Comparing the Intermediate Precision in Petroleomics by Ultrahigh-Resolution Mass Spectrometry

The mass analyzers, Ion Cyclotron Resonance (ICR) and Orbitrap, both integrated to Fourier Transform (FT), are widely used in research in petroleomics for providing results with ultrahigh resolution and mass accuracy. The Electrospray Ionization (ESI) source is often used to analyze oils at the molecular level when coupled to FT-ICR and Orbitrap. In this work, the statistical comparison was based on the molecular formula assignments by Composer software from the mass spectra data obtained by four different crude oils (n = 4), analyzed in triplicate (n = 3) for 7 consecutive days (n = 7), using ESI(±) (n = 2) coupled to FT-ICR MS and Orbitrap MS (n = 2). This resulted in 336 different mass spectra. The coefficient of variation (CV), confidence interval (CI), intermediate precision limit, and Principal Component Analysis (PCA) were studied from the means of the assignments of compound classes, double bond equivalent (DBE) distribution, and carbon number (CN) versus DBE plot by the processing of mass spectra data. The results confirmed a greater statistical certainty for ESI(±)­FT-ICR MS about ESI(±)­Orbitrap MS, which are in agreement with the PCA scores plot that showed low variation in the replicates obtained for the ESI(±)­FT-ICR MS analyses when compared to ESI(±)­Orbitrap MS. Also, a greater statistical certainty was noted for the DBE assignments [(0.06 ± 0.03)% for ESI(±)­FT-ICR MS and (0.18 ± 0.11)% for ESI(±)­Orbitrap MS] and compound classes [(0.21 ± 0.10)% for ESI(±)­FT-ICR MS and (3.22 ± 0.65)% for ESI(±)­Orbitrap MS]. Also, the PCA and statistical parameters indicated that ESI(−) showed higher intermediate precision when compared to ESI­(+).