A determination method for N-methyldidecane-1-ylamine in environmental water by liquid chromatography tandem-mass spectrometry (LC/MS/MS) was developed. The method detection limit (MDL) and method quantification limit (MQL) were 0.00055 µg/L and 0.0014 µg/L, respectively. The average recoveries from river water and sea water were 98% with a relative standard deviation (RSD) of 6.2% and 85% with a RSD of 2.4%, respectively. The concentrations of N-methyldidecane-1-ylamine in rivers and five locations in northern Ise Bay in Nagoya City were below the MDL. The concentrations of N-methyldidecane-1-ylamine added to river water and sea water were almost stable over a three-day preservation period, while the concentrations decreased by 50% after seven days of preservation. In order to discuss the mechanism underlying the aforesaid decrease, the preserved solutions were analyzed by liquid chromatography/high-resolution mass spectrometry. Two compounds were identified as the oxidation products of N-methyldidecane-1-ylamine in the preserved solutions.

The present study was conducted on an occasion that the unpleasant odor was found in a marine aquaculture fish served in restaurant. The identification of odor compound was conducted using Gas Chromatography-Olfactometry (GC-O) and odor compounds database. GC-O analysis and database search could estimate the odor compound as 2-methylisoborneol (2-MIB). No previous research has been reported that 2-MIB was detected from marine fish because 2-MIB is the compound produced by a type of algae and actinomycetes in fresh water pond and lake. A likely reason for 2-MIB detection from marine fish was that the water filtration device in aquarium which kept the fish was contaminated by 2-MIB. This case was accidental food contamination by natural chemicals analogous to mycotoxins.