Octadecylsilane chemically bonded silica is widely used in chromatography as a stationary phase, particularly in reversed-phase high-performance liquid chromatography (HPLC). Its hydrophobic surface makes it ideal for separating non-polar and moderately polar compounds, such as pharmaceuticals, environmental pollutants, and biological molecules. The material is also employed in solid-phase extraction (SPE) to purify and concentrate analytes from complex matrices like blood, urine, or environmental samples. Additionally, it finds applications in the analysis of fatty acids, steroids, and other lipophilic substances due to its strong retention of non-polar compounds. Its stability and reproducibility make it a preferred choice in analytical laboratories for precise and reliable separations.