Página 1 dos resultados de 53 itens digitais encontrados em 0.000 segundos

External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column

VAZ, Fernando Antonio Simas; CASTRO, Patricia Mendonca de; MOLINA, Celso; RIBEIRO, Sidney Jose Lima; POLACHINI, Ferminio Cesar; MESSADDEQ, Younes; NUNES, Adriana Palombo; OLIVEIRA, Marcone Augusto Leal de
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
27.88%
Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 mu m i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximate to 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene. (C) 2008 Elsevier B.V. All rights reserved.

External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column

Simas Vaz, Fernando Antonio; de Castro, Patricia Mendonca; Molina, Celso; Lima Ribeiro, Sidney Jose; Polachini, Ferminio Cesar; Messaddeq, Younes; Nunes, Adriana Palombo; Leal de Oliveira, Marcone Augusto
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 226-229
ENG
Relevância na Pesquisa
27.68%
Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 mu m i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximate to 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene. (C) 2008 Elsevier B.V. All rights reserved.

Optimization of photo-polymerized sol gel monolithic stationary phases prepared in polyacrylate-coated fused-silica capillaries for capillary electrochromatography

Simas Vaz, Fernando Antonio; Moutinho, Arthur Damasio; Rodrigues Furtado de Mendonca, Jose Paulo; de Araujo, Ricardo Tavares; Lima Ribeiro, Sidney Jose; Polachini, Ferminio Cesar; Messaddeq, Younes; Leal de Oliveira, Marcone Augusto
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 21-26
ENG
Relevância na Pesquisa
37.68%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The preparation of photo-polymerized sol-gel monolithic stationary phases (MSP) within 100 mu m internal diameter polyacrylate-coated fused-silica capillaries for use in capillary electrochromatography (CEC) was optimized. Eight mixtures containing different amounts of methacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid solution as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photo-initiator were irradiated at 370 nm inside the capillaries in order to complete the MSP polymerization, according to a fractional factorial experimental design 2(IV)(4-1). All the preparation procedure, from capillary pretreatment until the MSP is ready to use in CEC, were made in less than four hours in mild conditions. A high pressurization injection device (HPID) useful for micro-volume syringes was built in order to achieve practical, controlled and precise injections of sols, solvents and electrolytes in the capillaries. The eight MSP were equally washed, conditioned and submitted to CEC procedures via short-end injection...

Desenvolvimento e caracterização de fases estacionárias monolíticas à base de octadecilmetacrilato para uso em eletrocromatografia capilar; Development and characterization of octadecyl methacrylate-based monolithic stationary phases for use in capillary electrochromatography

Valeska Soares Aguiar
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/12/2011 PT
Relevância na Pesquisa
37.68%
A Eletrocromatografia Capilar (CEC) é uma técnica de separação que combina a seletividade cromatográfica da Cromatografia Líquida de Alta Eficiência (HPLC) com a alta eficiência da Eletroforese Capilar (CE). A coluna capilar usada na separação é preenchida com uma fase estacionária, que pode ser do tipo particulada ou monolítica. Neste trabalho, monolitos poliméricos orgânicos foram preparados por polimerização in situ a partir dos monômeros octadecilmetacrilato (precursor e seletor hidrofóbico), etilenodimetacrilato (agente de entrecruzamento) e ácido 2-acriloilamido-2- metilpropanossulfóxido (monômero ionizável), além de diferentes tipos de solventes porogênicos, como álcool isoamílico, amílico, cicloexanol e 1,4- butanodiol, na presença e na ausência de água. Na primeira etapa do trabalho, variaram-se a natureza e a proporção entre os solventes porogênicos e, na segunda, o mesmo ocorreu com a proporção entre o conjunto de monômeros e de solventes porogênicos. As fases estacionárias foram caracterizadas por técnicas físicas como a microscopia eletrônica de varredura e a porosimetria; e as colunas moldadas com o material monolítico foram avaliadas pela técnica de CEC. As colunas apresentaram eficiência na faixa de 3000 a 50000 pratos m. A análise das isotermas de adsorção e dessorção de nitrogênio e das curvas de distribuição de poros permitiu afirmar que o material monolítico sintetizado é essencialmente micro e mesoporoso. Os macroporos para fluxo de fase móvel foram nitidamente observados em imagens de microscopia eletrônica de varredura. Assim...

Síntese e caracterização de nova fase monolítica para eletrocromatografia capilar usando método sol-gel; Synthesis and characterization of a new monolithic phase for capillary electrochromatography by sol-gel method

María de Jesús Santa Gutiérrez Ponce
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/07/2011 PT
Relevância na Pesquisa
27.34%
Monolitos à base de sílica têm sido usados como fases estacionárias em eletrocromatografia capilar e apresentam vantagens em relação aos materiais particulados tais como: melhor homogeneidade; controle do tamanho dos poros; alta estabilidade mecânica e térmica; minimização da formação de bolhas e diminuição de problemas com filtros. O presente trabalho teve como objetivo a síntese e caracterização de uma nova fase estacionária monolítica à base de sílica com grupos carboxílicos em sua estrutura, os quais ajudam a sustentar o fluxo eletrosmótico e conferem características de troca catiônica à fase. A fase estacionária monolítica foi sintetizada empregando o processo sol-gel. A síntese do agente sililante foi feita a partir de ácido 4-aminobenzóico e trietóxipropilisocianatossilano. A derivatização da fase estacionária monolítica foi feita adicionando-se ao monolito uma solução de 10% do silano em DMF e deixando reagir por 6 horas a 60 °C. A fase estacionária monolítica funcionalizada foi avaliada por microscopia eletrônica de varredura, espectroscopia no infravermelho e análise elementar. A fase estacionária também foi testada com um equipamento de eletroforese capilar construído no laboratório com detecção condutométrica sem contato (CD) e um equipamento de eletroforese capilar Agilent com detecção UV. Os resultados da microscopia eletrônica confirmaram a formação do monolito dentro do capilar e a espectroscopia no infravermelho...

Fases estacionárias monolíticas para separações cromatográficas

Faria,Anízio M.; Bottoli,Carla B. G.; Jardim,Isabel C. S. F.; Collins,Carol H.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2006 PT
Relevância na Pesquisa
27.34%
Monolithic stationary phases represent a new generation of chromatographic separation media. These phases consist of a continuous separation bed prepared by in situ polymerization or consolidation inside the column tubing. In recent years, their simple preparation procedure, unique properties and excellent performance have attracted quite remarkable attention in liquid chromatography and capillary electrochromatography. This review summarizes the preparation, characterization and applications of monolithic stationary phases. The analytical potential of these columns is demonstrated with separations involving various families of compounds in different separation modes.

Eletrocromatografia capilar: contextualização, estado da arte e perspectivas

Segato,Milena Pinotti; Silva,César Ricardo; Jardim,Isabel Cristina Sales Fontes
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 PT
Relevância na Pesquisa
27.68%
Capillary electrochromatography (CEC) is a separation technique in which the mobile phase flow is based on the application of a voltage across a packed capillary, which generates an electroosmotic flow that transports the analytes along the capillary toward the detector. As it combines the separation mechanisms of high-performance liquid chromatography (HPLC) and of capillary electrophoresis (CE), CEC can be considered a hybrid of HPLC and CE. This review presents some fundamental aspects of CEC and is focused on the instrumental advances of the technique, such as column technology, operation modes and detection systems, presenting recent papers on these topics and some applications and perspectives about CEC.

CONSTRUÇÃO DE UM DISPOSITIVO DE PRESSURIZAÇÃO A VÁCUO PARA A PREPARAÇÃO DE FASES ESTACIONÁRIAS MONOLÍTICAS VIA PROCESSO SOL-GEL

Ribeiro,Sandro Pereira; Vaz,Fernando Antonio Simas; Oliveira,Marcone Augusto Leal de; Mendes,Thiago de Oliveira; Mendonça,José Paulo Rodrigues Furtado de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 PT
Relevância na Pesquisa
27.34%
The filling of capillaries via the sol-gel process is growing. Therefore, this technical note focuses on disseminating knowledge acquired in the Group of Analytical Chemistry and Chemometrics over seven years working with monolithic stationary phase preparation in fused silica capillaries. We believe that the detailed information presented in this technical note concerning the construction of an alternative high pressurization device, used to fill capillary columns via the sol-gel process, which has promising potential for applications involving capillary electrochromatography and liquid chromatography in nano scale, may be enlightening and motivating for groups interested in developing research activities within this theme.

A comparative study on analytical method of total alkaloids from cortex Phellodendri amurens by reversed phase high performance liquid chromatography (RP-HPLC) and pressurized capillary electrochromatography (pCEC)

Yang,Bo; Zhang,Xiaoying; Zhang,Rusong
Fonte: Sociedade Brasileira de Farmacognosia Publicador: Sociedade Brasileira de Farmacognosia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2011 EN
Relevância na Pesquisa
37.68%
A pressurized capillary electrochromatography (pCEC) method with post-column detection cell has been developed for the analysis of total alkaloids of cortex Phellodendron amurense Rupr., Rutaceae. The separation of total alkaloids (berberine, palmatine, oatrorrhizine, magnoflorine, phellodendrine, candicine, menisperine) was optimized by compositions of the mobile phase, ionic strength of buffers, pH value, and applied voltage. Separation of total alkaloids was achieved within 11 min by using a mobile phase of Na2HPO4-citric acid solution-acetonitrile (pH 4.00; 3 mM) (60:40, v/v) and applying a voltage of -10 kV. This method showed satisfactory retention times and peak shapes. Meanwhile, a reversed phase high performance liquid chromatography (RP-HPLC) has also been established for the separation of total alkaloids extracted from cortex Phellodendri amurens. Baseline separation of total alkaloids was achieved within 25 min by using a mobile phase of acetonitrile-0.1% phosphoric acid with 0.1 g sodium dodecanesulphonate per 100 mL (35:65, v/v). Compared to conventional RP-HPLC, pCEC led to higher column efficiency, less consumption of reagent, and shorter analysis time.

Physical and electrophoretic characterization of octadecyl methacrylate-based monolithic columns for use in capillary electrochromatography

Aguiar,Valeska S.; Bottoli,Carla B. G.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2013 EN
Relevância na Pesquisa
37.68%
Organic monolithic columns with high efficiency were obtained for use in capillary electrochromatography (CEC) from a mixture of monomers (constant concentrations) with different proportions of porogenic solvents (1,4-butanediol with isoamyl alcohol, amyl alcohol or cyclohexanol in the presence or absence of water). The stationary phases were prepared from the precursor monomer octadecyl methacrylate (ODMA), the cross-linking agent ethylene dimethacrylate (EDMA) and the ionizable monomer 2-acryloylamido-2-methylpropanesulfonic acid (AMPS), the latter being necessary to make the stationary phase negatively charged, assuring electrosmotic flow (EOF) during analysis. The monolithic columns synthesized were physically characterized by porosimetry and scanning electron microscopy (SEM), and electrochromatographically characterized by calculation of chromatographic parameters. The most efficient column was prepared using the porogenic solvent amyl alcohol:1,4-butanediol in a 65:35 (v/v) ratio and showed a plate height of 38 µm. These columns were applied for the separation of alkyl parabens and polycyclic aromatic hydrocarbons (PAH).

Optimized Separation Method for Estriol, 17-β-Estradiol and Progesterone by Capillary Electrochromatography with Monolithic Column and its Application to a Transdermal Emulsion

Marques,Rafael; Vaz,Fernando A. S.; Polonini,Hudson C.; Oliveira,Marcone A. L. de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2015 EN
Relevância na Pesquisa
37.68%
A monolithic stationary phase based on 3-(methacryloxypropyl)trimethoxysilane monomer, prepared within a fused silica capillary externally coated with a UV-transparent fluoropolymer was employed for separation of estriol, 17-b-estradiol and progesterone by capillary electrochromatography in a standard mixture. A 23 factorial design was used to optimize the separation system. The optimized condition containing 30% (v/v) of acetonitrile and 10 mmol L-1 aqueous ammonium acetate presented a total run time less than 10 min by applying 25 kV. The resolution between adjacent peaks ranged from 1.8 up to 2.9 and the plate numbers per column meter in this condition was 1873, 3631 and 3886 for the estriol, 17-b-estradiol and progesterone peaks, respectively. The optimized method was employed in the quantitative analysis of a commercial transdermal emulsion formulation.

Determination of parabens in sweeteners by capillary electrochromatography

Bottoli,Carla Beatriz Grespan; Gutiérrez-Ponce,María de Jesús Santa; Aguiar,Valeska Soares; Aquino,Walkyria Moraes de
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 EN
Relevância na Pesquisa
27.34%
Parabens, common food preservatives, were analysed by capillary electrochromatography, using a commercial C18 silica (3 µm, 40 cm × 100 µm i. d.) capillary column as separation phase. In order to optimise the separation of these preservatives, the effects of mobile phase composition on the separation were evaluated, as well as the applied voltage and injection conditions. The retention behavior of these analytes was strongly influenced by the level of acetonitrile in the mobile phase. An optimal separation of the parabens was obtained within 18.5 minutes with a pH 8.0 mobile phase composed of 50:50 v/v tris(hydroxymethyl)aminomethane buffer and acetonitrile. The method was successfully applied to the quantitative analysis of paraben preservatives in sweetener samples with direct injection.

Porous Polyacrylamide Monoliths in Hydrophilic Interaction Capillary Electrochromatography of Oligosaccharides

Guryča, Vilém; Mechref, Yehia; Palm, Anders K.; Michálek, Jiří; Pacáková, Věra; Novotný, Miloš V.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.34%
Capillary electrochromatography (CEC) of oligosaccharides in porous polyacrylamide monoliths has been explored. While it is possible to alter separation capacity for various compounds by copolymerization of suitable separation ligands in the polymerization backbone, “blank” acrylamide matrix is also capable of sufficient resolution of oligosaccharides in the hydrophilic interaction mode. The “blank” acrylamide network, formed with a more rigid crosslinker, provides maximum efficiency for separations (routinely up to 350,000 theoretical plates/m for fluorescently-labeled oligosaccharides). These columns yield a high spatial resolution of the branched glycan isomers and large column permeabilities. From the structural point of view, some voids are observable in the monoliths at the mesoporous range (mean pore radius ca. 35 nm, surface area of 74 m2/g), as measured by intrusion porosimetry in the dry state.

Optimized separation of β-blockers with multiple chiral centers using capillary electrochromatography–mass spectrometry☆

Bragg, William; Norton, Dean; Shamsi, Shahab A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/11/2008 EN
Relevância na Pesquisa
27.34%
This work focuses on the simultaneous analysis of β-blockers with multiple stereogenic centers using capillary electrochromatography–mass spectrometry (CEC–MS) with a vancomycin stationary phase. The critical mobile phase variables (composition of organic solvents, acid/base ratios) as well as column temperature and electric field strength, effecting enantioresolution and analysis time were first optimized sequentially. Next, to achieve global optimum a multivariate D-optimal design was used. Although multivariate approach did not improve enantioresolution any further, analysis time was significantly reduced. Under optimum CEC–MS conditions, all stereoisomers were resolved with resolution in the range 1.0−3.1 in less than 60 min with an average signal-to-noise (S/N) greater than 1000. The developed CEC–MS method has the potential to emerge as a screening method for analysis of multiple chiral compounds using a single protocol using the same column and mobile phase conditions, thus reducing the operation time and cost.

Sulfated and sulfonated polysaccharide as chiral stationary phases for capillary electrochromatography and capillary electrochromatography–mass spectrometry

Zheng, Jie; Bragg, William; Hou, Jingguo; Lin, Na; Chandrasekaran, Sekar; Shamsi, Shahab A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.68%
The applications of polysaccharide phenyl carbamate derivatives as chiral stationary phases (CSPs) for capillary electrochromatography (CEC) are often hindered by longer retention times, especially using a normal-phase (NP) eluent due to very low electroosmotic flow (EOF). Therefore, in this study, we propose an approach for the aforementioned problems by introducing two new types of negatively charged sulfate and sulfonated groups for polysaccharide CSPs. These CSPs were utilized to pack CEC columns for enantioseparation with a NP eluent. Compared to conventional cellulose tris(3,5-dimethylphenyl carbamate) or CDMPC CSPs, the sulfated CDMPC CSP (sulfur content 4.25%, w/w) shortened the analysis time up to 50% but with a significant loss of enantiomeric resolution (~60%). On the other hand, the sulfonated CDMPC CSP (sulfur content 1.76%, w/w) not only provided fast throughput but also maintained excellent resolving power. In addition, its synthesis is much more straightforward than the sulfated one. Furthermore, we studied several stationary phase parameters (CSP loading and silica gel pore size) and mobile phase parameters (including type of mobile phase and its composition) to evaluate the throughput and enantioselectivity. Using the optimized conditions...

Capillary electrochromatography: Selected developments that caught my eye since the year 2000

Svec, Frantisek
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/2009 EN
Relevância na Pesquisa
27.34%
During the last decade, a number of new developments have emerged in the field of capillary electrochromatography (CEC). This paper focuses only on monolithic columns prepared from synthetic polymers. Monolithic columns have become a well-established format of stationary phases for CEC immediately after their inception in the mid 1990s. They are readily prepared in situ from liquid precursors. Also, the control over both porous properties and surface chemistries is easy to achieve. These advantages make the monolithic separation media an attractive alternative to capillary columns packed with particulate materials. Since the number of papers concerned with just this single topic of polymer-based monolithic CEC columns is large, this overview describes only those approaches this author found interesting.

Surfactant-Bound Monolithic Columns for Capillary Electrochromatography

Gu, Congying; He, Jun; Jia, Jinping; Fang, Nenghu; Shamsi, Shahab A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/2009 EN
Relevância na Pesquisa
27.34%
A novel anionic surfactant bound monolithic stationary phase based on 11-acrylaminoundecanoic acid (AAUA) is designed for capillary electrochromatography (CEC). The monolith possessing bonded undecanoyl groups (hydrophobic sites) and carboxyl groups (weak cationic ion-exchange sites) was evaluated as a mixed-mode stationary phase in CEC for the separation of neutral and polar solutes. Using a multivariate D-optimal design the composition of the polymerization mixture was modeled and optimized with five alkylbenzenes (ABs) and seven alkyl phenyl ketones (APKs) as test solutes. The D-optimal design indicates a strong dependence of electrochromatographic parameters on the concentration of AAUA monomer and porogen (water) in the polymerization mixture. A difference of 6%, 8% and 13% RSD between the predicted and the experimental values in terms of efficiency, resolution, and retention time, respectively, indeed confirmed that the proposed approach is practical. The physical (i.e., morphology, porosity and permeability) and chromatographic properties of the monolithic columns were thoroughly investigated. With the optimized monolithic column, high efficiency separation of N-methylcarbamates (NMCs) pesticides and positional isomers was successfully achieved. It appears that this type of mixed-mode monolith (containing both chargeable and hydrophobic sites) may have a great potential as a new generation of CEC stationary phase.

Development of Advanced Capillary Electrophoresis Techniques with UV and Mass Spectrometry Detection for Forensic, Pharmaceutical and Environmental Applications

Fu, Hanzhuo
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
Relevância na Pesquisa
27.68%
Capillary electrophoresis (CE) is a modern analytical technique, which is electrokinetic separation generated by high voltage and taken place inside the small capillaries. In this dissertation, several advanced capillary electrophoresis methods are presented using different approaches of CE and UV and mass spectrometry are utilized as the detection methods. Capillary electrochromatography (CEC), as one of the CE modes, is a recent developed technique which is a hybrid of capillary electrophoresis and high performance liquid chromatography (HPLC). Capillary electrochromatography exhibits advantages of both techniques. In Chapter 2, monolithic capillary column are fabricated using in situ photoinitiation polymerization method. The column was then applied for the separation of six antidepressant compounds. Meanwhile, a simple chiral separation method is developed and presented in Chapter 3. Beta cycodextrin was utilized to achieve the goal of chiral separation. Not only twelve cathinone analytes were separated, but also isomers of several analytes were enantiomerically separated. To better understand the molecular information on the analytes, the TOF-MS system was coupled with the CE. A sheath liquid and a partial filling technique (PFT) were employed to reduce the contamination of MS ionization source. Accurate molecular information was obtained. It is necessary to propose...

Miniaturisierte Trennverfahren und ihre On-line-Kopplung mit der NMR Spektroskopie: Entwicklung und Anwendungen; On-line coupling of miniaturized separation techniques with nuclear magnetic resonance spectroscopy: development and applications

Rapp, Erdmann
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
DE_DE
Relevância na Pesquisa
27.68%
In der vorliegenden Arbeit wurde zum einen die Entwicklung und Anwendung modularer Apparaturen für den flexiblen Einsatz miniaturisierter Trennmethoden wie cHPLC, CEC und Gradienten-(p)CEC vorgestellt. Zum anderen wurde eine Methode weiterentwickelt, die es ermöglicht, frittenlose strapazierfähige (elektro-)chromatographische Kapillarsäulen apparativ einfach und rationell, in reproduzierbarer Qualität herzustellen und dabei eine hohe Variabilität in der Wahl des Packungsmaterials und der Säulenlänge gewährleistet. Im letzten Teil dieser Arbeit wird die Entwicklung der on-line-Kopplung von Kapillartrenntechniken mit der NMR-Spektroskopie beschrieben. Hier gelang zum ersten Mal die splittlose Kopplung mit der cHPLC, CEC und der pCEC. Im Rahmen dieser Arbeit wurde ein Konzept zur Herstellung von Kapillarsäulen mit einer Fritte sowie von Kapillarsäulen ohne jegliche Fritte entwickelt. Beide erlauben den Austausch gebrochener UV-Detektionsfenster und eignen sich sowohl zur on-line-Kopplung von CEC, pCEC und cHPLC mit der NMR Spektroskopie, als auch mit der Massenspektrometrie. Ihre Herstellung wurde im Detail beschrieben. Die Qualität der selbst hergestellten (elektro-)chromatographischen Kapillarsäulen wurde mit Hilfe eines Benzoesäureester-Testgemisches überprüft. Dazu wurde eine Serie von van-Deemter-Kurven vermessen...

Nanoparticles as a tool in capillary electrochromatography

Ribeiro, Susana
Fonte: Universidade da Beira Interior Publicador: Universidade da Beira Interior
Tipo: Dissertação de Mestrado
Publicado em //2009 ENG
Relevância na Pesquisa
28.02%
Two different types of molecularly imprinted nanoparticles against (R)-propranolol were used to separate the enantiomers of propranolol in capillary electrochromatography mode, methacrylic acid based nanoparticles and core-shell molecularly imprinted polymer nanoparticles. Partial filling technique was used to avoid interference of molecularly imprinted polymer nanoparticles in UV detection. With methacrylic acid based nanoparticles it was not possible to obtain enantiomer separation. Strong unspecific interactions between the molecular imprinted polymer nanoparticles and propranolol disturbed enantiomer separation. Since large content of acetonitrile had to be used in order to obtain stable suspensions of molecularly imprinted polymer nanoparticles, the electrostatic interactions were favored which contributed to the unspecific interactions occurring. Core-shell molecularly imprinted polymer nanoparticles present suspension stability at low content of acetonitrile due to the poly(acrylamide) shell that makes them more hydrophilic. Enantiomer separation of propranolol was achieved with 40% of acetonitrile. Reproducibility was problematic due to the unspecific interactions occurring. With time several factors can occur contributing to the decreased reproducibility of results such as...