Aptamer functionalized magnetic metal–organic framework for effective extraction of aflatoxin B1 from grains prior to HPLC determination

Herein, a facile magnetic solid-phase extraction (MSPE) method was developed for the enrichment and separation of aflatoxin B₁ (AFB₁) using an aptamer functionalized magnetic metal–organic framework (Fe₃O₄@MOF-APT) as the adsorbent. The novel Fe₃O₄@MOF-APT combines the unique properties of AFB₁-specific aptamer, UiO-66-NH₂ MOF, and magnetic Fe₃O₄, enabling selective analyte recognition, excellent stability, and rapid separation capabilities. The adsorbent was structurally characterized using TEM, FTIR, XRD, UV–vis, and XPS techniques. MSPE parameters, including loading and elution volumes as well as extraction and elution times, were systematically analyzed and optimized. An enrichment factor of 20 was achieved, and Fe₃O₄@MOF-APT demonstrated good reusability, maintaining consistent recovery over 33 cycles. The analysis was conducted using HPLC coupled with post-column photochemical derivatization and fluorescence detection. The limit of detection for AFB₁ was 0.02 µg kg⁻¹, which is considerably lower than the established maximum residue limits. Quality control materials of AFB₁-contaminated grains were evaluated, and the results closely matched the certified values. The recoveries for AFB₁ determination in peanut, corn, rice, and wheat samples ranged from 89.7 % to 99.5 %. This study presents a viable strategy for the specific recognition, sensitive quantification, and cost-efficient analysis of AFB₁ in grains.