NCJ Number
217245
Journal
Journal of Forensic Sciences Volume: 52 Issue: 1 Dated: January 2007 Pages: 216-220
Date Published
January 2007
Length
5 pages
Annotation
This study compared the ability of two methods to differentiate blue ballpoint inks: laser desorption ionization mass spectrometry (LDI-MS) and high-performance thin-layer chromatography (HPTLC).
Abstract
The findings indicate that LDI-MS and HPTLC are complementary to some extent. The presence of anionic dyes in blue ballpoint inks was recorded by HPTLC, but was not detected by LDI-MS in the positive mode; however, LDI produced information on the structure of the basic dyes and pigments. Spot identification and peak integration on the HPTLC plate were less precise. With respect to the chemical differentiation of inks, LDI-MS has proven to be a powerful technique for discriminating ballpoint dyes in ink formulations directly from written ink entries on paper. Sample preparation is minimal and analysis time is short in contrast to the more complex extraction, application, and development steps of HPTLC. MS resulted in the separation of the 31 blue ballpoint pens into 26 classes compared with the 18 groups obtained with HPTLC. The authors' proposed strategy is to differentiate and characterize ballpoint inks by first using inexpensive and rapid optical comparison with light sources at different wavelengths. This preliminary step should be followed by identification of the dye composition, preferably by LDI-MS; however, forensic scientists should remember that aging of ink dyes can substantially influence the results of this method. Analyses of other substances present in ballpoint ink, such as solvents or resins, should be performed to differentiate pairs that cannot be distinguished by dye composition. The study used 31 blue ballpoint pens that were randomly chosen from the German market. The pens were used to prepare entries on multifunction bright-white, wood-free, and chlorine-free paper. The straight ink lines were immediately sampled for analysis after their application to the paper. 1 table, 3 figures, and 17 references