Vapour generation Fourier transform infrared spectrometric determination of benzene, toluene and methyl tert.-butyl ether in gasolines

A simple and fast procedure has been developed for the direct and simultaneous determination by Fourier transform infrared (FTIR) spectrometry of benzene, toluene and methyl tert.-butyl ether (MTBE) in gasoline samples. The method is based on the injection of 1 mu l of gasoline into an electrically heated Pyrex glass reactor in which the sample is volatilized at 90 degrees C. The vapour generated is transported by means of a nitrogen carrier flow of 400 ml min(-1) inside an IR multiple pass gas cell and the spectrum in the mid-IR region is registered between 1600 and 500 cm(-1) as a function of time. The flow injection recordings obtained for the LR bands between 671-675 cm(-1), 727-731 cm(-1), and 1210-1214 cm(-1) were employed for the determination of benzene, toluene and MTBE respectively, using different criteria for establishing the baseline correction. Results obtained in the analysis of commercial samples of gasoline agree with those found by gas chromatography and another FTIR reference procedure.