Submitted to: Journal of the Association of Official Analytical Chemists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2007
Publication Date: 6/7/2007
Citation: Lehotay, S.J. 2007. Determination of Pesticide Residues in Foods by Acetonitrile Extraction and Partitioning with Magnesium Sulfate: Collaborative Study. Journal of the Association of Official Analytical Chemists.90:485-520 Interpretive Summary: Multiresidue analysis of pesticides in fruits, vegetables, and other foods is a primary function of several regulatory, industrial, and contract labs throughout the world. More than 100,000 food samples are analyzed each year for pesticide residues to meet a variety of purposes. In 2003, the ARS lab developed the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for multiclass, multiresdue analysis of pesticides in a variety of matrices, which is applicable for nearly any of these purposes, including regulatory enforcement and surveillance monitoring. This report and manuscript constitutes the culmination of an interlaboratory effort to validate the QuEChERS method according to AOAC International standards. Thirteen labs from 7 countries contributed to the study, and approximately 50,000 data points were generated. Overall results for the 28 pesticide residues determined in grapes, oranges, and lettuces demonstrate that the QuEChERS method is worthy of becoming an Official Method of AOAC International. It is already a widely used method of analysis in monitoring labs, and this project allows the QuEChERS method to be universally accepted in regulatory programs and become a "gold-standard" approach for pesticide residue analysis in foods.
Technical Abstract: A collaborative study was conducted to determine multiple pesticide residues in fruits and vegetables using a quick, simple, inexpensive, and effective sample preparation method followed by concurrent analysis with gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). For short, the method is known as QuEChERS (pronounced "catchers"), which stands for quick, easy, cheap, effective, rugged, and safe. Twenty representative pesticides were fortified in 3 matrices (grapes, lettuces, and oranges) at 3 duplicate levels unknown to the collaborators ranging from 10 to 1,000 ng/g. Additionally, 8 incurred pesticide residues were determined. Thirteen labs from 7 countries provided results in the study, and a variety of different instruments were used by collaborators. To achieve <10 ng/g detection limits in modern GC-MS, large volume injection (LVI) of 8 'L is typically needed, or the final extract can be concentrated and solvent exchanged to toluene (4 g/mL) in which case 2 'L splitless injection is used. In the study, the averaged results for data from 7-13 labs (not using internal standardization) for the 18 blind duplicates at the 9 spiking levels in the 3 matrices showed 87% recovery and 21% RSD inter-lab precision. Intra-lab repeatabilities for the method averaged 9.8% RSD for all analytes. The collaborative study results demonstrate that the QuEChERS method is fit-for-purpose to monitor many pesticide residues in fruits and vegetables, and the Study Director recommends that it be adopted official first action.