Simultaneous flow analysis Fourier transform infrared determination of benzene, toluene, and methyl t-butyl ether in petrol

Abstract

A new procedure has been developed for the simultaneous flow analysis Fourier transform infrared (FTIR) determination of benzene, toluene and methyl t-butyl ether (MTBE) in real petrol samples. The method is based on the dilution of samples in hexane (1 + 9) and direct injection of 300 µl of the diluted samples into a 0.28 ml min^–1 carrier flow of hexane. First-order derivative absorbance measurements are carried out by FTIR, in the wavenumber range 1350–400 cm^–1. The three compounds studied were determined simultaneously in the same sample without additional sample preparation. Benzene was determined by measurement of the first order derivative (dA/d, where A is the absorbance, and , the wavenumber) between the peak at 678 cm^–1 and the valley at 672 cm^–1 with a dynamic range between 0.005 and 0.8% v/v, being established as the limit of detection for a probability level of 99.6%. Toluene was determined by measuring dA/d between 731 and 725 cm^–1, the dynamic range being from 0.01 to 2.0% v/v. Methyl t-butyl ether was determined by measuring dA/d between 1209 and 1201 cm^–1, providing a dynamic range between 0.035 and 2% v/v. The method can be applied to the direct analysis of petrol; the results obtained in the determination of the three compounds in real samples agree with those found by gas chromatography.