Melamine as an important chemical raw material and a harmful additive in foods has attracted many people’s attention. In the present paper, The graphite-epoxy composited solid phase electrode was modified with bismut...Melamine as an important chemical raw material and a harmful additive in foods has attracted many people’s attention. In the present paper, The graphite-epoxy composited solid phase electrode was modified with bismuth layer by cyclic voltammetric deposition of bismuth from Bi(NO3)3 aqueous solution including 0.10 M HNO3, and hydrolyzed into micro bismuthyl chloride on-sites. Melamine in fresh milk was extracted with solid phase micro-extraction on the bismuthyl chloride modified graphite-epoxy composited solid electrode. The adsorption of melamine on bismuthyl chloride particle surfaces follows a Freundlich adsorption model, and results in the decrease of the reduction peak current of bismuth in bismuthyl chloride, and determined by differential pulse voltammetry from fresh milk in a larger concentration range of 10–4 ? 10–12 M with detection limit of 2.5 ? 10–12 M and relative standard deviation of 2.7%. The method is sensitive, convenient and was applied in the detection of melamine in fresh milk with relative deviation of 4.2% in content of 0.45 mg/kg melamine in the fresh milk.展开更多
2,4,6-trichlorophenol molecularly imprinted suspension polymer has been prepared and applied to the molecularly imprinted micro-solid-phase extraction procedure for selective preconcentration of phenolic compounds fro...2,4,6-trichlorophenol molecularly imprinted suspension polymer has been prepared and applied to the molecularly imprinted micro-solid-phase extraction procedure for selective preconcentration of phenolic compounds from environmental water samples. The influence of functional monomer, cross-linker, polymerization condition, porogen, and the ratio of template molecule and functional monomer to cross-linker on the size of the obtained particles were investigated. It was found that methyacrylic acid as functional monomer, divinylbenzene as cross-linker, the molar ratio of template molecule and functional monomer to cross-linker was 1:4:20, the amount of AIBN was 100 mg, ultraviolet radiation at 365 nm were the optimal conditions, and at these conditions, the polymers had the best adsorption efficiency and had the monodispersity of 2 - 3 μm microsphere particles. The characteristics of the MIMSPE method were valid by high performance liquid chromatography. This MIMSPE-HPLC method has been successfully applied to the direct preconcentration and determination of phenolic compounds (phenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol) in environmental water samples.展开更多
Microstructure evolution of wrought aluminum alloy extruded rods and the mechanism of liquid phase formation during reheating were investigated. And the relation between the volume fraction of liquid phase and the rec...Microstructure evolution of wrought aluminum alloy extruded rods and the mechanism of liquid phase formation during reheating were investigated. And the relation between the volume fraction of liquid phase and the recrystallization microstructure was proposed. The results show that increase in reheating temperature and time can augment the volume fraction of liquid phase and accelerate the grain spheroidization, as a result of which the requirement of semi-solid forming can be satisfied. Due to the higher aberration energy of grain boundary, the melting point is lowered as a result of the easy diffusion of atoms. At higher reheating temperature the grain boundary melts, the growth of the recrystallized grain is inhibited and the grain is refined. The composition of the low melt-point phase along the recrystallized grains was determined using EDS. It can be seen from the experimental results that when the extrusion rod of the wrought aluminum alloy is reheated at 610℃ for 20min, perfect fine equiaxial grains can be obtained, the average grain size is about 66.34μm and the volume fraction of solid phase is about 68%.展开更多
The paper presents the study of hierarchy of deformation wave-processes from nano- to macro-structural level, which takes place in dissimilar materials, bonded by high-temperature vacuum rolling in solid phase. The fo...The paper presents the study of hierarchy of deformation wave-processes from nano- to macro-structural level, which takes place in dissimilar materials, bonded by high-temperature vacuum rolling in solid phase. The focus was on the processes that occur on the interface of the bonded materials: mass trasfer of impurities and alloying elements stimulated by deformation, the study of nano- and micro-hardness.展开更多
为探究不同等级双井绿茶香气物质组成特征,利用顶空固相微萃取-气相色谱-质谱联用技术(Headspace solid-phase micro extraction and gas chromatography mass spectrometry,HS-SPME-GC/MS)对修水县双井银毫、双井绿茶特级、双井绿茶一...为探究不同等级双井绿茶香气物质组成特征,利用顶空固相微萃取-气相色谱-质谱联用技术(Headspace solid-phase micro extraction and gas chromatography mass spectrometry,HS-SPME-GC/MS)对修水县双井银毫、双井绿茶特级、双井绿茶一级和双井绿茶二级四个不同等级的双井绿茶的香气物质进行了检测分析。结果表明,从四个不同等级的双井绿茶中共鉴定出70种香气物质,主要包括醇类、烯烃类、烷烃类、酯类等化合物。不同等级的双井绿茶中香气物质组成及相对含量均有差异,通过主成分分析(Principal component analysis,PCA)和偏最小二乘法-判别分析(Partial least squares-discriminant analysis,PLS-DA),可以有效区分不同等级的双井绿茶。不同等级双井绿茶香气差异主要由反式-β-金合欢烯、香叶醇、水杨酸甲酯、茉莉酮、苯乙醇等14种关键化合物差异引起。在不同等级双井绿茶中关键香气物质表现出不同的分布规律,随着芽叶开展,α-椰油烯、石竹烯及己酸乙酯含量降低,而顺式-3-己烯醇、香叶醇及水杨酸甲酯含量呈增加趋势,芳樟醇、茉莉酮、反式-橙花叔醇含量从低到高,随后含量又迅速下降。本文研究了不同等级双井绿茶中香气物质的组成特征及关键香气物质的分布规律,为今后双井绿茶生产提供了理论依据。展开更多
文摘Melamine as an important chemical raw material and a harmful additive in foods has attracted many people’s attention. In the present paper, The graphite-epoxy composited solid phase electrode was modified with bismuth layer by cyclic voltammetric deposition of bismuth from Bi(NO3)3 aqueous solution including 0.10 M HNO3, and hydrolyzed into micro bismuthyl chloride on-sites. Melamine in fresh milk was extracted with solid phase micro-extraction on the bismuthyl chloride modified graphite-epoxy composited solid electrode. The adsorption of melamine on bismuthyl chloride particle surfaces follows a Freundlich adsorption model, and results in the decrease of the reduction peak current of bismuth in bismuthyl chloride, and determined by differential pulse voltammetry from fresh milk in a larger concentration range of 10–4 ? 10–12 M with detection limit of 2.5 ? 10–12 M and relative standard deviation of 2.7%. The method is sensitive, convenient and was applied in the detection of melamine in fresh milk with relative deviation of 4.2% in content of 0.45 mg/kg melamine in the fresh milk.
文摘2,4,6-trichlorophenol molecularly imprinted suspension polymer has been prepared and applied to the molecularly imprinted micro-solid-phase extraction procedure for selective preconcentration of phenolic compounds from environmental water samples. The influence of functional monomer, cross-linker, polymerization condition, porogen, and the ratio of template molecule and functional monomer to cross-linker on the size of the obtained particles were investigated. It was found that methyacrylic acid as functional monomer, divinylbenzene as cross-linker, the molar ratio of template molecule and functional monomer to cross-linker was 1:4:20, the amount of AIBN was 100 mg, ultraviolet radiation at 365 nm were the optimal conditions, and at these conditions, the polymers had the best adsorption efficiency and had the monodispersity of 2 - 3 μm microsphere particles. The characteristics of the MIMSPE method were valid by high performance liquid chromatography. This MIMSPE-HPLC method has been successfully applied to the direct preconcentration and determination of phenolic compounds (phenol, 4-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol, pentachlorophenol) in environmental water samples.
文摘Microstructure evolution of wrought aluminum alloy extruded rods and the mechanism of liquid phase formation during reheating were investigated. And the relation between the volume fraction of liquid phase and the recrystallization microstructure was proposed. The results show that increase in reheating temperature and time can augment the volume fraction of liquid phase and accelerate the grain spheroidization, as a result of which the requirement of semi-solid forming can be satisfied. Due to the higher aberration energy of grain boundary, the melting point is lowered as a result of the easy diffusion of atoms. At higher reheating temperature the grain boundary melts, the growth of the recrystallized grain is inhibited and the grain is refined. The composition of the low melt-point phase along the recrystallized grains was determined using EDS. It can be seen from the experimental results that when the extrusion rod of the wrought aluminum alloy is reheated at 610℃ for 20min, perfect fine equiaxial grains can be obtained, the average grain size is about 66.34μm and the volume fraction of solid phase is about 68%.
文摘The paper presents the study of hierarchy of deformation wave-processes from nano- to macro-structural level, which takes place in dissimilar materials, bonded by high-temperature vacuum rolling in solid phase. The focus was on the processes that occur on the interface of the bonded materials: mass trasfer of impurities and alloying elements stimulated by deformation, the study of nano- and micro-hardness.
文摘为探究不同等级双井绿茶香气物质组成特征,利用顶空固相微萃取-气相色谱-质谱联用技术(Headspace solid-phase micro extraction and gas chromatography mass spectrometry,HS-SPME-GC/MS)对修水县双井银毫、双井绿茶特级、双井绿茶一级和双井绿茶二级四个不同等级的双井绿茶的香气物质进行了检测分析。结果表明,从四个不同等级的双井绿茶中共鉴定出70种香气物质,主要包括醇类、烯烃类、烷烃类、酯类等化合物。不同等级的双井绿茶中香气物质组成及相对含量均有差异,通过主成分分析(Principal component analysis,PCA)和偏最小二乘法-判别分析(Partial least squares-discriminant analysis,PLS-DA),可以有效区分不同等级的双井绿茶。不同等级双井绿茶香气差异主要由反式-β-金合欢烯、香叶醇、水杨酸甲酯、茉莉酮、苯乙醇等14种关键化合物差异引起。在不同等级双井绿茶中关键香气物质表现出不同的分布规律,随着芽叶开展,α-椰油烯、石竹烯及己酸乙酯含量降低,而顺式-3-己烯醇、香叶醇及水杨酸甲酯含量呈增加趋势,芳樟醇、茉莉酮、反式-橙花叔醇含量从低到高,随后含量又迅速下降。本文研究了不同等级双井绿茶中香气物质的组成特征及关键香气物质的分布规律,为今后双井绿茶生产提供了理论依据。
