Evaluating the selectivity of colorimetric test (Fast Blue BB salt) for the cannabinoids identification in marijuana street samples by UV–Vis, TLC, ESI(+)FT-ICR MS and ESI(+)MS/MS

Abstract

Marijuana is one of the most marketed illicit drugs in the world. Originated from Cannabis sativa L, Δ9-tetrahydrocannabinol (or Δ9-THC) is proscribed in Brazil by the law number 11.343 from August 23rd of 2006 as well as its isomers, salts, ethers and esters. However, Δ9-THC is the main responsible for the hallucinogenic effects of the plant. The principal screening test used by the Brazilian Forensic Police is a colorimetric test called Fast Blue B or BB salt, in which the development of a reddish color in a basic medium indicates the presence of cannabinoids such as Δ9-THC, cannabinol (CBN) and/or cannabidiol (CBD). However, a better understanding of this chemical reaction is required. In this work, the products of the colorimetric test were identified by positive-ion mode electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI(+)FT-ICR MS), collision-induced dissociation (CID) experiments or ESI(+)MS/MS, ultraviolet–visible (UV–Vis) spectroscopy and thin layer chromatography (TLC). A chemical structure was proposed for the product of the reaction (m/z 626) formed by Fast Blue BB salt (4-amino-2,5-diethoxybenzanilide diazotated zinc double salt) and Δ9-THC molecule. Besides, the selectivity of the colorimetric test was evaluated in presence of interferences from other plants such as Jacaranda decurrens Cham and Paullinia cupana Kunth.