Solid-phase extraction (SPE) is a technique used to separate and purify specific compounds from a mixture. It involves passing a liquid sample through a solid material, known as a sorbent, which selectively retains the target analytes while allowing unwanted substances to pass through. This process enhances the concentration of the desired compounds for further analysis. After the sample has been processed, the retained analytes are eluted, or washed off, from the sorbent using a suitable solvent. This method is widely used in various fields, including environmental analysis, pharmaceuticals, and food safety, due to its efficiency and ability to improve the quality of analytical results.