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31.
《Electroanalysis》2006,18(2):115-120
Electrochemical method of detection of heparin polyion was developed based on voltammetry of heparin on a rotating glassy carbon (GC) electrode coated with a plasticized PVC membrane. The membrane was deposited on the GC disk by spin‐coating technique using a mixture of solutions of PVC in tetrahydrofuran, and 1,1′‐dimethylferrocene (DMFc) and hexadecyltrimethylammonium tetrakis(4‐chlorophenyl)borate (HTMATPBCl) in o‐nitrophenyl octyl ether. UV/vis reflection spectrometry was used to evaluate the membrane thickness, which exhibits a linear correlation with the membrane resistance measured by impedance spectroscopy. It is shown that this electrode can be used for amperometric or coulometric detection of heparin in aqueous samples of medically relevant concentrations (1–10 U mL?1), with a detection limit of 1.4 U mL?1. Evidence is provided indicating that the current determining step is the reversible adsorption of the ion‐pair of heparin polyion with HTMA+ cation at the membrane/aqueous electrolyte interface, which is driven by oxidation of DMFc at the GC/membrane interface. 相似文献
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电位法测定异价阳离子通过阳离子交换膜时的选择透过性 总被引:2,自引:0,他引:2
从理论上导出了不等价的两种阳离子在通过阳离子交换膜时的选择透过性与膜电位的关系,并用电位法对一些不等价阳离子组合在两种商品膜中的选择透过性进行了测定。本方法测定结果与电渗析实际分离效果相符。 相似文献
35.
氯磺化聚乙烯水解后是一种性能特异的离子交换膜。本文研究了低密度及高密度聚乙烯中空纤维氯磺化反应时间与交换容量之间的关系,并用红外光谱及广角X射线衍射法测定了氯磺化反应对聚乙烯晶体结构的影响。结果表明,氯磺化反应主要发生在聚乙烯的非晶区,最大交换容量及反应速度均与非晶区含量有关。反应对晶粒表面也有一定程度的侵蚀作用,随着交换容量的增加,结晶度下降,晶粒度减小。低密度及高密度聚乙烯的变化趋势相似,但前者比后者变化更显著。 相似文献
36.
Xiaoping Zhan 《European Polymer Journal》2007,43(4):1588-1594
Oral clonidine, used as an antihypertensive, can result in some side effects such as dry mouth, drowsiness, dizziness and sedation; thus, clonidine transdermal drug delivery (TDD) was considered. Use of the controlled release membrane was one of the methods in TDD systems to regulate the permeation properties. A new type of copolymer membrane that controlled clonidine linear release in TDD system was synthesized by UV radiation. This membrane consisted of three monomers: 2-hydroxy-3-phenoxypropylacrylate, 4-hydroxybutyl acrylate and diethyl maleate. The membrane had both fine permeation properties and perfect physical properties when three monomers were in the weight ratio of 4:4:2; this type of membrane was chosen as an optimized membrane. It was found that the membrane controlled clonidine zero-order release, the permeation rates decreased with the thicknesses of membranes increasing, and the permeation rates were linearly dependent on the square root of the concentration of clonidine. Furthermore, the optimized membranes were characterized by FTIR, DSC and SEM. 相似文献
37.
The preparation and potentiometric pH response properties of membranes formulated with various aminated-poly(vinyl chloride) (PVC-NH2) products are described. Products containing secondary and/or primary amino functional groups are obtained by modifying PVC with mono- and/or diamines, respectively. Blank membranes prepared with either type of aminated-polymer exhibit nearly Nernstian potentiometric pH responses over different pH ranges. In general, membranes based on diamino products exhibit pH response over a wider range (5–10.5) than membranes formulated with monoamino products (<8.0). These potentiometric results are used to estimate the basicity of the various primary and secondary amino sites in the membrane phases.Dedicated to Professer W. Simon on the occasion of his 60th birthday 相似文献
38.
Stoikov I. I. Gafiullina L. I. Ibragimova D. Sh. Antipin I. S. Konovalov A. I. 《Russian Chemical Bulletin》2004,53(6):1172-1180
New calix[4]arenes, di- and tetrasubstituted at the lower rim, with different functional groups were synthesized. They were studied as carriers of a series of dicarboxylic and -hydroxycarboxylic acids through a liquid impregnated membrane. The calix[4]arenes under study are capable of molecular recognition of oxalic acid in the series of structurally similar dicarboxylic and -hydroxycarboxylic acids. The regularities found make it possible to change purposefully the receptor ability of 1,3-disubstituted calix[4]arenes by variation of the nature of substituents. 相似文献
39.
In this study, porous glass fiber membranes were coated with monophenyl trimethoxysilane (MPh) and then sulphonated by chlorosulphonic acid to prepare the cation-exchange membranes with sulphonic acid groups. Different MPh-coating times were tested and the properties of the resulting membranes such as contact angle, FTIR spectrum, conductivity, and ion-exchange capacity were measured. It was found that the optimal MPh-coating time was 60 min and the related ion-exchange capacity was 49.5 μequiv./disc. The modified membrane under the optimal MPh-coating condition was adopted for lysozyme isolation. The results were compared with those for the commercial cation-exchange membrane with sulphonic acid groups (ICE 450 unsupported membrane). Although the prepared membrane exhibited less adsorption capacity than ICE 450 unsupported membrane in the batch lysozyme adsorption experiment, it showed lower non-specific binding ratio under higher salt concentration. In the flow process isolating lysozyme from hen egg albumen, the purification effectiveness obtained using the prepared cation-exchange membrane was superior to the ICE 450 unsupported membrane. 相似文献
40.
Poly(acrylonitrile-methylmethacrylate-sodium vinylsulfonate) membranes were subjected to seven different chemical modifications and the amount of the newly formed groups was measured for each membrane. Urease was then covalently immobilized onto the modified membranes and the amount of bound protein was determined. The kinetic parameters V(max) and K(m) of the immobilized urease were studied under static and dynamic conditions. Results showed that the rate of the enzyme reaction was higher for the membranes modified with NH(2)OH . H(2)SO(4), NH(2)NH(2) . H(2)SO(4), NaOH + EDA and NaOH + GA + EDA. It was confirmed that the reaction rate, measured under dynamic conditions, was higher than that one determined under static conditions. The influence of Cu(II) ions, as inhibitors, on the enzyme reaction kinetics (V(i) and K(i)) was also investigated. It turned out that the most sensitive membranes towards Cu(II) were those modified with NH(2)NH(2) . H(2)SO(4), NaOH + EDA and H(2)O(2). The results initiated further investigations on the influence of other heavy metal ions (Cd(II), Zn(II), Ni(II) and Pb(II)) over urease bound to a NH(2)OH . H(2)SO(4)-modified membrane. It was found that the inhibition effect of the heavy metal ions over immobilized urease decreases in the order: Cu(II) > Cd(II) > Zn(II) > Ni(II) > Pb(II). [Diagram: see text] 相似文献