High-Performance Liquid Chromatography (HPLC) is an advanced analytical technique widely used in environmental chemistry for the separation, identification, and quantification of compounds present in complex environmental samples such as water, soil, and air. The principle of HPLC is based on the differential partitioning of components between a stationary phase and a mobile phase. Compounds in a mixture interact differently with the stationary phase, which can be polar or non-polar, leading to their separation as they pass through the column carried by the mobile phase, usually a liquid solvent or mixture of solvents. The separation efficiency depends on the chemical nature of the analytes, the composition and flow rate of the mobile phase, the type of stationary phase, temperature, and pressure applied during the process. HPLC operates under high pressure to increase the speed and resolution of separation compared to traditional liquid chromatography. This high pressure forces the mobile phase through a column packed with finely divided stationary phase particles, resulting in sharper peaks and better separation of compounds even at very low concentrations. Depending on the nature of the sample and analytes, different modes of HPLC can be employed, including normal-phase HPLC, reversed-phase HPLC, ion-exchange HPLC, and size-exclusion HPLC. In environmental chemistry, reversed-phase HPLC is most commonly used because many environmental pollutants,