Towards an efficient and sustainable technique: A review on the preparation and synthesis of sorbents for in-tube solid-phase microextraction

Microextraction techniques are increasingly valued for their low sample requirements and consistency with green chemistry principles. Over time, several formats have been developed, enabling faster and automated analytical workflows. Among them, in tube-solid phase microextraction (IT-SPME) stands out as a powerful sample preparation technique, offering direct online coupling with chromatographic systems, automation, and reduced solvent use. This review critically examines the main strategies for IT-SPME sorbent fabrication, including fiber-filled, monolithic, coated, and particle-packed capillaries. Emphasis is set on the underlying chemistry of sorbent synthesis, radical polymerization, sol-gel processes, hydrothermal reactions, and click chemistry, while assessing efficiency, scalability, and environmental impact. Challenges such as complex syntheses, hazardous reagents, and artisanal protocols are discussed. The review offers the analytical community a practical guide to reproducible and sustainable strategies for developing IT-SPME devices that are well-suited to automated workflows.