High-speed gel permeation chromatography. A study of operational variables

Systematic studies of operational variables affecting GPC separation using μ-Styragel of nominal porosity 10⁶, 10⁵, 10⁴, and 10³ Å are reported. The dependences of (1) flow rate, (2) injection volume, and (3) concentration on elution volume (V_e), the theoretical plate number (N), and peak width at half-height were examined. The values of V_e changed with changing (1), (2), and (3). The values of N were inversely proportional to the root of flow rate. The relation between sample load and N showed that lower concentration and larger injection volume were desirable for N than the opposite. The concentration dependence for high-speed GPC was significantly higher than classical low-speed GPC. The methods of minimizing the effects produced by the individual variables and the optimum operational conditions are discussed. Recommended operational conditions are as follows: flow rate, 1 to 2 ml/min; injection volume, 0.1 ml; sample concentration, below 0.4% (or if injection volume 0.5 ml, sample concentration below 0.1%).     

DYNAMIC EVALUATION OF THE DEHYDRATION RESPONSE CURVES OF FOODS CHARACTERIZED BY A POULTICE-UP PROCESS USING A FISH-PASTE SAUSAGE. II. A NEW TANK MODEL FOR A COMPUTER SIMULATION

For a computer simulation of dehydration curves of foods, a new tank model is proposed that uses fish-paste sausage for drying that is accompanied by a poultice-up process. The model is proposed separately and is dependent on the moisture contents in Regions I (W ₀ > 100%-d.b.) and II (W ₀ < 100%- d.b.) and described by a two-term exponential expression for the two-tank model in Region I and a single-term exponential expression for a single tank model in Region II. The dehydration constants that appeared in the two equations could be evaluated quantitatively by the TPD, NMR, and SEM data obtained. By using the model equations, all the dehydration curves obtained under any drying condition were simulated, and the calculated curves agreed satisfactorily with the experimental curves derived from various drying conditions.     

The Stobbe Condensation with Substituted Succinic Esters. Part III. A Synthesis of Benzofuran and Indole Derivatives

The condensation of 1-methyl-pyrrolyl-2-carboxaldehyde with dimethyl methyl-succinate in presence of sodium hydride gave predominantly the corresponding E-half ester 1a . However, the condensation of either 1-methyl-pyrrolyl- or furan-2-carboxaldehyde with dimethyl phenylsuccinate using either the potassium t-butoxide or sodium hydride method produced a stereoisomeric mixture of E- and Z-half -esters. Cyclisation of the E-half-esters gave the corresponding benzofuran and indole derivatives 2 ; whereas their hydrolysis produced the E-dibasic acids 6 , which were converted to the corresponding anhydrides 7 .     

Cardanol‐based novolac‐type phenolic resins. I. A kinetic approach

Novolac resins having two different mole ratios of cardanol‐to‐formaldehyde (1:0.6 and 1:0.8) were prepared by using aliphatic tricarboxylic acid as catalyst at four different temperatures ranging between 100 and 130°C with an interval of 10°C. The synthesized novolacs were confirmed by infrared spectroscopic analysis with the appearance of characteristic groups of the novolac resin. The reaction between cardanol (C) and formaldehyde (F) was found to follow second‐order rate kinetics as determined by two different approaches. The over all rate constant (k) increased with the increase of C/F molar ratio. Based on the value of k, various other kinetic parameters such as activation energy (E_a), change in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG) of the reaction were also evaluated. The values of E_a and ΔH were found to be decreased with the increase of C/F molar ratio from 1:0.6 to 1:0.8. These values revealed the nature of the condensation reaction between cardanol and formaldehyde in presence of tricarboxylic acid catalysts. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:2730–2737, 2006     

A simple 1H N.m.r. Method for the quantitation of O-acetate ester and pyruvic acid acetal content of polymeric xanthan gum and related polysaccharides

Traditional methods for the quantitation of O-acetate ester and pyruvic acid acetal in xanthan gums require hydrolysis procedures followed by determination of acetic acid and pyruvic acid separately either by colorimetric, enzymic or chromatographic assays. Some of these assays are time-consuming and involve many solvent extractions, and during the course of these procedures the xanthan sample is destroyed by hydrolysis. The methyl protons of both O-acetate ester and pyruvic acid acetal can be detected by ¹H n.m.r. spectroscopy, and this paper describes a method for the quantitative determination of these groups on intact polymeric xanthan using an internal integration standard dissolved within the sample. The method is non-destructive, can be easily performed on a 60MHz spectrometer equipped with Fourier Transformation and variable temperature control, and simultaneously quantitates both O-acetate ester and pyruvic acid acetal with improved accuracy.     

Multifunctional carbochain organosilicon polymers. I. A new approach to the synthesis of high molecular weight cyclolinear polycarbosiloxane

Controlled synthesis of high molecular weight cyclolinear polycarbosiloxanes (PCCS) is considered, using the following reactions sequence: (1) anionic polymerization of vinyldimethylphenylsilane, (2) replacement of the Ph group in polyvinyldimethylphenylsilane (M _n=83.900,M _w/M _n=1.48) by a Cl group to prepare polyvinyldimethylchlorosilane (PVMCS), and (3) hydrolytic intramolecular condensation of PVMCS. The formation of carbochain polymer with predominantly six-membered carbosiloxane rings is demonstrated (M _n=81.400,M _w/M _n=1.54).     

The structure of rosmariquinone — A new antioxidant isolated fromRosmarinus officinalis L.

A new diterpene, named rosmariquinone, was isolated from the leaves ofRosmarinus officinalis L. The leaves were first extracted using methanol and, upon further purification, this extract yielded rosmariquinone. Structure elucidation of the antioxidant was done using IR, MS,¹H-NMR and¹³C-NMR.     

A study of pyridinium-type functional polymers. I. Preparation and characterization of soluble pyridinium-type functional polymers

Copolymerization of 4-vinylpyridine (4VP) with styrene (St) was performed in ethanol using 2,2′-azobisisobutyronitrile (AIBN) as an initiator, and then a random copolymer P(4VP–St) was obtained. A soluble pyridinium-type polymer containing N-benzyl-4-vinylpyridinium bromide [Q-P(4VP–St)], was prepared by quaternization of P(4VP–St) with benzyl bromide (BzBr). The structures of P(4VP–St) and its quaternized product Q-P(4VP–St) were identified by FTIR. The 4VP content in P(4VP–St) and the pyridinium group content (C_q) in Q-P(4VP–St) were determined by nonaqueous titration and argentometry, respectively. The molecular weight of p(4VP–St) was characterized by intrinsic viscosity. In addition, the charge density σ of the soluble pyridinium-type polymers was measured by colloid titration, and the mathematical relation between σ and C_q was established as follows: σ = −0.090 + 0.942 C_q. A preliminary investigation was made into the viscosity behavior and electroconductivity of the Q-P(4VP–St)/polar solvent system. © 1996 John Wiley & Sons, Inc.     

DYNAMIC EVALUATION OF THE DEHYDRATION RESPONSE CURVES OF FOODS CHARACTERIZED BY A POULTICE-UP PROCESS USING A FISH-PASTE SAUSAGE. I. DETERMINATION OF THE MECHANISMS FOR MOISTURE TRANSFER

In order to discern the mechanism for the transfer of moisture in foods as they are drying, the pore structure of food and the distribution of moisture in food matrices were studied in detail by using a fish-paste sausage that was prepared with various contents ofmo isture (W ₀). A uniform distribution ofmois ture was achieved with a poultice-up process. The void fractions (V_f ) that occurred as a result ofchanges in the pore structure of the food were evaluated from a graphical analysis of SEM photographs on a cross-sectional observation ofthe sausage. The V_f -values obtained changed drastically depending on the W₀ and were classified into two regions: I (W ₀ > 100%-d.b.), which gave V_f = 0.10 ± 0.08, and II (W ₀ < 100%-d.b.), which gave V_f = 0.24 ± 0.05 at a drying temperature of 35°C. For the analysis ofmois ture state, the temperature-programmed desorption (TPD) profiles and the correlation time ofwater protons evaluated from nuclear magnetic resonance (NMR) were effectively used. The results produced three states ofmois ture: weakly and strongly restricted water at Region I and gaseous water at Region II.     

Grafting. III. Copolymerization of methyl methacrylate and methacrylic acid

The method of graft copolymerization of methyl methacrylate on halogen-containing polymer has been utilized for grafting of methyl methacrylate–methacrylic acid monomer pair onto poly(vinyl chloride) and chlorinated rubber. Substantial grafting could be obtained by using the method reported earlier. However, the compositions of the grafted chains are found to deviate appreciably from the compositions calculated from r₁ and r₂ values reported in literature. The reactivity ratios for this pair of monomers have been therefore evaluated using azobisisobutyronitrile and n-butane thiol–dimethyl sulfoxide as initiators. The anomalies of the grafted chain compositions have been discussed and an explanation presented on preferential solvation.     

Isolation of saponin-free fraction from Ginseng (Panax ginseng C.A. Meyer) and its effects on the function of neutrophils

A method of isolation of bioactive water-soluble saponin-free subfraction (RG-ws-1-1-1) from Korean red ginseng using solvent extraction, ultrafiltration and chromatography on Diaion HP-20 resin was developed. To evaluate the potency of RG-ws-1-1-1 to effect on the heat stress (HS) response and anti-inflammatory response in neutrophils, the oxygen consumption (OC) and formation of Superoxide radicals (FSR) were assayed in suspensions of neutrophils from mice. Supplementation of RG-ws-1-1-1 to micein vivo (200 mg/kg, 14 days intraperitoneally) results in the increase OC by neutrophils assayedex vivo at 37 ℴC. OC and FSR by neutrophils were suppressed when cells obtained from the control animals were incubated at 42 ℴC. Preincubation of neutrophils with RG-ws-1-1-1 reduces HS related depression of FSR. Supplementation of RG-ws-1-1-1 to micein vivo decreases HS related suppression of OC. RG-ws-1-1-1 subfraction significantly improves an oxygen-dependent anti-microbial function of neutrophils, also studied under the HS conditions.     

Supported reagents—preparation analysis and applications. J. H. Clark,A. P. Kybett and D. J. Macquarrie. VCH,Weinheim, New York,Basle, Cambridge, 1992. pp. xi+152, price £40.50, DM108.00. ISBN 3-527-28043-X/1-56081-010-6

It is shown quantitatively that the formation of holes through the skin of membranes, prepared by the quick immersion in water of polyetherimides in solution in N-methylpyrrolidone, is governed by the solvent mobility. The surface pattern observed by videomicroscopy exhibits a characteristic distance between neighbouring holes (?5 μm) which is a linear function of D^?1_s; D_s is the solvent diffusion coefficient in the polymeric solution, measured using a pulsedfield gradient NMR technique. The dependence of this distance on the solvent concentration in water is also characterized.     

A simulation of gas transport in polymeric membranes. Application to heterogeneous aging

A simplified mechanism of polymer aging has been proposed to simulate the effect of diffusion on degradation processes. Simple observations have been made on different events simulated using a modelization of the diffusion of low mass species: (1) the bulk oxidation rate, in the case of heterogeneous oxidation, is proportional to the square root of the initiation rate (formation of radicals). (2) The relative oxidation profile (relative to the surface oxidation) as a function of aging time is not constant. (3) The initial concentration of oxygen has, in some cases, a large influence on the apparent bulk oxidation rate during all the degradation processes. (4) The same observation is made for model samples stored in air and aged in inert atmosphere. (5) When heterogeneous oxidation occurs in samples containing antioxidant additives, the concentration of antioxidant has an effect on the induction period and on the bulk oxidation rate (this is not the case for homogeneous oxidation). (6) When heterogeneous oxidation occurs, the effect of antioxidant mobility can be practically neglected when D_oxygen/D_antioxidant (D = diffusion coefficient) varies from to 100 to 1. (7) The time required to reach a pseudostationary state (corresponding to the egality of oxidation rate and oxygen diffusion rate) can be interpreted by a simple induction period (antioxidant consumption and/or hydroperoxide accumulation). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 435–444, 1997     

Interaction of metal ions with clays: I. A case study with Pb(II)

Pb(II) adsorption was studied under different conditions (pH, time, metal ion concentration, clay amount, temperature) on kaolinite, montmorillonite, and their poly(hydroxo)zirconium (ZrO–kaolinite, ZrO–montmorillonite) and tetrabutylammonium (TBA–kaolinite, TBA–montmorillonite) derivatives. All samples were calcined (ZrO-derivatives at 773 K, TBA-derivatives at 973 K) before using as adsorbents. The data were interpreted assuming first- and second-order kinetics. The rate constants including the pore diffusion rate constant are reported. The adsorption data could be fitted with Freundlich and Langmuir isotherms, and the coefficients indicated favorable adsorption of Pb(II) on the clays. Determination of the thermodynamic parameters, ΔH, ΔS, and ΔG showed the adsorption to be exothermic accompanied by decrease in entropy and Gibbs energy.     

Permeability of oxygen through polymers. I. A novel spectrophotochemical method

A novel method for the measurement of oxygen permeability through polymer membranes is described. It is based on monitoring the sensitized photo-oxygenation of a singlet oxygen acceptor in a detector layer sandwiched between a support and the polymer layer under test. The detector layer contains a sensitizer which on irradiation produces singlet excited oxygen from the ground-state oxygen available. The singlet oxygen reacts with an oxygen acceptor, the disappearance of which can be followed by spectrophotometry. In the photostationary state, changes in the acceptor absorbance are directly related to the overall flux of oxygen through the polymer membrane. It can be shown that the permeation coefficient P of oxygen is proportional to the rate of change in acceptor absorbance and to the inverse of the oxygen concentration in the surrounding atmosphere. It is given by the expression where ? is the molar extinction coefficient, ΔC is the difference in the oxygen concentration on the two sides of the polymer membrane, ΔD is the change in optical density during the time interval Δt, and l is the thickness of the polymer membrane. The method is comparatively simple and rapid and provides data for polymers that are difficult to study by more conventional methods. Oxygen permeabilities were measured for a group of water-soluble polymers.     

A Potent N-(piperidin-4-yl)-1H-pyrrole-2-carboxamide Inhibitor of Adenylyl Cyclase of G. lamblia: Biological Evaluation and Molecular Modelling Studies

In this work, we report a derivative of N-(piperidin-4-yl)-1H-pyrrole-2-carboxamide as a new inhibitor for adenylyl cyclase of Giardia lamblia which was obtained from a study using structural data of the nucleotidyl cyclase 1 (gNC1) of this parasite. For such a study, we developed a model for this specific enzyme by using homology techniques, which is the first model reported for gNC1 of G. lamblia. Our studies show that the new inhibitor has a competitive mechanism of action against this enzyme. 2-Hydroxyestradiol was used as the reference compound for comparative studies. Results in this work are important from two points of view. on the one hand, an experimentally corroborated model for gNC1 of G. lamblia obtained by molecular modelling is presented; on the other hand, the new inhibitor obtained is an undoubtedly excellent starting structure for the development of new metabolic inhibitors for G. lamblia.     

A study of pyridinium‐type functional polymers. III. Preparation and characterization of insoluble pyridinium‐type polymers

The copolymers of 4‐vinylpyridine (4VP), styrene (St) and divinylbenzene (DVB) with varied compositions, P(4VP‐St‐DVB), were synthesized by suspension polymerization using 2,2′‐azobisisobutyronitrile (AIBN) as an initiator. The insoluble (crosslinked) pyridinium‐type polymers in benzyl–pyridinium bromide form, which possess various macromolecular chain compositions, were prepared by the reaction of each P(4VP‐St‐DVB) with benzyl bromide (BzBr), respectively. By using different halohydrocarbon RX in the quaternization of P(4VP‐St‐DVB), the insoluble pyridinium‐type polymers with various pyridinium group structures were obtained. The structures of P(4VP‐St‐DVB) and its quaternized product Q‐P(4VP‐St‐DVB) were identified by FTIR. The 4VP content in each copolymer P(4VP‐St‐DVB) was measured by nonaqueous titration; and the pyridinium group content (C_q) in each Q‐P(4VP‐St‐DVB) sample was determined by means of the back titration manner in argentometry and/or the elemental analysis method, respectively. In addition, the particle structure and the surface morphology of the thus‐prepared polymer were observed using SEM. According to a series of experimental results, the preparation and characterization of insoluble pyridinium‐type polymers are analyzed and discussed. This work can prepare the ground for a study on the antibacterial activity of insoluble pyridinium‐type polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 668–675, 2000     

A new char combustion kinetic model 1. Formulation

This paper describes the development and formulation of a novel char combustion kinetic model for pulverised coal. The chemical reaction rate was considered as a function of coal intrinsic reactivity and fuel mass for a global reaction order n. The equation for char combustion reaction rate was devised by dimensional analysis using the Rayleigh method. It shows the dependency of chemical reactivity on coal parameters, such as maceral and mineral composition; char parameters, such as specify surface area and apparent density; devolatilisation time; temperature; and activation energy. The char combustion reaction rate equation developed, unlike most models, is dimensionally homogenous and is expressed by three dimensionless numbers which have physical chemical meaning. The model also exhibit similarities with transport phenomena models described by dimensionless numbers.     

Adhesion studies of tyre cords with rubber. I. Synthesis and characterization of natural rubber graft copolymers

Glycidyl methacrylate and N-vinyl pyrrolidone have been grafted onto natural rubber at 32°C using the simultaneous cobalt-60 irradiation technique. The natural rubber samples were swollen in the monomers for 24 h and thereafter subjected to gamma irradiation. The homopolymers formed in the graft copolymerization reactions and unreacted monomer were removed by solvent extraction using acetone and methanol for glycidyl methacrylate and N-vinyl pyrrolidone monomer, respectively. The influence of total dose and monomer concentration on the graft parameters was investigated. The dependence of the rate of grafting on the monomer concentration was found to be 0.93 and 0.80 for glycidyl methacrylate and N-vinyl pyrrolidone, respectively. DSC and TGA studies of the polymers were undertaken. Grafted copolymers based on glycidyl methacrylate were relatively less thermally stable compared with ungrafted natural rubber.     

Extraction of erythromycin‐A using colloidal liquid aphrons: I. Equilibrium partitioning

Colloidal liquid aphrons (CLAs) are surfactant‐stabilised solvent droplets which have recently been explored for use in pre‐dispersed solvent extraction (PDSE). In this work, the equilibrium partitioning of a microbial secondary metabolite, erythromycin, has been studied using both CLAs (formulated from 1% (w/v) Softanol 120 in decanol and 0.5% (w/v) SDS in water) and surfactant‐containing, two‐phase systems. The equilibrium partitioning of erythromycin was found to be strongly influenced by the extraction pH, and exhibited a marked change either side of the pK_a of the molecule. A modified form of the Henderson–Hasselbach equation could be used as a simple design equation to predict the equilibrium partition coefficient (m_eryt = C_org /C_aq) as a function of pH. For extraction experiments with dispersed CLAs where pH > pK_a, m_eryt values as high as 150 could be obtained and the erythromycin could be concentrated by factors of up to 100. Experiments were also carried out in surfactant‐containing, two‐phase systems to determine the effect of individual surfactants used for aphron formulation on erythromycin partitioning. For extraction at pH 10 neither the Softanol (a non‐ionic surfactant) nor SDS (an anionic surfactant) had any influence on the equilibrium erythromycin partition coefficients. For stripping at pH 7, however, it was found that recovery of erythromycin from the organic phase decreased with increasing concentration of SDS, although again the Softanol had no influence on the equilibrium. The effect of SDS was attributed to a specific electrostatic interaction between individual erythromycin and SDS molecules under stripping conditions. The m_eryt values and concentration factors achievable in the two‐phase systems were considerably less than those for the PDSE experiments. The physical properties of the two‐phase systems, ie density, viscosity, interfacial tension, etc, and the equilibrium distribution of the surfactants were also determined in relation to subsequent studies on the kinetics of erythromycin extraction. © 2000 Society of Chemical Industry