Comparison of thin layer chromatography (TLC) and gas chromatograph determination of propoxur residues in a cocoa ecosystem

Abstract

The fate of propoxur in a cocoa ecosystem has been studied using TLC and GC. Residues of propoxur as determined by both TLC and GC were not significantly different. TLC analysis of propoxur residues in soil, cocoa leaves and pods may not need any rigorous clean up since residues measured from cleaned and uncleaned extracts were not significantly different. The residue levels of propoxur in the soil were found to decrease rapidly and, by the 21st day, none was detected in the topsoil (0 – 15cm). Evidence of leaching of propoxur residues in the soil environment has also been demonstrated. The amount left in the top soil after the first seven days were 27%, 23% and 24% as determined by the TLC only, TLC with clean-up and GLC respectively. About 38% of pesticides detected on the cocoa pod on the day of treatment remained as residues on the pod seven days after treatment. The residue detected on the leaves on the day of treatment was higher than that for the soil. This decreased rapidly to 1.7% in 21 days compared to 16% for the soil and 23% for the pod. No propoxur residue was detected 21 days after spraying.


African Journal of Science and Technology Vol.4(2) 2003: 24-28