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1.
J Sep Sci ; 28(17): 2413-8, 2005 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-16342809

RESUMO

The surface derivatization of poly(p-phenylene terephthalamide) fiber was studied. The obtained surface-derivatized filaments were packed into a fused-silica capillary to evaluate its surface characteristics by using GC. As the stationary phase for GC the surface-derivatized fibers showed higher retention for alkanes and alkylbenzenes than that with the untreated Kevlar fiber. The improvements on the retention power and the peak shape were observed on the benzyl-modified fibrous stationary phase. The derivatized fibrous materials were also evaluated as the extraction medium in fiber-in-tube SPE, and the effect of the surface modification on the extraction power was compared to the parent fiber. The results indicated that the modified fiber possessed a higher extraction power than the untreated fiber. Based on the facts, the successful modification of the fiber surface was estimated.

2.
Anal Bioanal Chem ; 382(3): 825-9, 2005 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-15933854

RESUMO

High-temperature gas chromatographic separation of several synthetic polymer mixtures with Dexsil-coated fiber-packed columns was studied. A bundle of heat-resistant filaments, Zylon, was longitudinally packed into a short metal capillary, followed by the conventional coating process with Dexsil 300 material. Prior to the packing process the metal capillary was deactivated by the formation of a silica layer. The typical size of the resulting column was 0.3-mm i.d., 0.5-mm o.d., 1-m length, and packed with about 170 filaments of the Dexsil-coated Zylon. The column temperature could be elevated up to 450 degrees C owing to the good thermal stability of the fiber, Dexsil coating, and metal capillary; furthermore, this allowed the separation of low-volatile compounds to be studied.


Assuntos
Polímeros/análise , Compostos de Silício/química , Temperatura , Cromatografia Gasosa/métodos , Estrutura Molecular , Oxazóis/química , Polímeros/química , Sensibilidade e Especificidade , Dióxido de Silício/química , Fatores de Tempo
3.
J Chromatogr Sci ; 43(10): 536-41, 2005.
Artigo em Inglês | MEDLINE | ID: mdl-16438796

RESUMO

The high-temperature gas chromatographic (GC) separation of several semivolatile compounds is studied with a short metal capillary column packed with fibrous material, having a polydimethylsiloxane coating thereon. Taking advantage of the excellent heat-resistance of the fiber and also the combination of the surface-deactivated metal capillary, a temperature-programmed separation up to 450 degrees C is successfully demonstrated for the separation of polymer standard samples. The average molecular weight of the commercially-available polymer standard samples for size exclusion chromatography (SEC) is estimated by high-temperature GC analysis and compared with the nominal value determined by a conventional SEC method. Although a slight deviation for the number-average molecular weight is observed between the GC and SEC analysis, the data for the weight-average molecular weight shows a good agreement in these methods. The results also suggest the future possibility of the fiber-packed metal capillary as a miniaturized GC column with an increased sample loading capacity.

4.
Anal Sci ; 20(2): 335-9, 2004 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15055962

RESUMO

Fibrous synthetic polymers have been introduced as the support material for packed capillaries in gas chromatography. The filaments of the polymers were packed longitudinally into a fused-silica capillary, followed by the conventional coating process for open-tubular capillaries. With various polysiloxane-based polymeric materials coated onto these filaments, it was demonstrated that the retentivity was significantly improved over conventional wall-coated capillaries of the same length and that the selectivity can be tuned by selecting different coating materials chosen for the various purposes. The results clearly showed the contribution of the fibrous support and the polymer-coating to the retention of analytes. They also showed the bright possibility for a novel usage of fine fibrous polymers as the support material, which can be combined with a newly-synthesized coating materials designed for particular separations.

5.
J Chromatogr A ; 1025(1): 27-32, 2004 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-14753667

RESUMO

Introducing fine polymeric filaments as the extraction medium, a miniaturized sample preparation technique for micro-column liquid chromatography (micro-LC) has been developed along with the investigation of a reproducible preparation scheme of the extraction capillary. The polymeric filaments were packed longitudinally into either a fused-silica capillary or a polyether ether ketone (PEEK) capillary of appropriate dimensions, and the extraction capillary was installed to the injection valve in micro-LC system. The number of packed filaments should be precisely counted before the packing process to make sure the reproducible preparation of the extraction capillary. With conventional stationary phase materials for open-tubular gas chromatography, polymeric coating to the surface of the filaments was also studied in order to further enhance the extraction performance and selectivity. Coated with the polymeric material suitable for the extraction of particular analyte, a dramatic improvement on the extraction power was obtained. The results suggest that the future possibility of novel tailored fibrous extraction medium with an appropriate coating on it, especially for the analysis of complex sample matrices.


Assuntos
Miniaturização , Cromatografia Líquida/instrumentação , Cromatografia Líquida/métodos , Microscopia Eletrônica de Varredura , Reprodutibilidade dos Testes
7.
J Pharm Biomed Anal ; 30(6): 1801-8, 2003 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-12485721

RESUMO

Polymer-coated fibrous material has been introduced as the extraction medium for a miniaturized sample preparation method being coupled with microcolumn liquid chromatography. The preconcentration and the subsequent liquid chromatographic separation of tricyclic antidepressants (TCAs) drugs, amitriptyline, imipramine, nortriptyline and desipramine, was carried out with the hyphenated system. Several basic experimental parameters, such as extraction and separation conditions, were investigated along with the applicability of the method for the analysis of biological fluids. The results clearly showed that the on-line coupled system could be a powerful tool for the analysis of complex mixtures in biological matrix without a large solvent consumption and specially designed instruments. The lowest limit of quantification was quite acceptable for the analysis of TCAs in clinical and forensic situations.


Assuntos
Polímeros/análise , Tecnologia Farmacêutica/métodos , Antidepressivos Tricíclicos/análise , Antidepressivos Tricíclicos/química , Cromatografia Líquida de Alta Pressão/métodos , Oxazóis/análise , Oxazóis/química , Polímeros/química , Tecnologia Farmacêutica/instrumentação
8.
Anal Chem ; 75(20): 5525-31, 2003 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-14710834

RESUMO

Synthetic polymer filaments have been introduced as the support material in packed capillary gas chromatography (GC). The filaments of the heat-resistant polymers, Zylon, Kevlar, Nomex, and Technora, were longitudinally packed into a short fused-silica capillary, followed by the conventional coating process for open-tubular GC columns. The separation of several test mixtures such as n-alkylbenzenes and n-alkanes was carried out with these polymer-coated fiber-packed capillary columns. With the coating by various polymeric materials on the surface of these filaments, the retentivity was significantly improved over the parent fiber-packed column (without polymer coating) as well as a conventional open-tubular capillary of the same length. The results demonstrated a good combination of Zylon as the support and poly(dimethylsiloxane)-based materials as the coating liquid-phase for the successful GC separation of n-alkanes and polycyclic aromatic hydrocarbons (PAHs), while successful applications for other separations such as poly(ethylene glycol) coating for the separation of alcohols were also obtained. From the results it has been suggested that the selectivity of the fiber-packed column could be tuned by selecting different coating materials, indicating the promising possibility for a novel usage of fine fibrous polymers as the support material that can be combined with newly synthesized coating materials specially designed for particular separations. Taking advantage of good thermal stability of the fibers, the column temperature could be elevated to higher than 350 degrees C with the combination of a short metallic capillary.

9.
J Chromatogr A ; 975(1): 105-12, 2002 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-12458751

RESUMO

Miniaturized sample preparation technique for complex sample matrices has been developed with a polymer-coated fibrous extraction medium. Several hundreds of fine fibrous materials were packed longitudinally into a fused-silica capillary followed by a polymeric coating on it to prepare the extraction capillary. The extraction capillary was installed in a liquid chromatograph as a sample loop of the injection valve. The on-line coupled sample preparation/separation system demonstrated a good validity for the analysis of phthalates in real river and wastewater samples. The lowest limits of quantification for several phthalates were less than 1 ng/ml. The effect of polymeric coating to the filaments on the extraction power was also investigated.


Assuntos
Polímeros , Cromatografia Líquida de Alta Pressão/métodos , Miniaturização , Sensibilidade e Especificidade
10.
Anal Bioanal Chem ; 373(1-2): 81-6, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-12012176

RESUMO

Miniaturized solid-phase extraction (SPE) has been developed and successfully employed for the determination of organic species in water samples by liquid chromatography (LC). The method is based on the concept of a microscale extraction technique using a fused-silica capillary column for gas chromatography (GC), so-called in-tube solid-phase microextraction (SPME). The extraction conditions, such as the extraction time and flow-rate for the extraction and desorption process, were investigated as well as the effect of the internal structure of the extraction capillary on the efficiency. By inserting a stainless steel wire into the extraction capillary to reduce the internal volume of the capillary with the same surface area of the coating, an improved extraction and pre-concentration effects were obtained. Further pre-concentration was accomplished by the extraction device with a novel fiber-in-tube configuration. The direct coupling of the extraction method with a LC system has made it possible to determine low levels of phthalates in water samples without high consumption of organic solvents. The system developed must have potential applications for the analysis of environmental and biological samples in aqueous sample matrices.


Assuntos
Ácidos Ftálicos/análise , Água/análise , Ação Capilar , Cromatografia Líquida/instrumentação , Cromatografia Líquida/métodos , Desenho de Equipamento , Miniaturização/instrumentação , Miniaturização/métodos , Ácidos Ftálicos/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos
11.
Anal Bioanal Chem ; 372(1): 164-8, 2002 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11939188

RESUMO

Miniaturized fiber-in-tube solid-phase extraction (fiber-in-tube SPE) has been developed as a solventless sample preconcentration technique for microcolumn liquid-phase separation methods. Short capillaries packed with polymer filaments were employed as the extraction tube and the preconcentration power for phthalates in aqueous solutions was studied. On the basis of the successful on-line coupling of this preconcentration method with liquid chromatography (LC), a more miniaturized extraction cartridge, which is installed in the rotor of the micro-injector, has been developed. With a modified commercially available valve, on-line coupling of this sample preconcentration method to capillary electrochromatography (CEC) was also investigated.

12.
Anal Sci ; 18(1): 7-17, 2002 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-11817732

RESUMO

Miniaturized extraction and separation media have been successfully developed from precisely controlled technologies. In this article, recent developments in these high performance analytical methods, such as miniaturized sample preparation methods and the coupling of these techniques with microscale separation systems, have been reviewed, along with some applications to environmental and biological analysis. The advantage of the miniaturization is not only for the environmental compatibility but also for the developments of the high performance analytical systems. Down-sizing also makes it possible to investigate and introduce various compounds and materials as novel media (such as tailor-made materials and devices) in separation science. As a typical example of the novel miniaturized sample preparation system, the applications of fibrous materials for microcolumn liquid-phase separation methods are described.


Assuntos
Monitoramento Ambiental/métodos , Preparações Farmacêuticas/isolamento & purificação , Miniaturização/métodos , Preparações Farmacêuticas/análise , Sensibilidade e Especificidade
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