共查询到20条相似文献,搜索用时 125 毫秒
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固相萃取技术在食品痕量残留和污染分析中的应用 总被引:3,自引:0,他引:3
食品痕量残留和污染分析中,样品的前处理极为重要,也是其难点所在。由于食品和农产品样品的多样性和复杂性,目前还没有一种前处理技术能够适合所有情况下的所有样品。本文对近年来发展起来的新型固相萃取技术如固相微萃取、搅拌棒吸附萃取、基质固相分散萃取、分子印迹固相萃取、免疫亲和固相萃取、整体柱固相萃取、碳纳米管固相萃取等在食品痕量残留和污染分析中的应用进行了综述,对未来的发展前景作了展望。 相似文献
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作为一种新型非金属材料,石墨相氮化碳以其独特的优点,如简单的制备方法、优良的化学及热稳定性、良好的生物兼容性和无毒性等,受到越来越多的关注。石墨相氮化碳及其复合材料目前已被广泛应用于电催化、光催化、生物成像等领域。由于具有大的比表面积,同时又是富电子的疏水材料,石墨相氮化碳相关材料被认为是一种理想的样品前处理吸附剂。该文探讨了近年来石墨相氮化碳及其复合材料作为固相萃取、分散固相萃取、磁性固相萃取、固相微萃取吸附剂在样品前处理中的应用,并对未来的发展趋势和应用前景进行了展望,以期为相关领域的研究提供帮助。 相似文献
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Three-phase separation for Triton X-114 or Triton X-100 solutions with addition of hydrophobically modified hydroxyethyl cellulose was investigated experimentally. When the surfactant concentration was high enough, the solution slightly above the cloud point could separate into three macroscopic phases: a cloudy phase in between a clear phase and a bluish, translucent phase. The rate of phase separation was very low with the formation of the clear and cloudy phases followed by the emergence of the bluish phase. The volume fraction of the cloudy phase increases linearly with the global polymer concentration, whereas the volume fraction of the bluish phase increases linearly with the global surfactant concentration. Composition analyses found that most of the polymer stayed in the cloudy phase, as opposed to most of the surfactant in the bluish phase. The interesting phase behavior can be explained by an initial associative phase separation followed by a segregative phase separation in the cloudy phase. 相似文献
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This paper discusses the behaviour of angiotensin 1 and neurotensin together with their metabolites in a three-phase liquid phase microextraction under acidic conditions. Variations in donor phase, organic phase, and acceptor phase are studied with extraction recovery as response variable. It is proved that for all peptides the transport across the organic phase is mediated by heptane-1-sulphonic acid. n-Octanol gave overall best results as organic phase. A donor phase volume of 1.0 mL was chosen as a compromise between optimal recovery and robustness of the LPME device. The optimal pH of the donor phase (using acceptor phase of pH 2) was found to be different for the peptides, which opens opportunities for selective sample preparation. Decreasing the acceptor phase pH to 1.0 resulted in increased extraction recoveries. On using 1.0 mL of donor phase containing 50 mM heptane-1-sulphonic acid pH 3, n-octanol as organic phase immobilized in the pores of the fibre, and 20 microL of acceptor phase containing 0.1 mol/L HCl, extraction recoveries up to 82% (enrichment factor = 41) were achieved. To our knowledge this is the first report on liquid phase microextraction of angiotensins and neurotensins. 相似文献
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在基于相位分析的三维测量系统中,为了准确地得到物体的高度,相位展开扮演着很重要的角色。传统的相位展开方法常常需要额外的投影图,而傅里叶变换轮廓术只需要采集一幅或两幅变形条纹图就可以实现对物体轮廓的测量,其方法速度快,易于实现。针对傅里叶变换轮廓术方法计算得到的截断相位分布,本文提出了一种利用截断相位与参考平面相位差值2π的整数倍数获得截断相位的正确级次,辅助相位展开的方法。当被测物体较复杂,或者相位截断次数较多时,该方法在已有参考平面相位的基础上虚拟新的相位平面,依次比较截断相位和虚拟相位,进行多次分级相位展开,结合多个展开相位结果,最终得到正确的展开相位。该方法展开速度快,展开错误不会蔓延传递。仿真和实物实验结果证明了该方法的可行性,说明该方法可用于傅里叶变换轮廓术中进行截断相位的快速展开。 相似文献
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P. L. Zhu 《Chromatographia》1986,21(4):229-233
Summary An equation is derived which can describe how the retention of solutes is influenced by the composition of the mobile phase
in reversed-phase liquid chromatography, the retention of solutes in alkyl bonded stationary phase regarded as the complexation
between solute molecule and the active sites on the surface of the stationary phase. When the stationary phase is not fully
saturated by the organic modifier, the activity of the active sites, the activity coefficient of the adsorbed solute as well
as the activity coefficient of the solute in the mobile phase depend on the composition of the mobile phase. However, when
the stationary phase is fully saturated, the composition of the mobile phase mainly influences the activity coefficient of
the solute in the mobile phase. In addition, the selectivity of retention is discussed in terms of the derived equation. 相似文献
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The formation of lyotropic mesophases (liquid crystals) in four binary systems n-alkyl glycosides/water was examined in dependence on surfactant concentration, temperature and the chain lengths (alkyl = heptyl, octyl, nonyl, decyl). The binary phase diagrams were established and the enthalpies of phase transitions were measured. The following phase transitions were detected by texture observation and calorimetry: hexagonal phase H, lamellar phase L, cubic phase Q, gel phase G and crystalline phase C. The positions of the corresponding regions of these phases in the phase diagram were determined. Sequence of phases and the localization of the phase regions were depended on the chain length of the alkyl group. So in the binary system n-decyl-β-D-glucoside/water the H-phase was not observed. 相似文献
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The polymerisation of styrene in lyotropic liquid-crystalline (LC) phases of dioctadecyldimethylammonium bromide (DODAB)
in water is explored. Amphiphile concentrations between 20 and 50 wt % are employed. The study is set out as a model study
for polymerisation reactions in nonstabilised, nonfunctional bilayer systems. X-ray characterisation was used to assess the
phase behaviour of the lyotropic mesophases before, during and after polymerisation. The DODAB/water system forms the lamellar
phase within the concentration range considered. Addition of styrene to the lamellar phase of DODAB at an equimolar ratio
induces a phase shift to a bicontinuous cubic phase at elevated temperatures near the phase-transition temperature. Upon polymerisation
within this cubic phase, the phase structure is maintained if the system is kept at constant temperature; however, if the
polymer/amphiphile phase is cooled, the lamellar phase, being typical of the DODAB/water system, is restored. It is concluded
that, as a result of phase separation between the polymer and the amphiphile phase, the polymerisation in lyotropic LC phases
does not provide a stable copy of the templating amphiphile phase. This is in analogy to the observations for polymerisations
in other lyotropic phases.
Received: 16 March 2000 Accepted: 1 July 2000 相似文献
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An emulsification liquid phase microextraction followed by on-line phase separation coupled to high performance liquid chromatography (HPLC) is introduced based on a novel idea for the separation of dispersed organic phase from aqueous phase. In this method, the dispersed organic extraction phase was filtered using an in-line filter and it was separated from the water sample. The new approach is simple and, in addition to improving some limitations of the conventional emulsification liquid phase microextraction, eliminates the need for centrifugation in the phase separation step. 相似文献
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S. Goto 《Catalysis Surveys from Asia》2004,8(4):241-247
Phase transfer catalysis, a technique to bring the reactants in two immiscible phases together by adding a phase transfer agent, has been employed in the production of fine chemicals and pharmaceuticals in the last few decades. The third liquid phase (catalytic phase) may be formed when phase transfer catalysts (PTC), cannot be dissolved in either organic or aqueous phase. The third phase catalytic systems have the following three advantages, that is, (1) high activity (2) repeated use and (3) separation between the organic phase and the aqueous phase. It is expected that simple new processes can be constructed by applying these three advantages. 相似文献