On‐Chip Electromembrane Solid‐Phase Microextraction Using a Polypyrrole/Zirconium‐Based Metal–Organic Framework/Ti ₃ C ₂ T _<i>x</i> Titanium Carbide Composite Coating for the Determination of Phenoxyacetic Acid Herb

In this study, a miniaturized electromembrane-surrounded solid-phase microextraction (EM-SPME) device was integrated into a microfluidic chip. It was employed for the extraction of phenoxyacetic acid herbicides, including 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D), in environmental and food samples. The separation and determination of the analytes was performed by GC-MS. A nanostructured polypyrrole/zirconium-based metal-organic framework/Ti₃C₂T_x titanium carbide (MXene) fiber, synthesized electrochemically, was used as the acceptor adsorbent and also electrode. The simultaneous application of an electric field and nanocomposite-based adsorption enabled efficient preconcentration of the analytes within a compact and low-solvent system. Effective parameters on the extraction of the analytes were investigated and optimized. Under optimized conditions, the developed EM-SPME-GC-MS method exhibited limits of detection of 0.3 µg L^-1 for both analytes and linear ranges of 1-1000 µg L^-1 for MCPA and 2,4-D (R² ≥ 0.9934). Intraday and interday RSDs% were below 7.6% and 10.2% respectively, demonstrating satisfactory precision. The method was validated through real sample analysis in river water, cucumber, and rice extracts, achieving recoveries from 89% to 119%. The chip consumes 10 µL of 1-octanol as SLM and 250 µL of methanolic tetrabutylammonium bromide for derivatization per analysis (total < 0.26 mL organic solvent), which is markedly lower than conventional liquid-liquid extraction/solid phase extraction workflows.