To determine the color and composition of pen inks and inked writing found on documents pertinent to the case.

Collect a variety of ballpoint and felt tip pens and prepare documents with those pens. Assign pens and documents to the suspects and to the crime scene.

Extraction fluid and mobile phase: aqueous 0.005 M heptanesulfonic acid and acetonitrile mixed in 45:55 ratio.

Standard Reference Material

None

Visible spectrophotometry ; liquid chromatography

UV-Vis spectrophotometer; pair of small-volume, 1-cm cuvettes; liquid chromatograph with C18 column and diode array detector ; 2-mL chromatography vials with screw caps

For instructor (detailed); For student (brief)

Visible spectra of felt tip and ballpoint inks ; representative chromatograms of two (A and B) pen inks: 20-µL injection of liquid sample; C18 column; isocratic elution with 45:55 aqueous 0.005 M heptanesulfonic acid (pH = 4.7): acetonitrile, flowing at 0.3 mL/min.