Significance and Use
5.1 FTIR spectroscopy may be employed for the classification of paint binder types and pigments as well as for the comparison of spectra from known and questioned coatings. When utilized for comparison purposes, the goal of the forensic examiner is to determine whether any significant differences exist between the known and questioned samples.
5.2 This guide is designed to assist an examiner in the selection of appropriate sample preparation methods and instrumental parameters for the analysis, comparison or identification of paint binders and pigments.
5.3 It is not the intent of this guide to present comprehensive theories and methods of FTIR spectroscopy. It is necessary that the examiner have an understanding of FTIR and general concepts of specimen preparation prior to using this guide. This information is available from manufacturers’ reference materials, training courses, and references such as: Forensic Applications of Infrared Spectroscopy (Suzuki, 1993) (4), Infrared Microspectroscopy of Forensic Paint Evidence (Ryland, 1995) (5), Use of Infrared Spectroscopy for the Characterization of Paint Fragments (Beveridge, 2001) (6), and An Infrared Spectroscopy Atlas for the Coatings Industry (2).
Scope
1.1 This guide applies to the forensic IR analysis of paints and coatings and is intended to supplement information presented in the Forensic Paint Analysis and Comparison Guidelines (1)2 written by Scientific Working Group on Materials Analysis (SWGMAT). This guideline is limited to the discussion of Fourier Transform Infrared (FTIR) instruments and provides information on FTIR instrument setup, performance assessment, sample preparation, analysis and data interpretation. It is intended to provide an understanding of the requirements, benefits, limitations and proper use of IR accessories and sampling methods available for use by forensic paint examiners. The following accessory techniques will be discussed: FTIR microspectroscopy (transmission and reflectance), diamond cell and attenuated total reflectance. The particular methods employed by each examiner or laboratory, or both, are dependent upon available equipment, examiner training, specimen size or suitability, and purpose of examination. This guideline does not cover the theoretical aspects of many of the topics presented. These can be found in texts such as An Infrared Spectroscopy Atlas for the Coatings Industry (Federation of Societies for Coatings, 1991) (2) and Fourier Transform Infrared Spectrometry (Griffiths and de Haseth, 1986) (3).
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
