High performance liquid chromatography hyphenated by flow injection to inductively coupled plasma mass spectrometry (HPLC–FI–ICP-MS) was used to investigate vanadium linked to porphyrins present in fractions of crude oil. First, the crude oil sample was submitted to fractionation by preparative liquid chromatography with UV-Vis detection, at the porphyrin Soret band wavelength (400 nm). The obtained porphyrin fractions were then separated in a 250 mm single column, in the HPLC, and eluted with different mobile phases, methanol or methanol:toluene (80:20; v:v). The quantification of V-porphyrins in the fractions eluted from HPLC was carried out by online measuring the 51V isotope in the ICP-MS, against vanadyl octaethylporphine standard solutions (VO-OEP), prepared in the same solvent as the mobile phase, and injected post-column directly into the plasma. A 20 micrograms L−1 Ge in methanol was used as internal standard for minimizing non-spectral interference, such as short-term variations due to injection. The mathematical treatment of the signal based on Fast Fourier Transform (FFT) smoothing algorithm was employed to improve the precision. The concentrations of V as V-porphyrins were between 2.7 and 11 mg kg−1 in the fractions, which were close to the total concentration of V in the fractions of the studied crude oil.