植物油中苯并(a)芘液相色谱检测方法的研究

本文研究了植物油中苯并(a)芘的高效液相色谱检测法。试样中的苯并(a)芘用丙酮提取,液相色谱-荧光检测器测定,外标峰面积法定量。苯并(a)芘在(0.5~20)ng/m L范围内呈良好的线性关系,3个水平(2.5μg/kg、5.0μg/kg、10.0μg/kg)添加苯并(a)芘的回收率为93.0%~104.4%,相对标准偏差(RSD)为2.9%~3.9%,检出限为1.0μg/kg。此方法简便、快捷,适用于植物油中苯并(a)芘的检测。     

氢化物原子荧光光谱法同时测定生活饮用水中砷和硒

建立了氢化物发生原子荧光光谱法同时测定生活饮用水中砷和硒的方法.测试结果表明砷和硒在质量浓度分别为0.00μg/L~10.00μg/L和0.00μg/L~40.00μg/L范围内呈线性关系,相关系数分别为(砷r=0.9998,硒r=0.9997)。仪器检出限为砷:0.03μg/L硒:0.05μg/L。本方法检出限砷为0.075μg/L;硒为0.125μg/L。水质样品中砷的回收率为92.6%~96.5%,精密度为0.8%~1.4%;硒的回收率为91.2%~97.4%,精密度为1.0%~1.6%。应用本方法测定生活饮用水中的砷和硒方法简便、快速,结果准确可靠,较好地提高了工作效率。     

磁性多壁碳纳米管固相萃取-气相色谱质谱联用快速测定食用油中的苯并[a]芘

建立以磁性多壁碳纳米管(Fe3O4/MWCNTs)作为磁固相萃取吸附剂,气相色谱-质谱联用检测食用油中苯并[a]芘(Ba P)的方法。实验优化萃取时间、洗脱溶剂的种类和用量、洗脱时间等影响萃取效率的主要参数。最佳样品处理条件为:萃取时间5 min、4 m L甲苯作为洗脱剂超声洗脱3 min。在最佳条件下,该方法具有较高的准确性和灵敏度,其回收率为95.3%~100.5%,检出限(3倍信噪比)为0.15μg/L。检测市售食用油中的Ba P时,实际样品加标回收率为77.2%~89.1%,相对标准偏差为1.1%~6.0%,检出限为0.19%~0.29μg/L,该方法操作简便、耗时短、有毒试剂用量少、准确灵敏。     

HPLC法同时测定季铵盐中氯化苄和苯甲醇

本文提出同时测定季铵盐苄基氯化铵中氯化苄、苯甲醇的新方法。采用高效液相色谱法,以C18(4.6mm×250mm,5μm)为分离柱;磷酸二氢盐—甲醇进行梯度洗脱;检测波长为210nm;柱温为25℃;流速为1.0m L/min。结果表明氯化苄在6.5~130μg/m L(r=0.9998),苯甲醇在6.25~125μg/m L(r=0.9999)浓度范围内呈良好的线性关系,氯化苄和苯甲醇的回收率分别为95.00~102.00%和102.86~105.71%,检出限分别为3.0μg/g、1.5μg/g。该方法操作简单,未用到有毒的试剂,准确性高,是季铵盐原料质量控制的理想方法。     

液相色谱-串联质谱法同时测定饲料中矮壮素和缩节胺的残留

本文采用高效液相色谱-串联质谱(HPLC-MS/MS)同时测定饲料中的矮壮素和缩节胺残留。样品先用正己烷脱除油脂,后用缓冲溶液(含0.2%甲酸-0.05mol/L乙酸铵)提取,离心上清液用乙腈沉淀净化后进行测试。结果表明:两种化合物在1.0~50.0μg/L范围内线性关系良好;定量限(S/N=10)矮壮素为0.32μg/L,缩节胺为0.45μg/L;加标回收率为91.7%~94.3%;相对标准偏差3.9%~6.1%;实测有30%的样品中含有矮壮素或缩节胺,含量范围为:矮壮素11.2μg/kg-78.4μg/kg;缩节胺9.7μg/kg-126.6μg/kg。该方法简便、快速、灵敏和准确,适合饲料中这两种农药残留的快速检测和定量分析。     

气相色谱-质谱法检测牛奶中左旋咪唑残留的研究

目的:建立牛奶中左旋咪唑残留量检测的气相色谱-质谱方法。方法:牛奶样品经乙酸乙酯提取,盐酸反萃取后碱化,三氯甲烷提取液,可供气相色谱质谱联用仪分析。采用Agilent 6890N-5973i气-质谱联用仪,HP-5MS(30m×0.25 mm×0.25μm)毛细管柱,EI离子源,m/z 204、203、148、101选择离子监测,外标法定量。结果:左旋咪唑添加水平为5μg/L、10μg/L、50μg/L时,方法的回收率为76.5%~95.5%,批内批间相对标准偏差为1.4%~12.2%;在浓度为0.05~5μg/m L范围内左旋咪唑色谱峰面积与其质量浓度的线性方程为Y=16130X-164.37,r=0.9997。方法检测限为3μg/kg,定量限可达到10μg/kg。结论:所建立的GC-MS简便、快速,能够满足左旋咪唑残留检测的要求,可作为我国牛奶质量综合监控的有效方法之一,对我国动物性食品中左旋咪唑残留监控具有实际意义。     

啤酒易拉罐中苯酚和双酚A的迁移检测

目的建立一种测定啤酒易拉罐中苯酚和双酚A迁移量的方法,应用于市售易拉罐啤酒污染物的检测。方法选用体积分数为10%的乙醇为食品模拟物,在迁移温度为60℃,迁移时间为10 d的条件下开展迁移研究,采用高效液相色谱-荧光法对迁移样液进行检测。结果在文中的试验方法下,苯酚和双酚A在7 min内可实现完全分离,方法的检出限(LOD)分别为6.0和1.5μg/L。苯酚在20~400μg/L质量浓度范围内线性良好(相关系数为0.9999),双酚A在5~100μg/L质量浓度范围内线性良好(相关系数为0.9998)。通过对空白样品进行加标回收试验,苯酚回收率为90.0%~98.5%,相对标准偏差(RSD)为2.7%~6.2%;双酚A回收率为84.0%~102%,RSD为3.2%~5.3%。将该方法应用于7种易拉罐啤酒中苯酚和双酚A迁移量的检测,结果均未检出苯酚,双酚A检出量在6.9~14.8μg/kg之间。结论该方法准确度高、灵敏度好,能够满足啤酒易拉罐中苯酚和双酚A迁移量检测的要求。     

微波消解-原子荧光光谱法测定中药中的砷和硒

建立了微波消解-原子荧光光谱测定中药中砷和硒含量的方法。该方法测定砷和硒的检出限分别为0.087μg/L和0.123μg/L,荧光强度与砷及硒的质量浓度在0~200μg/L及0~100μg/L范围内呈线性关系。用于中药中砷和硒的测定,相对标准偏差(n=6)均小于3.6%,砷的回收率在95.2%~102.8%之间,硒的回收率在94.5%~104.8%之间。     

液相色谱/串联质谱法测定茄子中5种拟除虫菊酯类农药残留

建立了茄子中5种拟除虫菊酯类农药(氟氰戊菊酯、甲氰菊酯、氯氟氰菊酯、溴氰菊酯和氟胺氰菊酯)残留的液相色谱/串联质谱检测方法。样品以乙腈提取,采用电喷雾正离子源(ESI+)和多重反应监测(MRM)模式测定,基质匹配标准曲线定量。结果表明:茄子基质中,5种拟除虫菊酯类农药峰面积响应值与其质量浓度呈良好线性关系(r0.995)。氟氰戊菊酯、甲氰菊酯、氯氟氰菊酯、溴氰菊酯和氟胺氰菊酯检测方法线性范围分别为8~100μg/L、2~100μg/L、10~100μg/L、4~100μg/L和4~100μg/L,检出限分别为2.52、0.63、3.14、1.26和1.13μg/kg,定量限分别为8.4、2.1、10.4、4.2和3.7μg/kg;5、50和100μg/kg三个添加水平下,5种拟除虫菊酯类农药的回收率在71.7%~91.1%,相对标准偏差为4.9%~9.3%。该法简单、准确、快速、灵敏,符合法规残留限量监测要求。     

高效液相色谱-三重四级杆质谱法测定豆制品中二甲基黄、二乙基黄

建立一种同时测定豆制品中二甲基黄、二乙基黄的高效液相色谱-三重四级杆质谱(HPLC-MS/MS)方法。对提取溶剂及色谱条件进行优化,粉碎后的样品经乙腈提取,提取液以HPLC-MS/MS测定,外标法定量。二甲基黄、二乙基黄在3 min内流出并完全分离,两者在0.05~10μg/L范围内相关系数r2均大于0.999,二甲基黄在0.5~50μg/kg的加标回收率为90.0%~93.4%,RSD为0.5%~5.1%,二乙基黄在0.5~50μg/kg水平的加标回收率在84.6%~93.8%,RSD为1.1%~4.6%,检出限两者均为0.2μg/kg。该方法操作简捷、准确度和精密度高,适用于豆制品中二甲基黄、二乙基黄的检测。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.