Behavior of pre-mix formulation of imazethapyr and imazamox herbicides in two different soils.

Imidazolinone group herbicides are known for longer persistence in soil. Therefore, a laboratory study was performed to evaluate the persistence of pre-mix formulation of two imidazolinone herbicides-imazethapyr and imazamox in clay and sandy loam soils. Herbicide formulation was applied at 70 and 140 g a.i. ha-1 equivalent to recommended doses in legumes. For achieving efficient sample preparation, three methods namely ultrasonic-assisted extraction (UAE), matrix solid phase dispersion (MSPD), and solid phase extraction (SPE) were optimized. MSPD gave better recoveries (85.22 to 96.00%) over SPE (80.10 to 84.78%) and UAE (56.44 to 66.20%). Residues were estimated using gas chromatography tandem mass spectrometry (GC-MS/MS) which is previously not reported in open literature. Dissipation followed first-order kinetics and half-life period of 23.5 to 43.3 days in clay loam and 19.6 to 39.8 days in sandy loam soil. The results revealed the persistent nature of pre-mix formulation of both herbicides as only 64.2 to 86.6% residues dissipated after 90 days of application in both soils.

Determination of residues of fipronil and its metabolites in cauliflower by using gas chromatography-tandem mass spectrometry.

Fipronil is a widely used insecticide with a well-described toxicological pathway. Recently it has been widely used in India to control vegetable pests. The present study has been carried out to observe the persistence pattern of fipronil and its metabolites-fipronil sulfone, fipronil sulfide, fipronil desulfinyl in cauliflower and soil so as to know the potential risk if any to consumers and environment. Fipronil was applied @ 56 g a.i. ha(-1). Samples of cauliflower and soil were collected periodically; processed using QuEChERS method and analyzed by GCMS/MS. In cauliflower, residues of fipronil and its metabolites reached below detectable level before 30 days of application whereas in soil about 95% of total fipronil residues got degraded within same time period. Washing and washing followed by cooking or boiling was found effective in reducing residues. A safe waiting period of 15 days is therefore suggested before consuming cauliflower.