Challenges in the identification of new thermolabile psychoactive substances: The 25I-NBOH case.
Ana Flávia Belchior de Andrade, Mathieu Elie, Christian Weck, Jorge Jardim Zacca, Mônica Paulo De Souza, Luíza Nicolau Brandão Caldas, Jose Gonzalez-Rodriguez
Forensic science international July 1, 2020 DOI: 10.1016/j.forsciint.2020.110306 via PubMed
Summary
The drug 25I-NBOH, a new psychoactive substance (NPS), breaks down in the hot injector of a gas chromatograph-mass spectrometer (GC-MS), a common forensic tool, creating misleading byproducts. The main breakdown product is 2C-I, with a smaller amount of an ortho-phenolic benzyl ether (o-PBE) whose exact form depends on the solvent used. Adjusting the injector temperature, split ratio, or flow rate did not prevent this thermal degradation. Thermal analysis showed that 25I-NBOH has a narrow temperature range between melting and decomposing, making it unstable. Derivatization successfully prevented the degradation, allowing accurate GC-MS analysis.
Study at a glance
| Characteristics | Experimental study Peer reviewed |
|---|---|
| Keywords | 25i-nboh Derivatization Nps Thermal degradation |
| Citations | 8 |
| Key finding | Derivatization prevents the thermal degradation of 25I-NBOH during GC-MS analysis, while adjustments to injector temperature, split ratio, and flow rate do not. |
Abstract
The continuous emergence of NPS over the last years poses a series of novel challenges for forensic analysts. Most of those new compounds are synthesized with minimal chemical modifications to the structure of already known chemicals in order to avoid regulations. Some of these new compounds may undergo chemical changes during analysis leading to misidentification and detrimental legal consequences. GC-MS is one of the most widely used analytical techniques employed by forensic laboratories all over the world for drug analysis. Nevertheless, thermolabile NPS, such as 25I-NBOH can generate artefacts in the traditional GC-MS analysis. In this paper, we describe the fragmentation mechanism of the 25I-NBOH into a major peak corresponding to 2C-I and a minor one corresponding to the associated ortho-phenolic benzyl ether (o-PBE), which exact identity is directly linked with the solvent used for the analysis. Also, a series of method adjustments is displayed, encompassing variation on the injector temperature, split ratio and flow ratio, although with no success to prevent 25I-NBOH thermo degradation in the GC injector. Furthermore, differential scanning calorimetry and thermogravimetric analysis demonstrated that 25I-NBOH's thermal stability is due to a smaller temperature window between fusion and decomposition points. Finally, we perform derivatization experiments and demonstrate how to overcome 25I-NBOH degradation in the GC/MS analysis.