Search results for "Divinylbenzene"
showing 10 items of 13 documents
Synthese substituierter 1,4-Divinylbenzole durch doppelte Heck-Reaktion mit Ethen unter Druck
1999
Substituted 1,4-divinylbenzenes 3a–i were synthesized by twofold Heck coupling from the corresponding 1,4-dibromo) (electron withdrawing substituents) or 1,4-di-iododialkoxybenzenes 1a–i and ethene. Oligomerizations could be suppressed by increasing the pressure of ethene to 30 bar, simultaneously improving the yields of the title compounds.
COMPARATIVE STUDY OF C18- AND STYRENE-DIVINYLBENZENE-BASED SORBENTS FOR THE ENRICHMENT OF PHENOLS FROM WATER
2001
The potential of solid-phase extraction with C18- and styrene divinylbenzene-based sorbents for the preconcentration of phenols from water samples has been evaluated for a variety of phenols of different polarities: phenol, o-, m- and p-cresol, 2-chlorophenol, and 4-chloro-3-methylphenol. The extraction efficiencies have been calculated for different volumes of samples containing the analytes at different concentration levels. The UV limits of detection were of 1–5 ng/mL, for the method using Bond Elut C18 cartridges and sample volumes of 25 mL, and 0.05–0.1 ng/mL (except for 4-chloro-3-methylphenol) for the method using the polymeric sorbent Bond Elut PPL and 1000 mL of the samples. Possib…
A rapid and reliable size-exclusion chromatographic method for determination of kojic dipalmitate in skin-whitening cosmetic products
2007
A size-exclusion chromatographic method has been developed to determine the relatively novel skin-whitening agent called kojic dipalmitate (KDP) in skin-whitening cosmetic products. Preliminary experiments were carried out in order to select the solvent for standard and sample solution, and also for mobile phase composition. A PLGel Mixed-D (polystyrene/divinylbenzene co-polymer) column and isocratic mobile phase of pure tetrahydrofuran (at 1.5 mL min(-1) flow rate) were used. Detection was carried out by means of an UV/vis spectrometry detector set at 248 nm. A study of interferences reveals that KDP can be determined without interferences coming from cosmetic matrices. Most other cosmetic…
Transesterification of rapeseed oil over acid resins promoted by supercritical carbon dioxide
2011
The methanolysis of rapeseed oil catalyzed by commercial styrene-divinylbenzene macroporous acid resins was performed in a batch reactor at 100-140 °C and 10-46 MPa to study the effect of supercritical carbon dioxide (scCO2) on the performances of the process. Reaction temperatures of 120-140 °C were necessary to obtain high enough yields of fatty acid methyl esters. Upon addition of scCO2 faster transesterification kinetics was obtained also at the lowest investigated operating pressure (10-11 MPa), working in two fluid phase systems. Experiments performed changing the reaction time indicated that most of the esters were formed during the first 3 h. When the pressure was increased at 38-46…
Determination of phenolic antioxidants additives in industrial wastewater from polypropylene production using solid phase extraction with high-perfor…
2019
Abstract This paper describes a new method for the effective extraction of the residues of five synthetic phenolic antioxidants (AOs): Ditertbutylphenol (DTF), Irganox 1010, Irganox 1076, Ethanox 330 and Cyanox 1790, from industrial water produced during the polypropylene (PP) deodorization process. In the deordorization process, PP is stored in a column for an average time of four hours and exposed to nitrogen and water vapor to remove inflammable compounds which may generate atypical odors in the PP. The samples of interest were taken in the desorber, followed by cleansing and pre-concentration using modified styrene divinylbenzene polymer cartridges. Liquid chromatography was performed w…
Inhomogeneity of gel and microsyneresis in porous styrene‐divinylbenzene copolymers
1985
The porosity of styrene-divinylbenzene copolymers prepared by suspension copolymerisation of the monomers carried out in the presence of inert diluent changes due to solvent pretreatment is investigated. The changes seem to reflect the inhomogeneity of copolymer gel. Various portions of it are transferred from the rubber-like into the glassy state at different stages of either swelling solvent exchange or the drying process. A microsyneresis, i.e. a local collapse of loosely crosslinked gel portions not followed by a shrinkage of the whole system, leads to the porosity changes.
Comparative evaluation of the swelling and degrees of cross-linking in three organic gel packings for SEC through some geometric parameters.
2003
Abstract The size exclusion chromatographic (SEC) behavior of five solvent/polymer systems in three organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, TSK-Gel H HR , μ-styragel and TSK-Gel H XL , has been compared. All the packings offer similar characteristics (pore size, particle size and efficiency) but some differences have been found when eluting the same systems. The different elution behavior observed in both polymeric gels has been analyzed in terms of their swelling and cross-linking degrees and of the fractal parameters. From the Universal Calibration plots, values of the chromatographic partition coefficient, K p , have been obtained and using some eq…
SPME of 52 pesticides and polychlorinated biphenyls: Extraction efficiencies of the SPME coatings poly(dimethylsiloxane), polyacrylate, poly(dimethyl…
2001
Fiber/water partition coefficients (Kfw) of 52 pesticides, including triazines, organophosphorus pesticides, organochlorine pesticides, and polychlorinated biphenyls (PCBs) were experimentally calculated for the five polymeric coatings poly(dimethylsiloxane) (PDMS), polyacrylate (PA), poly(dimethylsiloxane)-Divinylbenzene (PDMS-DVB), Carboxen-poly(dimethylsiloxane) (CAR-PDMS), and Carbowax-divinylbenzene (CW-DVB) commercially available for solid-phase microextraction coupled to gas chromatography. The equilibrium-time profiles for the five coatings were previously studied in order to establish the time needed for equilibrium. To calculate Kfw the amount of analyte extracted at equilibrium w…
An Analysis of the Concentration Effects on Elution Volumes by Using the Preferential Solvation Parameter in Two SEC Packings
2002
Size exclusion chromatography (SEC) elution behavior of different solvent/polymer systems has been analyzed from chromatographic, thermodynamic, and hydrodynamic points of view in two organic column packings based on polystyrene/divinylbenzene (PS/DVB) copolymer, μ-styragel and TSK-Gel H HR . Although both packings present similar chromatographic properties, some differences arise when eluting the same systems. The values of the adsorption distribution coefficients, K p , have been correlated with the preferential solvation coefficient, λ (see Figure), for both packings, showing that those systems with lower and negative λ values (denoting higher preferential solvation of the polymer by the…
Preparation of monodisperse polyethylene oxides by gel permeation chromatography of discontinuous polymer-homologous series
1970
Abstract Starting from triethylene glycol, monodisperse polyethylene oxides of a molecular weight (MW) up to 2000 (degree of polymerisation (DP) During the first step the ditosylate of triethylene glycol is reacted with the sodium alkoxide of the same diol at room temperature. The condesation product (polymer homologues of triethylene glycol) was separated by molecular distillation and yielded the pure oligomers nonaethylene glycol (DP = 9, MW 414) and pentadecaethylene glycol (DP = 15, MW = 678), as proved by gel chromatography. During the next step the polymer homologues of nonaethylene glycol were synthesised in a similar way. The pure oligomers hepteicosa (DP = 27, MW = 1207) and pentat…