Separation and identification of nitrogen compounds in coal-tar pitch

Chromatographic behaviour of 64 pure hydrocarbons and nitrogen compounds was verified by gel permeation chromatography. It was found that the elution volumes of almost all nitrogen compounds were higher than the elution volumes of aromatic hydrocarbons. This knowledge was used in the separation of nitrogen compounds from coal-tar pitch extracts. The obtained concentrates with a high nitrogen content were analysed by mass spectrometry to determine the mass representation of the individual groups of nitrogen compounds. The analysed concentrates contained carbazoles and their benzo-derivatives as the main nitrogen compounds.