Discriminating Inks and Toners
Using Raman Spectroscopy to Discriminate Blue Gel Pens
Gel pens are increasingly being used in by the general public in preference to more traditional ballpoint and liquid ink pens. Gel pens have presented new challenges to document examiners; primarily because many of them are pigment based and cannot be easily extracted for analysis by thin layer chromatography (TLC). It is, therefore, useful to find other methods of analysis for these pens.
There have been several scientific studies published using Raman spectroscopy and other methods to discriminate Gel Pens. Mazella and Buzzini used Raman Spectroscopy at 2 different wavelengths to give a discrimination rate of 68% for pigmented blue gel pens. Zieba-Pulus et al utilized a combined Raman/µXRF instrument to analyze a range of materials of forensic interest including blue Gel Pens.
Here we present a brief study applying Raman spectroscopy to discriminate blue gel pens, using 3 different wavelengths of laser excitation; namely 532 nm, 685 nm and 785 nm
Using Surface-Enhanced Resonance Raman Scattering (SERRS) to Discriminate Inkjet Inks
Due to the ready availability and cheap cost of inkjet printers, printed documents produced by these machines are frequently encountered by forensic document examiners. Conventional techniques such as visible/IR absorption, so useful in ink examination are not as effective in the examination of printed documents produced by inkjet printers. Other techniques such as chromatography involve the destruction of a small portion of the document.
Littleford et al have used SERRS Spectroscopy to the probe the structural changes of the chromophore present in black inkjet inks when deposited onto paper. They also give examples of the types of dye that are likely to be found in inkjet inks.
Here we present a brief study applying SERRS spectroscopy to the discrimination of black inkjet inks, and determine its potential use in the discrimination of inks produced by different manufacturers.
Using Raman Spectroscopy to Discriminate LaserJet and
LaserJet and Photocopy toner are some of the more challenging materials which the document examiner is asked to examine. Conventional techniques such as visible/IR absorption, so useful in ink examination are not applicable to toners. Techniques which are used such as FTIR are either quite destructive to the document or are time-consuming and expensive to carry out.
Merrill et al comprehensively describe the various FTIR techniques as applied to toners.
Here we present a brief study applying Raman spectroscopy to the discrimination of toners. Firstly we attempt to discriminate toner in-situ on the document.