| Plant growth regulators are a class of synthetic pesticides with plant hormone activity, widely usedin regulating fruits growth and metabolic processes, which play important roles in improving the yieldand quality of agro-products. However, with the development of science and technology, reports on thesafety issues of plant growth regulators are increasing, and this problem has become a common concernto the world. Studies have shown that: the half-life of paclobutrazol residue in soil was so long that itmay harm non-target substance. Gibberellic acid may affect animal growth and development, and evencause the body to become cancerous. Long-term exposure to forchlorfenuron may cause disorders ofprotein metabolism in the body, mild emphysema and loss of body weight. Due to the strong polarity,thidiazuron can easily move from ground to the surface, and lead to the pollution of surface water.2,4-D had been demonstrated to affect thyroid and gonads, which was listed as endocrine disruptionchemicals. At present, the five plant growth regulators mentioned above are often used as mixture inChina, however, there are critical lack of basic researches, including determination methods,environmental behaviors and the limit standards for them. Therefore, it has a very important practicalsignificance for the study of multi-residue determination methods and dissipation dynamics ofcommonly used plant growth regulators in fruits and vegetables.This paper focused on the multi-residue determination method of paclobutrazol, gibberellic acidforchlorfenuron, thidiazuron and2,4-D, carried out the residual dynamic study of paclobutrazol in peachand soil, the main contents and results are as follows:(1)Through the optimization of the instrument parameters, composition of mobile phases, sampleextraction and purifying methods, the LC-MS/MS method was developed for the determination ofpaclobutrazol, gibberellic acid, forchlorfenuron, thidiazuron and2,4-D in fruits and vegetables. Theresults showed that: good linear relationships were shown for paclobutrazol, forchlorfenuron,thidiazuron and2,4-D in the range of1.0μg/kg~25μg/kg, and excellent linear relationship was shownfor gibberellic acid in the range of10μg/kg~500μg/kg, all the correlation coefficients were greater than0.9900. Their recoveries were in the range of100.1%~104.0%,101.2%~108.4%,83.2%~89.7%,88.3%~105.1%,93.9%~104.6%, respectively, in peach samples, and the relative standard deviationswere from2.1%to11.8%, method detection limits were0.5μg/kg,5.0μg/kg,0.4μg/kg,0.3μg/kg,1.0μg/kg, respectively. This method can be applied to grape, cucumber, apple, orange and other fruits andvegetables, with recoveries ranging from76.2%to112.7%, and the relative standard deviations werefrom0.47%to15.2%.(2)Through the study of extraction solvent, extraction temperature and extraction time, anaccelerated solvent extraction method was established for the determination of paclobutrazol in soil.The results showed that: in the concentration range of5μg/mL~100μg/mL, good linear relationshipwas shown for paclobutrazol with a correlation coefficient of0.9992. When the spiked levels were0.005mg/kg,0.01mg/kg,0.02mg/kg, the recoveries were between98.1%and100.6%, and the relative standard deviations were from1.7%to5.5%, the method detection and quantification limits were1.0μg/kg and3.0μg/kg, respectively.(3) On the basis of the established determination methods of paclobutrazol residue in peach andsoil, field tests were carried out of paclobutrazol in peach. The results showed that: paclobutrazol can beeasily degradated in peach fruits and soil, in2010and2011, the half-life of paclobutrazol residue inpeach was8.65day and5.39day, respectively, and the half-life of paclobutrazol residue in soil was22.95day and14.84day, respectively. Through the study of the final residue test, according to thenational situation and paclobutrazol MRLs in EU (0.5mg/kg) and Japan (0.2mg/kg), recommended that:the application method of paclobutrazol was foliar spray, spraying dose was1000mg ai/L, the sprayingnumbers were twice, and the recommended preharvest interval should be21day. |
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