Development of new technologies for the selective removal of volatile compounds with applications in forensic science and natural aromas

Tese de doutoramento, Farmácia (Química Farmacêutica e Terapêutica), Universidade de Lisboa, Faculdade de Farmácia, 2015

The increasing awareness on the environmental problems, led to an increasing demand of “greener” processes in the several fields of science, focusing mainly in solvent-free processes. We find two good examples in both forensic toxicology and natural compounds extraction fields, where solvents are still widely used. In the last twenty years hair has gained great relevance as a toxicological sample, namely in the field of drugs of abuse. Although this matrix allows the detection of such compounds after weeks, months and even years (in same cases), it requires a precleaning step (decontamination) in order to ensure the absence of drugs at the hair surface. Despite the existence of several decontamination strategies, none ensures the absence of drug at the hair surface. On the other, in the field of the extraction of natural compounds, it has been observed a rising demand for more selective, environmentally friendly, and cheaper extraction techniques that can be industrially applied. In these contexts, the non-volatility of ionic liquids (ILs) makes them almost ideal systems for the sorption of compounds. In literature it is possible to find already some applications of these liquids, namely in the adsorption of dioxins. We hereby present the development of new technologies for the selective removal of volatile compounds, applied to forensic toxicology (hair testing, using ILs) and to natural aromas (essential oils, without using ILs). We started to apply the ILs to the decontamination of hair samples containing opiates at the surface. More than forty ILs were screened (100 ºC, 96h) and the liquid 1- ethanol-3-methylimidazolium tetrafluoroborate, [C2OHMIM][BF4], showed very promising results (extraction efficiency > 80%). In order to reduce the extraction time to less than 24h, the process was optimized by means of Design of Experiment (DOE), and the final experimental conditions were 120 ºC, 16 h and a water content of 44% (w/w). The method was then compared with Cairns method (a common and very time-consuming decontamination strategy) and the results showed that the developed method yielded, in average, slightly better results (% difference ~5%). The method was then applied to both cocaine and cannabinoids. In the case of cocaine, the temperature led to the spontaneous hydrolysis of cocaine into its metabolite benzoylecgonine (BZE). Unfortunately, we were not able to remove BZE from the hair surface and no explanation for this phenomenon was found. As for the cannabinoids, the ILs screening revealed a great affinity to these compound (extraction efficiency > 90%). Once more the liquid [C2OHMIM][BF4] was chosen and the method was optimized for the cannabinoids extraction, and its final conditions were 100 ºC and 13 h. When compared with the Cairns decontamination, our method showed higher extraction efficiency. The developed decontamination procedure was then rationalized in order to fully understand the phenomenon. A three steps model was assumed: transport of the drugs to IL gas-liquid interface, adsorption onto the liquid free surface and absorption into the bulk liquid. Quartz crystal microbalance (QCM) experiments, as well as surface tension measurements were performed to evaluate the proposed model. The results confirmed that the water vapor enhances the transport of the drugs (due to solubilization). Additionally, using Kamlet-Taft parameters to characterize the polarity of ILs, we concluded that the cations with the highest acidity and lowest basicity parameters are the most efficient in the removal of the drugs from hair. The second part of the work involved the development of a new technology to selectively extract volatile compounds from botanicals. Using Eucalyptus globulus leafs as a model, a new extraction technique based on the vapor pressures was developed. In this particular case we found no need to use ILs. The method was optimized by mean of DOE and the optimum conditions were: 50 ºC, a nitrogen flow rate of 0.15 l/min , during 2.36 h. The vapor should be condensed at -10 ºC. Under these conditions the extraction yield was of 6.11 % (w/w). The method was further applied to both Lavandula dentata and Rosmarinus officinalis. The results showed not only the removal of the more volatile compounds (as expected), but also high extraction yields (7.23 % and 4.28 %, respectively).

Fundação para a Ciência e a Tecnologia (FCT), SFRH/BD/73228/2010