In the present work we describe a novel method for the isolation of the neutral N-containing fraction from crude oil by preparative liquid chromatography using thermally treated silica gel as stationary phase. The hydrocarbons are eluted in the first two fractions and the nitrogen compounds in the third fraction. The collected fractions are analyzed by HRGC-NPD. The method is shown to be very selective for the isolation of nitrogen compounds from the neutral fractions of crude oil.