Diethyl phthalate acid ester in methanol certified reference material is primarily used for calibration and quality control purposes in analytical laboratories. It ensures the accuracy and precision of instruments like gas chromatographs and mass spectrometers when detecting and quantifying phthalates in various samples. This reference material is essential in environmental testing to monitor phthalate contamination in water, soil, and air. It also plays a critical role in the analysis of consumer products, such as plastics, cosmetics, and packaging materials, to ensure compliance with safety regulations. Additionally, it supports research studies focused on the impact of phthalates on human health and the environment.