para-Fluorobutyryl fentanyl-13C6 (hydrochloride) (Item No. 26216) is intended for use as an internal standard for the quantification of para-fluorobutyryl fentanyl (Item Nos. 19826 | 17049) by GC- or LC-MS. para-Fluorobutyryl fentanyl is structurally similar to known opioids. It has been associated with fatal overdoses.1 para-Fluorobutyryl fentanyl-13C6 (hydrochloride) is regulated as a Schedule I compound in the United States. This product is intended for research and forensic applications.WARNING This product is not for human or veterinary use.