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31.
Summary Plots of capacity factor and retention time vs. elution solvent composition were proved to be useful to interpret the retention
behavior of Kepone and its metabolites in a reversed-phase solid-phase extraction and to optimize the elution solvent. The
percent recovery of Kepone was largely improved when the solvent was optimized. The standard deviations of the results of
extractions were also improved upon the optimization of the solvent. 相似文献
32.
A novel zirconia-based hybrid organic-inorganic sol-gel coating was developed for capillary microextraction (CME) (in-tube SPME). High degree of chemical inertness inherent in zirconia makes it very difficult to covalently bind a suitable organic ligand to its surface. In the present work, this problem was addressed from a sol-gel chemistry point of view. Principles of sol-gel chemistry were employed to chemically bind a hydroxy-terminated silicone polymer (polydimethyldiphenylsiloxane, PDMDPS) to a sol-gel zirconia network in the course of its evolution from a highly reactive alkoxide precursor undergoing controlled hydrolytic polycondensation reactions. A fused silica capillary was filled with a properly designed sol solution to allow for the sol-gel reactions to take place within the capillary for a predetermined period of time (typically 15-30 min). In the course of this process, a layer of the evolving hybrid organic-inorganic sol-gel polymer got chemically anchored to the silanol groups on the capillary inner walls via condensation reaction. At the end of this in-capillary residence time, the unbonded part of the sol solution was expelled from the capillary under helium pressure, leaving behind a chemically bonded sol-gel zirconia-PDMDPS coating on the inner walls. Polycyclic aromatic hydrocarbons, ketones, and aldehydes were efficiently extracted and preconcentrated from dilute aqueous samples using sol-gel zirconia-PDMDPS coated capillaries followed by thermal desorption and GC analysis of the extracted solutes. The newly developed sol-gel hybrid zirconia coatings demonstrated excellent pH stability, and retained the extraction characteristics intact even after continuous rinsing with a 0.1 M NaOH solution for 24 h. To our knowledge, this is the first report on the use of a sol-gel zirconia-based hybrid organic-inorganic coating as an extraction medium in solid phase microextraction (SPME). 相似文献
33.
《Journal of separation science》2003,26(17):1527-1532
In this paper, a setup called micro‐column solid phase extraction (MicroSPE) was developed to enhance the sensitivity of capillary electrophoresis. The setup consists of a manual pump, several insulin syringes, and a Teflon extraction cartridge. The cartridge was made of 2–4 mm irregular C18 solid phase materials in a Teflon tube (375 μm ID) with glass fiber frits. Two pieces of capillary tubing were connected to both the ends of the cartridge. Using sulindac‐spiked urine as the test sample, the extraction and analytical conditions were investigated in detail. When 1 μL 70/30 methanol/water was applied as the elution solvent, satisfactory results could be obtained. The internal standard method was used to quantitatively determine the compound in urine. The detection limit for sulindac was 2.9 ng/mL and the enrichment factor reaches more than 260. The result illustrates that the MicroSPE setup has a significant concentrating effect and is suitable for preconcentrating and cleaning‐up samples with complex matrices. 相似文献
34.
In this paper, we describe a new method of automated sample preparation for multiplexed biological analysis systems that use flow cytometry fluorescence detection. In this approach, color-encoded microspheres derivatized to capture particular biomolecules are temporarily trapped in a renewable surface separation column to enable perfusion with sample and reagents prior to delivery to the detector. This method provides for separation of the biomolecules of interest from other sample matrix components as well as from labeling solutions. After sample preparation, the beads can be released from the renewable surface column and delivered to a flow cytometer for direct on-bead analysis one bead at a time. Using mixtures of color-encoded beads derivatized for various analytes yields suspension arrays for multiplexed analysis. Development of this approach required a new technique for automated capture and release of the color-encoded microspheres within a fluidic system. We developed a method for forming a renewable filter and demonstrate its use for capturing microspheres that are too small to be easily captured in previous flow cells for renewable separation columns. The renewable filter is created by first trapping larger beads in the flow cell, and then smaller beads are captured either within or on top of the bed of larger beads. Both the selective microspheres and filter bed are automatically emplaced and discarded for each sample. A renewable filter created with 19.9 μm beads was used to trap 5.6 μm optically encoded beads with trapping efficiencies of 99%. The larger beads forming the renewable filter did not interfere with the detection of color-encoded 5.6 μm beads by the flow cytometer fluorescence detector. The use of this method was demonstrated with model reactions for a variety of bioanalytical assay types including a one-step capture of a biotinylated label on Lumavidin beads, a two-step sandwich immunoassay, and a one-step DNA binding assay. A preliminary demonstration of multiplexed detection of two analytes using color-encoded beads was also demonstrated. The renewable filter for creating separation columns containing optically encoded beads provides a general platform for coupling renewable surface methods for sample preparation and analyte labeling with flow cytometry detectors for suspension array multiplexed analyses. 相似文献
35.
Felicia Dragan I. Bratu Gh. Borodi Mihaela Toma A. Hernanz S. Simon Gh. Cristea R. Peschar 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(1-2):125-130
Aqueous-solution complexes of β-cyclodextrin (β-CD) with metoprolol tartrate (MET) have been analysed with 1H NMR and UV–vis spectroscopy. With 1H NMR a [1:1] stoichiometry could be established for the β-CD-MET complex while its stability constant was determined with
UV–vis spectroscopy. Powder diffraction data of a polycrystalline sample of the β-CD-MET complex show that a novel product
has been formed, likely to be a β-CD-MET [1:1] inclusion complex. Also Hyperchem MM+ molecular-dynamics results suggest an
inclusion complex and from 1H NMR data it is inferred that probably the MET is docked in the CD with the formers methoxyethyl-benzene moiety in front.
Mihaela Toma is Socrates/Erasmus student at UNED Madrid 相似文献
36.
The response of a single TE102 and double TE104 rectangular cavity to the insertion of samples contained in tubes with variable wall thickness and a quartz Dewar into the cavity has been analyzed. A direct, indirect, and concurrent (positive or negative) “lens effect” inside the double TE104 rectangular cavity is discussed. The experimental dependence of the EPR signal intensity on the wall thickness of the sample tube, δ, for the line-like samples with identical length of the sample material column, L=30 mm, recorded in the microwave cavity showed a directly proportional increase of the relative “lens effect” with the increase of the wall thickness of the tube in the interval, δ∈<0.1 mm, >0.5 mm. The insertion of the variable-temperature double-wall quartz Dewar (home-built, resonant frequency shift, ca. −300 MHz) into the single TE102 rectangular cavity showed the same relative “lens effect”, with ca. 1.5-time increase of the EPR signal intensity, for a point-like sample and the line-like samples with material columns of diameter of 1 and 1.3 mm, and wall thickness of the sample tubes, δ∈<0.1 mm, >0.5 mm. The increased effect of the Dewar arises because the active volume of the quartz Dewar tube walls is always much more larger than the active volume of the sample tube wall. In the case of the double TE104 rectangular cavity, the insertion of the quartz Dewar: (i) into the same cavity, in which the sample is present, caused a direct “lens effect”, with ca. 1.8-fold increase of the EPR signal intensity; however, (ii) into the complementary cavity, in which the sample is absent, caused an indirect “lens effect”, with ca. 0.6-fold decrease of the EPR signal intensity. With the Dewar and sample in one cavity and a large empty sample tube in the complementary cavity, a concurrent (positive or negative) “lens effect” can be observed. Thus, the possible increase/decrease of the EPR signal intensity depends on the volume ratio of the quartz Dewar tube walls and large sample tube wall inserted into the double TE104 rectangular cavity. Each of the above phenomena may be a significant source error in quantitative EPR spectrometry unless the samples to be compared in the quantitative EPR analysis are contained in sample tubes having the same wall thickness and each EPR spectra should be recorded inside an identical quartz Dewar. 相似文献
37.
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39.
食源性致病菌是引发和威胁公众健康的主要因素之一.由于食源性致病菌种类繁多,常规检测方法复杂耗时要求高,因此迫切需要一种更加快速精确的致病菌检测技术.在传统红外光谱检测致病菌的流程中,如经典的溴化钾压片法,除了压片本身的操作之外通常还需对样品进行冷冻干燥(约需2 d)等耗时前处理过程,因而不利于高通量快速检测.本研究利用... 相似文献
40.
《Physics letters. A》2020,384(20):126418
In this study, Cu-20wt.Sn alloy was produced by powder metallurgy (PM) method by using high purity element powders. The phases in the microstructure of the produced alloy were determined by XRD study. The phase transformation behaviour of the alloy was investigated by DSC and modelling method. Moreover, the Cu-20wt.Sn alloy system was modelled with molecular dynamics (MD) simulation based on modified Embedded Atom Method (MEAM). The radial distribution function (RDF) was calculated to determine the structural properties of system during the phase transformations. The experimental results showed that the transformation () → () occur at temperature above 500°C. The simulation results showed that the phase transformation occurs at 550°C temperature. Our simulation results are in reasonable agreement with the experimental data. 相似文献