Analysis of nitro musk compounds and their amino metabolites in liquid sewage sludges using NMR and mass spectrometry

A method using HRGC ion trap MS/MS for measuring simultaneously amino metabolites and the parent compounds, the nitro musks, an important group of organic fragrance components found in sewage sludges, was developed. The monoamino metabolites were synthesized and characterized by 1H/13C NMR and mass spectroscopy. Among the nitro musks, musk ketone was the major compound, found at an average concentration of 5 microg/kg of dry mass (dm) whereas musk xylene was detected in only one sample (30 microg/kg dm). Three amino metabolites were identified, namely, 1-tert-butyl-3,5-dimethyl-4-amino-2,6-dinitrobenzene, 1,1,3,3,5-pentamethyl-4-nitro-6-aminoindane, and 4-acetyl-1-tert-butyl-3,5-dimethyl-2-nitro-6-aminobenzene, the corresponding reduction products of the nitro musks xylene, moskene, and ketone. These metabolites were present in partly higher concentrations in the sludges than the corresponding nitro musk compounds. Musk xylene and musk moskene were mainly found as their monoamino metabolites, underlining the importance of anaerobic reduction processes in the sewage treatment plant.