Ismail, Roseny Augustina
(2004)
Screening for pesticides (to develop a scheme for
testing).
Screening for pesticides (to develop a scheme for testing).
(Submitted)
Abstract
Pesticide poisoning is an important cause of morbidity and mortality in
many countries in the world. Pesticides are substances or mixture of
substances for controlling pest. Because of its hazardous property for killing the
pests, pesticides are also always harmful for human beings if there are not
used wisely and carefully. There are still many types of pesticides that are
available in the market although many types of them had been banned to be
produced or to be sold. For the purpose of pesticide screening, classification of
pesticides is based on their chemical properties. This project focuses on
pesticides which are classified as organochlorine hydrocarbons, chlorinated
phenoxy acids, organophosphorus pesticides, carbamate pesticides and
paraquat. In this project, pesticides from each class were added to an artificial
biological sample of stomach content.
Then, the pesticides in the stomach contents are extracted with various
types of solvents and mixture of solvents. In each step, the adjustment of pH is
so important because the solubility of pesticides in solvents may be depending
on the pH of the sample. By following this method of extraction, at the end of
the project the best solvent and the suitable pH for extracting pesticides in
biological samples will be known. After extracting the stomach contents, all
fractions of the organic layer that are collected in each extraction step, will be
evaporated and the residue will be subjected to thin layer chromatography
(TLC) for identification of pesticides. Beside identification of pesticides by using
TLC, identification of paraquat will be made separately and estimated
quantitatively.
Chromatograms of TLC of different pesticides will be developed using
different solvent systems according to their chemical nature. The suitability of
spray reagent to a particular class of compounds is also a main concern in this
project. This is to confirm the presence of pesticides in extracted solvents. The
Rt value of the samples and Rt value of the standards will be compared and
pesticides that have extracted will be identified. The presence of pesticides in a
particular solvent will indicate that the pesticides are soluble in that solvent.
Then, the solvent that extracted most of the pesticides will be concluded as the
best solvent to use for extraction.
At the end of this project, a simple scheme of extraction will be developed
and this scheme can be used for screening pesticides in pesticide poisoning
cases especially when the pesticide is unknown. The scheme is useful for the
usage of laboratories which lack of modern automated instrument for screening
pesticides.
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