Premium
Identification of Colorants in Pigmented Pen Inks by Laser Desorption Mass Spectrometry *
Author(s) -
Papson Kaitlin,
Stachura Sylwia,
Boralsky Luke,
Allison John
Publication year - 2008
Publication title -
journal of forensic sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.715
H-Index - 96
eISSN - 1556-4029
pISSN - 0022-1198
DOI - 10.1111/j.1556-4029.2007.00599.x
Subject(s) - pigment , inkwell , orange (colour) , mass spectrometry , chemistry , chromatography , desorption , copper phthalocyanine , materials science , analytical chemistry (journal) , adsorption , organic chemistry , optoelectronics , food science , composite material
Pigments are rapidly replacing dyes as colorants in pen and printer inks, due to their superior colors and stability. Unfortunately, tools commonly used in questioned document examination for analyzing pen inks, such as TLC, cannot be used for the analysis of insoluble pigments on paper. Laser desorption mass spectrometry is demonstrated here as a tool for analyzing pigment‐based pen inks. A pulsed nitrogen laser can be focused onto a pen stroke from a pigmented ink pen on paper, and positive and negative ions representative of the pigment can be generated for subsequent mass spectrometric analysis. Targeted pens for this work were a set of Uni‐ball ® 207 ™ pigmented ink pens containing blue, light blue, orange, green, violet, red, pink, and black inks. Copper phthalocyanine was identified as the pigment used to make both blue inks. A mixture of halogenated copper phthalocyanines were identified in the green ink. Unexpectedly, the pink ink was found to contain a red pigment, Pigment Red 12, treated with a mixture of water‐soluble dyes. Each sample yielded ions representative of the pigments present.