Preparation and Chromatographic Properties of Some Chemically Bonded Phases for Reversed-Phase Liquid Chromatography

Abstract

Four different monomeric chemically bonded phases suitable for reversed-phase liquid chromatography have been prepared. Duplicate preparations, elemental analysis, post-treatment with TMS and chromatographic properties all indicate that maximum coverage has been obtained. The chromatographic activity of the silica surface is discussed on the basis of TMS-phases with various surface coverages. It is observed that logarithmic retention data for homologous series and different RP-phases-partially taken from the literature—form a set of straight lines with a common intersection point.     

The Characterisation of Chemically Bonded Chromatographic Stationary Phases by Thermogravimetry

This paper details a simple thermogravimetric procedure to determine the amount of ligand present on silica based chemically bonded stationary phases for HPLC and CEC. The weight loss observed from stationary phases between 150 and 600 °C was found to be directly proportional to carbon loading of the phase. Weight loss at lower temperatures was due to the removal of weakly bound solvent. The use of temperatures higher than 600 °C resulted in the condensation of surface silanol groups resulting in an artificially elevated carbon loading result. The procedure has been applied to a range of commercially available HPLC stationary phases and the results obtained for the carbon loading for each phase was within 3% of the value reported by the manufacturer. The data presented demonstrates that the procedure is accurate and precise over a rage of carbon contents typically observed for commercially available HPLC phases and is applicable to a range of silica supports and hydrophobic ligands.     

Comparison of Solvent Adsorption on Chemically Bonded Stationary Phases in RP-LC

The excess adsorption isotherms of organic modifiers (methanol and acetonitrile) from water on chemically bonded stationary phases were studied, using seven different packed columns with different organic ligand lengths from C4 to C30. Isotherms were measured using the minor disturbance method. Excess isotherms can give useful information about the structure of the stationary phase. The amount of “adsorbed” solvent can indicate the type of distribution mechanism.     

Survey and Trends in the Preparation of Chemically Bonded Silica Phases for Liquid Chromatographic Analysis

In order to increase chromatographic selectivity and to extend the analytical capability of reversed phase liquid chromatography (RP HPLC) many investigators have concentrated on the preparation of silica based column packings with chemically bonded phases (CBP). These phases have also been successfully used in sample preparation techniques, mainly in solid phase extraction (SPE). Although alkyl bonded phases (e.g., C₂, C₈, and C₁₈) are the most widely used packings in RP HPLC and SPE, various specific applications require CBPs with polar functional groups (e.g., -NH₂, -NO₂, -CN, and/or -OH). The solution of problems with separation of complicated chiral compounds was attempted by applying stationary phases with chiral selectors (e.g., cyclodextrins, Pirkle phases, crown ethers, etc.). On the other hand, packings with pseudo-membrane or liquid crystal properties have been utilized for the separation of various substances of natural origin. Porous silica is commonly used as a support in the preparation of CBPs. Its physico-chemical characteristics, such as: type and structure of siliceous matrix, porosity, type and concentration of silanol groups, as well as surface purity, strongly influence the density and structure of chemically bonded phases. Recognition of these properties is helpful in optimizing separation processes based on RP HPLC elution and/or extraction of substances with polar character.     

Preparative Hydrophobic Interaction Chromatography of Proteins Using Ether Based Chemically Bonded Phases

Abstract

This paper examines the use of 15–20 micron wide-pore silica-based ether bonded phases for the preparative hydrophobic interaction chromatography of proteins. In particular, silyl ethers are immobilized on large particle silica in an analogous manner to previously developed ether bonded 5 um analytical supports. The preparative supports are reproducibly prepared and exhibit constant chromatographic retention for at least five months of continual use. Preparative columns can be operated for protein chromatography with peak shapes and capacity as predicted by the Snyder gradient elution model. Moreover, similar retention times are obtained relative to those on the 5 um analytical columns, enabling the direct transition and scale-up of separation. Gradient optimization is seen to directly parallel that performed on 5 um bonded ether analytical columns. Acceptable chromatographic resolution was obtained with sample capacity of >15 mg protein/ml column volume using a repetitive injection technique. A column clean-up strategy is examined for rapid and safe removal of contaminants. An illustrative example of use of the bonded ether preparative columns is made by application to soybean trypsin inhibitor purification. Initial results are presented on a column-switching method for the analytical monitoring of preparative separation.     

键合型纤维素-苯基氨基甲酸酯手性固定相的制备及用于对映异构体拆分

采用化学键合法,利用4,4′-二苯基甲基二异氰酸酯作间隔臂,通过纤维素葡萄糖单元上2、3或6-位上的羟基将纤维素衍生物键合在氨丙基硅胶上,制备了键合型纤维素-苯基氨基甲酸酯手性固定相.同时,以微晶纤维素和苯基异氰酸酯为原料,合成了纤维素-三苯基氨基甲酸酯,并以未修饰的硅胶为载体,制备了涂敷型纤维素-三苯基氨基甲酸酯手性固定相.分别对键合型和涂敷型两类手性固定相进行了表征,并首次在纤维素-苯基氨基甲酸酯手性柱上拆分了安息香.     

键合型纤维素—苯基氨基甲酸酯手性固定相的制备及用于对映异构？…

采用化学键合法,利用４,４′－二苯基甲基二异氰酸酯作间隔臂,通过纤维素葡萄糖单元上２、３或６－位上的羟基将纤维素衍生物键合在氨丙基硅胶上,制备了键合型纤维素－苯基氨基甲酸酯手性固定相。同时,以微晶纤维素和苯基异氰酸酯为原料,合成了纤维素－三苯基氨基甲酸酯,并以未修饰的硅胶为载体,制备了涂敷型纤维素－三苯基氨基甲酸酯手性固定相。分别对键合型和涂敷型两类手性固定相进行了表征,并首次在纤维素－苯基氨基甲     

GC-MS Study of the Products Cleaved from RP-18 Chemically Bonded Phases for TLC During Thermal Modification

JPC – Journal of Planar Chromatography – Modern TLC -     

键合反相硅胶的简单制备方法

用柱层析分离天然有机物时，经常遇到的困难是：尽管选用了各种各样的淋洗剂体系，还是不能得到满意的分离效果。据笔者经验，这时若变换固定相（如将硅胶换成氧化铝、聚酰胺、硅藻土或采用反相键合硅胶等），可能会得到满意的分离效果。可见，丰富固定相的种类对有机化合...     

On the Thermal Instability of Selected TLC-Type Alkyl Chemically Bonded Stationary Phases and on its Physical Implications

JPC – Journal of Planar Chromatography – Modern TLC - In this paper we report our most recent experimental results relating to the thermal instability of selected alkyl chemically...     

Thermal Aromatization of Selected TLC-Type Aliphatic Chemically Bonded Stationary Phases,as Monitored by Use of HPLC-DAD

JPC – Journal of Planar Chromatography – Modern TLC - In our earlier papers we provided indirect experimental evidence strongly in support of our long-established hypothesis that...     

Influence of the Structure of Chemically Bonded C 18 Phases on HPLC Separation of Naproxen Glucuronide Diastereoisomers

Abstract

On the basis of Nucleosil-100 a series of materials with varying structure and different coverage density of chemically bonded C₁₈ phases (CBP) were prepared. The physico-chemical characteristics of these packings e.g. porosity and carbon content were studied by the BET method and CHN analysis. The structure of the C₁₈ CBP was determined by solid state CP/MAS NMR. The prepared packings and columns have been applied for HPLC separation of naproxen and its two diastereoisomeric conjugates with glucuronic acid. Material with monomeric C₁₈ CBP structure and with high coverage density has given good and reproducible separation results.     

Resolution of the Optical Isomers of Underivatisized Amino Acids on Chemically Bonded Chiral Phases by Ligand Exchange Chromatography

Abstract

A method for the direct separation of racemates by HPLC is described. A chiral stationary phase is synthesized, suitable for ligand exchange chromatography. L-proline is chemically bonded to silica gel via 3-glycidoxypropyltrimethoxysilane. The bonded support is loaded with Cu(II) ions as a complexing agent. Complete resolution of amino acid racemates can be obtained in less than ten minutes. α-values up to 3.5 are observed.     

Experimental Study of Model Bonded Stationary Phases for Liquid Chromatography I. Silica/Polyethyleneoxide

Abstract

Model bonded phases have been prepared by reaction of polyethyleneoxide of various molecular weights (200 < M < 5.10⁶) on silica.

The retention behavior of solutes on these bonded stationary phases for liquid chromatography depends on silica loadings, grafted molecule length, solute size and solvent nature. Different mechanisms such as dissolution effect in the grafted phase, adsorption on mineral support and steric exclusion due to the residual porosity of silica, are involved in the observed separations. An expression of elution volumes in relation with these mechanisms is proposed.

Chromatographic data and thermodynamic predictions are in good agreement.     

Experimental Study of Model Bonded Stationary Phases for Liquid Chromatography II. Silica/Polystyrene

Abstract

Mechanisms of separations performed on bonded phases in liquid chromatography are investigated by studying model grafted phases.

These phases are prepared by reaction of chlorinated silica with living anionic polystyrene of various molecular weights. Owing to thermodynamic predictions, an expression of the elution volume of various solutes on such packings and conditions for reverse-phase chromatography are proposed.     

高效液相色谱烷基硅胶键合固定相

综述了高效液相色谱烷基硅胶键合固定相研究的最新进展,参考文献４０篇。     

Preparation of Various Bonded Phases for HPLC Using Monochlorosilanes

Abstract

Monochlorosilanes have been prepared with yields of about 80% through a catalytic hydrosilylation of terminal olefins. Subsequently, the silanes are chemically bonded to silica to obtain: (i) n-octyldimethylsilyl bonded phases with reproducible surface coverage ranging from 0.8 to 3.5 μmol/m², (ii) propyldimethylsilyl bonded phases with different functional groups at the γ-position, all showing a nearly equal surface coverage of some 3.3 μmol/m², and (iii) n-alkyldimethylsilyl bonded phases with chainlengths ranging from 1 to 22 carbon atoms and with surface coverages ranging from 3.9 μmol/m² for RP-1 to 3.0 μmol/m² for the RP-22 bonded phase. A simplified model based on the pore structure of silica allows an explanation and estimation of the maximum surface coverage as a function of the chainlength of the bonded phase.     

高效液相色谱环糊精键合固定相

环糊精是由Ｄ（＋）－葡萄糖单元通过α－１，４糖苷键连接的环状齐聚糖，其最典型的性质是能与许多客体分子形成包容配合物。高效液相色谱环糊精键合固定相广泛用于对映异构体，非对映异构体，结构异构体和常规化合物的分离。     

Protein Separations on Octyl and Diphenyl Bonded Phases

Abstract

Two new packing materials specifically designed to handle high performance liquid chromatographic separations of proteins and peptides have been made. These are built on a 300 A pore silica gel to allow access of large molecular weight species, and are exhaustively bonded, first with an octyl or a diphenyl silane and final end-capping with trimethylsilyl groups. The media are called Protesil 300 Octyl and Protesil 300 Diphenyl. Their unique selectivity is shown with various samples of dipeptides and proteins. The Octyl phase has specific affinities for alkyl functionalities, the Diphenyl phase has specific affinities for aromatic functionalities. Loading and mass recovery studies have been done on these media to show their capabilities under the elution conditions shown in the various separations. Comments regarding their correct use have also been made.     

碳十八键合锆胶固定相的制备与色谱性能评价

用诱导聚合胶体凝聚法（PICA）制得的二氧化锆微球与碳十八三乙氧基硅烷反应制备了碳十八键合锆胶固定相（ODZ），评价了该柱填料的色谱性能，并用此固定相分离了中性和碱性化合物。