Ion transfer voltammetric and LC/MS investigations of the oxidative degradation process of fentanyl and some of its structural analogs

Abstract

Ion transfer voltammetry at a polarized ionic liquid membrane and LC/MS technique were used to investigate the oxidative time-resolved degradation of the frequently (mis)used opioid fentanyl and some of its structural analogs.The degradation is based on the reaction of opioids with hydroxyl radicals produced by the catalytic decomposition of hydrogen peroxide. Using the voltammetric technique, it was confirmed that the presence of Fe2+ions and hydrogen peroxide is essential in the degradation process of fentanyl(s). An increasing concentration of ferrous ions accelerates the described reactions, while the reaction rate is much less affected by the concentration of fentanyl.In an excess of ferrous ions, the course of the reaction can be approximated by a pseudo-first-order reaction with a half-time of 3.85 min. The generation of HO• radicals was proved to be the rate-determining step. Oxidative degradation processes of all investigated fentanyl-related drugs exhibit similar kinetics. A wide variety of fentanyl degradation products were detected and characterized using LC/MS analysis. Mono-, di- and trihydroxylated derivatives in several isomeric forms were observed most abundantly in a relatively short reaction time (5–30 min). The formation of norfentanyl has also been demonstrated.