Representative tar balls collected in two distinct years (2012 and 2014) in a beach along the State of Bahia, northeastern Brazil, were geochemically characterized in order to identify correlations between them and investigate potential sources. Terpanes and steranes biomarkers (detected by gas chromatography coupled to mass spectrometry, GC-MS), carbon stable isotope ratio (δ13C), Ni and V ratios and polar compounds by Fourier transform ion cyclotron resonance mass spectrometry using electrospray ionization in negative mode (ESI(-) FT-ICR MS) were evaluated. Three Brazilian oil samples from distinct sources were assessed as possible spill sources, comparing their results with the tar ball samples. Using chemometric techniques, it was verified correlation between the two set of tar ball samples, suggesting same source. However, no correlation with the oil samples was observed, with different geochemical profile among them. The heteroatom class distribution displayed severe degradation levels for tar balls and its seems that photo-oxidation and biodegradation processes were further relevant. Tar ball samples show multiple classes, most oxygenated, and with one sample showing considerable relative abundance of N1 class, suggesting it is from a more recent oil spill. In brief, our results suggest that the region, with very sensitive ecosystem, is possibly subjected to frequent spills from the same source.

Abstract The presence of acidic compounds as naphthenic acids in crude oil causes several problems for the petroleum industry, including corrosion in both upstream and downstream production processes. Based on this scenario, the main objective of this work was to investigate the removal of the acidic compound from two Brazilian heavy oils by adsorption processes using six potential adsorbents: powdered shale, activated carbon, bentonite, silica gel, powdered sandstone and powdered wood. These raw materials were previously characterized by conventional and surface analysis techniques, which show that they offer a good surface area and thermal stability. To evaluate the removal efficiency at the molecular level, the crude oil samples and the filtered oils were analyzed by negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry [ESI (-) FTICR MS]. The O2 class, which is related to the relatively high acidity of the samples, was the most abundant in both crude oil samples, moreover, this class was more retained by adsorbents. Silica gel, activated carbon and bentonite were the best adsorbents of acidic compounds from the tested oils, in agreement with their markedly higher surface area and porous volume. Additionally, a chromatographic analysis was performed and showed no changes in the oil profile.

Design of experiments (DOE) applied to mass spectrometry (MS), mainly focusing on the optimization of ionization techniques, has been applied to optimize experiments in order to provide the highest amount of information with the lowest number of experiments. However, DOE has not been used in petroleomics. For the first time, we applied DOE to optimize the main parameters associated with the crude oil analysis in a petroleomics approach. For the ionization technique, atmospheric pressure photoionization (APPI) has been selected and data were acquired in a high resolution (400,000 at m/z 400) and high mass accuracy (< 1 ppm) Fourier transform ion cyclotron resonance (FT-ICR) MS. Full and fractional two-level factorial designs were applied for the APPI(±) FT-ICR MS data set from two different crude oil samples with distinct physical and chemical characteristics. The standard ionization parameters that affect the MS responses of the crude oil analysis were optimized for both APPI(+)-MS and APPI(–)-MS. Such ionization parameters were then successfully applied to a crude oil and its saturated, aromatics, resin and asphaltene fractions, all with superior features of merit. Thus, the optimized APPI(±)-MS parameters should serve as reference and can be used as a guide for new studies in petroleomics.