Spectral Analysis of Ball Pen Script by FTIR Microscope with ATR Objective
HUANG Tao-hong1,WU Tian-ming2
1. Shimadzu International Trading (Shanghai) Co., Ltd, Shanghai Analytical Applications Center, Shanghai 200020, China 2. The Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
Abstract：Inspection of ball pen script is very important in public security and justice field. It is difficult to get a good spectrum directly by infrared microscope reflectance mode because of low reflectivity of paper and dark gray in color. The best way to measure low reflectivity sample is by infrared microscope with ATR objective method. Measurement with the microscopic ATR method involves bringing the trace of ball pen ink into contact with the prism.By this method, some mixed spectra of ball pen ink and paper fiber were obtained from one of the actual sample. The spectrum of the paper was subtracted from those mixed spectra and a pure spectrum of the ball pen ink was obtained. In this spectrum, three strong peaks were found 1 581，1 361 and 1 172 cm-1 respectively, all from crystal violet, a typical triphenylmethane pigment. Another strong peak at 1 724 cm-1 is contributed by carbonyl vibration from oil reagent alkyd. A 3D graph, showing the distribution of peak 1 581 cm-1 in this area, was set up by using mapping software. In the 3D distribution graph, the figure of ball pen trace vividly appeared. This infrared microscope ATR method makes it available to nondestructively inspect original ball pen script.
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