Volume 34, Issue 5 (September 1989)
Determining the Relative Age of Ballpoint Ink Using a Single-Solvent Extraction, Mass-Independent Approach
Brunelle et al. (Journal of Forensic Sciences. Nov. 1987) recently reported a single-solvent extraction technique for determining the relative age of ballpoint ink entries on questioned documents. This technique was mass dependent, which means equal amounts of ink had to be removed from the document for all samples compared. This paper describes a modification of the previous procedure that makes the age determination independent of the amount of ink sampled for testing. The modified procedure involves extracting the inks with solvents, spotting the ink extract onto a thin-layer chromatographic plate, and then separating the dye components in a solvent system of ethyl acetate: alcohol: water (70:35:30 parts, respectively). The relative concentrations of the dye components are measured using a densitometer. The calculated ratios of the relative concentrations are independent of the amount of ink taken for analysis. Aging curves were prepared for four different ballpoint inks and two non-ballpoint inks. The effect of different papers on ink aging was determined, and the mass independence theory was verified. The feasibility for determining the relative age of non-ballpoint inks was also established.