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Abstract :
[en] Synthetic cathinones (SCs) are phenylalkylamine compounds related to natural cathinone from Catha Edulis leaves. Given their structural similarities with amphetamines, these compounds are mainly drug of abuse. Indeed, these substances constitute the second most frequently seized group of new psychoactive substances and counted more than 130 compounds in Europe (EMCDDA 2016). In addition to be sold on the illegal market, some of them are currently available online using various brand names as “bath salts”, taking advantage of a legislative void. In this context, reliable analytical tools are required to track these substances.
The main objective of the present study was to develop a capillary electrophoresis separation method with laser induced fluorescence detection (CE-LIF) to analyze most frequently observed SCs. As these stimulants are frequently used as substitutes to these drugs, and especially in ecstasy, most common amphetamines were also included in the panel of 14 target analytes.
Due to their lack of native fluorescence, analytes were labeled using fluorescein isothiocyanate isomer I (FITC). Design of experiments strategy was performed to optimize the labeling process [1]. The FITC/analyte ratio, pH of reaction buffer and reaction time were selected as factors of the DoE. The objective was to maximize the peak intensity observed in CE while keeping an easy and fast protocol. Moreover, the estimation of process precision (i.e. repeatability and intermediate precision) was performed simultaneously by including triplicates of the central point during each day of DoE experiments.
Regarding the CE method, various BGE composition and additives were investigated in order to optimize the separation [2]. As non-ionic surfactants showed interesting selectivity, the development of a micellar electrokinetic capillary chromatography (MEKC) method was performed. The nature and concentration of non-ionic surfactants were deeply studied. The interest of polyethylene glycol ether surfactant was clearly demonstrated for the separation of these closely related compounds.
To conclude, a reliable labeling process was optimized thanks to DoE approach. Regarding the separation, the high resolving power of MEKC combined to the high sensitivity of LIF detection (pg/mL order) seemed to be an appropriate tool for the screening of both legal and illegal drugs
