Low temperature cleanup combined with magnetic nanoparticle extraction to determine pyrethroids residue in vegetables oils

To quantify trace pesticide residue in vegetable oil rapidly, low temperature cleanup combined with magnetic nanoparticle based solid phase extraction was developed to determine eight pyrethroids in vegetable oils, including tetramethrin, fenpropathrin, cypermethrin, decamethrin, fenvalerate, acrinathrin, permethrin and bifenthrin. Polystyrene coated magnetic nanoparticles were synthesised by a modified chemical coprecipitation combined with emulsion polymerisation method. The nanoparticles were afterwards characterised by Fourier transform-infrared spectroscopy, X-ray diffraction, transmission electron microscopy as well as vibrating sample magnetometer, and successfully employed as adsorbents for the magnetic solid phase extraction of pyrethroids which were cleaned up using low temperature approach in advance. Critical impact factors on the efficiency of the extraction method such as the mass of adsorbents used, volume and type of eluent solvent, extraction time as well as elution time were optimised subsequently. Regression analysis of the calibration curves of the eight pyrethroids yielded satisfactory correlation coefficients within the range of 0.980–0.998. Limit of detection and limit of quantification were calculated to be between 0.0290-0.0658 and 0.0890–0.1994 ng g⁻¹, respectively. Intra-day and inter-day reproducibility at different concentration levels also produced satisfactory recovery rates of 83.18–112.79% with relative standard deviations not exceeding 10.84% and 12.01%, respectively, suggesting desirable stability of the proposed method.     

牛肉中孕酮的气相色谱/燃烧炉/同位素比质谱检测

建立了牛肉中孕酮的气相色谱/燃烧炉/同位素比质谱(GC/C/IRMS)检测方法。牛肉样品用乙腈振荡和超声辅助提取,经Na Cl脱水,有机相离心和旋转蒸发后以Zn Cl2脱脂,然后用LC-C18、LC-Si、LC-NH2固相萃取柱净化,过滤液经半制备液相色谱(Pre-HPLC)的C18柱纯化,最后分析物以GC/C/IRMS系统分析。牛肉中加标外源性孕酮δ13C值为-30.64±0.24‰(n=6),牛肉内源性孕酮δ13C值为-25.70±0.13‰(n=6),单因素方差分析(ANOVA,p值=2.23×10-140.05)显示,内源性孕酮和外源性孕酮的δ13C值存在显著差异性,且牛肉中加标外源性孕酮δ13C值与孕酮标准溶液的δ13C值无差异性。同时,经模拟实验可知,实际样品中内外源性孕酮混合物的δ13C值与外源性孕酮的δ13C值具有同源性。结果表明,本方法特异性和准确性好,GC/C/IRMS是鉴别激素来源的有效工具,该方法填补了国内鉴别激素来源技术空白。     

葡萄酒中总酸测量的不确定度评定

目的评定酸碱滴定法测定葡萄酒中总酸的不确定度。方法依据JJF1059.1-2012《测量不确定度评定与表示》,分析总酸含量测定过程中的不确定度来源,通过建立数学模型量化不确定度分量,计算合成不确定度及扩展不确定度。结果该方法检测葡萄酒中总酸的合成不确定度为0.063 g/L,扩展不确定度为0.13g/L。本实验测定的葡萄酒中总酸含量结果为(5.53±0.13)g/L(k=2,置信区间P为95%)。结论本方法的不确定度主要由重复性、标准溶液滴定体积、取样体积等引入。     

Polarized light microscope method for the determination of asbestos fiber of textile

ABSTRACT

Optical spectrogram and optical characteristic parameters of six kinds of asbestos standard products were established by polarizing microscope to analyze the asbestos fiber, and utilized horizon estimation to get the semi-quantitative asbestos content in the samples. The sample had been observed form, refractive index, interference color, dispersion, ductility, color, pleochroism, cleavage, contour lines, bumps, rough, baker characteristics under different refractive index of oiled, to compare with standard optical spectra and characteristic parameters. Comparison between the situation of asbestos fiber particles and the standard map of mineral chips in the field of view, the percentage of asbestos fibers in the sample is estimated. The results showed that this method is accurate, simple and fast.     

Application of nitriding to electroless nickel–boron coatings: Chemical and structural effects; mechanical characterization; corrosion resistance

Electroless nickel–boron coatings, synthesized on mild steel, were submitted to nitridation treatments in varying conditions of pressure, temperature and atmosphere composition. One treatment was carried out under a reduced pressure of a nitrogen-based gas, the other under ambient pressure in a ammonia-based atmosphere.The modifications of the samples’ chemistry after those treatments were investigated by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectroscopy), GD-OES (Glow Discharge-Optical Emission Spectroscopy) and ToF-SIMS (Time of flight-Secondary Ions Mass Spectroscopy) analysis. Their structures and morphology were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy. The mechanical properties of the samples were investigated by micro- and nanohardness measurements successively on the free surface of the sample and on polished cross-sections; their roughness and resistance to scratch test were measured. Electrochemical corrosion tests were also carried out.The effects of both treatments were then compared: after the treatment carried out under lowered pressure, the coatings are dense, present signs of solution hardening and are characterized by a high hardness (close to 1600 hv₁₀₀). A combination layer is observable on the samples treated under an ammonia-based atmosphere. This outer layer possesses poorer mechanical properties but the inner layer of the coating presents properties similar to those of vacuum nitrided coatings. The corrosion resistance of the coatings is as good as that of heat treated coatings.     

Using locally estimated geodesic distance to optimize neighborhood graph for isometric data embedding

To deal with the highly twisted and folded manifold, this paper propose a geodesic distance-based approach to build the neighborhood graph for isometric embedding. This approach assumes that the neighborhood of a point located at the highly twisted place of the manifold may not be linear so that its neighbors should be determined by geodesic distance. This approach firstly determines the neighborhood for each point using Euclidean distance and then applies the locally estimated geodesic distances to optimize the neighborhood. It increases only linear time complexity. Furthermore the optimized neighborhood can speed up the subsequent embedding process. The proposed approach is simple, general and easy to deal with a wider range of data. The conducted experiments on both synthetic and real data sets validate the approach.     

The antimicrobial effects and synergistic antibacterial mechanism of the combination of ε-Polylysine and nisin against Bacillus subtilis

The aim of the present study was to evaluate the combined effects of ε-Polylysine (ε-PL) and nisin and investigate the synergistic action of these compounds against Bacillus subtilis (B. subtilis).The combination of ε-PL and nisin showed synergistic anti-microbial activity against Escherichia coli (E. coli), B. subtilis and Staphylococcus aureus (S. aureus). SEM and TEM microscopy revealed that combined treatment with ε-PL and nisin synergistically damaged the morphology of tested bacterial cells. Propidium iodide (PI) infiltration experiments indicated that combined treatment with ε-PL and nisin synergistically enhanced the permeability of the bacterial cell membrane, likely reflecting the inhibition of both Na⁺K⁺- and Ca⁺⁺ Mg⁺⁺-ATPase activities through these compounds. The fluorescence spectrum showed an interaction between ε-PL and DNA, but not between nisin and DNA. The mode of ε-PL in binding with DNA was similar to that of ethidium bromide (EB). These results indicated that the uptake of ε-PL into cells was promoted through nisin, and subsequently, ε-PL interacted with the intracellular DNA achieving a synergistic effect.     

Raman investigation of optical phonons in the ion implanted Hg1−xCdxTe

Raman scattering is studied here for Hg_1−xCd_xTe (x = 0.3) samples implanted with 180-keV of B¹¹ ions with various doses up to 1 × 10¹⁵ cm⁻². Considering disorder in the implanted HgCdTe material, the correlation length of Raman active optical phonons is determined as a short range order in the nanocrystals. Phonon softening and asymmetric broadening are investigated for HgTe like LO and TO phonon modes in the Raman spectrum while CdTe like modes almost disappeared for the dose greater than 5 × 10¹³ cm⁻². Disorder is measured quantitatively for wide ranges of doses on the basis of phonon confinement model. Nanostructures of the near-surface implantation-induced damage layer are known to consist of a mixture of amorphous HgCdTe and its nanocrystals. A significant reduction of the nanocrystallites size is reported here with increasing dose i.e. L = 34–46 A⁰ at dose of 1 × 10¹⁵ cm⁻².     

蒜制品中二氧化硫4种检测方法的比较研究

目的研究比较蒜制品中二氧化硫的检测方法。方法通过应用碘量法、比色法、柱后衍生-高效液相色谱法以及离子色谱法检测蒜制品中二氧化硫的结果进行比较分析。结果鲜蒜和脱水蒜制品的比色法检测结果差异较大。采用比色法(盐酸副玫瑰苯胺法)检测鲜蒜和脱水蒜制品中二氧化硫的结果普遍较高,蒜罐头类的检测结果与其他检测方法的值接近。采用滴定法、高效液相色谱法和离子色谱法的检测结果都较为接近。结论 4种方法都可用于蒜制品中二氧化硫的检测,但比色法不适用于鲜大蒜及脱水蒜制品中二氧化硫的检测。     

Carbon fiber/epoxy composite property enhancement through incorporation of carbon nanotubes at the fiber–matrix interphase – Part I: The development of carbon nanotube coated carbon fibers and the evaluation of their adhesion

A new method to realize the uniform coating of carbon nanotubes (CNTs) to carbon fibers (CFs) has been developed, which enables the scalable fabrication of CNT containing CF/epoxy composites. In this method, CNTs are treated by cationic polymers, then, the CNTs are coated to CFs by immersion into a CNT/water suspension. Good dispersion is achieved by repulsive force between positively charged CNTs and uniform coating of the CNTs is achieved by attractive forces between positively charged CNTs and negatively charged CFs. It is found that the use of specific cationic polymers including polyethyleneimine (PEI) results in stable CNT/water suspensions, and uniform coating of the CNTs. Single fiber fragmentation tests of the CF/epoxy composites were conducted to evaluate the strength of interface and interphase under shear loading. The results show that the combination of epoxy resin sizing and PEI treated CNT coating to CFs results in high interfacial shear strength.