High-Performance Liquid Chromatography (HPLC) is an advanced analytical technique used for the separation, identification, and quantification of compounds in complex mixtures, particularly in environmental chemistry. The principle of HPLC is based on the differential distribution of analytes between a mobile phase and a stationary phase under high pressure. When a liquid sample containing multiple components is introduced into a column packed with a stationary phase, each compound interacts differently with the stationary and mobile phases according to its polarity, molecular size, or affinity. These interactions cause the analytes to migrate at different rates, resulting in their separation. The efficiency of HPLC depends on the choice of stationary phase, composition of the mobile phase, flow rate, and temperature. The technique offers high resolution, sensitivity, and reproducibility compared to traditional liquid chromatography because it uses fine particles in the stationary phase and operates under high pressure to increase separation efficiency. The instrumentation of HPLC consists of several key components that work in an integrated manner. A solvent reservoir stores the mobile phase, which is a mixture of water, organic solvents, or buffers depending on the type of separation required. The solvent delivery system, or pump, generates the high pressure necessary to push the mobile phase through the column at a constant flow rate. A degasser is often included to remove dissolved gases that could form bubbles and interfere with the detector response. The injector introduces the liquid sample into the flowing mobile phase, ensuring minimal disturbance to the pressure and flow conditions. The heart of the system is the column, packed with stationary phase material such as silica particles modified with chemical groups