Authenticity of Questioned Documents

Another forensic use of mass spectrometry is to verily the authenticity of questioned documents. The age of an ink can answer this dilenuna. This task can be accomplished by laser desorption/ionization (EDI) mass spectrometry [69]. Methyl violet is a typical dye in ballpoint inks. It is relatively unstable under light and undergoes demethylation upon exposure to light. In a case study, an EDI spectrum showed an abundant amount of M+ ion of m/z 372.2 and less [M — CH3] ion of m/z 358.2. The light-exposure-aged specimen showed a decrease in abundance of the 

M+ ion and an increase in the abnndance of a series of demethylated products. A plot of the relative peak area versus time could be correlated with the age of the document. 

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