Application of FT-ICR MS Equipped with Quadrupole Detection for Analysis of Crude Oil

Resolving power is a critical factor determining the quality of ultrahigh-resolving power mass spectra of crude oil. In this study, 7T Fourier-transform ion cyclotron mass spectrometry (FT-ICR MS), equipped with quadrupole detection, was applied and evaluated for crude oil analysis for the first time. Four spectra were obtained from two oil samples using two ionization methods. Resolving power of 1500000 was observed at m/z 400 with 4 s transient signal. Comparison with literature reports revealed that the achieved resolving power was comparable with or superior to those obtained from instruments using higher magnetic fields but without quadrupole detection. A total of 6000-10000 peaks with an S/N ratio of 3 or higher were observed from the obtained spectra and over 97% of the peaks could be assigned to appropriate chemical formulas with an error within 1 ppm. Double bond equivalents vs carbon number plots generated from the obtained data agreed well with those previously reported without quadrupole detection. Mass accuracy values of the assigned elemental formulas were examined and the average root-mean-square error was calculated to be only 160 ppb. Low unassignment rate of the observed peaks and strong agreement with previously reported results suggests that unwanted harmonics of reduced frequency are not significant for the data obtained with quadrupole detection. Overall, the data presented in this study show that FT-ICR MS equipped with quadrupole detection can be a powerful tool to examine complex mixtures like crude oil. To the best of our knowledge, this is the first paper reporting application of FT-ICR MS equipped with quadrupole detection for the oil analysis.