Trace Elements in Medicine (Moscow)
2017, 18(3): 25–29
ORIGINAL PAPER

STUDY OF KINETICS OF THE PECTIN INTERACTION WITH Mg2+, Cu2+, Fe2+ SALTS

N.Sh. Kajsheva, A.Sh. Kajshev

Pyatigorsk Medico-Pharmaceutical Institute, Kalinin ave., 11, Pyatigorsk, 357532, Russia

DOI: 10.19112/2413-6174-2017-18-3-25-29 

ABSTRACT. The kinetic characteristics of reactions of beet pectin interaction with Mg2+ sulfate, Cu2+ acetate, Fe2+ ammonium sulfate were studied. The particular order of the reaction was defined by metal ions and the reaction rate constant was defined by the determination at different times of the concentration of Mg2+ and Cu2+ by complexometry with sodium edetate, Fe2+ – by photometry using the reaction with sulfosalicylic acid. By identifying the graphic system, in which a rectilinear relationship between the duration of the reaction and the concentration of a metal ion was observed, there were calculated the kinetic characteristics using integration method. The values obtained were confirmed by Vant-Hoff differential method in graphical form. Both methods revealed that the reaction of the pectin with Mg2+ or Cu2+ is a first-order reaction (described by equation lgCM = f(t)), reaction with Fe2+ is a second-order reaction (described by equation t = f(1/CM)). It shows different mechanisms and the complexity of the processes of in-teraction, especially with Fe2+. The calculated reaction rate constants of the interaction of pectin with Cu2+ (6.5 hour1), Fe2+ (4.0 hour1), Mg2+ (1.3 hour1) showed that the reaction with Cu2+, compared to Mg2+ and Fe2+, occurs in 1.6 and 5 times faster, respectively. Perhaps it was because of the difference in the electronic configuration of the metal cations, their degree of hydration and the polarizing action, the strength of bonds formed. The relative error in the determination did not exceed ± 4.9%. Thus, Cu2+ ions, unlike ions of biogenic metals (Mg2+, Fe2+), are preferentially bound by pectins when they are introduced into biological fluids, which, if the level of biogenic metals is maintained, will almost com-pletely bind Cu2+ ions with pectin.

KEYWORDS: pectins, metal (II) ions, kinetic characteristics, order of reaction, reaction rate constant.