FLOW-INJECTION DERIVATIVE FOURIER-TRANSFORM INFRARED DETERMINATION OF METHYL TERT-BUTYL ETHER IN GASOLINES

A procedure was developed for the flow-injection Fourier transform (FT) infrared spectrometric determination of methyl tert-butyl ether (MTBE) in unleaded gasolines. The method is based on the use of first-order derivative measurements in a flow system. The experimental procedure requires only the dilution of samples with hexane and the injection of a 320-mu l volume into a carrier flow of hexane. The FT-IR spectra are continuously recorded and the first-order derivative obtained. The flow-injection peaks are established from the variation with time of the dA/d (r) over bar values found between 1209 and 1201 cm(-1). Using a micro flow cell with a 0.117 mm path length and a carrier flow-rate of 0.45 ml min(-1), the limit of detection of the method corresponds to 0.035% (v/v). The recovery of MTBE varies from 98.2 to 102% and the relative standard deviation is 0.6% for samples containing 0.8% (v/v) MTBE. Results obtained in the analysis of real unleaded gasoline samples compare well with those found by gas chromatography.