Determination of 8 N-Nitrosamines in Dried Fish, Dried Small Shrimp and Shrimp Meat by GC-MS/MS with Alkali Solution Treating Followed Active Carbon Cartridge Solid Phase Extraction

N-nitrosodimethylamine (NDMA), N-nitroxymethylamine (NMEA), N-nitrosodiethylamine (NDEA), N-nitrosodipropylamine (NDPA), N-nitrosopiperidine(NPIP), N-nitrosopyrrolidine (NPYR), N-nitrosomorpholine (NMOR) and N-nitrosodibutylamine (NDBA) in dried fish, dried small shrimps and shrimp meat were determined by gas chromatography-tandem mass spectrometry (GC-MS/MS) with alkali solution treating and active carbon solid phase extraction. 10 g of sample was placed into a 50 mL screw-cap plastic centrifugation tube, and 50 μL of internal standards solution including NDMA-d6，NDPA-d14 and NPYR-d8 with each concentration of 1 mg/L, 1.0 g of Ba(OH)₂•8H₂O and distilled water with volumn to the 50 mL scale line were added. Then the tube was heated at 80 ℃ for 1 h in an oven and centrifuged at 10 000 r/min for 10 min. All the supernatant was passed through a Sep-Pak^® Plus AC-2 cartridge which had been conditioned with 6 mL of dichloromethane, 6 mL of methanol and 6 mL of water in turns, and the anlytes were eluted with 5 mL of dichloromethane from the cartridges after aspiration to dryness by a vacuum pump. The eluent was concentrated further to 1 mL under nitrogen flow at 40 ℃ and was then passed through a 0.22 μm pore filter for injection. The chromatographic separation was carried on a DB WAXUI column (30 m×250 μm×0.25 μm) and detected with tandem mass spectrometry at multiple reactions monitoring mode. The calibration curves show good linearity in the range of 1-200 μg/L with the correlation coefficients (R²) greater than 0.998. The limits of detection and quantification are in the ranges of 0.03-0.25 μg/kg and 0.10-0.85 μg/kg, respectively. The recoveries of N-nitrosamines are 71.3%-119.0%, except that NDBA is slightly lower at high addition levels, and the relative standard deviations (RSD) is 0.65%-15.4%. 23 samples from local supermarket including 8 ready-to-eat dried fish, 5 fresh dried fish, 4 dried small shrimp and 6 shrimp meat were detected. The results indicate that NDMA is the major N-nitrosamines and is detected in all samples with the highest level among of the analytes, and the other N-nitrosamines are detected in partial samples with relative lower levels even blow the LOQ. The samples with the highest levels of NDMA are dried fishes and the levels of ready-to-eat dried fishes are much higher than that of the fresh dried fishes, the samples with medium and the lowest levels of NDMA are dried small shrimps and shrimp meats, respectively. NDBA should be paid more attention during the relative food safety control. This method is simple, environment-friendly, easy for high-throughput detection and reliable for both qualitative and quantitative analysis.