Analysis of ballpoint pen inks directly from paper using capillary electrophoresis

Abstract A new sampling technique for capillary electrophoretic analysis of writing inks directly from the surface of paper is introduced. A section of paper containing a written word is placed on a sampling platform. The automated system is programmed to deposit about 3 µL of background electrolyte onto a portion of the writing to solubilize some of the ink. A small portion of the solution created is then electrokinetically injected into the capillary and analyzed. The ink surface area consumed was 40× less than a conventional off-line sample extraction technique. Moreover, because of the higher concentration of analyte in solution in the direct analysis technique, less sample volume was injected into the capillary resulting in a better peak shape and higher signal-to-noise ratio (S/N) when compared to a traditional method. In addition, this novel technique minimizes sample preparation time, uses less sample, and produces less waste than conventional methods.