Microscale solid phase extraction of glyphosate and aminomethylphosphonic acid in water and guava fruit extract using alumina-coated iron oxide nanoparticles followed by capillary electrophoresis and electrochemiluminescence detection

A microscale solid-phase extraction (SPE) method using alumina-coated iron oxide nanoparticles (Fe3O4@Al2O3 NPs) as the affinity adsorbent for glyphosate (GLY) and its major metabolite aminomethylphosphonic acid (AMPA) in aqueous solution is reported. One milligram of Fe3O4@Al2O3 NPs was employed to extract both analytes in 5 ml of aqueous solution. After 5 min extraction, magnetic NPs were isolated from sample solution by employing an external magnet. Followed by rinsing the NPs with 5 μl of 20 mM Na4P2O7 solution for 5 min, the extract was directly analyzed using the derivatization-free CE-electrochemiluminescence (CE-ECL) method. With a sample-to-extract volume ratio of 1000, the enrichment factors for GLY and AMPA were 460 and 64, respectively. The limits of detection (LODs) were 0.3 and 30 ng ml−1 for GLY and AMPA in water, respectively. The developed method was applied to the analysis of GLY in guava fruit. The LOD of GLY in guava was 0.01 μg g−1. Total analysis time including sample pretreatment, SPE and CE-ECL was less than 1 h.