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Title: DERIVATIZATION REACTIONS OF CARBAMATE PESTICIDES IN SUPERCRITICAL FLUID CARBON DIOXIDE (SC-CO2)

Author
item King, Jerry
item ZHANG, ZHOUYAO - PHARMACIA CORPORATION

Submitted to: Analytical and Bioanalytical Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2002
Publication Date: N/A
Citation: N/A

Interpretive Summary: Analysis of toxicants, such as pesticides in agricultural products requires several discrete steps to prepare the sample prior to analysis. These steps consist of sample pretreatment, extraction with a solvent, further purification of the extract, followed by possible conversion of the pesticide to another chemical form to enhance its detection. In this study, pressurized carbon dioxide gas was used as an extraction solvent for pesticides, as well as a medium in which to convert the pesticide analytes to a different form more amenable for final analysis. The benefits of the described technique are the avoidance of using large amounts of solvents which are harmful to the environment and laboratory personnel, the integration of several steps in the analytical procedure,and equivalent sensitivity to other standard pesticide analysis methods. The results should aid food analysts and those involved with the analysis of trace levels of pesticides in the environment.

Technical Abstract: Because of the widespread use of toxic N-methylcarbamates as insecticides for agricultural products and concerns over their occurrence in food and drinking water supplies, various methods have been developed for monitoring the concentration levels of these carbamates. Typically, carbamates are extracted with organic solvents and analyzed either by pre-column derivatization for gas chromatography (GC), or via post column derivatization using HPLC. In this study, SC-CO2 has been used to dissolve derivatizing agents (such as heptafluorobutyric anhydride, HFBA, and pyridine), which also act as a modifier in the fluid phase, to simultaneously extract and derivatize carbamates from the sample matrix. The derivatized carbamate pesticides were then analyzed by GC/ECD or GC/MS with excellent sensitivity. The extraction/conversion of the carbamates was complete as indicated by a HPLC method using post column hydrolysis and o-phthalaldehyde derivatization, followed by fluorescence detection. GC-MS (ion trap) was also used for confirming the formation of the carbamate derivatives. Compared with the same HFBA reaction in an organic solvent, the derivatization reaction time was considerably shortened in SC-CO. The described approach combining both extraction and derivatization steps simplifies the analysis of carbamate pesticides as well as eliminates the use of organic solvent associated with the derivatization step.