Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion
Kompeksometrijsko određivanje - I. EDTA i kompleks sa Cu2+ jonom
Apstrakt
Compounds forming very stable complexes - chelates, have a wide field of application in analytical chemistry. The most famous group of these compounds are complexons. Complexons represent organic polyaminocarbonic acids as for example ethylenediaminetetraacetic acid (EDTA) and its salts. The EDTA molecule has six coordinative sites. It is a hexadentate ligands i.e. it has two binding nitrogen atoms and four oxygen atoms from carboxyl groups and it forms complexes with almost all metal ions. EDTA as a tetraprotonic acid, H4Y disociates through four steps, yielding the ions HsY-, H2Y2-, HY3- and Y4-. Which of the EDTA forms will be encountered in a solution, depends on the pH. Due to the poor solubility of EDTA in pure water, as well as in most organic solvents, the disodium salt of EDTA Na2H2Y-2H2O, under the commercial name complexon III, is utilized for analytical determinations. In water, EDTA forms soluble, stabile chelate complexes with all cations, at the molar ratio 1:1, regardle...ss of the charge of the metal ion. In contrast to other equilibria, which are mainly defined by Le Chatellier's principle, equilibria related to metal-EDTA complex formation are also dependent on the influence of the secondary equilibria of EDTA complex formation. Complexing reactions, which are equilibrium reactions, are simultaneously influenced by the following factors: solution pH and the presence of complexing agents which may also form a stabile complex with metal ions. The secondary reaction influence may be viewed and monitored through conditional stability constants. In the first part of the paper, the reaction of the formation of the Cu2+-ion complex with EDTA is analyzed beginning from the main reaction through various influences of secondary reactions on the complex Cu2+-EDTA: pH effect, complexation effect and hydrolysis effect. The equations are given for conditional stability constants, which include equilibrium reactions under actual conditions.
U prvom delu rada analizirana je reakcija stvaranja kompleksa Cu2+ jona sa etilen diamin tetra sirćetnom kiselinom (EDTA) počev od glavne reakcije preko različltih uticaja sporednih reakcija na kompleks Cu2+-EDTA: pH efekat, efekat kompleksiranja i efekat hidrolize. Dati su izrazi za uslovne konstante stabilnosti, koje definišu ravnotežne reakcije u realnim uslovima.
Ključne reči:
ethylenediaminetetraacetic acid - EDTA / chelate effect / complexing agent / conditional formation constant / Cu2+-ion / multidentate ligand / Etilendiamintetrasirćetna kiselina - EDTA / helatni efekat / kompleksirajući reagens / uslovna konstanta stabilnosti kompleksa / Cu2+-jon / polidentatni ligandIzvor:
Hemijska industrija, 2002, 56, 7-8, 338-345Izdavač:
- Savez hemijskih inženjera, Beograd
Institucija/grupa
Poljoprivredni fakultetTY - JOUR AU - Rajković, Miloš PY - 2002 UR - http://aspace.agrif.bg.ac.rs/handle/123456789/420 AB - Compounds forming very stable complexes - chelates, have a wide field of application in analytical chemistry. The most famous group of these compounds are complexons. Complexons represent organic polyaminocarbonic acids as for example ethylenediaminetetraacetic acid (EDTA) and its salts. The EDTA molecule has six coordinative sites. It is a hexadentate ligands i.e. it has two binding nitrogen atoms and four oxygen atoms from carboxyl groups and it forms complexes with almost all metal ions. EDTA as a tetraprotonic acid, H4Y disociates through four steps, yielding the ions HsY-, H2Y2-, HY3- and Y4-. Which of the EDTA forms will be encountered in a solution, depends on the pH. Due to the poor solubility of EDTA in pure water, as well as in most organic solvents, the disodium salt of EDTA Na2H2Y-2H2O, under the commercial name complexon III, is utilized for analytical determinations. In water, EDTA forms soluble, stabile chelate complexes with all cations, at the molar ratio 1:1, regardless of the charge of the metal ion. In contrast to other equilibria, which are mainly defined by Le Chatellier's principle, equilibria related to metal-EDTA complex formation are also dependent on the influence of the secondary equilibria of EDTA complex formation. Complexing reactions, which are equilibrium reactions, are simultaneously influenced by the following factors: solution pH and the presence of complexing agents which may also form a stabile complex with metal ions. The secondary reaction influence may be viewed and monitored through conditional stability constants. In the first part of the paper, the reaction of the formation of the Cu2+-ion complex with EDTA is analyzed beginning from the main reaction through various influences of secondary reactions on the complex Cu2+-EDTA: pH effect, complexation effect and hydrolysis effect. The equations are given for conditional stability constants, which include equilibrium reactions under actual conditions. AB - U prvom delu rada analizirana je reakcija stvaranja kompleksa Cu2+ jona sa etilen diamin tetra sirćetnom kiselinom (EDTA) počev od glavne reakcije preko različltih uticaja sporednih reakcija na kompleks Cu2+-EDTA: pH efekat, efekat kompleksiranja i efekat hidrolize. Dati su izrazi za uslovne konstante stabilnosti, koje definišu ravnotežne reakcije u realnim uslovima. PB - Savez hemijskih inženjera, Beograd T2 - Hemijska industrija T1 - Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion T1 - Kompeksometrijsko određivanje - I. EDTA i kompleks sa Cu2+ jonom EP - 345 IS - 7-8 SP - 338 VL - 56 DO - 10.2298/HEMIND0208338R ER -
@article{ author = "Rajković, Miloš", year = "2002", abstract = "Compounds forming very stable complexes - chelates, have a wide field of application in analytical chemistry. The most famous group of these compounds are complexons. Complexons represent organic polyaminocarbonic acids as for example ethylenediaminetetraacetic acid (EDTA) and its salts. The EDTA molecule has six coordinative sites. It is a hexadentate ligands i.e. it has two binding nitrogen atoms and four oxygen atoms from carboxyl groups and it forms complexes with almost all metal ions. EDTA as a tetraprotonic acid, H4Y disociates through four steps, yielding the ions HsY-, H2Y2-, HY3- and Y4-. Which of the EDTA forms will be encountered in a solution, depends on the pH. Due to the poor solubility of EDTA in pure water, as well as in most organic solvents, the disodium salt of EDTA Na2H2Y-2H2O, under the commercial name complexon III, is utilized for analytical determinations. In water, EDTA forms soluble, stabile chelate complexes with all cations, at the molar ratio 1:1, regardless of the charge of the metal ion. In contrast to other equilibria, which are mainly defined by Le Chatellier's principle, equilibria related to metal-EDTA complex formation are also dependent on the influence of the secondary equilibria of EDTA complex formation. Complexing reactions, which are equilibrium reactions, are simultaneously influenced by the following factors: solution pH and the presence of complexing agents which may also form a stabile complex with metal ions. The secondary reaction influence may be viewed and monitored through conditional stability constants. In the first part of the paper, the reaction of the formation of the Cu2+-ion complex with EDTA is analyzed beginning from the main reaction through various influences of secondary reactions on the complex Cu2+-EDTA: pH effect, complexation effect and hydrolysis effect. The equations are given for conditional stability constants, which include equilibrium reactions under actual conditions., U prvom delu rada analizirana je reakcija stvaranja kompleksa Cu2+ jona sa etilen diamin tetra sirćetnom kiselinom (EDTA) počev od glavne reakcije preko različltih uticaja sporednih reakcija na kompleks Cu2+-EDTA: pH efekat, efekat kompleksiranja i efekat hidrolize. Dati su izrazi za uslovne konstante stabilnosti, koje definišu ravnotežne reakcije u realnim uslovima.", publisher = "Savez hemijskih inženjera, Beograd", journal = "Hemijska industrija", title = "Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion, Kompeksometrijsko određivanje - I. EDTA i kompleks sa Cu2+ jonom", pages = "345-338", number = "7-8", volume = "56", doi = "10.2298/HEMIND0208338R" }
Rajković, M.. (2002). Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion. in Hemijska industrija Savez hemijskih inženjera, Beograd., 56(7-8), 338-345. https://doi.org/10.2298/HEMIND0208338R
Rajković M. Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion. in Hemijska industrija. 2002;56(7-8):338-345. doi:10.2298/HEMIND0208338R .
Rajković, Miloš, "Complexometric determination: Part I - EDTA and complex formation with the Cu2+ ion" in Hemijska industrija, 56, no. 7-8 (2002):338-345, https://doi.org/10.2298/HEMIND0208338R . .