Description General description Isobutyryl fentanyl is a fentanyl analog and sold on the illicit market as a designer drug or in combination with heroin. This stable-labeled internal standard is suitable for quantification of isobutyryl fentanyl levels in urine or other matrices by LC/MS or GC/MS for clinical toxicology, forensic analysis, or urine drug testing applications. Legal Information CERILLIANT is a registered trademark of Cerilliant Corporation