NEW METHOD for the PRODUCTION of BTX STANDARD GAS SAMPLING with SPME As An Alternative to AIR Monitoring, Advantages and Limitations

Benzene, Toluene and Xylenes (BTX) are extremely volatile solvents, and therefore play an important role in atmospheric chemistry, being precursors in the tropospheric ozone formation. In this work a BTX new standard gas was produced in nitrogen for stagnant systems. The aim of this work is to develop a new method, simple and cheaper, to quantify and monitor BTX in air using solid phase micro-extraction/gas chromatography/mass spectrometry (SPME/CG/MS). The features of the calibration method proposed are presented in this article. SPME sampling was carried out under non-equilibrium conditions using a Carboxen/PDMS fiber exposed for 10 minutes to standard gas mixtures. Sampling time and gas concentration have been studied in order to verify the affect on the extraction process of the gases. The results of the calibration curve of the BTX multicomponent system studied have shown a linear and a nonlinear range. In the non-linear range, it is remarkable the effect of competition by selective adsorption with the following affinity order p-xylene> toluene> benzene. This behavior represents a limitation of the method, however being in accordance with some references and it shows promissing results.