【国外标准】 Standard Guide for Microspectrophotometry in Forensic Paint Analysis

5.1 This guide is designed to assist an analyst in the selection of appropriate sample preparation methods and instrumental parameters for the analysis and comparison of paint pigments and colors. When used for comparison purposes, the goal is to determine whether any exclusionary differences exist between the samples.5.2 Paint sample spectra can be measured by reflectance or transmittance spectroscopy for comparison purposes. Transmittance measurements are generally preferred and are required for the analysis of UV absorbers in clear coats and the detailed analysis of effect pigments that are not opaque. Emission comparison by means of fluorescence is also measurable.5.3 It is not the intention of this guide to present comprehensive theories and methods of MSP. It is necessary that the analyst have an understanding of UV-Vis-NIR MSP and general concepts of specimen preparation before using this guide. This information is available from manufacturers’ reference materials, training courses, and references such as Eyring (1),3 Stoecklein (2), and Purcell (3).1.1 This guide is intended to assist forensic analysts who conduct UV, visible, NIR, or fluorescence emission spectral analyses on small fragments of paint or use Guide E1610, as this guide is to be used in conjunction with a broader analytical scheme.1.2 This guide deals primarily with color measurements within the visible spectral range but will also include some details concerning measurements in the UV and NIR spectral ranges. The particular method(s) employed by each analyst depends upon available equipment, examiner training (Practices E2917, E3234), sample suitability, and sample size.1.3 This guide provides basic recommendations and information about microspectrophotometers.1.4 This guide does not address other areas of color evaluation such as colorimetric values, paint surface texture or pigment particle size, shape, or dispersion within a paint film that are evaluated by other forms of microscopy.1.5 This guide is directed at the color analysis of commercially prepared paints and coatings. It does not address the analysis or determination of provenance of artistic, historical, or restorative paints, but it could be useful in those fields.1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.7 This standard is intended for use by competent forensic science practitioners with the requisite formal education, discipline-specific training (see Practices E2917, E3234), and demonstrated proficiency to perform forensic casework.1.8 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.