高效液相色谱法检测苦参碱在小白菜及土壤中的残留与消解动态

通过一年两季(春季和冬季)的田间试验,采用C18固相萃取-高效液相色谱分析方法,研究了苦参碱在小白菜及土壤中的残留和消解动态。方法验证试验表明:在0.02~0.5mg/kg添加水平下,苦参碱在小白菜和土壤中的平均回收率为71%~87%,相对标准偏差为5.7%~14%,在小白菜与土壤中的定量限(LOQ)均为0.02mg/kg。消解动态试验结果表明:苦参碱在小白菜及土壤中的消解过程均符合一级动力学方程,消解半衰期分别为1.0d(春季,小白菜)、1.5d(冬季,小白菜)、1.4d(春季,土壤)和1.6d(冬季,土壤)。最终残留结果显示:距最后一次施药7d后,高浓度(有效成分6.71g/hm2)和低浓度(有效成分4.47g/hm2)苦参碱在春季和冬季小白菜中的最终残留量在0.061~0.074mg/kg之间;在土壤中的最终残留量在未检出~0.075mg/kg之间。可见,苦参碱在小白菜及土壤中易消解,为保障小白菜食用安全,建议可将0.1mg/kg作为其最大残留限量,安全间隔期不小于3d。

Determination and study on residue and dissipation of matrine in Brassica rapa L. chinensis Group. and soil by high performance liquid chromatography

Field experiments were conducted to study the residues and dissipation of matrine in Brassica rapa L.chinensis Group. and soil in spring and winter. The C₁₈ solid phase extraction combined with high performance liquid chromatography (HPLC) analysis method was established to determine the content of matrine in pakchoi and soil. The recoveries of matrine in pakchoi and soil were 71%-87%, with relative standard deviations (RSDs) of 5.7%-14%. The limit of quantity (LOQ) of matrine in pakchoi and soil were both 0.02 mg/kg. The degradation results indicated the dissipation of matrine in pakchoi and soil accorded with the first-order kinetic equations, the half-lives were 1.0 d (spring, pakchoi), 1.5 d (winter, pakchoi), 1.4 d (spring, soil) and 1.6 d (winter, soil), respectively. 7 days after the last spraying, the final residues of high (6.71 g a.i./hm²) and low (4.47 g a.i./hm²) concentrations in pakchoi were 0.061-0.074mg/kg. However, the contents in soil were from nondetected to 0.075 mg/kg under the same conditions. The results demonstrated that the residues of matrine in pakchoi and soil were easy to be degraded. To ensure the safety, 0.1 mg/kg was recommended as maximum residue limit (MRL) of matrine in pakchoi, and 3 days was suggested as the safe interval period.