Abstract: Objective　To establish a method for determination of pyriclobenzuron (PBU) residues in rice and paddy environments, and to determine the residual amounts and observe the degradation dynamics of PBU.  Methods　In July 2022, the paddies of Zhejiang Academy of Agricultural Sciences were selected as experimental fields, and were divided into the blank control group (no pesticide application), the 1⁃fold⁃concentration pesticide group (1 kg/667 m2), and the 5⁃fold⁃concentration pesticide group (5 kg/667 m2), with a 100 m2 area in each group. At the early tillering stage of rice, 20% suspension of PBU sulfate was sprayed once in the 1⁃fold⁃concentration and 5⁃fold⁃concentration pesticide groups, and rice plants, paddy water and soil samples were collected 2 h, and 1, 2, 3, 5, 7, 11, 14, 21, 28, 35, 49 d and 63 d following spraying PBU, while rice straw, field soil, brown rice and rice husk samples were collected 98 d following spraying. PBU was extracted and purified in samples using a quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment technique, and the PBU contents were determined in samples using ultra⁃high performance liquid chromatography tandem mass spectrometry (UPLC⁃MS/MS). The solvent standard working solution and matrix standard working solution were prepared. A linear regression equation was fitted between PBU concentration (x⁃axis) and peak area (y⁃axis), and the ratio of the slope (k) of the matrix standard curve to the slope (K) of the solvent standard curve was calculated to evaluate the matrix effect of PBU in samples. According to the Guidelines for Pesticide Residue Testing in Crops (NY/T 788—2018), the addition levels of PBU were set at 0.005, 0.050, 5.000, 1 000.000 mg/kg in rice plants, 0.005, 0.050, 2.000, 10.000 mg/kg in paddy water, 0.005, 0.050, 2.000 mg/kg in soil, and 0.005, 0.050, 5.000 mg/kg in brown rice and rice husks. The recovery and relative standard deviation (RSD) of PBU addition were calculated to evaluate the effectiveness of UPLC⁃MS/MS for determination of PBU contents. The first⁃order kinetic equation of PBU concentration was fitted in samples at different sampling time points to analyze the trends in PBU degradation in rice plants, paddy water, and soil, and the half⁃life of PBU was calculated in different samples. Results　There was a good linear relationship between the mass concentration and peak area of PBU at concentrations of 0.000 1 to 0.020 0 mg/kg under solvent and matrix conditions (R2 = 0.985 8 to 0.999 7, t = -0.47 to 1.62, all P values < 0.01). The matrix effects of PBU were 70.26%, 65.42% and 65.12% in rice plants, brown rice and rice husks, indicating a matrix⁃inhibitory effect, and the matrix effect was 87.06% in soils, indicating a weak matrix effect. The recovery of PBU addition was 77.61% to 100.12% in different samples, with RSD of 1.43% to 6.74%, and a limit of quantification (LOQ) of 0.005 mg/kg, and the addition recovery and RSD met the requirements of the Guidelines for Pesticide Residue Testing in Crops (NY/T 788—2018), validating the effectiveness of UPLC⁃MS/MS assay. Following spraying PBU at a dose of 1 kg/667 m2, the half⁃life of PBU was 6.24 d in rice plants and 3.43 d in paddy water samples, respectively. The final residues of PBU were lower than the LOQ of 0.005 mg/kg in brown rice and rice husk samples 98 d following spraying PBU. Following spraying PBU at a dose of 5 kg/667 m2, the half⁃life of PBU was 15.75 d in rice plants and 7.62 d in paddy water samples, respectively. The final residue of PBU was lower than the LOQ of 0.005 mg/kg in brown rice 98 d following spraying PBU, and the final residue of PBU was 0.049 mg/kg in rice husks.  Conclusions　A simple, and highly accurate and precise UPLC⁃MS/MS assay has been developed for determination of PBU residues in rice plants and paddy environments through extraction and purification of PBU from matrix samples using QuEChERS pretreatment. After spraying PBU in paddies, the concentration of PBU gradually decreases in rice plants and paddy water over time, and the final residual concentration is low.

Key words: Pomacea canaliculata, Pyriclobenzuron, Pesticide residue, Degradation dynamic, UPLC?MS/MS

摘要： 目的　建立水稻及稻田环境吡螺脲残留检测方法，测定其残留量，并观察其消解动态。方法　2022年7月选取浙江省农业科学院水稻田作为试验田，将试验田分为空白对照组（不施药）、1倍施药浓度组（剂量1 kg/667 m2）和5倍施药浓度组（剂量5 kg/667 m2），每组面积100 m2。1倍和5倍施药浓度组分别在水稻分蘖初期施用20%吡螺脲硫酸盐悬浮剂1次，施药后2 h以及1、2、3、5、7、11、14、21、28、35、49 d和63 d分别采集水稻植株、稻田水、土壤样本，施药后98 d采集各组秸秆、田间土壤、糙米和稻壳样本。采用快速、简便、廉价、高效、稳定和安全（quick，easy，cheap，effective，rugged，and safe，QuEChERS）前处理方法提取和净化样本中吡螺脲，采用超高效液相色谱⁃串联质谱（ultra performance liquid chromatography⁃tandem mass spectrometry，UPLC⁃MS/MS）技术检测各样本中吡螺脲含量，配制溶剂标准工作液和基质标准工作液，以吡螺脲浓度为横坐标、峰面积为纵坐标拟合线性回归方程，计算基质标准曲线斜率k与溶剂标准曲线斜率K的斜率比值以评价吡螺脲在样本中基质效应。根据《农作物中农药残留试验准则（NY/T 788—2018）》，设置水稻植株中吡螺脲添加水平为0.005、0.050、5.000 mg/kg和1 000.000 mg/kg，稻田水中吡螺脲添加水平为0.005、0.050、2.000 mg/kg和10.000 mg/kg，土壤中吡螺脲添加水平为0.005、0.050 mg/kg和2.000 mg/kg，糙米、稻壳吡螺脲添加水平为0.005、0.050 mg/kg和5.000 mg/kg，计算吡螺脲添加回收率和相对标准偏差（relative standard deviation，RSD），评价UPLC⁃MS/MS技术检测吡螺脲含量的有效性。对不同时间采样的各样本中吡螺脲的浓度进行一级动力学方程拟合，分析吡螺脲在水稻植株、稻田水和土壤中的降解趋势，计算不同样本中吡螺脲半衰期。结果　在0.000 1 ~ 0.020 0 mg/kg浓度范围内，吡螺脲在溶剂和基质条件下质量浓度与检出峰面积间存在良好线性关系（R2 = 0.985 8 ~ 0.999 7，t = -0.47 ~ 1.62，P均< 0.01）。吡螺脲在水稻植株、糙米和稻壳中基质效应分别为70.26%、65.42%和65.12%，均< 80%，为基质抑制效应；在土壤中基质效应为87.06%，为弱基质效应。田间试验各样本中吡螺脲添加回收率范围为77.61% ~ 100.12%，RSD范围为1.43% ~ 6.74%，定量限为0.005 mg/kg，添加回收率和RSD符合《农作物中农药残留试验准则（NY/T 788—2018）》要求，验证了该检测方法的有效性。施用剂量为1 kg/667 m2的吡螺脲后，水稻植株和稻田水样本中吡螺脲半衰期分别为6.24 d和3.43 d；施药后98 d糙米和稻壳样本中吡螺脲最终残留低于定量限0.005 mg/kg。施用剂量为5 kg/667 m2的吡螺脲后，水稻植株和稻田水样本中吡螺脲半衰期分别为15.75 d和7.62 d，施药后98 d糙米中吡螺脲最终残留低于定量限0.005 mg/kg，稻壳中吡螺脲最终残留量为0.049 mg/kg。结论　本研究通过采用QuEChERS前处理方法提取和净化基质样本中吡螺脲、UPLC⁃MS/MS技术检测吡螺脲在水稻植株及稻田环境中残留量，建立了一套操作简单且准确度、精确度均较高的吡螺脲残留检测方法。在稻田中施用吡螺脲后，水稻植株及稻田水中吡螺脲浓度随时间推移逐渐下降，最终残留浓度较低。

关键词: 福寿螺, 吡螺脲, 农药残留, 消解动态, 超高效液相色谱?串联质谱法