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1.
J Sep Sci ; 30(12): 1844-51, 2007 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-17638361

RESUMO

Stationary phases for RP-HPLC were prepared from metalized (titanized and zirconized) and unmodified silica particles using sorbed and immobilized poly(methyltetradecylsiloxane) (PMTDS). Different immobilization procedures, such as gamma irradiation and thermal treatments, were used for the preparation of the immobilized PMTDS phases. The stabilities of these stationary phases were evaluated by passing alkaline (pH 10) mobile phase through 60 mm x 3.9 mm columns of the different phases, with periodic tests to evaluate chromatographic performance. The results show that higher stabilities were obtained with stationary phases based on PMTDS immobilized on zirconized silica, these phases being 50% more stable than their titanized silica counterparts and 400% more stable than those based on unmodified silica. These supports provide higher chemical stability to the laboratory-made stationary phases, when compared with chemically bonded silica-based phases.


Assuntos
Técnicas de Química Analítica/métodos , Cromatografia Líquida de Alta Pressão/métodos , Dióxido de Silício/química , Siloxanas/química , Adsorção , Carbono/química , Cromatografia/métodos , Concentração de Íons de Hidrogênio , Metais/química , Modelos Químicos , Siloxanas/isolamento & purificação , Fatores de Tempo , Zircônio/química
2.
J Chromatogr A ; 1119(1-2): 135-9, 2006 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-16430910

RESUMO

Reversed phases for high-performance liquid chromatography (RP-HPLC) were obtained by thermal immobilization of polysiloxanes having different length chains (C1, C8 and C14) onto HPLC silica particles. The importance both of percent loading of the stationary phase promoted by each immobilization procedure and of the length of the lateral chain of the polymer on the chromatographic performances of the phases obtained is compared and discussed.


Assuntos
Cromatografia Líquida de Alta Pressão/instrumentação , Cromatografia Líquida de Alta Pressão/métodos , Dióxido de Silício/química , Siloxanas/química , Acenaftenos/isolamento & purificação , Compostos de Anilina/isolamento & purificação , Derivados de Benzeno/isolamento & purificação , Temperatura Alta , Interações Hidrofóbicas e Hidrofílicas , Naftalenos/isolamento & purificação , Fenol/isolamento & purificação , Uracila/isolamento & purificação
3.
J Pharm Biomed Anal ; 39(1-2): 17-21, 2005 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-15935597

RESUMO

A comparison between dissolution profiles obtained by using a dissolution apparatus (conventional method) and the NIR diffuse reflectance spectra of a series of clonazepam-containing batches is reported. Ten different formulations with fixed amount of clonazepam and varying proportions of excipients were analyzed at seven dissolution times and three different media. The percentages of dissolution of each sample were correlated with the NIR spectra of three tablets of each batch, through a multivariate analysis using the PLS regression algorithm. The squared correlation coefficients for the plots of percentages of dissolution from the equipment laboratory (dissolution apparatus and HPLC determination) versus the predicted values, in the leave-one-out cross-validation, varied from 0.80 to 0.92, indicating that the NIR diffuse reflectance spectroscopy method is an alternative, nondestructive tool for measurement of drug dissolution from tablets.


Assuntos
Preparações Farmacêuticas/química , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Análise Multivariada , Solubilidade
4.
J Chromatogr A ; 1075(1-2): 87-94, 2005 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-15974121

RESUMO

This work describes the preparation and characterization of six stationary phases for high-performance liquid chromatography (HPLC) obtained by deposition of poly(dimethylsiloxane) (PDMS) in HPLC silica particles, followed by immobilization using different processes (thermal treatments, thermal treatment + microwave irradiation, self-immobilization + gamma irradiation and self-immobilization + microwave irradiation). The chromatographic parameters of all the phases were evaluated with a mixture of test compounds having varied natures (acid, basic and neutral). The stability of one of these phases was evaluated in both a neutral mobile phase and a higher pH mobile phase used at an elevated temperature, with promising results.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Dimetilpolisiloxanos/química , Dióxido de Silício/química , Silicones/química , Concentração de Íons de Hidrogênio
5.
J Chromatogr A ; 987(1-2): 93-101, 2003 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-12613801

RESUMO

Several reversed-phase materials for high-performance liquid chromatography were obtained by deposition of poly(methyloctylsiloxane) (PMOS) on HPLC silica particles, followed by immobilization using different procedures. Each phase had characteristic physicochemical and chromatographic properties. The present work evaluates the stability of these phases with both neutral and basic mobile phases. All of the stationary phases were quite stable to neutral mobile phase, with less stability at higher pH. However, one thermally immobilized phase presented high stability even at an elevated temperature with a pH 10.0 mobile phase.


Assuntos
Cromatografia Líquida de Alta Pressão/instrumentação , Polímeros/química , Dióxido de Silício/química , Siloxanas/química , Microscopia Eletrônica de Varredura
6.
J Chromatogr A ; 948(1-2): 97-107, 2002 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-12831187

RESUMO

Five different reversed-phase materials for high-performance liquid chromatography were obtained by deposition of poly(methyloctylsiloxane) in HPLC silica particles, followed by immobilization using different processes: thermal treatment (120 or 220 degrees C for 4 h), irradiation with microwaves (495 W for 15 min), gamma radiation (dose of 80 kGy) and self-immobilization. These phases were characterized by gel permeation chromatography, percent carbon, 13C and 29Si solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The results show that the different immobilization processes produce different physical characteristics in the prepared phases.


Assuntos
Polímeros/química , Siloxanas/química , Isótopos de Carbono , Fenômenos Químicos , Físico-Química , Cromatografia em Gel , Cromatografia Líquida de Alta Pressão , Isótopos , Espectroscopia de Ressonância Magnética , Microscopia Eletrônica de Varredura , Silício , Dióxido de Silício , Espectrofotometria Infravermelho , Temperatura , Termogravimetria
7.
J Chromatogr A ; 948(1-2): 109-19, 2002 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-12831188

RESUMO

This work describes the chromatographic characterization of stationary phases prepared by deposition of poly(methyloctylsiloxane) (PMOS) on silica followed by immobilization using one of several different processes: thermal treatments (120 or 220 degrees C for 4 h), microwave irradiation (495 W for 15 min), gamma radiation (dose of 80 kGy) or self-immobilization. This evaluation was based on the chromatographic parameters of several test solutes. The stationary phases immobilized at 220 degrees C and which underwent self-immobilization were not appropriate for chromatographic use but the other immobilized phases presented chromatographic performances similar in most respects to a commercial phase (Rainin C8) while the peak characteristics of the basic probe were significantly better with these phases.


Assuntos
Polímeros/química , Siloxanas/química , Carbono/química , Fenômenos Químicos , Físico-Química , Cromatografia Líquida de Alta Pressão , Raios gama , Indicadores e Reagentes , Micro-Ondas , Dióxido de Silício/química , Solventes , Temperatura
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