Gel Permeable Chromatography Research Articles

Enhancement of large ring cyclodextrin production using pretreated starch by glycogen debranching enzyme from Corynebacterium glutamicum

Synthesis of large-ring cyclodextrins (LR-CDs) in any significant amount has been challenging. This study enhanced the LR-CDs production by Thermus filiformis amylomaltase (TfAM) enzyme by starch pretreatment using glycogen debranching enzyme from Corynebacterium glutamicum (CgGDE). CgGDE pretreated tapioca starch gave LR-CD conversion of 31.2 ± 2.2%, compared with LR-CDs produced from non-treated tapioca starch (16.0 ± 2.4%). CgGDE pretreatment enhanced amylose content by approximately 30%. Notably, a shorter incubation time of 1 h is sufficient for CgGDE starch pretreatment to produce high LR-CD yield, compared with 6 h required for the commercial isoamylase. High-Performance Anion Exchange Chromatography coupled with Pulsed Amperometric Detection (HPAEC-PAD) and Gel Permeable Chromatography (GPC) revealed that CgGDE is more efficient than the commercial isoamylase in debranching tapioca starch and gave lower molecular weight products. In addition, lower amount of by-products (linear oligosaccharides) were detected in cyclization reaction when using CgGDE-pretreated starch. In conclusion, CgGDE is a highly effective enzyme to promote LR-CD synthesis from starch with a shorter incubation time than the commercial isoamylase.

Wood adhesives from waste-free recycling depolymerisation of flexible polyurethane foams

Flexible polyurethane foams (FPUF) are common plastic materials used in industry or consumer goods (heat and sound insulation, washing sponges, car seats). FPUF wastes are frequently taken to landfills and incineration, which causes environmental problems. The current method of physical recycling for rebound foams seems to be efficient, however, with limited usage in the structure of mattresses or construction insulations. Disadvantages of the current chemical recycling methods of FPUF consist of the slow reaction process, high energy consumption, and production of secondary waste by-products. This article deals with the special technique of the controlled depolymerisation of the studied FPUF. FPUF was depolymerised in an ambience of non-reactive liquid at a temperature of 130 °C, only giving liquid products. The depolymerisation process and the final product was characterised by titration methods, Fourier Transform-Infrared Spectroscopy (FT-IR), Gas Chromatography/Mass Spectrometry (GC/MS), and Gel Permeable Chromatography (GPC). The recycled polyol (product of depolymerisation) was tested in model polyurethane adhesive formulations and evaluated for shear tensile strength on spruce wood test pieces.

An in-situ RAFT polymerization technique for the preparation of poly(N-vinyl imidazole) modified Cloisite nanoclay to develop nanocomposite PEM

In this work, we have carried out in-situ RAFT polymerization of poly (N-vinylimidazole) (PNVI) in the inter-galleries of Cloisite nanoclay. The polymerization was carried out in two sets of different solvent-initiator combinations: N, N-Dimethyl formamide (DMF) - azobisisobutyronitrile (AIBN) and water/ethanol mixture - 4,4′-azobis (4-cyanovaleric acid) (ACV), with varying monomer ratios in order to synthesize PNVI of three different molecular weights. The three PNVI modified Cloisite clays (named as CP-1, CP-2 and CP-3 corresponding to low, medium and high molecular weight PNVI, respectively) were characterized thoroughly. X-ray diffraction and field emission scanning electron microscope analysis revealed the extent of delamination of the clay layers after the polymerization. The CP-3 clay, containing high molecular weight PNVI, was completely exfoliated, whereas the CP-1 clay with low molecular weight PNVI formed intercalated structure and CP-2 showed partial exfoliation. Gel permeable chromatography was used to determine the molecular weights of PNVI and the thermogravimetric analysis revealed the quantities of PNVI polymerized in the clays galleries. Further, the PNVI modified clays were used to prepare nanocomposites with poly (4,4′-diphenylether-5,5′-benzimidazole) (OPBI). All the nanocomposite membranes exhibited higher storage modulus (up to ~170% increase at 400 °C), tensile properties, acid doping levels (~30 mol/OPBI repeat unit), proton conductivity (0.19 S/cm at 180 °C) and controlled acid leaching. The CP-3 clay, with exfoliated clay layers and freely dispersed PNVI chains in the OPBI matrix, resulted in effective interfacial interactions with the OPBI chains and consequently demonstrated higher property enhancement of the nanocomposite membranes than when the other two clays were incorporated.

Molecular Weight of Liquid Natural Rubber (LNR) Product from the Chemical Depolymerization Process of High Molecular Weight Narutal Rubber Latex

The molecular weight of natural rubber varies greatly, from only a few hundred thousand to more than one million. Liquid natural rubber (LNR) products generally use natural rubber in the form of latex with a relatively low molecular weight, which ranges from a molecular weight of 600,000 g / mol. This study aims to determine the molecular weight of LNR products made from the chemical depolymerization process of natural rubber latex with a molecular weight of more than one million. The natural rubber used latex with 20% Dry Rubber Content (KKK). The natural rubber depolymerization process used NaNO2 and H2O2 degrading agents with a CoCl2 catalyst at 80 °C. H2O2 levels were kept constant at 1 parts per hundred rubber (phr), and NaNO2 levels vary at 0; 2; 3; and 4 phr. After the reactor temperature reaches 80°C, the CoCl2 catalyst was added, which level varied at 0; 1; 3; and 5 phr. The reaction time was varied, which 7, 8, and 9 hours. The results of LNR product was purified to form a semi-gel, and molecular weight was analyzed using gel permeable chromatography (GPC). The results showed that the lowest molecular weight of the resulting LNR product was 108,335 g / mol from the initial molecular weight of 1,384,638 g / mol.

Synthesis, characterisation and application of quaternised pectin as flocculant in wastewater treatment

Citrus pectin is modified by quaternisation and named with quaternised pectin (QP) to enhance the flocculating efficiency of pectin. QP was characterised by Fourier-transform infrared spectroscopy (FTIR), gel permeable chromatography (GPC) and zeta potential. The results of QP characterisation revealed that functional groups are hydroxyl, carboxyl and amino group, the molecular weight is 380,188 Da, and zeta potential is in range of 24.68 to 33.95 mV. Jar test was used to evaluate the coagulation-flocculation properties of QP with the prior addition of ferric chloride as a coagulant. Three factors (pH, [FeCl3] (mg/L) and [QP] (mg/L)) were found essential for the removal of turbidity, suspended solids (SS), chemical oxygen demand (COD) and colour of anaerobic-aerobic treated palm oil mill effluent (AATPOME). Response surface methodology (RSM) was used for optimisation, and the results of central composite design (CCD) for the optimum conditions were pH 5, the dosage of FeCl3 at 927 mg/L, and the dosage of QP at 6.4 mg/L.

"Receptor free" inner filter effect based universal sensors for nitroexplosive picric acid using two polyfluorene derivatives in the solution and solid states.

Two "receptor-free" blue fluorescent conjugated polymers (CPs) of fluorene namely 9,9-bis(6-bromohexyl)-2-phenyl-9H-fluorene (PF1) and 9,9-bis(6-bromohexyl)-9H-fluorene (PF2) were synthesized using Suzuki cross coupling polymerization and oxidative coupling polymerization methods in high yields and well characterized by gel permeable chromatography, NMR, UV-vis, fluorescence and time-resolved photoluminescence (TRPL) spectroscopy. Both CPs explicitly recognized nitroexplosive picric acid (PA) and displayed a fluorescence quenching response in solution and on a solid support via the Inner Filter Effect (IFE) mechanism. Both CPs were highly selective and sensitive towards PA with high quenching constant values (Ksv) of 5.1 × 104 M-1 and 5.0 × 104 M-1 and remarkably low limit of detection (LOD) values of 110 nM and 219 nM. Contact mode detection of PA was also accomplished using economical and transportable fluorescent paper test strip devices for on-site sensing, which detect a minimum of 22.9 femtograms of PA. The IFE mechanism for PA sensing (or for other analytes) is an interesting concept that can detect PA by just having blue fluorescence. Therefore, careful experiments for IFE correction were performed herein for PA detection to observe ∼77% suppression efficiency due to the IFE. These studies provide fundamentally important information on the IFE based mechanism for the detection of various analytes.

High Yields of Bio Oils from Hydrothermal Processing of Thin Black Liquor without the Use of Catalysts or Capping Agents.

Black liquor (BL) from the kraft pulping process has been treated at elevated temperatures (380 °C) in a batch reactor to give high yields of a bio oil comprising monomeric phenolic compounds that were soluble in organic solvents and mineral oil and a water fraction with inorganic salts. The metal content in the product was <20 ppm after a simple extraction step. A correlation between concentration, temperature, and reaction time with respect to yield of desired product was found. At optimal reaction conditions (treating BL with 16 wt % dry substance at 380 °C for 20 min), the yield of extractable organics was around 80% of the original lignin with less than 7% of char. The product was analyzed by gel permeable chromatography, mass spectroscopy, nuclear magnetic resonance, elemental analysis, and inductively coupled plasma. It was found that a large fraction composed of mainly cresols, xylenols, and mesitols. This process provides a pathway to convert a major waste stream from a pulp mill into a refinery feed for fuel or chemical production, whereas at the same time the inorganic chemicals are recovered and can be returned back to the pulp mill.

Purification and characterization of a harsh conditions-resistant protease from a new strain of Staphylococcus saprophyticus

A major road block to the industrial usage of known proteases is their limited stability under harsh conditions. Hence, there is always a need for newer enzymes with novel properties that can further satisfy all industrial demands. This study described a benthic marine bacterium, Staphylococcus saprophyticus that secretes an alkaliphilic and broad-temperature active protease (10–80 °C). The protease was successfully purified 42.66-fold using 70–80% ammonium sulfate precipitation and gel-permeable column chromatography. It had a relative molecular mass of 28 kDa on sodium dodecyl sulphate-polyacrylamide gel electrophoresis and retained high activity and significant stability at 60–80 °C, over a wide range of pH (3.0–12.0), inhibitors and metal ions. Furthermore, the enzyme was stable in surfactants (such as sodium dodecyl sulfate), oxidizing agents (such as H2O2), bleaching agents (such as zeolite) and hydrophobic solvents (such as benzene, hexanes and hexadecane). These properties support the enzyme's potential as a vigorous biocatalyst for industrial applications.

Iron(III) porphyrin catalyzed ionic liquid mediated polymerization of methylmethacrylate

A novel application of iron(III)porphyrin catalyst, 5,10,15,20 − tetrakis − (2′,6′‐dichlorophenyl)porphyrinatoiron(III) chloride is reported for the reaction of methyl methacrylate with hydrogen peroxide in imidazolium ionic liquids at ambient temperature. The reaction furnished polymethyl methacrylate in 75–94% yields. The yield of the polymer was optimized upon changing the reaction media, ratio of catalyst, oxidant and substrate, reaction time and quenchers. The polymethyl methacrylate was secured as highly stereoregular with predominantly syndiotactic sequences as analyzed with the aid of NMR (1H and 13C) and infrared spectroscopy. Besides, the number‐average molecular weights (Mn) were attained in the range of 15,000 to 55,000 with narrow polydispersity (~1.1–1.9) as calculated using gel permeable chromatography (GPC).

Fluorescence "Turn-On" Indicator Displacement Assay-Based Sensing of Nitroexplosive 2,4,6-Trinitrophenol in Aqueous Media via a Polyelectrolyte and Dye Complex.

A water-soluble nonfluorescent cationic conjugated polyelectrolyte poly(1,1′-((1,4-phenylenebis(oxy))bis(propane-3,1-diyl))bis(pyridin-1-ium)bromide) (PPPy) was specifically synthesized via an economical method of oxidative coupling polymerization in high yields. PPPy selectively recognized nitroexplosive picric acid (PA) by fluorescence “turn-on” in the presence of closely related nitroexplosive compounds, namely, 2,4,6-trinitrotoluene, 2,4-dinitrophenol, and 4-nitrophenol via fluorescence indicator displacement assay (IDA) technique in water at pH 7.0. The polymer PPPy was characterized by NMR spectroscopy, gel permeable chromatography, UV–vis spectroscopy. The polymer PPPy forms an electrostatic complex with uranine dye. This ensemble scheme was utilized to detect PA with a limit of detection value of 295 nM (solution state) and 0.22 ppm (vapor state) through IDA, a phenomenon that is very different from the widely reported Förster resonance energy transfer, photoinduced electron transfer, ground-state charge transfer and inner filter effect based probes used for nitroexplosive PA detection.

Dodecyl methacrylate and vinyl acetate copolymers as viscosity modifier and pour point depressant for lubricating oil

The article presents application of homo polymer of dodecyl methacrylate (DDMA) and its copolymers with vinyl acetate (VA) as multifunctional additives for lubricant formulation. Homo polymer of DDMA and five copolymers of DDMA with VA at different molar ratios were synthesized by free radical polymerization method using azobisisobutyronitrile (AIBN) as initiator. The characterization of the polymers was carried out through FTIR, NMR and GPC (gel permeable chromatography) analysis. The performance of all the polymers as viscosity index improver (VII) or viscosity modifier and pour point depressant (PPD) additive in two different base oils (mineral) were evaluated. The mechanism of action of the polymers as pour point depressant was studied by photo micrographic analysis. Rheological study of the formulated lubricant was also carried out and reported. The thermal stability of the polymers was determined by thermogravimetric analysis (TGA). It was found that thermal stability, VI and molecular weights of copolymers are higher than the homopolymer which showed better PPD property.

Effects of high energy radiation and thermo-chemical environments on polyetherimide composites: futuristic approach to nuclear waste storage

This research highlights the effect of radiation, chemical and thermal environments on mechanical and thermal properties of polyetherimide (PEI) composites. The tests are conducted on specimens made from PEI and PEI reinforced with modified Carbon Nano Fibre (CNF). The specimens are subjected to gamma radiation doses of 5 MGy, which is equivalent to the cumulative dose of radiation from spent nuclear fuel until the end of complete radioactivity. The exposed samples are further subjected to highly corrosive and thermal environments. Studies under transmission electron microscopy reveal that there is a uniform dispersion of modified CNF in PEI. Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA) indicate that there are no significant changes in thermal properties of PEI and PEI composite when exposed to aggressive environments. It is observed that there is a marginal loss in the tensile strength of polymeric samples when exposed to gamma radiation and thermal environments. PEI samples when subjected to alkaline corrosive environments show significant loss in the tensile strength. There is a significant decrease in the molecular weight of PEI under alkaline corrosive environments as seen from Gel Permeable Chromatography (GPC).

Primitive structure and its morphology for describing highly branched structure of low-density polyethylene

Although low-density polyethylene (LDPE) has been commercially available for decades, a whole picture of its morphology related to micro-structure has not been yet clarified. Here, several characterization techniques, i.e., 13C-NMR, triple-detector gel permeable chromatography (3D-GPC) and rheology, are integrated to depict its detailed structure. The results yield a new proposed concept of primitive core structure existence prior to an addition of long-chain branch (LCB), the so-called “Primitive Core” (PCore). Morphology of the PCore can be estimated from the correlation plot of the related-LCB parameters obtained by 13C-NMR and 3D-GPC, i.e., LCBcor-NMR and gpcBR, respectively. It is not only the detailed morphology of the core that is revealed, but also the morphology of LCB growth is proposed. The correlation plot of the LCBcor-NMR and the LCB index (LCBirheo calculated from rheological information) shows two discrete LCB-growth regimes: the LCBs grow onto (I) the PCore (or, branch on PCore, BoP) and (II) on the exiting branches (or, branch on branch, BoB). Furthermore, from those parameters, the number and the average length of LCB can be estimated.

Quantification of Oxidative Aging of Polymer-Modified Asphalt Mixes Made with Warm Mix Technologies

AbstractThis research investigates the oxidative aging levels of polymer-modified asphalt (PMA) mixes using gel permeable chromatography (GPC), which can help to simplify the quantification of asphalt aging. Warm-mix asphalt (WMA) technologies, namely, Aspha-min and Sasobit, were especially adapted to the PMA mixes for the purpose of the aging reduction. A short-term oven aging (STOA) procedure was used under 135 and 154°C for 2 and 4 h, respectively, to simulate the asphalt binders aged during the field operations (i.e., production, hauling, and paving construction). The aging levels were analyzed based on large molecular size (LMS) of the binders extracted from the mixes. A rolling thin-film oven (RTFO) method was also utilized using PMA binders containing those WMA additives under 135 and 163°C for 85 minutes for comparison purposes. The results showed that (1) aging time and temperature were important parameters to influence the aging; (2) the STOA procedure had a higher aging level than the RTFO meth...

Functionalization of terminal carbon atoms of hydroxyl terminated polybutadiene by polyazido nitrogen rich molecules

We report a novel synthetic approach for the attachment of the polyazido nitrogen rich molecule on to the hydroxyl terminated polybutadiene (HTPB) backbone. The terminal carbon atoms of the HTPB are functionalized by attaching cyanuric chloride (CYC) covalently on the HTPB backbone. Further reaction of this modified HTPB with sodium azide yields polyazido nitrogen rich HTPB. The unique physico-chemical properties and the microstructure of the HTPB do not get affected upon modification. IR, gel permeable chromatography (GPC) and absorption spectroscopy studies prove that the polyazido nitrogen rich molecules are covalently attached at the terminal carbon atoms of the HTPB. The π electron delocalization owing to long butadiene chain, strong electron withdrawing effect of the triazine molecules are the major driving forces for the covalent attachment of the triazine at the terminal carbon atoms of the HTPB. The disruption of the intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB chains and the presence of hydrogen bonding between the N atoms of the triazine ring with OH group of the HTPB are observed. Theoretical study also reveals the existence of the hydrogen bonding between the OH and N. Theoretical calculation shows that the detonation performance of the polyazido nitrogen rich HTPB are very promising.

Mechanical Properties of Polylactic Acid and Natural Rubber Blends Using Vetiver Grass Fiber as Filler

Polylactic acid (PLA) and natural rubber (NR) were melt blended with vetiver grass fiber using an internal mixer. Heat treatment at the temperature of 180°C was done to obtain heat treated vetiver grass fiber. Glycidyl methacrylate grafted natural rubber (NR-g-GMA) was used as a compatibilizer of PLA/vetiver/NR composites. The injection molding and compression molding were used to prepare the specimens. Molecular weight determination of PLA before and after processing was done by Gel Permeable Chromatography (GPC).Comparisons between the mechanical properties of the composites prepared from injection molding and compression molding were made.

Cell proliferative effect of polyxyloses extracted from the rhizomes of wild turmeric, Curcuma aromatica

Hot water-soluble crude polysaccharides were extracted from the rhizomes of wild turmeric, Curcuma aromatica Salisb. (Zingiberaceae), using dry grinding, boiling water extraction, and then ethanol precipitation. The crude polysaccharide extract was then fractionated by DEAE-cellulose ion exchange column chromatography, and subsequently further purified by Superdex G-200 gel filtration column chromatography, giving two relatively abundant polysaccharide fractions, called P11 and P21, and a much less common fraction P22 obtained in insufficient amounts for further analysis. The two main polysaccharide fractions were evaluated for monosaccharide composition by acid hydrolysis and high performance liquid chromatography (HPLC), whilst the molecular weight and functional groups were determined by gel permeable chromatography (GPC) and FT-IR, respectively. Fractions P11 and P21 were found to be polyxyloses with molecular weight-averages of 469,171 and 157,665 Da, respectively. P11 (100 μg/mL) could significantly induce human gingival fibroblast cells proliferation by 30%, while P21 (100 μg/mL) could significantly inhibit gingival fibroblast cells proliferation by 92%. The in vitro human primary gingival fibroblast cell proliferation in cell culture at a concentration of 100 μg/mL.

Effect of copolymer ratio on hydrolytic degradation of poly(lactide-co-glycolide) from drug eluting coronary stents

The in vitro hydrolytic degradation behavior of poly( d, l-lactide-co-glycolide) (PLGA) has been systematically investigated from the drug eluting coronary stents with respect to different copolymer compositions. The drug–polymer coated stents were incubated in phosphate buffer saline (pH 7.4) at 37 °C and 120 rpm up to 12 months to facilitate hydrolytic degradation. Gel permeable chromatography, differential scanning calorimetry and scanning electron microscopy were employed to characterize their degradation profiles. The study supports the bulk degradation behavior for PLGA from coated stents. Molecular weight of polymer decreased immediately after immersion in PBS but mass loss was not observed during first few days. The rate of hydrolytic degradation was influenced by copolymer ratio, i.e., degradation of 50:50 PLGA was fastest followed by 65:35 PLGA and 75:25 PLGA. The drug release from PLGA coated stent followed biphasic pattern which was governed by surface dissolution and diffusion of drug rather than polymer degradation.

Isolation and Characterization of a Novel Thermophilic-Organic Solvent Stable Lipase From Acinetobacter baylyi

The benzene tolerant Acinetobacter baylyi isolated from marine sludge in Angsila, Thailand could constitutively secrete lipolytic enzymes. The enzyme was successfully purified 21.89-fold to homogeneity by ammonium sulfate precipitation and gel-permeable column chromatography with a relative molecular mass as 30 kDa. The enzyme expressed maximum activity at 60 degrees C and pH 8.0 with p-nitrophenyl palmitate as a substrate and found to be stable in pH and temperature ranging from 6.0-9.0 to 60-80 degrees C, respectively. A study on solvent stability revealed that the enzyme was highly resisted to many organic solvents especially benzene and isoamyl alcohol, but 40% inhibited by decane, hexane, acetonitrile, and short-chain alcohols. Lipase activity was completely inhibited in the presence of Fe(2+), Mn(2+), EDTA, SDS, and Triton X-100 while it was suffered detrimentally by Tween 80. The activity was enhanced by phenylmethylsulfonyl fluoride (PMSF), Na(+), and Mg(2+) and no significant effect was found in the presence of Ca(2+) and Li(+). Half of an activity was retained by Ba(2+), Ag(+), Hg(+), Ni(2+), Zn(2+), and DTT. The enzyme could hydrolyze a wide range of p-nitrophenyl esters, but preferentially medium length acyl chains (C(8)-C(12)). Among natural oils and fats, the enzyme 11-folds favorably catalyzed the hydrolysis of rice bran oil, corn oil, sesame oil, and coconut oil in comparison to palm oil. Moreover, the transesterification activity of palm oil to fatty acid methyl esters (FAMEs) revealed 31.64 +/- 1.58% after 48 h. The characteristics of novel A. baylyi lipase, as high temperature stability, organic solvent tolerance, and transesterification capacity from palm oil to FAMEs, indicate that it could be a vigorous biocatalyzer in the prospective fields as bioenergy industry or even in organic synthesis and pharmaceutical industry.

Synthesis and Characterization of Low Volatile Content Polyurethane Dispersion from Depolymerised Polyethylene Terphthalate

In the past few decades, governments and international agencies have been placing more emphasis on the improvement of production technique, working conditions and reduction of the toxic emission to the atmosphere. In this context aqueous polyurethane dispersion was synthesized from depolymerised polyethylene terphthalate (PET) waste. 1,4-Butanediol was used in PET depolymerisation. Polyurethane dispersion films were characterized using differential scanning calorimeter, Fourier transform infrared spectroscopy, gel permeable chromatography, etc. Incorporation of PET waste in polyurethane dispersion was an added advantage in waste management and produced better quality polyurethane dispersion.