Determination of Ethanol in Gasoline by FT-IR Spectroscopy

Ethanol is the primary oxygenate in gasoline in the United States. Gasoline containing various percentages of ethanol is readily available in the market place. A laboratory experiment has been developed in which the percentage of ethanol in hexanes can easily be determined using the O-H and alkane C-H absorptions in an infrared spectrum. Standard solutions of ethanol mixed with hexanes are prepared, and their infrared spectra collected. The areas under the O-H and C-H absorptions are used to prepare a standard curve, which is used to determine the percentage of ethanol. Results for the analysis of ethanol in gasoline from this model ethanol/hexanes calibration system compare favorably to advertised values, as well as to values determined by water extraction.