Analysis of pesticide residues in Citrullus lanatus Thunb. and Capsicum annuum L. in Bwaise market
Abstract
A study was conducted to analyse pesticide residues in C. lanatus Thunb. (watermelon) and C.
annuum L. (green pepper) in Bwaise market, Kampala. This was driven by the increased
concern that heavily sprayed fruits and vegetables have pesticide residues at the time of
consumption which have long term cumulative effects. In this regard a total of 18 fruits and
vegetables were purchased from stalls at Bwaise market, packaged in sterile polythene and
taken to the laboratory for extraction and analysis. Sample preparation and extraction was done
using the multi-residue method extraction protocols for pyrethoids and organophosphorous
pesticide residues. Quantification of pesticides done using gas chromatography. Identification
of respective pesticides was done by comparison of retention times of the samples with that of
the library spectrums of the pesticide standards. The data was analysed using R package, Excel
spread sheets and graph and from this, T-tests, Dunnet’s multiple comparison test was drawn.
Pyrethroid pesticides predominated the samples analysed and organophosphorous pesticides
were absent in the green pepper samples analysed. In WMa Cypermethrin - 0.04760 mg/kg,
Deltamethrin - 0.02694 mg/kg, Lambda Cyhalothrin - 0.02828 mg/kg and Diazinon - 0.02715.
in WMb Cypermethrin - 0.01574mg/kg, Deltamethrin - 0.02462 mg/kg, Lambda Cyhalothrin
0.01896mg/kg, Diazinon - 0.02620 mg/kg, Malathion 0.01 mg/kg and Chlorpyrifos - 0.02699
mg/kg. WMc had Cypermethrin - 0.03341 mg/kg, Lambda Cyhalothrin - 0.028 mg/kg while
the rest of the active chemicals were undetected. GPa had Cpermethrin - 0.01896 mg/kg,
Deltamethrin - 0.02760 mg/kg and Lamda Cyhalothrin - 0.03883 mg/kg. Only Cypermethrin -
0.03502 mg/kg was detected in GPb. The pesticide residue levels detected were below the
stipulated MRLs of; Chlorpyrifos 2.0 mg/kg, Cypermethrin 2.0 mg/kg, Deltamethrin 0.1 mg/kg
for Capsicum annuum, Diazinon 0.02 mg/kg, Chlorpyrifos 0.05 mg/kg, Cypermethrin 0.2
mg/kg and Deltamethrin 0.05 mg/kg for Citrullus lanatus. with the exception of Diazinon
0.02715 mg/kg and 0.02620 mg/kg in the C. lanatus samples which was significantly higher
than 0.02 mg/kg. The findings point to the need for continuous monitoring of pesticide
contamination in foods throughout the country so as to determine their hazard levels and safety
for human consumption