| In recent years,various food safety problems have emerged in an endless stream,which not only bring harm to people’s health,but also affect the prosperity and stability of the society.The problem of pesticide residues has become one of the hot topics in today’s society.It is inevitable that agricultural drugs such as fungicides,pesticides or plant growth regulators will be used in the grape growing process.If pesticide residues exceed the standard due to their improper use,not only the food safety of grape will be directly affected,but also the development of grape industry will be restricted.It is of great significance to establish an efficient and accurate method for the separation and analysis of pesticide residues in grape samples.A gas chromatography-triple quadrupole tandem mass spectrometry(GC-QqQ-MS/MS)method was developed for the simultaneous analysis of 33 pesticide residues in grape fruits,based on the analysis of fragment ions’ structures and secondary mass spectrometry fragmentation behavior of the target compounds.The main research achievements of this paper include:Firstly,a preliminary study on the mass spectrometry cracking behavior of target pesticides was carried out,exploring the microscopic chemical structure of characteristic fragment ions and the mechanism of secondary mass spectrometry fragmentation.Suitable ion pairs of MS/MS analysis were selected,thus a GC-QqQ-MS/MS method under multi-reaction monitoring(MRM)mode was developed.The method was applied to the determination of 33 kinds of pesticide residues in grape fruits of fresh edible grape and spiny grape,combined with stable isotope dillution internal standard.Secondly,in the pretreatment,grape samples were purified by C18 solid phase extraction(C18 SPE)cartridge and tandem SPE cartridges(including aminopropyl SPE cartridge and activated carbon SPE cartridge),after homogenization extracted by acetonitrile.The results indicated that this method had a good linear relationship within the concentration range of 0.0016～0.3200 mg/L with satisfactory linearity(R>0.9947).The limits of detection(LODs)were 0.064～40.000μg/L and the limits of quantification(LOQs)were0.0128～8.0000 mg/kg.The recoveries ranged from 70.1 % to 120.6 % for all the target pesticides with relative standard deviation(RSD)values less than 17.9 %,when spiked at three different concentration levels.Thirdly,deuterated m-Terpheny(TPh-D14)was used as internal standard substance,which effectively avoid the risk of quantitative calculation deviation,for the reason of interference peak of internal standard substance existed in the sample matrix.In this method,the object response signal was enhanced,baseline noise was reduce,and the target compounds were seperated from the baseline.The analytical sensitivity was greatly improved by 1 ～ 2 orders of magnitude higher than the national standard method,in order to gain more accurate qualitative and quantitative analytical results.The method meets all the specified criteria in the national standard method,such as parallel test,blank test,repeatability,limit and recovery,etc.,and is suitable for the analysis and effective control of trace/ultratrace pesticide residues in grape fruits and other fruits or vegetables.Fourthly,the pollution levels and distribution rule of these target pesticides in grape samples was analyzed in detail.The characteristic of pollution and distribution in different sampling sites was also discussed by partial least square discriminant analysis(PLS-DA).The results demonstrated that the main pesticide compounds for grape grey mould or grape downy mildew,such as iprodione,azoxystrobin and dimethomorph,are proved to place an important role in pesticide residue pollution in grape samples.Otherwise,food safety of grape and the formation cause in this province was evaluated,the scientific vineyard management was put forward,and the rational use of pesticides was offered,as well as the corresponding technical training and service guidance. |
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