SIMULTANEOUS FLOW-ANALYSIS FOURIER-TRANSFORM INFRARED DETERMINATION OF BENZENE, TOLUENE, AND METHYL T-BUTYL ETHER IN PETROL

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 mu l of the diluted samples into a 0.28 ml min(-1) carrier how 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 ($) over bar v, where A is the absorbance, and ($) over bar v, 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 ($) over bar v between 731 and 725 cm(-1), the dynamic range being from 0.01 to 2.0% v/v. R;Iethyl t-butyl ether was determined by measuring dA/d ($) over bar v 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.