Residual Dynamics In Rape And Photolysis Of Clopyralid

Clopyralid (3, 6-dichloropyridine-2-carboxylic acid) is a selective herbicide used primarily to control broadleaf weeds. It was used to control thistle, composite, legumina and eggplant in rape, beet, flax, strawberry and shallot in the field. HPLC was used to study its residue analysis methods in soil, rape plant and rape seed. The residue dynamic and ultimately residue of 30% clopyralid SL was determined in soil, rape plant and seed. Photolysis of clopyralid was studied with 500W mercury lamp.The samples were extracted with 2% Ca(OH)₂ solution, then ethyl acetate after adjust the pH between 2～3. After evaporating by vacuum the extracts of plant and seed were cleaned up with silica column. Firstly, ethyl acetate was used to wash the pillar, and then ethyl acetate and methanol used to wash the pillar again to remove impurity and pigment, finally the collected was evaporated nearly to dryness. Agilent 1100 HPLC was used to analysis clopyralid with DIAMONSIL—C₁₈ column and VWD detector. Mobile phase was methanol: 25mol L-1 phosphate buffer solution (5:95). The fortified level of soil, rape plant and rape seed were 0.05 mg kg^-1, 0.50 mg kg^-1 and 1.00 mg kg^-1, the average recoveries of 30% clopyralid SL was 80.90%～99.11%, and C.V. was 1.15%～8.50%, respectively. The recoveries were all exceed by 80% and correspond to residual analysis. The limit of detection (LOD) of sample was 0.2rig, and the limit of quantification (LOQ) was 0.002 mg kg^-1.The degradation of 30% clopyralid SL in soil and rape plant was detected by HPLC through the two years experiments in Jilin agricultural university trial field. The degradation of 30% clopyralid SL was correspond to the one-level dynamic equation, C=C0ekt. In soil, the dynamic equation was C=0.4502e-^0.084t, C=0.3878e-^0.104t and the t_1/2 was 3.2d and 3.5d in 2005 and 2006, respectively. In rape plant, the dynamic equations were C=6.61e-^0.1026t, C=12.634e^0.1203t and t_1/2 was 2.7d and 1.5d in 2005 and 2006 respectively. Two year experiments showed that 30% clopyralid SL was not detected in soil rape plant and rape seed at harvest. The result also showed that the degradation of 30% clopyralid SL in rape plant was faster than that in soil and clopyralid is a non-persistent pesticide (t_1/2＜30days).Mercury lamp was used to study the photolysis of clopyralid. Different concentration and pH of clopyralid were studied in same temperature and irradiation. In addition, the experiment also analyzed the photolysis dynamic in soil. It showed that the degradation of low concentration clopyralid was faster than that of high concentration; degradation of high pH clopyralid was faster than low pH; degradation of clopyralid in 500W irradiation was faster in soil. The dynamic equation was C=4.6031e^0.1418t, the t_1/2 was 4.3h.