New HPLC and fluorometric methods for the determination of pyriproxyfen and pyridalyl insecticide residues in tomatoes

Two sensitive, selective, and precise methods for the determination of pyriproxyfen and pyridalyl insecticide residues in tomatoes have been developed. The first method is HPLC with UV detection in which pyriproxyfen and pyridalyl were extracted with ethyl acetate and acetone, respectively, followed by cleanup using column chromatography. The recoveries ranged from 86.03 to 94.55 for pyriproxyfen and 95.08 to 99.38% for pyridalyl in tomato samples. The LOD of the method was 0.217 ppm for pyriproxyfen and 0.1866 ppm for pyridalyl. The second method depends on direct fluorometric determination of pyriproxyfen and pyridalyl in acetic and sulfuric acid at excitation and emission wavelengths of 320 and 646 nm, respectively. The recoveries of pyriproxyfen and pyridalyl in tomato samples ranged from 88 to 98% and 86 to 93%, respectively. The LOD of the method was 0.146 ppm for pyriproxyfen and 0.078 ppm for pyridalyl. Both methods were applied successfully to determine residues and rate of disappearance of pyriproxyfen and pyridalyl from tomatoes.