Chromatography Identification Of The Pen In The Ink Types

Forensic science often relate to questioned documents and require to exame the date of writing ink. Since 1950's, forensic scientist of all countries has taken great effort to study and establish many analytical techniques used in law cases, some analytical ways are accepted by many justice branch. But until now, questioned documents and dating writing inks is one of difficult problem in forensic science due to the complex composition and detection interfere of ink. So the study on the separation of pen inks by chromatography is more significant for forensic science. The paper included four parts:Chapter one introduced the development history , the major components of inks and the theory foundation, summarized the recent advance of questioned documents and dating writing inks, including chemical identify, solvent extraction, chromatogram analysis, spectroscopic analysis.Chapter two systematical analyzed on the blue ball point writing inks with high performance liquid chromatography (HPLC), selected proper extractor and mobile phase, studied the reproducibility, detector limit and the effect of different paper.. All 65 blue ballpoint pen and 24 black ballpoint pen samples collected from different factories in china and foreign were distinguished, Based on the retention time the peak of the main component, the ratio of mass and charge of liquid chromatography- mass spectrum, two dimensional diagram and three-dimensional diagram etc, 65 blue ballpoint pen were divided into 10 groups , 24 black ballpoint pen were divided into 6 groups.Chapter three separated and distinguished water-soluble pen ink and black gel pen with capillary zone electrophoresis. The effects of different buffer solution, pH , organic additive and extractor were Systematical studied. The most proper separative conditions were selected, 21 different brands water-soluble pen ink and 95 differentbrands black gel penChapter four studied the relative time of writing inks by the variety of the dyes component, A method for comparison of ink entries on papers in different conditions was presented, pure dye writings and ballpoint pen inks were exposed to strong light, infrared light, ultraviolet light heating and daylight. Dyes and inks were then extracted from paper and analyzed by HPLC. Significant changes in composition were noted on exposure to light, Based on the variety of dyes component and each concentration, The reaction mechanism was presumed .