“…Asphaltenes contain intrinsic paramagnetic species (paramagnetic centers, PCs) to be studied with electron paramagnetic resonance (EPR) techniques [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. Concentrations of PCs in asphaltenes can reach values of 10 22 spins per gram [ 13 ], meaning that every asphaltene molecule can be paramagnetic and that EPR is a suitable (valid) and unique tool for studies on PDS and PDS asphaltenes.…”