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目前教科书上普遍认为乙腈与水在任何条件都是互溶的。通过引导学生在开放环境下进行批判性学习,发现乙腈在水中的溶解性受到实验条件的影响。加入足量的无机盐或有机盐、加入足量的单糖或二糖、加入足量的疏水溶剂、放置于-20℃环境中等,均能引起乙腈-水混合溶液体系的相分离。相分离后的上相为富乙腈相,下相为贫乙腈相。人们已将这些相分离过程发展成为4种乙腈基萃取方法:乙腈盐析萃取法、乙腈糖析萃取法、乙腈低温萃取法和溶剂诱导相变萃取法。这些知识拓展了师生对于乙腈性质“新”的理解,激励了学生批判性学习的勇气。 相似文献
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多功能柱净化-高效液相色谱法同时检测小麦中雪腐镰刀菌烯醇和脱氧雪腐镰刀菌烯醇 总被引:1,自引:0,他引:1
建立了小麦中雪腐镰刀菌烯醇(NIV)和脱氧雪腐镰刀菌烯醇(DON)的高效液相色谱同时检测方法。样品采用乙腈-水(体积比85:15)混合溶剂进行提取.通过多功能净化柱(MFC)进行一次性净化,以C18柱为分离柱,水-乙腈-甲醇(体积比90:5:5)混合溶剂为流动相进行高效液相色谱分离和检测。在小麦样品中,本方法在0.2~5μg/g添加范围内的凹收率为87%~99%;相对标准偏差为1.5%~8.3%;DON和NIV的检出限分别为0.12和0、16μg/g(5/N=3)。 相似文献
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通过光化学方法取代传统的金属催化等法合成重要的药物中间体唑烷酮,反应条件温和、操作简便、产率较高且污染少.同时研究了丙酮、甲醇、乙腈3种溶剂与水的不同配比对反应产物的影响.随着溶剂极性增加,立体选择性有一定提高. 相似文献
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混合溶剂水含量强烈影响芘从H2O/DMF混合溶剂向聚苯乙烯/聚丙烯酸二嵌段共聚物平头胶团的增溶,随着水含量增加而明显增大了芘和胶团内核PS间的结合力,促进了芘的增溶。实验结果表明,增加混合溶剂极性组分是实现有效增溶的一种简便方法。 相似文献
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混合溶剂水含量强烈影响芘从H2O/DMF混合溶剂向聚苯乙烯/ 聚丙烯酸二嵌段共聚物平头胶团的增溶,随着水含量增加而明显增大了芘和胶团内核PS间的结合力,促进了芘的增溶。实验结果表明,增加混合溶剂极性组分是实现有效增溶的一种简便方法。 相似文献
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多功能柱净化-高效液相色谱法检测谷物中的玉米赤霉烯酮 总被引:7,自引:0,他引:7
建立了玉米和小麦中玉米赤霉烯酮(ZEN)的多功能柱净化-高效液相色谱检测方法。样品经乙腈-水混合溶剂(V(乙腈):V(水)=84:16)提取,通过多功能净化柱(MFC)进行一次性净化,以Symmetry^R C18柱为分离柱,甲醇-水(V(甲醇):V(水)=68:32)为流动相进行高效液相色谱分离和检测。玉米赤霉烯酮的质量浓度在0.01~4.0μg/mL范围内呈良好线性,相关系数为0.9996。检出限为0.04μg/g,在0、04—5.0mg/kg添加范围内的回收率为87.5%~98.6%,相对标准偏差为1.5%~8.3%。 相似文献
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The retention of aromatic hydrocarbons with polar groups has been correlated as log k1 versus log k2 for reversed-phase high-performance liquid chromatography systems with different binary aqueous mobile phases containing methanol, acetonitrile or tetrahydrofuran as modifiers. Distinct changes in separation selectivity have been observed between tetrahydrofuran and acetonitrile or methanol systems. Methanol and acetonitrile systems show lower diversity of separation selectivity. The changes in retention and selectivity of aromatic hydrocarbons with various polar groups between any two chromatographic systems with binary aqueous eluents (tetrahydrofuran vs. acetonitrile, tetrahydrofuran vs. methanol and methanol vs. acetonitrile) have been interpreted in terms of molecular interactions of the solute with especially one component of the stationary phase region, i.e. extracted modifier, and stationary phase ordering. The ordering of the stationary phase region caused by modifier type influences the chromatographic selectivity of solutes with different molecular shape. 相似文献
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Summary The solvation parameter model is used to characterize the retention properties of a cyanopropylsiloxanebonded, silica-based
sorbent with methanol, acetonitrile, tetrahydrofuran, and isopropanol in water as mobile phases. The system constants over
the composition range 1 to 50 % (v/v) organic solvent indicate that retention occurs because of the relative ease of cavity
formation in the solvated stationary phase compared to the same process in the predominantly aqueous mobile phase as well
as from more favorable stationary phase interactions with solutes containing π- and n-electrons. The capacity of the solute
for dipole-type interactions is not important whereas all hydrogen-bond-type interactions result in reduced retention. Graphing
the system constants as a function of mobile phase composition provides a simple mechanism for interpreting the change in
capacity of the chromatographic system for retention in terms of changes in the relative weighting of fundamental intermolecular
interactions. A comparison is also made with the retention properties of an octadecylsiloxane-bonded, silica-based sorbent
with 30 % (v/v) methanol in water as the mobile phase and the extraction characteristics of a porous polymer sorbent with
1 % (v/v) methanol, acetonitrile, tetrahydrofuran, and isopropanol in water as the sample processing solvent. Changes in sorbent
selectivity due to selective uptake of the processing solvent are much smaller for the cyanopropylsiloxane-bonded sorbent
than the results found for a porous polymer sorbent. 相似文献
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Summary The solvation parameter model is used to characterize the retention properties of a cyanopropylsiloxane-bonded, silica-based sorbent with methanol, acetonitrile, tetrahydrofuran, and isopropanol in water as mobile phases. The system constants over the composition range 1 to 50% (v/v) organic solvent indicate that retention occurs because of the relative ease of cavity formation in the solvated stationary phase compared to the same process in the predominantly aqueous mobile phase as well as from more favorable stationary phase interactions with solutes containing - and n-electrons. The capacity of the solute for dipole-type interactions is not important whereas all hydrogen-bond-type interactions result in reduced retention. Graphing the system constants as a function of mobile phase composition provides a simple mechanism for interpreting the change in capacity of the chromatographic system for retention in terms of changes in the relative weighting of fundamental intermolecular interactions. A comparison is also made with the retention properties of an octadecylsiloxane-bonded, silica-based sorbent with 30% (v/v) methanol in water as the mobile phase and the extraction characteristics of a porous polymer sorbent with 1% (v/v) methanol, acetonitrile, tetrahydrofuran, and isopropanol in water as the sample processing solvent. Changes in sorbent selectivity due to selective uptake of the processing solvent are much smaller for the cyanopropylsiloxane-bonded sorbent than the results found for a porous polymer sorbent. 相似文献
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Summary Capacity factor (k′) values of aromatic hydrocarbons with mono-substituted polar-groups are correlated for reversed-phase
systems involving stationary phases with C18 or C4 ligands chemically bonded to silica and a binary aqueous eluent containing modifiers: methanol, acetonitrile, tetrahydrofuran,
isopropanol, dioxane or dimethoxyethane. The relative retention variations of the solutes are interpreted with special consideration
of their interactions with non-polar stationary phases and the molecular structure of the modifiers and solutes. Rules for
retention and selectivity optimisation in RP-HPLC systems are given. 相似文献
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反相离子对色谱中有机溶剂浓度和离子对试剂浓度对保留值的影响 总被引:2,自引:0,他引:2
我们测定了氨基苯磺酸和氨基萘磺酸在反相离子对色谱中不同乙腈/水, 甲醇/水配比和离子对试剂浓度下的保留值,并把两种冲洗剂下的保留值和关系式lnk'=a+C~c~b中的参数a,C作线性关联,得到很好的相关性,这表明有机溶剂乙腈和甲醇对选择性并无显著的影响,但乙腈有更大的冲洗强度.证明关系式lnk'=A+Blnc~p+C~c~ b能较好地描述有机溶剂和离子对试剂浓度对保留值的影响, 但当离子对试剂浓度较高时该关系式不成立.同时提出了有机溶剂浓度和离子对试剂浓度"等同效应" 的概念 相似文献
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Summary Variations in retention and selectivity have been studied in cyano, phenyl and octyl reversed bonded phase HPLC columns. The retention of toluene, phenol, aniline and nitrobenzene in these columns has been measured using binary mixtures of water and methanol, acetonitrile or tetrahydrofuran mobile phases in order to determine the relative contributions of proton donor-proton acceptor and dipole-dipole interactions in the retention process. Retention and selectivity in these columns was correlated with polar group selectivities of mobile phase organic modifiers and the polarity of the bonded stationary phases. In spite of the prominent role of bonded phase volume and residual silanols in the retention process, each column exhibited some unique selectivities when used with different organic modifiers. 相似文献
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Sanka N. Atapattu 《Journal of separation science》2022,45(9):1487-1492
The solvation parameter model system constants and retention factors were used to interpret retention properties of 39 calibration compounds on a biphenylsiloxane-bonded stationary phase (Kinetex biphenyl) for acetone-water binary mobile phase systems containing 30–70% v/v. Variation in system constants, phase ratios, and retention factors of acetone-water binary mobile phases systems were compared with more commonly used acetonitrile and methanol mobile phase systems. Retention properties of acetone mobile phases on a Kinetex biphenyl column were more similar to that of acetonitrile than methanol mobile phases except with respect to selectivity equivalency. Importantly, selectivity differences arising between acetone and acetonitrile systems (the lower hydrogen-bond basicity of acetone-water mobile phases and differences in hydrogen-bond acidity, cavity formation and dispersion interactions) could be exploited in reversed-phase liquid chromatography method development on a Kinetex biphenyl stationary phase. 相似文献
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In this study, a series of polycyclic aromatic hydrocarbons (PAHs) and nitrogen-containing polycyclic aromatic hydrocarbons (NPAHs) is separated on a hybrid stationary phase using methanol and acetonitrile mobile phases. Temperature is varied from 283 to 313 K in order to determine thermodynamic and kinetic parameters of the separation. Thermodynamic behavior is characterized by the retention factor and associated changes in molar enthalpy, whereas kinetic behavior is characterized by the rate constants and associated activation energies. In this study, the retention factors for the NPAHs are smaller than those for the parent PAHs in methanol, while they are more similar to the parent PAHs in acetonitrile. The changes in molar enthalpy are very similar for all solutes, yet are more negative in acetonitrile than in methanol. The rate constants for the NPAHs are smaller than those for their parent PAHs in both mobile phases. Moreover, the rate constants in acetonitrile are one to four orders of magnitude smaller than those in methanol. Based on these thermodynamic and kinetic results, the hybrid stationary phase is compared to traditional silica stationary phases. In addition, the relative contributions from the partition and adsorption mechanisms are discussed. 相似文献
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The system constants of the solvation parameter model are used to prepare system maps for the retention of small neutral compounds on an ethyl-bridged, ocatadecylsiloxane-bonded superficially porous silica stationary phase (Kinetex EVO C18) for aqueous mobile phases containing 10–70% (v/v) methanol or acetonitrile. Electrostatic interactions (cation-exchange) are important for the retention of weak bases with acetonitrile–water but not methanol–water mobile phase compositions. Compared with a superficially porous octadecylsiloxane-bonded silica stationary phase (Kinetex C18) with a similar morphology but different topology statistically significant differences in selectivity at the 95% confidence level are observed for neutral compounds that vary by size and hydrogen-bond basicity with other intermolecular interactions roughly similar. These selectivity differences are dampened with acetonitrile–water mobile phases, but are significant for methanol–water mobile phase compositions containing <30% (v/v) methanol. A comparison of a totally porous ethyl-bridged, octadecylsiloxane-bonded silica stationary phase (XBridge C18) with Kinetex EVO C18 indicated that they are effectively selectivity equivalent. 相似文献
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The retention of aliphatic hydrocarbons with polar groups has been compared in respect to the separation selectivity changes in reversed-phase high-performance liquid chromatography with C18 stationary phase type and binary water eluent composed of methanol, acetonitrile, or tetrahydrofuran as modifiers. The changes in separation selectivity when one modifier is replaced by another in the eluent is explained, taking into consideration molecular interactions of the solutes with components of the stationary phase region, i.e., extracted modifier, and ordering of the stationary phase by the modifier. 相似文献