Analysis of chitosan by gel permeation chromatography

The effect of γ-radiation on the average molecular weight and the molecular-weight distribution of chitosan has been studied. The analysis of samples by gel permeation chromatography/size exclusion chromatography (GPC/SEC) has shown that the amount of high-molecular-weight fractions decreases and the amount of fractions containing low-molecular-weight chitosans (<50 kDa) increases with an increase in the radiation dose. The radiation-chemical yield of degradation is 11.0 particle/100 eV.     

Sample preparation improvement in polycyclic aromatic hydrocarbons determination in olive oils by gel permeation chromatography and liquid chromatography with fluorescence detection

The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid-liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile-water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15 degrees C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluorene to 500 nm for indeno(1,2,3-cd)pyrene. Recovery for all the compounds studied varied from 75 to 111%, and limit of detection values from 0.05 ng/g for benzo(k)fluoranthene to 0.48 ng/g for indeno(1,2,3-cd)pyrene, corresponding to 0.09 ng/g benzo(a)pyrene. Results were compared with those obtained by liquid-liquid extraction followed by a cleanup on silica and a direct GPC treatment of oil samples diluted in dichloromethane, 2 other methodologies that are appropriate for quantifying PAHs in olive oils. However, the proposed method improves the determination limits, reduces the time of analysis, and provides a highly stable baseline for sample chromatograms.     

Analysis of proanthocyanidins by high-performance gel permeation chromatography

A high-performance gel permeation chromatography method was developed for the analysis of proanthocyanidins. The isocratic method consisted of two porous polystyrene-divinylbenzene columns (300 x 7.5 mm each, 5 microm, 100 and 500 A individual pore size) and a mobile phase consisting of N,N-dimethylformamide containing 1% (v/v) acetic acid, 5% (v/v) water and 0.15 M lithium chloride. The flow-rate was maintained at 1 ml/min, with a column temperature of 60 degrees C and with detection at 280 nm. The method was used to analyze proanthocyanidin fractions of increasing molecular mass and from different plant tissues. The average molecular mass of proanthocyanidin fractions as determined by acid catalysis in the presence of phloroglucinol, related well with their gel permeation chromatography column retention, yet significant differences in the retention properties between individual plant tissue isolates existed. Proanthocyanidin compositional differences between isolates may explain these differences. A second-order calibration curve was generated from fractionated grape seed proanthocyanidins and this curve was used to analyze grape seed proanthocyanidins isolated from grapes harvested at extremes of maturity.     

Rapid analysis of membrane glycopeptides by gel permeation high-performance liquid chromatography

A rapid procedure for the analysis of glycopeptides has been developed using gel permeation high-performance liquid chromatography (HPLC). Glycopeptides derived by exhaustive pronase digestion of glycoproteins from radiolabeled human tumor and normal cell lines were chromatographed on DuPont GF-250 and GF-450 gel permeation columns in buffers containing non-ionic detergents. Effective separations of glycopeptides ranging in molecular mass from less than 600 daltons to more than 20,000 daltons, equivalent to the separation range of Sephadex G50 chromatography, were achieved in 7 min. The separations were dependent upon the use of an isocratic mobile phase, that contained a low-ionic-strength Tris buffer and Nonidet P-40 or Triton X-100. The mobilities of protein standards indicated the occurrence of a biphasic elution system, which favored the separation of species with molecular masses below 20,000 daltons. Glycopeptides isolated by this method could be applied directly to lectin or ion-exchange columns or could be digested with neuraminidase, endo H or other enzymes without further treatment. Removal of sialic acid from the glycopeptides caused a dramatic increase in retention time. Using this method, glycopeptides could be isolated rapidly and in high yield. The ease, speed and reproducibility of the separations and compatibility of the solvent systems with affinity or ion-exchange chromatography techniques make this gel permeation HPLC method an ideal initial step in the purification of glycopeptides.     

Polymer studies by gel permeation chromatography

Samples of polystyrene and poly(methyl methacrylate) have been prepared by bulk polymerization under conditions previously investigated in the literature. The molecular weight distributions were determined for early-conversion samples by gel permeation chromatography, and the experimental distribution curves were compared with calculated curves based on kinetic data. The agreement between the experimental and calculated curves was such as to indicate the utility of gel permeation chromatography in the investigation of polymer reaction kinetics and mechanisms.     

Discrimination of spilled oils by high speed gel permeation chromatography with ultraviolet spectrometric detector

Summary High speed gel permeation chromatography (GPC) with ultraviolet spectrometric detector was applied to the discrimination of oils spilled into sewer pipes and into the sea. HSG-15 (polystyrene gel, Shimadzu) and tetrahydrofuran were used as a stationary phase and an eluent, respectively. The chromatogram was obtained by measuring the absurbancy of the eluate with a spectrophotometer adjusted to the wavelength of 254 nm and others. The discrimination capability was considerably enhanced by comparing the profiles of the chromatograms at several detection wavelengths. The change of profiles with weathering of the oil was very small.

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Erkennung von Ölverschmutzungen durch Hochgeschwindigkeits-Gelpermeations-Chromatographie mit U.V.-spektralphotometrischem Detektor

Zusammenfassung HPGPC mit U.V.-spektralphotometrischer Detektion wurde zur Erkennung von Ölverschmutzungen auf See und in Kanalisationen eingesetzt. HSG-15 (Polystyrolgel, Shimadzu) diente als stationäre Phase, Tetrahydrofuran als Eluans. Das Chromatogramm wurde aus spektralphotometrischer Messung des Eluats bei 254 nm u. a. erhalten. Durch Messung bei verschiedenen Wellenlängen und Vergleich der entsprechenden chromatographischen Profile wurden die Unterscheidungsmöglichkeiten wesentlich verbessert. Die Profilveränderung durch Witterungseinflüsse auf das Öl war gering.

     

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.     

Separation of dextrans by gel permeation chromatography

The role of the intrinsic viscosity [η] as separation parameter in gel permeation chromatography (GPC) was studied for dextrans (from Leuconostoc mesenteroids B512) dissolved in water with deactivated silicagel (Porasil) as the column-filling material. For that purpose specific viscosities of dextran fractions eluted by GPC were measured as a function of the elution volume v. Provided that the elution volumes are corrected for zonal spreading, they are related to the intrinsic viscosities in an unambiguous way, probably reflecting a unique relationship between degree of branching and molecular weights. This was further investigated by developing an iteration method to prepare two calibration curves γ(v) and g(v), respectively, relating ln[\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}] and InM (M is the molecular weight) to v. It required that the weight-average molecular weight M _w, the number-average molecular weight M _n, and the average intrinsic viscosity [\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}] for a number of dextran samples (broad distributions) be previously known. The calibration curves found lead to consistent values of the above-mentioned averages. Moreover, they allow-establishment of the [\documentclass{article}\pagestyle{empty}\begin{document}$\left[ {\bar \eta } \right]$\end {document}]-M relationship over the range 5000 < M < 500,000.     

Analysis of the negative peaks in gel permeation chromatography

The negative peak usually encountered in gel permeation chromatography has been resolved into three distinct peaks through selection of appropriate columns. The three peaks are associated with water, nitrogen, and oxygen. Separation of these simple molecules was found to follow the fundamental theory of gel permeation chromatography, that is, separation according to straight-chain length.     

Instrumental broadening in gel permeation chromatography

Summary Instrumental broadening corrections to gel permeation chromatograms have been demonstrated to be of minimal concern when using the newly available high efficiency packing materials. This was demonstrated using -Styragel as packing material on polymer standards with both narrow and broad molecular weight distributions.     

Role of diffusion in gel permeation chromatography

A theory is developed that describes the diffusion of solute into the gel particles during a gel permeation chromatographic experiment. The particles are treated as homogeneous spheres of radius a, into which diffusion takes place with diffusion coefficient D_s. The concentration in the mobile phase at any level at any time is supposed to be uniform throughout the cross-section of the column. It is shown that in the usual columns the effect of diffusion in the mobile phase is unimportant. A determinative quantity in the process is the parameter a²/D_st, where t is the time. For large values of a²/D_st an explicit expression for concentration versus time in the mobile phase at the end of the column is derived [eq. (26) and Fig. 1]. It shows a relatively long tail at large efflux volumes V, where the concentration varies at V^?3/2. For arbitrary values of a²/D_st the first three moments of the concentration versus time curve are calculated [eqs. (33)–(37)]. Pronounced skewness of the curve is found unless a²/D_st is small.     

Flow-rate dependence of gel permeation chromatography

Analysis of polystyrene standards by gel permeation chromatography over a wide range of flow rates revealed two sources of error in volume measurement. These errors arise from solvent evaporation in the siphon chamber and from solvent continuing to flow into the siphon during discharge. Appropriate corrections are discussed, and a vapor feedback loop to eliminate the solvent evaporation error is described. The flow rate dependence of the GPC calibration curve, expressed in the corrected elution volumes, appears different from that reported in the literature. The corrected flow rate dependence of peak elution volumes is in agreement with the expectation of diffusion and exclusion theories.     

凝胶渗透色谱净化-高效液相色谱法测定油脂食品中的邻苯二甲酸酯类增塑剂

建立了油脂食品(方便面、油炸糕点、沙琪玛、食用油等)中5种主要邻苯二甲酸酯类增塑剂的凝胶渗透色谱（GPC）净化-高效液相色谱(HPLC)分析方法。食品样品用石油醚超声提取,经GPC净化后,采用反相HPLC进行分析。所用的分离柱为Labtech C18(250 mm×4.6 mm, 5 μm),以乙腈和水为流动相,梯度洗脱。方法的相关系数皆在0.997以上,目标物的检出限(信噪比为3计)为3.25～13.4 μg/L。在50 mg/L添加水平时,目标物的加标回收率为70.4%～113.6%,相对标准偏差为0.3%～5.8%(n=3)。该方法简便、快捷、实用,可用于油脂食品中邻苯二甲酸酯类增塑剂的分析测定。     

Characterization of polyurethane network chains by gel permeation chromatography

Starting materials, prepolymers, chain-extended oligomers, and polyurethane network chains were characterized by gel permeation chromatography in order to make clear the change of molecular distribution in the formation of polyurethane networks. The polyurethane networks were prepared from poly(oxypropylene)glycol (PPG 1000, M _n = 997, M _w/M _n = 1.04), 2,4-tolylene diisocyanate, and 1,4-butanediol by the prepolymer method. Polyurethane networks were degraded by the amine degradation method, by which allophanate groups as crosslinking sites were decomposed selectively. The prepolymer had four species. The polydispersity index of the prepolymer (M _w/M _n) was about 2, that is, the most probable distribution. The product of the chain-extending reaction of prepolymer with BD had five species. The molecular-weight distribution of this product was narrower than that of the prepolymer. The polydispersity of the interstitial chains between crosslinking sites was also narrower than that of the chain-extended product. The polyaddition mechanism in the formation of PPG–TDI–BD polyurethane networks was discussed.     

Clean-up of a pesticide-lanolin mixture by gel permeation chromatography

In this study, the efficiency of a clean-up method by gel permeation chromatography (GPC) for the separation of pesticides from lanolin is analyzed. The pesticides analyzed belong to two different families, organophosphorous and synthetic pyrethroids. Lanolin, a standard mixture of the pesticides, and a lanolin-pesticides mixture are injected in a GPC column. The recoveries and elution times from the GPC column of lanolin (by a gravimetric method) and pesticides (by gas chromatography-electron capture detector) are determined. From this column, a good separation of the lanolin-pesticides mixture is observed.