Accurate Determination of Pesticide Residues in Milk by Sonication-QuEChERS Extraction and LC-LTQ/Orbitrap Mass Spectrometry

A modified, quick, easy, cheap, effective, rugged, and safe (QuEChERS) extraction procedure combined with sonication and Ultra-High Performance Liquid Chromatography-Orbitrap-Mass Spectrometry (UHPLC-Orbitrap-MS) was developed as a sensitive and reliable methodology for the determination of multiclass pesticides in full-fat milk. Different amounts of EMR-lipid sorbent were assayed for the cleanup step in order to achieve both acceptably high recoveries and low co-extractives in the final extracts. Accurate mass measurements of the analyte's pseudo-molecular ions and tandem MS fragmentation were used to quantify and identify the target pesticides. Analytical performance characteristics of the method, such as linearity, recovery, precision, the limit of detection (LOD) and quantification (LOQ), matrix effects (ME), and expanded uncertainty, have been determined for method validation fulfilling all criteria for its use as a validated routine method. The method was successfully applied to real samples (by local farms and commercial), revealing the presence of carbendazim in one milk sample at a concentration level below the maximum residue limits.

Automated summary

A modified QuEChERS extraction procedure combined with sonication and UHPLC-Orbitrap-MS was developed for the determination of multiclass pesticides in milk. The method achieved high recoveries and low co-extractives by using different amounts of EMR-lipid sorbent for cleanup. Accurate mass measurements and tandem MS fragmentation were used for quantification and identification of target pesticides. The method was validated for routine use and successfully applied to real samples, revealing the presence of carbendazim below the maximum residue limits in one milk sample.