乐果与氧乐果在露地芹菜中的残留动态及安全性评价

为明确在芹菜中喷施乐果的安全性，研究了乐果和氧乐果在芹菜中的残留动态。以40%乐果为喷施药物，设置低浓度(600 g a.i/hm2)和高浓度(900 g a.i/hm2)2种施药剂量，在生长中期施药1次、采收期分别施药2次和3次，采集成熟的芹菜样品进行检测。样品采用乙腈提取，超高效液相色谱-串联质谱检测。结果]结果表明，在采收期按登记最高剂量喷施乐果1次，乐果的残留量3天后低于芹菜上的允许最大残留限量值（MRL值），但氧乐果高于MRL值。安全间隔期至少在21天以上，可以保证芹菜中乐果和氧乐果残留量低于MRL值。生长中期喷施乐果，乐果和氧乐果在芹菜中的残留量均低于MRL值。采收期施药2次，喷施2种浓度乐果在芹菜中的残留量在7天时均低于MRL值。施药3次，喷施低浓度乐果的残留量在7天时低于MRL值，喷施高浓度乐果的残留量超过MRL值。无论施药2次和3次，氧乐果的浓度在7天时均高于MRL值。结论]采收期多次喷施乐果，会造成氧乐果残留超标，建议在芹菜采收期禁止乐果施用。

Residual Dynamics and Safety Assessment of Dimethoate and Omethoate in Outdoor Celery

To ensure the safe application of dimethoate to celery, the residue dynamics of dimethoate and omethoate in celery are studied. 40% dimethoate emulsifiable concentrate was sprayed at different dosages (600 and 900 g a.i/hm2) during different growth periods, including once in the middle growth stage, twice and three times in the harvest period, and celery samples were collected. Samples were extracted by acetonitrile and determined by UPLC-MS/MS. The results showed that 3 days after one time application of dimethoate in the harvest period, the residue of dimethoate was lower than MRL value, however, the residue of omethoate was over than MRL value. The preharvest interval of 21 days was suggested for omethoate, which could ensure that the residues of dimethoate and omethoate in celery were both lower than MRL value. During the middle growth stage with one time application, the residue of dimethoate and omethoate in celery was lower than MRL value. By twice application of dimethoate during the harvest period, the residue of dimethoate in celery was lower than MRL value at 7 days. By three times application of dimethoate during the harvest period, the residue of dimethoate in celery at low dose spraying was lower than MRL value at 7 days and the residue of dimethoate in celery at high dose spraying was over MRL value at 7 days. For both twice and three times application, the residue of omethoate was over MRL value at 7 days. Repeated spraying of dimethoate can cause excessive omethoate residue, therefore, the application of dimethoate during the harvest period should be prohibited.