Persistence behaviour of deltamethrin on tea and its transfer from processed tea to infusion.

The dynamics and residues of deltamethrin in a tea grown in an open field ecosystem were investigated. The quantification was performed using gas chromatography-electron capture detection (GC-ECD) and confirmed by gas chromatograph-mass spectrometry (GC-MS) in selective ion monitoring (SIM) mode. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 87% to 101% with relative standard deviations (RSD) ranging of 0.7-7.1%. The residues of deltamethrin were found to dissipate following first order kinetics with half-life ranging between 3.04 and 3.54d for two different rates of foliar application. The deltamethrin residues are present in the processed tea are not transferred into the tea infusion during the infusion process, since their water solubility is extremely low. These results can be utilized in formulating the spray schedule and safety evaluation on deltamethrin tea crop.