Reproducibility of Crude Oil Spectra Obtained with Ultrahigh Resolution Mass Spectrometry

In this study, the reproducibility of crude oil analyzed with (+) atmospheric pressure photoionization ultrahigh resolution mass spectrometry was evaluated. Three sets of data were obtained at intervals of approximately a month for a span of three months. For each monthly data set, four oil samples were analyzed with four replicates in 1 day. The obtained 48 spectra were processed to examine the reproducibility of the class, double bond equivalent (DBE), and individual peak distributions. The reproducibility of the relative abundance was better than that of the absolute abundance. The distributions of major classes were consistent within the three sets with a less than 1% relative standard deviation (RSD). The DBE distribution for each data set was reproducible within 1% RSD, whereas the DBE distributions for the combined data sets had RSD values of 1%-6%. The RSD values were higher for minor components, suggesting that care must be taken in the use of minor values for quantitative or semiquantitative evaluation. The relative abundances of individual peaks in the major classes were reproducible within 1%-3% RSD for each data set. However, the RSD values of the combined data sets were over 10%, even for abundant peaks. The smaller RSD of the class and DBE distributions than that of individual peaks for combined data sets strongly suggest that variations observed from individuals were caused by random errors. The data presented in this study provide guidelines for evaluating petroleomic data obtained in the laboratory at different times or laboratories.