DETERMINATION OF METHANOL AND METHYL TERT-BUTYL ETHER IN GASOLINE BY INFRARED-SPECTROSCOPY USING THE CIRCLE(R) CELL AND MULTIVARIATE CALIBRATION

The feasibility of predicting concentrations of methanol and methyl te rt-butyl ether (MTBE) in gasolines from the mid-infrared absorption sp ectra was investigated. The C-O bond stretching band region was relate d to these oxygenated compounds' levels with the aid of multivariate s tatistics. The sample spectra were taken with the use of a circular in ternal reflectance (CIRCLE(R)) cell. With the use of partial least-squ ares (PLS) regression a model with 18 samples was built and used to pr edict a set of 10 gasolines with good agreement. Two additional sample s prepared with other brands of gasoline were analyzed with the same m odel and no matrix effects were found.