Liquid chromatographic determination of base oil composition and content in lubricating oils containing dispersants of the polybutenylsuccinimide type

The determination of base oil composition and content in engine motor oils and in the fractions enriched in the polybutenylsuccinimide type dispersant which can be isolated from the lubricants are achieved through liquid chromatography. Strongly activated silica gel and anhydrous pentane are used associated with a backflush technique and refractometric detection. Calibration is done with Neutral 200 base oil whose composition is determined by mass spectrometry. It is shown that the treatment of multigrade motor oils through dialysis and classical liquid adsorption chromatography on a Florisil column leads to a dispersant without appreciable content of base oil.