Ink dating science
Dye components are rapidly separated, and identification is based on comparison of electrophoretic mobility values and ultraviolet-visible spectra with individually run dye standards.A database of ballpoint pen ink analyses and common-dye reference standards has been initiated for future forensic use.Capillary electrophoresis requires an injection volume of only approximately 5–50 n L, which leaves enough sample for analysis by complementary methods because a typical casework ink extract is on the order of 15–50 μL.This is an important feature for real casework samples because multiple confirmatory exams often are necessary.Capillary electrophoresis methods can be readily developed to baseline separate analytes with nearly identical structures (Lurie et al. Data is stored electronically, allowing the development of an automated, searchable library of electropherograms and ultraviolet-visible spectra, while eliminating the need for an environmentally controlled storage space.
Differences in the ink samplings suggested that the questioned entry was made on a separate occasion, possibly to cover up insider trading violations. In addition, the dyes have ultraviolet-visible absorbances that can be measured and used for identification. Secret Service maintains an ink library that consists of approximately 8,500 ink-standard thin-layer chromatography slides.
Capillary electrophoresis is a powerful separation technique that produces theoretical plate counts on the order of 10 to 100 times greater than high-performance liquid chromatography (Skoog et al. The process is completely automated, and method development is rapid.