Search results for "Monolith"
showing 10 items of 90 documents
Development of pipette tip-based poly(methacrylic acid-co-ethylene glycol dimethacrylate) monolith for the extraction of drugs of abuse from oral flu…
2019
Abstract In this work, a monolithic polymer based on poly(methacrylic acid-co-ethylene glycol dimethacrylate) (MAA-co-EDMA) was prepared inside 200 μL pipette tips for the extraction of drug of abuse from oral fluid samples. After an appropriate surface tip modification, several polymerization mixtures with different monomer/cross-linker ratios, and percentage of porogen were studied. The most appropriate monolith to easily flow organic solvents and oral fluid samples was prepared with a MAA/EDMA ratio of 8:92 wt/wt and dodecanol containing 10 wt% toluene, as porogenic solvent. Parameters affecting the extraction procedure were evaluated and the monolith was characterized in terms of bindin…
Determination of tocopherols in vegetable oils by CEC using methacrylate ester-based monolithic columns
2007
The separation and determination of tocopherols (Ts) in vegetable oils by CEC using methacrylate ester-based monolithic columns has been developed. The effects of pore size of the monolithic columns were studied, and the composition of mobile phase was optimized. The optimal pore size of the monolith was obtained with 12 wt% 1,4-butanediol in the polymerization mixture. Excellent resolution between tocopherols was achieved within 10 min analysis time with a 99:1 v/v MeOH-aqueous buffer containing 5 mM tris(hydroxymethyl)aminomethane at pH 8.0. The LODs were lower than 2.3 microg/mL, and interday and column-to-column reproducibilities at 25 microg/mL were better than 5.6%. Using a 93:7 v/v M…
Effect of Impregnation and Activation Conditions of Al2O3/CuO Supported Monolith Catalysts in the Reduction of NO
1979
Reduction of NO in the presence of CO and Ar was examined on two series of monolithic sheets carrying an active CuO/Al 2 O 3 layer. In the impregnation procedure the ratio of Al 2 O 3 to CuO was varied in a wide range. The texture of the layer and the dispersion of CuO therein was controlled by mercury porosimetry, scanning electron microscopy and secondary ion mass spectrometry (SIMS). It could be established that the surface concentration of CuO determined by SIMS measurements is the most decisive quantity of the catalyst correlating linearly with the conversion of NO.
Development of a software package with GUI for the evaluation of monolithicity factors of RC jacketed columns
2023
The design of reinforced concrete (RC) jacketing for retrofitting substandard columns is a common practice when approaching the structural rehabilitation design of existing structures. In this framework, international technical codes suggest to assume the hypothesis of monolithic section and finally affecting the deduced performances by some empirical factors, known in the literature as monolithicity factors. The assessment of these coefficients is a difficult task, and only some rough assumptions can be found in the modern codes. This paper presents the development of a software package able to perform the static non-linear analysis of RC jacketed columns and evaluating the actual value of…
Zwitterionic codeine-derived methacrylate monoliths for enantioselective capillary electrochromatography of chiral acids and chiral bases
2018
Thiol-ene click reaction of N-acetyl-L-cysteine methyl ester to codeine, followed by reaction with allyl isocyanate and hydrolysis to the corresponding zwitterionic chiral selector and its subsequent bonding to the surface of a methacrylate monolith provided a new chiral capillary column for enantiomer separation of chiral acids and chiral bases. First, the epoxy groups of a poly(glycidyl methacrylate-co-ethylene dimethacrylate) monolith were converted into amine residues, followed by reaction with allylglycidyl ether. In this way, a spacer arm was bonded to the surface before coating and cross-linking poly(3-mercaptopropyl methylsiloxane) (PMPMS) via radical addition (thiol-ene click react…
Solid-phase extraction based on ground methacrylate monolith modified with gold nanoparticles for isolation of proteins
2015
In this study, a novel polymeric material functionalized with gold nanoparticles (AuNPs) was prepared as solid-phase extraction (SPE) sorbent for isolation of proteins. The sorbent was synthesized from a powdered poly(glycidyl-co-ethylene dimethacrylate) monolith, and modified with ammonia, followed by immobilization of AuNPs on the pore surface of the material. To evaluate the performance of this SPE support, proteins were selected as test solutes, being the extraction conditions and other parameters (loading capacity and regenerative ability of sorbent) established. The results indicated that this sorbent could be employed to selectively capture proteins according to their pI, on the basi…
Novel monolithic materials for miniaturized separation techniques
2015
En esta tesis, se describe el uso de nuevos materiales porosos polimericos y su potencial aplicación en técnicas de separación miniaturizadas. La primera sección (capítulos 1-3), contiene una introducción general, donde el impacto de los materiales polímeros (capítulo 2)en cromatografía es discutido. En el capítulo 3, se presenta una introducción a la caracterización de algunos polímeros y aceites esenciales. Los capítulos 1-3 se escribieron siguiendo la normativa de la Universidad Valencia. La segunda parte de esta tesis está enfocada en la preparación, caracterización y aplicación de nuevos materiales monoíticos usados en cromatografía líquida capilar y electrocromatografía (CEC). En esto…
Rapid determination of sterols in vegetable oils by CEC using methacrylate ester-based monolithic columns
2008
A method for the determination of sterols in vegetable oils by CEC with UV-Vis detection, using methacrylate ester-based monolithic columns, has been developed. To prepare the columns, polymerization mixtures containing monomers of different hydrophobicities were tried. The influence of composition of polymerization mixture was optimized in terms of porogenic solvent, monomers/porogens and monomer/crosslinker ratios. The composition of the mobile phase was also studied. The optimum monolith was obtained with lauryl methacrylate monomer at 60:40% (wt:wt) lauryl methacrylate/ethylene dimethacrylate ratio and 60 wt% porogens with 20 wt% of 1,4-butanediol (12 wt% 1,4-butanediol in the polymeriz…
Influence of photo-initiators in the preparation of methacrylate monoliths into poly(ethylene-co-tetrafluoroethylene) tubing for microbore HPLC.
2020
[EN] In this study, poly(butyl methacrylate-co-ethyleneglycol dimethacrylate) polymeric monoliths were in situ developed within 0.75 mm i.d. poly(ethylene-co-tetrafluoroethylene) (ETFE) tubing by UV polymerization via three different free-radical initiators fscce-azobisisobutyronitrile (AIBN), 2,2-dimethoxy-2-phenylacetophenone (DMPA) and 2-methyl-4'-(methylthio)-2-morpholinopropiophenone (MTMPP). The influence of the nature of each photo-initiator and irradiation time on the morphological features of the polymer was investigated by scanning electron microscopy, and the chromatographic properties of the resulting microbore columns were evaluated using alkyl benzenes as test substances. The …
A New Planar Microstrip Resonator for Microwave Circuits: The Quasi-Fractal Microstrip Resonator
1999
a new shape for microwave planar circuits using the self-similarity of the fractal geometry is presented. This new shape allows the generation of numerous resonant frequencies for this microwave planar resonator due to the surfaces encasilng. The resonant frequency assessment can be useful to concept specific filters or wide frequency band matching loads as examples, without consuming circuit surface.