Sample Treatment in Pesticide Residue Determination in Food by High-Resolution Mass Spectrometry: Are Generic Extraction Methods the End of the Road?

The use of high-resolution MS (HRMS) is becoming popular in laboratories for the determination of pesticide residues in food commodities. The recent improvements in the instrumentation have helped to increase the number of active compounds and transformation products that can be monitored within a simple chromatographic run. However, prior to instrumental determination, it is necessary to perform a nonspecific, or generic, sample treatment that allows the efficient extraction of several compounds with very relevant differences in their physical and chemical properties. In this sense, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and its several modifications and the "dilute-and-shoot" extraction methodology have already revealed an enormous potential for their use together with chromatographic techniques coupled to HRMS. The potentiality and limitations of such a methodological combination have been evaluated in terms of sensitivity and selectivity when they are applied to the analysis of complex food matrixes. An evaluation of the scope of the methods, in terms of efficiency of the extraction and ionization steps, as well as the matrix effect, has also been carried out. Different solutions for the matrix effect have been considered, including improvement in clean-up steps, sample dilution, and matrix compensation by matrix-matched calibration or by the use of isotopically labeled standards.