It is estimated that a quarter of the pesticides currently used in world agriculture contain chiral centers [1].  The majority of these compounds are applied as racemic mixtures even though one enatiomer exhibits the desired agricultural activity.  In the environment, the ratios of enantiomers are affected by biotic and abiotic processes that may result in either selective enrichment or depletion of isomeric forms depending on environmental conditions and are not readily predicted [2].  It has been shown that the compositional profile of chiral pesticides and pollutants within an exposed plant depends on tissue type and route of exposure [3,4].  In a recent study, myclobutanil, applied to strawberries exhibited rapid degradation of the (+)-myclobutanil enantiomer compared to the (-)-myclobutanil form [4].  The importance of identifying enantiomeric forms of pesticides and pollutants in the environment is relevant due to distinct differences in toxicological properties which can vary greatly [2].  The separation of these enantiomers, particularly in complex food matrices, can be challenging.  In this study, the separation of triazole fungicide enantiomers in food is demonstrated by gas chromatography mass spectrometry using a chiral stationary phase.  The instrument was modified to improve reliability and method robustness by using selective heart-cutting and column backflushing to reduce the matrix exposure to the chiral column thereby increasing column lifetime and performance reproducibility.  A programmed temperature vaporizer inlet was used to optimize sample introduction in order to reduce inlet decomposition or possible racemization.    Lewis, D. L.; Garrison, A. W; Wommack, K. E.; Whittemore, A.; Steudler, P.; Melillo, J. 1999 , Nature 401 (6756), 898-901. Richardson, S. D. 2006 , Anal. Chem., 78 (12), 4021-4045. Lee, W-Y.; Iannucci-Berger, W. A.; Eitzer, B. D.; White, J. C.; Mattina, M. I. 2003 , Chemosphere, 53, 111-121.Zhang, H.; Wang, X.; Qian, M.; Wang, X.; Xu, H.; Xu, M.; Wang, Q. 2011 , J. Agric. Food Chem, 59, 12012-12017.

Enatiomeric separation of chiral pesticides by gas chromatography-mass spectrometry

248th National Meeting (2014)

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