Problems with thin-layer chromatography reproducibility can be related to the difficulty in spotting uniform samples and maintaining constant environmental influences, which lead to changes in R values.Limited sensitivity, sample destruction, and extra processing required for additional information are also shortcomings of the method.Capillary electrophoresis allows ease of sample preparation with the ability to separate and identify dye compounds based on a calculated electrophoretic mobility and a characteristic ultraviolet-visible spectrum.
The ability to distinguish different inks can be quite useful for several reasons.
Document alteration (e.g., at a date later than indicated) by writing with a pen of similar color but different dye composition is one specific example when ink differentiation is crucial in criminal cases.
Vehicles or carriers are usually solvents that allow the ink to flow and carry the colorants to the material surface.
Solvents are the typical ingredients analyzed in date-of-origin investigations because of their gradual evaporation from a document (Aginsky 1994; Brunelle 1992; Brunelle and Cantu 1987; Brunelle et al. Last, additives can serve as flow (viscosity) modifiers, surface activators, corrosion controllers, solubility enhancers, and preservatives (Brunelle and Reed 1984; Leach and Pierce 1993).
Because of the small volume necessary for analysis, the remaining solution could be further processed using current law enforcement procedures for confirmation.