Identification and Quantitation of Oxygenates in Gasoline Ampules Using Fourier Transform Near-Infrared and Fourier Transform Raman Spectroscopy

Abstract

Oxygenated fuels are gasolines blended with alcohol or ether additives. The U.S. National Institute of Standards and Technology (NIST) provides eight oxygenated gasoline standard reference materials (SRMs) each containing one of four oxygenates at both the 2.0% and 2.7% oxygen mass fraction levels in 20-mL sealed glass ampules. In this study, FT near-IR and FT Raman spectroscopic methods were investigated to nondestructively identify and quantitate the oxygenate concentration in ampules of SRM gasoline. The samples contained any one of the four SRM oxygenates, MTBE, ETBE, TAME, or ETOH. In addition, dual-oxygenate mixtures were examined. The multivariate, statistical calibration technique, partial least-squares, was employed for both near-IR and Raman data to obtain calibration methods to predict the mass fraction of the oxygenate in these gasoline samples. Both spectroscopic techniques were able to unambiguously identify the oxygen additives and quantitate oxygen concentration to an accuracy within 0.1% oxygen mass fraction.