Deternimation Of N-nitrosamines In Aquatic Products

N-nitrosamines are a group of organic compounds with a special segment of N-NO,which are widely spread in surrounding mediums.Nitrosamines are potent carcinogents which can include liver tumour in various species and are toxic to human beings.In the process of free radicals and lipid peroxidation,it can be quickly absorbed in the body through the digesive tract,causing damage to human tissues such as liver and kidney.The national standard has specified the N-dimethylnitrosamine in aquatic products should be less than 4.0 μg/kg.However,the current method has some problems that need to be improved.This thesis established the determination method of N-nitrosamines in aquatic products.(1)In this study,a comprehensive analytical method based on gas chromatography-tandem mass spectrometry(GC-MS/MS)was developed for the determination of nine N-nitrosamines in aquatic products.Identification and quantification were achieved using an electron impact ion(EI)source in positive ion mode with multiple reaction monitoring(MRM)mode.The internal standard method was used to quantify the N-nitrosamines.Under the optimal conditions,the correlation coefficients of the standard calibration curves were greater than 0.99 in the range of 1-20 μg/L.The limits of detection were 0.3 μg/kg(S/N=3)and limits of quantification were 1 μg/kg(S/N=10).At spiked levels of 1,2,10 μg/kg,the average recoveries of N-nitrosamines in spiked samples ranged from 80.4% to 98.5%,with relative standard deviations between 2.41% and 12.50%.This method was used to determine aquatic products,The results showed that N-nitrosamines levels of salted aquatic products were generally higher than other samples.(2)In this work,we have developed a sensitive method for detection and quantification of eight N-nitrosamines in aquatic products which are nonvolatile.The method is based on liquid chromatography coupled to tandem mass spectrometry,using atmospheric pressure chemical ionization(APCI)in positive mode with a triple quadrupole analyzer.The simultaneous acquisition of two MS/MS ttransitions in multiple reaction monitoring(MRM)mode for each compound,together with the evaluation of their relative intensity.Under the optimal conditions,the correlation coefficients of the standard calibration curves were greater than 0.99 in the range of 10-500 μg/L.The limits of detection were 0.3 μg/kg(S/N=3)and limits of quantification were 1 μg/kg(S/N=10).At spiked levels of 1,2,10 μg/kg,the average recoveries of N-nitrosamines in spiked samples ranged from 82.2% to 106%,with relative standard deviations between 1.22% and 12.93%.This method was used to determine aquatic products,the results showed that N-nitrosamines levels of salted aquatic products were generally higher than other samples.(3)The accuracy,linearity and suitability of the two methods were validated and the consistency of the two methods was verified.The results of the validation showed that the two methods were consistent,and the formation and control of nitrosamines in foods were discussed.