Comparative analysis of aged documents by desorption electrospray ionization–Mass spectrometry (DESI‐MS) imaging

Abstract

Document dating is an important and challenging task in the field of forensic science. With the development of analytical techniques, related methods are emerging for document dating studies. Desorption electrospray ionization–mass spectrometry (DESI‐MS) is an ambient ionization‐MS technique that has been applied in the forensic discrimination of inks. This study focused on utilizing DESI‐MS to distinguish between ink entries of different ages. Blue ballpoint ink and black gel ink samples were artificially aged by heat and light exposure and then screened by DESI‐MS in the positive ion mode, with a methanol–water‐formic acid solution (90:10:0.1%, v/v/v) as the desorption solvent. As a result, the artificially aged ink samples were directly differentiated from the reference ones in the chemical images of age‐dependent compounds such as basic dyes or polyethylene glycol derivatives. The amount of ethoxylated fatty amine surfactants in copy paper was also found to decrease after artificial aging. Moreover, this method enabled us to visualize the differences between the composition of naturally aged and fresh ink samples. It has been proven to cause no apparent destruction of the samples. The identification of chronological changes in document materials suggests that the DESI‐MS method is a promising approach for relative document dating.

Applications of ambient ionization mass spectrometry in 2022: An annual review

“…51 The same group also applied this technique to the study of artificially aged inks, demonstrating potential time-dependent changes in the ink and paper that could be beneficial in confirming the age of questioned documents. 52 DART-MS has proven to be an advantageous technique across numerous areas of forensic research. DART as a suitable technique for dye differentiation.…”

“…DESI‐MS was used to characterize components in genuine and falsified stamped fingerprints, readily distinguishing the two based on the presence of sweat‐derived compounds 51 . The same group also applied this technique to the study of artificially aged inks, demonstrating potential time‐dependent changes in the ink and paper that could be beneficial in confirming the age of questioned documents 52 …”

A rapid and direct method for dating blue pen ink in documents using multiset modeling of infrared spectroscopy and mass spectrometry data

“…2 The main dyes used in the composition of pen inks are Basic Violet 3 (BV3), 1,3-dimethyl-1,3ditolylguanidine (DG), Victoria Blue B (VBB), rhodamine (R), and Basic Blue 7 (BB7). [4][5][6][7][8][9][10] Several studies have investigated the effects of aging processes on the composition of dyes, mainly using high performance liquid chromatography (HPLC) and mass spectrometry (MS). [2][3][4][5][6][7][8]11,12 However, the chromatographic methods have the disadvantage of requiring destructive sample preparation prior to analysis.…”

“…[4][5][6][7][8][9][10] Several studies have investigated the effects of aging processes on the composition of dyes, mainly using high performance liquid chromatography (HPLC) and mass spectrometry (MS). [2][3][4][5][6][7][8]11,12 However, the chromatographic methods have the disadvantage of requiring destructive sample preparation prior to analysis. As a result, the samples cannot be recovered, which makes it impossible to use them in a forensic context in judicial processes.…”

“…4,18,19 One of the most common MS ambient ionization technique is desorption electrospray ionization (DESI-MS), which is a minimally destructive that is suitable for the analysis of pen ink. 6 DESI-MS has been used to discriminate dyes, 20 but there is a lack of information in the literature concerning the use of this technique for the dating of pen inks.…”