Hydroxychloroquine Impurity E is primarily used in the development and quality control of pharmaceutical products, specifically those containing hydroxychloroquine. It serves as a reference standard in analytical testing to ensure the purity and consistency of the active pharmaceutical ingredient (API). By identifying and quantifying this impurity, manufacturers can comply with regulatory requirements and maintain the safety and efficacy of hydroxychloroquine-based medications. Additionally, it aids in research and development efforts to understand the degradation pathways and stability of the drug, contributing to improved formulation and storage strategies.