Fate of N-containing polycyclic aromatic compounds and microbial mutagenicity in SRC-II products on storage

Abstract

Samples of a solvent refined coal II fuel oil blend were stored at 100 °C in air for 16 weeks, at room temperature, both diluted in methylene chloride and undiluted, for one year, and under nitrogen, diluted in methylene chloride, for three years. These conditions were chosen to increase the rates of the reactions producing chemical changes, and to mimic worst case storage conditions for samples subjected to microbial mutagenicity and other bioassay test systems. The samples kept at 100 °C were fractionated by neutral alumina column chromatography to obtain nitrogen-containing polycyclic aromatic compound fraction to determine the fate of nitrogen species on storage under these conditions. The test samples after storage were compared by high resolution gas chromatography to samples which had been stored at −20 °C under nitrogen for the same length of time. The amino-substituted polycyclic aromatic hydrocarbons and indole concentrations were found to have significantly decreased in the materials stored at 100 °C. There was a corresponding significant decrease in the mutagenicity of these samples as measured in a histidine reversion bioassay. The samples stored at room temperature and diluted at −20 °C also showed significant decreases in microbial mutagenicity believed to be caused by a decrease in amino-PAH concentration after storage. A sample of SRC-II heavy distillate was sub-sampled from varying levels of an undisturbed 60 dm 3 Teflon-lined stainless steel drum after storage for four years at 4 °C under nitrogen. A sludge had formed on the bottom of the container with the major chemical constituent being carbazole. Microbial mutagenicity analysis showed no significant mutagenicity differences in the samples taken from varying levels of the drum.