Detection of TNT vapours with the Pico-1 Nose

The problem of sensing military grade TNT is addressed with the Pico-1 Electronic Nose developed at the Brescia University. Pico-1 is based on semiconductor thin films and uses static headspace sampling. TNT in air, sand and soil substrates is measured. All measurements were carried out against their respective substrates. It is found out that the TNT detection can be easily performed in two steps. First a Multilayer Perceptron (MLP), using as inputs the features extracted from the responses of three SnO2 catalyzed sensors, distinguishes between the different substrate types, irrespectively of the presence of TNT. Having determined the substrate, two bare sensors suffice to check if TNT is present: PCA plots show that the measurements quite clearly form two clusters (TNT absent/present). Further, regarding the detection limit of single sensors for TNT in air, measurements performed at room temperature (4 ppb of saturated TNT concentration) showed that there is a 10% variation of the sensor response (with respect to air) when TNT is present.