固相萃取-气相色谱-质谱法测定鸡蛋中160种农药残留

建立了串联组合柱固相萃取-气相色谱-质谱法检测鸡蛋中160种农药多残留的分析方法。鸡蛋样品用乙腈均质和超声波提取,提取液采用C18和PSA串联组合柱净化,气相色谱-质谱仪(GC-MS)分析。GC-MS采用SIM模式,外标法定量。在优化过的条件下进行测试,本法检出限(S/N≥3)为0.01~0.05 mg/kg,在加标水平为0.05 mg/kg时,方法回收率为63.2%~126%,相对标准偏差为2.3%~13%。     

SPE-GC-ECD法测定塑料食品包装材料中的短链氯化石蜡

目的建立固相萃取-气相色谱法(SPE-GC-ECD)测定塑料食品包装材料中7种短链氯化石蜡(SCCPs)的检测技术。方法利用丙酮和正己烷的混合溶液在50℃下超声萃取塑料食品包装材料中7种SCCPs成分,SCCPs经硅胶固相萃取柱净化,采用气相色谱-电子捕获检测器进行定性与定量测定。结果在0.1~100.0 mg/kg范围内,SCCPs质量浓度与色谱峰面积呈良好的线性关系,线性相关系数均大于0.9997;检出限为0.01~0.10 mg/kg,加标回收率为86.4%~102.7%,相对标准偏差为1.2%~3.7%。结论该方法准确度高、精密度好、检出限低,可为塑料食品包装材料中SCCPs的检测提供新方法。     

QuEChERS提取-气相色谱法测定木棉花中有机磷类残留

建立同时测定木棉花中9种有机磷农药的Qu ECh ERS提取-气相色谱快速检测方法。样品经乙腈溶解,Qu ECh ERS试剂萃取,分散固相萃取净化后,气相色谱-火焰光度检测器检测,在优化条件下,结果显示:9种农药均具有良好的线性关系,相关系数不低于0.995,检出限为0.012~0.316mg/kg,加标回收率为81.6%~103.4%,相对标准偏差为1.6%~4.8%。该方法具有检测结果准确可靠、简便快速等优点。     

分散固相散萃取_气相色谱法测定鱼肉中9种有机磷农药残留

建立了同时检测鱼肉中9种有机磷类农药残留的分散固相萃取-气相色谱联用方法。样品经乙腈进行提取,PSA、GCB和C18进行分散固相萃取净化,结合气相色谱法定性定量分析。添加样品的回收率为70.1%~80.4%,相对标准偏差在5.0%~10.2%,方法最低检出限为0.005~0.01 mg/kg。该法简便、准确,适用于鱼肉中9种有机磷农药残留量的检测。     

固相萃取-气相色谱-质谱联用法检测进出口蔬菜产品中百菌清残留

建立了固相萃取-气相色谱-质谱法检测蔬菜中百菌清残留的分析方法。样品用乙腈-水-磷酸混合液提取,经液液分配、Florisil/Na2SO4柱净化后过滤膜上机。采用选择离子扫描方式,外标法定量。通过优化前处理和上机条件,在最优条件下进行测试,实验结果百菌清的定量检出限为0.001mg/kg,在加标水平0.005～0.1mg/kg范围内,回收率为78.65%～90.67%,相对标准偏差为3.5%～5.8%。该方法简便、快速、净化效果理想,能满足残留分析的要求,可用于进出口蔬菜中百菌清残留的检测。     

加速溶剂萃取气相色谱-质谱法检测土壤中双酚A

建立加速溶剂萃取后利用气相色谱-质谱法测定土壤中双酚A的检测方法。样品前处理采用加速溶剂萃取,经硅胶柱净化,以HP-5MS色谱柱,采用气相色谱-质谱联用全扫描和选择离子扫描进行分析。结果表明:双酚A在0.1~10.0 mg/L的质量浓度范围内,线性良好,相关系数为0.999 3;方法检出限为0.01 mg/kg(S/N=3)。在0.1,1.0,10 mg/kg这3个加标水平下,样品的平均回收率为82.5%~101.7%,相对标准偏差(RSD)≤3.3%。该方法简便快速,灵敏度及准确度高,可用于土壤中双酚A的分析测定。     

固相萃取-超高效液相色谱法测定化妆品中6种硝基酚

建立了同时测定化妆品中6种硝基酚的固相萃取-超高效液相色谱分析方法。样品采用乙腈为提取溶剂,经超声提取后再做高速离心处理;上清液以Oasis HLB固相萃取柱净化,收集甲醇洗脱液,采用色谱分析。液相色谱分析方法:选择全氟苯基色谱柱,以乙腈和乙酸铵及0.1%甲酸作为流动相,梯度洗脱,检测波长为220nm,在优化的固相萃取前处理和液相色谱分离分析条件下,净化效果满足要求。6种硝基酚类化合物在20min内实现完全基线分离,检出限为0.02~0.04mg/L,回收率为86.3%~103.6%,相对标准偏差为3.4%~7.1%。本方法准确、快速、灵敏度高,可用于化妆品的实际检验。     

超声波提取-气相色谱-质谱法测定塑料食品接触材料中的乙二醇醚及其酯类

本文建立了采用超声波提取-气相色谱-质谱联用检测塑料食品接触材料中的乙二醇醚及其酯类的方法。通过以甲醇为溶剂,超声波萃取乙二醇醚及其酯类,固相硅胶小柱净化,气相色谱-质谱联用仪测定,外标法定量,该方法检测低限在20mg/kg,加标回收率在80%~95%之间,相对标准偏差(RSD)不大于6%,线性范围在10mg/L~1000mg/L,相关系数(r)大于0.999。实验结果表明方法简便、可靠,能满足塑料食品包装材料中的乙二醇醚及其酯类的检测要求。     

固相萃取-气相色谱法测定葡萄酒中16种有机磷农药残留

利用固相萃取(SPE)/气相色谱火焰光度(GC-FPD)技术建立了葡萄酒中16种有机磷农药残留量分析方法。样品加水稀释,过HLB小柱和LC-NH2小柱净化,浓缩、定容后,用气相色谱测定,外标法定量。各农药的方法定量限(LOQ)均为为0.01 mg/kg。添加回收实验,16种有机磷农药添加浓度为0.01-0.10 mg/kg时,添加回收率为65.3-92.3%,变异系数≤10%。     

大体积水样专用柱固相萃取-超高效液相色谱串联质谱测定水中5类40种抗生素类药物残留

目的:建立大体积水样专用柱固相萃取柱富集净化-超高效液相色谱-串联质谱(LC-MS/MS)法,同时测定水体中5类40种抗生素。方法:水样通过大体积水样专用柱萃取富集后,用5%氨化甲醇洗脱,以C18反相色谱柱为分析柱,乙腈-0.1%甲酸溶液为流动相,采用LC-MS/MS进行定性定量分析。选择电喷雾正电离源(ESI+),多反应监测模式(MRM),外标法定量。结果:5类40种抗生素在1~500 ng/L范围内均具有良好的线性关系,方法的检出限(S/N=3,1000倍浓缩)为0.1~10 ng/L。以自来水、闽江水和内河水作为基底,加标质量浓度为40 ng/L和100 ng/L时,抗生素的平均加标回收率分别为68.0%~120.3%和67.9%~117.7%,相对标准偏差(RSD)分别为2.0%~14.9%和1.8%~16.6%。结论:建立的大体积水专用柱固相萃取净化、富集,超高效液相色谱-串联质谱(LC-MS/MS)联用技术,可用于测定同时测定水体中5类40种抗生素。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。