Trioctylphosphine oxide is widely used as a solvent extraction agent in the separation and purification of rare earth metals. It plays a crucial role in the extraction of metals like uranium, thorium, and zirconium from their ores. Additionally, it is employed as a stabilizer and surfactant in the production of nanoparticles, particularly in the synthesis of quantum dots, where it helps control particle size and prevent aggregation. In the field of analytical chemistry, it is utilized as a complexing agent to enhance the detection and measurement of trace metals. Furthermore, it finds application in the formulation of lubricants and as an additive in fuel to improve performance and stability.