Dissipation Study of Dimethoate, Ethion and Oxydemeton Methyl in Chilli

The dissipation of dimethoate 30 EC (300 g a.i.ha⁻¹), ethion 50 EC (375 g a.i.ha⁻¹), oxydemeton-methyl 25 EC (500 g a.i.ha⁻¹) were studied on chilli for estimation of its half life (T) and waiting period (T). Quantification 1/2MRL/TOL of residues was done on Gas Liquid Chromatography (GLC) equipped with Ni ⁶³ electron capture detector (ECD) for dimethoate and ethion where as oxydemeton methyl residues were estimated on Gas Chromatography- Mass Spectrometry (GC-MS). The residues of the three insecticides persisted up to fifteen days and were below detectable level (BDL) on the twentieth day of spraying. From the dissipation data, the half life (T_1/2) values of dimethoate, ethion and oxydemeton methyl were calculated as 1.94, 3.43 and 4 d respectively. A waiting period of 13.63, 28 and 7 d were calculated for dimethoate, ethion and oxydemeton methyl on chilli.