Determination of organochlorine and organophosphorus pesticide residues in tomatoes, potatoes and pineapples from selected farmlands in southwest Ethiopia

Abstract

Pesticides are widely used in Ethiopian agriculture to increase the yield, improve the quality, and extend the storage life of horticultural crops. But wide uses of these chemicals could result in contamination of air, water, food, and ecosystem. In this study, determination of organophosphates and organochlorines pesticides residues in tomato, potato and pineapple samples from selected farmlands of Jimma zone and Kefa zone, in the southwest of Ethiopia was undertaken. The samples were collected from tomato, potato and pineapple farmlands of Mana, Jimma, Shebe sombo, Saka, Gojeb and Dedo woredas. The QuEChERS methodology that involves the extraction of the sample with acetonitrile containing 1% acetic acid and anhydrous magnesium sulfate, as well as anhydrous sodium acetate followed by d-SPE cleanup step, were used. Chromatographic separation and quantitative determinations of 4 OPPs and 7 OCPs was performed using gas chromatography-electron capture detector. The validity of the method was evaluated by recovery studies by spiking the target pesticides in tomato, potato and pineapple samples. The obtained recovery values were ranging from 71.22 – 121.56% with the exception of the recoveries of chloroflurenol-methyl and chloropyrifos, which were 65.651% and 67.90%, respectively, in potato matrices. Pesticides including dimethoate (except in Mana and Saka buyo qacama tomato), malathion (except in Saka buyo qacama tomato), p,p'-DDT, endrin, and dieldrin were not detected in all tomato, potato and pineapple samples. Other pesticides such as chloropyrifos, dibutyl chlorendate, p,p'-DDE, chloroflurenol-methyl, endosulfan sulfate and methoxychlor were detected in all samples. But, except dibutyl chlorendate and chloroflurenolmethyl the remaining detected concentrations of other pesticides considered in this study were below the MRL set by EU guidelines. Although the obtained concentrations were safe for most of the analytes, the one way ANOVA result (p ≤ 0.05) indicated the presence of significant variations among the sampling sites. Generally, the observed result indicates the need for the regular monitoring of pesticide residues since the detected levels indicate as the producers are using these pesticides on their farmlands.