This experiment showed that the nondestructive analysis of writing inks on paper without visible alteration can be achieved by using mass spectrometry with a new ion source called Direct Analysis in Real Time (DART).
The experiment found that the ink lines were not visibly altered by the DART analysis. Inspection with a low-power microscope failed to show any difference between the sampled and unsampled regions of individual ink lines. Mass spectrometry using DART sampling proved to be a quick, nondestructive method for analyzing ink on questioned documents. It produced spectra of sufficient quality and diversity to distinguish all but the most similar inks. Traditional methods of identifying the specific formula and manufacturer of ink generally require cutting sample material from the questioned document or otherwise visibly altering it. In addition, they often require skilled sample preparation, and the separation techniques are time-consuming. DART has recently been introduced as a new sampling interface for mass spectrometers. DART samples any material held in its ionization stream, which is open to the environment, so no sample is cut from a document during an analysis. The appearance of the writing is not changed by the sampling process. In the current experiment, this procedure was applied to 43 inks from pens or refill cartridges purchased between 2001 and 2004. These consisted of 13 black ballpoint inks, 10 blue ballpoint inks, 10 black fluid inks, and 10 black gel inks. The inks had been used in writing on paper either 11 or 16 months before testing, except for four black ballpoint inks, which were 7 weeks old. The spectra achieved were placed in a searchable library, which was then challenged with two spectra from each of the 43 inks. 4 figures and 17 references