A certified reference solution and internal standard for quantification of desomorphine levels in urine or other matrices by LC/MS or GC/MS. This stable-labeled internal standard is suitable for opiate testing applications in clinical toxicology, forensic analysis, prescription monitoring, or urine drug testing. Desomorphine, most commonly referred to by its street name Krokodil, is a designer opiate and morphine derivative originally abused in Russia and other parts of Europe due to its ease of manufacture from codeine. Desomorphine was previously sold under the trade name Permonid as an opiate drug for treatment of pain.