摘要:

The preparation, characterization and potential liquid chromatographic applications of various porphyrin-silica stationary phases are reviewed. These new phases are synthesized by covalently linking unsymmetrical tetraphenylporphyrin (TPP) derivatives (monocarboxyl- or monohydroxyl-), as well as native protoporphyrin IX (ProP) to appropriately derivatized silica support matrices. The porphyrinsilicas may be further modified by metallation with a wide range of central metal ions (e.g., Cu2+, Zn2+, Ni2+, Fe+3, In3+, Sn4+, etc.) by refluxing in the presence of metal ion salts. Columns packed with either metallated or unmetallated materials exhibit exceptionally high shape selectivity in the separation of polycyclic aromatic hydrocarbons (PAHs) and fullerenes owing to strong π-π interactions between such solutes and the immobilized porphyrin structures. Columns packed with metallated porphyrins, particularly In(III) and Sn(IV), may also be used for separation of anions, including aromatic carboxylates and sulfonates, via selective ligation reactions with the metal centers. Similar coordination chemistry can be exploited to achieve selective peptide separations through a combination of specific metal ion affinity reactions of certain amino acids (histidine, tryptophan) with given metal ion centers (i.e., Fe+3, Cu+2) and concomitant π-π interactions of aromatic amino acids with the immobilized conjugated macrocycle. In the area of peptide/protein separations, the metalloporphyrin-silicas may offer an attractive alternative to current immobilized metal ion affinity phases (IMAC), because of their exceptionally strong metal ion binding constants. This allows the columns to provide reproducible analytical and preparative separations without potential for metal ion contamination of the purified materials.

ISSN:1082-6076    

DOI:10.1080/10826079608015117

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper deals with studies on the optical resolution of glycyl-DL-amino acid dipeptides and diastereomeric dipeptides on three different chemically bonded chiral ligand exchange chromatography (LEC)-phases. The phases were prepared by binding L-proline or L-hydroxyproline to silica gel using different silanes as spacer. Using 10−5M copper(H) sulface as a mobile phase, eleven glycyl-dipeptides were resolved, nearly all of them with baseline separations. Several dipeptides containing two stereogenic centres were at least partially resolved into the four stereoisomers.

ISSN:1082-6076    

DOI:10.1080/10826079608015118

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Chiral HPLC stationary phases based on immobilized biopolymers (i.e., proteins, enzymes, antibodies etc.) are of growing importance for the separation and purification of enantiomeric compounds, especially in the areas of biological, pharmaceutical, and clinical chemistry. In the work described in this paper, several silica-immobilized serum albumin phases were synthesized and characterized by a variety of techniques. Low-temperature nitrogen adsorption isotherms were measured and employed to evaluate the surface characteristics of the stationary phases as a function of both the immobilization matrix and the surface modification chemistry. Elemental analysis and high resolution thermogravimetry were used to evaluate the surface coverages at each stage of modification. Based on these results, surface parameters such as the specific surface area, pore size distribution, bonding density, etc. were calculated, as well as the changes of these parameters as a function of the modification chemistry were analyzed. Different silicas of varying mean pore diameter from 30 nm to 400 nm were used.

ISSN:1082-6076    

DOI:10.1080/10826079608015119

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The comb-shaped polymer (ODAn) composed of a reactive terminal group and highly-orienting side-chain groups was prepared by telomerization using 3-mercaptopropyl trimethoxysilane and octadecylacrylate. The polymer was readily immobilized onto porous silica gels through a terminal reactive group. DSC indicated that the silica-supported polymer (Sil-ODAn) underwent crystal-to-isotropic phase transition on silica gels at a temperature range of 28–47°C (in the case of n = 27) in methanol. Polarity microscopic observation of the polymer showed the phase transition included a nematic liquid crystalline state. The packed column showed a remarkably higher separation factor for mixtures of planar aromatics (e.g. triphenylene andtrans-stilbene) and non-planar aromatics (e.g.o-terphenyl or cis-stilbene) at room temperatures than did the conventional hydrophobic stationary phases, i.e. octadecylated silica gels. In addition, the Sil-ODAncolumn showed remarkable temperature dependence on both retention capacity (k') and separation factor (a). The k'-temperature and α-temperature plots showed distinct bending at temperatures around the phase transition temperature of immobilized ODAn. These results indicate that the selective retention for planar compounds is related to highly-orienting structure formed from long-chain alkyl groups. This paper discusses the molecular recognition mechanism using additional chromatographic behaviors and MOPAC calculation.

ISSN:1082-6076    

DOI:10.1080/10826079608015120

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A zwitterion-exchange stationary phase (ZIXSP) was prepared for the separation of the mixture of organic bases, organic acids and amino acids by high performance liquid chromatography (HPLC). It was synthesized by the reaction of cyanuric chloride with sulfanilic acid and then bonded onto the silica gel on which the silane coupling agent was prebonded. The chromatographic behaviours of the prepared ZIXSP revealed that the capacity factors of each analyte varied with the pH value of the mobile phase. By applying the concept of acid-base equilibrium the correlation between the capacity factor on the ZIXSP and pH of the mobile phase could be explained reasonably. Based on our results, it is concluded that ZIXSP is a zwitterion exchanger that additionally provides π-π charge-transfer interaction and hydrophobic interaction functions.

ISSN:1082-6076    

DOI:10.1080/10826079608015121

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A low temperature glassy carbon (LTGC) stationary phase coated on porous glassy carbon and zirconium oxide is chromatographically evaluated and compared to an uncoated porous glassy carbon stationary phase. The curing temperature of the LTGC was chosen to produce a surface having a reversed phase type retention mechanism. The LTGC coating of the porous glassy carbon reduced retention due to dispersive interactions while maintaining a similar retention mechanism as the untreated porous glassy carbon phase. The LTGC-coated zirconia produced an efficient column with classical reversed-phase retention behavior.

ISSN:1082-6076    

DOI:10.1080/10826079608015122

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Silica immobilized bovine serum albumin (BSA) has been synthesized and studied chromatographically using D, L-tryptophan and L-Kynurenine. Site specific and background interactions have been measured as a function of temperature and treatment with methanol. The results indicate that solvent entrapment in the interior hydrophobic region of the protein may lead to small changes in conformation and/or dynamics which influence the site specific binding of the protein and hence changes in chromatographic retention. The entrapped solvents appear to be thermodynamically and kinetically stable such that their influence on the protein persists at elevated temperatures and over hundreds of column volumes of aqueous buffer eluent.

ISSN:1082-6076    

DOI:10.1080/10826079608015123

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

It is important to elucidate the effect of the support on retention when investigating the retention mechanism in reversed phase liquid chromatography. The objective of this research was to examine how octadecyl-modified phase can control the unique nature of Titania. Titania was synthesized in our laboratory by the sol-gel method. Octadecyl-modified Titania was prepared by silylation with a octadecyltriethoxysilane. By using anionic, cationic. acidic and basic solutes, the retention behaviours of the Titania and the octadecyl-modified Titania were determined under reversed phase conditions. In the use of aqueous methanol mobile phases containing acetic acid-sodium acetate or bicine-sodium hydroxide buffer, we observed that the Titania synthesized behaved as an amphoteric ion exchanger, and that the retention behaviours of the octadecyl-modified Titania were significantly influenced by octadecyl-modification. The effect of octadecyl-modification on retention was ascribed not only to octadecyl groups but also silanol groups, which were formed by silylation. The retention behaviour as a whole, however, was clearly based on behaviour as an amphoteric ion-exchanger. Thus, we concluded that the octadecyl-modified phase, although it really influenced the retention behaviour, could not accomplish controlling the amphoteric ion exchange ability of the Titania in these experiments.

ISSN:1082-6076    

DOI:10.1080/10826079608015124

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A new amide-functionalized silica stationary phase, Supelcosil ABZ−Plus, suitable for reversed phase HPLC applications, was characterized by X-ray photoelectron spectroscopy (XPS), solid-state29Si and13C CP/MAS NMR and FTIR. The degree of hydration of this material was found to be much higher compared to amide-functionalized silica phases prepared by acid chloride treatment of aminopropylsilylated silica reported earlier and also compared to conventional C18reversed phase columns. The liquid chromatographic performance of this ABZ+Plus column was found to be superior to the C18columns, especially for polar analytes. The enhanced selectivity and better peak shape with this ABZ−Plus material was attributed to greater compositional differences between the surface and mobile phases coupled with more effective shielding of residual silanols and a more oriented alkyl chain structure.

ISSN:1082-6076    

DOI:10.1080/10826079608015125

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:1082-6076    

DOI:10.1080/10826079608015106

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor