Discontinuous spectrocolorimetric titration method for determining stability constants of fulvic acid - iron complexes

Soil Research ◽  
1997 ◽  
Vol 35 (6) ◽  
pp. 1279 ◽  
Author(s):  
S. B. Pandeya ◽  
A. K. Singh
Keyword(s):  
Stability Constant ◽  
Stability Constants ◽  
Aqueous Media ◽  
Poultry Manure ◽  
Fulvic Acids ◽  
Titration Method ◽  
Binding Ability ◽  
Press Mud ◽  
Determining Factors ◽  
The Stability

The stability constants for the complexes formed between iron species existing in ambient soil environment and fulvic acids (FA) extracted from organic wastes like sewage sludge, farm yard manure (FYM), poultry manure, and press mud were determined in aqueous media of pH 5·0 and 8·5 by discontinuous spectrocolorimetric titration method. The values of stability constant (log K) of Fe–FA complexes estimated at pH 5·0 were 6·026, 6·212, 6·270, and 6·342 for FYM, sludge, poultry manure, and press mud, respectively. The respective values at pH 8·5 were 6·145, 6·276, 6·350, and 6·940. The order of the values of log K for different preparations of fulvic acids was press mud > poultry manure > sludge > FYM. The functional group contents, their pH of neutralisation, and electrostatic properties of the FA such as pKINT, pKm, and 0·868 nW, were found to be the determining factors for maximum binding ability of FA for metal cations and the stability constant of Fe–FA for different FA preparations. The basic assumptions and the limitations of the discontinuous spectrocolorimetric estimation of stability constants for Fe–FA are discussed.

SODIUM CHELATES OF ETHYLENEDIAMINETETRAACETIC ACID

1963 ◽  
Vol 41 (1) ◽  
pp. 18-20 ◽  
Author(s):  
Vladimir Palaty
Keyword(s):  
Stability Constant ◽  
Stability Constants ◽  
Ethylenediaminetetraacetic Acid ◽  
Glass Electrode ◽  
Neutral Solution ◽  
Experimental Conditions ◽  
The Stability ◽  
Sensitive Method

The stability constant of the sodium chelate of EDTA was determined by means of a sodium-sensitive glass electrode. It appears that a hydrogen chelate of the formula NaHY2− is formed in the neutral solution of EDTA, but is very unstable. The stability constants, pKNaY = −2.61 and pKNaHY = 0.03, are comparable to the value obtained by Schwarzenbach and Ackermann under different experimental conditions by a less sensitive method.

Transferrin binding of Al3+ and Fe3+.

1987 ◽  
Vol 33 (3) ◽  
pp. 405-407 ◽  
Author(s):  
R B Martin ◽  
J Savory ◽  
S Brown ◽  
R L Bertholf ◽  
M R Wills
Keyword(s):  
Stability Constant ◽  
Blood Plasma ◽  
Stability Constants ◽  
Metal Ion ◽  
Equilibrium Dialysis ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Quantitative Studies ◽  
Intensity Changes ◽  
The Stability

Abstract An understanding of Al3+-induced diseases requires identification of the blood carrier of Al3+ to the tissues where Al3+ exerts a toxic action. Quantitative studies demonstrate that the protein transferrin (iron-free) is the strongest Al3+ binder in blood plasma. Under plasma conditions of pH 7.4 and [HCO3-]27 mmol/L, the successive stability constant values for Al3+ binding to transferrin are log K1 = 12.9 and log K2 = 12.3. When the concentration of total Al3+ in plasma is 1 mumol/L, the free Al3+ concentration permitted by transferrin is 10(-14.6) mol/L, less than that allowed by insoluble Al(OH)3, by Al(OH)2H2PO4, or by complexing with citrate. Thus transferrin is the ultimate carrier of Al3+ in the blood. We also used intensity changes produced by metal ion binding to determine the stability constants for Fe3+ binding to transferrin: log K1 = 22.7 and log K2 = 22.1. These constants agree closely with a revision of the reported values obtained by equilibrium dialysis. By comparison with Fe3+ binding, the Al3+ stability constants are weaker than expected; this suggests that the significantly smaller Al3+ ions cannot coordinate to all the transferrin donor atoms available to Fe3+.

103Rh-NMR-Untersuchungen an Chloro-Bromo-Rhodaten(III) und Bestimmung der Stabilitätskonstanten im System [RhClnBr6-n]3-, n = 0-6 / 103Rh NMR Studies of Chloro-Bromo-Rhodates(III) and Determination of the Stability Constants in the System [RhCl„Br6-n]3-, n = 0-6

1989 ◽  
Vol 44 (11) ◽  
pp. 1402-1406 ◽  
Author(s):  
W. Kuhr ◽  
G. Peters ◽  
W. Preetz
Keyword(s):  
Nmr Spectroscopy ◽  
High Resolution ◽  
Stability Constant ◽  
Stability Constants ◽  
Trans Isomers ◽  
Nmr Studies ◽  
Downfield Shift ◽  
Overall Stability ◽  
The Stability

By 103Rh NMR spectroscopy the ten compounds of the system [RhCl„Br6_„]3-, n = 0-6 are identified by separate signals. A downfield shift of approximately 160 ppm is observed per substitution of Cl by Br, and the stereoisomers for n = 2, 3, 4 are separated by at least 4 ppm. From the relative intensities of the 103Rh signals in equilibrated solutions, whose total contents of Rh. Cl and Br are known, six individual stability constants are calculated. Their product gives the overall stability constant, indicating [RhBr6]3- to be 36,300 times more stable than [RhCl6]3-. On treatment of [RhBr6]3- with HCl cis/fac isomers are formed stereospecifically, whereas the reaction of [RhCl6]3- with HBr gives trans isomers, n = 2 and 4, containing 20—30% of the cis compounds; only mer-[RhCl3Br3] 3- is obtained pure. The high resolution spectra of [RhCl6]3- and [RhBr6]3- are exhibit five signals each, reflecting the intensity patterns of the most abundant isotopomers within [Rh35Cln37Cl6-n]3-, n = 2-6, and [Rh79Br„81Br6_„]3-, n = 1-5, respectively.

Europium tartronate and mandelate ion association in water

1967 ◽  
Vol 45 (14) ◽  
pp. 1643-1647 ◽  
Author(s):  
P. G. Manning
Keyword(s):  
Ionic Strength ◽  
Solvent Extraction ◽  
Stability Constant ◽  
Stability Constants ◽  
Ion Association ◽  
Tridentate Ligand ◽  
Radiotracer Method ◽  
The Stability ◽  
Two Stages ◽  
Low Ionic Strength

Stepwise stability constants have been determined for the 1:1 and 1:2 Eu3+:mandelate− and Eu3+:tartronate2− complexes in water. Measurements were made at low ionic strength and the temperature was 25 °C. The solvent-extraction–radiotracer method was used.For the mandelate system at an ionic strength of 0.104, K1 = 5.0 × 102, K2 = 1.58 × 102, and K1:K2 = 3.1. The K1:K2 ratios suggest monodentate ligandcy.The stepwise stability constants for the two stages of tartronate ion association are: K1 = 7.1 ( ± 15%) × 104 and K1K2 = 4.2 ( ± 5%) × 108. The magnitudes of the stability constants suggest that tartronate is a tridentate ligand. The stability constant ratios are discussed with reference to the ratios for piperidinedicarboxylate and iminodiacetate complexes.

Study of nitrate complex formation with trivalent Pm, Eu, Am and Cm using a solvent extraction technique

2004 ◽  
Vol 92 (12) ◽  
Author(s):  
Sofie Andersson ◽  
C. Ekberg ◽  
J-O. Liljenzin ◽  
M. Nilsson ◽  
G. Skarnemark
Keyword(s):  
Solvent Extraction ◽  
Complex Formation ◽  
Nuclear Fuel ◽  
Stability Constants ◽  
Spent Nuclear Fuel ◽  
Aqueous Media ◽  
Separation Process ◽  
Nitrate Complex ◽  
The Stability ◽  
Solvent Extraction Technique

SummaryThe separation of actinides and lanthanides is an important question in the treatment of spent nuclear fuel in the transmutation concept. To find an efficient and well functioning separation process it is necessary to study the chemistry of the elements in the two groups in different aqueous media. The stability constants of the nitrate complex formation with Pm, Eu, Am and Cm were determined using solvent extraction. The extraction was studied using the synergistic system of 2,6-bis-(benzoxazolyl)-4-dodecyloxylpyridine and 2-bromodecanoic acid in

scholarly journals Copper(II) and lead(II) complexation by humic acid and humic-like ligands

2011 ◽  
Vol 76 (9) ◽  
pp. 1325-1336 ◽  
Author(s):  
Ivana Kostic ◽  
Tatjana Andjelkovic ◽  
Ruzica Nikolic ◽  
Aleksandar Bojic ◽  
Milovan Purenovic ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Humic Acid ◽  
Stability Constants ◽  
Comparative Investigation ◽  
Binding Ability ◽  
Exchange Method ◽  
Mononuclear Complexes ◽  
Ion Exchange Method ◽  
The Stability

The stability of metal-humate complexes is an important factor determining and predicting speciation, mobility and bioavailability of heavy metals in the environment. A comparative investigation of the complexation of Cu(II) and Pb(II) with humic acid and humic-like ligands, such as benzoic and salicylic acid, was performed. The analysis was realized at pH 4.0, a temperature of 25?C and at an ionic strength of 0.01 (NaCl) using the Schubert ion-exchange method and its modified form. The stability constants were calculated from the experimental data by the Schubert method for complexes with benzoic and humic acid. A modified Schubert method was used for the determination of the stability constants of the complexes with salicylic acid. It was found that Cu(II) and Pb(II) form mononuclear complexes with benzoic and humic acid while with salicylic acid both metals form polynuclear complexes. The results indicate that Pb(II) has a higher binding ability than Cu(II) to all the investigated ligands. The Cu(II)-salicylate and Pb(II)-salicylate complexes showed noticeable higher stability constants compared with their complexes with humic acid, while the stabilities of the complexes with benzoic acid differed less. Salicylic and benzoic acids as humic-like ligands can be used for setting the range of stability constants of humic complexes with Cu(II) and Pb(II).

scholarly journals Electrochemical Studies on Speciation of Cadmium(II) in ppb Level by Complexation with Ethylenediamine in Aqueous Media

1970 ◽  
Vol 44 (1) ◽  
pp. 1-10
Author(s):  
Nurun Nahar ◽  
Anshaya Ramim ◽  
M Nurul Abser
Keyword(s):  
Stability Constants ◽  
Anodic Stripping Voltammetry ◽  
Aqueous Media ◽  
Stripping Voltammetry ◽  
Differential Pulse ◽  
Exchange Equilibrium ◽  
Experimental Conditions ◽  
Mercury Film ◽  
Competitive Ligand Exchange ◽  
The Stability

The speciation of cadmium(II) in ppb level by complexation with ethylenediamine (EN) has been investigated by differential pulse anodic stripping voltammetry (DPASV) using thin mercury film coated glassy carbon electrode (TMFGCE). The overall work has been carried out at constant ionic strength of 0.01 mol dm-3 (NaNO3) at ambient temperature. The pH was kept constant at 8.81 ± 0.10 by the addition of borate buffer. The stability constants of different species of cadmium(II) with ethylenediamine have been calculated from the variation of peak potential and diffusion current of simple and complexed metal ions under the present experimental conditions. The logarithmic values of overall stability constants: log β1, log β2 and log β3 (βi = [CdLi]/[Cd2+][L]i where i = 1, 2 and 3) have been found to be 5.01, 8.9 and 11.1 for CdL, CdL2 and CdL3, respectively (charges were omitted for simplicity). The stability constants of cadmium complexes and hydrolysis constants of cadmium indicate that five different species of cadmium (Cd2+, CdOH+, CdL, CdL2 and CdL3) co-exist at ligand concentrations up to 5×10-4 mole dm-3 under the present experimental conditions. The results obtained by this method is applied to study the cadmium speciation in river water on the basis of competitive ligand exchange equilibrium. Key words: Speciation, Complexation, Aqueous media, DPASV, Mercury film electrode.   doi: 10.3329/bjsir.v44i1.2709 Bangladesh J. Sci. Ind. Res. 44(1), 1-10, 2009

scholarly journals In vitro Study on Interaction of Ketotifen Fumerate with Paracetamol

IIUC Studies ◽  
2012 ◽  
Vol 7 ◽  
pp. 49-54
Author(s):  
Mohammed Aktar Sayeed ◽  
Sohel Rana
Keyword(s):  
Stability Constants ◽  
Aqueous Media ◽  
In Vitro Study ◽  
Vitro Study ◽  
Reaction Systems ◽  
The Stability

Interaction of ketotifen fumerate and paracetamol was studied in aqueous media. The ability of interaction of ketotifen with paracetamol is dependent on pH of the solution and it has been found that ketotifen forms 1:1 complexes at different pH. The stability constants have been calculated from the Ardon’s spectrophotomeric measurements of the reaction systems. When ketotifen was interacted with paracetamol and the absorbance was determined at 300 nm the stability constants were found of - 7.32 and -7.84 at pH 1.6 and 7.4 respectively. DOI: http://dx.doi.org/10.3329/iiucs.v7i0.12258 IIUC Studies Vol.7 2011: 49-54

scholarly journals In vitro study on the interaction of ketotifen fumarate with anhydrous theophylline

2012 ◽  
Vol 48 (2) ◽  
pp. 211-216
Author(s):  
Mohammed Aktar Sayeed ◽  
Razibul Habib ◽  
Mominur Rahman ◽  
Hasan Al Banna ◽  
Sohel Rana
Keyword(s):  
Stability Constants ◽  
Aqueous Media ◽  
In Vitro Study ◽  
Stable Complex ◽  
Concurrent Administration ◽  
Fixed Temperature ◽  
Ketotifen Fumarate ◽  
The Stability ◽  
Anhydrous Theophylline

The purpose of the present study was to investigate the interaction between ketotifen fumarate and anhydrous theophylline in aqueous media of various pH (1.2 and 6.8). Using Job's continuous-variation analysis and Ardon's spectrophotomeric measurement methods, the values of the stability constants of theophylline with ketotifen were determined at a fixed temperature (37 ºC) at various pH. The stability constants, ranging between 5.66 and 9.92, were derived from Ardon's plot, indicating that comparatively stable complexes had formed as a result of an interaction between the drugs. However, following the interaction of theophylline with ketotifen, stability constants were <1 at gastric pH (1.2) and intestinal pH (6.8). Concurrent administration of ketotifen and theophylline could result in the formation of a stable complex and this is likely to reduce the therapeutic activities of both drugs.

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