Electrophoretic methods in tubular microcompartments – forensic applications of capillary electrophoresis (CE) and CE coupled to mass spectrometry (MS)

Forensic science is a peculiar scientific discipline that includes all those scientific technologies and applications that are valuable to support the forensic investigation and/or to bring scientific evidence to court. On many occasions, forensic science provides also the information needed for drafting new laws and rules requiring scientific knowledge [1-3]. The main areas of this discipline are forensic toxicology, analysis of explosives, gunshot residues and chemical warfare, trace analysis (fibres, hairs, inks, dyes, glass etc.), and forensic genetics. For the latter area, which is based on DNA fragment analysis and sequencing, the development of capillary electrophoresis (CE) technology has been a fundamental step forward [4], being today a standard technique worldwide. In almost all its fields of application, the development of analytical forensic sciences finds two milestones: i. the introduction of chromatography and electrophoresis and ii., more recently, the introduction of mass spectrometric techniques. In both chromatography and electrophoresis, the miniaturisation of the separation compartment in a capillary format has highly increased the analytical efficiency and improved the possibility of coupling with mass spectrometry (MS). In the recent decades, CE proved to be a powerful analytical technique because of its excellent separation efficiency, high resolution and selectivity, short analysis time, low reagent consumption, sample volume and cost, and good recovery [5]. In particular, when performing enantioselective analyses, CE is known for being one of the most favoured separation techniques due to its numerous advantages listed above [6]. On these grounds, the major aims of the present doctoral research project were i. to improve and to develop analytical methods in CE for the stereoselective separations of NPSs (New Psychoactive Substances) and of drugs involved in dependence withdrawal therapy; ii. to couple CE with MS in order to improve analytical sensitivity and selectivity. With regards to i., a CZE (Capillary Zone Electrophoresis) method was developed for the chiral separation of ketamine and its major metabolite, norketamine, in hair specimens, in order to investigate potential chronic abuses in the context of traffic and workplace law enforcement. Moreover, an existing analytical method for the measurement of baclofen was further improved, being baclofen a drug that proved effective when administered to alcohol dependent patients in order to reduce the severe symptoms of sudden withdrawal from alcohol abuse. Last-but-not-least, CE, originally equipped with a UV detector, was coupled to a TOF (Time Of Flight) mass spectrometer with the purpose of taking advantage from the unique features of this mass spectrometry technique, i.e. possibility of acquisition of the “total ion current” without sacrificing sensitivity, possibility of re-processing of the raw data for post-analysis search of compounds, high speed of data acquisition. Moreover, since forensic toxicology involves complex biological matrices, the matrix effect was investigated with the aim of evaluating the possible advantages on ion suppression offered by a miniaturised separation technique, such as CE.