Separation range and separation efficiency in high-speed gel filtration on TSK-GEL SW columns

Separation ranges for gel filtration on TSK-GEL SW columns, G2000SW, G3000SW and G4000SW, were measured for globular protein, dextran and polyethylene glycol. It was possible to separate globular proteins of molecular weights from 5000 to 7,000,000, dextrans of molecular weights from 1000 to 500,000 and polyethylene glycols of molecular weights from 500 to 250,000 by using these three columns of different pore sizes. The column having the highest separation efficiency for globular proteins was also determined. The highest separation efficiency for molecular weights of less than 30,000, 30,000–500,000 and greater than 500,000 was exhibited by G2000SW, G3000SW and G4000SW, respectively.     

Application of High-Performance Exclusion Chromatography to Studying and Monitoring the Process of the Preparation of Agar

A procedure was proposed for the chromatographic analysis of mixtures of proteins and polysaccharides by high-performance exclusion chromatography on Shodex Asahipak GS-520H and GS-620H series-coupled columns with elution with water and refractometric and UV (280 nm) detection. The procedure substantially simplifies sample preparation. It was used for studying the solvent extraction of agar from the red alga Ahnfeltia tobuchiensis.     

Universal calibration in GPC: A study of polystyrene,poly-α-methylstyrene,and polypropylene

The theoretical justification for using M[_η], or a similar quantity, as a universal calibration parameter in GPC is reviewed. The equation based on this parameter is applied to transform the primary calibration curve, obtained by means of polystyrene samples, into calibration curves for poly-α-methylstyrene, polypropylene, and linear polyethylene. The Mark–Houwink equations for these polymers, as they are used in the transformation, are discussed. The resulting GPC calibration curves are compared with molecular weights and peak elution volumes of fractionated poly-α-methylstyrene and polypropylene. The same comparison is made with samples of polypropylene and polyethylene having very broad molecular weight distributions. The agreement lies within experimental error.     

Separation of peptides by multimode chromatography on a column packed with vinyl alcohol copolymer gel

Several mechanisms of peptide separation in high-performance liquid chromatography were observed to occur on the Asahipak GS-320 packed with vinyl alcohol copolymer. Neutral rather than acidic mobile phases were employed as they were found to result in higher retention of many peptides on the GS-320. For neutral peptides, the retention volume corresponded to the Rekker's hydrophobic fragmental constant, with a correlation coefficient of 0.71. Peptides with acidic residues eluted early, as an effect of ionic exclusion; those with basic residues were retained longer, owing to an ion-exchange effect. The ionic interactions were shown to involve the carboxylic group present on the gel polymer. The net result was found to be excellent separation of hydrophilic as well as hydrophobic peptides, related to differences in their isoelectric points. The combination of these complex mechanisms, together with the size-exclusion effect of the GS-320 gel for separation of proteins and other large molecules and for analysis with a mobile phase high in acetonitrile content, makes possible high-resolution isocratic analysis of peptides, which cannot be achieved on octadecylsilica or ion-exchange columns.     

Hemichrome Determination by Thermal Lensing with Polyethylene Glycols for Signal Enhancement in Aqueous Solutions

The thermal lens technique is proposed for the determination of total hemoglobin in the form of reversible hemichrome. The conditions were optimized (concentration of sodium dodecyl sulfate, 2?mM) to attain the maximum sensitivity with the use of polyethylene glycols as signal enhancers. For polyethylene glycols with molecular weights 1500–35000 Da in a concentration range of 5–15% w/w (5–25?mM), the influence on thermal lens signal enhancement was estimated. It is shown that the use of 5% w/w polyethylene glycol 2000 provides the maximum increase in the thermal lens enhancement factor (by 40%) in comparison with unmodified aqueous solutions. The detection limit of iron(II) tris(1,10-phenanthrolinate) as a model system is 60?nM. Under these conditions, the thermal lens detection limit of hemichrome is 10?nM, which shows a 15-fold enhancement compared to spectrophotometry. Modification of the medium with polyethylene glycols decreases the limit of detection of hemichrome determination by 15% in comparison with unmodified aqueous solutions due to better reproducibility for the range of concentrations from 0.02 to 0.9?µM.     

Determination of molecular weights and Mark–Houwink constants for soluble electronically conducting polymers

Intrinsic viscosities and gel permeation chromatography data were used to evaluate the Mark–Houwink constants of the soluble electronically conducting polymer, poly(3-hexylthiophene) (P3HT):K and a are 2.28 × 10^-3 cm³/g and 0.96, respectively, in tetrahydrofuran (THF) at 25°C. Mark–Houwink constants were used to calibrate gel permeation chromatography (GPC) columns for P3HT. Number-average molecular weights of P3HT determined with modified calibration curves agreed well with those determined by an absolute method, embulliometry. Molecular weights estimated using unmodified polystyrene calibration procedures were significantly larger than true values.     

Complexation of aryldiazonium ions by polyethylene glycols and their ethers

Complexation constants for interactions of $\text{p-tert}$-butylbenzenediazonium tetrafluoroborate with polyethylene glycols and their mono- and dimethyl ethers in 1,2-dichloroethane are reported. For polyethylene glycols of molecular weights 1000 and 1500 and their dimethyl ethers complexation constants with the aryldiazonium ion are 12–18% of that for the crown ether 18-crown-6.     

Rheoviscosimetric Study of PEG35000 and PEG6000 at pH 7 and pH 9: Conformational Transitions and Unperturbed Dimensions

These investigations may be of interest for researchers working on the determination of the hydrodynamic properties of the polyethylene glycols in various conditions. Various concentration regimes and the intrinsic viscosity variation were determined for polyethylene glycols of different molecular weights at different pH. The temperature-concentration phase diagrams were obtained and the information on the entanglement process of polyethylene glycol under the effect of pH was evaluated. The parameters [η]_θ, K_θ and the expansion factor α_η in the unperturbed state as a function of concentrations and temperatures were determined.     

Novel polystyryl resins for size exclusion chromatography

New size exclusion chromatography (SEC) resins based on a crosslinker having independent vinyl groups have been produced and compared with SEC resins based on divinylbenzene-55 (DVB). 1,2-Bis(p-vinylphenyl)ethane (p,p-BVPE) and its meta-isomers were suspension-copolymerized with p-methylstyrene in the presence of different porogens to give particles of about 5 μm average diameter. The porous particles were slurry-packed into stainless steel columns for SEC evaluation. Calibration curves were obtained using narrow disperse polystyrene standards with molecular weights ranging from 580 to 3,040,000. The calibration curves for the new BVPE resins covered wider useful molecular weight ranges than those for comparable divinylbenzene resins. Particle size, surface morphology and the properties of pores were studied using a Coulter Multisizer II, scanning electron microscopy, nitrogen adsorption, and mercury porosimetry. © 1994 John Wiley & Sons, Inc.     

Fractionation of polyethylene by gel permeation chromatography

The performance of the gel permeation chromatography (GPC) technique was studied with several commercial samples of linear high density polyethylene. A comparison of these data was made with those obtained from the elution column technique based on fractional dissolution. GPC gave reproducible fractionation data in the molecular weight range of 10³–10⁶. These data were obtained from two columns in series with nominal capacity of 1–10⁴ and 1–10⁶A. Polyethylene fractions of known molecular weights are required as calibration standards and for many commercial polyethylenes it is necessary to increase sensitivity at molecular weight higher than 10⁶.     

Resolution of GPC columns

A resolution index for gel-permeation chromatograph (GPC) columns is defined by the relation log (RI) = αW, where RI is the resolution index, α is the slope of the calibration curve of logarithm of molecular weight against peak position for narrow polymer fractions, and W is the width of the GPC curves for narrow fractions. This resolution index is calculated approximately for several GPC columns individually and in series combinations by using data obtained on narrow fractions of polystyrene. The index increases with number of columns and with flow rate over a limited range of flow rate, does not vary much with solvent, and does not correlate well with plate count obtained with low molecular weight molecules. It is believed that the resolution index provides an improved indication of the performance of GPC columns.     

Data Treatment in Aqueous GPC with On-Line Viscometer and Light Scattering Detectors

Abstract

Gel Permeation Chromatography (GPC) is becoming a very powerful tool for polymer characterization with the coupling of mass detectors using viscometry and light scattering techniques. The triple coupling seems to be the best way since the light scattering detector gives absolute molecular weights and viscometric detection provides intrinsic viscosity, leading to absolute molecular weights through universal calibration and information on long-chain branching. However, instrumentation becomes more sophisticated, expensive and, simultaneously, very sensitive to several parameters which are not critical in classical GPC. Moreover, an on-line computer is required for data acquisition and appropriate software for reliable interpretation of chromatograms.

Our experiments were performed with a Waters Associates room temperature instrument in which a home-made continuous viscometer, using pressure transducers, and a light scattering detector (LALLS Chromatix-CMX 100) were inserted on-line between the column set and the refractometer. Data were interpreted through personal software written on HP9836 and PC-AT computers.

We describe, here, the behavior of some polymers in aqueous solutions, mainly those that are commonly used as calibration standards (polyethylene oxides, pullulans). Experiments were run using two different sets of columns (‘Ultrahydrogel’ from Waters Associates and ‘Shodex OH-Pak’ from Showa Denko K.K.) in several aqueous solvents, pure water or water with various salts (LiNO₃, NaNO₃, LiCl, NaCl, Na₂SO₄) at different concentrations. Intrinsic viscosities were determined through viscometric detection and weight average molecular weights through the LALLS detector, leading to a plot of universal calibration curves Log([ηl.M) versus elution volumes.     

Rheological properties of aqueous solutions of polyethylene glycols with various molecular weights

The dependences of the kinematic viscosity of dilute aqueous solutions of polyethylene glycols (PEGs) with various molecular weights in the temperature range of 293.15–323.15 K were investigated. The intrinsic viscosity, the Huggins constant, and the activation energy of a viscous flow were calculated for these solutions. Proposals regarding the structure of polymer macromolecules in solution are made. The constants of the Mark-Kuhn-Hauvink equation required to estimate the polymer molecular weights were determined for PEG-water systems at various temperatures.     

Effect of molecular structure on polyethylene melt rheology. II. Shear-dependent viscosity

The investigation of the effect of molecular structural variables on the melt viscosity of polyethylene was extended to the shear dependent region by application of a reduced variables treatment following, in a formal sense, that of Bueche. Viscosity–shear rate data were obtained for a series of experimentally polymerized linear polyethylene samples having a range of molecular weights and molecular weight distributions as characterized primarily by gel permeation chromatography. These data could be superimposed on a single reduced variables flow curve using parameters which were a function only of temperature, limiting Newtonian viscosity, M?_w, and M?_w/M?_n. The same treatment was successfully applied also to branched (low-density) fraction data discussed in a previous paper, with additional correction for long-chain branching. However, different reduced variables curves were obtained for the branched and linear cases.     

Evaluation of the properties of polyethylene glycols as stationary phases in gas-liquid chromatography

This paper reports an evaluation of the retention characteristics of polyethylene glycols used as liquid phases in gas chromatography.Eight different grades of polyethylene glycol were tested (Carbowax 300, 400, 600, 1000, 1540, 4000, 6000 and 20M) and their retention volumes for various homologous series were measured (n-alkanes, l-alcohols, methyl alkyl ketones and linear chloro-, bromo- and iodoalkanes).Effects of the molecular weight, of temperature, and of the position of the hydroxyl group were examined, and the activity coefficients calculated.     

Gel permeation chromatography: On the shape of the calibration plot and molecular size separability

Data obtained from the calibration of GPC columns of different permeabilities with standard polystyrenes are reported. For single columns the logarithm molecular weight–elution volume plot is linear for approximately one and one-half decades in molecular weight. GPC separations are such that the separability of two samples of similar molecular weight improves as their mean molecular weight decreases. Because of this the analysis of high molecular weight polymers can best be accomplished on a series of columns in which each column has a high permeability limit. The elution volume for columns in series is shown to be the sum of the elution volumes of the individual columns. As higher molecular weights are eluted a pronounced tailing effect is observed.     

Recent advances in the bioanalytical methods of polyethylene glycols and PEGylated pharmaceuticals

Polyethylene glycols are synthetic polymers composed of repeating oxyethylene subunits, which have been known for non‐toxic, non‐immunogenic, non‐antigenic, good solubility in water and therefore approved for pharmaceutical applications. Recently, attachment or amalgamation of polyethylene glycols to therapeutic small molecules, peptides, proteins, or nanoparticles has become a mature technology for the sake of improving their pharmacokinetic and pharmacological profiles, also referred to as PEGylation. By comparison, there are only a few PEGylated pharmaceuticals have been registered for further clinical trials and even less was approved for marketing. High failure rate of PEGylated pharmaceuticals in pre‐clinical and clinical trials could be majorly attributed to their unclear pharmacokinetic behaviors. Therefore, the in vivo fate of the PEGylated pharmaceuticals for the various routes of administration needs to be thoroughly investigated An accurate in vivo pharmacological study thereof highly depends on the precise detection of polyethylene glycols as well as their fragments in biological matrixes. The goal of this review is to highlight the analytical methods that were developed and applied to evaluate the polyethylene glycols in pharmaceutical ingredients and excipients, which bring us closer to bridging the gap between the development of polyethylene glycol‐based drug delivery systems and their clinical application.     

Comparison of dynamically coated SE-54, SP-2250 and carbowax 20M wall-coated open tubular (WCOT) glass capillary columns,prepared after surface pretreatment with Superox™-4 or with BaCO3

A new surface pretreatment for the preparation of wall-coated open tubular (WCOT) glass capillary columns has been evaluated. This technique involves the application of a non-extractable layer of Superox?-4, a 4,000,000 MW polyethylene glycol, to the glass surface as a pretreatment and deactivation agent. Unlike other polyethylene glycols, Superox-4 is stable at high temperatures (> 300°C) in the absence of oxygen, coats smoothly onto a bare glass surface and resists droplet formation. WCOT columns (SE-54, Carbowax 20M, and SP-2250) prepared using this technique are compared to columns prepared using a modified Grob [2,3] BaCO₃ procedure. The Superox-4 pretreated columns were equal or superior in quality to the BaCO₃ pretreated columns, based on the appearance of an activity standard and the effective theoretical plates (N_eff) per meter. Chromatograms showing practical application of the WCOT columns prepared using both methods is given.     

相转移催化合成增塑剂BBP和水杨醛的研究

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Simple solution for a complex problem: proanthocyanidins, galloyl glucoses and ellagitannins fit on a single calibration curve in high performance-gel permeation chromatography

This study was undertaken to explore gel permeation chromatography (GPC) for estimating molecular weights of proanthocyanidin fractions isolated from sainfoin (Onobrychis viciifolia). The results were compared with data obtained by thiolytic degradation of the same fractions. Polystyrene, polyethylene glycol and polymethyl methacrylate standards were not suitable for estimating the molecular weights of underivatized proanthocyanidins. Therefore, a novel HPLC-GPC method was developed based on two serially connected PolarGel-L columns using DMF that contained 5% water, 1% acetic acid and 0.15 M LiBr at 0.7 ml/min and 50 °C. This yielded a single calibration curve for galloyl glucoses (trigalloyl glucose, pentagalloyl glucose), ellagitannins (pedunculagin, vescalagin, punicalagin, oenothein B, gemin A), proanthocyanidins (procyanidin B2, cinnamtannin B1), and several other polyphenols (catechin, epicatechin gallate, epicallocatechin gallate, amentoflavone). These GPC predicted molecular weights represented a considerable advance over previously reported HPLC-GPC methods for underivatized proanthocyanidins.