Mesoporous silica nanoparticle film as sorbent for in situ and real-time monitoring of volatile BTX (benzene, toluene and xylenes).

A strategy is described for the real time and selective monitoring of benzene, toluene and xylenes (BTX) in air. Rapid preconcentration and recovery have been achieved with films made of mesoporous silica nanoparticles assembled on a quartz plate. The resulting nanoparticle films displayed high transmittance and allowed the detection of toluene up to 1 ppm within a minute and a regeneration of the sensor in less than 30 s. The sensor response increased while increasing the concentration of benzene (detection at 252 nm), toluene (detection at 267 nm) or p-xylene (detection at 274 nm) in the polluted air from 1 to 100 ppm. The order of sensitivity, i.e. p-xylene > toluene > benzene, was correlated with their respective molar extinction coefficients. The BTX adsorption on mesoporous silica nanoparticle films has been analyzed with the Freundlich adsorption model. The repeatability of the detection was good in intraday (2%) and extra-day (4%) experiments with a given sensor. The ability to detect toluene in the presence of volatile compounds often encountered in working environments (i.e., methyl ethyl ketone, ethanol, acetone and cyclohexane) has been shown. The introduction of a gas dryer before the measurement cell allowed application of the sensor in humid atmosphere. This sensor could be used to alert if permissible values of exposure to toluene and xylenes have been reached during work. [ABSTRACT FROM AUTHOR]