Used primarily as a reference standard or impurity marker in the quality control of thioctic acid (alpha-lipoic acid) pharmaceutical formulations. Helps in detecting and quantifying impurities during synthesis, purification, and stability testing of active pharmaceutical ingredients. Employed in analytical methods such as HPLC and GC to ensure drug purity, safety, and compliance with regulatory standards. Also useful in studying degradation pathways of thioctic acid under various storage or processing conditions.