Detection of the Engine Anti-Knock Additive Methylcyclopentadienyl Manganese Tricarbonyl (MMT) from Unleaded Gasoline in Soil by Diffuse Reflectance Infrared Fourier Transform Spectroscopy and Mass Spectrometry

Abstract

Soil samples were washed with dilute solutions of the toxic anti-knock fuel additive methylcyclopentadienyl manganese tricarbonyl (MMT) in hexanes and commercial unleaded gasoline. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was then used to detect the v(CO) modes of MMT, and subsequently ¹³CO-enriched MMT, in the soil samples. The presence of MMT in the soils was further confirmed by mass spectrometry. Concentrations corresponding to ∼10 ppm Mn in soil could be detected by DRIFTS of the dry samples, and, most interestingly, there was no evidence of significant MMT decomposition over a period of eight months. Apparently, MMT is stabilized by physisorption onto the soils. In the absence of such stabilization, however, MMT undergoes photolytic and thermal decomposition in a matter of minutes. These results suggest the possibility of longer-term environmental problems associated with gasoline spills containing MMT than was previously suspected.