Effects of nitrosation on the chemical composition and epidermal carcinogenicity of the nitrogen-rich fraction of a high-boiling coal liquid.

Abstract

An 800-850 degrees F solvent-refined coal-II liquid was fractionated into chemical classes to obtain the aliphatic hydrocarbons, polycyclic aromatic hydrocarbons (PAH), nitrogen-containing polycyclic aromatic compounds (NPAC), and hydroxy-substituted PAH (hydroxy-PAH). The isolated NPAC fraction was refractionated by chemical class both before and after undergoing a nitrosation reaction. The nitrosated and non-nitrosated refractionated NPAC fractions were further subfractionated into secondary amine (pyrroles), primary amine-enriched (amino-PAH), and tertiary amine (azaarene) classes. The PAH and hydroxy-PAH composition of the NPAC fraction increased upon nitrosation, whereas the amino-PAH fraction composition decreased upon nitrosation. Nitrosation of standards indicated the amino-PAH compounds reacted to form parent PAH, chloro-substituted PAH, and methoxy-substituted PAH when analyzed by high-resolution gas chromatography (GC) and GC/mass spectrometry (MS). Some easily oxidized PAH compounds reacted to form ketones and quinones. All other standard reference compounds, chosen to be representative of the major chemical classes of compounds present in coal liquefaction materials, were unchanged by the nitrosation reaction. The amino-PAH of the nitrosated NPAC fraction reacted to form parent and some chloro-substituted PAH when analyzed by low-voltage direct-probe MS in addition to the methods given above. Epidermal carcinogenesis studies with the PAH, NPAC, nitrosated NPAC, and hydroxy-PAH fractions isolated from the 800-850 degrees F coal liquid indicated the PAH and NPAC were the most important determiners of skin carcinogenesis, with the PAH giving a higher response than the NPAC. The tumorigenicity of the NPAC was drastically reduced by nitrosation, probably due to the destruction of the amino-PAH upon nitrosation.