Search

The purpose of the work is to establish the possibility of obtaining expanded graphite of high purity (carbon content more than 99.5 % wt.) from flotation-enriched graphite (carbon content 94–97 % wt.) by combining into one process intercalation of graphite with a solution of potassium dichromate in concentrated sulfuric acid with subsequent hydrolysis, and chemical purification using solutions of ammonium bifluoride in sulfuric or hydrochloric acid and Trilon B in an alkaline buffer as purification reagents, and to confirm this possibility by quantum chemical calculations. It has been experimentally shown that combining oxidized graphite synthesis and its chemical purification into one process allows obtaining expanded graphite of high purity, with a carbon content of 99.75–99.85 % wt. The methods of X-ray diffraction and thermogravimetry show that the interaction of oxidized graphite (the residual compound of intercalation of graphite with sulfuric acid) with cleaning reagents does not reduce the ability to expand. The magnitude of the mass loss of oxidized graphite according to various variants of chemical post-cleaning and the temperature range of such loss remain practically unchanged. Quantum chemical calculations of the adsorption energy (∆Eads) of one molecule of Trilon B on the surface of a graphene-like plane (GLP), the complexation reaction of metal sulfates, the energy effect of the interaction of Trilon B with sulfates of alkaline earth metals in an aqueous solution, and with the participation of the surface of the graphene plane were carried out using the GAMESS (US) program by the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d,p) basis set, taking into account the Grimme D3 dispersion correction within the PCM polarizable continuum. The results of the analysis of quantum chemical calculations indicate that the Trilon B molecule is better physically sorbed on the oxidized GLP (–412 kJ/mol) than on its native form (–188 kJ/mol). The values of the energy effect of the complexation of magnesium and calcium cations with Trilon B have a negative value both in an aqueous solution and in the presence of the oxidized form of GLP. This indicates the thermodynamic probability of this process, which is consistent with the experimental results. Regardless of the nature of the cation, its interaction with Trilon B is thermodynamically more likely in an aqueous solution than in the adsorbed state on the surface of oxidized GLP. [ABSTRACT FROM AUTHOR]

Polysaccharides from Ficus carica L. (FCP) exert multiple biological activities. As a biological macromolecule, the available knowledge about the specific structures and mechanisms of the biological activity of purified 'Brunswick' fig polysaccharides is currently limited. In the present study, chemical purification and characteristics were identified via chemical and instrumental analysis, and then the impact of FCP on immunomodulation activity in vitro and in vivo was examined. Structural characteristics showed that the molecular weight of the FCP sample was determined to be 127.5 kDa; the primary monosaccharides present in the FCP sample were galacturonic acid (GalA), arabinose (Ara), galactose (Gal), rhamnose (Rha), glucose (Glc), and xylose (Xyl) at a ratio of 0.321:0.287:0.269:0.091:0.013:0.011. Based on the investigation of in vitro immunomodulatory activity, FCP was found to stimulate the production of NO, TNF-α, and IL-6, and increased the pinocytic activity of macrophages. Further analysis revealed that FCP activated macrophages by interacting with Toll-like receptor 4 (TLR4). Moreover, the in vivo test results indicate that FCP showed a significant increase in serum pro-inflammatory factors in immunosuppressed mice. Overall, this study suggests that FCP has the potential to be utilized as a novel immunomodulator in the pharmaceutical and functional food industries. [ABSTRACT FROM AUTHOR]

[Display omitted] • This paper focuses on a novel analytical method based on packed-nanofibers solid-phase extraction coupled with HPLC-FLD to determine aflatoxins G1, B1, G2, B2 in foods, which contribute vitally to the application of nanoscience and material technology on the agricultural and food chemistry and analytical field. • This study confirmed that the as-synthesized electrospun nanofibers as adsorbent displays preferable potential practical application in the simultaneous pretreatment and analysis of toxins from various samples. • Under optimized conditions, one-step sample pretreatment integrating extraction, purification, enrichment and elution, was realized. The method can simultaneously process 12 samples within 5 min on a semi-automatic array SPE processor. A novel analytical method based on nanofiber-packed solid-phase extraction (PFSPE) combined with HPLC-FLD has been successfully developed and applied to determine aflatoxin B1, B2, G1, G2 in foods. In order to effectively adsorb analytes from complex food matrices, four types of nanofibers based on skeleton of polystyrene–polyvinyl pyrrolidone were prepared by electrospinning and applied as adsorbent to home-made solid-phase extraction device. The effects of type of nanofibers, pH of sample, type and concentration of salt ion, type of activation solvent, type and volume of eluent, amount of nanofibers, and extraction time on the adsorption/desorption were investigated and optimized. Under optimal conditions, the method showed satisfactory linear relationship, with limits of detection (LODs) of 0.07–0.17 ng g−1, intra-day and inter-day RSDs for spiked samples of 1.3–8.0 % and 1.9–5.8 %, and absolute recoveries in the range of 60.1–98.4 %. The results presented the great potential to be utilized to determine AFs in foodstuffs. [ABSTRACT FROM AUTHOR]