A novel method for the determination of the degree of deacetylation of chitosan by coulometric titration

Development of Chitosan Functionalized Magnetic Nanoparticles with Bioactive Compounds

In this study, magnetic maghemite nanoparticles, which belong to the group of metal oxides, were functionalized with chitosan, a non-toxic, hydrophilic, biocompatible, biodegradable biopolymer with anti-bacterial effects. This was done using different synthesis methods, and a comparison of the properties of the synthesized chitosan functionalized maghemite nanoparticles was conducted. Characterization was performed using scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). Characterizations of size distribution were performed using dynamic light scattering (DLS) measurements and laser granulometry. A chitosan functionalization layer was confirmed using potentiometric titration on variously synthesized chitosan functionalized maghemite nanoparticles, which is important for further immobilization of bioactive compounds. Furthermore, after activation of chitosan functionalized maghemite nanoparticles with glutaraldehyde (GA) or pentaethylenehexamine (PEHA), immobilization studies of enzyme cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) were conducted. Factors influencing the immobilization of enzymes, such as type and concentration of activating reagent, mass ratio between carrier and enzyme, immobilization time and enzyme concentration, were investigated. Briefly, microparticles made using the chitosan suspension cross-linking process (MC2) proved to be the most suitable for obtaining the highest activity of immobilized enzyme, and nanoparticles functionalized with chitosan using the covalent binding method (MC3) could compete with MC2 for their applications.

The determination of trace free acid content in lithium-ion battery electrolytes by coulometric titration in non-aqueous media

A new quantitative analysis method was proposed, aiming at resolving the difficulty encountered in accurately determining the trace content of a free acid in lithium-ion battery electrolytes in the past 30 years. The presented method overcame the three restrictive factors of lithium-ion battery electrolytes, namely, poor thermal stability, the formation of hydrofluoric acid with water and difficulty in the accurate determination of trace free acids. The free acid in lithium-ion battery electrolytes was directly titrated with ethoxide ions generated through the electrolyzation of a 0.50 mol L^-1 LiCl ethanol solution. The content of free acid was obtained according to the Faraday's law, and the whole determination process could be completed in 5 minutes. The relative standard deviation was below 2.0% when the content of free acid was 2.0 μg and above. The detection limit was 1.0 μg and the recovery rate was 99.5%-102.5%. In this method, free acid determination was not affected by temperature change and the existence of a small amount of water. Thus, this study provides a simple, fast and accurate analytical method with a lower detection limit for free acid in the lithium-ion battery industry and comprehensively improves the quality of lithium-ion battery electrolytes and the performance of lithium-ion battery products.

Accumulation of 2-Acetylamino-5-mercapto-1,3,4-thiadiazole in chitosan coatings for improved anticorrosive effect on zinc

Chitosan (Chit) coatings were applied on zinc substrates by the dip-coating method. Subsequently, the coatings were impregnated with a corrosion inhibitor, 2-Acetylamino-5-mercapto-1,3,4-thiadiazole (AcAMT) to obtain an increased anticorrosive effect. The coating thickness and the AcAMT accumulation were determined using UV-Vis spectroscopy on glass and quartz substrates, respectively. The surface morphology and coverage were investigated with atomic force microscopy. Electrochemical impedance spectroscopy and potentiodynamic polarization techniques were used to investigate the protective properties of the impregnated coatings. The chitosan coatings facilitated the accumulation of the corrosion inhibitor inside the polymeric matrix (a multiplication of 380 times compared to the impregnating solution concentration was calculated), channeling high amounts of AcAMT to the Zn surface, which resulted in an inhibition efficiency of >90%. This effect demonstrates the applicability of chitosan coatings as carriers for corrosion inhibitors, significantly reducing the amount of inhibitor needed to achieve good anticorrosive effects.

Determination of the Deacetylation Degree of Chitooligosaccharides

The methods for determination of chitosan content recommended in the Chinese Pharmacopoeia and the European Pharmacopoeia are not applicable for evaluation of the extent of deacetylation (deacetylation degree, DD) in chitooligosaccharides (COS). This study explores two different methods for assessment of DD in COS having relatively high and low molecular weights: an acid-base titration with bromocresol green indicator and a first order derivative UV spectrophotometric method for assessment of DD in COS. The accuracy of both methods as a function of molecular weight was also investigated and compared to results obtained using ¹H NMR spectroscopy. Our study demonstrates two simple, fast, widely adaptable, highly precise, accurate, and inexpensive methods for the effective determination of DD in COS, which have the potential for widespread commercial applications in developing country.

Removal of As(III) and As(V) from water by chitosan and chitosan derivatives: a review

As arsenic removal becomes a global concern, the development of removal processes for arsenic treatment is still a major challenge. With regard to environmental compatibility and cheapness, chitosan and chitosan derivatives are considered as a promising removal technology for arsenic. Chitosan and chitosan derivatives possess the properties of low cost and good sorption on the arsenic removal. The present review is concerned about the present understanding of the mechanisms involved in sorption processes. Further on, detailed discussions are given of the effects of various factors on the performance of chitosan and chitosan derivatives in arsenic treatment processes. Finally, special attention is paid to the future challenges of chitosan and chitosan derivatives utilized for industrial arsenic treatment.