Used primarily as a reference standard in pharmaceutical quality control and analytical testing during the manufacturing and purification of afatinib, a tyrosine kinase inhibitor. It helps in identifying and quantifying impurities in the final drug substance to ensure product purity, safety, and regulatory compliance. Also utilized in stability studies to monitor degradation pathways of afatinib under various storage conditions. Its presence is closely monitored to maintain consistent therapeutic efficacy and minimize potential toxic side effects in the final dosage form.