This stable-labeled internal standard is suited for quantitation of tocopheryl acetate by LC/MS or GC/MS Vitamin E testing applications such as quality control testing of Vitamin E fortified foods, dietary supplements, or pharmaceuticals. Tocopheryl acetate is a synthetic form of Vitamin E used as a fortifying agent, dietary supplement for Vitamin E in food or additive in vaping liquids. The U.S. Centers for Disease Control and Prevention (CDC) identified vitamin E acetate as very strong culprit of concern in the recent vaping related lung disease outbreak in the United States.