Ionogel based material for the colorimetric detection of Δ9-tetrahydrocannabinol

Cannabis sativa is the most widely abused illegal drug in the world. On the other hand, there is an increasing interest in the production of non-psychoactive industrial hemp for several applications, including the production of cannabidiol (CBD). This makes the easy and fast in situ detection of Δ9-tetrahydrocannabinol (THC), the illicit, psychoactive molecule that characterises drug-type cannabis a pressing need. It is here where detection mechanisms based on novel methodologies, e.g. microfluidics devices and new materials, offer interesting approaches that reduce reagents consumption and that minimise the generation of waste during the process. Moreover, fast analysis times and portability are of great importance to generate useful devices. Portability can be improved by using solid matrixes, where the detection mechanism could take place, such as an ionogel. In this work, we report for the first time the use of an ionogel matrix for the colorimetric detection of THC through the Fast Blue B Salt method. The integration of the Fast Blue B Salt into the ionogel matrix was studied as a first step in the development of a fully integrated sensor, for the identification of THC from hemp biomass and extracts.

I. Introduction

The consumption of illicit drugs is a safety and health concern worldwide, among all the drugs of abuse, cannabis is the most consumed [1]. Additionally, the increase in the use of hemp for industrial purposes makes imperative the development of easy and affordable techniques for the detection of ∆9-tetrahydrocannabinol, the main psychotropic component of drug-type cannabis. Therefore, there is a growing need to be able to distinguish between industrial hemp (THC < 0.3 %) and marijuana [2]. The detection of cannabinoids, including THC [3] has been performed using many techniques such as gas and liquid chromatography [46] that can reach very low detection limits (up to 0.01 ng mL¹) [7]. Nevertheless, in order to simplify the detection method, colorimetric assays have been also developed, which require less bulky and inexpensive type of equipment. For instance, the Fast Blue B Salt (FBBS) method, which consists on the nucleophilic attack of the lone pare electrons from the phenolic group of the THC to the azo group from the salt, is very specific for cannabinoids [8]-[10]. However, additional analysis, are required to distinguish between THC and other cannabinoids present in the sample [11].