Determination of fentanyl and acetylfentanyl in soil in their intact form and orthogonal corroboration of their presence by EI-GC-MS using chloroformate chemistry

In the field of forensic chemistry, methods for identifying and characterizing illicit drugs remain of great interest to government and law enforcement entities. To this end, the unambiguous identification of a drug in the environment (e.g., soil) prompts further investigation into the possibility of a clandestine point of production for such drug. In this report, a method for the analysis of the two common synthetic opioids fentanyl and acetylfentanyl in a soil matrix when present separately at 1 and 10 μg/g by electron ionization gas chromatography-mass spectrometry (EI-GC-MS) is presented. The method involves the initial extraction of the intact opioids followed by their reaction with 2,2,2-trichloroethoxycarbonyl chloride (Troc-Cl) to predictably generate Troc-modified norfentanyl, Troc-noracetylfentanyl and 2-phenylethyl chloride products that can be used to retrospectively corroborate the identity of the opioid by EI-GC-MS. Estimated method detection limits (MDLs) for the Troc-norfentanyl and Troc-noracetylfentanyl species were 15.4 and 13.6 ng/mL respectively from the soil matrix extracts employed (Virginia type A soil) while the calculated method’s LOQ values were 45.7 and 40.4 ng/mL respectively. The protocol presented herein describes for the first time the analysis of these highly toxic and common synthetic opioids in a soil matrix as well as their retrospective confirmation by analyzing the products arising from their reaction with Troc-Cl by EI-GC-MS.