Structure and wettability relationship of coelectrospun poly (L‐lactic acid)/gelatin composite fibrous mats

Coelectrospun polylactide(PLA)/gelatin (GE) composite fibrous matrixes have been identified to exhibit much improved performances compared to the respective components; however, the reasons for their water contact angles decreasing to zero at proper PLA/GE ratios remain unclear. To get a deep understanding of the phenomenon, PLA and GE were coelectrospun with different PLA/GE ratios in this study. Although the resulting composite fibers were homogeneous in appearance, they were detected different microscopic structures by transmission electron mircroscope (TEM) and via morphological observations after selective removal of either PLA or GE component. Together with the results of degradation study in phosphate buffered solution, a kind of cocontinuous phase separation microstructure could be identified for the PLA(50 wt%)/GE(50 wt%) composite fibers, which also showed the water contact angle of 0°. This value was far lower than those of electrospun PLA (～123°) and GE (～42°) fibrous matrixes. The X‐ray photoelectron spectrometry (XPS) data revealed that the polar side groups of protein macromolecules have moved toward composite fiber surface with solvent evaporation during electrospinning, due to the hydrophobic interaction between PLA and GE. Then the excellent hydrophilicity of PLA(50 wt%)/GE(50 wt%) composite fibers could be suggested as the consequence of: (1) the cocontinuous phase separation structure could provide more interface and void for water molecules penetrating; and (2) the accumulation of polar groups on composite fiber surface significantly increased the surface wettability. Copyright © 2010 John Wiley & Sons, Ltd.     

PAN基活性炭纤维的表面及其孔隙结构解析

通过氮吸附等温线、X射线光电子能谱以及扫描电子显微镜（SEM）对聚丙烯腈（PAN-Polyacrylonitrile）-基活性炭纤维（ACF-Activated Carbon Fiber）的表面和孔隙结构进行了分析,结果表明吸附测量可以提供有关碳质吸附剂的孔结构复杂性;通过XPS对PAN基ACF的表面官能团的种类及含量进行了表征,由SEM对PAN基ACF的表面以及断面的孔隙结构进行了直接观察,提供了有关孔隙结构的直接证据。     

Simultaneous determination of phthalates and adipates in human serum using gas chromatography–mass spectrometry with solid‐phase extraction

A gas chromatography–mass spectrometry assay was developed and validated for the simultaneous determination of phthalates and adipates in human serum. The phthalates and adipates studied were dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzylbutyl phthalate, di‐2‐ethylhexyl phthalate, di‐n‐octyl phthalate, diethyl adipate, dibutyl adipate, diisobutyl adipate, bis(2‐butoxyethyl) adipate and di‐2‐ethylhexyl adipate, with diisooctyl phthalate as internal standard. The extraction and cleaning up procedure was carried out with solid‐phase extraction cartridges containing dimethyl butylamine groups, which showed extraction efficiencies over 88% for each analyte and the internal standard. The calibration curves obtained were linear with correlation coefficients greater than 0.98. For all analytes, the assay gave CV% values for intra‐day precision from 4.9 to 13.3% and mean accuracy values from 91.4 to 108.4%, while inter‐day precision was 5.2–13.4% and mean accuracy 91.0–110.2%. The limits of detection for the assay of phthalates and adipates were in the range 0.7–4.5 ng/mL. The method is simple, sensitive and accurate, and allows for simultaneous determination of nanogram levels of phthalates and adipates in human serum. It was successfully applied to an investigation on the level of phthalates and adipates in a non‐occupationally exposed population.     

驱油体系化学剂间相互作用对界面吸附膜的影响

采用界面张力弛豫技术研究了不对称Gemini表面活性剂C12COONa-p-C9SO3Na、部分水解聚丙烯酰胺Mo-4000、疏水缔合水溶性聚丙烯酰胺(HMPAM)等驱油体系化学剂在癸烷/水界面上的扩张流变性质,考察了不同离子强度、不同类型电解质对体系界面流变性质的影响,计算得到界面扩张弹性模量和粘性模量的全频率谱,并通过归一化方法(cole-cole图)探讨了界面吸附膜的弛豫过程。研究发现,界面膜内分子重排和界面与体相间分子扩散交换是影响膜性质的主要弛豫过程。表面活性剂体相浓度增大有利于界面分子重排过程,而低频有利于扩散交换过程;不同结构聚合物以及不同离子强度、不同类型电解质对表面活性剂吸附膜有不同的影响。     

Formaldehyde removal by Rayon-based activated carbon fibers modified by <Emphasis Type="Italic">P</Emphasis>-aminobenzoic acid

We impregnated Rayon-based activated carbon fibers (ACFs) by p-aminobenzoic acid (PABA) and systematically investigated their porous structure, surface chemistry, and formaldehyde removal behavior. Using standard nitrogen adsorption analysis, we found that the specific surface area, the micropore volume, and the total pore volume decreased with increasing concentration of PABA. Through elemental analysis and X-ray photoelectron spectroscopy, it was found that some nitrogen-containing functional groups presented on the surface of modified Rayon ACFs. The modified Rayon-based ACFs showed much higher adsorption capacity and longer breakthrough time for formaldehyde than did as-prepared Rayon-based ACF. We proposed that the improvement of formaldehyde removal by modified ACFs was attributed to the combined effects of physisorption contributed by pore structures and chemisorption contributed by the N-containing functional groups, whereas there was only physisorption between the as-prepared ACF and formaldehyde molecules.     

GPC-多检测联用技术测定聚己内酯分子量及其分布

介绍一种用于生物可降解高分子材料聚已内酯(PCL)及其改性高分子的分子量和分子量分布测定的GPC-示差折光(RI)-示差黏度(DV)-直角光散射(RALLS)多检测联用技术.叙述了该方法的实验原理,并对测试过程中的有关技术及实验结果进行了讨论.该方法可准确测定聚己内酯(PCL)及其改性高分子的分子量及其分布、特性黏度分布、Mark-Houwink方程系数以及高分子尺寸等重要参数.通过对窄分布PS标样验证,分子量测定结果的相对误差在1%之内.     

毛细管电泳和毛细管电色谱技术在农药残留检测中的应用

由于毛细管电泳（CE）和毛细管电色谱（CEC）具有所需样品体积小、分离效率高等特点,越来越多的学者已将它们应用到农药残留（简称农残）检测中,并将它们同各种不同的检测器以及样品浓缩方法相结合,以提高检测的灵敏度。本文对CE和CEC两种方法中所涉及的常见的样品预浓缩方法进行了简要的介绍。对各种不同类型的检测器（如紫外检测、荧光检测、电化学检测以及质谱检测等）的优缺点及其在农残检测中的应用情况进行了评述;同时对手性农药的CE和CEC分离检测情况进行了特别介绍;并对CE和CEC在农残分析与检测中的应用前景进行了展望。     

Simulating water with the self-consistent-charge density functional tight binding method: from molecular clusters to the liquid state

The recently developed self-consistent-charge density functional tight binding (SCCDFTB) method provides an accurate and inexpensive quantum mechanical solution to many molecular systems of interests. To examine the performance of the SCCDFTB method on (liquid) water, the most fundamental yet indispensable molecule in biological systems, we report here the simulation results of water in sizes ranging from molecular clusters to the liquid state. The latter simulation was achieved through the use of the linear scaling divide-and-conquer approach. The results of liquid water simulation indicate that the SCCDFTB method can describe the structural and energetics of liquid water in qualitative agreement with experiments, and the results for water clusters suggest potential future improvements of the SCCDFTB method.