CHROMATOGRAPHIC AND SPECTROSCOPIC ANALYSIS OF MTBE AND TAME OCTANE IMPROVERS IN GASOLINES

Four analytical methods, namely combined gas chromatography-mass spectrometry, capillary gas chromatography, infrared spectroscopy and proton nuclear magnetic resonance spectroscopy, were used to determine the concentration of the octane improvers, methyl tertiary butyl ether (MTBE) and tertiary amyl methyl ether (TAME) in six commercially available unleaded gasolines. Combined gas chromatography-mass spectrometry and gas chromatography were both able to clearly resolve the ether compounds in the complex hydrocarbon mixtures, having minimum detection limits below 0.01 vol%. Infrared and low resolution (60 MHz) nuclear resonance spectroscopy could not resolve the individual ethers, and had minimum detection limits of about 0.5 vol% ether. The concentrations of ethers found in the different gasolines ranged from 0.1 to 6.4 vol% for MTBE and all less than 0.2 vol% for TAME.