Influence of Stationary Phase Chemistry on Shape Recognition in Liquid Chromatography

Sander, Lane C.; Wise, Stephen A.

doi:10.1021/ac00114a027

Cited by 171 publications

(163 citation statements)

References 38 publications

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“…The less bulky isomer was retained longer presumably, as proposed for the selectivity of polymeric C18 phase for polyaromatic hydrocarbons [19]. In Figure 3, a Newman projection presentation was employed to show the anti-periplanar conformation of the phytyl tail of tocopherol having (R,R,R) configuration at the chiral centers.…”

Section: Resultsmentioning

confidence: 97%

Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure

Yui¹,

Miyazaki²,

et al. 2016

Journal of Chromatography A

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Section: Resultsmentioning

confidence: 97%

Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure

Yui¹,

Miyazaki²,

et al. 2016

Journal of Chromatography A

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“…On the other hand, for silylation with multifunctional silanes, the heterogeneity due to the silanol distributions is reduced, and higher surface coverages (up to ~6.4 µmol/m 2 for silane polymerization in solution) can be achieved. 4,20 Nevertheless, surface heterogeneity arises from deposition and bonding of silane polymers onto the silica surface during synthesis; the silica surface may be covered with clusters of high ligand density, which would induce chain ordering. 8 We initially expected that the locally increased chain density of the DA-β-CD-bonded phase, compared to monomeric RPLC phases, would allow the chains to be more ordered, and therefore, to show enhanced solute shape selectivity.…”

Section: Resultsmentioning

confidence: 99%

“…[5][6][7] This has been ascribed to increased chain ordering in polymeric phases, which results from their alkyl chain organization as a result of higher chain densities. 4,6,[8][9][10][11][12] and simulation 13 studies have shown that chain ordering increases with increasing chain density.…”

Section: Introductionmentioning

confidence: 98%

“…Furthermore, shape selectivity differences are strongly influenced by the kind of surface-modification chemistry used. 4 It has been noted that polymeric octadecylsilane (ODS) silicas provide higher shape selectivity than monomeric counterparts in the separation of PAHs. [5][6][7] This has been ascribed to increased chain ordering in polymeric phases, which results from their alkyl chain organization as a result of higher chain densities.…”

Section: Introductionmentioning

confidence: 99%

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An Attempt Directed toward Enhanced Shape Selectivity in Reversed-Phase Liquid Chromatography: Preparation of the Dodecylaminated β-Cyclodextrin-Bonded Phase

et al. 2002

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Soluteshape selectivity in reversed-phase liquid chromatography (RPLC) has been a topic of much study over the last decade.1,2 Several classes of closely related compounds, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, steroids, and carotenoids, can be separated in RPLC based on the molecular shape. 3 Although the contribution of the reversed-phase material to shape selectivity is not completely understood, there have been a few trends observed in RPLC separations. Shape selectivity varies with carbon loading of the stationary phase, the length of the alkyl-chains bonded to silica gel and the properties of the silica substrate. Also, it is well known that shape selectivity is enhanced by reducing the column temperature or by increasing the organic-modifier content in the mobile phase. Furthermore, shape selectivity differences are strongly influenced by the kind of surface-modification chemistry used. 4 It has been noted that polymeric octadecylsilane (ODS) silicas provide higher shape selectivity than monomeric counterparts in the separation of PAHs. [5][6][7] This has been ascribed to increased chain ordering in polymeric phases, which results from their alkyl chain organization as a result of higher chain densities. 4,6,[8][9][10][11][12] and simulation 13 studies have shown that chain ordering increases with increasing chain density.The purpose of this paper is to report on the synthesis of a new RPLC bonded phase that is designed so as to have regularly spaced, ordered chains on a local level. The possible structure of the prepared stationary phase is depicted in Fig. 1. A number of PAHs were separated with this stationary phase, and its selectivity was compared with those obtained with conventional stationary phases. The preliminary experiments revealed that the new stationary phase offers enhanced molecular shape-recognition performance.It may be noted that, by far, a large number of modified β-CD stationary phases have been synthesized, most of which were directed toward chiral separations, but not toward RPLC separations. An exception to this trend has been presented by i and Ishizuka. 14 They synthesized dodecylamino-β-CD by the reaction of heptakis(6-bromo-6-deoxy)-β-CD with dodecylamine in dimethylformamide. ODS silicas were coated with the produced material and used as a stationary phase for the separation of structural isomers. Experimental Synthesis of the stationary phaseThe preparation procedure of the stationary phase consisted of four separate stages (Fig. 2): (1) silylation of silica gel through reactions of 3-glycidoxypropyltrimethoxysilane with the surface silanol groups, 15 which provides a site for subsequent bonding with dodecylaminated β-CD; (2) sulfonation of the primary hydroxyl groups of β-CD with mesitylsulfonyl chloride, 16 (3) reaction of n-dodecylamine with mesitylenesulfonylated β-CD, yielding n-dodecylamino-derivatized β-CD (DA-β-CD) (the synthesis of heptakis(6-dodecylamino-6-deoxy)-β-CD has been already described by Takahashi et al. 17 ); and (4...

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“…A organossilanização em condições anidras é o método mais utilizado atualmente para a modificação da superfície da sílica e dos óxidos metálicos 17,29,[31][32][33][34][35] . Primeiramente, é necessário ativar os grupos hidroxilas da superfície do óxido através de aquecimento, removendo as moléculas de água ligadas à superfície do óxido por pontes de hidrogênio.…”

Section: Fases Estacionárias Quimicamente Ligadasunclassified

Fases estacionárias para cromatografia líquida de alta eficiência em fase reversa (CLAE-FR) baseadas em superfícies de óxidos inorgânicos funcionalizados

Tonhi¹,

Collins²,

Jardim³

et al. 2002

Quím. Nova

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Recebido em 24/7/01; aceito em 31/10/01 STATIONARY PHASES FOR REVERSED PHASE HIGH PERFORMANCE LIQUID CHROMATOGRAPHY (RP-HPLC) BASED ON FUNCTIONALIZED INORGANIC OXIDE SURFACES. Particles of porous silica or other solvent resistent inorganic oxides can be functionalized by aliphatic (e.g., C-8 or C-18) or other groups to give stationary phases for use in reversed phase HPLC. The functionalization can be done by bonding of individual groups to the surface of the support particles, by producing an organic polymeric film from pre-polymers, or by adsorbing/immobilizing pre-formed polymers on the surfaces. These three types of functionalization are reviewed.Keywords: HPLC; reversed phase; functionalized inorganic oxides. INTRODUÇÃOA Cromatografia Líquida de Alta Eficiência (CLAE) é uma téc-nica de separação que, em menos de trinta anos, passou a ser um dos métodos analíticos mais utilizados para fins qualitativos e quantitativos. As razões para este crescimento estão relacionadas à sua adaptabilidade para determinações quantitativas com boa sensibilidade, a possibilidade de separar espécies não voláteis e termicamente instá-veis, com destaque para a indústria farmacêutica, bem como as suas aplicações em determinações ambientais e em muitos outros campos da ciência, como o da medicina.Dentro da CLAE, estima-se que mais de 90% dos laboratórios de análise espalhados pelo mundo utilizam pelo menos um método que aplica a modalidade de CLAE em fase reversa (FR) 1 . Sistemas de CLAE-FR consistem de uma fase estacionária de menor polaridade e uma fase móvel de maior polaridade, enquanto a fase normal tem as polaridades invertidas. Estas fases apresentam várias vantagens, tais como: uso de fases móveis menos tóxicas e de menor custo, como metanol e água; fases estacionárias estáveis de muitos tipos diferentes; rápido equilíbrio da coluna após a mudança da fase mó-vel; facilidade de empregar eluição por gradiente; maior rapidez em análises e boa reprodutibilidade dos tempos de retenção. Além disso, são muito aplicadas à separação de solutos de diferentes polaridades, massas molares e funcionalidades químicas.O presente trabalho visa revisar as fases estacionárias de CLAE-FR com destaque para os desenvolvimentos recentes. SUPORTESPor mais de 30 anos a sílica tem sido o material preferido para a preparação das fases estacionárias para CLAE-FR, sendo que é mecanicamente estável à altas pressões, pode ser facilmente modificada, existe um vasto conhecimento de sua estrutura e suas propriedades e é comercialmente disponível em uma grande variedade de tamanho de partículas, formas e tamanhos de poros.Por outro lado, as fases baseadas em sílica tendem a serem limitadas em dois aspectos importantes. Um destes aspectos está relacionado à não homogeneidade da sua superfície, que apresenta diferentes tipos de grupos silanóis 2,3 , os quais afetam a funcionalização e, consequentemente, o mecanismo de retenção. Os silanóis (ºSi-OH) são ácidos e podem interagir fortemente com vários tipos de moléculas básicas (fármacos, bio-orgânicos, etc.) e ...

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Influence of Stationary Phase Chemistry on Shape Recognition in Liquid Chromatography

Cited by 171 publications

References 38 publications

Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure

Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure

An Attempt Directed toward Enhanced Shape Selectivity in Reversed-Phase Liquid Chromatography: Preparation of the Dodecylaminated β-Cyclodextrin-Bonded Phase

Fases estacionárias para cromatografia líquida de alta eficiência em fase reversa (CLAE-FR) baseadas em superfícies de óxidos inorgânicos funcionalizados

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