Ion Chromatography of Inorganic Anions on Graphitic Carbon as the Stationary Phase

Inorganic anions could be separated on porous graphitic carbon stationary phases in ion chromatography. Ion exchange between eluent anions and sample anions on the stationary phase was confirmed by the retention behavior and the possibility of indirect photometric detection. The elution order of anions was different from that observed for commercially available anion exchangers. Chloride, nitrate, and sulfate contained in tap water could be determined in 7 min.     

Properties and Applications of Cryptand‐22 Surfactant for Ion Transport and Ion Extraction

A non‐ionic cryptand‐22 surfactant consisting of a macrocyclic cryptand‐22 polar head and a long paraffinic chain (C₁₀H₂₁‐Cryptand‐22) was synthesized and characterized. The critical micellar concentration (CMC) of the cryptand surfactant in ROH/H₂O mixed solvent was determined by the pyrene fluorescence probe method. In general, the cmc of the cryptand surfactant increased upon decreasing the polarity of the surfactant solution. The cryptand surfactant also can behave as a pseudo cationic surfactant by protonation of cryptand‐22 or complexation with metal ions. Effects of protonation and metal ions on the cmc of the cryptand surfactant were investigated. A preliminary application of the cryptand surfactant as an ion‐transport carrier for metal ions, e.g., Li⁺, Na⁺, K⁺ and Sr²⁺, through an organic liquid‐membrane was studied. The transport ability of the cryptand surfactant for these metal ions was in the order: K⁺ ≥ Na⁺ < Li⁺ < Sr²⁺. A comparison of the ion‐transport ability of the cryptand surfactant with other macrocyclic polyethers, e.g., dibenzo‐18‐crown‐6, 18‐crown‐6 and benzo‐15‐crown‐5, was studied and discussed. Among these macrocyclic polyethers, the cryptand surfactant was the best ion‐transport carrier for Na⁺, Li⁺ and Sr²⁺ ions. Furthermore, a foam extraction system using the cryptand surfactant to extract the cupric ion was also investigated.     

含磺酸,羧酸双功能基树脂对混合氨基酸的分离性能研究

对苯乙烯-丙烯腈-二乙烯基苯(S/AN/DVB)交联共聚机理研究曾发现,丙烯腈作为第三单体,可使DVB竞聚率比在S/DVB共聚体系中降低,相互分离显著,从而有利于合成性能较好的离子交换树脂;本文在此基础上,将S/AN/DVB共聚体中的氰基水解成羧基来合成含磺酸、羧酸双功能基树脂,解决了前人研究中仅有50％的氰基水解成羧基的问题,并首次将这种树脂应用于混合氨基酸的分离。     

Crystalline Degradation Products of Vancomycin as a New Chiral Stationary Phase for Liquid Chromatography

Two crystalline degradation products (CDP-1-M and CDP-1-m) are formed from vancomycin by hydrolytic loss of ammonia. The CDP are structurally similar to vancomycin, with two carboxyl groups, but are biologically inactive. In this work the CDP of vancomycin have been covalently linked to silica gel and their ability to resolve racemic mixtures, their stability, and their loading has been evaluated by HPLC. Elemental analysis and scanning electron microscopy were used to monitor the surface of this new stationary phase. Enantiomeric separation was achieved for some compounds that have not been previously been separated on other chiral stationary phases.     

锆胶基质阳离子色谱柱填料的制备

以10μm锆胶微球包覆聚苯乙烯制成强酸、弱酸型的阳离子色谱柱填料,具有良好的色谱性能。使用D ionex-120型双柱离子色谱仪,较好地分离碱金属、碱土金属离子及铵离子,比较了不同交换基团对溶质保留的影响。由于锆胶基质具有高的化学稳定性和机械强度,用作离子色谱柱填料有良好的应用前景。     

离子色谱整体固定相的最新进展

整体固定相是近年来新兴的一种多孔性固定相介质,它在离子态及极性化合物的分离中得到了越来越广泛的重视。本文就离子色谱领域整体固定相的发展以及最新的研究动向进行了综述,讨论了离子色谱整体固定相的优点、分类以及在分离分析离子态物质方面的应用等。     

Silica-Based Phenyl and Octyl Bifunctional Imidazolium as a New Mixed-Mode Stationary Phase for Reversed-Phase and Anion-Exchange Chromatography

In this study, octylbenzimidazolium-modified silica (BeImC8-Sil) was prepared by covalent attachment of 1-octylbenzimidazole to γ-chloropropyl silica. The synthesized materials were characterized by the elemental analysis, IR spectrum, and thermogravimetric analysis. Due to the introduction of phenyl and octyl groups on the quaternary imidazolium, the developed BeImC8-Sil column can function via both reversed-phase and anion-exchange retention mechanisms. The chromatographic properties of the synthesized material were investigated by the separations of polycyclic aromatic hydrocarbons, mono-substituted derivatives of benzene, anilines, and phenols, revealing the existence of multiple interactions, including hydrogen bonding, π–π stacking, electrostatic forces, and hydrophobic interactions in reversed-phase mode; inorganic and organic anions were also separated mainly through anion-exchange interaction. The proposed BeImC8-Sil is a promising mixed-mode stationary phase for the separation of complex samples in high-performance liquid chromatography.

     

Ethylammonium Acetate as a Mobile Phase Modifier for Reversed Phase Liquid Chromatography

We have synthesized the low melting hygroscopic ionic liquid ethylammonium acetate (EAA) and characterized a concentrated solution of EAA as a reversed phase mobile phase replacement for organic solvents like methanol. This solution of EAA acts like an organic solvent with a polarity parameter (P=6.0) similar to methanol (P=5.1) but less than water (P=10.2). A test mixture of salicylate, nitrofurantoin, and acetophenone was separated in this order on C1, C4, and C18 columns using an EAA modified aqueous mobile phase. On a C-18 column, the reduction in retention factor for acetophenone from about 20 to 2 as the % EAA is raised from 20–80% is similar to the same trend found using methanol. However, the retention order using methanol is first nitrofurantoin, then salicylate, and finally acetophenone. Log retention factor (k) versus the volume fraction of either EAA or methanol plots were linear indicating the solvent strength parameter for EAA was about 85% of that for methanol. Despite the relatively high viscosity of EAA, plate count values averaged only about 15% less for EAA as compared to methanol using the same mobile phase composition and could be raised by either working at a temperature above ambient or reducing the flow rate. EAA as a modifier allowed for faster separations of water-soluble vitamins on a reversed phase column designed for totally 100% aqueous mobile phases.Acknowledgements This work was supported by a grant from the Miami University Committee on Faculty Research. We thank ES Industries for the gift of the AquaSep column.     

Acetohydroxamate Resin as Column Packing for Ion Chromatography

A chelating resin with acetohydroxamate functional groups was synthesized and used as the stationary phase in ion chromatography for the determination of copper. As the reaction mechanism was mainly complexation, the coordination behavior of the synthesized resin toward Cu(II) was studied by means of EPR, IR and electronic spectrometry and potentiometry. The kinetic study shows that the resin is suitable for use in ion chromatography. We employed a resin column 250 mm long by 3 mm I.D. in conjunction with a mixture of hydrochloric acid and acetone as mobile phase for the determination of Cu(II). Detection of the chromatography system was carried out via post-column derivatisation of the column effluent with PAR at 520nm. The detection limit is 0.22ppm, and the relationship was linear in the range 0.25-1.20ppm. We investigated the effect of other metal ions, As(V), Cd(II), Cr(III), Hg(II), Ni(II), Pb(II) and Zn(II), or foreign ligands, EDTA, ascorbic acid, humic acid or sodium chloride on the determination of Cu(II) ion. A concentration column packed with acetohydroxamate resin combined with the above separation system was also used to determine of copper ion; the dynamic range is 2-15 ppb and the detection limit is 0.70ppb. The proposed system was applied to the analysis of Cu(II) in sea water.     

Application of Artificial Neural Network and Multiple Linear Regression Retention Models for Optimization of Separation in Ion Chromatography by Using Several Criteria Functions

This work focuses on problems regarding empirical retention modelling and optimization of separation in ion chromatography. Influences of eluent flow rate and concentration of eluent competing ion (OH^–) on separation of seven inorganic anions (fluoride, chloride, nitrite, sulphate, bromide, nitrate, and phosphate) were investigated. Artificial neural networks and multiple linear regression retention models in combination with several criteria functions were used and compared in global optimization process. It can be seen that general recommendations for optimization of separation in ion chromatography is application of chromatography exponential function criterion in combination with artificial neural networks retention model.     

厚朴酚键合硅胶液相色谱固定相的制备、表征与性能评价

通过γ-巯丙基三甲氧基硅烷(KH-590)的作用, 将具有抗菌功能的中草药厚朴的主要药用成分厚朴酚键合在硅胶表面上, 制备了厚朴酚键合硅胶液相色谱固定相. 采用红外光谱、元素分析和热重分析对该固定相进行了表征. 以苯同系物、5种吡啶、6种苯胺和8种芳香羧酸类化合物为溶质探针, 初步考察了该新型固定相的基本色谱性能, 研究了其对这些化合物的保留机理. 结果表明, 该固定相的反相色谱性能类似于十八烷基键合硅胶固定相(ODS), 分离原理与疏水性作用有关; 另外, 该固定相包含有别于疏水性作用的氢键作用、π-π电荷转移作用和偶极-偶极等作用, 多种作用力使其在分离某些可电离的碱性和酸性化合物时表现出更好的选择性和分离效果. 厚朴酚配体的多种作用位点对快速分离极性芳香化合物有重要贡献.     

Separation of Tetracycline Antibiotics by Hydrophilic Interaction Chromatography Using an Amino-Propyl Stationary Phase

In this work the potential of hydrophilic interaction chromatography (HILIC) is explored for the analysis of tetracycline antibiotics. The choice of the polar stationary phase is first discussed and it is demonstrated that aminopropyl stationary phases lead to higher efficiencies and peak symmetry than bare silica ones. The influence of the composition of the mobile phase is studied next : the concentration of the weaker solvent (acetonitrile), the nature and concentration of the more polar solvent (water or methanol), pH, the nature and ionic strength of the buffer. It is shown that high efficiencies are reached only with a citrate buffer that impairs the interactions with the residual silanol groups whatever the mobile phase pH is. We demonstrate that the citrate buffer strongly interacts with the cationic moiety of the aminopropyl stationary phase and thus reduces the accessibility of silanols. The separation of oxytetracycline, tetracycline and chlortetracycline is achieved in a few minutes at pH 3.5 or 5, with no peak tailing as usually observed in reversed phase liquid chromatography with an opposite elution order when compared with reversed phase liquid chromatography.     

Rapid Chiral Separation by Flow-Through Chromatography with a Biporous Stationary Phase

Enantiomer separation is an area of increasing importance in chemistry and in the pharmaceutical industry. Although liquid chromatography is one of the most practical processes for chiral resolution, the high mass-transfer resistance of most commercially available packings makes chiral resolution time-consuming. In this work, a novel chiral stationary phase (CSP) with wide pores was prepared by coupling bovine serum albumin to a biporous resin with triazine as a linker. The rigid biporous medium was fabricated by radical suspension copolymerization with solid granules and solvents as porogenic agents. Studies by scanning electron microscopy and mercury intrusion porosimetry revealed the matrix contained two types of pore—micropores smaller than 180 nm and macropores of 500–7300 nm. Because the macropores provide convective flow channels for the mobile phase, the chromatographic process can be operated at high flow rate with low back-pressure. The biporous CSP was applied to the resolution of d, l-tryptophan (Trp). When the flow velocity was as high as 1800 cm h^–1, d, l-Trp could still be separated. By comparison of the resolution of d, l-Trp on this CSP at high flow velocities with that predicted theoretically for conventional supports we concluded that the increased flow velocity had little effect on the resolution of enantiomers with biporous packings. The results indicate that the protein biporous CSP is promising for high-speed resolution of enantiomers.Revised: 8 October 2004 and 3 January 2005     

新型多孔材料用作色谱手性固定相

手性固定相是色谱法分离分析手性化合物的关键。近年来,随着材料科学的迅速发展,越来越多的新型手性材料被作为色谱固定相用于手性分离分析。本文综述了近5年来液相色谱、气相色谱和毛细管电色谱领域的新型手性固定相的研究进展,重点总结了基于手性多孔材料的新型手性固定相研究,最后对手性固定相的研究进行了总结与展望。     

Two Stabilized Calix[6]Cryptand Stereo Isomers used as Stationary Phases for Capillary Gas Chromatography

ABSTRACT

A couple of stabilized calix[6]cryptand steroisomers were synthesized by capping 1,3,5-trimethoxy-p-tert-butylcalix[6]arene with 1,1,1-tri(tosyloxyethoxyethoxymethyl)-propane and used as stationary phases for capillary gas chromatography. Their chromatographic characteristics and separation mechanism for aromatic positional isomers and polycyclic aromatic hydrocarbons are discussed.     

Extended Thermodynamic Approach to Ion Interaction Chromatography: Influence of Organic Modifier Concentration

Summary The influence of organic modifier and ion interaction reagent (IIR) concentrations on analyte retention in ion interaction chromatography (IIC) was investigated via a bivariate approach. The system examined is as follows: ODS-Hypersils was used as stationary phase; the eluent was a variable mixture of a phosphate buffer pH 2.1 and methanol ranging 0%–40% (v/v). The organic modifier decreases both the analyte and the IIR free energy of adsorption hence their interaction is lower when the organic modifier concentration is higher. Retention equations describe how these two factors interact with each another. The estimated equilibrium constant for the IIR adsorption corresponds to G° = –17.3 KJ mol^–1. This value is reliable because it makes sense physically. The chi-squared (k _calc – k _exp)² is 1.11E + 00 and 2.85E-02, for octopamine and 2-naphthalenesulfonate, respectively. Retention equations were compared with those obtained from the outstanding retention models in IIC. For the modelled system, the extended thermodynamic approach is able to explain experimental evidence that cannot be rationalised by existing retention models: it proves superior for fitting experimental data and is also able to predict when the purely electrostatic approach may work properly. In the absence of IIR the present retention equation reduces, as expected, to the relationship that describes the influence of organic modifier on retention behaviour in reversed-phase liquid chromatography.     

气相色谱键合固定相的制备及农药残留测定的应用研究

本文采用热反应键合法,将ＰＥＧ－２０Ｍ与４０５白色硅藻上载体进行热键合制备气相色谱键合固定相。用ＴＧ－ＤＴＡ法对固定相的键合量及温度特性进行研究,结果表明,键保固定相具有较好的色谱性能,能有效地应用于食品及农产品中多种有机磷类农药、氨基在农药以及拟除虫菊酯类农药残留量的分离测定。     

异喹啉酸衍生物配体交换色谱手性固定相的制备及应用

合成了2-(2-羟基十六烷基)-(S)-1,2,3,4-四氢-3-异喹啉羧酸手性选择子,并采用动态涂渍方法,制备了一种涂渍于ODS柱上的新型手性配体交换色谱固定相。采用醋酸铜水溶液为流动相,在柱温25℃和UV254nm检测条件下,拆分了16种D,L-氨基酸对映体,其对映体选择性α和分离度Rs分别在1.09~1.67和1.0~4.8之间,并观察到D-异构体在先,L-异构体在后的色谱流出顺序。讨论了柱温、流动相的流速、pH值、Cu2 浓度和NH4 对D,L-氨基酸对映体拆分的影响。     

表面接枝型离子色谱固定相的制备

以苯乙烯-二乙烯基苯微球为基质,建立了一种新型离子色谱固定相的制备方法。在基质微球表面合成一层聚缩水甘油甲基丙烯酸酯聚合物层(GMA),随后与甲胺及1,4-丁二醇二环氧甘油醚(BDDE)交替反应,与其表面接枝上带正电荷的季铵基团,可用于阴离子的分离。通过改变接枝反应的次数,控制交换树脂的交换容量。自制色谱固定相能够用于7种常规阴离子分离分析,并用于自来水中常规阴离子的检测。分离检测结果可与商用离子色谱柱相比,同时水负峰能与氟离子完全分离,不影响氟离子的定量检测。