Use Of Gel Permeation Chromatography Research Articles

Past to Future: Application of Gel Permeation Chromatography from Petroleomics and Metallopetroleomics to New Energies Applications: A Minireview

In the field of petroleomics and metallopetroleomics, the gel permeation chromatography (GPC) technique coupled with high-resolution detection technologies has made significant contributions as an analytical and preparative tool for over five decades. This bibliographic minireview highlights the study of the supramolecular and structural behavior of heavy crude oil and its fractions, as well as their reactivity to various processes by use of GPC. The preferred mobile phase is tetrahydrofuran (THF), whereas the stationary phase is polystyrene–divinylbenzene copolymer to avoid compound retention in the column. Other techniques such as HPTLC, RPLC, and NPHPLC have been used to provide multidimensional separations complementary to GPC. The high molecular weight (HMW) fraction, due to its greater polarity, reactivity to polymerization, and resistance to hydrodemetallization processes, has been the focus of interest for years. GPC coupled with high-resolution techniques has proven to be reliable for the detection of organic and inorganic species in bio-oils, making it a valuable tool for researchers and industry professionals in the context of feedstocks changes and new energy production.

Improvements on the use of GPC to measure large-size microstructures in aged asphalt binders

ABSTRACT Gel permeation chromatography (GPC) is commonly used to study the aging and rejuvenation behaviours of asphalt binders, as the sizes of molecules and microstructures in asphalt binders change in such processes. The filtration procedure in preparing GPC specimens, however, may filter out some large-size microstructures in asphalt, making the measured molecular size distribution biased. To investigate this issue, two laboratory-aged asphalt binders and seven recovered ones were studied. Substances filtered from asphalt binders were analysed gravimetrically, followed by examinations using scanning electron microscope (SEM) and scanning transmission electron microscope (STEM). Relationships between binders’ rheological properties and the proportion of large molecular size (LMS) content based on the GPC chromatogram were investigated before and after counting the filtered substances. Results show that microstructures in the recovered asphalt binders differ from those in laboratory-aged ones in both size and morphology. While about 1% of laboratory-aged asphalt binders is obstructed by the GPC filter, 6–10% of recovered ones are blocked. Adding the filtered substances results in better correlations between the rheological properties and the proportion of LMS content. Therefore, in using GPC to analyze aged asphalt binders, it is recommended to count the filtered substances as part of LMS content.

Understanding the removal of V, Ni and S in crude oil atmospheric residue hydrodemetallization and hydrodesulfurization

This study describes the use of gel permeation chromatography inductively coupled plasma high-resolution mass spectrometry (GPC ICP HRMS) to examine and explain two important petroleum industry catalytic processes: hydrodemetallization (HDM) and hydrodesulfurization (HDS).The sulfur, nickel and vanadium species size distributions in atmospheric residue fractions were studied to track their evolution during both catalytic processes and examine their mechanisms, especially those mechanisms linked to changes in temperature and initial deactivation via coke laydown. Chromatogram shapes as well as peak areas were used to study the V, Ni and S aggregate types and concentrations in the feedstock as well as in the product after varying the operating temperature and residence time at a constant temperature. For the V and Ni compounds, the low and medium molecular weight (LMW and MMW, respectively) aggregates are easily hydrotreated under all conditions, while the high molecular weight (HMW) compounds are more refractory. For the S compounds, a different reactivity pattern was observed whereby the LMW, MMW and HMW aggregates were more similar in their reactivity, showing that the catalyst is less selective towards a certain aggregate size for the S compounds compared to the V or Ni compounds.

Study of Permanent Shear Thinning of VM Polymer Solutions

The ultrashear viscometer (USV) has been adapted and employed to investigate the permanent shear thinning of polystyrene solutions in a series of phthalate ester base fluids. The permanent shear stability index based on viscosities measured at 106 s−1, PSSI(106), has been found to be a convenient way to express the magnitude of permanent shear thinning. When comparing permanent shear thinning at various shear rates in the USV, it is very important to take account of the different times of shear that are present at different shear rates. The PSSI(106) value divided by the total time of shear is then a useful way of quantifying and comparing permanent shear thinning rates. Tests using polystyrene in different viscosity base fluids have shown that this rate of permanent shear thinning depends on shear stress and not shear rate and varies linearly with polymer concentration. The rate of permanent shear thinning also varies exponentially with shear stress, suggestive of a stress-promoted polymer breakdown process. By using a small volume of test fluid in the USV and solvent extraction after a test, it has proved possible to obtain molecular weight distributions of polymer after shear using gel permeation chromatography (GPC). This indicates that the polymer breakdown process is different at low and high polymer concentrations, with molecule fragmentation at low polymer concentration but mid-chain scission at high concentration. A key feature of the USV is that, unlike other methods currently used to measure permanent shear thinning behaviour of engine oils, it subjects the test fluid to well-defined, controllable high shear conditions. Coupled with the use of GPC, this makes it possible for the first time to relate quantitatively the permanent shear thinning of engine oils to shear conditions and to polymer degradation response.

Characterization of Crude Oil Interfacial Material Isolated by the Wet Silica Method. Part 1: Gel Permeation Chromatography Inductively Coupled Plasma High-Resolution Mass Spectrometry Analysis

The interfacial material (IM) from four different crude oils with different capabilities to form stable water-in-oil (w/o) emulsion was extracted with the wet silica method and analyzed by different techniques. In the first of a series of papers, we report the use of gel permeation chromatography inductively coupled plasma high-resolution mass spectrometry (GPC ICP HR MS) to analyze the size distributions of sulfur-, vanadium-, and nickel-containing compounds present in the IM. The analysis of replicate samples demonstrated the reproducibility of the wet silica extraction method, and successive extractions of the same crude oil concentrated larger and more insoluble IM aggregates containing S, V, and Ni. The analysis of the IM from different crude oils revealed that there is a similar, selective adsorption of high-molecular-weight compounds containing Ni and V at the w/o interface. Conversely, the sulfur profiles for all of these IMs were unique, and given their widely varying ability to stabilize emulsio...

A highly automated method for simultaneous determination of sterols, erythrodiol and uvaol in olive oils

In this work, we presented a highly automated method for the simultaneous analysis of sterols, erythrodiol and uvaol in olive oils with the use of gel permeation chromatography (GPC), an automatic solvent evaporator and LC-MS.

Gel permeation chromatography as a multifunctional processor for nanocrystal purification and on-column ligand exchange chemistry.

This article illustrates the use of gel permeation chromatography (GPC, organic-phase size exclusion chromatography) to separate nanocrystals from weakly-bound small molecules, including solvent, on the basis of size. A variety of colloidal inorganic nanocrystals of different size, shape, composition, and surface termination are shown to yield purified samples with greatly reduced impurity concentrations. Additionally, the method is shown to be useful in achieving a change of solvent without requiring precipitation of the nanocrystals. By taking advantage of the different rates at which small molecules and nanoparticles travel through the column, we show that it is furthermore possible to use the GPC column as a multi-functional flow reactor that can accomplish in sequence the steps of initial purification, ligand exchange with controlled reactant concentration and interaction time, and subsequent cleanup without requiring a change of phase. This example of process intensification via GPC is shown to yield nearly complete displacement of the initial surface ligand population upon reaction with small molecule and macromolecular reactants to form ligand-exchanged nanocrystal products.

Following the enzymatic digestion of chondroitin sulfate by a simple GPC analysis

We describe the use of gel permeation chromatography (GPC) setup with four size exclusion columns for analysis of enzymatically digested glycosaminoglycans (GAGs). This setup provides information about the molecular weight (Mw) and concentration of all species (low and high Mw) present in the digests in a single measurement. The data about the fraction with high Mw (often omitted in the analysis of GAG digests) provide direct evidence about the mechanisms of action of the enzymes. We proved the feasibility of this methodology by applying it to chondroitin sulfate (CS) substrates with different molecular weight and sulfation pattern and using different enzymes (hyaluronidase and chondroitinase). NMR analysis of the obtained digests fractionated by ultrafiltration confirmed the results obtained by GPC setup and reveal further details about the degradation mechanisms: (i) both enzymes preferentially attack 4-sulfated chondroitin and (ii) additionally to the well documented endolytic activity of hyaluronidase we also observed a low lyase activity for this enzyme reflected in the detected minor exolytic breakage. Finally, we demonstrate that CS with medium molecular weight (12–60kDa) which is sulfated mainly at 6-position can be obtained in good yields by enzymatic digestion and following ultrafiltration.

Single-stage synthesis of phosphazene-containing epoxy oligomers

A single-stage synthesis of phosphazene-containing epoxy oligomers via the direct interaction of hexachlorocyclotriphosphazene, diphenylolpropane and epichlorohydrin has been proposed. The resulting products are composed of a common epoxy-diane oligomer and an epoxyphosphazene component, with the content of the latter being up to 45 wt %. Oligomers with epoxy numbers up to 22 were characterized with the use of gel permeation chromatography, chromatography-mass spectrometry, laser mass spectrometry, 31P NMR spectroscopy, and 1H NMR spectroscopy.

Use of gel permeation chromatography for clean-up in the analysis of coccidiostats in eggs by liquid chromatography–tandem mass spectrometry

An analytical method for determination and confirmation of nine coccidiostatics in eggs is reported. Ethyl acetate is used as extraction solvent, with satisfactory results, and simple automated clean-up is based on gel-permeation chromatography (GPC) . The target compounds are then analysed by liquid chromatography-electrospray ionization-tandem mass spectrometry. The method was validated in-house in accordance with Commission Decision 2002/657/EC. Trueness and precision were determined at four concentrations, and the mean errors obtained were <10 %, with relative standard deviations ranging from 3 to 18 %. For three non-authorized coccidiostatics (clopidol, ethopabate, and ronizadole), decision limit and detection capability were in the ranges 0.12-0.16 and 0.18-0.23 μg kg(-1), respectively. The results obtained prove the suitability of this new analytical method for routine monitoring of these substances in eggs.

Degradable Poly(2-hydroxyethyl methacrylate)-co-polycaprolactone Hydrogels for Tissue Engineering Scaffolds

Biodegradable poly(2-hydroxyethyl methacrylate)(pHEMA) hydrogels for engineered tissue constructs were developed by the use of atom transfer radical polymerization (ATRP), a degradable cross-linker, and a macroinitiator. Hydrogels are appropriate materials for tissue engineering scaffolds because of their tissue-like mechanical compliance and mass transfer properties. However, many hydrogels that have seen wide application in medicine are not biodegradable or cannot be easily cleared from the body. pHEMA was selected for the scaffold material because of its reasonable mechanical strength, elasticity, and long history of successful use in medicine as well as because it can be easily fabricated into numerous configurations. pHEMA was studied at various molecular weights between 2 and 50 kDa. The molecular weight range suitable for renal clearance was an important factor in the experimental design. The fabricated hydrogels contain oligomeric blocks of polycaprolactone (PCL), a hydrolytically and enzymatically degradable polymer, as a cross-linking agent. In addition, a degradable macroinitiator that also contained oligomeric PCL was used to initiate the ATRP. The chain length, cross-link density, and polymerization solvent were found to affect the mechanical properties of the pHEMA hydrogels. Degradation of the pHEMA hydrogels was characterized by the use of 0.007 M NaOH, lipase solutions, and phosphate-buffered saline. The mass loss, swelling ratio, and tensile modulus were evaluated. Degradation products after sodium hydroxide treatment were measured by the use of gel permeation chromatography (GPC) to verify the polymer lengths and polydispersity. Erosion was observed in only the sodium hydroxide and lipase solutions. However, the swelling ratio and tensile modulus indicate bulk degradation in all PCL-containing samples. Degradable hydrogels in enzymatic solutions showed 30% mass loss in 16 weeks. Initial cell toxicity studies indicate no adverse cellular response to the hydrogels or their degradation products. These hydrogels have appropriate mechanical properties and a tunable degradation rate, and they are composed of materials that are currently in FDA-approved devices. Therefore, the degradable pHEMA developed in this study has considerable potential as a scaffold for tissue engineering applications, in cardiac and other applications.

Monoacrylated cyclodextrin via “click” reaction and copolymerization with N-isopropylacrylamide: guest controlled solution properties

Mono-(1 H-1, 2, 3-triazol-4-yl) (methyl) 2-methylacryl-β-cyclodextrin (CD) 3 is synthesized by microwave assisted `click´ reaction of propargyl (meth) acrylate and mono-(6-azido-6-deoxy)-β-CD using Cu (I) catalysis. Free radical copolymerizations of monomer 3 with N-isopropylacrylamide 5 (NIPAAM) of different portions are carried out. The properties of polymers are characterized by use of gel permeation chromatography (GPC), dynamic light scattering (DLS) and turbidity measurements. The Lower Critical Solution Temperatures (LCSTs) of the copolymers with different portions of NIPAAM and influence of guest molecules addition by adamantly carboxylate and adamantly methyl methacrylate are evaluated.

Improvement of the purification of Saint Louis encephalitis virus NS2B-NS3 recombinant protease expressed in Escherichia coli

The NS2B-NS3 serine protease of Saint Louis Encephalitis virus (SLEV), a potential target for antiviral drug design, has been over-expressed as a recombinant His-tag protein in Escherichia coli for future structural determination. The production process resulted in a soluble protease with co-purification of DnaK, a bacterial molecular chaperone already described in E. coli protein expression. Two approaches were tested to remove this specific contaminant. The fusion protein bound to the purification resin was washed with MgATP plus soluble denatured E. coli proteins before elution, but this method proved to be poorly efficient due to a substantial loss of the targeted recombinant protease. After the immobilized metal affinity chromatography step, the use of gel permeation chromatography with addition of arginine in the mobile phase led to effective separation of the native viral protease from the DnaK aggregates. By this way, SLEV ΔNS2B-NS3pro protease was purified as a functional protein with a purity greater than 90% suitable for crystallization attempts.

Interdiffusion of polydisperse Mw distributions subsequent to proton irradiation of PS melts

Under exposure to ionizing radiation the molecular weights of polymeric matter changes via formation of crosslinks and scissions of chains. As a result the molecular weight ( M w) distribution of a polymer depends on the applied ion fluence and differs from the initial one, which in our case is of the Schulz–Zimm type. Statistical theories can be used to estimate the M w distribution. We study M w distributions in proton irradiated polystyrene (PS) thin films by diffusion measurements. As chains of different degrees of polymerization diffuse unequally fast diffusion depth profiles contain information about the involved M w distribution. Both irradiation and analysis with nuclear reaction analysis (NRA) were made at the Freiburg van de Graaff accelerator. As comparison gel permeation chromatography (GPC) measurements were conducted. However, the use of GPC is limited by the minimal amount of material needed and also does not work for very short chains in our case. Here we concentrate on the M w distributions, the measurements and the fitting procedure will be presented elsewhere.

Determination of banned 10 azo-dyes in hot chili products by gel permeation chromatography–liquid chromatography–electrospray ionization-tandem mass spectrometry

An accurate method based on the use of gel permeation chromatography (GPC)–liquid chromatography–tandem mass spectrometry interfaced with electrospray ionization (GPC–LC–ESI-MS/MS) was devised for the simultaneous determination of Sudan (I–IV), Sudan Orange G, Sudan Red B, Sudan Red G, Sudan Red 7B, Butter Yellow and Para Red in hot chili products. A GPC clean-up procedure was developed for simultaneous quantification of 10 dyes in hot chili and hot chili products avoiding some interference and permitting multiple injections without damaging the column. A HPLC was performed on an Inertsil C18 column using a multistep gradient elution with 0.1% formic acid and methanol as the mobile phase. Mass spectral acquisition was done in positive ion mode. Linearity of around three orders in the magnitude of concentration was generally obtained with the correlation coefficients ( r 2) of 0.9984–0.9997. Limit of detection (LOD) and limit of quantification (LOQ) for the investigated dyes were in the ranges of 0.1–1.8 and 0.4–5.0 μg/kg depending on matrices, respectively. The recoveries of the 10 synthetic dyes in five matrices ranged from 81.7 to 92.9%. The intra- and inter-day precision (RSDs) was between 2.9–7.8 and 3.9–8.1%, respectively. This method has been applied successfully for the determination of the studied 10 banned dyes in hot chili products.

Fundamental kinetic aspects of living radical polymerization and the use of gel permeation chromatography to shed light on them

AbstractThe control achievable by living radical polymerization (LRP) is based on a kinetic balance of the activation–deactivation reversible reactions, which are specific to LRP, with conventional elementary reactions such as initiation, propagation, and termination. This work describes, as plainly as possible, how chains grow and how their polydispersity evolves as they experience activation–deactivation cycles and how these processes can be quantitatively analyzed by gel permeation chromatography. A comprehensive probability theory on the polydispersity indices of LRP polymers is presented. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4743–4755, 2004

In vitro hydrolysis of poly( l-lactide) crystalline residues as extended-chain crystallites : III. Effects of pH and enzyme

The effects of pH and an enzyme on the hydrolysis of poly( l-lactide) [i.e. poly( l-lactic acid) (PLLA)] crystalline residues or extended-chain crystallites containing a negligibly small amount of chains in an amorphous state were investigated in aqueous solutions at pH range from −0.9 to 12.8 and in Tris–HCl buffered solution with or without proteinase K by the use of gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). GPC results showed that the hydrolysis of the crystalline residues proceeded from their surface composed of very short chains with a free end along the chain direction, irrespective of pH, but that from their lateral surface could not be traced. GPC and DSC results indicated that the hydrolysis of the crystalline residues was accelerated with the pH deviation from 7, reflecting that the hydronium and hydroxide ions have catalytic effects on the hydrolysis of the crystalline residues. The dependence of hydrolysis rates estimated by GPC on the concentration of hydronium or hydroxide ions revealed that the catalytic effect of hydroxide ions on the hydrolysis is much higher than that of hydronium ions. The significant T m decrease at high and low pH means that there is a decrease in thickness of the crystalline residues by the hydrolysis. On the other hand, GPC and DSC results also showed that proteinase K has no catalytic effect on the hydrolysis of the crystalline residues, confirming the reported finding that the hydrolysis of very short chains with a free end is not accelerated by the presence of proteinase K.

Dynamic Modeling of Living Anionic Solution Polymerization of Styrene/Butadiene/Divinylbenzene in a Continuous Stirred Tank Reactor Train

Herein is reported a novel dynamic kinetic reactor model for the living anionic solution polymerization of styrene/butadiene/divinylbenzene in a continuous stirred tank reactor train. The model accounts for association of the n-butyllithium, the anionic initiator, and the formation of tetrafunctional long-chain branches via propagation with pendant carbon–carbon double bonds on divinylbenzene incorporated in the copolymer chains. The model predicts individual molecular weight distributions for polymer chains from zero to nine tetrafunctional branch points and by using Zimm–Stockmayer long-chain branching equations, it is possible to predict, gel permeation chromatography (GPC) (DRI (differential refractive index)/VISCOTEK) detector cell contents properties (polymer weight fraction, intrinsic viscosity, and number-average molecular weight vs. retention volume). This permits effective use of GPC for kinetic parameter estimation. The GPC measurements on the copolymer in the effluent of a single continuous stirred tank reactor are used to illustrate the effectiveness of parameter estimation.

Linear polymers with sulfur in the main chain. II. Synthesis of polyesters by interfacial polycondensation of bis(4,4′‐hydroxyphenyl)sulfide with several aliphatic acid dichlorides and their properties

AbstractThe synthesis and properties of sulfur‐containing polyesters derived from bis(4,4′‐hydroxyphenyl)sulfide (TDP) and various acid dichlorides (AC) have been studied to evaluate the effect of the incorporation of sulfur in the main chains of polyesters. Polyesters derived from TDP and AC (with methylene numbers of 2–10) were synthesized by interfacial polycondensation in a 1,1,2,2‐tetrachloroethane /water mixture using tetra‐n‐butyl ammonium bromide as a phase transfer catalyst. Through the use of gel permeation chromatography, it was determined that the polyesters thus obtained had high molecular weights. The thermal properties of the polyesters including the TDP moiety were evaluated by thermogravimetry/differential thermal analysis and by differential scanning calorimetry. The analyses indicated that the polyesters including the TDP moiety were crystalline polymers with relatively high heat resistance. These polyesters were found to show an odd–even effect with the glass transition temperature and the melting point based on the methylene numbers. The tensile strength and storage modulus decreased with the methylene numbers. It was further found that the polyesters evidenced excellent barrier properties towards oxygen gas having an odd–even effect. In particular, it was shown that the polyesters with methylene numbers of 3, 4, 6, and 8 of methylene units have lower oxygen permeability than poly(ethylene terephthalate) (PET).©2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1865–1872, 2004

Use of Gel Permeation Chromatography to Characterize the Changes in Natural Organic Matter through Oxidative Treatments

Use of Gel Permeation Chromatography to Characterize the Changes in Natural Organic Matter through Oxidative Treatments