A fully automated system with on-line micro solid-phase extraction combined with capillary liquid chromatography-tandem mass spectrometry for high throughput analysis of microcystins and nodularin-R in tap water and lake water

Microcystins and nodularins are cyclic peptide hepatotoxins and tumour promoters from cyanobacteria. The present study describes the development, validation and practical application of a fully automated analytical method based on on-line micro solid-phase extraction-capillary liquid chromatography-tandem mass spectrometry for the simultaneous determination of seven microcystins and nodularin-R in tap water and lake water. Aliquots of just 100 μL of water samples are sufficient for the detection and quantification of all eight toxins. Selected reaction monitoring was used to obtain the highest sensitivity. Good linear calibrations were obtained for microcystins (50-2000ng/L) and nodularin-R (25-1000 ng/L) in spiked tap water and lake water samples. Excellent interday and intraday repeatability were achieved for eight toxins with relative standard deviation less than 15.7% in three different concentrations. Acceptable recoveries were achieved in the three concentrations with both tap water matrix and lake water matrix and no significant matrix effect was found in tap water and lake water except for microcystin-RR. The limits of detection (signal to noise ratio=3) of toxins were lower than 56.6 ng/L which is far below the 1 μg/L defined by the World Health Organization provisional guideline for microcystin-LR. Finally, this method was successfully applied to lake water samples from Tai lake and proved to be useful for water quality monitoring.     

Development of a static and exhaustive extraction procedure for field passive preconcentration of chlorophenols in environmental waters with hollow fiber-supported liquid membrane

A static and exhaustive extraction mode of hollow fiber-supported liquid membrane was developed for field sample passive pretreatment of environmental water samples. The extraction device was prepared by immobilizing dihexyl ether in the wall of a polypropylene hollow fiber membrane (60 cm length, 50 μm wall thickness, and 280 μm id) as liquid membrane and filling the fiber lumen with 0.1 M NaOH as acceptor, and closing the two ends of the fiber with an aluminum foil. Passive extraction was conducted by immersing the device into 15 mL water samples modified with 0.01 M HCl and 20% m/v NaCl. Model analytes including 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol were transferred into acceptor with extraction efficiencies over 79% in 10 h at room temperature, and determined by high-performance liquid chromatography. The proposed method has the enrichment factor of 394-498 and LOD of 0.3-0.4 μg/L for the three chlorophenols. Humic acid and salinity in the environmentally relevant range had no significant influence on the extraction, and chlorophenols in various environmental waters were determined with spike recoveries between 71.6 and 120%. The static passive extraction nature benefited field sample pretreatment without power, whereas the exhaustive extraction mode effectively eliminated the sample matrix effects.     

电磁力诱导二次流对微流体混合效果影响的研究

设计了一种微流道中液体混合的方法, 基于电磁力的作用, 诱导微流道中二次流动 发生, 从而产生Dean涡, 使流道中流体出现往复运动及流体界面的弯曲延伸, 使不 同流体的接触面积大大地增加, 从而提高混合效率. 对3种结构的工况进行了比较. 建立了微流道混合系统的理论模型并进行了数值模拟,对流体混合过程进行了分析并对混合效率进行了评价. 进行了验证性的试验研究, 对模拟结果与试验结果进行了比较, 结果相吻合.     

一种免装配微惯性测量单元的研制与开发

以柔性材料和高精度六面体作为惯性传感器的安装载体和基准,设计了一种免装配、安装误差小、体积小、功耗低且便于标定的微惯性测量单元。给出了安装误差小角度前提下的传感器的测量方程和标定方法;利用微控制器的并行工作机制,提出了一种快速有效的基于均值滤波和FIR滤波的组合滤波方案。实验结果表明:MIMU可以100 Hz的频率更新测量输出,加速度测量噪声小于2.5 mg、测量误差小于0.8 mg,旋转角速度测量噪声小于0.15 o/s、测量误差小于0.2 o/s,可满足微小型惯性导航系统的功耗、体积、测量精度和响应速度的应用需求。     

振动钻削微小孔中钻头寿命与振动参数的二次回归试验研究

本文采用正交组合设计的试验方法，对振动钻削微小孔加工中钻头寿命与轴向振动参数之间的非线性关系进行了二次回归试验，得到了最优回归方程。用回归方程给出的最佳振动参数钻孔，钻头寿命提高了９６．３％     

Solid phase microextraction using fused silica fibers coated with graphitized carbon black

Summary This paper presents the results obtained using fused-silica fibers coated with graphitized carbon black (Carbograph-Alltech) for solid-phase microextraction (SPME). The extraction and calibration curves relative to organic micro-pollutants present in gaseous and aqueous samples are reported. Examples of applications of this extraction procedure to GC and GC-MS analysis of organic micro-pollutants in actual samples are also reported.     

微流量输液泵

对近几年出现的以声、光、电、磁、热等为基本激发形式的新颖的微流量输液泵的原理、特点作了评述。     

Hybrid Comminution with High‐Pressure Roller and Stirred Bead Milling

This paper presents the experimental results on the wet grinding of a moist calcium carbonate material in a hybrid comminution system, which consists of a high pressure roller mill (HPRM) and a subsequent stirred bead mill. The results show that the pre‐treatment of the material with the HPRM could result in energy saving and efficient size reduction during the subsequent wet ultra‐fine grinding in the stirred bead mill. It was found that the level of fineness of the ground product is dramatically influenced by the number of repeat passes of pre‐grinding in the HRPM. The formation of micro‐cracks in the particles under compressive loads was discussed in order to elucidate the role of the HRPM as a pre‐grinder in the hybrid comminution system. The simulated breakage behaviors of various irregular shaped particles indicate that the tortuous micro‐crack propagation paths and the crack branching behavior are related to the heterogeneity of the particle and the stress distributions.     

W/O型乳胶粒子表面电性的近代测试技术

采取近代表面电学测试技术对乳胶粒子表面电性进行微观测量，取得了一系列反映胶粒表面双电层结构的特征参量，证明表面扩散双电层的存在。为完善W／O型乳胶体系的稳定性理论提供了一定实验依据。     

Cracking in polylactide spherulites

A polylactide of high optical purity was crystallized between 100 and 140 °C, in‐between two glass slides, and its morphology was investigated by polarizing optical microscopy, scanning electron microscopy, and atomic force microscopy, during subsequent heating and cooling cycles between ?15 °C and the crystallization temperature. It was found that dark circular rings show up on cooling on top of the spherulites and represent cracks of about 300 nm in width. This phenomenon is completely reversible, and the heating–cooling curves are centered at about 56 °C, which coincide with the T_g of polylactide. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3308–3315, 2005