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Title: Development of novel extraction methodologies for the determination of illicit drugs in biological matrices
Tutor: Curini, Roberta
Issue Date: 20-Dec-2013
Abstract: Sample preparation is a critical step in bioanalytical methods and is a key factor in determining the success of analysis. The aim of this work was to investigate and develop new techniques to address some of the shortcomings of current sample preparation techniques in forensic analytical chemistry. The goal has been to provide automation of the clean-up step, short sample preparation times, increasing selectivity and low sample volumes minimizing the consumption of solvents and chemicals. The developed procedures were intended for use with biological samples, such as human urine, plasma, serum, 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. Therefore in this project appropriate sample preparation techniques have been investigated with special regard to each different matrix. Biological samples are complex matrices which often need an effective clean-up step before analysis to reduce the levels of possible interfering substances from the matrix, especially if the analytes are present at trace levels. Conventionally, liquid–liquid extraction (LLE), protein precipitation (PP) and solid-phase extraction (SPE) are used as sample preparation techniques. The manual operations associated with these processes are often labor-intensive and time-consuming, for these reasons in this work we have investigated and developed new procedures based on innovative sample preparation. New selective stationary phases for SPE based on hexapeptides were developed while miniaturized SPE techniques such as microextraction on packed sorbent (MEPS) and µ-SPE were investigated for the analysis of urine, plasma and oral fluids; finally 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. Development of methods based on liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS) was also 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 fused core columns has been investigated, which allowed fast chromatographic runs and high efficiency. To improve the method selectivity multi reaction monitoring (MRM) acquisition modes were used for quantification of the investigated compounds. All the methods developed have been validated according to international guidelines.

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