Submitted to: Journal of Association of Official Analytical Chemists International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2010
Publication Date: 2/1/2010
Citation: Lehotay, S.J., Mastovska, K., Lightfield, A.R., Gates, R.A. 2010. Multi-Analyst, Multi-Matrix Performance of the QuEChERS Approach for Pesticide Residues in Foods and Feeds Using LC-MS/MS Analysis with Different Calibration Techniques. Journal of Association of Official Analytical Chemists International. 93(2):355-367.
Interpretive Summary: One of the most powerful methods of analysis for pesticide residues in foods is liquid chromatography-tandem mass spectrometry (LC-MS/MS), but the approach has a limitation that indirect effects from the sample matrix can reduce the quality of the quantitative results. There are several ways to try to overcome or compensate for the matrix effects, but each has its advantages and disadvantages. In this paper, we compared three means of quantitative calibration (standards in solvent-only, matrix-matching, and the echo-peak technique) for pesticide residue analysis to see which one had the best results for practical implementation. There were few matrix effects in 9 of the 12 commodities tested, so the methods worked equally well in those cases, but carrot, corn silage, and foliage needed matrix-matched calibration to achieve the most accurate results. This study provides important information and practical guidance to analytical chemists using LC-MS/MS, particularly for pesticide residue analysis in foods.
Technical Abstract: Three different calibration approaches were applied in liquid chromatography – triple quadrupole tandem mass spectrometry (LC-MS/MS) using electrospray ionization for the determination of 14 diverse pesticide residues at different levels in a variety of food matrices. This study was conducted as part of a 4-day training course for 17 chemists to learn the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) approach to pesticide residue analysis in foods. The analysts were divided into 4 different teams for the analysis of 12 different matrices (strawberries, plums, carrots, green peppers, milk, molasses, alfalfa oats, corn silage, dry pet food, soybean, almonds, and foliage). The acetate-buffered QuEChERS protocol gave excellent results in the spiked samples for all matrices tested. The LC-MS/MS calibration techniques consisted of external standardization in solvent solutions; matrix-matching; and the echo-peak technique. Peak areas were normalized to an internal standard in all 3 approaches. Matrix effects were observed with the corn silage, carrot, and foliage extracts, but they were minimal or nonexistent in the other matrices. Matrix-matching best compensated for matrix effects, but has logistical difficulties in real-world application and required extra sample preparation compared to the other approaches. The echo-peak technique reduced matrix effects but did not eliminate them.