Potent mutagenic impurities in a commercial sample of 3-nitro-9-fluorenone

A commercial sample of 3-nitro-9-fluorenone was a potent mutagen in the Ames Salmonella assay, producing 1000 TA98 net revertants per plate at 0.76 microgram/plate without the presence of liver homogenates (-S9). After purification by high-pressure liquid chromatography (HPLC), 3-nitro-9-fluorenone was found to be at least 6 times less active than the parent sample. The commercial sample was fractionated by HPLC and the mutagenic impurity peaks collected and subjected to high-resolution mass spectrometry (HRMS). The mass spectra of 2 potent mutagenic fractions showed the principal molecular species to be a dinitrofluorenone and an acetamidomononitrofluorenone. Samples of synthetic 2,7-dinitro-9-fluorenone and 2-acetamido-3-nitro-9-fluorenone had mutagenic activities, HPLC retention times, and mass spectra characteristics similar to the mutagenic impurity fractions collected from the commercial sample.