Enhanced preconcentration of selected chlorofluorocarbons on multiwalled carbon nanotubes with polar functionalities.

Chromatographic monitoring of chlorofluorocarbons in air requires the preconcentration of these highly volatile species. In this paper, we present functionalized multiwalled carbon nanotubes as effective sorbents for a microtrap designed for chlorofluorocarbons preconcentration. Among the commercial carbons and carbon nanotubes studied, functionalization via carboxylation and propyl amine was most effective for dichlorofluoromethane and trichlorofluoromethane (Freon 11), which were selected as representative chlorofluorocarbons.

Methane preconcentration in a microtrap using multiwalled carbon nanotubes as sorbents.

The GC monitoring of green house gases is a challenging task because the concentration of organic species such as methane are relatively low (ppm to ppb) and their analysis requires some level of preconcentration. Since methane is highly volatile, it is not easily retained on conventional sorbents. In this paper we present multiwalled carbon nanotubes (MWNTs) as an effective sorbent for a microtrap designed for methane preconcentration.

Self-assembly of carbon nanotubes via ethanol chemical vapor deposition for the synthesis of gas chromatography columns.

The synthesis of the gas chromatography stationary phase by molecular self-assembly of carbon nanotubes (CNTs) via a novel ethanol chemical vapor deposition process is presented. A major advantage is that ethanol was found to be an excellent carbon source that generated highly pure multiwalled carbon nanotubes with very little nontubular carbon impurities. The nanotubes were not vertically aligned but lay flat out on the column surface in a randomly distributed configuration.

Modifying the sorption properties of multi-walled carbon nanotubes via covalent functionalization.

We demonstrate that the functionalization of carbon nanotubes dramatically alters their sorption characteristics. The effect of covalent functionalization of multiwalled carbon nanotubes (MWNTs) on the gas phase adsorption and desorption of polar and nonpolar organics is presented. Carboxylation and nitration led to the generation of polar functional groups on the nanotube surface.

Carbon nanotubes as sorbents for the gas phase preconcentration of semivolatile organics in a microtrap.

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.

Microtrapping characteristics of single and multi-walled carbon nanotubes.

Carbon nanotubes (CNTs) possess some highly desirable sorbent characteristics, which make them attractive for a variety of applications including micro-scale preconcentration. The main advantage of CNTs is that they are non-porous, thus eliminating the mass transfer resistance related to diffusion into pore structures. Their high aspects ratio leads to large specific capacity, consequently they have the potential to be the next generation high performance sorbent.

Development of continuous on-line purge and trap analysis.

An on-line purge and trap system for continuous monitoring of Volatile Organic Compounds (VOC) is presented. The purge chamber was designed for continuous extraction of VOC from water with nitrogen. The analytes were preconcentrated on a microtrap prior to analysis by GC with flame ionization detection.

Chromatography on self-assembled carbon nanotubes.

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.

Preconcentration of volatile organics on self-assembled, carbon nanotubes in a microtrap.

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.