Abstract The potential of polar compound compositions from electrospray ionization ultra-high resolution mass spectrometry (FT-ICR-MS) to characterize petroleum fluids as well as petroleum system processes is shown in the example of the Eagle Ford Formation in Texas, USA. A set of six black oil and nine source-rock bitumen samples is investigated with respect to its organic nitrogen-, sulphur- and oxygen-compound inventory in order to assess maturity, depositional environment, lithofacies and retention and migration behaviour. Compared to conventional geochemical tools based on molecular parameters from gas chromatographic analyses, FT-ICR-MS enables a maturity assessment from immature to late mature stage, which is barely influenced by source or depositional environment. Due to the increased molecular mass and polarity range of its target compounds, FT-ICR-MS is the most convincing tool to describe the retention and fractionation of polar compounds in a petroleum system.