Determination of residue level of endosulfan in black tea in Bangladesh.

The study was conducted at Bangladesh Tea Research Institute (BTRI), Srimangal, Moulvibazar, Bangladesh during 2007-08 in both dry and wet season on the mature tea to determine the residue level of Endosulfan (Thiodan 35EC) in black tea at different plucking intervals after spraying and their degradation rate in order to fix the plucking interval to keep the residue level at Maximum Residue Limit (MRL) or below. Two doses of Endosulfan i.e. normal (1.5 Lha -1 ) and double dose (3.0 Lha -1 ) were applied. In dry season, the initial deposits of residues were 129 and 183 ppm on 0 day and declined to 0.91 and 2.11 ppm on the 14th day whereas in wet season, the initial residues were 122 and and 171 ppm on 0 day and declined to 0.87 and 2.01 ppm on the 14th day at normal and double dose respectively. The dissipating rate of residues of Endosulfan with the increase of plucking days was not uniform, rather it was exponential. Residue levels of Endosulfan at the commonly followed Pre Harvest Interval (PHI) i.e. 7th day were 1.68 and 3.14 ppm in normal and double dose respectively in the dry season while in the wet season the residue levels were recorded as 1.40 and 2.93 ppm. This slight variation in result at the same PHI indicates that seasonal variation has a role on the level of residues. However, these seasonal variation as well as dose rate differences were statistically non significant within themselves. Commonly followed PHI (7th day), the samples of Endosulfan at normal dose in both seasons did not exceed the MRLs imposed by EPA, Codex Commission, EEC/EU and German law.