constants were determined by curve fitting method and it was shown that dioxivanadium(V) forms two mononuclear 1:1 and 1:2 species with alanineof type VO2L and VO2L2-.The porotonation constant of the amino group of alanine has been determined using potentiometric techniques and calculated using a computer program wich employ a least-squares method. The dependence of the porotonation of alanine and the stability constants of the species on ionic strength are described by a deby-huckel type equation.

scholarly journals STUDY OF THE ALGORITHM OF PSEUDONORMAL OPTIMIZATION ON THE STABILITY OF THE SOLUTION OF THE EQUATION PROBLEM AND THE ESTIMATION OF THE ACCURACY

2021 ◽  
Vol 1 ◽  
pp. 40-48
Author(s):  
Amridon G. Barliani ◽  
Galina A. Nefedova ◽  
Irina V. Karnetova
Keyword(s):  
Least Squares ◽  
Least Squares Method ◽  
Experimental Studies ◽  
Network Models ◽  
Optimization Method ◽  
Equation Problem ◽  
Estimated Parameters ◽  
The Matrix ◽  
The Stability ◽  
Stability Of The Solution

In geodesic practice, when designing and adjusting geodetic networks for various purposes on a computer, it is necessary to solve poorly conditioned systems of linear normal equations. In such systems, the determinant of the matrix of equations tends to zero, so the application of the least squares method leads to large distortions of the estimated parameters. Moreover, in such situations, for the least squares algorithm, a slight distortion of the input data leads to unacceptably large distortions of the final results of the equalization and accuracy estimation. In this regard, the application of the pseudonormal optimization method is proposed. The presented work is devoted to the study of the stability of the solution of the adjustment task and the estimation of accuracy obtained on the basis of the pseudonormal optimization method. The novelty is the obtained algorithm for estimating the relative error of the pseudonormal optimization method. A comparative analysis of two competing processing methods was performed for different network models. The results of experimental studies and their analysis have shown the advantage of the pseudonormal optimization method over the least squares method.

Constraints on the determination of stability constants for metal complexes. II. The iron(III) phenolates

1968 ◽  
Vol 46 (14) ◽  
pp. 2385-2392 ◽  
Author(s):  
W. A. E. McBryde
Keyword(s):  
Metal Complexes ◽  
Stability Constants ◽  
Equilibrium Constants ◽  
Low Ph ◽  
Experimental Results ◽  
Good Precision ◽  
Acidity Constants ◽  
Extinction Coefficients ◽  
Molar Extinction Coefficients

Stability constants have been measured spectrophotometrically for the 1:1 complexes of iron(III) with phenol and five derivatives in background solutions having two different compositions, 0.027 M NaClO4 and 0 5 M KNO3 Conditional acidity constants for these phenols in the second of these media were also determined The experimental results were treated in two different ways to obtain values of the equilibrium constants and the molar extinction coefficients of the complexes It is apparent that the equilibrium in these cases must be studied under conditions, such as low pH and low concentration of iron, which militate against good precision in the results

scholarly journals COMPLEXATION OF PRAZIQUANTEL WITH α-, β- AND y-CYCLODEXTRINS IN AQUEOUS-ALCOHOLIC SOLUTIONS

2020 ◽  
Vol 17 (36) ◽  
pp. 302-314
Author(s):  
Nurgiza F IBRAKOVA ◽  
Galiya G KUTLUGILDINA ◽  
Yuriy S ZIMIN
Keyword(s):  
Stability Constants ◽  
Animal Husbandry ◽  
Complex Compounds ◽  
Molar Ratio ◽  
Ratio Method ◽  
Temperature Dependences ◽  
Medicinal Substances ◽  
The Stability ◽  
Increasing Temperature ◽  
Parasitic Worms

Currently, the percentage of infections with invasive (parasitic) diseases is quite large; therefore, the treatment of helminthiases is an urgent problem in veterinary medicine. Parasitic worms inflict significant damage on animal husbandry, leading to the death of animals, shortage of meat, dairy products, and wool. The most common active ingredient in antihelmintics is praziquantel, which is well known as an effective broad-spectrum anthelmintic. At the same time, praziquantel has low solubility in water and a pronounced bitter taste, which represents a significant obstacle in developing liquid forms of drugs that are convenient for administration to animals. One way to solve these problems is the complexation of medicinal substances with various (natural and synthetic) compounds. In this regard, this paper aims to study the complexation of praziquantel with α-, β-, and -cyclodextrins in aqueous-alcoholic solutions. The studies were carried out by the method of ultraviolet spectroscopy. It was found that the addition of cyclodextrins to aqueous-alcoholic solutions of praziquantel leads to spectral changes indicating the presence of intermolecular interactions and complexation. The isomolar series method showed that in dilute solutions, praziquantel forms complex compounds with cyclodextrins 1:1, that is, one molecule of praziquantel falls on one molecule of α-, β- or y-cyclodextrin. The stability constants of the resulting complexes were calculated using the molar ratio method. It is shown that in the range of 296-316 K, the composition of complex compounds remains unchanged (1:1), and their stability decreases with increasing temperature. The study of the temperature dependences of the stability constants made it possible to determine the standard values of changes in the Gibbs energy, enthalpy, and complexation entropy.

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