Characterization of Naphthenic Acids in Thermally Degraded Petroleum by ESI(−)-FT-ICR MS and 1H NMR after Solid-Phase Extraction and Liquid/Liquid Extraction

Naphthenic acids (NAs), present in a typical Brazilian acid crude oil and its thermal degradation products, were investigated using two separation methodologies: solid-phase extraction (SPE) and liquid–liquid extraction (LLE). Fractions produced were characterized by proton nuclear magnetic resonance spectroscopy (1H NMR) and negative-ion-mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI(−)-FT-ICR MS). Of the NAs extraction methods studied, SPE was more efficient than LLE. Further, ESI(−)-FT-ICR MS results showed that the SPE method with eluent phase variation allowed for the detection of a larger amplitude of NAs compounds (m/z200–1200), reducing the occurrence of ion suppression on the NAs of higher average molecular weight (Mw) distribution. It was noted that the aromaticity or double bond equivalent (DBE) of these produced collective fractions as well as their Mwvalues increased as a function of the polarity of the extraction system (DCM →