Styrene Divinylbenzene Research Articles

Comparison of liquid chromatographic methods with direct detection for the analysis of gentamicin

Several liquid chromatographic (LC) methods have been described for the analysis of gentamicin. LC combined with pulsed electrochemical detection (LC-PED) or evaporative light scattering detection (LC-ELSD) was found to be the most suitable technique. A first method, previously developed by Adams et al. used a poly(styrene-divinyl benzene) stationary phase with a mobile phase containing sodium sulphate, sodium-1-octanesulphonate, tetrahydrofuran, 0.2 M phosphate buffer (pH 3) and water. However, the polymer columns show low efficiency, which also leads to poor sensitivity. So, recently the use of newer conventional C18 columns was further investigated. Improved separation was obtained using a Supelcosil LC-18-DB column with an adapted mobile phase. Another method derived from a company method was checked by using a Gemini column and a mobile phase containing an aqueous solution of trifluoroacetic acid (TFA) and pentafluoropropionic acid (PFPA) adjusted to pH 2.6 with sodium hydroxide (NaOH). This method was transferred to ELSD by replacing the non-volatile NaOH with volatile ammonium hydroxide solution. A volatile method, which was originally developed for ELSD using an aqueous solution of 50 mM TFA and gradient elution with methanol, was also combined with PED. In this study, these methods were compared with regard to their selectivity, sensitivity and ease of use.

Bioreactors Based on Monolith‐Supported Ionic Liquid Phase for Enzyme Catalysis in Supercritical Carbon Dioxide

AbstractBioreactors with covalently supported ionic liquid phases (SILP) were prepared as polymeric monoliths based on styrene–divinylbenzene or 2‐hydroxyethyl methacrylate–ethylene dimethacrylate, and with imidazolium units loadings ranging from 54.7 to 39.8 % wt IL per gram of polymer. The SILPs were able to absorb Candida antarctica lipase B (CALB), leading to highly efficient and robust heterogeneous biocatalysts. The bioreactors were prepared as macroporous monolithic mini‐flow systems and tested for the continuous flow synthesis of citronellyl propionate in supercritical carbon dioxide (scCO2) by transesterification. The catalytic activity of these mini‐flow‐bioreactors remained practically unchanged for seven operational cycles of 5 h each in different supercritical conditions. The best results were obtained when the most hydrophobic monolith, M‐SILP‐8‐CALB, was assayed at 80 °C and 10 MPa, reaching a total turnover number (TON) of 35.8×104 mol product/mol enzyme. The results substantially exceeded those obtained for packed‐bed reactors with supported silica‐CALB‐Si‐4 catalyst under the same experimental conditions.

Purification of citrus limonoids and their differential inhibitory effects on human cytochrome P450 enzymes

AbstractRecent studies demonstrated that citrus limonoids and flavonoids possess numerous health promoting properties. In the present study, glucosides of limonoids and flavonoids were purified from citrus molasses and limonoid aglycones from citrus seeds. Glucosides were separated on styrene (divinylbenzene), Q‐sepharose resins with increasing concentration of sodium chloride. A pH‐dependent cold precipitation was carried out for the isolation of naringin in large quantity. Major aglycones such as limonin and nomilin were isolated from seeds by direct crystallization and minor limonoids were purified by vacuum liquid chromatography. The structures of the isolated compounds were confirmed by NMR spectra. Individual limonoids were tested for O‐dealkylase and hydroxylase activities of human cytochrome P450 (CYP) isoenzymes such as CYP1A2, CYP1B1, CYP3A4 and CYP19, using ethoxyresorufin, methoxyresorufin and dibenzylfluorescein as substrates. Partial to high inhibition of CYPs was observed in dose‐dependent assays. Significant (P < 0.001) reductions in enzyme activities were observed with purified compounds above 2 µmol. Kinetic analyses indicated that limonin glucoside inhibited CYP19 competitively (IC50, 7.1 µ mol L−1), whereas Nomilinic acid glucoside inhibited it noncompetitively (IC50, 9.4 µ mol−1). Nomilinic acid glucoside was the most potent limonoid, with an overall IC50 of < 10 µ mol, for all the enzymes tested. The differential inhibition of CYPs can be ascribed to structural variations of the limonoid nucleus. Limonoid inhibition of key CYPs involved in carcinogenesis supports growing evidence that citrus limonoids act as anticancer agents. Copyright © 2007 Society of Chemical Industry

Fabrication of a poly(styrene–octadecene–divinylbenzene) monolithic column and its comparison with a poly(styrene–divinylbenzene) monolithic column for the separation of proteins

In this paper, a poly(styrene-octadecene-divinylbenzene) (PS-OD-DVB) monolithic column was prepared in one step by introducing a C18 carbon chain as monomer. N,N-Dimethylformamide and decanol served as porogens to make a homogeneous polymerization mixture in a fused silica capillary (320 microm inner diameter). Its physical and chromatographic properties were compared with those of poly(styrene-divinylbenzene) (PS-DVB) monolithic column, which was also fabricated by in-situ polymerization in a fused silica capillary with the same inner diameter. Six standard proteins were used to evaluate the columns and their potential application for the separation of human hemoglobin was also discussed. It was shown that the PS-OD-DVB and PS-DVB monoliths appeared to have similar efficiency for rapid separation of six proteins within 3.5 min. The PS-OD-DVB monolith was found to have higher loading capacity and higher resolution for the separation of alpha and beta chains of hemoglobin because of the introduction of C18 carbon chains, and shows great potential for the separation of bio-macromolecules.

Kinetics of sorption of polyaromatic hydrocarbons onto granular activated carbon and Macronet hyper-cross-linked polymers (MN200)

Polymeric supports are presented as an alternative to granular activated carbon (GAC) for organic contaminant removal from groundwater using permeable reactive barriers (PRB). The search for suitable polymeric sorbents for hydrocarbon extraction from aqueous streams has prompted the synthesis of new resins incorporating new functionalities or modifying the polymer network properties that solve many of the existing problems. Between them, the new type of polymeric sorbents Macronet Hypersol containing a styrene–divinylbenzene macroporous hyperreticulated network has been evaluated. Because of their potential sorptive properties, tests were conducted to determine the feasibility of using them as a low-cost reactive material for groundwater applications. The present work describes the sorption of six polycyclic hydrocarbons (PAHs) from aqueous solution onto both Macronet polymeric sorbent MN200 and granular activated carbon. Batch experiments were performed to determine loading rates of a family of PAHs (naphthalene, fluorene, anthracene, acenaphthene, pyrene, and fluoranthene), from a simple two-rings PAH (naphthalene) up to a four-ring PAH (pyrene). The behavior of a non-functionalized Macronet support (MN200) was compared with the behavior of a recognized material, granular activated carbon (GAC). Analyses of the respective rate data with three theoretical models (pseudo-first- and pseudo-second-order reaction models and the Elovich model) were used to describe the PAH sorption kinetics. Sorption rate constants were determined by graphical analysis of the proposed models. The study showed that sorption systems followed a pseudo-first-order reaction model, although the pseudo-second-order reaction model provides an acceptable description of the sorption process. Graphical analysis showed that the sorption process with activated carbon is a more complex process than the one observed for hyper-cross-linked polymers (MN200). A simulation of the barrier thickness needed to treat a PAH-polluted plume showed that 0.1–1 m of sorption media is enough even for high water fluxes such as 0.1–2 m 3/m 2/day for both sorbents.

Deformation of styrene—divinylbenzene copolymers and hypercrosslinked polystyrenes during solvent adsorption and desorption

An automated procedure was developed for monitoring fast changes in the size of spherical samples of polymers during their contact with a solvent or drying. The kinetics of bulk deformation in these processes was studied for a series of cross-linked polymers, viz., gel-type and porous styrene—divinylbenzene copolymers and poly(divinylbenzenes), and hypercrosslinked polystyrenes. Gel, macroporous, and hypercrosslinked polystyrenes are substantially different in the rate, mechanism, and degree of swelling, which is associated with the principal differences in their physical structures. An unusual effect of a sharp decrease followed by a temporary increase in the volume of porous polystyrene and poly(divinylbenzene) materials were observed during desorption (evaporation) of organic solvents. Water desorption is accompanied by an excessive bulk compression of porous granules giving rise to negative deformations, which gradually relax to the state equilibrium for the dry polymer. The results of dynamic desorption porometry (for water desorption) are indicative of a bimodal size distribution of micropores in hypercrosslinked polystyrene.

Adsorption of Maillard reaction products from aqueous solutions and sugar syrups using adsorbent resin

Adsorption of the Maillard reaction products (MRP) onto a styrene–divinylbenzene copolymer based adsorbent resin (AR) was studied. The effects of various parameters such as temperature, AR concentration, contact time, and sugar concentration were investigated. Among various isotherms, the equilibrium data fitted best to the GAB isotherm which indicated a multilayer adsorption of MRP onto AR. The temperature strongly influenced the adsorption process. The thermodynamic parameters E a, Δ H, Δ G and Δ S indicated that the adsorption process was exothermic and spontaneous process which is favored at lower temperatures, and also occurred by both physical adsorption and weak chemical interactions. Adsorption of MRP onto AR obeyed the pseudo-second-order kinetic model and occurred by both surface sorption and intraparticle diffusion. The pore diffusion controlled the adsorption process at low sugar concentrations while the film diffusion governed the adsorption mechanism at high sugar concentrations. It was concluded that the adsorption process should be performed at sugar concentrations lower than 50% to overcome the film resistance.

Fe(II/III) adsorption onto styrene/divinyl benzene based polymers

AbstractThe effectiveness of two styrene/divinyl benzene (SDB) compounds was studied for the removal of Fe(II) and Fe(III) from aqueous solutions. The first one was styrene/divinyl benzene sulfonate (SDB‐S), which was commercially supplied and used as an ion‐exchange resin. The second one was a terpolymer, styrene/divinyl benzene/allyl methacrylate (SDBAM), which was synthesized from the monomers and used as an adsorbent. Fe(II/III) removal experiments were conducted in columns and in batch reactors. The results indicated that both SDB compounds were effective for both Fe(II) and Fe(III) removal. The ion‐exchange capacity of SDB‐S was calculated to be 907 mequiv/100 g for Fe(II) and 1100 mequiv/100 g for Fe(III) (which are good quantities). The adsorptive capacity of SDBAM, determined from isotherm calculations, was 79 mequiv/100 g for Fe(II) and 70 mequiv/100 g for Fe(III). This was less than the adsorptive capacity of SDB‐S but acceptable in comparison with common adsorbents. The SDB compounds were more selective for Fe(II). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2696–2703, 2007

Synthesis of macroporous poly(styrene-divinyl benzene) microspheres by surfactant reverse micelles swelling method

Macroporous poly(styrene-divinyl benzene) microspheres with pore size of about 500nm were prepared by a new method, surfactant reverse micelles swelling method. The macroporous microspheres were prepared by convenient suspension polymerization. The difference from conventional suspension polymerization was that a higher concentration of surfactant was added in the oil phase. The effects of the amount and type of surfactants on the morphology of microspheres were investigated, and the formation mechanism was also discussed. Macropores were formed when the concentration of surfactant was much higher than critical micelle concentration (cmc). It was proposed that a large amount of reverse micelles formed by adding a large amount of surfactant in the oil droplet phase, and the reverse micelles could absorb water from the external aqueous phase. The water in the oil phase formed macropores after polymerization. The method developed in this study was convenient to prepare microspheres with larger pore size than the conventional method such as agglomeration method of nanoparticles.

Mössbauer investigation of magnetite nanoparticles incorporated in a mesoporous polymeric template

Mossbauer spectroscopy was used in this study to investigate magnetite-based nanocomposites, using mesoporous styrene-divinylbenzene (Sty-DVB) microspheres as the hosting template. The magnetite content was increased in the polymeric template by performing several in situ chemical reactions (one to six cycles) in the hosting material. We found the Mossbauer linewidth associated to site-A increasing with the relative increase of iron in site-A. The Mossbauer linewidth associated to site-B decreases with the relative decrease of iron in site-B. We explain our findings by assuming local change in the homogeneity associated to changes in the relative iron population in sites A and B.

Quantification of lactobionic acid and sorbitol from enzymatic reaction of fructose and lactose by high-performance liquid chromatography

Experimental conditions for complete separation and quantification of mixtures containing lactobionic acid, sorbitol, lactose and fructose are discussed for the first time. These mixtures appear in the enzymatic bioconversion of fructose and lactose catalyzed by glucose–fructose oxidoreductase (GFOR) and glucono-δ-lactonase (GL) enzymes of Zymomonas mobilis cells. The high-performance liquid chromatography (HPLC) separation was carried out in a strong cation ion exchange resin (hydrogen form) based on a copolymer of styrene divinylbenzene (PS–DVB). A stationary phase of β-cyclodextrin was also evaluated. An efficient separation was obtained with PS–DVB column eluted with sulfuric acid 0.450 mM solutions (pH 3.0–3.2) at 75 °C. The formation of lactones was observed, which is associated with the dissolution of lactobionic acid crystals; however, by dissolving the lactobionic acid crystals on alkaline calcium hydroxyde solution in equimolar ratio a single lactobionic acid chromatographic peak without lactobionolactone is obtained.

Kinetic aspects of SCWO progress of solid organic substances

The specific surface reaction rates of Breasol coal and styrene–divinylbenzene resin particles in sub and supercritical water with O 2 were investigated in the temperature range of 300 – 450 ∘ C at 25 MPa by observing the size change using a shadowgraph method. The rates were approximately proportional to the O 2 concentration and non-linearly dependent on the flow rate. The rate obeyed the Arrhenius law at lower temperatures, but became gradually independent on the temperature above 400 ∘ C , which indicated that the overall reaction is controlled by a certain mass transfer process at the higher temperatures. Compared with the case of coal and activated carbon, much smaller amount of O 2 is enough to result in the rapid size decrease rate in the resin particle.

Solid-phase extraction of nitro-PAH from aquatic samples and its separation by reverse-phase capillary liquid chromatography

In this work, an analytical methodology to extract 1-nitronaphthalene, 2-nitrofluorene, 9-nitroanthracene, 3-nitrofluoranthene, and 1-nitropyrene aquatic samples is proposed. Capillary liquid chromatography with on-column UV detection (µLC-UV) was employed to separate and quantitate all five nitrated polycyclic aromatic hydrocarbons (nitro-PAH) extracted from water samples. Two different extraction techniques were tested and compared: liquid-liquid extraction (LLE) and solid phase extraction (SPE) with two different sorbents, octadecylsilica (C18) and styrene divinylbenzene (XAD-2) particles. The elution of analytes was tested with both acetonitrile and methylene chloride. The best recovery results were obtained for SPE-C18 extraction with the methylene chloride with values ranging from 76 to 97% with RSD values smaller than 4%. The chromatographic conditions for analysis was carried out using a 250 × 0.3 mm i.d. packed capillary column with 5 µm C18 particles. The elution was isocratic with 65% acetonitrile in water (v/v) as mobile phase with a flow rate of 7 µL min-1. The detection limits due to on-column UV detection (ranging ~3-30 mmol L-1) are limiting for environmental applications, however, they are suited for toxicological studies.

Research progress in macroporous styrene-divinylbenzene co-polymer microspheres

Macroporous styrene-divinylbenzene (St-DVB) co-polymer microspheres can be synthesized through the free-radical cross-linking co-polymerization of styrene and divinylbenzene in the presence of an inert diluent. The research developments such as in preparation methods, synthesis variables and various applications achieved in the field of St-DVB co-polymer microspheres during the last few years is presented in this article. It has been shown that pore structures of St-DVB co-polymer microspheres, such as the pore size, the pore size distribution, the total pore volume, as well as the specific surface area, were strongly depended on their synthesis variables, such as the type and amount of the diluent, the amount of DVB and the volume ratio of monomer and diluent.

Analysis of Glucosamine in Cream Dosage Form and Diffusion Liquid by High Performance Liquid Chromatography

A simple and sensitive high performance liquid chromatography (HPLC) method based on a reaction of 1-naphthyl isothiocyanate (NITC) with glucosamine was developed and validated to determine glucosamine in cream dosage form and diffusion liquid. The derivatisation products were cleaned up using styrene divinylbenzene quaternary ammonium ion exchanger and was then analyzed on a reverse-phase C18 column (150 mm × 4.6 mm, 5 μm) using acetonitrile-water-triethylamine (15: 85: 0.05) as the mobile phase and was detected at wavelength of 254 nm. The detector response was linear in the concentration range of 1-1200 μg/ml. The recovery of glucosamine from cream and diffusion liquid were 95.9-97.4% and 97.6-98.4%, respectively. The intra- and inter-day relative standard deviation (%RSD) was less than 5%.

Impregnation synthesis of a novel macroporous silica-based TODGA polymeric composite and its application in the adsorption of rare earths in nitric acid solution containing diethylenetriaminepentaacetic acid

A macroporous silica-based N, N, N′, N′-tetraoctyl-3-oxapentane-1,5-diamide (TODGA) polymeric composite (TODGA/SiO 2-P) was synthesized. It was done through impregnation and immobilization of TODGA molecule into the pores of the SiO 2-P particles utilizing a vacuum sucking technique. The macroporous SiO 2-P particles were the silica-based organic/inorganic composite synthesized by immobilizing styrene–divinylbenzene copolymer inside SiO 2 through the complicated polymerization reaction. The adsorption of rare earth (RE(III)) elements onto TODGA/SiO 2-P was investigated in HNO 3 solution containing diethylenetriaminepentaacetic acid (DTPA), an acidic multi-dentate chelating agent. It was found that in the presence of 0.05 M DTPA, NO 3 - and H + had significant effect on the TODGA/SiO 2-P adsorption due to the competition reactions of RE(III) with different species, H 4DTPA − and H 2DTPA 3−. With an increase in the concentration of NO 3 - from 0.115 M to 3.015 M, the adsorption of RE(III) onto TODGA/SiO 2-P increased noticeably. On the other hand, RE(III) showed strong adsorption at 0.1 M H +, weak adsorption at around pH 2, and no adsorption in excess of pH 2.3. In a 0.1 M H +–0.115 M NO 3 - –0.05 M DTPA solution, a change of the distribution coefficient of RE(III) onto TODGA/SiO 2-P with an increase in atomic number of RE(III) from La(III) to Lu(III) was investigated. The silica-based TODGA/SiO 2-P polymeric composite showed strong adsorption for heavy RE(III) over the light one. In a 0.01 M H +–1.0 M NO 3 - –0.05 M DTPA solution, the effect of the ratio of solid phase to liquid one on the relationship of the distribution coefficient of RE(III) with the change in atomic number of RE(III) was also studied. Based on the complicated disassociation equilibrium of DTPA, the influence of the concentrations of NO 3 - and H + on the adsorption of TODGA/SiO 2-P for RE(III) was demonstrated. This makes the partitioning of RE(III) and MA(III) together from high level liquid waste (HLLW) by the polymeric composite TODGA/SiO 2-P promising.

Comparison of the Porous Structure of Polymeric Beads Obtained by Modified Suspension and Multi-Step Swelling Polymerizations

The porous structures of the polymeric beads obtained by modified suspension and multi-step swelling polymerizations were studied. A porous styrene–divinylbenzene copolymer (ST–DVB) was synthesized in the modified suspension polymerization. In the multi-step polymerization, porous ST–DVB layers of the same chemical composition as obtained in the suspension polymerization were embedded onto polystyrene seed particles obtained in the first step. Three methods were used for investigating the porous structures generated. These were inverse exclusion chromatography, nitrogen adsorption and small X-ray scattering (SAXS). The former was used to characterize the polymer in the swollen state, whereas the latter two were employed with dry polymer samples. The results obtained showed that polystyrene seed particles are porous in the swollen state. However, such pores could not be detected either by nitrogen adsorption or SAXS methods.

Enhanced removal of p-chloroaniline from aqueous solution by a carboxylated polymeric sorbent

In the present study a carboxylated styrene-divinylbenzene (St-DVB) polymeric sorbent (CSPS) was prepared for enhanced removal of p-chloroaniline from aqueous solution. A commercial styrene-divinylbenzene polymeric sorbent Amberlite XAD-4 was selected as the reference sorbent to evaluate the performance of CSPS. Characterization of CSPS was determined by infrared spectroscopy and pore size distribution. A p-chloroaniline sorption enhancement on CSPS at capacity about twice of Amberlite XAD-4 was observed, which was mainly attributed to the carboxyl group added on the polymeric matrix. Different pH-dependent sorption property of p-chloroaniline onto XAD-4 and CSPS was observed partly due to the role of carboxyl group. Sorption isotherm of p-chloroaniline on CSPS could be represented by Freundlich model reasonably, and that on XAD-4 was more suitable for Langmuir model. Kinetic studies demonstrated that the uptake of p-chloroaniline on CSPS and XAD-4 followed the pseudo-second order model. Moreover, breakthrough curves on CSPS further demonstrated its better performance towards p-chloroaniline removal from aqueous solution. Complete regeneration of the spent sorbent CSPS was achieved by dilute hydrochloric acid for its repeated use, implying its potential application in associated chemical wastewater treatments.

Characterization of sulfonated poly(styrene–divinylbenzene) and poly(divinylbenzene) and its application as catalysts in esterification reaction

AbstractPolymeric supports based on divinylbenzene (DVB) were prepared by aqueous suspension polymerization in presence or absence of styrene (S), using toluene and n‐heptane as diluents of the monomers. Poly(S–DVB) and poly(DVB) were sulfonated with sulfuric acid in presence of 1,2‐dichloroethane. The influence of the morphological structure of the supports and as a consequence of the catalyst on the esterification reaction of acetic acid with n‐butanol was evaluated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3616–3627, 2006

Effects of post-crosslinking of macroreticular styrene–divinylbenzene copolymers on their morphology

We performed a detailed comparison of properties of two different styrenic polymers containing divinylbenzene as the crosslinker before and after the introduction of the additional crosslinks by Friedel–Craft's reaction of the residual double bonds. For the polymer characterization was used a wide selection of methods, including nitrogen adsorption/desorption, inverse steric exclusion chromatography, MAS NMR and AFM. The residual double bonds are quite probably located in the dense cores of the microgel domains where steric hindrances prevented them to react during the polymerization. Reinforcement of the cores of polymer microgel domains by transformation of the residual double bonds into additional crosslinks by the Friedel–Craft's reaction results then in greater stability of the already existing pores rather than in creation of new pores by incomplete collapse of swollen polymer gel.