Inks in the Analytical Laboratory: A Forensics Activity for Undergraduate Students

Here, we present a laboratory activity in which the students work on an analysis of a questioned document that was written with one out of five possible pens. As a forensics study, the activity applied chemistry and analytical chemistry tools to solve the case. The students were able to apply polarity and solubility concepts to select and discard some pens. They also learned the basics of fluorescence and the possibilities of using it to detect falsifications. Then, they were able to set up the detection conditions for the HPLC-UV analysis by studying the absorbance behavior of the blue dyes. Finally, the students identified the pen used to write the suicide note and partially characterized the composition of the ink. This multipurpose activity perfectly suits subjects involving analytical techniques and forensics for students with basic knowledge of chemistry that are studying instrumental techniques for the first time.