Abiotic Enantiomerization of Permethrin and Cypermethrin
J. Agric. Food Chem., Vol. 55, No. 14, 2007 5739
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induce enantiomerization, especially when it is mixed with an
alcohol or exposed to sunlight.
This study is the first instance where the isomerization of
pyrethroids in organic solvents and solvent-water systems was
evaluated at the enantiomer level. This was made possible by
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it is reasonable to speculate that similar enantiomerization may
also occur for cyfluthrin and cyhalothrin.
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Enantiomerization on the R-carbon due to exposure to
solvents may have significant consequences. For instance,
enantiomerization caused by solvents during sample extraction
and analysis may result in analytical artifacts and erroneous
information on the composition of stereoisomers. When envi-
ronmental samples are analyzed, caution should be used to avoid
the use of inappropriate solvents. Enantiomerization caused by
solvents may also produce unexpected toxicity in bioassays and
to nontarget species in the environment. In addition, products
with a single enantiomer (e.g., esfenvalerate and deltamethrin)
or selected stereoisomers (e.g., R-, â-, and θ-CP, λ-cyhalothrin,
and â-cyfluthrin) are increasingly being used nowadays, because
such products have improved efficacy and are also considered
more environmentally friendly due to the lower application rate
(10). However, enantiomerization caused by solvents in for-
mulation or during application may easily decrease the intended
efficacy and also lead to inaccurate expectations of environ-
mental benefits from such uses.
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Received for review March 27, 2007. Revised manuscript received May
17, 2007. Accepted May 18, 2007.
JF0708894