Submitted to: Journal of Chromatography A
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/5/2012
Publication Date: 12/28/2012
Citation: Kwon, H., Lehotay, S.J., Geis-Asteggiante, L. 2012. Variability of matrix effects in liquid and gas chromatography - mass spectrometry analysis of pesticide residues after QuEChERS sample preparation of different food crops. Journal of Chromatography A. 1270:235-245. Interpretive Summary: Pesticide residue analysis of foods is commonly conducted in laboratories worldwide to ensure food safety and conduct regulatory enforcement. Unfortunately, the most powerful analytical tools are susceptible to matrix effects that reduce the ability to accurately quantify the residue levels in complex food samples. A common method to improve accuracy is matrix-matched calibration, but it was not known if one sample type within the same matrix could adequately compensate for matrix effects for other sample types. In this study, we evaluated the results for 38 representative pesticides in 20 samples each of rice, orange, apple, and spinach using two different detection methods. Main conclusions are that acceptably accurate quantitative results were achieved by using matrix-matching even with different samples of the same type. This provides justification to use matrix-matching for regulatory purposes, and for this reason, this research provides a positive benefit to regulatory agencies worldwide.
Technical Abstract: Gas and liquid chromatography (GC and LC) coupled to sophisticated mass spectrometry (MS) instruments are among the most powerful analytical tools currently available to monitor pesticide residues in food, among other applications. However, both GC-MS and LC-MS are susceptible to matrix effects which can adversely affect quantification depending on the analyte, matrix, sample preparation, instrumentation, and operating conditions. Among the approaches that reduce matrix effects, the most common in pesticide residue applications is matrix-matched calibration because it is relatively inexpensive and simple. However, the quality of matrix-matched results in real-world analyses depends on the consistency of matrix effects among diverse samples. In this study, the variability of matrix effects was measured for 38 representative pesticides in 20 samples each (including different varieties) of rice, orange, apple, and spinach extracted using the “quick, easy, cheap, effective, rugged, and safe” (QuEChERS) method for analysis by LC-MS/MS and low-pressure GC-MS. In LC-MS/MS, only oranges gave greater than 20% matrix effects for a few pesticides. GC-MS exhibited larger matrix effects, but as in LC-MS/MS, the differences were reasonably consistent among the 20 samples tested. Main conclusions of this study are that for the conditions utilized, matrix-matching was not needed for most pesticides in the simpler food matrices, and for the more complex orange matrix, acceptably accurate quantitative results were achieved by using matrix-matching even with a different sample of the same type. However, full confidence cannot be extended to matrix-matched results, and for consequential applications such as regulatory enforcement, confirmatory analyses using alternate quantitative determinations should also be conducted.