Micro-infrared Spectroscopy Analyzing Writings about Their Componential Identity from Thermosensitive Erasable Signing Pens

To explore the feasibility of identifying the writings with their componential identity from thermosensitive erasable signing pens using microscopic attenuated total internal reflectional Fourier transform infrared spectroscopy (ATR-FTIR). With a collection of 49 kinds of thermosensitive erasable signing pens (from color- and batch-different products of 5 various brands) and 5 brand-discrepant common signing pens, the writings were tested from the collected pens via microscopic ATR-FTIR. At the same time, the influence of paper was investigated on the infrared spectrum of writing. All the 49 erasable writing samples had one strong infrared absorption peak near the respective 2916, 2850, 1729, 1513, 1455, 1254, 1214, 1170, 830, 739 and 698cm-1, revealing that those brand-different yet color-same erasable pens were shown of their writings into the peaks of obvious difference at both position and intensity. For those model-same yet color-different pens, their writing samples were also found of obvious difference with their infrared absorption peak and intensity. The microscopic ATR-FTIR can identify not only whether one suspicious writing has been forged about its componential identity but also the brand of erasable pen used for forging. This method is of fast, lossless and accurate advantages, capable of providing effective means for the inspection of forged documents.