Stability of Pyrethroid Insecticides in Mosquito Coil Extract

The recovery of pyrethroids with furan ring from mosquito coil was not sufficient (about 70%), because they were degraded in organic solvent solution by tabu powder components. Tabu powder extract was divided into 9 components on TLC and some of these react with the pyrethroids in the solution. The most active constituent was identified as pheophytin by infrared and visible absorption spectra. The pyrethrois were degraded also by chlorophyll a and b, which were separated from spinach, but were not degraded by phytol, the alcohol moiety of chlorophyll. It was deduced that the pyrethroids decomposition in solution were caused by the porphine ring in the pheophytin or analogous substances. The pyrethroids in the mosquito coil were not decomposed by pheophytin but were decomposed by oxygen in air.