Separation of T-MAZ ethoxylated sorbitan fatty acid esters by reverse phase chromatography

Summary The method for determination of T-MAZ ethoxylated sorbitan fatty acid esters is described. This work demonstrates that with a less retentive C₈ alkyl bonded phase packing, reverse phase chromatography can be used to analyze nonionic polymer mixtures with a molecular weight range of 900 to 1500. Using a gradient elution, a complete separation of T-MAZ oligomers was achieved, comparable to that obtained by Supercritical Fluid Chromatography (SFC). Isocratic elution is used to quantify T-MAZ and the detection limit is 321 ppm, which is acceptable for polymers with high molecular weights and no UV-absorbing chromophores. This work also shows the comparison of the separations of T-MAZ using gel permeation chromatography and reverse phase chromatography.     

Reversed-phase and cation-exchange chromatography on a new poly(styrene-divinylbenzene) high capacity,weak cation-exchanger

Summary A weak cation-exchanger for high-performance liquid chromatography is obtained by oxidation of either poly(methylstyrene-divinylbenzene) or of poly(chloromethylstyrene-divinylbenzene). Reaction conditions were optimised to yield an exchange capacity of about 4meqg^–1 dry resin. The material was evaluated chromatographically as a function of pH, organic modifier, temperature and flow rate. A combination of ionexchange and hydrophobic interaction between the solutes and the packing material was observed. This could be used to provide more options for realising chromatographic separations. Some chromatograms of heterocyclic bases, nucleosides, nucleotides and amino acids are shown.     

Options for rapid analysis of peptides and proteins, using wide-pore, superficially porous, high-performance liquid chromatography particles with unique bonded-phase ligands

The large size and complexity of many proteins constrains the reversed-phase high-performance liquid chromatography packings that are useful for their separation. Wide-pore, superficially porous, silica-based packings with solid 4.5-microm cores and a 0.25-microm porous outer layer (Poroshell) demonstrate a variety of characteristics that are beneficial for the separation of proteins. A shorter diffusion distance allows separations of large molecules at high linear velocities. This benefit over totally porous particles is clearly shown using separations of a peptide-protein standard. The structure and reduced surface area (4.5 m2/g) of these superficially porous particles simplifies interactions with its surface, resulting in improved peak shapes and resolution. Specialized bonding chemistries for low- and high-pH operation may be used to change band-spacing and achieve atypical separations. These rapid analysis options are demonstrated using protein standards and very high molecular weight glycosylated proteins including intact monoclonal antibodies, IgM, alpha2-macroglobulin, and glycophorin. In liquid chromatography-mass spectrometry analysis of a myoglobin peptide digest, bidentate-C18-bonded superficially porous packings achieve complete runs in 4 min and demonstrate an elution pattern that is unique from that of material bonded with sterically protected C18 ligands.     

Effects of solutions used for storage of size-exclusion columns on subsequent chromatography of peptides and proteins

The effects of storage of size-exclusion column packing materials in methanolic or azide-water solutions on subsequent separations were tested. Three commercially available columns were used in these studies; the Toyo-Soda Bio-Sil TSK 125, Bio-Sil TSK 250 and the DuPont Bio-Series GF-250. Upon initial chromatography, all three columns bound up to 760 micrograms of cytochrome c tryptic peptides. Sample binding to packing material is probably a function of the positively charged basic groups on peptides or proteins interacting with silanol groups. The larger the peptide, the less the opportunity for silanol-charged group interaction, hence, less binding. Initial samples introduced to a new column occupy the binding sites. Equilibration with neat methanol removes the bound protein revealing sites which bind sample. After absorption of peptides to binding sites on the packing material, storage in neat methanol regenerates the binding sites. Storage in 10% methanol diminished the binding phenomenon, but storage in azide-water reduced binding to a range below detection at the microgram level. Our recommendation to users of size-exclusion chromatographic columns is that one satisfy the absorption capacity of a new column by injecting a sufficient quantity of a basic peptide standard or other convenient sample to reduce available binding sites before using the column for important separations. Store columns in azide-water or 10% methanol to prevent the regeneration of exposed silanol groups.     

Evaluation of the porous structures of new polymer packing materials by inverse size-exclusion chromatography

A highly cross-linked porous polymer resin based on styrene-divinylbenzene matrix with pores created by the use of micellar imprinting technique was used as chromatographic packing material. Its performance as a column packing material in inverse size-exclusion chromatography was compared with a non-imprinted resin of the same polymer matrix. The porous structures (the pore size and the porosity) of the resins in the dry and wet states and their relationships with the elution volume of probe solutes (alkanes and polystyrene standards) were established. Characteristic properties of the resins such as specific pore volume, specific surface area and porosity are compared with results obtained by other methods of characterization such as mercury intrusion porosimetry, solvent regain and nitrogen sorption. The results show that the new porous resin can be used in the separation of small molecules. The separation is based on the size of the molecules, and the larger pores (meso- and macropores) in the porous resin can provide a much easier access to the smaller pores (micropores) which are useful in the chromatographic separations.     

硅胶基质高效液相色谱填料研究进展

高效液相色谱(HPLC)不仅是一种有效的分析分离手段,也是一种重要的高效制备分离技术。色谱柱是HPLC系统的核心,不同性能的填料是HPLC广泛应用的基础。硅胶是开发最早、研究最为深入、应用最为广泛的HPLC固定相基质,其制备方法主要有喷雾干燥法、溶胶-凝胶法、聚合诱导胶体凝聚法及模板法等。近年来,亚2μm小粒径硅胶、核-壳型硅胶、双孔径硅胶、介孔性硅胶、有机杂化硅胶等新型硅胶应用于HPLC并取得了色谱分离技术的飞速发展,例如基于亚2μm填料的超高压液相色谱技术、基于核-壳型填料的快速分离技术、基于杂化硅胶填料的高温液相色谱技术等。硅胶经表面化学键合、聚合物包覆等有机改性可制得先进的大分子限进填料、温敏性填料、手性填料等,大大扩展了HPLC的应用范围。本文对液相色谱用硅胶的制备方法、改性与修饰方法以及硅胶基质固定相的评价方法加以系统综述,概述了新型硅胶在HPLC中的应用进展,并对硅胶基质填料的发展方向与应用前景进行了展望。     

A simple procedure for the preparation of fritless columns by entrapping conventional high performance liquid chromatography sorbents

A rapid and direct method for immobilizing conventional high performance liquid chromatography (HPLC) packing material inside fritless capillaries has been developed. Due to the simple composition of the entrapment matrix (tetraethoxysilane, alkyltriethoxysilane, ethanol and water), straightforward manufacturing procedure and modest equipment requirement, the method can readily be transferred to any laboratory and easily automated. The entrapment procedure has minimal influence on the structure and chromatographic properties of the original reverse-phase sorbent. Various immobilization solutions have been tested, and a comparison between columns entrapped with different immobilization mixtures and conventional packed capillaries is presented. High efficiency separations were obtained using tert-butyl-triethoxysilane entrapped columns in both capillary electrochromatography (reduced plate heights of 1.1-1.4 were measured) and microliquid chromatography (reduced plate heights of 2.2-2.6 were observed) formats. Elimination of frits, stabilization of the packed bed and on-the-fly customization of column length render mechanically robust columns that are remarkably stable over time, from which manufacturing imperfections can be removed easily.     

High temperature fast chromatography of proteins using a silica-based stationary phase with greatly enhanced low pH stability

Reversed-phase liquid chromatography (RPLC) is very widely used for the separation and characterization of proteins and peptides. A novel type of highly stable silica-based stationary phase has been developed for protein separations. A dense monolayer of dimethyl-(chloromethyl)phenylethyl)-chlorosilane (DM-CMPES) on the surface of silica is "hyper-crosslinked" with a polyfunctional aromatic crosslinker through Friedel-Crafts chemistry resulting in stationary phases with extraordinary stability in acidic media. Elemental analysis data confirm the high degree of cross-linking among the surface groups. The hyper-crosslinked phases are extremely stable under highly acidic mobile phase conditions even at a temperature as high as 150 degrees C. A wide-pore (300 A) material made in this way is used here to separate proteins by a reversed-phase mechanism and compared to a commercially available "sterically protected" C18 phase. For small molecules, including neutral and basic compounds, these crosslinked phases give comparable peak shape and efficiency to the commercial phase. Our results show that no pore blockage takes place as commonly afflicts polymer coated phases. In consequence, protein separations on the new phases are acceptable. Using strong ion-pairing reagents, such as HPF6, improves the separation efficiency. Compared to the commercial phases, these new phases can be used at lower pHs and much higher temperatures thereby enabling much faster separations which is the primary focus of this work. Better efficiency for proteins was obtained at high temperature. However, at conventional linear velocities the instability of proteins at high temperature becomes a problem which establishes an upper temperature limit. Uses of a narrowbore column and high flow rates both solves this problem by reducing the time that proteins spend on the hot column and, of course, speeds up the separation of the protein mixture. Finally, an ultrafast gradient (<1 min) protein separation was obtained by utilizing the high temperature and thus high linear velocities afforded by the extreme stability of these new phases. The phases are stable even after 50h of exposure to 0.1% TFA at 120 degrees C. This paper is dedicated to the memory of Csaba Horvath whose work in high temperature HPLC inspired the development of the stationary phases described here.     

High-performance membrane chromatography of serum and plasma membrane proteins.

Porous discs made of poly(glycidyl methacrylate) were used for high-performance membrane chromatography (HPMC) of proteins. In model experiments, separations of standard proteins by anion-exchange HPMC using a DEAE disc were carried out. The influences of sample distribution and disc diameter and thickness on separation performance were studied. The separation disc allowed a scaling-up from analytical (diameter 10 mm) to semi-preparative (diameter 50 mm) dimensions. In an application study, separations with anion-exchange and affinity HPMC were carried out using different complex samples such as rat serum and plasma membrane proteins. In all experiments the results on poly(glycidyl methacrylate) discs were comparable to those achieved on adequate high-performance liquid chromatographic (HPLC) columns. However, the separations on HPMC discs could be carried out faster than corresponding separations on HPLC columns. The pressure drop on the discs was low even at high flow-rates. The experiments show that the poly(glycidyl methacrylate) discs used are especially suitable for the isolation of proteins and other biopolymers which occur in a diluted state in complex mixtures.     

新型大孔硅质酰胺型聚合物键合相的制备及其对蛋白质的分离

大孔硅胶与乙烯基硅烷反应后,再与甲基丙烯酰胺和二乙烯基苯共聚成一种新型分离蛋白质的色谱柱填料。考察了这种色谱填料对蛋白质的分离能力,认为其具有柱效高、惰性好和分离效率高的优点,聚合物键合相的制备重复性好。并探讨了流动相中离子强度和ｐＨ值对蛋白质分离的影响。     

稠环芳烃在烷基膦酸改性锆镁复合氧化物固定相上的反相液相色谱保留行为

 以稠环芳烃为探针,考察了烷基膦酸改性锆镁复合氧化物材料的反相色谱性能。研究了稠环芳烃类化合物的结构与其保留值的关系,比较了烷基膦酸改性锆镁复合氧化物固定相和十八烷基键合硅胶ZorbaxODS对稠环芳烃异构体的选择性,并对可能的保留机理进行了讨论。以甲醇-水(体积比为75∶25)为流动相,在烷基膦酸改性锆镁复合氧化物固定相上分离了8种稠环芳烃类化合物。     

High-performance liquid chromatography of proteins using chemically-modified silica supports

Summary Highly efficient and fast exclusion-chromatographic separations of proteins are possible on chemically-modified, silica stationary phases. By optimizing the pH and the ionic strength of the aqueous eluent secondary interactions of the samples with surface groups can be excluded. Bonded propylamide groups proved to possess optimum properties for exclusion chromatography. With other functional groups adsorption effects cannot be excluded totally. The optimum pore size distribution for protein separation up to relative molecular masses of 500,000 daltnons is between 10nm and 50nm. With these silica-based phases the pore size distribution, the pore volume and the packing characteristics are independent of the eluent, therefore the same column can be used with aqueous as well with organic eluents. It is possible to correlate the elution volume (molecular size) of proteins with those of polystyrene standars. The recovery of the proteins and their biological activity has always been better than 90%. The potentialities of adsorption chromatography of proteins on chemically-bonded stationary plases with different functional groups are demonstrated.     

Proteomic analysis of rat plasma by two-dimensional liquid chromatography and matrix-assisted laser desorption ionization time-of-flight mass spectrometry

The proteomic analysis of plasma and serum samples represents a formidable challenge due to the presence of a few highly abundant proteins such as albumin and immunoglobulins. Detection of low abundance protein biomarkers therefore requires either the specific depletion of high abundance proteins using immunoaffinity columns and/or optimized protein fractionation methods based on charge, size or hydrophobicity. Here we describe a two-dimensional (2D) liquid chromatography separation method for the fractionation of rat plasma. In the first dimension proteins were separated by chromatofocusing according to their isoelectric point (pI). In the second dimension, proteins were further fractionated by non-porous, reversed-phase chromatography according to their hydrophobicity. The data from both separations was displayed as a 2D protein expression map of pI versus retention time (relative hydrophobicity). Both separations were carried out on the ProteomeLab PF 2D system (Beckman Coulter), an instrument platform that provides a high degree of automation and real-time monitoring of the separation process. The reproducibility of the first-dimension separation was evaluated in terms of pH gradient formation. The second-dimension separation was evaluated in terms of peak retention times on the reversed-phase column. We found in four consecutive chromatofocusing separations that the pH gradient differed by less than 0.2 pH units at any time during the elution step. Second dimension retention times of peaks from identical pI fractions differed by less than 7 s in six consecutive separations. Each 2D separation generated a total of 540 fractions which were analyzed by matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). We detected approximately 275 peptides and proteins with molecular masses ranging from 3 to 225 kDa. Most fractions were found to contain multiple low and high molecular weight proteins. Differential display of 2D protein expression maps from retinol-sufficient and -deficient rat plasma samples identified a fraction with several proteins that appeared to be down-regulated in the vitamin A-deficient animal. Quantitative proteomic analysis of complex samples such as plasma is still a difficult task. We discuss the potential of this approach for biomarker discovery and address the experimental challenges that remain.     

Packing and performance of microbore columns for adsorption and partition chromatography

Summary Microbore columns of 1 mm i.d. have turned out to be very suitable for the achievement of efficient columns.The packing procedure for stainless steel 1 mm i.d. columns from 5 to 100 cm in length was studied. Stationary phases used were: pure silica gel, octyl, octadecyl and amino bonded silicas. The main parameters (slurry composition, packing system, choice of materials) are discussed.Short columns packed with 3 or 5m particles allow high speed separations. A separation in 18 seconds is described.Very high plate numbers can be obtained with long columns. With 7–8m particles, a 1 m column can produce 50,000 plates (h=3). Columns can be joined without loss of efficiency. 270 000 theoretical plates were obtained on a 6 m adsorption column with a test mixture. In reversed-phase chromatography, bile acid sodium salts can be separated on a 1 m column. In adsorption chromatography, details are given of the separation of a polystyrene oligomer sample, as well as a light and a heavy petroleum distillate samples on a 2 m column with refractive index detection in the last-case.     

稠环芳烃在烷基膦酸改性锆镁复合氧化物固定相上的反相液相色谱保留行为

以稠环芳烃为探针 ,考察了烷基膦酸改性锆镁复合氧化物材料的反相色谱性能。研究了稠环芳烃类化合物的结构与其保留值的关系 ,比较了烷基膦酸改性锆镁复合氧化物固定相和十八烷基键合硅胶 Zorbax ODS对稠环芳烃异构体的选择性 ,并对可能的保留机理进行了讨论。以甲醇 -水 (体积比为 75∶ 2 5)为流动相 ,在烷基膦酸改性锆镁复合氧化物固定相上分离了 8种稠环芳烃类化合物     

Enantiomer separations by capillary electrochromatography using chiral stationary phases

The applicability of capillary electrochromatography (CEC) using packed capillary column to enantiomer separations was investigated. As chiral stationary phases, OD type packing materials of 5 and 3 microm particle diameters, originally designed for conventional high-performance liquid chromatography (HPLC) were employed. The chiral packing materials were packed by a pressurized method into a 100 microm I.D. fused-silica capillary. Several racemic enantiomers, such as acidic, neutral and basic drug components, were successfully resolved, typically by using acidic or basic solutions containing acetonitrile as mobile phases. The separation efficiencies for some enantiomers in the chiral CEC system using the 5 microm OD type packing were superior to those obtained in HPLC using chiral packings. The plate heights obtained for several enantiomers were 8-13 microm or the reduced plate height of 1.6-2.6, which indicates the high efficiency of this chiral CEC system.     

Packing materials suitable for rapid, analytical, low-pressure chromatography of haemoglobins on midget columns

Rapid, quantitative, chromatographic separations of mixtures of human haemoglobins have been performed on short (5-20 mm) columns of packing material. The desirable characteristics of suitable column packing materials are illustrated and discussed. Simple, inexpensive, manually operated equipment can be used for the analysis, since the specifically designed midget columns generate little back pressure (10-30 lb/in2) when eluted at constant flow rates up to 2 mL/min. Cation exchange chromatography on bonded silicas has been used for the detection of pathological haemoglobinopathies. Separations similar to the HPLC procedures are possible with the correct selection of buffer composition. It also compares favourably with the methods in common clinical use employing electrophoresis on cellulose acetate. Both ion-exchange and affinity methods for the estimation of glycated haemoglobins have been developed and are compared.     

Direct coupling of size exclusion chromatography and mass spectrometry for the characterization of complex monoclonal antibody products

The present study describes the possibilities offered by an innovative bioinert size exclusion chromatography column for size variant characterization of complex monoclonal antibody products. This size exclusion chromatography column includes a novel column hardware surface. The column was prepared from metallic hardware components that were treated to have prototype hydrophilically modified hybrid organic–inorganic silica surfaces called hybrid surface technology. This provides a significant reduction in nondesired hydrophobic and electrostatic interactions that can occur between column and analyte when performing size exclusion chromatography analysis with volatile mobile phase. Compared to a reference stainless-steel column packed with the same batch of packing material, peak tailing, band broadening, and above all recovery of high molecular weight species were distinctly improved for all types of monoclonal antibody products. Based on our observations, we found that 50 mM ammonium acetate in water was a suitable mobile phase offering good compromise in terms of liquid chromatography performance and mass spectrometry sensitivity. In addition, method repeatability (intra- and interday relative standard deviations) on elution times and high molecular weight species peak areas were found to be excellent. By using this innovative size exclusion chromatography material, the low and high molecular weight species contained in various stressed and nonstressed monoclonal antibody products were successfully characterized with mass spectrometry detection.     

含酯基包覆聚合物液相色谱柱填料

以丙烯酸甲酯或辛酯和二乙烯苯为原料，在溶液中用游离基聚合法制备了一系列含酯基包覆聚合物反相液相色谱柱填料．用傅立叶红外光谱、电子显微镜和元素分析鉴定了聚合物层，并评价了诸如硅羟基、柱压降、柱效和峰对称性等特性．该类填料适合于含氨基和羟基化合物的分离，作为应用实例，对洛伐他汀（Lovastatin）的分析展示其优良的色谱性能。     

An initial assessment of the use of gradient elution in microemulsion and micellar liquid chromatography

Novel microemulsion and micellar HPLC separations have been achieved using gradient elution and columns packed with reverse phase material. Initial attempts at gradient microemulsion liquid chromatography proved impossible on use of a microemulsion successfully used in capillary electrophoresis. Optimisation of the microemulsion composition allowed the generation of stable microemulsions to achieve separations in HPLC. The novel use of organic-solvent micellar chromatography in gradient elution mode was shown to give efficient separations. A range of efficient separations of pharmaceuticals and related impurities were obtained. Acidic, basic, and neutral solutes were resolved covering a wide range of water solubilities and polarities. Elution times were in the order of 4-15 minutes. Separations were briefly compared to those accomplished with a micellar HPLC system. It is proposed that gradient elution in both microemulsion and micellar HPLC can be regarded as a highly successful means of achieving resolution of complex mixtures and should be considered for routine analysis and further investigation.