Impurity C of Alfacalcidol is primarily relevant in the pharmaceutical industry, where it is monitored during the production and quality control of Alfacalcidol, a medication used to treat conditions related to calcium and bone metabolism, such as osteoporosis and renal osteodystrophy. The presence of this impurity is carefully regulated to ensure the safety, efficacy, and purity of the final drug product. Analytical methods, such as high-performance liquid chromatography (HPLC), are employed to detect and quantify Impurity C to comply with regulatory standards set by agencies like the FDA or EMA. Controlling this impurity is critical to maintaining the therapeutic integrity of Alfacalcidol and minimizing potential adverse effects in patients.