Submitted to: Journal of Chromatography A
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/30/2014
Publication Date: 7/8/2014
Publication URL: http://handle.nal.usda.gov/10113/59514
Citation: Gonzalez-Curbelo, M.A., Lehotay, S.J., Hernandez-Borges, J., Rodrigues-Delgado, M.A. 2014. Use of ammonium formate in QuEChERS for high-throughput analysis of pesticides in food by fast, low-pressure gas chromatography and liquid chromatography tandem mass spectrometry. Journal of Chromatography A. doi: 10.1016/j.chroma.2014.06.104. Interpretive Summary: Fast, inexpensive, and simple high quality methods of analysis are needed to provide high sample throughput for effective and efficient monitoring of pesticide residues in food. In this work, the “quick, easy, effective, rugged, and safe” (QuEChERS) approach to sample preparation has been revised to make it compatible with even faster methods of analysis (1 minute vs. 10 minutes per sample). The salts used in the original QuEChERS method could damage the instrument in the rapid flow injection approach, and the reagents used in this new version do not accumulate on internal surfaces of the sensitive intruments. This new QuEChERS version will be further evaluated in high-throughput applications to more efficiently monitor chemical residues in food.
Technical Abstract: The “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) approach to sample preparation is widely applied in pesticide residue analysis, but the use of magnesium sulfate for salting out in the method is not ideal for mass spectrometry. In this study we developed and evaluated three new different versions of the QuEChERS method using more volatile salts (ammonium chloride and ammonium formate and acetate buffers) to induce phase separation and extraction of 43 representative pesticide analytes of different classes. Fast low-pressure gas chromatography tandem mass spectrometry (LPGC-MS/MS) and liquid chromatography (LC)-MS/MS were used for analysis. The QuEChERS AOAC Official Method 2007.01 was also tested for comparison purposes. Of the studied methods, formate buffering using 7.5 g of ammonium formate and 15 mL of 5% (v/v) formic acid in acetonitrile for the extraction of 15 g of sample (5 g for wheat grain) provided the best performance and practical considerations. Method validation was carried out with and without the use of dispersive solid-phase extraction for cleanup, and no significant differences were observed for the majority of pesticides. The method was demonstrated in quantitative analysis for GC- and LC-amenable pesticides in 4 representative food matrices (i.e. apple, lemon, lettuce, and wheat grain). With the typical exceptions of certain pH-dependent and labile pesticides, 90-110% recoveries and less than 10% RSD were obtained. Detection limits were mostly less than 5 ng/g, which met the general need to determine pesticide concentrations as low as 10 ng/g for monitoring purposes in food applications.