Ion Pairing HPLC Used for Ink Analysis

Researchers at Beijing Normal University and the Institute of Beijing Criminal Science and Technology (China) used ion pairing high performance liquid chromatography (HPLC) to analyze 12 black inks and six red inks from various manufacturers in a number of countries. They extracted each ink-containing paper sample for 12 h with a acetonitrile–tetrabutylammonium bromide solution and analyzed the filtered extract without further preparation. They used a C18 column to separate the ink dyes with a mobile-phase gradient of acetonitrile in aqueous tetrabutylammonium bromide and UV–vis detection at 590 nm and 520 nm for the black and red inks, respectively.