β-Hydroxythiofentanyl-13C6 (hydrochloride) (Item No. 26218) is an analytical reference material intended for use as an internal standard for the quantification of β-hydroxythiofentanyl (Item Nos. 19736 | 17421) by GC- or LC-MS. β-Hydroxythiofentanyl is categorized as an opioid.1 β-Hydroxythiofentanyl-13C6 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.