Insight on the heterogeneously activated H2O2 with goethite under visible light for cefradine degradation: pH dependence and photoassisted effect.

The iron mineral-catalyzed degradation of cephalosporin antibiotics with H2O2 occurs ubiquitously in nature. Despite numerous studies, the effects of environmental conditions on reactive species production and degradation processes of cephalosporins remain unclear. Here, we report the iron mineral of goethite as the efficient and heterogenous catalyst for the degradation of cefradine (CRD) via H2O2 activation under different conditions involving pH and visible light irradiation. Results show that the CRD removal rate is highly dependent on pH and visible light irradiation. Interestingly, when the pH ranges from 4.0 to 7.0, the degradation intermediates of CRD under dark are the same as under visible light conditions in the goethite/H2O2 system. And, the ratio of CRD degradation rate constant (kLight/kDark) reaches a maximum at pH 5.0, suggesting that CRD existing as zwitterion species is preferable for its removal with photoassistance. The mechanism investigation reveals that both •OH and ≡[FeIVO]2+ oxidants are generated during the reaction process, and •OH is the major oxidant at acidic pH, while ≡[FeIVO]2+ is more likely to be formed with photoassistance at near-neutral pH. According to UPLC-MS/MS analysis, CRD degradation likely happens via hydrogen atom abstraction from cyclohexadienyl by •OH, thioether and olefin oxidation by ≡[FeIVO]2+, and FeIII-catalyzed hydrolytic cleavage of ß-lactam ring. These findings highlight the vital roles of pH and photoassistance in the heterogeneously activated H2O2 with goethite for CRD degradation.

Molecular structure modification of ovalbumin through controlled glycosylation with dextran for its emulsibility improvement.

Ovalbumin (OVA) is a high nutritious protein, but the poor emulsibility limited its application. The present study glycosylated OVA with dextran (Dex) by controlled wetheating (60-90 °C for 3 h). Temperature was an inductive factor for glycosylation degree (DG and browning intensity), and higher temperature could accelerate the reaction. Variations in molecular structure of OVA were analyzed by SDS-PAGE, FTIR, fluorescence spectroscopy and UV spectroscopy, which verified successes in the generation of glycoconjugate with more flexible structure. Emulsifying activity index (EAI) and emulsion stability index (ESI) for the emulsion of OVA-Dex glycoconjugates were significantly enhanced with the increasing of glycosylation temperature. Moreover, confocal laser scanning results revealed that the emulsion exhibited smaller size and more uniform distribution, and slower transmission profiles were checked by LUMiSizer centrifugal analysis as well, confirming the emulsibility improvement of OVA. Thus, controlled glycosylation reaction is an available method to improve the emulsifying properties of OVA.

Speciation Analysis of Chromium in Chromium-Enriched Yeast by Ion Chromatography-Inductively Coupled Plasma Mass Spectrometry.

Chromium-enriched yeast (CrY) is a popular Cr dietary supplement, but suitable speciation analysis of highly toxic Cr(VI) in CrY is not available. Ion chromatography-inductively coupled plasma mass spectrometry method was firstly developed and validated for the quantification of Cr(III) and Cr(VI). Ultrasound-assisted weakly alkaline EDTA solution combined with boiling was used to extract two Cr species in CrY. Two species were separated on two successive anion-exchange columns using a mobile phase of 0.6 mmol/L EDTA and 76 mmol/L NH4NO3 solution. The method was sensitive, accurate (92.4-100.9%), and precise (0.8-3.1%). Species of Cr(VI) were not found in CrY.