Determination of N-nitrosamines in processed meats by liquid extraction combined with gas chromatography-methanol chemical ionisation/mass spectrometry

摘要

A simple, accessible and reproducible method was developed and validated as an alternative for the determination of nine volatile N-nitrosamines (NAs) in meat products, using a low volume of organic solvent and without requiring specific apparatus, offering the possibility of practical implementation in routine laboratories. The NAs were extracted with dichloromethane followed by a clean-up with phosphate buffer solution (pH 7.0). The extracts were analysed by gas chromatography-chemical ionisation/mass spectrometry (GC-CI/MS) in positive-ion mode using methanol as reagent. Limits of detection and quantification, recovery and reproducibility were determined for all NAs (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosopyrrolidine, N-nitrosodipropylamine, N-nitrosomorpholine, N-nitrosopiperidine, N-nitrosodibutylamine and N-nitrosodiphenylamine). Satisfactory sensitivity and selectivity were obtained even without concentrating the extract by solvent evaporation, avoiding the loss of the nine NAs studied. Limits of detection ranged from 0.15 to 0.37 μg kg~(-1), whereas limits of quantification ranged from 0.50 to 1.24 μg kg~(-1). Recoveries calculated in cooked ham that had been spiked at 10 and 100 μg kg~(-1) were found to be between 70% and 114% with an average relative standard deviation of 13.2%. The method was successfully used to analyse five samples of processed meat products on the day of purchase and 7 days later (after storage at 4℃). The most abundant NAs found in the analysed products were N-nitrosodipropylamine and N-nitrosopiperidine, which ranged from 1.75 to 34.75 μg kg~(-1) and from 1.50 to 4.26 μg kg~(-1), respectively. In general, an increase in the level of NAs was observed after the storage period. The proposed method may therefore be a useful tool for food safety control once it allows assessing the profile and the dietary intake of NAs in food over time.