高效液相色谱法测定桶装水及水桶中双酚A含量

该文建立固相萃取/高效液相色谱测定桶装水及水桶中双酚A含量的方法。桶装水样品经C18固相萃取柱富集,水桶用二氯甲烷溶解甲醇提取双酚A;采用C18色谱柱,以乙腈-水(V/V,60:40)为流动相,检测波长224 nm,高效液相色谱法测定双酚A含量。在最优检测条件下,双酚A在0.4～10μg/mL浓度范围内线性关系良好(r2=0.999 8),方法的检出限为0.069μg/mL,定量限为0.23μg/mL,平均回收率为98.3%。该方法简便、灵敏、重现性好,所抽取桶装水中并未检测到双酚A的存在,水桶材质中检测出双酚A的含量为37.1μg/g。     

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。     

双酚S迁移量的快速检测及迁移规律研究

目的研究聚醚砜中双酚S迁移量的快速检测方法,以及双酚S的迁移规律。方法以液相色谱-质谱法(LC-MS)快速测定模拟液乙醇(体积分数为50%)、乙酸(质量浓度为30 g/L)及水中双酚S的迁移量,并以此为基础,研究不同的介质、温度、时间、厚度等因素对双酚S迁移规律的影响。结果该法对双酚S的检出限为2.0μg/L,定量限为6.0μg/L,在模拟液水、乙醇(体积分数为50%)、乙酸(质量浓度为30 g/L)中的加标回收率分别为95.2%~102%,97.3%~102%,96.3%~102%,相对标准偏差分别为2.6%~4.2%,2.6%~4.0%,3.3%~4.7%;在相同条件下,双酚S在乙醇(体积分数为50%)中的迁移量最大,其迁移量顺序为乙醇(50%)乙酸(30 g/L)水,同时符合温度越高则迁移量越大、厚度越大迁移量越高的规律。结论采用液相色谱-质谱法检测双酚S,具有操作简便、灵敏度高、重复性好、结果准确等特点;食品模拟物的属性是影响双酚S迁移行为的重要因素,同时,温度和厚度也影响着双酚S在PES中的迁移。     

北京市售桶装饮用水中双酚A的污染水平

目的建立定量分析桶装饮用水中双酚A的方法,研究北京市桶装饮用水中双酚A的污染水平。方法采用固相萃取技术进行样品前处理,运用液相色谱?质谱联用法进行样品检测。结果在质量浓度为122.9~1190.7 ng/L范围内,在最优的质谱检测条件下,一级质谱的线性回归方程为y=69.4x+2186.1,相关系数为0.993,检出限为7.0 ng/L,定量限为23.5 ng/L。方法的回收率为78.8%~108.1%,相对标准偏差(n=6)≤13.5%。在随机检测的北京市6个水站的53种桶装饮用水中有36种检出双酚A,但浓度均低于《生活饮用水卫生标准》(GB 5749—2006)中规定的双酚A限值(0.01 mg/L)。结论该方法选择性好、灵敏度高、重现性好,能够满足定量检测桶装饮用水中双酚A的要求。北京市售桶装水中较为普遍地存在双酚A,长期饮用有健康风险。     

同位素内标-UPLC-MS/MS法检测易拉罐啤酒中双酚A含量

目的 为了提高金属易拉罐啤酒中双酚A(BPA)的检测能力,建立一种基于同位素内标的超高效液相色谱-串联质谱分析方法。方法 样品经超声处理后除去CO2,随后添加内标物BPA-¹³C12,用超高效液相色谱-串联质谱法进行检测分析,采用内标法定量。结果 经同位素内标标准曲线校正,方法的定量限为1.00 μg/L,线性方程为y=1.73x+0.206,线性相关系数为0.9992,相对标准偏差为4.68%～6.63%,加标回收率为91.0%～109%。使用该方法对厦门市市售6种易拉罐啤酒样品进行了BPA污染物迁移量检测,结果显示6种啤酒中均检出BPA,平均质量浓度为1.48 μg/L。结论 此方法具有前处理简便快捷、检测限高、灵敏度高、准确度好等特点,能够满足金属易拉罐啤酒中低含量BPA的检测要求。     

高效液相色谱-荧光检测法检测金属食品罐用涂料中的双酚 A 含量

建立了一种高效液相色谱-荧光检测法测定金属食品罐用涂料中双酚 A 的定量分析方法。 样品用甲醇超声提取,双酚 A 在质量浓度为 0. 1 ~20. 0 μg/ mL 范围内,峰面积与质量浓度具有良好的线性关系,线性方程为 y=19. 241x+2. 7916,相关系数为 0. 9985,检测限为 0. 05 μg/ mL,回收率为 95. 0% ~100. 9% 。 分析比较了不同厂家和不同批号涂料中双酚 A 的含量。 研究表明,该方法灵敏可靠,准确度高,适用于定量检测金属食品罐用涂料中的双酚 A。     

水中甲萘威高效液相色谱测定方法研究

建立水中甲萘威含量检测的高效液相色谱分析方法。使用乙酸乙酯作为液液萃取预处理方式的萃取剂,萃取水样中的甲萘威。萃取液氮吹浓缩后定容在甲醇中。富集后的样品使用高效液相色谱法分析,以甲醇/水作为流动相(体积比:55/45)使用XTerra MS C18色谱柱(4.6mm×150mm×5μm)分离。选取280nm作为紫外检测器的吸收波长。并对测试方法的线性方程、检出限、精密度和加标回收率进行实验。结果表明,甲萘威在0.10~3.00μg/mL的浓度范围内线性关系良好。当水样萃取体积为100mL时,检出限0.22μg/L,平均回收率为89.0%,RSD在3.2%~6.8%之间。该方法快可以捷准确的检测水中的甲萘威,灵敏度高。使用乙酸乙酯作为萃取剂可提高样品中甲萘威的回收率,同时减少毒性大的有机溶剂的使用。     

超高效液相色谱法测定食品包装材料中的富马酸二甲酯

提出了内标法结合超高效液相色谱法测定食品包装材料中富马酸二甲酯的方法。以包装企业自送的4种包装材料为例,讨论了用超高效液相色谱进行富马酸二甲酯测定的过程。该方法的检出限为10μg/kg,加标回收率在76%～98%之间,相对标准偏差在1.2%～4.1%之间。实验结果表明,用溶剂萃取结合超高效液相色谱能够满足日常进出口食品包装材料中富马酸二甲酯的检测。     

食品包装塑料中双酚F和双酚S迁移量测定的优化及分析

目的 优化液相色谱串联质谱测定塑料制品中双酚F和双酚S迁移量的方法。方法 通过色谱条件及质谱条件的优化,迁移实验所得食品模拟物经C18柱分离、甲醇-氨水洗脱、多反应模式监测、外标法定量。结果 优化条件下,双酚F和双酚S线性关系良好,水基模拟物的检出限为4μg/L和0.2μg/L、定量限为10μg/L和0.5μg/L,油基模拟物的检出限为20μg/kg和1μg/kg、定量限为50μg/kg和2.5μg/kg,回收率为89.2%～105.5%,RSD值为1.42%～6.18%。结论 该法准确、灵敏,适用于食品包装塑料双酚F和双酚S迁移量的测定。     

液相色谱-串联质谱法测定饮用水中的丙烯酰胺

建立了用液相色谱-串联质谱法测定饮用水中丙烯酰胺的方法。该法使用Cole-Parmer PTFE滤膜过滤样品,采用Acquity HSS T3(1.8μm,2.1X50mm)柱分离,以0.1%甲酸和甲醇为流动相(体积比95:5)分离。采用UPLC/MS/MS电喷雾电离正离子模式(ESI+),多反应检测(MRM),以外标法定量分析。该方法在0.10μg/L到0.60μg/L有良好线性范围。最低检测下限(LOD)0.10μg/L。加标回收率范围为88.9%-106.7%。相对标准偏差均低于8.2%。方法适用与水中丙烯酰胺的测定,具有灵敏度高、重现性好的特点,在水质监测中有重要作用。     

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.     

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.     

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.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.