Determination Of Multi-pesticide Residues In Dried Fruits And Nuts By UPLC-MS/MS

Dried fruit and nuts, such as raisin, red jujube, walnut, almond and so on, are famous as the special local products of Xinjiang, which play an important role in the local economy. Pesticides were extensively used in growth process of dried fruit and nuts to ensure their quality and yield. However, it is inevitable to make pesticides remain in dried fruit and nuts so that may pose a risk to human health. Nowadays, a number of conmunities and countries have paid more and more attention to the problem of pesticide residues in food and harmonized stricter maximum residue limits(MRLs) of pesticide residues for dried fruit and nut matrixes. China has paid more and more attention to the security of food safety and harmonized stricter MRLs for food. However, there is a gap between our country and international coummunities about the amount and MRLs of pesticide. Therefore, devolping the analytical method to determine the pesticide residues in dried fruit puples and nuts matrixes is vital to ensure the security of food and health of people as well as avoid the barriers in international trade.In this study, according to different characteristics of the dried fruit and nut matrixes, they were divided into two groups to study the method for determination of the pesticide residues which may be applied to the culitivation process of fruits and nuts.(1) A modified dispersive solid-phase extraction(d-SPE) method followed by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry(UPLC-MS/MS) analysis was developed for the determination of 56 pesticide residues in dried fruits. Samples were soaked by water, and then 0.1% formic acid-acetonitrile was added to extract the analytes. The extracts were cleaned up by dispersive solid-phase using primary secondary amine(PSA). The modified d-SPE method could not only enhance penetration of acetonitrile but also remove most of saccharides, so the efficiency of extraction was improved significantly. The analytes were separated by liquid chromatography and determined by triple-quadrupole mass spectrometry. Matrix-matched curve external standard method was used for quantification. The linearity of all the analytes was good in the concentration ranges from 10 μg/L to 500 μg/L with correlation coefficient larger than 0.990. The average recoveries at three spiked levels of 5, 10 and 50 μg/kg ranged from 60.4% to 127.9% with the relative standard deviations(RSDs, n=6) from 1.1% to 20.0%. The limit of detection(LOD) and the limit of quantification(LOQ) of 56 analytes were in the range of 0.1-1.0 μg/kg and 0.3-3.1 μg/kg, respectively. The method has been proven to be sensitive, simple, quick, economical and suitable for determination of 56 pesticide residues in dried fruit pulps.(2) A multiresidues analytical method for the determination of trace levels of 100 pesticides in nuts has been developed based on cleaning up by freezing, Qu EChERS and determining by ultra-performance liquid chromatography-hybrid triple quadrupole linear ion trap mass spectrometer(UPLC-QqLIT-MS). The freezing and d-SPE with PSA and C18 were ultilized to minimize the co-extract liquid. The linearity of all the analytes was good in the concentration ranges from 5 μg/L to 500 μg/L with correlation coefficient larger than 0.990.The recoveries obtained by this method ranged from 60.2% to 128.0%(except novaluron and chlorbenzuron in walnuts) and RSDs(n=5) in the range from 1.0% to 20.0% at three spiked concentration levels of 10, 50 and 100 μg/kg. The limit of detection(LOD) and the limit of quantification(LOQ) of 100 pesticides were varied from 0.3 μg/kg to 3.1 μg/kg and 0.9 μg/kg to 10.0 μg/kg, respectively. The proposed method was simple, quick and sensitive. It is applied successfully for the determination of 100 pesticide resuides in nut matrixes.(3) A simple, selective and sensitive method based on gel permeation chromatography(GPC) cleanup has been established for the determination of 8 benzoylurea insecticides in walnuts by ultra-performance liquid chromatography-hybrid triple quadrupole linear ion trap mass spectrometer(UPLC-QqLIT-MS). The experimental conditions were investigated and optimized, including extraction solvents, GPC conditions, and ionization mode. The analytical procedure is based on liquid-solid extraction with 10%aceton-n-hexane mixtrue and cleaned up by GPC. Matrix effects were investigated, all BUs except for diflubenzuron and chlorbenzuron had matrix effect, so the matrix-matched calibration curve were used for quantification to compensate for the matrix effect. The linearity of all the analytes was good in the concentration ranges from 5 μg/L to 500 μg/L with correlation coefficient larger than 0.992. The mean recoveries obtained by this method at three spiked concentration levels(10, 50, and 100 μg/kg) were in the range of 62.6-112.1%, with the relative standard deviation(RSD, n=5) ranged from 1.4 to 19.0%. The limits of detections(LODs) and the limits of quantifications(LOQs) varied from 0.6 to 3.0 μg/kg and 1.8 to 9.7 μg/kg, respectively.The proposed analytical method proved to be simple, quick, sensitive and successfully applied to determine 8 benzoylurea insecticides in walnut samples.