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Gas chromatography (GC) is regarded as an essential separation method for the analysis of volatile compounds, and a wide variety of polymeric liquid-phases have been developed as the stationary phase. 1,2 Various deactivation and polymer-coating processes have been also proposed for the preparation of GC columns with good separation performance and stability. [3][4][5][6] In contrast to the successful applications and subsequent commercialization of these polymer-coated columns, such as wall-coated, support-coated and pellicular-coated, the reports for the fibrous polymer-packed stationary phases, however, have been limited, except for characterizing the surface of the fibers in inverse GC (IGC). 7,8 In general, the surface characteristics of the fiber have been analyzed with IGC technique by injecting the standard samples into a fiber-packed column and measuring the elution behavior. This characterization method is based on the observation of the specific interactions between the surface of the fibers and the standard solutes injected as the probes. Consequently, it is quite natural that a synthetic fiber can be employed as a separation medium in GC, if the fiber possesses both the thermal stability for the operation at an elevated temperature and the resistance to the gaseous chemical species through the column during the separation.In terms of the use of fibrous stationary phase in liquid phase separation methods, several applications have been reported. Kiso et al. introduced fibrous cellulose acetate (CA) stationary phase for the separation of alcohols 9 and polycyclic aromatic hydrocarbons (PAHs) 10 in microcolumn LC, and Jinno et al.reported the application of CA phase in capillary electrochromatography (CEC). 11,12 Recently, the possibility of the several synthetic fibers as the stationary phase in CEC 13 was also demonstrated. Although the separation efficiency of those columns was still not comparable with those of conventional particle-packed columns such as octadecylsilica (ODS) phase, and moreover, there were several limitations on the mobile phase composition and the packing density, still it has been clearly shown that the packed filaments could play the role as a stationary phase. Saito et al. have also reported the successful applications of fibrous polymeric material as an extraction medium for novel miniaturized sample preparations specially designed for the on-line coupling to microcolumn liquid phase separation methods. 14-22 On the basis of the above successful applications of fibrous materials as the stationary phase and the extraction medium, fiber-packed fused-silica capillaries have been introduced in our previous study for the separation of volatile compounds in GC. 23In this work, polymer coating onto the packed-filaments in a capillary was investigated using several conventional polymeric materials as the liquid-phase for capillary GC columns. As the fibrous material, Zylon ® [poly(p-phenylene-2,6-benzobisoxazole)] fiber ( Fig. 1) was employed, taking into account the heat resistance...

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.

Liquid chromatography (LC) is one of the most powerful techniques for the separation of various nonvolatile organic compounds. Nevertheless, the separation mechanism in LC has not yet been completely clarified. It is well known that the retention in LC is generated by a dispersion of the analyte between the mobile phase and the stationary phase. Especially, the intermolecular interaction of the analyte and the stationary phase ligand molecule plays a very important role during the retention process in LC. Therefore, the characterization of the surface structure of the stationary phase at the molecular level is very important.Octadecylsilica (ODS) has been most widely used as a stationary phase in LC because of its high separation ability. A number of attempts to understand the surface structure of the ODS stationary phase have been reported, in which spectroscopic techniques were used, such as nuclear magnetic resonance (NMR) spectroscopy, 1-7 Fourier-transform infrared spectroscopy (FT-IR), 5,8 Raman spectroscopy, 9-16 contact-angle measurements, 17 thermal analysis 5,18 and actual chromatographic methods. 19 Also, the influence of the temperature and bonding chemistry on the alkyl ligand conformation have also been well described in these reports.It is also experimentally known that a slight difference of the mobile-phase composition dramatically changes the LC retention. However, most of these reports are described based on the structure of the alkyl bonded silica surface in air, or in a pure solvent, such as water, methanol or acetonitrile. Pemberton et al. have recently studied the ODS ligand conformation systematically using Raman spectroscopy, [13][14][15][16] in which the bonding density, temperature, some kinds of solvents were considered to be the contributing factors. Sander et al. investigated the relationship between the alkyl ligand conformation and the mobile-phase composition using FT-IR spectroscopy. 8 Molecular dynamics (MD) simulations represent a powerful method to estimate the time-series structural changes of a multimolecular system, and are widely used in biochemistry to characterize the higher structures of biomolecules. Although this technique is used by only a limited number of researchers, because it needs computational resources, the advances of computer technologies have made it possible to use this technique on personal computers, and also to easily handle calculations for a huge molecular system, such as the stationary phase in LC. Some articles or reviews have been reported to characterize the stationary-phase ligand conformation using this type MD simulation. [20][21][22][23][24][25][26][27][28] Klatte and Beck applied MD simulations to molecular models that consisted of tethered and randomly placed n-alkane monolayers, and investigated the influence of the temperature, alkyl chain length and density of alkane molecules on the physical properties, such as the alkyl chain conformation and phase transition. 20,21 Although these results interpreted the behavior of the surface struct...

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.