Stationary phases that provide high resolutions and are stable at high temperatures are of significant importance in chromatographic analysis. Carbon nanotubes (CNTs) are known to have high thermal and mechanical stability and have the potential to be high-performance separation media that utilize the nanoscale interactions. Here, we report the first application of self-assembled CNTs in long capillary tubes for the development of gas chromatography columns. A film of CNTs was deposited by chemical vapor deposition (CVD) to form the stationary phase in the open tubular format. High-resolution separation of a number of compounds has been achieved. Altering the CVD conditions can vary the thickness and the morphology of the CNT film, which opens the possibility of selectivity tuning. The ability to fabricate long tubes coated with CNTs can be readily employed in other gas- and liquid-phase separations as well.

This paper reports the self-assembly of carbon nanotubes (CNTs) on the inside wall of a steel capillary to fabricate a microtrap for the adsorption/desorption of trace organics. The microtrap functioned as a nanoconcentrator and an injector for gas chromatography (GC). The CNTs were deposited as a thin film by catalytic chemical vapor deposition from either CO or C2H4 as the precursor. The sorbent film synthesized from C2H4-CVD (CVD = chemical vapor deposition) had higher CNT density and thus was a stronger sorbent. In general, the CNT microtraps showed high-capacity adsorption and fast quantitative desorption, and the process showed excellent precision. This study demonstrates that CNT films can be deposited quite easily in a steel capillary for use in different analytical applications, and CNT films can perform as efficiently as packed-bed carbon sorbents.

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In this paper we present the application of carbon nanotubes as unique sorbents for the fabrication of microtraps for the nanoscale adsorption/desorption of relatively large semivolatile organic molecules. The microtrap application requires high adsorption capacity as well as easy desorbability; the latter being critical for semivolatile compounds. The sorbent characteristics of single and multiwalled carbon nanotubes for gas phase adsorption/desorption of several compounds has been studied. The nonporous nature of carbon nanotubes (CNTs) eliminates the mass transfer resistance related to diffusion into pore structures, thus allowing easy desorbability. At the same time, their high aspects ratios lead to large breakthrough volumes. As compared to a commercial sorbent Carbopack, the breakthrough volume was as much as an order of magnitude higher in the CNTs, while the rate of desorption measured as the peak width at half height of the desorption band was eight times lower. The trapping and desorption characteristics of single and multi walled nanotubes were found to be comparable. We also found that the presence of disordered carbon impurities, which could be removed by controlled oxidative annealing could greatly degrade the performance of CNTs.