Molecular Comparison of Solid-Phase Extraction and Liquid/Liquid Extraction of Water-Soluble Petroleum Compounds Produced through Photodegradation and Biodegradation by FT-ICR Mass Spectrometry

We apply two widely used extraction techniques, liquid/liquid extraction and solid-phase extraction with styrene-divinylbenzene polymer with a proprietary nonpolar surface priority pollutant (PPL) to water-soluble compounds generated through photodegradation and biodegradation of petroleum. We compare the molecular composition of bio- and photodegraded water-soluble organic (WSO) acids by 21 T negative-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). We highlight the compositional differences between the two extraction techniques for abiotic and biotic degradation processes and identify known toxic species (naphthenic acids) produced through hydrocarbon biodegradation identified by liquid/liquid extraction (LLE) that are not detected with solid-phase extraction (SPE) of the same sample. Photodegraded WSO compounds extracted by SPE-PPL correspond to species with higher O/C ratio and carbon number compared to LLE extracted compounds. Naphthenic acids, a recalcitrant class of nonaromatic carboxylic acids and known acute toxicants formed through biodegradation of oil, are detected in LLE extracts (up to C30 and double-bond equivalents, DBE < 3) but are not detected in SPE-PPL extracts. This suggests that LLE and SPE-PPL retain different water-soluble oil species based on the dominant type of oil weathering process.