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Thermodynamic and detailed kinetic study of the formation of orthophthalaldehyde-agmatine complex by fluorescence intensities.

The aim of this work is to determine the thermodynamic parameters and the kinetics of complex formation between orthophthalaldehyde (OPA) and agmatine (AGM) in an alkaline medium (pH 13). Firstly, the association constant (Ka) between orthophthalaldehyde and agmatine was determined at different temperatures (between 298 K and 338 K) with a step size of 10 K. Secondly, the thermodynamic parameters such as standard enthalpy (?H°), standard entropy (?S°),and Gibbs energy (?G) were calculated, where a positive value of ?H° (+45.50 kJ/mol) was found, which shows that the reaction is endothermic. In addition, the low value of ?S°(+0.24 kJ/mol) indicates a slight increase in the disorder in the reaction medium. Furthermore, the negative values of ?G between ?35.62 kJ/mol and ?26.02 kJ/mol show that the complex formation process is spontaneous. Finally, the parameters of the kinetics of the reaction between OPA and AGM were determined as follows: when the initial concentration of AGM (5 × 10?6 M) is equal to that of the OPA, the results show that the reaction follows an overall 1.5 order kinetics with an initial rate of 5.1 × 10?7 Mmin?1 and a half-life of 8.12 min. The partial order found in relation to the AGM is 0.8. This work shows that the excess of OPA accelerates the formation reaction of the complex.

Auteur(s) : Khémesse Kital, Moumouny Traoré, Diégane Sarr, Moussa Mbaye, Mame Diabou Gaye Seye, Atanasse Coly, François Delattre & Alphonse Tine.
Année de publication : 2020
Revue : Journal of Analytical Science and Technology
N° de volume : 11(41)
Type : Article
Mise en ligne par : COLY Atanasse