Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2009
Publication Date: 5/26/2010
Citation: Mastovska, K., Dorweiler, K., Lehotay, S.J., Wegscheid, J.S., Szpylka, K.A. 2010. Pesticide Multiresidue Analysis in Cereal Grains Using Modified QuEChERS Method Combined with Automated Direct Sample Introduction GC-TOFMS and UPLC-MS/MS Techniques. Journal of Agricultural and Food Chemistry. 58:5959-5972. Interpretive Summary: Monitoring of pesticide residues in food commodities and products has become an essential part of the food safety control. Because of the high number of potentially used pesticides and the variety of food samples, regulatory agencies and other food testing laboratories need wide-scope, effective, rapid, and reliable analytical methods for pesticide residue analysis. A previously reported sample preparation method for the multiresidue analysis of pesticides in fruits and vegetables was modified to provide good analytical results for cereal grains. The sample preparation method was combined with state-of-the-art instrumentation, which enabled fast and sensitive analysis and inclusion of a larger number of pesticides. As opposed to the traditional approach, the new method also offers significantly improved sample throughput and substantial reductions in solvent waste and overall cost of the analysis.
Technical Abstract: The QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation method was modified to accommodate various cereal grain matrices (corn, oat, rice and wheat) and provide good analytical results (recoveries in the range of 70-120% and RSDs <20%) for the majority of the target pesticides (about 180 analytes). The method consists of 1-hour shaking of a milled sample (2.5-5 g) in 20 mL of 1:1 (v/v) water-acetonitrile (or 25 mL of 1.5:1 water-acetonitrile in the case of rice) to provide simultaneous matrix swelling and analyte extraction. Then, a MgSO4:NaCl salt mixture (4:1, w/w) is added to the extract to induce phase separation and force the pesticides into the upper acetonitrile layer, a 1 mL aliquot of which is subsequently cleaned up using dispersive solid phase extraction with 150 mg PSA, 50 mg C18, and 150 mg MgSO4. GC-amenable pesticides were analyzed using gas chromatography combined with time-of-flight mass spectrometry (GC-TOFMS) and the automated direct sample introduction technique for a large volume injection of the extracts. Ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (UPLC-MS/MS) was employed for the analysis of LC-amenable pesticides. This method was implemented in a routine laboratory, providing about 3-fold increased sample throughput, 40-50% reduction in the cost of disposable materials and in the operation costs, 1:100 solvent waste reduction, and increased scope of the analysis vs. the traditional approach based on the Luke method.