Signature Instrument Method Of Ink Types

It is an important problem nowadays to distinguish whether the questioned documents,like contracts, deeds and receipts, written in gel pen inks are fake. We should establish an exact method to distinguish the similarities and differences of the gel pen inks and identify the writing age because gel pens are the most common written tools in daily life. In this study, 46 different kinds of blue gel pen inks and 35 different kinds of red gel pen inks from different manufactures were studied with three analysis methods: UV-vis spectrophotometry, thin-layer chromatography (TLC) and High performance liquid chromatography (HPLC). By analyzing the component of gel pen inks through all the methods and contrasting to the conclusion, the classification of gel pen inks was confirmed to be reliable which left the foundation for the next study.Chapter one introduced the class of kinds of pens and summarized the recent advance of the research for the writing age of them.In chapter two, the kinds of blue gel pen inks were studied by UV-vis spectrophotometry and thin-layer chromatography (TLC) which were used for classification. The blue gel pen inks can be classified into 5 groups according to the difference of UV absorption peaks and they can be further classified into 9 groups according to the Rf values and color tones of dyestuff spots separated by TLC.In chapter three, 46 blue gel pens were divided into 9 groups according to the number of peaks and the chromatographic retention times of main component. This result can match along well with the classification of TLC.In chapter four and chapter five, 35 red gel pen inks were separated into 4 groups according to the difference of UV absorption peaks and divided into 11 groups according to the number of peaks and the chromatographic retention times of main component. By using external standard method, one of the main components was confirmed to be eosin yellowish.