Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
Monitoring and Decontamination of Pesticide Residues in Farm Gate
Vegetables
Anjana Srivastava
Department of Chemistry, G.B.P.U.A.&T., Pantnagar- 263 145 (UK)
Vegetables form an important component of human diet. They are however, infested by
various insect pests like aphids, jasssids, diamond moths, caterpillars, etc. Among the vegetables,
brinjal, cauliflower, tomato and okra etc. are some very common vegetables cultivated, throughout
the country but all are badly affected by insect-pest and diseases. In India, farmers use about
6000 tonnes of active ingredients to control pests of vegetables and fruits . Vegetables consume
14% of the total pesticides used in India, in which, the share of different types of pesticides in
Indian agriculture market shows that organophosphorus (50%) rank first, followed by pyrethroids
(19%), organochlorines (18%), carbamates (4%) and biopesticides (1%). Pesticide application is
a necessary step for coping with the pest related problems and therefore, it is not possible to meet
the requirements of our ever growing population without pesticide application. Indiscriminate use
of pesticides particularly at fruiting stage and
non adoption of safe waiting period leads to
accumulation of pesticide residues in consumable vegetables. Since most of the pesticides are
toxic in nature, their continuous ingestion by man even in trace amounts, can result in their
accumulation in body tissues with serious adverse effects on health. Hence it is important to
assess the pesticide residues in vegetables so that they may be removed to the maximum extent
possible.
Estimation of pesticide residues
The estimation of pesticide residues involve several steps like extraction of pesticide with
a suitable solvent, concentration of the solvent, partitioning with some polar / nonpolar solvent,
clean up and finally the analysis through HPLC, HPTLC or GC for quantitative estimation of the
pesticides.
Since several pesticides are used on one type of vegetables, therefore a multiclass
pesticide residue analysis method is more appropriate for quantitative determination of pesticide
levels in vegetables. For example cypermethrin, imidacloprid and carbendazim are being used on
okra, chlorpyrifos , imidacloprid and carbendazim on tomato etc. Chlorpyrifos and imidacloprid
(insecticides) and carbendazim(fungicide) are a few such pesticides which are being invariably
used on almost all the vegetables and so a method which can be used for estimating the pesticide
mixture is more desirable than the one which will estimate only a single compound.
Solvents like acetone, acetonitrile, ethyl acetate, dichloromethane, methanol, hexane and
propenol-2 are some common solvents which are used for extraction of pesticide residues.
Similarly adsorbents like alumina, neutral silica gel G and charcoal are used for column cleanup.
After going through the rigorous extraction and clean up processes the sample is subjected to
GC, HPLC or HPTLC analysis for quantitative determinations of pesticides as these techniques
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