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Avermectin B1(abamectin) is an very effective acaricide/insecticide. Because it is applied at low rates, the resultant residue level would be quite low and this requires highly sensitive analytical method. In this study, three analytical methods for avermectin Bl, were compared in view of detectability and sensitivity. The first analytical method was an HPLC method employing the fluorescence detection of avermectin. The second analytical technique to quantitate avermectin Bl, and its photodegradative delta 8,9-isomer employed trifluoroacetic anhydride and 1-methylimidazole in DMF. The new method was the modification of trifluorescence method. The average recoveries of avermectin Bl_a for the concentration range from 1 and 10 ng/g in whole apple fruit by fluorescence method were 90.3% and 88.2% respectively. In trifluorescence method, the recoveries of the avermectin B1_a and delta 8,9-isomer were 100.7% and 94.7% in concentration from 5 ng/g and 25 ng/g. The average recoveries of 5 ng and 25 ng/g in the newly modified method were 95.0, 99.0. 96.0, 92.8% in whole apple and soil respectively.
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