Norfentanyl d5

The primary reference materials for fentanyl, norfentanyl, acetyl fentanyl, acetyl norfentanyl, and their respective internal standards (ISTD) fentanyl-d₅, norfentanyl-d₅, acetyl fentanyl-¹³C₆, and acetyl norfentanyl-¹³C₆ were purchased from Cerilliant (Round Rock, Texas). Ammonium formate, ammonium hydroxide, glacial acetic acid, isopropanol, methylene chloride, methanol, sodium phosphate monobasic, sodium phosphate dibasic and deionized (DI) water were purchased from Fisher Scientific (Hanover Park, Illinois). All reagents were ACS grade or better. SPEC® MP3 solid phase extraction (SPE) columns were purchased from Agilent Technologies, Inc, (Santa Clara, California). Medical grade nitrogen was purchased from National Welders Supply Company (Richmond, Virginia). Drug-free expired whole blood was obtained from Transfusion Medicine Laboratory at Virginia Commonwealth University Health System. The blood was certified drug free by screening for alkaline extractable drugs by GC/MS and UPLC/MS/MS prior to use.

Optima LC–MS grade methanol, acetonitrile, water, ammonium acetate, ammonium formate, and formic acid were purchased from Fisher Scientific (Hampton, NH) and used as received unless otherwise specified. Synthetic urine (Sigmatrix Urine Dilutent) was purchased from Millipore Sigma (Saint Louis, MO). All opioid and metabolite standard solution aliquots were purchased from Cerilliant (Round Rock, TX) and diluted to their stock concentrations in compatible solvents (methanol or acetonitrile). Deuterated internal standards (buprenorphine-d₄, dihydrocodeine-d₆, fentanyl-d₅, methadone-d₉, norbuprenorphine-d₃, norfentanyl-d₅, and oxycodone-d₆) methanol solution aliquots were also purchased from Cerilliant (Round Rock, TX). Working stock solutions were prepared to a concentration of 2.5 μg/mL for all opioids and metabolites examined in this study. For flow-injection analysis, all working stock solutions were diluted to a concentration of 500 ng/mL in LC–MS grade water.