Fuente: JOURNAL OF ASQDE ENERO 2010 Volume 12, Number 2
Magdalena Ezcurra G., Itxaso Velasco, Juan M. G. Góngora, M. Itxaso Maguregui, and Rosa M. Alonso.
This work studies the ink composition of 26 BIC Cristal Medium ballpoint pens, 13 blue and 13 black, purchased from various countries around the world in 2008. The volatile components of these inks were studied by gas chromatography/mass spectrometry (GC/MS) preceded by a liquid-solid extraction, with the use of retention time locking (RTL) for the 1st time in the forensic field. The RTL tool assures reproducible retention times, and the realignment of the chromatograms assures rescaling of the time axis of the chromatogram. In order to determine the qualitative composition of dyes present in each ink, thin-layer chromatography (TLC) was used, followed by the identification of those colorants by liquid chromatography tandem mass spectrometry (LC/MS-MS). The study revealed that at least 2 different blue-ink formulations were used around the world in this period of time but that the formulation of the black inks was identical for all the studied pens. The differences found in the blue-ink formulations regard not only volatile components but also dyes. The great differences found in the concentration of the volatile component phenoxyethanol (PE) present in the 2 blue-ink formulations lead to important differences in the natural aging process of these 2 blue formulations as measured by the loss of the amount of PE against the time. The amount of PE varied depending on the BIC ink formulation between 221.9 μg and 84.7 μg per lineal centimeter of ink stroke 1 day after the ink was deposited on the paper.