Combination of a Green and a Traditional Method for Estimating Relative and Absolute Ink Age: A Case Study of Ballpoint Pen Ink Dating in Vietnam

Abstract

The dating of ink in questioned documents remains a significant challenge in forensic investigations in Vietnam and other countries. Many forensic examination methods have been usually applied to ensure the highest accuracy of the assessment results while maintaining high environment awareness. In this study, paper characteristics were physically tested to confirm source similarity, and the relative ink dating was established by high-performance thin-layer chromatography (HPTLC). Absolute ink dating by solvent and dye identification was performed by Raman spectrometry—a green technique, using a time-dependent degradation model for crystal violet and the comparison between 2-phenoxyethanol peak intensities. We found that the relative dating of the questioned document was 14 ± 3 months lesser than that of the reference samples, i.e., the absolute age of the questioned samples was estimated to be 24 ± 3 months. The combination of the conventional HPTLC method with the dynamic crystal violet degradation Raman model provides promising results for relative and absolute ink dating of ballpoint pens, which can be applied for documents written 1–15 years prior to the time of examination. The combination of the abovementioned methods demonstrated an acceptable error margin, affording highly practical applications in modern forensic science.

GC-MS Silylation Derivative Method to Characterise Black BIC® Ballpoint 2-Phenoxyethanol Ratio Evaporation Profile—A Contribution to Ink Ageing Estimation

“…First, we established the GC/MS conditions for separation and detection of ink constituents. This included an initial derivatisation step with a silylation reagent, since pen inks usually have a heterogenous mixture of compounds with different physico-chemical properties, including dyes, pigments, stabilising polymers, liquid solvents, and other additives [ 8 ]. In this case, this procedure is crucial for (i) improvement of the resolution and reducing the tailing of polar compounds, (ii) analysis of relatively non-volatile compounds, (iii) improvement of analytical efficiency and increasing detectability, and (iv) stabilising compounds for GC/MS analysis [ 8 ].…”

“…This included an initial derivatisation step with a silylation reagent, since pen inks usually have a heterogenous mixture of compounds with different physico-chemical properties, including dyes, pigments, stabilising polymers, liquid solvents, and other additives [ 8 ]. In this case, this procedure is crucial for (i) improvement of the resolution and reducing the tailing of polar compounds, (ii) analysis of relatively non-volatile compounds, (iii) improvement of analytical efficiency and increasing detectability, and (iv) stabilising compounds for GC/MS analysis [ 8 ]. After applying the proposed approach, it was possible to identify in the black point pen ink three target peaks with retention times of 22.7 min (peak 1), 23.1 min (PE-TMS, peak 2), and 23.8 min (peak 3), Figure 1 .…”

“…These approaches include accelerated ageing techniques, chemometrics, construction of document chronology, luminescent component analysis, radiocarbon dating, and nanotechnology-based methods [ 3 , 6 , 7 ]. In the literature, the case reports show that the ageing document determination is mainly performed by the determination of the changes in crystal violet colorant and the solvent 2-phenoxyethanol (PE) [ 8 , 9 , 10 , 11 ].…”

Interpol questioned documents review 2019–2022

“…including any other technology used to prepare the document. The following 64 articles [ [548] , [549] , [550] , [551] , [552] , [553] , [554] , [555] , [556] , [557] , [558] , [559] , [560] , [561] , [562] , [563] , [564] , [565] , [566] , [567] , [568] , [569] , [570] , [571] , [572] , [573] , [574] , [575] , [576] , [577] , [578] , [579] , [580] ] [ [581] , [582] , [583] , [584] , [585] , [586] , [587] , [588] , [589] , [590] , [591] , [592] , [593] , [594] , [595] , [596] , [597] , [598] , [599] , [600] , [601] , [602] , [603] , [604] , [605] , [606] , [607] , [608] , [609] , [610] , [611] ], combined with 17 presentations [...…”

“…Hoang et al [ 574 ] combined green and traditional methods to improve accuracy in the estimation of relative and absolute age of ballpoint pen inks. Green methods like Raman and paper characteristics measurement were used to first determine batch similarity and storage conditions of the documents and inks.…”