Solid-Phase Extraction (SPE) is a sample preparation technique used to separate and concentrate specific compounds from a mixture. It involves passing a liquid sample through a solid adsorbent material, which selectively retains the target analytes while allowing unwanted substances to pass through. This process enhances the purity and concentration of the desired compounds for further analysis. After the target analytes are retained, they can be eluted from the solid phase using a suitable solvent. This step allows for the collection of the concentrated compounds, making SPE a valuable method in various fields, including environmental analysis, pharmaceuticals, and food safety.