An overview of analytical methodologies for the determination of antibiotics in environmental waters

The widespread occurrence of antibiotics as contaminants in the aquatic environment has increased attention in the last years. The concern over the release of antibiotics into the environment is related primarily to the potential for the development of antimicrobial resistance among microorganisms. This article presents an overview of analytical methodologies for the determination of quinolone (Qs) and fluoroquinolone (FQs), macrolide (MLs), tetracycline (TCs), sulfonamide (SAs) antibiotics and trimethoprim (TMP) in different environmental waters. The analysis of these antibiotics has usually been carried out by high-performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) and to a lesser extent by ultraviolet (UV) or fluorescence detection (FD). A very important step before LC analysis is sample preparation and extraction leading to elimination of interferences and prevention of matrix effect and preconcentration of target analytes.     

Density Functional Study of Two Seven-Membered Unconventional Fullerenes C58F17CF3 and C58F18

The density functional method is used to study the structure, electronic properties, static linear polarizabilities, and optical absorption spectra of two seven‐membered unconventional fullerene derivatives C₅₈F₁₇CF₃ and C₅₈F₁₈. It is calculated that three sites chosen to locate the CF₃ are isoenergetic. The energy gaps of C₅₈F₁₈ and C₅₈F₁₇CF₃ are much larger than that of C₅₈, indicating the fluorination and trifluoromethylation of C₅₈ can remarkably enhance the kinetic stability. The density of states explore that the influence of CF₃ to the energy levels is mainly distributed in the energy range from ?10 to ?2 eV. However, when the CF₃ substitutes for F in C₅₈F₁₈, the bond lengths, energy gaps, static linear polarizabilities, and optical absorption spectra all show small variety.     

Theoretical study on the reaction of (Z)‐CF3CHCHCF3 with OH radicals

The mechanism on the OH‐initiated atmospheric oxidation reaction of (Z)‐CF₃CH?CHCF₃ with and without O₂/NO has been investigated theoretically. The electronic structure information of the potential energy surface was obtained at the M06‐2X/aug‐cc‐pVDZ level, and the single‐point energies were refined by MCG3/3 method. The calculations show that the (Z)‐CF₃CH?CHCF₃ + OH reaction occurs via addition‐elimination mechanism, leading to products CF₃ and CF₃CH?CH(OH), rather than H‐abstraction mechanism at low temperature. Under atmospheric condition, the OH‐addition intermediate is likely to react rapidly with O₂/NO, and the likely products are CF₃C(O)H, CF₂(O), CF₃CH(OH)CH(O), FNO, and HO₂, as is proposed by experiment. © 2013 Wiley Periodicals, Inc.     

Comprehensive Theoretical and Experimental Studies on the CF3H Fire‐extinguishing Mechanism

In order to clarify the chemical suppression mechanisms of CF₃H, experimental and theoretical studies were conducted respectively in this paper. Firstly, the combustion species in low pressure laminar premixed flat methane flames with CF₃H addition is measured by synchrotron radiation molecular beam mass spectrometry (SR‐MBMS) experimentally. Fire suppression chemistry of CF₃H is investigated by selective detection of combustion radicals and intermediates in experimental process. Secondly, quantum chemistry calculations are performed to calculate the potential energy surfaces (PES) for the CF₃H unimolecular dissociation reaction and reactions of CF₃H with free radical OH and H at the B3LYP/6‐311++G** and QCISD(T)/6‐311++G** levels. Finally, the chemical suppression mechanism of CF₃H was discussed by comparing the theoretical calculation with experimental measurement.     

类金刚石碳膜电极传感药物分子

以类金刚石碳膜(DLC)为工作电极,通过电化学方法来传感药物分子扑热息痛(PCT:paracetamol)和咖啡因(CF:caffeine).在室温条件下,pH为6.76的缓冲溶液中,通过循环伏安法可以分别和同时检测PCT和CF,并分别得到了对应的标准曲线.结果显示,在测试范围内PCT和CF的浓度都与峰电流呈良好的线性关系,DLC电极可以作为PCT和CF的生物传感器.     

The investigation of the friction and wear properties of surface‐treated carbon fiber/SiO2 reinforced PMMA composites

The mechanical properties of SiO₂ filler particles on carbon fibers have been under discussion for several decades; the diverse models, and the properties of the components relevant to retention, are critically reviewed in the first part of this study. In addition, to gain an insight into some possible combined effect of the carbon fiber/poly(methyl methacrylate) (CF/PMMA), interfacial adhesion strength and the tensile properties and dielectric strength of the hybrid composites were studied. Simple modified rules of mixtures are used to estimate the fiber efficiency factors for the strength and modulus of the hybrid composites. Except, with the increasing fraction of CFs in PMMA, the weld line area's elongation percent is decreased. Whereas for case of SiO₂, the 10 wt% is the threshold for micro injection molded weld line tensile strength and dielectric strength turning from decrease trend to increase. Same as CF, elongation of micro weld line samples is in general lower than neat PMMA as well, due to the addition of SiO₂ particles.     

Improving the interfacial property of carbon fiber/PI resin composite by grafting modification of carbon fiber surface

The poor interfacial adhesion between carbon fibers (CFs) and polyimide (PI) resin has seriously hampered the application of CF/PI composites. In this work, the interfacial adhesion was efficiently enhanced by grafting on the CF surface. Surface morphology and surface composition of modified carbon fibers were characterized, which indicated that acrylamide was grafted successfully on the CF surface and the surface roughness was increased slightly. After grafting, the interface shear strength of modified carbon fibers/PI composites was significantly improved by 86.96%, and the interlaminar shear strength was enhanced by 55.61% due to the covalent bonds in interphase and the toughening effect of sizing agent. Moreover, the mechanical properties of composites with different interfacial adhesion were measured, which further confirmed the effect of the grafting modification.     

Study on the atmospheric photochemical reaction of CF_3 radicals using ultraviolet photoelectron and photoionization mass spectrometer

A study of the atmospheric photochemical reaction of CF3 radical with CO and O2 was performed by using a homemade ultraviolet photoelectron spectrometer-photoionization mass spectrometer (PES- PIMS). The electronic structures and mechanism of ionization and dissociation of CF3OC(O)OOC(O)- OCF3 were investigated. It was indicated that the two bands on the photoelectron spectrum of CF3OC(O)OOC(O)OCF3 are the result of ionization of an electron from a lone pair of oxygen and a fluo- rine lone pair of CF3 group. The outermost electrons reside in the oxygen lone pair. The experimental and theoretical first vertical ionization energy is 13.21 and 13.178 eV, respectively, with the PES and OVGF method. They are in good agreement. The photo ionization and dissociation processes were discussed with the help of theoretical calculations and PES-PIMS experiment. After ionization, the parent ions prefer the dissociation of the C-O bond and giving the fragments CF3OCO and CF3 . It demonstrated that the ultraviolet photoelectron and photoionization mass spectrometer could be ap- plied widely in the study of atmospheric photochemical reaction.     

CF3Cl，CF2Cl2 和CFCl3分子外价壳层轨道特性的电子动量谱学研究

通过比较相同电子成分轨道的实验和DFT-B3LYP/6-311+G*理论的电子动量分布,系统研究了CF3Cl,CF2Cl2 和CFCl3分子外价壳层的轨道特性.研究结果表明CF3Cl,CF2Cl2 和CFCl3分子的Cl（3p）孤对电子轨道随着Cl原子个数增多,分子内相互作用逐渐增强,Cl原子3p轨道电子动量分布的特征逐渐淹没;F孤对电子轨道和的电子动量分布在高动量区出现了一个弱结构,且随Cl原子个数增多和F原子个数减少逐渐消失,这可能是由于部分轨道C-Cl 键电子成分的贡献;除3a1轨道外,C-F成键轨道和的理论的电子动量分布均在低动量端低于实验结果,可能是由于“d-like” 轨道低动量端的扭曲波效应;3a1轨道理论的电子动量分布均在 范围内低于实验结果,可能是由于扭曲波效应和电子关联等效应的影响.