Thin-Film Agarose Xerogel Membranes Enable Integrated Electromembrane Extraction and Electrocoagulation

Gel electromembrane extraction (G-EME) using agarose gel membranes is a green and effective approach for the selective transport of ionic analytes. However, its application is often limited by electroendosmotic flow (EEO) and the poor mechanical stability of agarose hydrogel membranes, particularly when combined with an organic solvent-based protein removal method for protein-rich samples. In this work, an electric-field-induced integration of selective ionic transport and protein electrocoagulation is introduced using a thin-film xerogel that combines electromembrane extraction and protein electrocoagulation into a single analytical step. Conversion of the hydrogel into a xerogel produces a mechanically robust, low-water-content membrane with reduced thickness, which suppresses EEO while still allowing efficient electromigration of charged analytes. The improved stability of the xerogel membrane permits operation at elevated electric fields sufficient to induce in situ protein electrocoagulation, thereby disrupting protein−drug binding and providing simultaneous matrix cleanup during extraction. The developed method offers a broad linear range (1−100 ng mL−1), acceptable precision (<11% (intra-day) and <12% (inter-day)), low limits of detection (0.3 ng mL−1), low limit of quantification (1 ng mL−1), extraction efficiency up to 88%, and enrichment factor up to 44. Norfloxacin and ciprofloxacin were extracted directly from milk samples and quantified by HPLC-UV with an accuracy of 78−110%. These results demonstrate that a thin-film agarose xerogel membrane provides a simple and effective platform for suppressing EEO and integrating extraction with electrocoagulation, enabling robust EME of antibiotics from protein-rich food matrices.