Automated offline µ-SPE cleanup in GC-based multi-residue analysis: overcoming the challenges of fatty acid containing matrices

The aim of this work was to investigate and optimize the use of offline automated µ-SPE cleanup for the analysis of GC-amenable pesticides in fatty acid containing matrices, such as wheat and linseeds. The manual d-SPE and the automated µ-SPE procedures were compared in terms of analytical performance. Furthermore, different cartridge compositions, loading volumes and elution rates were tested and compared in order to find the best conditions for the cleanup of highly complex QuEChERS raw extracts. In µ-SPE, the key aspect was the PSA capacity for the removal of fatty acids and prevention of overloading. The novelty of this research lies in the use of customized µ-SPE cartridges containing higher amounts of PSA, which proved to be the most effective strategy for minimizing matrix effects and enhancing the method robustness. The extracts obtained were cleaner compared to d-SPE, and the addition of analyte protectants (shikimic acid) was required to prevent the adsorption of certain analytes in the GC system. The final µ-SPE workflow provided an efficient and reliable cleanup step for testing highly complex extracts rich in fatty acids and improved GC robustness, reducing the need for GC-MS maintenance.