Forensic toxicology applications of capillary electrophoresis (CE) coupled to electrospray ionization (ESI) time of flight (TOF) mass spectrometry

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Forensic science includes all the applications of science which can be used to support at any level the enforcement of the law. Moreover in many countries the term forensic science also includes the scientific knowledge on the basis of which news laws and rules are drafted (Tagliaro, 2006). Just limiting the attention to the analytical aspects of forensic science, an extremely wide application area is thus identified, including forensic toxicology, personal identification, identification of gunshot and postblast residues, investigation of the cause of fatal intoxications, fire and arson investigation, analysis of fibers and hairs, analysis of inks and paints, etc. Nowadays, classical analytical techniques such as gas chromatography (GC) or high performance liquid chromatography (HPLC), capillary electrophoresis (CE) has been used in the field of forensic analysis. In many new laboratories work has been started to explore the potential of CE and numerous application were published (Thormann, 2001). It is well known that Capillary Electrophoresis (CE) is the most powerful techniques for the separation of charged analytes, which, in principle, pose problems to both HPLC and GC. CE analyte separation, normally carried out in fused silica capillaries, is based on the different rates of migration of charged molecules in a buffer solution under the influence of an electrical field, which also generates an electroosmotic flow (EOF). Since longitudinal molecular diffusion and mass transfer restrictions encountered in liquid chromatography (LC) are not relevant in CE, the mass sensitivity and separation efficiency of CE is significantly better than LC. Moreover the use of mass spectrometry as detector for CE has increasingly gained acceptance, complementing or replacing conventional detection methods such as UV absorbance, electrochemical oxidation/reduction or fluorescence, which are less informative and also less universal. Over the past few years, considerable advances have been made in the development of interfaces, thus facilitating the transfer of analytes from the liquid phase of CE separation to the gas phase of MS analysis. Areas of still active research in CE include CZE, chiral separations, micellar electrokinetic capillary chromatography (MEKC), nonacqueous capillary electrophoresis (NACE), CE with chemiluminescence detection, capillary electrophoresis mass spectrometry (CE-MS), capillary electrochromatography (CEC) and “CE on a chip” technology. On the other hand, numerous applications using CE and CE-MS, clearly indicate that this technique CE is going to become a routine tool for the analysis of seized drugs, explosive analysis and gunshot residues, small ions of forensic interest, forensic DNA and RNA analysis, protein of forensic interest, ink analysis. A brief summary of CE and CE-MS applications to forensic drug analysis recently reported in the literature is presented below.