超高效液相色谱-串联质谱法测定人尿液中全氟有机化合物

采用超高效液相色谱-串联质谱(UPLC-MS/MS)联用技术,建立了对人尿液中12种全氟有机化合物(PFCs)的分析方法。首先在尿液样品中加入相应的同位素内标,以2%(体积分数)甲酸甲醇溶液超声萃取、离心后,将提取液用弱阴离子交换固相萃取柱净化,采用UPLC-MS/MS测定,内标法定量。12种目标化合物在0.05～50 μg/L质量浓度范围内线性良好,相关系数(r)均大于0.992,检出限在0.44～3.47 ng/L之间。在20、100、500 ng/L添加水平下,平均回收率范围为80.3%～116.2%,相对标准偏差(n=6)在5.5%～13.8%之间。该方法灵敏度高、重现性好、回收率高、操作简单,适合人尿液中PFCs的测定。     

超高效液相色谱-质谱法比较黑顺片单煎液及其复方煎煮液中次乌头碱在大鼠体内的吸收

为了研究有毒中药中主要成分的体内吸收,以黑顺片单煎液及其复方煎煮液“术附汤”和“甘草附子汤”灌胃大鼠血浆中的次乌头碱为检测指标,建立了血浆中次乌头碱的超高效液相色谱-四极杆飞行时间质谱(UPLC/Q-TOF MS)检测方法,并采用内标法对其进行了含量测定,绘制了血药浓度-时间曲线,计算了药动学参数。方法学考察结果表明血中次乌头碱在0.02～10 ng/mL范围内呈现良好的线性关系;样品测定结果表明,“术附汤”中的某种或某些成分抑制了次乌头碱的体内吸收,而“甘草附子汤”中的某种或某些成分促进了次乌头碱的体内吸收,两复方功效差异可能来源于次乌头碱在体内吸收程度的不同。由3种煎煮液中次乌头碱的消除半衰期(T1/2)及血药浓度-时间曲线下面积(AUC)值推测次乌头碱在大鼠体内的转运过程为非线性动力学过程。     

超高效液相色谱串联质谱法测定鱼组织中6种抗雌激素药物

采用超高效液相色谱-串联质谱(UPLC-MS/MS)在多反应监测(MRM)模式下建立了鱼肉、鱼肝中6种抗雌激素类药物(托瑞米芬、氯米芬、他莫昔芬、雷洛昔芬、阿那曲唑、来曲唑)的检测方法。样品采用乙腈超声提取,上清液中加入适量水稀释提取液,经混合型阳离子交换(MCX)固相萃取柱富集、净化后进行UPLC-MS/MS分析。UPLC分离在ACQUITY UPLCTM BEH C18柱(100 mm×2.1 mm, 1.7 μm)上进行,以乙腈和0.1%甲酸水溶液为流动相进行梯度洗脱。6种抗雌激素药物的定量限(以信噪比为10计)为0.1～0.3 μg/kg; 4个加标水平的平均回收率为84.9%～112.2%,相对标准偏差为0.9%～14.3%。该方法可用于鱼肉、鱼肝中6种抗雌激素药物的痕量分析。     

超高效液相色谱-电喷雾三重四极杆质谱法测定中药中马兜铃酸A和B的含量

利用超高效液相色谱-电喷雾三重四极杆质谱仪建立了中药中马兜铃酸A和B的定性定量分析方法。选取柴胡、生甘草、桔梗、龙胆泻肝丸、消胖丸、减肥茶等14种代表性样品,用甲醇-水(70:30, v/v)溶液加热回流提取,经Oasis MAX固相萃取柱富集净化后,在Eclipse RP HD C18反相柱(150 mm×2.1 mm, 1.8 μm)上进行分离;流动相为5 mmol/L乙酸铵水溶液(pH 7.5)-乙腈(75:25, v/v)。采用电喷雾离子源正离子模式(ESI+)和多反应监测模式(MRM)进行质谱分析。马兜铃酸A和B的线性范围分别为0.5～200 μg/L和1～200 μg/L,相关系数(r2)均大于0.995;检出限(LODs)分别为5 μg/kg和7.5 μg/kg;定量限(LOQs)分别为12.5 μg/kg和25 μg/kg。在100 μg/kg和500 μg/kg添加水平下,马兜铃酸A和B的回收率(n=6)范围分别为60.3%～96.4%和61.3%～94.7%,相对标准偏差均不大于10.2%。该方法灵敏度高,重复性好,操作简便,适用于中药材、饮片及中成药中马兜铃酸A和B的痕量检测。     

Liquid phase microextraction applications in food analysis

Over the last years, liquid-phase microextraction (LPME) in its different application modes (single drop microextraction, dispersive liquid-liquid microextraction and hollow fiber-LPME) has been increasingly applied for the extraction of both inorganic and organic analytes from different matrices. Its advantages over conventional extraction procedures (simplicity, effectiveness, rapidity and low consumption of organic solvents) has also attracted its application in the complex food analysis field, in which it has clearly provided good and challenging results. A comprehensive review dealing with those articles published since its introduction till the end of March 2011 is presented, offering also a critical vision of the analytical potential of LPME for the analysis of foods.     

Higher order log-concavity in Euler’s difference table

For 0≤k≤n, let be the entries in Euler’s difference table and let . Dumont and Randrianarivony showed equals the number of permutations on [n] whose fixed points are contained in {1,2,…,k}. Rakotondrajao found a combinatorial interpretation of the number in terms of k-fixed-points-permutations of [n]. We show that for any n≥1, the sequence is essentially 2-log-concave and reverse ultra log-concave.     

Modification of microstructures and physical properties of ultra high molecular weight polyethylene by electron beam irradiation

An ultra high molecular weight polyethylene was irradiated with the electron beam at dose levels ranging from 100 kGY to 1 MGy. The microstructures of the irradiated samples were characterized by FTIR, gel fraction measurement, DSC, and small‐ and wide‐angle X‐ray scattering. For the mechanical properties, a static tensile test and creep experiment were also performed. The crosslinking and the crystal morphology changes were the main microstructural changes to influence the mechanical properties. It was found that 250 kGy appeared to be the optimal dose level to induce crosslinks in the amorphous area and recrystalliztion in the crystal lamellae. At doses above 250 kGy, the electron beam penetrates into the crystal domains, resulting in crosslinks in the crystal domains and reduction in the crystal size and crystallinity. The static mechanical properties (modulus, strength) and the creep resistance were enhanced by the electron beam irradiation. The stiffness rather correlated with the degree of crosslinks while the strength with the crystal morphology. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3019–3029, 2005     

Laser Based Techniques for Ultra Trace Isotope Production, Spectroscopy and Detection

A variety of research activities in the field of fundamental and applied nuclear physics has evolved in the last years using resonantly tuned radiation from powerful lasers. The technique of resonance ionization spectroscopy has delivered outstanding results and found broad acceptance in the last years as a particularly efficient and highly selective method for rare and exotic radioisotope studies. It is used for production, spectroscopy and detection of these species and provides complete isobaric, high isotopic and even some isomeric selection, which altogether is needed for on-line investigation of short lived species far off stability as well as for ultra trace determination. Good overall efficiency pushes the experimental limits of detection in elemental trace analysis down to below 10⁶ atoms per sample, and additionally isotopic selectivity as high as 3 × 10¹² has been demonstrated. The widespread potential of resonance ionization techniques is discussed, focusing on the experimental arrangements for applications in selective on-line isotope production, spectroscopy of rare radioisotopes and ultra trace determination of radiotoxic isotopes like ²³⁸Pu to ²⁴⁴Pu, ^135,137Cs, ^89,90Sr or ⁴¹Ca in environmental, technical and biomedical samples.     

超微弱发光图像的统计处理方法

应用超高灵敏度的光电成像系统，获得了活体昆明鼠的超微弱生物发光图像，并用概率统计理论研究了光子图像中的光子频数分布，得到了一种去除噪声的原则。文中首次提出了用Ｘ＾２准则拟合实际图像中的信号区和背景区分布，并根据得到的统计估计值对光子图像进行处理的方法，该法对实验获得的昆明鼠的超微弱生物发光有较好的处理效果，提高了图像的信噪比，得到了好的观察效果。     

Detection and analysis of radio pulses from extensive air showers

Radio pulses from extensive air showers (EAS) at 30, 44, and 60 MHz frequencies have been studied, using wide band broad-side arrays of half-wave dipole antenna systems. The experimental results support the theoretical prediction that the field strength of radio emission depends on the shower size. An asymmetry has been noticed in the pulse height distributions of radio pulses detected by North-South and East-West directed arrays. These observations are in agreement with the theory that the charge separation mechanism is predominant in generating radio pulses from EAS and radio emission is polarised in the East-West direction. Experimental data are compared with those of earlier workers.