Journal of Chromatography A, 1216 (2009) 6517–6521 Contents lists available at ScienceDirect Journal of Chromatography A journal homepage: www.elsevier.com/locate/chroma Carbon nanotube field-effect transistor detector associated to gas chromatography for speciation of benzene, toluene, ethylbenzene, (o-, m- and p-)xylene Lurdes I.B. Silva a,∗ , Filipe D.P. Ferreira a,b , Teresa A.P. Rocha-Santos a , A.C. Duarte b a ISEIT/Viseu - Instituto Piaget, Estrada do Alto do Gaio, Galifonge, 3515-776 Lordosa, Viseu, Portugal b CESAM & Department of Chemistry, University of Aveiro, 3810-193 Aveiro, Portugal article info Article history: Received 24 April 2009 Received in revised form 22 July 2009 Accepted 27 July 2009 Available online 3 August 2009 Keywords: Carbon nanotubes BTEX detection Nanodetector Field-effect transistor abstract An analytical methodology based on a field-effect transistor detector using carbon nanotubes (NTFET) coupled to a gas chromatograph has been developed for the speciation of the following aromatic com- pounds: benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene (BTEX). This methodology combines the proven separation capability of gas chromatography (GC) with the potential for detection of a NTFET. The developed analyzer shows a high and stable analytical response upon repeated analysis of BTEX during 4 weeks, with detection limit less than 4 g/L. The GC–NTFET system also shows a great suit- ability for actual monitoring of indoor atmospheres and no significant difference was observed between the results obtained by the developed analyzer and a more classical analytical methodology, namely gas chromatography–flame ionization detection (GC–FID). © 2009 Published by Elsevier B.V. 1. Introduction Carbon nanotubes (CNTs) have been widely used as nanostruc- tured materials in both forms of single-walled [1] and multi-walled [2] in many applications in electronics, optics and other fields of nanotechnology and nanoscience, due to their unique, novel and useful physical characteristics. CNTs have gained an increase in attention when used in many nanoscale devices [3,4], includ- ing field-effect transistors [5] for environmental monitoring and biosensing. The robust and inert carbon nanotube structure, nanosized mor- phology and high surface area, make CNTs potentially useful for highly sensitive and reversible gas adsorption, as well as gas sen- sor materials with excellent sensitivities and fast responses [6–10]. In this area, single-walled carbon nanotubes (SWCNTs) have been successfully applied as sensing nanomaterial in gas sensors devel- opment, especially in field-effect transistors (FETs) based sensors [11–16]. The potential use of SWCNTs in chemical sensors has been demonstrated possibly for the first time by Kong et al. [6] when exposing them to electron withdrawing or donating gaseous molecules (e.g. NO 2 and NH 3 , respectively) dramatically increases or decreases the electrical resistance of the SWCNTs in the tran- sistor scheme. The NTFETs analytical devices are based on fact ∗ Corresponding author. Tel.: +351 232 910 100; fax: +351 232 910 183. E-mail address: lisilva@ua.pt (L.I.B. Silva). that carbon nanotubes are extremely sensitive to the effects of charge transfer and chemical doping by various molecules. The electronic structures of target molecules near the semiconducting nanotubes cause measurable changes to the nanotubes’ electri- cal conductivity. The carbon nanotubes can also be functionalized with molecules enabling the specific interaction with target chem- icals, thus improving the selectivity of CNTs based devices [17]. The NTFETs analyzers are a promising platform for environmental pollutants monitoring with the required analytical features (sen- sitivity, stability and reproducibility) at low cost. These devices have also attracted increasing interest, due to their compatibility with well-developed microelectronic fabrication techniques which make possible a high degree of miniaturization [18]. This paper aimed at the development of a NTFET detector cou- pled to a gas chromatograph (GC) for detection of the following aromatic compounds: benzene, toluene, ethylbenzene, m-xylene, p-xylene and o-xylene (BTEX), which constitute an important class of indoor air pollutants since even at a trace amounts they show a high potential hazard to human health due to their carcinogenic nature. 2. Experimental Fig. 1 shows the experimental apparatus used for the newly pro- posed method, highlighting a detailed view of the NTFET detector. The GC component is constituted by a capillary column (fused silica-Supelcowax, 30 m × 0.32 mm ID × 1.0 m, Cat No. 24211, 0021-9673/$ – see front matter © 2009 Published by Elsevier B.V. doi:10.1016/j.chroma.2009.07.060