The Storage Stability Of Seven High Frequency Detection Pesticides In Citrus

Due to the limit of human resources and technology, spot check and detection of pesticide residues and pesticide registration residue test in foods,wouldn’t started right off.Instead of immediately analysis, the pesticide samples usually be stored under certain conditions after getting them. Former studies shows that with the extension of storage, most of pesticides would decompose, thus would directlyinfluence the accuracy of analytical results. This situation will have an impact on accurate assessment of pesticide safety andthe interests of consumers. So, it is necessary to search the pesticide storage stability. This study used 7 pesticides with high frequency detection rate in citrus, in order to provide some reference data to perfect the database system of stability of pesticide in different matrices.This study clarified the variation trendency of seven high frequency detection pesticides in different citrus matrices, fortified levels and storage temperatures. QuEChERS method combined with gas chromatography(GC), gas chromatography-mass spectrography(GC-MS), and ultra-performance liquid chromatography-mass spectrometry(UPLC-MS/MS) were used in detecting the pesticide concentration in different interval periods. Results shows:(1) The storage stability of pesticides is greatly affected by pesticides types. It showed that the carbamates pesticide has the fastest degradation rate, and pyrethrum ester insecticide had a faster degradation than organic phosphorus pesticide. Compared with previous studies, this phenomenon perhaps relate to the saturated vapor pressure and water solubility of pesticides.(2) Temperature is also an important factor affecting the stability of pesticide storage. Compared with room temperature, stored under the condition of-20℃, the degradation rate was significantly decreased, and the stability was prolonged.(3) In addition, the initial concentration level and the matrix species also affect the stability of pesticides. The degradation rate of low concentration pesticides was faster than high one. The degradation rates of most pesticides in citrus pulpwas higher than whole fruit and the peel, while it may be owing to its higher water content.(4) Taking the residues of 70% as the stable storage standard, and ordering stable storage time to stable period. At room temperature, the stable period of isocarbophos was 7 days, profenofos 7d, triazophos 7d, bifenthrin 5d, fenpropathrin 1d, carbofuran less than 1d, carbosulfan less than 1d. To prevent the decomposition of pesticide, samples should be tested quickly after collection, or stored at freeze condition in a short period.