LAUSR

BACKGROUND Residues of polar pesticides cannot be determined by QuEChERS-based multiresidue extractions because of their non-amenability to reverse-phase chromatographic separation and poor recoveries. On the other hand, single residue methods pose limitations because of the various requirements of sample preparation and LC-MS/MS conditions. A new multiresidue method is thus warranted for rapid and simultaneous analysis of polar pesticides. OBJECTIVE The study developed a multiresidue method for the simultaneous analysis of glyphosate and its metabolite (aminomethylphosphonic acid, AMPA), glufosinate and its metabolites (3-methylphosphinicopropionic acid and N-acetyl-glufosinate), ethephon, fosetyl-aluminum and its metabolite (phosphonic acid), and trimesium in grape and pomegranate by LC-MS/MS. METHODS The homogenized samples (10 g) were extracted with acidified methanol (20 mL). An aliquot of the extract was diluted with acetonitrile (1 + 1) and measured by LC-MS/MS using a Torus DEA column. The performance of a hydrophilic interaction liquid chromatography (HILIC) column and an "anionic polar pesticides" (APP) column was also evaluated. RESULTS The method performance on the Torus DEA column was satisfactory for all compounds (recoveries = 77-104%, repeatability-RSD, <11%) at LOQ (0.01 mg/kg), and higher levels in grape and pomegranate. The only exception was AMPA, which had an LOQ of 0.05 mg/kg. In the APP column, AMPA could be determined with an LOQ of 0.01 mg/kg. Trimesium, which had poor retention in Torus DEA, performed better in an XBridge HILIC column (retention time= 4.2 min, LOQ = 0.01 mg/kg). The inter-laboratory validation experiment yielded comparable results with high accuracy and precision. CONCLUSIONS The method could screen the residues of all compounds on a Torus DEA column. For AMPA and trimesium, the APP and XBridge HILIC columns provided superior method performances. Since isotopically-labelled internal standards were not required, the method appeared cost-effective. Considering its compliance with the SANTE/12682/2019 validation guidelines and EU-MRLs, the method can be recommended for regulatory testing purposes. HIGHLIGHTS A high-throughput residue analysis method targeting nine polar and ionic compounds in grape and pomegranate involved a single multiresidue extraction, followed by direct analysis using LC-MS/MS. A satisfactory method performance was achieved through intra- and inter-laboratory validation. The method sensitivity met the EU-MRLs and the SANTE/12682/2019 analytical quality control criteria.