New Principles of Ion-Exchange Techniques Suitable to Sample Preparation and Group Separation of Natural Products Prior to Liquid Chromatography

Abstract

A Gentle method of group separation of low molecular weight hydrophilic natural products is reported. The method is based on separation of the compounds according to their net charge at different pH values using different types of ion-exchange columns connected in series. Precolumns retaining interfering compounds are used in some cases. Elution of the compounds retained on the columns is performed by use of volatile eluents. The elution principle for two of the ion-exchangers in question is removal of the charges on the column materials while for the third column the positive net charge on the compounds retained is removed. Thereby, the total amount of ions retained on the different columns is released and eluted into small volumes, which after evaporation leaves the ions as well defined salts. The method is experimentally simple and efficient to separation of natural products into groups suitable to direct use in sensitive methods of analysis as e.g. high-performance liquid chromatography and gas chromatography. Combinations of these column chromatographic methods have been adpated for micro or semimicro determinations of naturally occurring compounds, e.g., aromatic choline esters, amines, amino acids and esters of phenolic carboxylic acids. The methods seem to be general practicable for group separation of low molecular weight hydrophilic compounds.     

Boron Separation by the Two—step Ion—Exchange for the Isotopic Measurement of Boron

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Measurement of Salicylic Acid by a High-Performance Liquid Chromatography Procedure Based on Ion-Exchange

An improved method for the detection and quantification of salicylic acid is described. This procedure utilised a high-performance liquid chromatography (HPLC) approach based on ion-exchange, coupled to a multi-detector system. This ameliorated the problems associated with resolution that are a characteristic feature of other methodologies. Furthermore, the increased sensitivity of this procedure supported a mini-scale format, which was both rapid and convenient. As the eluent from the ion exchange column was converted to water in the suppressor, this separation technique could also be linked directly to mass spectroscopy, providing more powerful characterization.     

Influence of Synergistic Effects on Ion-Exchange Chromatographic Separation of Proteins

Formation of strong bonds between proteins and polyelectrolyte chains of ion-exchange sorbents gives rise to synergistic effects in multicomponent sorption and chromatographic separation of proteins. A series of heteronetwork-cross-linked polymeric bases with varied content of ionic groups was prepared. Consecutive sorption and cosorption of insulin and -lactalbumin on these materials were studied.     

Ion-Exchange Chromatographic Supports Obtained by Formation of Polyelectrolyte Multi-Layers for the Separation of Proteins

Summary High performance liquid chromatography (HPLC) was used to study the mechanism of formation of polyelectrolyte multilayers on porous silicas. The coatings were produced by alternating the adsorption of positively and negatively charged polymers. The stationary phases formed by adsorbing a single layer, double layers and triple layers were tested by studying the elution behavior of model proteins. The double polymer coating was achieved by adsorbing first a polycation such as hexadimethrine bromide (HB) on the HPLC silica support and then a polyanion such as dextran sulfate (DS) on the cationic layer formed. The retention properties of this support are mainly those of a cation exchanger as the negatively charged proteins were strongly retained while positively charged ones were weakly adsorbed. This work demonstrated the importance of the first underlying layer as the retention behavior of proteins was greatly affected by the properties of this coating. The triple polymer coating was achieved by adsorbing the polycation (HB) on the double layer coating (HB-DS). Its retention behavior was that of an anion exchange support. The HB-DS stationary phase displayed good chromatographic performances, with an adsorbed layer relatively stable. The polyelectrolyte multilayer coating procedure was useful to easily synthesize cation-exchange supports for the separation of basic proteins.     

Semi-Preparative High-Performance Liquid Chromatographic Separation of Potato Glycoalkaloids

Abstract

A semi-preparative high-performance liquid chromatographic method has been developed to separate crude mixtures of the potato glycoalkaloids α-chaconine, α-solanine, commersonine and demissine. Milligram quantities of each substance can be obtained within an 8 hour period. A Zorbax semi-preparative NH₂ column and a solvent system of tetrahydrofuran-water-acetonitrile (55:20:25) were employed for the separation. The flow rate was 1.0 ml/min. Glycoalkaloid separations were monitored using both refractive index and ultraviolet detection (215 nm). Further analyses of these glycoalkaloids were done using analytical high-performance liquid chromatography (HPLC) and thin-layer chromatography (TLC) to check compound purity and identity.     

Ion-Exchange Chromatographic Separation of Anions on Hydrated Bismuth Oxide Impregnated Papers

Abstract

A comparative study of the chromatographic behaviour of anions, iodide, sulphide, phosphate, arsenate, arsenite, vanadate, chroraate, dichromate, thiosulphate, thiocyanate, ferricyanide and ferrocyanide on papers impregnated with hydrated bismuth oxide and untreated Whatman no, 1 papers has been made by employing identical aqueous, non-aqueous and mixed solvent systems. Sharp and compact spots were obtained with impregnated papers whereas the opposite applied to plain papers. Various analytically important binary and ternary separations are reported.     

Ion-Exchange Preconcentration and Separation of Trace mounts of Platinum and Palladium

ABSTRACT

The preconcentration and separation of platinum and palladium from weakly acidic solution (pH=4) were done on microcolumn packed with Cellex-T resin. Selective platinum elution from the column was performed with 0.01 mol/l glycine solution at pH=12, while for palladium elution 1.2 mol/l thiourea (pH=0.5) or 4.0 mol/l potassium thiocyanate (pH=1) may be used. As the detection technique was used either FAAS or GFAAS, depending on the concentration of studied metals in the eluate.     

金属蛋白的提取分离技术

微量元素在生命活动中起着十分重要的作用。体内微量元素(主要指金属元素)水平的反常、存在形态的变化以及特定的金属酶、金属蛋白的表达、定位、结构和功能等方面的变化常常与某些病理状态相关,甚至是关键的病理环节,所以对生物体系中金属蛋白的定位、含量、化学形态及其结构的高通量分析是生命科学研究领域的重要课题。本文介绍并比较了各种金属蛋白的提取、分离方法(包括高效液相、毛细管电泳和电泳技术)及与之对应的元素分析技术(包括激光剥蚀(LA)-等离子体电感耦合质谱(ICP-MS)、同步辐射(SR)-X射线荧光(XRF)技术等),主要介绍了各种电泳方法在金属蛋白分离中的应用。同时评价各种方法对蛋白结合金属的影响,针对方法的局限性提出了可能的解决办法。     

NBD-Cl as a Post-Column Reagent for Primary and Secondary Amines after Separation by Ion-Exchange Chromatography

In this study 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) is proposed as a post-column derivatization (PCD) reagent for the fluorescence detection of aliphatic primary and secondary amines after HPLC separation. Five primary (methylamine, isoamylamine, 2-phenylethylamine, putrescine, and histamine) and one secondary amine (dimethylamine) were separated isocratically on a cation-exchange column using HNO₃ (5 × 10^?3 mol L^?1) as the mobile phase. Post-column derivatization was based on two steps: 1) the derivatization of amines with NBD-Cl in alkaline medium, and 2) the acidification of the resulted mixture in order to minimize the background signal of the reagent and improve dramatically the sensitivity and determination range. The variables of the post-column reaction (concentration of NBD-Cl, buffer concentration and pH, reaction temperature, concentration of HCl, flow rates of the reagents) were thoroughly investigated. Critical chromatographic parameters such as the concentration of HNO₃, the percentage of organic solvent, and the column temperature were also examined to achieve adequate separation. An internal standard of 1,7-diaminoheptane was used. The developed post-column method provides the ability for a fully automated analysis, low detection limits (LODs 20–100 µg L^?1 with S/N = 3), and it requires less sample preparation. The applicability of the proposed analytical scheme was demonstrated by the determination of histamine (HIS) in tuna fish tissues according to US Food and Drug Administration (FDA) guidelines.     

Studies on the Ion-Exchange Chromatographic Separation of L-Ascorbic Acid and Oxalic Acid

L-Ascorbic acid and oxalic acid could be successfully separated with a column of 8% cross-linked sulfonated polystyrene cation-exchange resin in hydrogen form, and eluted with 0.01% aqueous solution of nitric acid, sulfuric acid, or phosphoric acid. Among the mineral acids used, nitric acid showed the best separatory effect. The minimum detectable quantities of the acids were 0.05 μg and 0.5 μg per 0.5 ml sample solution for L-ascorbic acid and oxalic acid, respectively. Under this condition, the acids could be detected by using automatic UV-monitor apparatus.     

Separation of Monosulfated Bile Acids by High-Performance Liquid Chromatography

Abstract

Separation of 3-, 7- and 12-monosulfates of cholate, chenodeoxycholate, deoxycholate, lithocholate and ursodeoxycholate and their glyco- and tauro-conjugates by high-performance liquid chromatography on a reversed phase column has been carried out. Effects of pH and salt concentration of a mobile phase on the k' value of sulfated bile acids were investigated with the μBondapak C₁₈ and ODS SC-02 columns. The 3-sulfated bile acids were efficiently separated on ODS SC-02 using three aqueous ammonium carbonate/acetonitrile systems. The chromatographic behaviors of 7-and 12-sulfated bile acids are also briefly discussed.     

Separation of Ramipril Optical Isomers by High-Performance Liquid Chromatography

Abstract

High-performance liquid chromatographic methods for determining the optical purities of ramipril, a novel angiotensin converting enzyme inhibitor, and its synthetic intermediates have been developed. Analytical procedures were established for the resolution of optical isomers of two moieties, precursor I and precursor II, used for the preparation of ramipril. No occurrence of racemization during condensation reaction of the two precursors could be unambiguously confirmed by the proposed methods. On the basis of analytical data ramipril bulk material proved to be optically pure.     

Novel Orientation Techniques for the Preparation of High-Performance Materials from Semiflexible Polymers

Abstract

A technique is described for postponing the formation of anisotropic domains in semiflexible polymers so as to better orient them along a common direction. A theory has been developed to provide a foundation for this approach and guidance on carrying it out experimentally, and is described in outline form. The primary advantage of this processing route is the improved mechanical properties accompanying the increased orientation. This is illustrated by increases in moduli and ultimate properties of films of some cellulosics, polyisocyanates, and the protein collagen in the form of gelatin.     

复杂生物体系中蛋白质高效分离分析技术的新进展

继人类基因组计划完成之后,作为一种新的研究策略,蛋白质组学在生命科学研究中发挥着愈来愈重要的作用。由于生物体系的复杂性和多样性,使得分离效率高、灵敏度高、通量高和动态范围宽的分离分析技术平台的研究和应用已成为蛋白质组学研究的重点和热点之一。着重介绍了近年来应用日益广泛的多维色谱预分离、毛细管液相色谱-质谱联用、毛细管电泳及其与质谱联用等高效分离分析技术在复杂生物体系的蛋白质分析中的最新进展。引用相关文献40篇。     

高效毛细管电泳法手性拆分奥昔布宁对映体

以羟丙基-β-环糊精（HP-β-CD）作为手性选择剂,采用毛细管区带电泳模式,对盐酸奥昔布宁对映体进行手性分离,比较了β-CD和 HP-β-CD之间对药品的分离能力,考察了手性选择剂的浓度、背景电解质的pH 值、柱温、分离电压和三羟甲基氨基甲烷（Tris）在背景电解质磷酸盐中的用量等因素对盐酸奥昔布宁对映体分离的影响,在优化条件下,使盐酸奥昔布宁对映体达到基线分离。结果表明该方法重现性好、简便、快捷、实用性强、具有良好的应用前景。     

Ion Exchange Separation Techniques for NAA of Refractory Metals

Radiochemical separation methods have been applied for the neutron activation analysis of impurities in four high-purity refractory metals, Ta, Nb, W and Mo. Impurities in the metals of Ta, Nb and W can be separated into groups using anion exchange resin with HF and/or a mixture of HF acid and HCl, but those in Mo is done using both anion and cation exchange resins. The coprecipitation of U with Th in HF media is also investigated.     

Ionic Liquids as Mobile Phase Additives for Separation of Nucleotides in High-Performance Liquid Chromatography

Ionic liquids are a type of salts that are liquid at low temperature (＜100℃). Because of their some special properties, they have been widely used as new “green solvents” for many chemical reactions and liquid-liquid extraction in the past several years. In this paper, a new method for the separation of nucleotides is developed and the essential feature of the method is that 1-alkyl-3-methylimidazolium salts are used as mobile phase additives, resulting in a baseline separation of nucleotides without need of gradient elution and need of organic solvent addition as currently used in RP-HPLC. This study shows the potential application of ionic liquids as mobile phase additives in reversed-phase liquid chromatograohy.