Element speciation analysis of petroleum and related materials

Challenges to identification, characterisation and determination of element species in crude and residual oils, oil fractions, natural gas and gas condensates, and related products are presented. The principal elements of concern include vanadium, nickel, sulfur, mercury and arsenic. The state-of-the-art of analytical methods available for element speciation in petroleum-related matrices is discussed with particular attention given to chromatography with plasma source atomic spectrometric detection. Methods for fractionation of metal species prior to chromatography are critically reviewed. Analysis for metal species by gas (GC) and liquid chromatography (LC) using different separation mechanisms (size-exclusion, adsorption, ion-exchange, reversed and normal-phase) and element selective detection are discussed. The potential and limitations of LC-ICP AES, LC-ICP MS, GC-MIP AES and GC-ICP MS are highlighted in the context of techniques allowing a direct insight into the metal coordination in petroleum-related samples, such as X-ray absorption spectroscopy (XAS), electron paramagnetic resonance (EPR) and molecular mass spectrometry (using laser desorption, electrospray and chemical ionization).