Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 4/16/2004
Publication Date: 6/13/2004
Citation: Mastovska, K., Lehotay, S.J. 2004. Evaluation of common organic solvents for gas chromatographic analysis and stability of multiclass pesticide residues. Meeting Abstract. Interpretive Summary:
Technical Abstract: An ideal solvent for gas chromatographic (GC) analysis of multiclass pesticide residues should be compatible with: the analytes, sample preparation, and GC analysis. This study addresses each aspect with emphasis placed on stability of selected pesticides in 6 common organic solvents to assess their overall suitability in multiclass analysis. Three of the tested solvents, acetone, acetonitrile (MeCN) and ethyl acetate (EtAc), represent extraction solvents commonly used in multiresidue methods for determination of pesticides in produce. The other three, isooctane, hexane and toluene, often serve as exchange solvents before a GC analysis. Degradation of N-trihalomethylthio fungicides in MeCN was observed only in certain lots of the tested MeCN, but even if it occurred, the stability of these analytes as well as that of dicofol and chlorothalonil was dramatically improved by the addition of 0.1% acetic acid (v/v). Dicofol and chlorothalonil were also unstable in acetone, and pesticides with a thioether group (such as fenthion and disulfoton) degraded in the tested EtAc. Formation of isomers of certain pyrethroids (deltamethrin, lambda-cyhalothrin) was recorded in the chromatograms from MeCN and acetone solutions, but this effect more likely occurred during the GC injection than in solution. For several reasons, MeCN was found to be the most suitable solvent for extraction of a wide polarity range of pesticide residues from produce. After acidification, the stability of problematic pesticides in MeCN is acceptable, and MeCN can also serve as a medium for GC injection.