Multiresidue Pesticide Analysis in Cereal Grains Using Nanosized γ-Aluminum Oxide as Effective Purification Material

This study demonstrated the application of nanosized γ-aluminum oxide as dispersive solid-phase extraction (d-SPE) sorbent to pesticides multi-residue analysis in cereal grains by gas chromatography combined with orbitrap mass spectrometry (GC-Orbitrap-MS). The influence of structural phase, particle size, and usage amount of nanosized aluminum oxide were investigated on d-SPE cleanup performance. The ability of nanosized γ-aluminum oxide to clean up interfering substances from ethyl acetate extracts of cereal grains was also evaluated. Compared with common d-SPE sorbents (i.e., primary secondary amine (PSA), basic alumina, neutral alumina, acidic alumina, octadecylsilane (C18), florisil, graphitized carbon black (GCB), and nanosized ferroferric oxide (Fe3O4)), 10 nm γ-aluminum oxide was cost-effective and exhibited much better cleanup performance with 99.72% removal of eluting matrix components for wheat kernel. Meanwhile, a multiresidue method was validated on 24 representative pesticide residues in three cereal grains (wheat kernel, rice, and corn). Acceptable average recoveries of 71.1-117.0% and relative standard deviations (RSDs) < 12.7% were obtained for all target pesticides. The method met the 5-10 μg L-1 limit of detection and 10-20 μg kg-1 limit of quantification. The results indicated that 10 nm γ-aluminum oxide represented an affordable and effective d-SPE adsorbent for pesticides multiresidue analysis in cereal grains.