Physiologically based pharmacokinetic (PBPK) models are scientific methods used to predict veterinary drug residues that may occur in food-producing animals, and which have powerful extrapolation ...ability. Quinocetone (QCT) and mequindox (MEQ) are widely used in China for the prevention of bacterial infections and promoting animal growth, but their abuse causes a potential threat to human health. In this study, a flow-limited PBPK model was developed to simulate simultaneously residue depletion of QCT and its marker residue dideoxyquinocetone (DQCT) in pigs. The model included compartments for blood, liver, kidney, muscle and fat and an extra compartment representing the other tissues. Physiological parameters were obtained from the literature. Plasma protein binding rates, renal clearances and tissue/plasma partition coefficients were determined by in vitro and in vivo experiments. The model was calibrated and validated with several pharmacokinetic and residue-depletion datasets from the literature. Sensitivity analysis and Monte Carlo simulations were incorporated into the PBPK model to estimate individual variation of residual concentrations. The PBPK model for MEQ, the congener compound of QCT, was built through cross-compound extrapolation based on the model for QCT. The QCT model accurately predicted the concentrations of QCT and DQCT in various tissues at most time points, especially the later time points. Correlation coefficients between predicted and measured values for all tissues were greater than 0.9. Monte Carlo simulations showed excellent consistency between estimated concentration distributions and measured data points. The extrapolation model also showed good predictive power. The present models contribute to improve the residue monitoring systems of QCT and MEQ, and provide evidence of the usefulness of PBPK model extrapolation for the same kinds of compounds.
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•The coal dust explosion residues are still capable of exploding.•Coal dust and its explosion residues were compared on HRR and flame speed.•Chemical functional groups of multiple ...explosion residues were investigated.•Residues explosion is a solid-state reaction dominated by fixed carbon.
The complex post-explosion environment in a coal mine can induce multiple methane explosions, in which coal dust explosion residues might be involved. To investigate the explosion possibility and characteristics of coal dust explosion solid residues, tests were carried out in a 20 L explosion device. The results show that the collected coal dust solid residues remain capable of exploding. Unexpectedly, the explosion intensity of residues is still strong, despite being weaker than that of coal dust: the residues are characterised by a slower flame propagation speed and a lower heat release rate than that of coal dust. The re-explosion product analysis shows that more holes appeared and the elemental contents of carbon, oxygen, and nitrogen decreased. Proximate analysis and FTIR analysis reveal that fixed carbon, instead of volatile matter and chemical bonds, in these residues is further combusted in the re-explosion process. The research results are of significance when assessing explosion hazards arising from coal dust explosion residues in a coal mine.
An attractive drug target to combat COVID‐19 is the main protease (Mpro) because of its key role in the viral life cycle by processing the polyproteins translated from the viral RNA. Studying the ...crystal structures of the protease is important to enhance our understanding of its mechanism of action at the atomic‐level resolution, and consequently may provide crucial structural insights for structure‐based drug discovery. In the current study, we report a comparative structural analysis of the Mpro substrate binding site for both apo and holo forms to identify key interacting residues and conserved water molecules during the ligand‐binding process. It is shown that in addition to the catalytic dyad residues (His41 and Cys145), the oxyanion hole residues (Asn142–Ser144) and residues His164–Glu166 form essential parts of the substrate‐binding pocket of the protease in the binding process. Furthermore, we address the issue of the substrate‐binding pocket flexibility and show that two adjacent loops in the Mpro structures (residues Thr45–Met49 and Arg188–Ala191) with high flexibility can regulate the binding cavity’ accessibility for different ligand sizes. Moreover, we discuss in detail the various structural and functional roles of several important conserved and mobile water molecules within and around the binding site in the proper enzymatic function of Mpro. We also present a new docking protocol in the framework of the ensemble docking strategy. The performance of the docking protocol has been evaluated in predicting ligand binding pose and affinity ranking for two popular docking programs; AutoDock4 and AutoDock Vina. Our docking results suggest that the top‐ranked poses of the most populated clusters obtained by AutoDock Vina are the most important representative docking runs that show a very good performance in estimating experimental binding poses and affinity ranking.
•QuEChERS procedure combined with UHPLC–MS/MS determination of pesticide residues in orange juice.•Optimization of the best QuEChERS conditions by central composite design (CCD).•Good recoveries ...(70–117%), with RSD <19% and method LOD from 0.1 to 12.4μgL−1.•The validated method was efficiently applied to real samples.
In this study, different extraction procedures based on the QuEChERS method were compared for the multiresidue determination of pesticides in orange juice by ultra high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC–MS/MS). After choosing preliminary conditions, an experimental design was carried out with the variables C18, PSA, NaOH and CH3COONa to optimize the sample preparation step. The validation results of the validation were satisfactory, since the method presented recoveries between 70% and 118%, with RSD lower than 19% for spike levels between 10 and 100μgL−1. The method limit of detection (LOD) and limit of quantification (LOQ) ranged from 3.0 to 7.6μgL−1 and from 4.9 to 26μgL−1, respectively. The method developed was adequate for the determination of 74 pesticide residues in orange juice.
•The integration of IMS into UHPLC-HRMS is reviewed.•Focus is the utility of the instrumentation in the field of multiresidue analysis.•The usability of commercially available techniques is ...explored.•Strengths, limitations, and future potentials are critically discussed.
Residue chemists who analyse pesticides in vegetables or veterinary drugs in animal-based food are currently facing a situation where there is a requirement to detect more and more compounds at lower and lower concentrations. Conventional tandem quadrupole instruments provide sufficient sensitivity, but speed and selectivity appear as future limitations. This will become an even larger issue when there is a need to not only detect active compounds but also their degradation products and metabolites. This will likely lead to a situation in which the conventional targeted approach must be expanded or augmented by a certain non-targeted strategy. High-resolution mass spectrometry provides such capabilities, but it frequently requires an additional degree of selectivity for the unequivocal confirmation of analytes present at trace levels in highly complex and variable food matrices. The hyphenation of ultrahigh performance liquid chromatography with ion mobility and high-resolution mass spectrometry provides analytical chemists with a new tool for performing such a demanding multiresidue analysis. The objective of this paper is to investigate the benefits of the added ion mobility dimension as well as to critically discuss the current limitations of this commercially available technology.
•Analysis of pesticide and veterinary drug residues in baby food by UHPLC-Q-Orbitrap.•Optimization of the analytical parameters was achieved with a d-optimal design.•The determination of drug ...residues in baby food using QuEChERS.•The proposed sample preparation method is simple, robust and cheaper.
A new analytical method was developed and validated for simultaneous analysis of 333 pesticide and veterinary drug residues in baby food. Response surface methodology was employed to optimize a generic extraction method. Ultrahigh-performance liquid chromatography and electrospray ionization quadrupole Orbitrap high-resolution mass spectrometry (UHPLC-ESI Q-Orbitrap) was used for the separation and detection of all the analytes. The method was validated by taking into consideration the guidelines specified in Commission Decision 2002/657/EC and SANCO/12571/2013. The extraction recoveries were in a range of 79.8–110.7%, with coefficient of variation <8.3%. The 333 compounds behave dynamic in the range 0.1–1000μgkg−1 concentration, with correlation coefficient >0.99. The limits of detection for the analytes are in the range 0.01–5.35μgkg−1. The limits of quantification for the analytes are in the range 0.01–9.27μgkg−1. This method has been successfully applied on screening of pesticide and veterinary drugs in ninety-three commercial baby food samples, and tilmicosin, fenbendazole, tylosin tartrate and thiabendazole were detected in some samples tested in this study. The present study is very useful for fast screening of different food contaminants.
Biomass pyrolysis: past, present, and future Fahmy, Tamer Y. A.; Fahmy, Yehia; Mobarak, Fardous ...
Environment, development and sustainability,
2020/1, Letnik:
22, Številka:
1
Journal Article
Recenzirano
Biomass pyrolysis is a promising renewable sustainable source of fuels and petrochemical substitutes. It may help in compensating the progressive consumption of fossil-fuel reserves. The present ...article outlines biomass pyrolysis. Various types of biomass used for pyrolysis are encompassed, e.g., wood, agricultural residues, sewage. Categories of pyrolysis are outlined, e.g., flash, fast, and slow. Emphasis is laid on current and future trends in biomass pyrolysis, e.g., microwave pyrolysis, solar pyrolysis, plasma pyrolysis, hydrogen production via biomass pyrolysis, co-pyrolysis of biomass with synthetic polymers and sewage, selective preparation of high-valued chemicals, pyrolysis of exotic biomass (coffee grounds and cotton shells), comparison between algal and terrestrial biomass pyrolysis. Specific future prospects are investigated, e.g., preparation of supercapacitor biochar materials by one-pot one-step pyrolysis of biomass with other ingredients, and fabricating metallic catalysts embedded on biochar for removal of environmental contaminants. The authors predict that combining solar pyrolysis with hydrogen production would be the eco-friendliest and most energetically feasible process in the future. Since hydrogen is an ideal clean fuel, this process may share in limiting climate changes due to CO
2
emissions.
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