Application Of HPLC/MS In Color Marks Identification

With the development of society, legal relationships between individuals or groups often reflect in effectively legal documents such as contracts, bills. Therefore, it’s significant to identify the authenticity of these documents. Color marks identification (handwriting or seal stamps) is an effective means.There are mainly two kinds of color marks identification:distinction of different inks and their date on paper. Inks of ballpoint pen, gel pen and seal stamp are generally composed by colorants, solvents and other auxiliary components. Their components and corresponding concentration in various inks are always different, which is the theoretical basis of color marks identification. Ink components will go through complicated physical and chemical reactions on paper, such as volatilization, crossinking, degradation. In this way it could not only help dating identification but also establish intersections of different inks.Spectroscopy, chromatography and mass spectrometry have been used in colorful marks identification.Compared with reported methods, HPLC draw benefits of high separation efficiency and good reproducibility, and ESI-MS could provide both molecular weight and fragment information. Therefore, HPLC/ESI-MS was chosen to analyze ballpoint pen, gel pen and red sealing inks in this study. The main conclusions are listed as follows:1. After extractions optimized by UV-Vis, nine red sealing inks were analyzed by LC/MS and classified into five categories by different retention time. It was indicated that their main components included Lake Red C, Fast Red3132, Dibutyl Phthalate, Dioctyl Phthalate, and coresponding standard curve was established. Furthermore, aging of inks in dark and light condition was either studied.2. Based on LC/MS, ten black and ten blue ballpoint pens were classified into three and two major kinds according to different retention time and peak area, respectively. Crystal Violet, Methyl Violet, Basic Blue26and Para-rosaline were found in ballpoint pen inks. Natural and artificial aging process of these compounds were studied to make their aging curves.3. Extractions, as well as its temperature and time, were optimized in gel pen inks analysis. For different nonvolatile components in inks, fourteen black and eleven blue gel pens were classified into three and four major kinds based on HPLC, respectively.