Petroleum analysis using laser-induced acoustic desorption/chemical ionization mass spectrometry

PETR 170

Hilkka I Kenttämaa, hilkka@purdue.edu, Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2038
Laser-induced acoustic desorption (LIAD) allows the evaporation of saturated hydrocarbons as intact neutral molecules into mass spectrometers. The method is based on acoustic waves generated by light pulses from a Nd-Yag laser in a thin Ti foil. When the back side of the foil is irradiated, the acoustic waves desorb the hydrocarbon analyte from the opposite side of the foil. This technique, when coupled with chemical ionization (CI) in a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR), allows the simultaneous analysis of both the nonpolar and polar components in petroleum. Several metal ion complexes were employed to ionize the desorbed hydrocarbon molecules. The CpCoCO+• ion appears to be the best reagent ion since it forms a stable adduct, with no accompanying fragmentation, for all hydrocarbons studied. Results obtained from an examination of petroleum distillate samples and lube base stocks will be discussed.