Gel Permeation Chromatography System Research Articles

“On Water” Effect for Green Click Reaction: Spontaneous Polymerization of Activated Alkyne with “Inert” Aromatic Amine in Aqueous Media

“On Water” Effect for Green Click Reaction: Spontaneous Polymerization of Activated Alkyne with “Inert” Aromatic Amine in Aqueous Media

Simultaneous Determination of Tocopherols, Phytosterols, and Squalene in Vegetable Oils by High Performance Liquid Chromatography-Tandem Mass Spectrometry

Vegetable oil is one of the principal sources of minor bioactive substances such as tocopherol, phytosterol, and squalene. In order to obtain the distribution of these substances in vegetable oil, this study developed and validated high performance liquid chromatography-tandem mass spectrometry (HPLC-MS) method for the simultaneous analysis of tocopherols (α-, β-, γ-, and δ-tocopherol), phytosterols (β-sitosterol, stigmasterol, brassicasterol, and campesterol), and squalene in vegetable oils. An automatic gel permeation chromatography (GPC) system was used to remove triglycerides from oils, avoiding the heat treatment of traditional saponification. Method validation revealed the accuracy and reliability of this method. The current approach achieved the successful separation of β- and γ-tocopherol, which solved the problem of coelution and inaccurate quantification for β- and γ-tocopherol in previous study. Additionally, this method was applied to detect tocopherols, phytosterols, and squalene in 9 categories of vegetable oils.

Advanced Gel Permeation Chromatography system with increased loading capacity: Polycyclic aromatic hydrocarbons detection in olive oil as a case of study

Gel permeation chromatography (GPC) is herein used as size exclusion clean-up technique for highly sensitive and straightforward detection of Polycyclic Aromatic Hydrocarbons (PAHs) in olive oil samples. An advanced chromatographic system has been developed to isolate a series of PAHs with cancerogenic potential, including PAH4 (benzo(a)pyrene BaP, benzo(a)anthracene BaA, benzo(b)fluoranthene BbF and chrysene Chry) reported in the European Regulation. The system avails of two glass chromatographic columns and a switching valve, that allow removal of interfering analytes in olive oil without resorting to any preliminary extraction process. A seven-fold increase of the loaded sample amount versus conventional chromatographic systems (1 g vs 0.150 g) has been pursued, as well as improved PAHs detection and quantification limits (LOD-LOQ for PAH4: 0.21–0.70 ng/g for BaA, 0.26–0.86 ng/g for Chry, 0.23–0.76 ng/g for BbF, 0.32–1.06 ng/g for BaP), in accordance with the continuous need of more and more reducing these limits in food analysis by the European Regulation. The protocol developed represents a highly innovative and efficient analytical method for organic pollutants in complex biological matrices as olive oil, that can have huge impact on technology for PAHs detection in food samples, being suitable for both industrial and small-scale laboratories.

Structural and physicochemical properties of lotus seed starch nanoparticles prepared using ultrasonic-assisted enzymatic hydrolysis.

Lotus seed starch nanoparticles were prepared by ultrasonic (ultrasonic power: 200W, 600W, 1000W; time: 5min, 15min, 25min; liquid ratio (starch: buffer solution): 1%, 3%, 5%) assisted enzymatic hydrolysis (LS-SNPs represent lotus seed starch nanoparticles prepared by enzymatic hydrolysis and U-LS-SNPs represent lotus seed starch nanoparticles prepared by high pressure homogenization-assisted enzymatic hydrolysis). The structure and physicochemical properties of U-LS-SNPs were studied by laser particle size analysis, scanning electron microscope, X-ray diffraction, Raman spectroscopy, nuclear magnetic resonance and gel permeation chromatography system. The results of scanning electron microscopy showed that the surface of U-LS-SNPs was cracked and uneven after ultrasonic-assisted enzymolysis, and there was no significant difference from LS-SNPs. The results of particle size analysis and gel permeation chromatography showed that the particle size of U-LS-SNPs (except 5% treatment group) was smaller than that of LS-SNPs. With the increase of ultrasonic power and time, the weight average molecular gradually decreased. The results of X-ray diffraction and Raman spectroscopy showed that ultrasonic waves first acted on the amorphous region of starch granules. With the increase of ultrasonic power and time, the relative crystallinity of U-LS-SNPs increased first and then decreased. The group (600W, 15min, 3%) had the highest relative crystallinity. The results of nuclear magnetic resonance studies showed that the hydrogen bond and double helix structure of starch were destroyed by ultrasound, and the double helix structure strength of U-LS-SNPs was weakened compared with LS-SNPs. In summary, U-LS-SNPs with the small-sized and the highest crystallinity can be prepared under the conditions of ultrasonic power of 600W, time of 15min and material-liquid ratio of 3%.

Development of an effective method for the separation of petroleum pitch using high pressure CO2

Mesophase pitch, as an important chemical intermediate, belongs to highly structured pitch materials that has good property for conducting heat or electricity. Pitch can be naturally derived from petroleum or coal tar. Prior to producing the mesophase pitch materials, the removal of complex low molecular weight polycyclic aromatic hydrocarbons (PAHs) from the original petroleum pitch is essential.In the study, we have developed a two-step process using high pressure CO2 for separating the useful part with desired properties from the raw petroleum pitch sample. Firstly, a stepwise supercritical CO2 (scCO2) extraction process was employed for removing the lightest molecular weight fractions. The residual and CO2-insoluble fractions were further separated by a subcritical anti-solvent (SAS) process using CO2 at 25 °C and three high pressure conditions. A modified SAS apparatus was utilized in this study. The gel-permeation chromatography (GPC) analysis system with standard calibrations was used to determine the molecular weight of various pitch samples. The GPC system was equipped with dual Ultraviolet (UV) and Refractive Index (RI) detectors. The polydispersity index (PDI) value of the raw petroleum pitch 6 (PP6) sample was 6.9, and it was reduced to 3.8 after the scCO2 extraction and under the appropriate SAS processing pressure. The corresponding weight average molecular weight (Mw) was increased from 987 to 1493 g/mol.This study provides an effective separation and product identification method that only employs commonly used GPC analyses with dual UV and RI detectors. A useful screening method has been developed for selecting the most appropriate separation parameters.

Inonotus obliquus polysaccharides protect against Alzheimer's disease by regulating Nrf2 signaling and exerting antioxidative and antiapoptotic effects.

Inonotus obliquus polysaccharide (IOPS) was initially separated and purified via precipitation from an aqueous extract with 80% alcohol, a DEAE-52 cellulose anion exchange column, and a Sephadex G-100 gel permeation chromatography system. IOPS was found to have a molecular weight of 111.9 kDa. In L-glutamic acid (L-Glu)-damaged HT22 cells, a 3-h pre-incubation with IOPS enhanced cell viability, inhibited apoptosis and caspase-3 activity, reduced the release of lactate dehydrogenase, restored the dissipated mitochondrial membrane potential, and suppressed the excess accumulation of intracellular reactive oxygen species. Compared with L-Glu-exposed cells, IOPS pre-treated cells exhibited reduced levels of Bcl-2 associated X protein (Bax) and Kelch-like ECH-associated protein 1 (Keap1) and enhanced levels of B-cell lymphoma-2 (Bcl-2), NF-E2p45-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), superoxide dismutase-1 (SOD-1), and cysteine ligase catalytic subunit. In amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice, an 8-week course of IOPS improved the pathological behaviors related to memory and cognition, reduced the deposition of β-amyloid peptides and neuronal fiber tangles induced by enhanced phosphor-Tau in the brain, and modulated the levels of anti- and pro-oxidative stress enzymes. Additionally, IOPS enhanced the expression levels of Nrf2 and its downstream proteins, including HO-1 and SOD-1, in the brains of APP/PS1 mice. The present study successfully demonstrated the protective effect of IOPS against AD and revealed the possible mechanism underlying the ability of IOPS to modulate oxidative stress, especially Nrf2 signaling, and mediate mitochondrial apoptosis.

Simplified Robust Triple Detection Methods for High Temperature GPC Analysis of Polyolefins

Very powerful triple detector high‐temperature gel permeation chromatography (HT‐GPC) systems equipped with concentration, viscosity, and multiple angle light scattering detectors can be found in many polyolefin characterization laboratories. However, the complexity and sometimes lack of robustness of some detection methods often result in failure to achieve the required precision and long‐term reliability to properly support the industrial needs. Two methods for data processing in triple detector HT‐GPC of polyolefins are here described aiming at overcoming those difficulties, specifically those related to the application of multiple angle light scattering. In the first place, we propose here a data processing method using light scattering data collected at only one angle, with application of a dissymmetry correction based on an estimate of the molecular size from the hydrodynamic volume given by the universal calibration. This method (SALSDC: single‐angle light scattering with dissymmetry correction) is simple and robust for molar mass distribution and averages. Long chain branching detection and quantification is another field plagued with lack of precision and inconsistency problems, due to the difficulty in collecting reliable radius of gyration (Rg) data using MALS, for calculation of the g‐index. A novel approach to estimate the g‐index, based on point‐by‐point calculation of the gpcBR index is here described and evaluated.

Characterization of Low-Density Polyethylene in Dibutoxymethane by High-Temperature Gel Permeation Chromatography with Triple Detection

The study presents the possibility to replace the 1,2,4-trichlorobenzene (TCB) for the analysis by gel permeation chromatography (GPC) of low-density polyethylenes (LDPE) with dibutoxymethane (DBM, butylal), a halogen free and less toxic solvent. The molecular weight distributions and the viscosity plots were measured for commercial LDPE samples solubilized in TCB, and DBM, using a GPC system with triple detection (light scattering, differential refractive index and viscometer). Similar results were obtained in both solvents for the molecular weight and long chain branching distributions of the analyzed resins, thus confirming the possibility to replace TCB with DBM for the analysis by high-temperature GPC of all types of polyolefins.

Synthesis and characterization of conjugated polymers containing phenyl and bithiophene: controlling of optical properties with molarity

Conjugated polymers containing phenyl and bithiophene units are synthesized by conventional polycondensation and crossing-coupling method of carboxylic acids with halides. The structure of both polymers formed by adding the ester group to the first polymer was confirmed by means of Fourier transform infrared (FTIR), nuclear magnetic resonance techniques, differential scanning calorimetry, and thermogravimetry and elemental analysis. The molecular weight distribution values of polymers were determined with a gel permeation chromatography (GPC) system. The optical properties of these different polymers with synthesis methods and structures were investigated for different molarities. The molar extinction coefficient values of the polymers decrease with increasing molarity. Transmittance (T) values of the polymers are increased with ester group addition and decreasing molarity. We obtained two types (direct and indirect allowed band gaps) of band gaps. The direct allowed optical band gap (E gd) values of poly(2,2′ bithiophene terephthalate) (polyBTTP) are lower than the indirect allowed optical band gap (E gid) values of poly(5-phenyl-2,2′ bithiophene) (polyPBT). The direct and indirect allowed band gap values of the polymers can be decreased with ester group addition and increasing molarity. The refractive index of the polymers can be decreased with decreasing molarity, increasing wavelength, and ester group addition.

Characterization of Polypropylene in Dibutoxymethane by High-Temperature Gel Permeation Chromatography with Triple Detection

This study presents the possibility of replacing the 1,2,4-trichlorobenzene (TCB) recommended by ASTM D 6474 for the analysis by gel permeation chromatography (GPC) of polypropylenes with dibutoxymethane (DBM, butylal), a halogen-free and less toxic solvent. The molecular weight distributions as well as the K and alpha parameters of the Mark-Houwink-Sakurada equation were measured for different types of commercial polypropylene samples solubilized in TCB and DBM, using a GPC system with triple detection (light scattering, differential refractive index, and viscometer). For the analyzed resins, covering typical applications of polypropylene, the GPC method in DBM provided results similar to those obtained in TCB.

Characterization of Polyethylene in Dibutoxymethane by High-Temperature Gel Permeation Chromatography with Triple Detection

This study presents the possibility of replacing the 1,2,4-trichlorobenzene (TCB) recommended by ASTM D 6474 for the analysis by gel permeation chromatography (GPC) of linear polyethylenes with dibutoxymethane (DBM, butylal), a halogen-free and less toxic solvent. The molecular weight distributions as well as the K and alpha parameters of the Mark-Houwink-Sakurada relationship were measured for polyethylene solutions in TCB and DBM, using a GPC system with triple detection (light scattering, differential refractive index, and viscometer). For commercial metallocene polyethylene resins typically used for film and packaging applications, the GPC method in DBM provided results comparable to those obtained in TCB.

Correction to Separation of Single-Walled Carbon Nanotubes with a Gel Permeation Chromatography System

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to Separation of Single-Walled Carbon Nanotubes with a Gel Permeation Chromatography SystemBenjamin S. Flavel*, Katherine E. Moore, Moritz Pfohl, Manfred M. Kappes, and Frank Hennrich*Cite this: ACS Nano 2014, 8, 9, 9687Publication Date (Web):August 25, 2014Publication History Received21 August 2014Published online25 August 2014Published inissue 23 September 2014https://doi.org/10.1021/nn504707kCopyright © 2014 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views2665Altmetric-Citations3LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (42 KB) Get e-AlertsSUBJECTS:Carbon nanotubes,Gel permeation chromatography,Nanoscale,Nanotechnology Get e-Alerts

Separation of Single-Walled Carbon Nanotubes with a Gel Permeation Chromatography System

A gel permeation chromatography system is used to separate aqueous sodium dodecyl sulfate suspensions of single-walled carbon nanotubes (SWCNTs). This automated procedure requires no precentrifugation, is scalable, and is found to yield monochiral SWCNT fractions of semiconducting SWCNTs with a purity of 61-95%. Unsorted and resulting monochiral fractions are characterized using optical absorption and photoluminescence spectroscopy.

Polymer Characterization by Static Laser Light Scattering

Low angle laser light scattering (LALLS) and multi-angle laser light scattering (MALLS) methods have become valuable, if not indispensable, tools for the chemist and biochemist, since they can be used to determine the absolute molecular weight and size of molecules in solution. When linked to a gel permeation chromatography system, they become even more powerful tools, providing information on molecular weight averages and their distributions (polydispersity). LALLS has essenttially been superseded by the development of on-line MALLS and size-exclusion chromatography (SEC)/MALLS systems, which have facilitated the greater application of light scattering theory in structure elucidation. For example, the determination of root mean square radii, molecular conformation and structure, branching ratios etc., are now readily achievable. This paper reviews the “theoretical backbone” of light scattering methods and the technology available for use in this particular aspect of macromolecular characterisation. Particular emphasis is placed on the use of SEC/MALLS and SEC/LALLS for the molecular weight elucidation of polysaccharides (such as carrageenans, starch, hyaluronic acid and dextrans), proteins, and the examination of branching in large macromolecular structures

EFFECTS OF EXTRUSION ON κ‐CARRAGEENAN/AGAR MIXED GEL TYPE

ABSTRACTκ‐Carrageenan and agar have a slight mutual thermodynamic incompatibility. Therefore, this study examined the effects of extrusion on the synergy ofκ‐carrageenan and agar mixed gels using mathematical mixture rules for modulus and gel time. Unlike the non‐extruded mixed gels, the extruded mixed gels did not follow the rule for a phase‐separated gel type. The changing pattern of gel time with the varying proportion of the two components of the extruded mixed gels was also different than that of the extruded mixed gels. The extrusion specific mechanical energy showed a sudden change at the proportion of the two components where a phase inversion of a phase‐separated mixed gel occurs. The polydispersity index (Mw/Mn) determined by gel permeation chromatography system suggested that the extruded agar underwent some structural changes.PRACTICAL APPLICATIONSExtrusion is one of the more versatile bioprocessing technologies, and it is effective in converting food materials in the physicochemical properties. This study attempted to modify the mixed gel properties using the extrusion process. The findings revealed that the extrusion process caused a change in the mixed gel type of κ‐carrageenan/agar, shifting from a phase‐separated gel to another gel type without phase inversion. This difference can be applied to produce a new mixed gel product.

Estimation of high-temperature properties of rubberized asphalt using chromatograph

The rutting resistance index (G*/sin δ) and chemical composition of rubber-modified binder (RMB) were evaluated using a Dynamic Share Rheometer (DSR) and a Gel-Permeation Chromatography (GPC) system, respectively. A source of base asphalt binder, PG 64-22, was used to make a total of 36 RMBs from two rubber types (ambient and cryogenic), three sizes (passing #14, #30 and #40 sieves), two contents (10% and 15% by wt.of binder) and three reaction times (15, 30 and 45 minutes). Routine PG binder tests were carried out on each binder. RMB was tested as the original binder in the DSR at high temperature. The RMB was then RTFO aged and tested as RTFO in DSR at high temperature. Chromatogram of each binder was measured using a GPC system and relative quantity (%) of large molecular size (LMS) was calculated for each binder. Correlation of LMS with G*/sin δ was evaluated by service temperature; 70, 76 and 82°C. It was found that there was a significant correlation between LMS and rutting resistance index. The size and content of crumb rubber were also significant factors affecting the rheology of binder. In addition, G*/sin δ could be estimated using LMS, crumb rubber type and content with R2 of over 0.92 by the developed prediction model. Therefore, it is possible to predict the G*/sin δ value of rubber-modified binder, with some degree of accuracy, based on LMS value, rubber content and size.

Investigation of polyaniline processibility using GPC/UV–vis analysis

In this work, we characterized the molecular weight and UV–vis spectra of polyaniline (PANI) simultaneously using a gel permeation chromatography (GPC) system equipped with a photodiode array (PDA) detector. Therefore, we constructed correlations between weight average molecular weight ( M w) values and UV–vis spectral features such as the ratio of quinoid units/benzenoid units (Q/B ratio), and the B peak positions for the continuum of discrete chromatographic fractions of PANI emeraldine base (EB). The correlation is further verified by electrochemical techniques. Using this correlation, we analyzed newly synthesized PANIs and investigated how the synthesis and post-treatment conditions impact the quality, uniformity, and processibility of the PANIs. The study also reveals that the portions with low molecular weights of PANI are more sensitive to the process conditions than those with high molecular weights.

Poly(ethylene glycol)/poly(ethyl cyanoacrylate) amphiphilic triblock copolymer nanoparticles as delivery vehicles for dexamethasone

AbstractAmphiphilic triblock copolymers, poly(ethyl cyanoacrylate)‐b‐poly(ethylene glycol)‐b‐poly(ethyl cyanoacrylate) (PECA‐b‐PEG‐b‐PECA), were synthesized via oxyanion‐initiated polymerization with sodium alcoholate‐terminated PEG as macroinitiator. PECA‐b‐PEG‐b‐PECA were characterized by gel permeation chromatography system, 1H NMR and FTIR. The results indicate that the copolymerization is well controlled with narrow molecular weight distribution. The dexamethasone (DXM)‐loaded PECA‐b‐PEG‐b‐PECA nanoparticles (NPs) were prepared by nanoprecipitation technique and then characterized by Laser Particle Size Analyzer, 1H NMR and transmission electron microscopy. The drug‐loaded PECA‐b‐PEG‐b‐PECA NPs are of spherical shape with average size of less than 100 nm. The drug‐loaded amount (DLA) and encapsulation efficiency of DLNPs were investigated by HPLC. The results show that DXM can be effectively incorporated into PECA‐b‐PEG‐b‐PECA NPs, which provides an optional delivery system for DXM and other hydrophobic drugs. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7809–7815, 2008

Facile synthesis of controlled‐structure primary amine‐based methacrylamide polymers via the reversible addition‐fragmentation chain transfer process

AbstractWe report here a novel direct method for the syntheses of primary aminoalkyl methacrylamides that requires mild reagents and no protecting group chemistry. The reversible addition‐fragmentation chain transfer polymerization (RAFT) of the aminoalkyl methacrylamide revealed to be highly efficient with 4‐cyanopentanoic acid dithiobenzoate (CTP) as chain transfer agent and 4,4′‐azobis(4‐cyanovaleric acid) (ACVA) as initiator. Cationic amino‐based homopolymers of reasonably narrow polydispersities (Mw/Mn < 1.30) and predetermined molecular weights were obtained without recourse to any protecting group chemistry. A range of block and random copolymers were also synthesized via the RAFT process. The homopolymers and copolymers were characterized by aqueous conventional and triple detection gel permeation chromatography systems. Furthermore, the primary amine‐based methacrylamide monomers and polymers revealed to be highly stable both with the primary amino group in the protonated and deprotonated form. We have also demonstrated that stabilized gold nanoparticles can be generated with the RAFT‐synthesized amine‐based polymers via a photochemical process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4984–4996, 2008

Molecular weight determination for colloidal iron by Taguchi optimized validated gel permeation chromatography

Method development of gel permeation chromatography (GPC) is a time-consuming task, since finding appropriate operating conditions has traditionally been a trial-and-error process. A novel approach in the field of GPC using experimental design called Taguchi is presented. This experimental design was used to compare the net effects of various conditions which were both qualitative and quantitative in nature. Quantitative factors included mobile phase pH, flow rate, temperature of column and detector, and injection volume. The qualitative factors were treated as noise which included enclosure of GPC system and position of waste container with respect to refractive index detector. The method was efficient as opposed to a one-factor-at-a-time approach. Taguchi optimized conditions included pH of 7.2, flow rate of 0.4 mL/min, temperature of 35 °C for column and detector, as well as injection volume of 10 μL. The optimized factors yielded acceptable results in terms of weight average molecular weight (m.w.), standard deviation and signal-to-noise ratio. Standard curves were constructed using dextran m.w. standards (12,000–270,000 Da) over the analytical range. The method was validated according to ICH guidelines. Log-linear function was used for m.w. standard curve and weight average m.w. was calculated utilizing trapezoidal approach. A correlation coefficient of >0.99 was obtained for both intra-day and inter-day standard calibration curves. Inter-day accuracy ranged from 91 to 108% and precision was <2.0%.