Determinação da precisão intermediária de um espectrômetro de massas de altíssima resolução e exatidão em análise de petróleos

Abstract

The ultrahigh resolution and mass accuracy from electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, ESI(±)FT-ICR MS, makes it possible to discern very close m/z (mass/charge ratio) signals. This differentiation capacity is reflected by the spectrometer's very high resolution. Studies using different complex matrices have been carried out. Crude oil presents difficulties in determining its compounds because its complexity. Part of the heteroatomic group (CcHhNnOoSs, where the subscripts correspond to carbon, hydrogen, nitrogen, oxygen and sulfur atoms numbers, respectively) are more susceptible to ionization and have greater reliability in determining their presence in crude oil. However, the repeated analysis of the same sample can generate different m/z values due the very high-resolution of the spectrometer. That reduce the accuracy of the analysis. Numerous aspects of the heavy crude oils have been studied in the last years and a great number of works in Petroleomics using ESI(±)FT-ICR MS are now available. Therefore, it is necessary to determine the analytical reliability of this equipment. The objective of this work is to estimate the intermediate precision of ESI(±)FT-ICR MS data from assigned compounds class, DBE distribution and the DBE versus CN plot for the most abundant classes (N[H] for ESI(+); and O2[H] and N[H] for ESI(-) for crude oil A and B, respectively). Furthermore, the PCA was used to determine the ionization mode (ESI(+) or ESI(-)) that presents the better intermediate precision of produced data. The ESI(+) ionization mode has better intermediate precision for Crude oil A and ESI(-) for Crude oil B. The DBE values presented lower intermediate precision limit values when compared to the assigned classes values. The classes and DBE values with intensities above 0.42% and 0.04%, respectively, are statistically present in the crude oil composition. ESI(-) presented lower Lclass (class limit statistically present) and LDBE (DBE limit statistically present)values (0.039% and 0.013%) than ESI(+) (0.42% and 0.04%) for the Crude oil A and Crude oil B, respectively. The PCA scores plot, coefficient of variation plot and intermediate precision limits indicate higher intermediate precision in the ESI(+) for Crude oil A and ESI(-) for Crude oil B.