Preparation and ion chromatographic properties of a new core-shell chromatographic support Al2O3/SiO2-10

A new stationary phase Al₂O₃/SiO₂-10 was prepared and characterized by XPS, XRD, SEM and surface analysis. The anion exchanger properties of this new stationary phase were investigated by the separation of inorganic anions in ion chromatography (IC). pH of the mobile phase, concentration and strength of the Lewis base of the elute, and the organic modifier of the mobile phase strongly affect the separation of inorganic anions, and anion exchange selectivities of the analyte on the new support are significantly different from quaternary ammonium styrene based anion exchangers. The result of separation of inorganic anions shows that the new stationary phase provides excellent column efficiency, well-defined chromatographic peaks and favorable retention times.     

Vitamin U-bonded stationary phase in capillary ion chromatography

A vitamin U-bonded stationary phase was prepared and the retention behavior of inorganic anions was examined using ion chromatography. Inorganic anions were retained on the vitamin U-bonded stationary phase under acidic as well as neutral eluent conditions in the ion-exchange mode. The elution order of the examined anions under neutral eluent conditions was nearly the same as that observed in common ion exchange mode, while the elution order observed under acidic eluent conditions was completely different from that observed in common ion exchange mode. The retention of the analyte anions under the neutral eluent conditions was due to the sulfonium groups of the vitamin U, while protonated primary amino groups caused retention of the analyte anions with different selectivity under acidic conditions. The retention factor of the analyte anions increased with decreasing eluent concentration under both eluent conditions. The present system was applied to the determination of bromide and nitrate contained in seawater.     

Silica based click amino stationary phase for ion chromatography and hydrophilic interaction liquid chromatography

A silica based amino stationary phase was prepared by immobilization of propargylamine on azide-silica via click chemistry. This readily prepared click amino stationary phase demonstrated good selectivity in separation of common inorganic anions under ion chromatography (IC) mode, and the triazole ring in combination with free amino group was observed to play a major role for separation of the anions examined. On the other hand, the stationary phase also showed good hydrophilic interaction liquid chromatography (HILIC) properties in the separation of polar compounds including nucleosides, organic acids and bases. The retention mechanism was found to match well the typical HILIC retention.     

Comparison of Reversed Stationary Phases for the Chromatographic Separation of Inorganic Analytes Using Hydrophobic Ion Mobile Phase Additives

Abstract

Alkyl-modified silica (RSi) and polystyrenedivinylbenzene (PRP-1) stationary phases are compared for the chromatographic separation of inorganic analyte anions and cations using hydro-phobic ions of opposite charge as mobile phase additives. Tetra-alkylammonium salts were used for anion separations and alkyl sulfonate salts for cation separations. Two major equilibria influence the retention of analyte ions on PRP-1. These are: retention of the hydrophobic ion on PRP-1 and an ion exchange selectivity between the hydrophobic counterion and the analyte ion. When using RSi retention is also influenced by ion exchange at residual silanol groups, which act as weak cation exchange sites. Mobile and stationary phase variables that influence analyte retention are identified. Optimization of these provides favorable eluting conditions for the separation of inorganic ionic analytes. Of particular interest is the potential use of PRP-1 and RSi columns for the separation of inorganic cations; conditions for the separation of alkali metals and alkaline earths are discussed.     

Polyoxyethylene as the stationary phase in ion chromatography

The present article reviews the use of polyethylene glycol (PEG) or polyoxyethylene (POE) as the stationary phase for the separation of inorganic anions in ion chromatography and discusses about the retention mechanisms involved in the separation of anions on the novel stationary phases. PEG permanently coated on a hydrophobic stationary phase retained anions in the partition mode and allowed us to use high-concentration eluents because the retention of anions increased with increasing eluent concentration for most of the eluents. This situation was convenient to determine trace anions contained in seawater samples without any disturbance due to matrices. Chemically bonded POE stationary phases retained not only anions but also cations. Anions were retained in the ion-exchange mode, although POE chains possess no ion exchange sites. The retention behavior suggested that eluent cations could be trapped among multiple POE chains via ion-dipole interaction, and that the trapped cations worked as the anion-exchange sites. Anions could be separated using crown ether, i.e., cyclic POE, as the eluent additive with a hydrophobic stationary phase, where analyte anions were retained via electrostatic interaction with the eluent cation trapped on the crown ether.     

Preparation of High‐capacity,Monodisperse Polymeric Weak Cation Exchange Packings Using Surface‐initiated Atom Transfer Radical Polymerization and Its Chromatographic Properties

A novel stationary phase for weak cation exchange (WCX) chromatography was prepared by "grafting from" strategy. Surface initiated atom transfer radical polymerization (ATRP) of acrylic acid (AA) was conducted in toluene medium, starting from the macromolecule initiators of poly(4‐vinylbenzyl chloride‐co‐divinylbenzene) (P_CMS/DVB) beads. The amounts of poly(acrylic acid) grafted chains with different ATRP formulations were calculated based on the elemental analyses. The poly(acrylic acid) grafted beads obtained with different ATRP formulations were tried as chromatographic packings in the separation of proteins by ion‐exchange chromatography. The effect of the poly(acrylic acid) grafted chain lengths on P_CMS/DVB beads for the separation of proteins was investigated in details. Simultaneously, characterization of the column was investigated as ion chromatographic stationary phase for the separation of inorganic cations. The results show that poly(acrylic acid) grafted columns had excellent performance for separation of proteins and inorganic cations. The highest of the dynamic capacity of the column was 35.55 mg/mL. The columns were provided with high column efficiency.     

A novel silica based click lysine anion exchanger for ion exchange chromatography

Ion chromatography (IC) is one of the most powerful analysis technologies for the determination of charged compounds. A novel click lysine stationary phase was prepared via Cu(I) catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) and applied to the analysis of inorganic ions. The chromatographic evaluation demonstrated good performance (e.g. the plate number of thiocyanate is ～50,000 plates m(-1)) and effective separation ability for the common inorganic anions with aqueous Na(2)SO(4) eluent. The separation mechanism was observed to be mainly dominated by ion exchange interaction. The retention of these analytes is highly dependent on the pH value of eluent. Compared with the lysine stationary phase prepared via the conventional manner, the click lysine exchanger demonstrated shorter retention time and better ion separation characteristics under the same chromatographic conditions, which is a great advantage for rapid separation and analysis of inorganic ions.     

Separation of inorganic anions on a triazole-functionalized ion exchanger in ion chromatography

The retention behavior of inorganic anions on a triazole-based stationary phase was first examined in ion chromatography. It was initially designed for hydrophilic interaction liquid chromatography and was simply prepared by introducing the triazole groups onto the surface of silica gel via click chemistry. Effective separation of common inorganic anions, including iodate, chloride, bromide, nitrate and iodide, was achieved with Na(2)SO(4) eluent. The logarithm of the retention factor of analytes was observed to be linear with the logarithm of the eluent concentration, and the slopes of the plots were almost the same as those of the ideal theoretical value. The eluent pH value in the range of 3.4-7.0 had little effect on the separation. The utility of the column was demonstrated for the determination of UV-absorbing anions in saliva and tap water.     

Determination of iodide in seawater and edible salt by microcolumn liquid chromatography with poly(ethylene glycol) stationary phase

An ion chromatography method for rapid and direct determination of iodide in seawater and edible salt is reported. Separation was achieved using a laboratory-made C30 packed column (100 mm x 0.32 mm i.d.) modified with poly(ethylene glycol) (PEG). Effects of eluent composition on retention behavior of inorganic anions have been investigated. Both cation and anion of the eluent affected the retention of analyte anions. The retention time of anions increased with increasing eluent concentration when lithium chloride, sodium chloride, potassium chloride, sodium sulfate, magnesium sulfate were used as the eluent, while it decreased with increasing eluent concentration when ammonium sulfate was used as the eluent. The detection limit for iodide obtained by injecting 0.2 microl of sample was 9 microg/l (S/N = 3). The present method was successfully applied to the rapid and direct determination of iodide in seawater and edible salt samples. Partition may be involved in the present separation mode.     

亲水作用色谱柱与阳离子交换树脂柱结合分离无机离子（英文）

A combination of hydrophilic interaction chromatographic(HILIC) column and a weakly acidic cation-exchange resin(WCX) column was used for simultaneous separation of inorganic anions and cations by ion chromatography(IC).Firstly,the capability of HILIC column for the separation of analyte ions was evaluated under acidic eluent conditions.The columns used were SeQuant ZIC-HILIC(ZIC-HILIC) with a sulfobetaine-zwitterion stationary phase(ZIC-HILIC) and Acclaim HILIC-10 with a diol stationary phase(HILIC-10).When using tartaric acid as the eluent,the HILIC columns indicated strong retentions for anions,based on ion-pair interaction.Especially,HILIC-10 could strongly retain anions compared with ZIC-HILIC.The selectivity for analyte anions of HILIC-10 with 5 mmol/L tartaric acid eluent was in the order of I-> NO-3 > Br-> Cl-> H2PO-4.However,since HILIC-10 could not separate analyte cations,a WCX column(TSKgel Super IC-A/C) was connected after the HILIC column in series.The combination column system of HILIC and WCX columns could successfully separate ten ions(Na+,NH+4,K+,Mg2+,Ca2+,H2PO-4,Cl-,Br-,NO-3 and I-) with elution of 4 mmol/L tartaric acid plus 8 mmol/L 18-crown-6.The relative standard deviations(RSDs) of analyte ions by the system were in the ranges of 0.02%-0.05% in retention times and 0.18%-5.3% in peak areas through three-time successive injections.The limits of detection at signal-to-noise ratio of 3 were 0.24-0.30 μmol/L for the cations and 0.31-1.2 μmol/L for the anions.This system was applied for the simultaneous determination of the cations and the anions in a vegetable juice sample with satisfactory results.     

Functionality-type distribution of poly(ethylene oxide) and poly(propylene oxide) macromonomers: Critical-chromatography study

Functionality-type distributions of macromomoners with poly(ethylene oxide) and poly(propylene oxide) chains are studied by chromatography under critical conditions. It is shown that, in the critical separation mode, separation of macromolecules with respect to size disappears and only information on the functionality-type distributions of the test samples may be derived. The critical conditions are determined experimentally with a normal phase (unmodified silica gel) for poly(propylene oxide) and with a reversed phase C₁₈ for poly(ethylene oxide). The experimental retention volumes for bifunctional macromolecules are in satisfactory agreement with the values calculated under approximation of the Gaussian chain model.     

Separation of inorganic anions by liquid chromatography with crown ether as eluent additive

Inorganic anions were separated on a reversed-phase stationary phase dynamically modified with crown ether as a selector in capillary ion chromatography. The eluent contained crown ether, acetonitrile and a salt. Free and cation-trapped crown ether molecules in the eluent were adsorbed on a hydrophobic stationary phase such as triacontyl-functionalized silica (C30). The eluent cations trapped on crown ether worked as the ion-exchange sites, where the eluent anions and the analyte anions were competing for electrostatic interaction. The sizes of crown ether and the salt cation affected the retention of analyte anions. The concentrations of acetonitrile and crown ether as well as the eluent anion also affected the retention of analyte anions. An aqueous solution containing 18-crown-6-ether, potassium salt and acetonitrile achieved larger retention for analyte anions. Effects of the eluent conditions on the retention of analyte anions were examined in detail.     

Ion-chromatographic behavior of alkali metal cations and ammonium ion on zirconium-adsorbing silica gel

The preparation and evaluation of zirconium-adsorbing silica gel (Zr-Silica) as an ion-exchange stationary phase in ion chromatography for inorganic anions and cations was carried out. The Zr-Silica was prepared by the reaction of silanol groups on the surface of the silica gel with zirconium butoxide (Zr(OCH2CH2CH2CH3)4) in ethanol. The ion-exchange characteristics of the Zr-Silica were evaluated using 10 mM tartaric acid at pH 2.5 as eluent. The Zr-Silica was found to act as a cation-exchanger under the eluent conditions. The retention behavior of alkali and alkaline earth metal cations was then investigated. The Zr-Silica column was proved to be suitable for the simultaneous separation of alkali metal cations and ammonium ion. Excellent separation of the cations on a 15 cm Zr-Silica column was achieved in 25 min using 10 mM tartaric acid as eluent.     

Dicationic imidazolium ionic liquid modified silica as a novel reversed‐phase/anion‐exchange mixed‐mode stationary phase for high‐performance liquid chromatography

A dicationic imidazolium ionic liquid modified silica stationary phase was prepared and evaluated by reversed‐phase/anion‐exchange mixed‐mode chromatography. Model compounds (polycyclic aromatic hydrocarbons and anilines) were separated well on the column by reversed‐phase chromatography; inorganic anions (bromate, bromide, nitrate, iodide, and thiocyanate), and organic anions (p‐aminobenzoic acid, p‐anilinesulfonic acid, sodium benzoate, pathalic acid, and salicylic acid) were also separated individually by anion‐exchange chromatography. Based on the multiple sites of the stationary phase, the column could separate 14 solutes containing the above series of analytes in one run. The dicationic imidazolium ionic liquid modified silica can interact with hydrophobic analytes by the hydrophobic C₆ chain; it can enhance selectivity to aromatic compounds by imidazolium groups; and it also provided anion‐exchange and electrostatic interactions with ionic solutes. Compared with a monocationic ionic liquid functionalized stationary phase, the new stationary phase represented enhanced selectivity owing to more interaction sites.     

Evaluation of the thermal effect on separation selectivity in anion-exchange processes using superheated water ion-exchange chromatography

The thermal effect on retention and separation selectivity of inorganic anions and aromatic sulfonate ions in anion-exchange chromatography is studied on a quaternized styrene-divinylbenzene copolymer anion-exchange column in the temperature range of 40-120 °C using superheated water chromatography. The selectivity coefficient for a pair of identically charged anions approaches unity as temperature increases provided the ions have the same effective size, such that the retention of an analyte ion decreases with an increase in temperature when the analyte ion has stronger affinity for the ion-exchanger than that of the eluent counterion, whereas it increases when it has weaker affinity. The change in anion-exchange selectivity with temperature observed with superheated water chromatography has been discussed on the basis of the effect of temperature on hydration of the ions. At elevated temperatures, especially in superheated water, the electrostatic interaction or association of the ions with the fixed ion in the resin phase becomes a predominant factor resulting in a different separation selectivity from that obtained at ambient temperature.     

Comparison of liquid chromatographic behaviors on N-methylimidazolium functionalized ZrO(2)/SiO(2)-4 and N-methylimidazolium functionalized SiO(2) stationary phases

A new stationary phase N-methylimidazolium functionalized ZrO(2)/SiO(2)-4 (Zr/SilprMim) has been prepared. The chromatographic property of this stationary phase is investigated by ion chromatography (IC) with inorganic and organic anions, and normal phase HPLC with basic compounds and hydroxybenzenes. The effects of pH and the strength of Lewis base of eluent on separation of anions are studied. This new stationary phase is also compared with a N-methylimidazolium functionalized SiO(2) stationary phase (SilprMim). The results show that this new stationary phase can be used in analysis of inorganic anions with great prospects. At the same time, successful separations of some organic anions can be obtained by using phosphate buffer solution as mobile phase. This new stationary phase also has a distinct advantage in the separation of basic compounds in normal phase. But due to the presence of Lewis acid sites on the surface of ZrO(2)/SiO(2)-4, Lewis bases such as hydroxybenzenes adsorb very strongly on this new stationary phase, and Lewis acid sites can be masked or modified by the eluent that contain Lewis base groups.     

原子转移自由基聚合法制备新型亲水作用色谱固定相及其性能评价

以自制的6.0μm单分散大孔交联聚氯甲基苯乙烯-二乙烯基苯(Poly(4-vinylbenzylchloride-co-divi-nylbenzene),PCMS/DVB)微球为基质和引发剂,CuCl和自行合成的三[(2-二甲基氨基)乙基]胺(Tris[2-(dimeth-ylamino)ethyl]amine,Me6TREN)组成混合催化体系,使4-乙烯基吡啶(4-Vinyl pyridine,4-VP)在甲苯中进行原子转移自由基聚合,制得4-乙烯基吡啶聚合物,单体4-乙烯基吡啶的接枝率为8.55%。将该聚合物与正溴丁烷反应制得新型亲水色谱固定相。在亲水作用色谱模式下,流速1 mL/min,乙腈-水为流动相可分离5种芳胺化合物和4种酚类化合物。在离子交换色谱模式下,6 mmol/L Na2CO3-5.5 mmol/L NaHCO3为淋洗液可分别分离5种无机阴离子和4种短链有机酸。结果表明,此固定相对极性化合物和无机阴离子具有良好的分离性能,是一种性能优异的亲水作用色谱固定相。     

单分散树脂基质的弱阳离子交换色谱固定相的制备及其在生物大分子分离中的应用研究

采用分散聚合法制备种子和“一步种子溶胀聚合法”制备了粒径为6~15 μm的单分散多孔氯甲基苯乙烯-二乙烯苯微球。该微球经化学改性后得到一种亲水性良好的新型高效弱阳离子交换色谱固定相。详细考察了该固定相的表面亲水性、对标准蛋白的分离性能和盐的种类对蛋白质保留行为的影响。考察结果表明该固定相是一种性能优异的弱阳离子交换色谱固定相。将其应用于鸡蛋清中溶菌酶的快速分离纯化,纯化后的溶菌酶纯度高于96%,比活高达71184 U/mg。     

基于季铵化烯丙基缩水甘油醚改性的阴离子交换固定相的制备北大核心CSCD

制备了一种季铵化烯丙基缩水甘油醚(allyl glycidyl ether,AGE)改性聚合物基质的阴离子固定相应用于离子色谱系统。它是利用AGE与水解的聚甲基丙烯酸缩水甘油酯-二乙烯基苯poly(glycidylmethacrylate-divinylbenzene,GMA-DVB)微球表面残留双键通过表面自由基共聚,再通过N,N-二甲基乙醇胺(一种叔胺)进行开环反应制备得到的。通过考察有机叔胺类型、微球水解、单体和引发剂用量、反应温度和时间对7种阴离子分离性能的影响,优化了制备条件。采用扫描电镜、元素分析对所得阴离子固定相进行了表征。结果表明,采用预先水解的GMA-DVB微球(水解过程中微球表面丰富的环氧基团转化为羟基)相对于直接采用GMA-DVB微球有助于降低固定相的交换容量和微球自身的非离子吸附作用;通过淋洗液浓度和目标离子保留因子的拟合结果证实了该固定相保留机理为典型的离子交换作用。使用碳酸根淋洗液,在优化的色谱条件下,该固定相可在13 min内实现常见7种无机阴离子的基线分离,并表现出较高的柱效(Cl-理论塔板数为49000块/m)。该色谱柱实用性通过分析自来水实际样品进行了验证。     

C<Subscript>18</Subscript>-Free Organic–Inorganic Hybrid Silica Particles Derived from Sole Silsesquioxane for Reversed-Phase HPLC

Ethyl-bridged organic–inorganic hybrid silica particles were prepared via a sol–gel and hydrothermal synthesis approach using 1,2-bis(triethoxysilyl)ethane (BTESE) as the sole precursor, and triblock copolymer poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (P123) and dodecyltrimethylammonium bromide (DTAB) as combined templates. The morphology, pore structure, chemical composition and liquid chromatographic performance of the obtained materials were investigated in detail. The particles exhibit a high surface area of 1136.40 m²/g, together with a pore volume of 0.39 cm³/g and an average pore size of 2.30 nm. Used as stationary phase for high-performance liquid chromatography (HPLC), the particles without extra bonding either C₁₈ or C₈ can successfully separate a mixture of uracil, phenol, pyridine, methylbenzene, ethylbenzene and tert-butylbenzene. The obtained materials also show practical application in the separation of phthalate acid esters (PAEs), which are harmful to environment and human health. Although the columns packed with ethyl-bridged organic–inorganic hybrid silica show lower column efficiency and peak symmetry compared to commercial column, they have considerably higher chemical stability in alkaline mobile phase. The HSS column also possesses high mechanical stability which is similar to that of the commercial column.