Fig. 1

Chromatograms of a blank extract of watermelon sample; b a representative chromatogram of watermelon sample extract containing dimethoate (D, 5.17 ppb) and metalaxyl (M, 23.5 ppb); and c a representative chromatogram of durian sample extract contained dimethoate (D, 1.44 ppb) and metalaxyl (M, 4.41 ppb) Peak identification: 1 unknown peak from plastic centrifuge tube, 2, 4, 5, 6, 7, 8, and 9 unknown endogenous peaks found in watermelon samples, D dimethoate, M metalaxyl, A aldrin used as the internal standard in watermelon assay, F fenitrothion, the internal standard used in durian assay, and 10 the second peak of cypermethrin