IOSR Journal of Applied Chemistry (IOSR-JAC) e-ISSN: 2278-5736. Volume 5, Issue 3 (Sep. – Oct. 2013), PP 36-41 www.iosrjournals.org www.iosrjournals.org 36 | Page Comparative Analysis of Inkjet Printer Inks Extracted from Printed Documents by FT-IR Spectrophotometry Rashmi Sharma 1 , Kavita Goyal 2 , Amit Chattree 3 , T.R.Baggi 4 , A.K.Gupta 5 1. Senior Research Fellow, Central Forensic Science Laboratory, Ramanthapur, Hyderabad, A.P.500013, India. 2. Senior Scientific Officer, Forensic Science Laboratory, Rohini, Delhi-110085, India. 3. Head, Department of Chemistry, SHIATS, Allahabad, U.P.-211007, India. 4. Academic Coordinator, Forensic Science Unit, Department of Chemistry, University College of Science, Osmania University, Hyderabad, A.P. 500007, India. 5. Head, Department of Forensic Science, SHIATS, Allahabad, U.P.-211007, India. Abstract: Primary coloured inks i.e. Cyan, Magenta, Yellow, and Black used in inkjet printers were extracted from the printed document and analyzed in order to identify the possible functional groups using Infrared (IR) spectroscopic technique. Experiments were conducted on the all four primary inks and the results are presented. The technique can provide valuable information if an admitted sample is provided for comparison with the suspect printed document. Keywords: Functional Group, Inkjet Printing, Infrared Spectroscopy, Printer, Printed Document. I. Introduction Determination of authenticity of a document is based on many factors. Characterization of writing/printing instruments used to produce the document such as ink; paper etc may be a leading step in the investigation. Many instrumental analytical techniques are available to determine the actual composition of dyes and other compounds present in inkjet printer inks. The IR technique is one of the techniques which can provides important information about the commercially available printer inks (Yuen et al, 2005). IR spectroscopy deals with the infra red region of the electromagnetic spectrum. The IR portion of the electromagnetic spectrum is usually divided into three regions; the near-IR (approximately 14000–4000 cm −1 ), mid-IR (4000–400 cm −1 ) and far- infrared (400–10 cm −1 ). The near-IR can excite overtone or harmonic vibrations, the mid-infrared may be used to study the fundamental vibrations and associated rotational- vibrational structure whereas the far-infrared has low energy and may be used for rotational spectroscopy. IR spectroscopy is based upon the ability of certain compounds to absorb radiation by interaction of IR radiation with the molecular bonds of the sample. Absorption occurs when the molecular bond has a vibrational frequency equal to the IR radiation. The wavelengths at which a measured absorption occurs correspond to specific functional groups. This information can be interpreted to characterize the compounds. Fourier Transform Infrared Spectroscopy (FTIR) is used to obtain an infrared spectrum of a solid, liquid or gas. In the Fourier Transform instrument the whole wavelength range is measured at once and then a transmittance or absorbance spectrum is generated with the help of a computer. Analysis of the position, shape and intensity of peaks in the spectrum reveals details about the molecular structure of the sample. A simple glass tube with length of 5 to 10 cm equipped with infrared windows at the both ends of the tube can be used for concentrations down to several hundred ppm. Sample gas concentrations well below ppm can be measured with a White's cell in which the infrared light is guided with mirrors to travel through the gas. Liquid samples can be sandwiched between two plates of highly polished transparent sodium chloride, potassium bromide or calcium fluoride. These plates are transparent to the infrared light. Solid samples can be prepared in a variety of ways such as by finely mixing the fine powder sample with an oily mulling agent (usually Nujol) in a marble or agate mortar, with a pestle. A thin film of the mull is smeared onto salt plates and measured. The second method is to grind a quantity of the sample with potassium bromide finely. This powder mixture is then pressed in a mechanical press to form a translucent pellet through which the beam of the spectrometer can pass. A third technique is the "cast film" technique mainly used for polymeric materials and most suitable for qualititative analysis. The sample is first dissolved in a suitable, non hygroscopic solvent. A drop of this solution is deposited on surface of KBr or NaCl cell. The solution is then evaporated to dryness and the film formed on the cell is analyzed directly. The final method is to use microtomy to cut a thin (20–100 µm) film from a solid sample. IR technique can provide valuable information about the chemical composition of a material (Kan, et al., 2000; Wen, 2004; Huang, 2004) with convenient sample analysis.