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介绍了毛细管电色谱中流动相的选择以及缓冲液的不同离子强度对ODS柱分离行为的影响。 相似文献
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低压离子色谱理论探讨 总被引:5,自引:0,他引:5
本文提出了低压离子色谱的设计思想,讨论了离子色谱分离柱的交换容量与分离检测之间的关系。同时对低压离子色谱的可行性进行了探讨,认为由于离子色谱柱填料的特殊性,低压在离子色谱这一领域是可行的。 相似文献
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在不同键合程度的ODS柱和硅胶柱上,以甲醇和磷酸盐缓冲液为移动相,研究了色谱分离吲哚生物碱的特性。具体考察了pH对容量因子,甲醇比例和离子强度对保留时间的影响。实验测得吲哚生物碱在三种选定的硅胶和ODS柱上有相似的保留行为,其容量因子都随pH的升高而增加,随甲醇比例和离子强度的增加而下降。在ODS柱上难以分离的一些生物碱在硅胶柱上用含磷酸缓冲液的甲醇为移动相时能得到满意的分离。 相似文献
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离子液体中卤素离子杂质的离子色谱-直接电导检测法分析 总被引:4,自引:4,他引:0
研究了离子色谱-直接电导检测法分离测定离子液体中的卤素离子(F~-、Cl~-、Br~-)杂质.采用Shim-pack IC-A3阴离子交换色谱柱,考察了淋洗液种类及浓度、流速和色谱柱温度对分离测定的影响.最佳色谱条件为:以1.25 mmol/L邻苯二甲酸氢钾为淋洗液,流速1.5 mL/min,色谱柱温45 ℃.在此条件下可以基线分离卤素离子,且NO~-_3、BF~-_4、SO~(2-)_4不干扰测定.该法测定卤素离子的检出限(S/N=3)为0.02 ~0.11 mg/L,峰面积的相对标准偏差(n=5)不大于0.7%,F~-、Cl~- 和Br~- 的标准曲线的线性范围分别为0.1 ~50、0.1 ~50、0.5 ~100 mg/L.将方法用于烷基咪唑四氟硼酸盐离子液体中卤素离子杂质的测定,加标回收率为98% ~102%. 相似文献
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A. Gurkaynak F. Tubert J. Yang J. Matyas J. L. Spencer Carl C. Gryte 《Journal of polymer science. Part A, Polymer chemistry》1996,34(3):349-355
Poly(acrylic acid) (PAA) was decarboxylated in aqueous solution as a function of pH and ionic strength in the temperature range 100–350°C. Degradation kinetics were first order with respect to acid functionality. The rate of decarboxylation at high pH (Eα = 51.1 kcal/mol) was much slower than that at low pH (Eα = 20.3 kcal/mol). At intermediate pH, the reactivity was found to depend on the degree of dissociation of PAA as a functions of ionic strength, pH, and temperature. No monomer was observed in the reaction product. © 1996 John Wiley & Sons, Inc. 相似文献
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The adsorption of two different proteins at a planar poly(acrylic acid) (PAA) brush was studied as a function of the ionic strength of the protein solutions applying total internal reflection fluorescence (TIRF) spectroscopy. Planar PAA brushes were prepared with a grafting density of 0.11 nm(-2) and were characterized using X-ray reflectometry. Hen egg-white lysozyme and bovine serum albumin (BSA) were used as model proteins, which have a net positive and negative charge at neutral pH-values, respectively. It has been found that both proteins adsorb strongly at a planar PAA brush at low ionic strength. Whereas lysozyme interacts with a PAA brush under electrostatic attraction at neutral pH-values, BSA binds under electrostatic repulsion at pH > 5. Even at pH = 8, significant amounts of BSA are adsorbed to a planar PAA brush. In addition, the reversibility of BSA adsorption has been characterized. Dilution of a BSA solution leads to an almost complete desorption of BSA from a PAA brush at short contact times. When the ionic strength of the protein solutions is increased to about 100-200 mM, a planar PAA brush appears largely protein-resistant, regardless of the protein net charge. The results of this study indicate that the salt-dependent protein affinity of a PAA brush represents a unique effect that must be explained by a novel protein-binding mechanism. On the basis of a recent model, it is suggested that a release of counterions is the most probable driving force for protein adsorption at a PAA brush. In a general view, this study characterizes a planar PAA brush as a new materials coating for the controlled immobilization of proteins whose use in biotechnological applications appears to be rewarding. 相似文献
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Vitaliy V. Khutoryanskiy Zauresh S. Nurkeeva Aibek D. Sergaziyev Janusz M. Rosiak 《European Polymer Journal》2003,39(4):761-766
The complex formation of poly-2-[(methacryloyloxy)-ethyl]trimethylammonium chloride (PMADQUAT) with poly(acrylic acid) (PAA) of different molecular weights has been studied in aqueous solutions by potentiometric, viscometric, turbidimetric and FTIR spectroscopic methods. The formation of insoluble non-stoichiometric polyelectrolyte complexes has been shown. The stability of polyelectrolyte complexes in solutions of different pH and ionic strength has been evaluated. The formation of polyelectrolyte complexes between hydrogels of PMADQUAT and linear PAA of different molecular weights has been studied. It was shown that the molecular weight of PAA considerably affects the kinetics of interaction as well as the final state of gel-polymer complex. 相似文献
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Abohachem Laguecir Serge Ulrich Jérôme Labille Nicolas Fatin-Rouge Serge Stoll Jacques Buffle 《European Polymer Journal》2006,42(5):1135-1144
Monte Carlo simulations, experimental titrations and fluorescence correlation spectroscopy experiments were used to investigate the conformational and electrical properties of polyacrylic acids (PAA). On the one hand, titration curves were calculated to get an insight into the role of pH on the degree of ionization and conformation of PAA chains. On the other hand, experimental potentiometric titrations of PAA were also achieved for different PAA molecular weights and compared to the calculated titration curves obtained by Monte Carlo coarse grained simulations. It was found that for a large range at intermediate PAA ionizations, a good correlation is obtained between experimental and simulations data thanks to the prominence of electrostatic interactions in this domain. The effect of ionic concentration and PAA molecular weight on the titration curves was also investigated. In order to get a better understanding of PAA conformational behavior, we also investigated PAA diffusion properties in aqueous solutions as a function of pH and ionic strength by fluorescence correlation spectroscopy (FCS), thanks to its high sensitivity to measure diffusion coefficients of tracer solutes. Good qualitative agreements were observed between experimental diffusivities and polymer properties calculated from MC simulations. It was shown that the high molecular weight PAA chains display more significant changes in diffusivity in agreement with the ionization degrees and conformational changes observed in the simulations. 相似文献
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DeLongchamp DM Hammond PT 《Langmuir : the ACS journal of surfaces and colloids》2004,20(13):5403-5411
We report the development of a solid polymer electrolyte film from hydrogen bonding layer-by-layer (LBL) assembly that outperforms previously reported LBL assembled films and approaches battery integration capability. Films were fabricated by alternating deposition of poly(ethylene oxide) (PEO) and poly(acrylic acid) (PAA) layers from aqueous solutions. Film quality benefits from increasing PEO molecular weight even into the 10(6) range due to the intrinsically low PEO/PAA cross-link density. Assembly is disrupted at pH near the PAA ionization onset, and a potential mechanism for modulating PEO:PAA ratio within assembled films by manipulating pH is discussed. Ionic conductivity of 5 x 10(-5) S/cm is achievable after short exposure to 100% relative humidity (RH) for plasticization. Adding free ions by exposing PEO/ PAA films to lithium salt solutions enhanced conductivity to greater than 10(-5) S/cm at only 52% RH and tentatively greater than 10(-4) S/cm at 100% RH. The excellent stability of PEO/PAA films even when exposed to 1.0 M salt solutions led to an exploration of LBL assembly with added electrolyte present in the adsorption step. Fortuitously, the modulation of PEO/PAA assembly by ionic strength is analogous to that of electrostatic LBL assembly and can be attributed to electrolyte interactions with PEO and PAA. Dry ionic conductivity was enhanced in films assembled in the presence of salt as compared to films that were merely exposed to salt after assembly, implying different morphologies. These results reveal clear directions for the evolution of these promising solid polymer electrolytes into elements appropriate for electrochemical power storage and generation applications. 相似文献
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Cleary J Bromberg L Magner E 《Langmuir : the ACS journal of surfaces and colloids》2004,20(22):9755-9762
Pluronic-PAA, a thermogelling copolymer composed of side chains of poly(acrylic acid) (PAA) grafted onto a backbone of Pluronic copolymer, is of interest as a vehicle for the controlled release of compounds. An important feature of such a vehicle is its bioadhesive/mucoadhesive properties, which in the case of Pluronic-PAA are significant due to the presence of the PAA side chains. An atomic force microscopy (AFM) method has been developed and utilized to investigate the interactions between a Pluronic-PAA-modified microsphere and mucous substrates. The bioadhesive force was successfully measured, and trends were observed under conditions of varying pH and ionic strength. Pluronic-PAA exhibits significant mucoadhesion over a range of pH values, with mucoadhesion being optimal at pH 4-5 (adhesive force approximately 80 mN/cm(2)) and dropping sharply at higher pH, to a value of approximately 20 mN/cm(2) at pH 8. The mucoadhesive force decreased with increasing ionic strength, from a value of approximately 80 mN/cm(2) in 0.025 M NaCl to approximately 25 mN/cm(2) in 1.0 M NaCl. These results have been interpreted in terms of the effect of changing pH and ionic strength on electrostatic interactions and swelling of the polymer and mucin layers. Tensiometric force measurements indicated that hydrophobic interactions, as well as hydrogen bonding and electrostatic interactions, were significant in the mucoadhesion of Pluronic-PAA copolymers. Experiments with a range of Pluronic-PAA copolymers with varying PPO contents in the Pluronic segments showed that increasing the overall PPO content increased the hydrophobicity of the polymer solutions. This was reflected in the increases in the advancing contact angles with the mucin layer, indicating that hydrophobic interactions play a role in the adhesion of Pluronic-PAA to mucin. 相似文献
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The retention behaviour of a set of sixteen more or less drugs on a CN column with methanol-phosphate buffer as eluent was studied. The influence of the volume percentage of methanol, pH and the ionic strength on the capacity factors (k') of the drugs was determined using an experimental design consisting of three pH values (3, 5 and 7), four ionic strengths (0.025, 0.05, 0.075 and 0.1) and three volume percentages of methanol (10, 30 and 50%). The selected drugs were basic, acidic and neutral compounds with different polarity properties. The number of carbon atoms, considered here as reflecting the hydrophobic characteristics of the solutes, varied from 7 to 25. The influence on the retention of drugs on a CN column of the different parameters studied was evaluated. The volume percentage of organic modifier and the pH are the most important factors. A change in ionic strength is important only when large molecules are chromatographed. As the interaction between pH, ionic strength and volume percentage of methanol is small, optimization of the three parameters separately is possible. 相似文献