scholarly journals Investigation of the Interaction of Gadolinium with Several Organic Ligands and Humic Acid by Ligand Competition Using 4-(2-Pyridylazo)-Resorcinol (PAR)

Environments ◽  
2020 ◽  
Vol 7 (9) ◽  
pp. 69
Author(s):  
Spencer Steinberg ◽  
Vernon Hodge ◽  
Luis Becerra-Hernandez
Keyword(s):  
Humic Acid ◽  
Organic Acids ◽  
Stability Constants ◽  
Reasonable Agreement ◽  
Organic Ligands ◽  
Competitive Displacement ◽  
Colored Complex ◽  
Method Of Continuous Variation ◽  
The Stability ◽  
Displacement Approach

Gd3+ forms a strongly colored complex with 4-(2-pyridylazo)-resorcinol (PAR) in aqueous solutions. We characterized the Gd3+-PAR complex in order to use it as a probe of Gd3+ speciation in the presence of environmentally relevant ligands. The formation of the Gd3+-PAR complex was investigated from pH 5 to 8 in the presence of excess PAR. The absorbance of the Gd3+-PAR complex dramatically increased from pH 5 to 8 and application of the method of continuous variation indicates that the complex was primarily 1:2 Gd(PAR)2 at pH 8. Stability constants for Gd3+ with other ligands can be quantified by competitive displacement of the PAR ligand. To establish the viability of this approach, we measured the stability constants between Gd3+ and several organic acids and carbonate. Our measurements show reasonable agreement with the literature values. We used the competitive displacement approach to establish that humic acids can competitively displace PAR from the Gd(PAR)2 complex.

Studies of metal–organic interactions in model systems pertaining to natural waters

1976 ◽  
Vol 54 (16) ◽  
pp. 2600-2611 ◽  
Author(s):  
Robert D. Guy ◽  
C. L. Chakrabarti
Keyword(s):  
Humic Acid ◽  
Organic Acids ◽  
Stability Constants ◽  
Tannic Acid ◽  
Natural Waters ◽  
Model Systems ◽  
Organic Complexes ◽  
Metal Organic ◽  
Acid Release ◽  
The Stability

The interactions of Cu(II), Pb(II), Cd(II), and Zn(II) with humic and tannic acids were studied to evaluate the possibility of metal speciation using a combination of dialysis/atomic absorption spectroscopy, and the pH characteristics of the metal–organic species. The stability constants of metal–organic complexes were found to decrease in the order Pb(II) > Cu(II) > Cd(II) > Zn(II) and EDTA > humic acid > tannic acid. Scatchard plots for the metal–humic acid systems indicated two types of binding sites with a difference in stability constants of about 10. Ultrafiltration of metal–humic acid solutions indicated that the metal ions were concentrated in the large molecular size fractions (> 3.1 nm). Separation by dialysis was used to investigate the release of metal from model sediment components by the organic acids (the metal–organic complexes were non-dialyzable). For release of copper from bentonite, it was found that the amount of copper released depended on both the concentration of ligand and the stability constant of metal complex, with the ratio of metal release to complexing sites decreasing in the order EDTA > humic acid > tannic acid. Release of metal from the solids decreased in the order: bentonite > MnO2 > humic acid. Release of metal from the hydrous oxides via a redox decomposition of the oxide by natural organics was investigated using pyrogallol, gallic, and tannic acids. At natural water pH levels (6–8), 20 μg/ml solutions of the organic acids released 20 μmol manganese per 100 ml solutions whereas at pH 2, 60 μmol manganese were released. The pH behaviour of the organic acids has been explained in terms of formation of oxalic acid at pH &([a-z]+); 5, which then reduces the hydrous oxide.

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 Comparative study of binding strengths of heavy metals with humic acid

2013 ◽  
Vol 67 (5) ◽  
pp. 773-779 ◽  
Author(s):  
Ivana Kostic ◽  
Tatjana Andjelkovic ◽  
Ruzica Nikolic ◽  
Tatjana Cvetkovic ◽  
Dusica Pavlovic ◽  
...  
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Humic Acid ◽  
Metal Ions ◽  
Stability Constants ◽  
Metal Ion ◽  
Heavy Metal Ions ◽  
Exchange Method ◽  
Divalent Metal Ion ◽  
The Stability

The complexation of humic acid with certain heavy metal ions (Co(II), Ni(II), Cu(II), Zn(II) and Pb(II)) was investigated. The stability constants of humate complexes were determined by method which is based on distribution of metal ions between solution and resin in the presence and the absence of ligand, known as Schubert?s ion exchange method. Experiments were performed at 25 ?C, at pH 4.0 and ionic strength of 0.01 mol dm-3. It was found that the 1:1 complexes were formed between metal ions and humic acid. Obtained results of the stability constants, log ?mn, of complexes formed between the metal ions and humic acid follow the order Co(II) < Ni(II) < Cu(II) > Zn(II) which is the same like in the Irving-Williams series for the binding strength of divalent metal ion complexes. Stability constant of complex between Pb(II) ions and humic acid is greater than stability constants of other investigated metal-humate complexes. The investigation of interaction between heavy metal ions and humics is important for the prediction of the distribution and control of the migration of heavy metals in natural environment.

Synthesis of some salicylic acid derivatives and studies of their interaction with uranyl ion

1991 ◽  
Vol 56 (7) ◽  
pp. 1446-1453 ◽  
Author(s):  
Evgenija A. Djurendić ◽  
Terézia M. Surányi ◽  
Dušan A. Miljković
Keyword(s):  
Salicylic Acid ◽  
Stability Constants ◽  
Aqueous Ethanol ◽  
Continuous Variation ◽  
Acidity Constants ◽  
Stability Constants Of Complexes ◽  
Salicylic Acid Derivatives ◽  
Method Of Continuous Variation ◽  
The Stability ◽  
Derivatives Of

Some unsubstituted and substituted bis-derivatives of salicylic acid have been synthesized and their acidity constants determined spectrophotometrically in 61.10% aqueous ethanol. The stability constants of complexes these compounds from with UO22+-ion were determined spectrophotometrically using the method of continuous variation under following conditions: pH 3.58 and 3.98, 61.10% aqueous ethanol, μ = 0.5 (LiCl), 25 ± 1 °C.

Polarographic determination of the stability constants of binary and ternary lead(II) complexes and different organic ligands

1985 ◽  
Vol 196 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Ramon J.Barrio Diez-Caballero ◽  
Juan F.Arranz Valentin ◽  
Adela Arranz Garcia ◽  
Rafael Pardo Almudi ◽  
Pedro Sanchez Batanero
Keyword(s):  
Stability Constants ◽  
Organic Ligands ◽  
Polarographic Determination ◽  
The Stability

Changes in the Humic Acid–Metal Complexation Characteristics Depending on Humification Degree / Humīnskābju – Metālu Kompleksveidošanās Rakstura Izmaiņas Atkarībā No Humifikācijas Pakāpes

2012 ◽  
Vol 51 (3) ◽  
pp. 228-237
Author(s):  
D. Dudare ◽  
M. Klavins
Keyword(s):  
Humic Acid ◽  
Stability Constants ◽  
Humic Acids ◽  
Complex Stability ◽  
Peat Layer ◽  
Raised Bog ◽  
Complexing Capacity ◽  
Humification Degree ◽  
Complexation Process ◽  
Complex Stability Constants

The aim of this study is to determine the Cu(II) complexing capacity and stability constants of Cu(II) complexes of humic acids isolated from two well-characterized raised bog peat profiles in respect to the basic properties and humification characteristics of the studied peats and their humic acids. The complex stability constants significantly change within the studied bog profiles and are well correlated with the age and decomposition degree of the peat layer from which the humic acids have been isolated. Among factors that influence this complexation process, molecular mass and ability to form micellar structures (supramolecules) of humic substances are of key importance.

Extractive Spectrophotometric Method for the Determination of Glibenclamide by Ion-Pair Complex in Pure Form and Pharmaceutical Formulation

2019 ◽  
Vol 9 (o3) ◽  
Author(s):  
RUAA MUAYAD MAHMOOD ◽  
HAMSA MUNAM YASSEN ◽  
SAMAR , NAJWA ISSAC ABDULLA AHMED DARWEESH ◽  
NAJWA ISSAC ABDULLA
Keyword(s):  
Spectrophotometric Method ◽  
Molar Absorptivity ◽  
Ion Pair ◽  
Pharmaceutical Formulation ◽  
Ratio Method ◽  
Colored Complex ◽  
Colored Product ◽  
Method Of Continuous Variation ◽  
Job's Method

Simple, rapid and sensitive extractive spectrophotometric method is presented for the determination of glibenclamide (Glb) based on the formation of ion-pair complex between the Glb and anionic dye, methyl orange (MO) at pH 4. The yellow colored complex formed was quantitatively extracted into dichloromethane and measured at 426 nm. The colored product obeyed Beer’s law in the concentration range of (0.5-40) μg.ml-1. The value of molar absorptivity obtained from Beer’s data was found to be 31122 L.mol-1.cm-1, Sandell’s sensitivity value was calculated to be 0.0159 μg.cm-2, while the limits of detection (LOD) and quantification (LOQ) were found to be 0.1086 and 0.3292 μg.ml-1, respectively. The stoichiometry of the complex created between the Glb and MO was 1:1 as determined via Job’s method of continuous variation and mole ratio method. The method was successfully applied for the analysis of pharmaceutical formulation.

Extraction of strontium and barium salts by the nitrobenzene solution of dicarbolide in the presence of glymes

1985 ◽  
Vol 50 (3) ◽  
pp. 581-599 ◽  
Author(s):  
Petr Vaňura ◽  
Emanuel Makrlík
Keyword(s):  
Stability Constants ◽  
Organic Phase ◽  
Equilibrium Constants ◽  
Minor Role ◽  
Nitrobenzene Solution ◽  
Ligand Structure ◽  
Stability Constants Of Complexes ◽  
Separation Factors ◽  
The Stability ◽  
A Minor

Extraction of microamounts of Sr2+ and Ba2+ (henceforth M2+) from the aqueous solutions of perchloric acid (0.0125-1.02 mol/l) by means of the nitrobenzene solutions of dicarbolide (0.004-0.05 mol/l of H+{Co(C2B9H11)2}-) was studied in the presence of monoglyme (only Ba2+), diglyme, triglyme, and tetraglyme (CH3O-(CH2-CH2O)nCH3, where n = 1, 2, 3, 4). The distribution of glyme betweeen the aqueous and organic phases, the extraction of the protonized glyme molecule HL+ together with the extraction of M2+ ion and of the glyme complex with the M2+ ion, i.e., ML2+ (where L is the molecule of glyme), were found to be the dominating reactions in the systems under study. In the systems with tri- and tetraglymes the extraction of H+ and M2+ ions solvated with two glyme molecules, i.e., the formation of HL2+ and ML22+ species, can probably play a minor role. The values of the respective equilibrium constants, of the stability constants of complexes formed in the organic phase, and the theoretical separation factors αBa/Sr were determined. The effect of the ligand structure on the values of extraction and stability constants in the organic phase is discussed.

Studies on the Coordination Reaction of VO2+ and Tannic Acid in the Tannin Extract Desulfurization

2012 ◽  
Vol 239-240 ◽  
pp. 1573-1576
Author(s):  
Zhu Qing Gao ◽  
Xiao Dong Cai ◽  
Kai Cheng Ling
Keyword(s):  
Stability Constants ◽  
Tannic Acid ◽  
Ph Value ◽  
Protonation Constants ◽  
Conditional Stability ◽  
Tannin Extract ◽  
Acid Effect ◽  
Different Temperatures ◽  
The Stability ◽  
Apparent Stability

At different temperatures, the protonation constants of tannic acid and the complex apparent stability constants between tannic acid and VO2+ were determined by using pH potentimetric method. The results showed that the protonation constants and the complex apparent stability constants slightly decreased with the raising temperature. In accordance with the pH value in the tannin extract technology, the conditional stability constants of the complex were calculated on the basis of the acid effect of tannic acid and the hydrolysis effect of VO2+. It was found that pH greatly affected the stability constants of the complex , so pH must be strictly controlled in the tannin extract technology.

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