Validation of the Capillary Electrophoresis Method for the Forensic Ink Analysis

Joanna Mania1, Xiaoma Xu2, Paweł Kościelniak1, 3


Capillary electrophoresis (CE) is probably the most interesting analytical technique which appeared in recent years. In CE, electrophoresis and/or electrokinetic separations are carried out in tiny capillaries at high voltages (10-30kV), thus achieving high efficiency and resolution power. The main characteristics of CE are versatility of application (from inorganic ions to large DNA fragments), use of different separation modes with different selectivity, low demands on sample volume, negligible running costs, possibility of interfacing with different detection systems and ruggedness and simplicity of the instrumentation.

Applications of CE to the forensic sciences are now rapidly growing. The primary function of the forensic scientist is to provide analysis of evidence and expert testimony to be used in legal proceedings. The method used in forensic science must be reliable and provide information that is unequivocal. Therefore the validation of analytical method used in forensic laboratories is extremely important.

In the Netherlands Forensic Institute, Rijswijk, Holland, an original CE ink analysis method was developed for forensic comparison and distinguishing inks. It is suitable for analyses of glycol-, solvent- and water-based writing and printing inks. The present poster shows the basic principles of the CE method validation and presents results from the validation of the CE ink analysis method. The goal of performed experiments was to validate this method and to establish the general criteria for distinguishing between inks based on electropherograms of ink extracts from paper. The robustness, reproducibility, selectivity and sensitivity of the method were investigated. Also the general quality control procedures were proposed. It was proved that the CE ink analysis method is stable and the obtained results are reproducible. The CE ink analysis method for the ink comparison is reliable and can be recommended for case analysis.

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