Magnetic dispersive micro solid-phase extraction and gas chromatography determination of organophosphorus pesticides in strawberries

Magnetic nanoparticles (MNPs) with different sizes and characteristics were synthesized to be used as a QuEChERS sorbents for the determination of seven organophosphorus pesticides (OPPs) in strawberries by gas chromatography analysis with flame photometric and mass spectrometry detection. To achieve the optimum conditions of modified QuEChERS procedure several parameters affecting the cleanup efficiency including the amount of the sorbents and cleanup time were investigated. The results were compared with classical QuEChERS methodologies and the modified QuEChERS procedure using MNPs showed the better performance. Under the optimum conditions of the new methodology, three spiking levels (25, 50 and 100 μg kg-1) were evaluated in a strawberry sample. The results showed that the average recovery was 93% and the relative standard deviation was less than 12%. The enrichment factor ranged from 111 to 145%. The good linearity with coefficients of determination of 0.9904-0.9991 was obtained over the range of 25-250 μg kg-1 for 7 OPPs. It was determined that the MNPs have an excellent function as sorbent when purified even using less amount of sorbents and the magnetic properties allowed non-use of the centrifugation in cleanup step. The new methodology was applied in strawberry samples from conventional and organic farming. The new sorbents were successfully applied for extraction and determination of OPPs in strawberries.The authors would like to thank technical assistance of Rui Rocha from Centro de Materiais da Universidade do Porto (CEMUP) for the SEM images, Aurora Silva from REQUIMTE/LAQV and Instituto Superior de Engenharia/Instituto Politécnico do Porto for FTIR analysis and Paula Paíga from REQUIMTE/LAQV for the graphical abstracts design. This work received financial support from the European Union (FEDER funds through COMPETE) and National Funds (FCT) through project UID/QUI/50006/2013 from the European Union (FEDER funds) under the framework of QREN through Project Qualidade e Segurança Alimentar – Uma abordagem (nano)tecnológica”, reference NORTE-01-0145-FEDER- 000011. Virgínia Cruz Fernandes and Maria Freitas are grateful to FCT (Fundação para a Ciência e a Tecnologia) for the Postdoc grant (SFRH/BPD/109153/2015) and PhD grant (SFRH/BD/111942/2015) respectively.