Simplification of heavy matrices by liquid-liquid extraction: Part I -How to separate LMW, MMW and HMW compounds in maltene fractions of V, Ni and S compounds

Abstract : A method using liquid–liquid extractions has been developed for matrix simplification and evaluated by gel permeation chromatography coupled with inductively coupled plasma and mass spectrometry. In this method, maltenes were dissolved in n-heptane and extractions with methanol (MeOH), acetonitrile (ACN), and dimethylformamide (DMF) were performed. The extraction with ACN is more efficient than that with MeOH for the removal of compounds with low-molecular weights (LMW) containing V (our reference element) and more selective than that with DMF (with this solvent, compounds with LMW and medium-molecular weights (MMW) are extracted). Thus, a sequential extraction was performed by applying ACN to selectively remove LMW compounds, followed by extractions with DMF of the resulting maltene to separate the MMW compounds from the high-molecular weights (HMW) compounds remaining in the final remnant maltene. The results show, for the first time in the literature, that it is possible to separate the three V and Ni species of compounds present in maltenes based on their molecular weights (HMW, MMW, and LMW).