The Kinetics of Chitosan Degradation in Organic Acid Solutions

This paper presents a comparative study on chitosan degradation in organic acid solutions according to their different dissociation characteristics. More precisely, the aim of the study was to determine the kinetics of the degradation process depending on the different acid dissociation constants (pKa values). The scientists involved in chitosan to date have focused mainly on acetic acid solutions. Solutions of lactic, acetic, malic, and formic acids in concentrations of 3% wt. were used in this research. The progress of degradation was determined based on the intrinsic viscosity measurement, GPC/SEC chromatographic analysis, and their correlation. Changes in the viscosity parameters were performed at a temperature of 20 °C ± 1 °C and a timeframe of up to 168 h (7 days). The chemical structure and DDA of the initial chitosan were analyzed using 1H-NMR spectroscopy analysis. The results of this study can be considered of high importance for the purpose of electrospinning, production of micro- and nano-capsules for drug delivery, and other types of processing. Understanding the influence of the dissociation constant of the solvent on the kinetics of chitosan degradation will allow the selection of an appropriate medium, ensuring an effective and stable spinning process, in which the occurrence of polymer degradation is unfavorable.

Physico-chemical properties of N-(2-Hydroxybenzoyl)-N'-(p-Tosil) Hydrazine

The results of a study of the physicochemical properties of N- (2-hydroxybenzoyl) -N '- (p-tosyl) hydrazine (GBSH) are presented. The solubility of the reagent in ethanol, 0.1 mol / L KOH solution, toluene, chloroform, hexane was studied by spectrophotometry, refractometry, and gravimetry. Based on the results obtained, it was shown that GBSG can be used in the processes of flotation and extraction. Acid-base equilibria in reagent solutions were studied spectrophotometrically. The obtained values of the acid dissociation constants (pKa1 = 7.93 ± 0.34; pKa2 = 10.48 ± 0.15) prove that GBSH is a weak diacid. The hydrolytic stability of the reagent was studied by the spectrophotometric method. The results of the study showed that HBHS solutions are sufficiently stable over time in alkaline media: the degree of hydrolysis within two hours is 2.35%. The surface activity of the reagent was determined by the stalagmometric method. It has been established that GBSG is a surfactant.