Inner-wall biochar-coated pipette tip microextraction for rapid and sustainable determination of tyrosine kinase inhibitors in plasma

Tyrosine kinase inhibitors (TKIs) are critical in cancer therapy, but their clinical application is complicated by narrow therapeutic windows and significant interpatient variability in pharmacokinetics. To address this, this study presents an effective pipette-tip solid-phase microextraction (PT-μSPE) method using kapok fiber-derived biochar (KFB) as a green and cost-effective sorbent for the extraction of TKIs in plasma. The KFB was incorporated as an inner-wall coating within a standard pipette tip, minimizing backpressure and enhancing automation compatibility. This PT-μSPE method is optimized for efficiency and sensitivity, with ethanol used as the desorption solvent. The method is coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the determination of TKIs, demonstrating excellent linearity (R 2 > 0.99), sensitivity (LOD: 0.022-0.125 ng mL-1), and reproducibility. Furthermore, the method exhibits notable green chemistry characteristics, including minimal solvent usage and environmental sustainability. The proposed method offers a practical, scalable solution for TKI quantification for potential clinical and pharmacokinetic studies, with potential for high-throughput integration into automated systems.