A range of Raman spectrometers for the examination of questioned documents
For forensic applications FORAM spectrometers are supplied with either a 532nm, 685nm or 785nm laser and have a spectral range of 400 to 2000 wavenumbers and 8 wavenumber resolution.
The instruments have an integral video microscope to assist sample selection, and a turret of four objective lenses provide on screen magnification of up to x500. A large XYZ translation stage which can support whole documents allows alignment and focussing onto areas of interest as small as 5 microns.
The system is controlled with easy to use on screen menus, and the software provides for baseline correction of spectra to remove background fluorescence, automatic spectral comparisons, and data archiving with search and match facilities.
In recent years, gel pens have become more commonly used by the general public in preference to traditional ball point and liquid ink pens. Gel pens present new challenges to document examiners since many employ inks which are based on pigments, rather than dyes, which cannot easily be extracted for analysis by thin layer chromatography (TLC).
Several scientific studies have been published reporting the use of Raman spectroscopy to discriminate between gel pens. Mazella and Buzzini  have applied Raman spectroscopy using two different excitation wavelengths to give a discrimination rate of 68% for pigmented blue gel pens. Zieba-Pulus et al  utilised a combined Raman/μXRF instrument to analyse a range of materials of forensic interest including blue gel pens.
In this Application Note, we demonstrate the potential of the Foster + Freeman Raman Spectral Comparator (FORAM) to differentiate blue gel pens.
The discrimination of laser printer and photocopier toners present the document examiner with particular challenges. Conventional analytical techniques such as visible/IR absorption which are so useful in ink examination are not applicable to toners. Other techniques such as FTIR (Fourier Transform Infrared) spectroscopy are either quite destructive to the document or are time consuming and expensive. Merrill et al  have described the various FTIR techniques which may be applied to toners.
In this Application Note, we demonstrate the potential of the Foster + Freeman FORAM Raman Spectral Comparator to discriminate toners. Initially, we attempt to discriminate toner in-situ on the document. Subsequently, we extract the acetone soluble components from the toner and deposit the solute onto aluminium foil. This solute is then subjected to Raman analysis in the same way.
The low cost and ready availability of inkjet printers has greatly increased the frequency with which documents produced by these machines are encountered by document examiners. Conventional analytical techniques such as visible/IR absorption which are normally so useful in ink examination are not as effective with printed documents produced by inkjet printers. Other techniques such as chromatography involve the destruction of a small portion of the document.
Whilst the application of Raman and SERRS (Surface Enhanced Resonance Raman Scattering) spectroscopy to the analysis of questioned documents is widely discussed in the scientific literature [1, 2, 3, 4], the application of these techniques to the analysis of black inkjet inks is somewhat limited.Littleford et al  have used SERRS spectroscopy to 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.
In this Application Note, we demonstrate the potential of the Foster + Freeman FORAM Raman Spectral Comparator to discriminate black inkjet inks when used in conjunction with the SERRS technique.
Presumptive tests are the simplest examination carried out on explosive substances but they lack specificity. Field techniques such as Ion Mobility Spectroscopy (IMS) are expensive and can be prone to false positives. Whilst traditional Mass Spectrometry techniques, are expensive, and difficult to make field deployable.
One of the newer technologies to identify explosive residues is Raman spectroscopy.
The Foster & Freeman Foram-785 Portable Raman System provides fast and non-destructive analysis of explosives and importantly is able to identify a specific explosive due to the “signature” spectrum that the explosive gives. It is able to get positive ID of particles < 3 microns in size.
Foster + Freeman, in partnership with S.T. Japan GmbH are now able to offer a comprehensive collection of Raman spectra libraries that have been formatted for use with the Foram and ffTA systems.
In total over nine thousand spectra of common and specialist materials are available divided into 20 categorised libraries including:
- Forensic Compounds
- Pharmaceuticals, Drugs and Antibiotics
- Hazardous and Toxic Chemicals
- Dyes, Pigments, and Stains
A complete list of the available libraries, together with order codes, can be downloaded here