ASTM D5845 Standard Test Method for Determination of MTBE, ETBE, TAME, DIPE, Methanol, Ethanol and tert-Butanol in Gasoline by Infrared Spectroscopy
4. Summary of Test Method
4.1 A sample of gasoline is introduced into a liquid sample cell. A beam of infrared light is imaged through the sample onto a detector, and the detector response is determined. Regions of the infrared spectrum are selected for use in the analysis by either placing highly selective bandpass filters before or after the sample or mathematically selecting the regions after the whole spectrum is obtained. A multivariate mathematical analysis is carried out which converts the detector response for the selected regions in the spectrum of an unknown to a concentration for each component.
5. Significance and Use
5.1 Alcohols and ethers are added to gasoline to produce a reformulated lower emissions gasoline. Alcohols and ethers may also be added to gasoline to increase the octane number. Type and concentration of various oxygenates are specified and regulated to ensure acceptable commercial gasoline quality. Driveability, vapor pressure, phase separation, and evaporative emissions are some of the concerns associated with oxygenated fuels.
5.2 This test method is faster, simpler, less expensive and more portable than current methods.
5.3 This test method may be applicable for quality control in the production of gasoline.
5.4 This test method is not suitable for testing for compliance with federal regulations.
5.5 False positive readings for some of the samples tested in the round robin were sometimes observed. As only extreme base gasolines were tested in the round robin, no definitive statement can be made as to the expected frequency or magnitude of false positives expected in a wider range of base gasolines.
