This result is beyond the scope of this study to identify these unknown
and possibly endogenous compounds in these two tropical
fruits.
Of the 28 pesticides investigated, only five were detected
in the watermelon samples. These were carbofuran,
chlorpyrifos, diazinon, dimethoate, and metalaxyl. Seven
watermelon samples were found to contain no pesticides;
this represents a rate of free pesticides of 9.3 % (Fig. 2a).
Pesticide residues were detected in 68 watermelon samples.
This corresponds to a rate of pesticide detection of 90.7 %.
Some samples contained only one pesticide, while others
(41 %) had multiple pesticide residues. However, in all of
the 68 watermelons in which the pesticides were found, the
pesticide levels were considerably low, less than the
recommended MRL values . Regarding the types
of pesticides detected in watermelons, only one
sample was found to contain carbofuran at a concentration
of 0.01 ppb (lg/kg), which is much lower than its recommended
MRL (0.1 ppm or 100 ppb). Two watermelon
samples contained diazinon at concentrations of 0.02 and
0.04 ppb. Again, these levels found were well below the
MRL suggested for diazinon in watermelons (0.01 ppm or
10 ppb). Chlorpyrifos was detected in one watermelon
sample at a concentration of 1.3 ppb, which was below its
MRL value. Of interest, dimethoate and metalaxyl were the
most often found pesticides in the watermelon samples
investigated (Fig. 2b).