Integrated Fe(III)-driven liquid-phase microextraction-spectrophotometry for selective and high-throughput detection of ethyl maltol in complex food samples.

Excessive addition of ethyl maltol (EMA) to foods poses potential health risks, highlighting the need for reliable monitoring. Herein, an integrated Fe(III)-driven liquid-phase microextraction (LPME)-spectrophotometry system was developed for selective and high-throughput EMA determination. Fe(III) in the acceptor phase served dual roles: as a chemical trap achieving >90% extraction efficiency and as an in situ chromogenic probe enabling direct detection. This unique design combines membrane-mediated matrix exclusion with coordination-assisted extraction, resulting in enhanced sensitivity and improved resistance to matrix interference. Density functional theory calculations revealed that Fe(III) facilitated the forward extraction by reducing the transmembrane transfer free energy barrier while suppressing back-extraction via weakening EMA-membrane solvent interactions. Under the evaluated conditions, the system offered a broad linear range (7.8-1500 μM, R2 > 0.999), low detection limit (0.67 μM), and satisfactory selectivity toward structural analogues. Validation in diverse food matrices yielded recoveries of 88-107% with good agreement with HPLC-UV (R2 > 0.99). The minimal solvent consumption, high throughput, and favorable greenness further highlight its practical utility. More than an EMA detection method, this work provides a proof-of-concept for the coordination-driven LPME strategy that intrinsically integrates sample preparation with in situ signal generation, offering new insights into the design of a mechanism-driven microextraction system.