Evaluation of cleanup procedures in pesticide multi-residue analysis with QuEChERS in cinnamon bark

Cinnamon bark is a very complex spices matrix for pesticide residue analysis. In this study, two cleanup procedures, dispersive solid-phase extraction (d-SPE) and repetitive d-SPE, combined with Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) extraction were both investigated and applied for the determination of 60 pesticide residues in cinnamon bark by liquid chromatography - tandem mass spectrometry (LC-MS/MS) detection. The extraction solvents, phase partition salts, and cleanup sorbents were optimized. The results showed that 150 mg MgSO4 + 50 mg C-18 showed the best performance in d-SPE. The repetitive d-SPE achieved less matrix effects than d-SPE, but several high water-solubility analytes were lost during the cleanup, and also the 10 fold dilution compromised the sensitivities of analytes. With the validated QuEChERS-d-SPE method, 44 of 60 pesticides obtained satisfactory recoveries (71%-118%) and RSDs (2%-27%) at three to five spiking levels. The method was applied to monitor 15 market cinnamon samples.