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Title: A research route in the actions against the abuse of psychotropic substances
Other Titles: New analytical tools for determination of drugs of abuse by means of Liquid Chromatography – tandem Mass Spectrometry
Tutor: Roberta, Curini
Keywords: Drugs of abuse
Mass Spectrometry
Issue Date: 15-Sep-2015
Abstract: The research route of this PhD started from workplace drug testing, an emerging need for safety and hygiene at work. The aim of the work consisted of developing and validating analytical methods: innovative tools for drug addiction monitoring and for illicit drugs testing. Different classes of psychotropic substances are examined in relation to their chemical and pharmacological effects, with a special focus on new psychoactive substances (NPS) and new trends of abuse. The most important biological matrices, suitable for analysis, are studied and the peculiarities of each matrix are highlighted. Analytical methods were developed for drugs determination in biological samples, such as human urine, plasma, oral fluids and hair. All these matrices are equally important for forensic purposes as they give different kind of information about the time of assumption and they show some distinctive features. Sample preparation is a critical step and is a key factor in determining the success of analysis: the task of chemist is to develop the best strategy to ensure that the system, consisting of 3 variables, matrix - target analytes - instrumental equipment, will be solved consistently with the ultimate purpose of the analysis. Therefore in this project appropriate sample preparation techniques have been investigated with special regard to each different matrix. The manual operations associated with these processes are often expensive, labor-intensive and time-consuming and affect the uncertainty of the final analytical data, for these reasons in this work new procedures based on innovative sample preparation were investigated and developed. The goal has been to provide short sample preparation times, automation of the clean-up step and low sample volumes, minimizing the consumption of solvents and chemicals. Development of methods based on liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) was a crucial component of this work. LC–MS is considered to be the benchmark for quantitative/qualitative bioanalysis, providing specificity, sensitivity and speed to the method. Different chromatographic conditions have been evaluated for the optimal separation and detection of the investigated compounds. As a new trend, the application of columns with superficially porous packing materials has been investigated, which allowed fast chromatographic runs and high efficiency. The versatility of the LC-MS/MS has been proven by providing a single analytical method for the determination of 11 drugs of abuse in biological fluids: conventional matrices, such as plasma and urine, and unconventional ones, such as oral fluids. The research route was then directed to hair analysis and for the first time pressurised liquid extraction (PLE) was shown to be effective for the extraction of drugs belonging to different classes from hair samples. Experiments were carried out to ensure correct interpretation of the analytical data by studying the phenomenon of external contamination (a critical point in the analysis of hair for forensic purposes). To improve the methods selectivity, multi reaction monitoring (MRM) acquisition modes were used for quantification of the investigated compounds in both cases. Finally analytical target was extended to NPS: a method for the screening of methylenedioxyamphetamine and piperazine-derived compounds in urine was developed. These substances, characterized by possessing common moieties, are screened using precursor ion and neutral loss scan mode and then quantified in MRM acquisition mode. All the methods developed have been validated according to specific international guidelines to ensure reliable results, unambiguously interpreted and useful for forensic purposes.

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