超声波辅助萃取同位素稀释质谱法测定聚氯乙烯中6种邻苯二甲酸酯

采用超声波辅助萃取同位素稀释质谱法测定聚氯乙烯中6种邻苯二甲酸酯的含量。以四氢呋喃为溶剂对样品进行超声波辅助提取后,加入甲醇对聚合物进行沉淀,取上清液,经冷冻离心后进行气相色谱一质谱分析,并采用氘代邻苯二甲酸酯为内标,单点校正法定量。该方法应用于中、日、韩计量比对的样品测定中,两天进行的6次测定结果相对标准偏差为0．7％～3．0％。最终比对结果显示3个国家的数据取得很好的一致性,除DEP相对标准偏差为2．4％以外,其它5种邻苯二甲酸酯相对标准偏差为0．7％～1．2％,测定结果的相对扩展不确定度为1．8％～4．9％,证明该方法准确、可靠。     

Characterization of Key Odorants in Scallion Pancake and Investigation on Their Changes during Storage

To characterize key odorants in scallion pancake (SP), volatiles were extracted by solvent extraction-solvent assisted flavor evaporation. A total of 51 odor-active compounds were identified by gas chromatography-olfactometry (GC-O) and chromatography–mass spectrometry (GC-MS). (Z/E)-3,6-Diethyl-1,2,4,5-tetrathiane was detected for the first time in scallion food. Application of aroma extract dilution analysis to extracts showed maltol, methyl propyl disulfide, dipropyl disulfide and 2-pentylfuran had the highest flavor dilution (FD) factor of 4096. Twenty-three odorants with FD factors ≥ 8 were quantitated, and their odor active values (OAVs) were calculated. Ten compounds with OAVs ≥ 1 were determined as the key odorants; a recombinate model prepared from the key odorants, including (E,E)-2,4-decadienal, dimethyl trisulfide, methyl propyl disulfide, hexanal, dipropyl trisulfide, maltol, acetoin, 2-methylnaphthalene, 2-pentylfuran and 2(5H)-furanone, successfully simulated the overall aroma profile of SP. The changes in odorants during storage were investigated further. With increasing concentrations and OAVs during storage, hexanal became an off-flavor compound.     

Effect of rGO on polymer-dispersed liquid crystal fabricated by RAFT polymerisation

In this study, we demonstrated that doping polymer matrix with a small amount of reduced graphene oxide (rGO) component (0.05–0.2%) had significant influence on the polymerisation kinetics and electro-optical performances of polymer-dispersed liquid crystal films (PDLCs) fabricated with macro reversible addition-fragmentation chain transfer agents. The effects of rGO content were studied in terms of morphology, compound viscosity, polymer conductivity, polymerisation kinetics and driving voltage of PDLCs. The results exhibited that higher rGO content increased the compound viscosity and the entire process proceeded slowly. Furthermore, the addition of rGO increased the polymer conductivity and local electric field, and reduced the saturation voltage as well as the threshold voltage from 27.3 to 19.5 V and 13.2 to 6.41 V, respectively.     

A Green and Efficient Approach for the Synthesis of 3-Chalcogen Benzo[b]Furans via I2-Mediated Cascade Annulation Reaction of 2-Alkynylanisoles at Room Temperature in Water

Abstract

An efficient and green aqueous protocol to access 3-chalcogen benzo[b]furan derivatives has been developed. The reaction can proceed via I₂-mediated intramolecular annulation reaction of 2-alkynylanisoles with diaryl disulfides (diselenides) in water or under solvent-free conditions at room temperature. With the participation of I₂, a variety of 3-chalcogen benzo[b]furan derivatives were obtained in good to excellent yields. This reaction was considered to work via an iodocyclization cascade mechanism and the intermediate 3-iodo-2-phenylbenzofuran was detected by GC-MS.     

一种新型交替迭代算法用于农药GC-MS信号快速分析

化学计量学算法为重叠GC-MS信号解析提供了有效手段. 免疫算法(IAs)可根据标准样品的信号(色谱或质谱)对重叠GC-MS信号进行解析并得到重叠信号中各组分的信息. 但是标样信号与实际测量信号之间的差别会造成解析结果出现偏差. 针对标样信号与测量信号不一致的问题, 作者提出了一种交替迭代算法用于重叠GC-MS测量信号的直接解析. 该方法在不提供标样信号的情况下可以解析出组分的质谱和色谱信息. 计算过程中, 采用随机产生的质谱作为初始输入, 利用最小二乘和IA算法交替计算质谱和色谱, 直到满足终止条件. 采用所建立的方法对40种组分的农药混合物进行了分析, 使用快速升温程序在10 min保留时间内得到了全部组分的色谱和质谱信息.     

近红外光谱结合化学计量学评价胚胎发育潜能

使用近红外光谱分析方法测量培养后的胚胎培养液,结合偏最小二乘判别分析对胚胎发育潜能进行评价,鉴别具有妊娠能力与不具妊娠能力的胚胎。为了提高模型的判别能力,消除无信息变量对模型稳定性影响,分别采用基于蒙特卡罗的无信息变量消除法(MC-UVE)、竞争性自适应加权抽样法(CARS)与基于变量稳定性的竞争性自适应加权抽样法(SCARS),对光谱进行波长选择。结果表明,与采用全谱74%的正判率相比较,采用这3种波长选择方法,模型独立检验集的正判率分别提高至74.24%,77.12%与80.10%,建模使用变量数降至50以内。比较发现,SCARS的模型优化能力和稳定性均好于MC-UVE和CARS方法。采用近红外光谱结合化学计量学方法预测胚胎的发育潜能是可行的。     

Selective fluorescence response and magnetic separation probe for 2,4,6-trinitrotoluene based on iron oxide magnetic nanoparticles

Despite the rapid development of nanomaterials and nanotechnology, it is still desirable to develop novel nanoparticle-based techniques which are cost-effective, timesaving, and environment-friendly, and with ease of operation and procedural simplicity, for assay of target analytes. In the work discussed in this paper, the dye fluorescein isothiocyanate (FITC) was conjugated to 1,6-hexanediamine (HDA)-capped iron oxide magnetic nanoparticles (FITC–HDA Fe₃O₄ MNPs), and the product was characterized. HDA ligands on the surface of Fe₃O₄ MNPs can bind 2,4,6-trinitrotoluene (TNT) to form TNT anions by acid–base pairing interaction. Formation of TNT anions, and captured TNT substantially affect the emission of FITC on the surface of the Fe₃O₄ MNPs, resulting in quenching of the fluorescence at 519 nm. A novel FITC–HDA Fe₃O₄ MNPs-based probe featuring chemosensing and magnetic separation has therefore been constructed. i.e. FITC–HDA Fe₃O₄ MNPs had a highly selective fluorescence response and enabled magnetic separation of TNT from other nitroaromatic compounds by quenching of the emission of FITC and capture of TNT in aqueous solution. Very good linearity was observed for TNT concentrations in the range 0.05–1.5 μmol?L^?1, with a detection limit of 37.2 nmol?L^?1 and RSD of 4.7 % (n?=?7). Approximately 12 % of the total amount of TNT was captured. The proposed methods are well-suited to trace detection and capture of TNT in aqueous solution.

Modeling and Simulation of Bonding and Optical Characters of Ternary Nanocrystals

In this paper, conformations of the ternary structures ZnSe(Te), ZnS(Te), ZnS(Se), CdSe(Te), CdS(Te) and CdS(Se) were optimized, and their orbital, spectra have been investigated at the B3LYP/LANL2DZ level. First, we have found some rules which agreed with experimental results. HOMO–LUMO gaps, WBI values and the wavelengths of the absorption peaks of ternary structures changed gradually with the ratio of Te, Se and S atoms in ternary structures. Second, analysis of Raman spectra revealed that doped structures had the spectra of two relevant binary clusters. Namely, Raman spectra of ternary ZnSe(Te) clusters had the Raman peaks of ZnSe and ZnTe. In this way, with the help of the Raman spectra, the formations of the ternary structures can be determined in experiment. This was important to estimate during synthesis progress. Finally, calculated results have proved that ZnS and CdS structures had the shorter wavelengths of the absorption peaks, the higher excited energies of singlets, and good stability.