Persistence of Permethrin and Cypermethrin Residues on Treated Vegetables: An Overview
Grade Level at Time of Presentation
Sophomore
Major
Biology
Minor
Chemistry
Institution
Kentucky State University
KY House District #
29
KY Senate District #
36
Faculty Advisor/ Mentor
Dr. George antonious, ph.d.
Department
Environmental Studies
Abstract
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). Pyrethroids constitute the majority of commercial insecticides. The major agricultural pyrethroids at present are esters of 3-phenoxybenzyl alcohol or α-cyano-3-phenoxybenzyl alcohol used as a single isomer (deltamethrin) or as a mixture of four isomers (permethrin) or eight isomers (cypermethrin). Permethrin and cypermethrin are two insecticides commonly used in agricultural production in Kentucky and worldwide. They are very similar in chemical structure, but cypermethrin contains a cyanide (CN) group. It was found that the CN group affects the physical and chemical properties of the two compounds. We investigated differences in the persistence, vapor pressure and solubility in water that might affect their behavior under field conditions. A CN group at α- carbon of the 3-phenoxybenzyl-alcohol moiety enhanced the insecticidal activity roughly 3-6 fold compared to non-cyano pyrethroids. The solubility of permethrin in water is 5.5 ˟ 10-3 mg/L at 20⁰C versus cypermethrin that is 4.0 × 10mg/L at 20⁰C. Permethrin was extracted from plants using hexane and cleaned-up using a 1.2 m × 2 mm i. d. open glass chromatographic column packed with Florisil. The GC chromatograms revealed the presence of the two sterioisomers (cis- and trans-permethrin)at retention times of 26.0 and 26.6 minutes, that corresponds to half-lives (T1/2) of 4.45 and 3.41 d, respectively. The electron impact mass spectrum of permethrin extracted from plant leaves and fruits indicated the molecular weight of 390 and molecular ions of m/z 183, 163, 127, 91, and 51, along with other characteristic fragment ions. The results revealed that the trans-isomer was less persistent than the more stable cis-isomer.
Persistence of Permethrin and Cypermethrin Residues on Treated Vegetables: An Overview
A pyrethroid is an organic compound similar to the natural pyrethrins produced by the flowers of pyrethrums (Chrysanthemum cinerariaefolium and C. coccineum). Pyrethroids constitute the majority of commercial insecticides. The major agricultural pyrethroids at present are esters of 3-phenoxybenzyl alcohol or α-cyano-3-phenoxybenzyl alcohol used as a single isomer (deltamethrin) or as a mixture of four isomers (permethrin) or eight isomers (cypermethrin). Permethrin and cypermethrin are two insecticides commonly used in agricultural production in Kentucky and worldwide. They are very similar in chemical structure, but cypermethrin contains a cyanide (CN) group. It was found that the CN group affects the physical and chemical properties of the two compounds. We investigated differences in the persistence, vapor pressure and solubility in water that might affect their behavior under field conditions. A CN group at α- carbon of the 3-phenoxybenzyl-alcohol moiety enhanced the insecticidal activity roughly 3-6 fold compared to non-cyano pyrethroids. The solubility of permethrin in water is 5.5 ˟ 10-3 mg/L at 20⁰C versus cypermethrin that is 4.0 × 10mg/L at 20⁰C. Permethrin was extracted from plants using hexane and cleaned-up using a 1.2 m × 2 mm i. d. open glass chromatographic column packed with Florisil. The GC chromatograms revealed the presence of the two sterioisomers (cis- and trans-permethrin)at retention times of 26.0 and 26.6 minutes, that corresponds to half-lives (T1/2) of 4.45 and 3.41 d, respectively. The electron impact mass spectrum of permethrin extracted from plant leaves and fruits indicated the molecular weight of 390 and molecular ions of m/z 183, 163, 127, 91, and 51, along with other characteristic fragment ions. The results revealed that the trans-isomer was less persistent than the more stable cis-isomer.