Detection of signature forgery with erasable pens using paper spray mass spectrometry (PS-MS)

Paper spray mass spectrometry (PS-MS) is applied to a fast, sensitive and reproducible detection of forgery in signatures made with erasable pens that use a chemical method to remove inks (other than the usual physical methods). A forgery process was simulated by signing over a previously erased signature and triangular sections were cut out of the paper in order to perform the PS-MS analysis. No sample preparation was required as the analysis was conducted directly on the triangular paper by simply wetting it with methanol and applying high voltage. Analysis of the original, erased and forged signatures was made following the same procedure. The results show that the original and the forged signatures were promptly distinguished by their mass spectrometry profiles (fingerprints). Hence, the appearance of diagnostic ions (of m/z 172 and m/z 321) in the mass spectrum of the counterfeit signature can be used to quickly and reliably characterize this novel and potentially harmful type of forgery.