1.1 红外光谱法是法医学鉴定和比较纤维聚合物的一种有价值的方法。红外显微镜与傅立叶变换红外光谱仪的使用大大简化了单根纤维的红外分析，从而使该技术在法医实验室的常规使用变得可行。本指南提供了有关红外光谱仪和附件的基本建议和信息，重点介绍了光纤检查特有的采样技术。每个检验师或实验室采用的特定方法将取决于可用设备、检验师培训、样本适用性和样本量。 1.2 本指南适用于具有红外光谱理论和实践基础知识以及纤维处理和法医检验经验的检验员。此外，本指南将与更广泛的分析方案结合使用。 1.3 如果仅从光学数据中无法明显识别聚合物，则应使用额外的分析方法，如微化学测试、熔点、红外光谱、拉曼光谱或热解气相色谱。红外光谱的一个优点是，该仪器在大多数法医实验室都很容易获得，而且该技术的破坏性最小。 1.4 单位-- 以国际单位制表示的数值应视为标准。本标准中不包括其他计量单位。 1.5 本标准适用于受过必要的正规教育和特定学科培训的合格法医学从业者（见实践 E2917 )，并表现出执行法医案件工作的熟练程度。 1.6 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.7 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ===意义和用途====== 5.1 本指南旨在帮助检查员选择合适的样品制备方法，用于使用红外光谱分析、比较和鉴定纤维。IR光谱可以提供比单独使用偏振光显微镜获得的成分信息更多的成分信息。 进行红外光谱比较的程度将随着具体样品和案例评估的不同而变化。 5.2 红外分析应遵循可见光和荧光比较显微镜、偏振光显微镜和紫外线（UV）/可见光谱法。如果已知和未知样品在光学性质上没有发现排除性差异，则在适用的情况下，将红外光谱作为分析方案的下一步。 注1: IR分析通常遵循上述技术，因为样品制备（例如，压平）不可逆地改变纤维形态。 5.3 由于提取技术具有半破坏性，因此应在染料提取前进行红外光谱分析以进行色谱分析。由于有大量的亚类，丙烯酸和改性丙烯酸纤维的法医学检查可能会从红外光谱分析中受益匪浅 ( 5. ) 尼龙纤维和聚酯纤维的亚型之间的有用区别也可以通过IR光谱进行。 5.4 红外光谱可以提供关于主要有机和无机成分的分子信息。含量较少的成分通常更难识别。 造成这种情况的原因包括主要成分的吸收带与次要成分强度较低的吸收带的干扰，以及次要成分以低于仪器检测限的浓度存在的灵敏度问题。 5.5 通过各种技术制备和安装纤维样品用于显微镜红外分析。使用与IR显微镜、ATR或具有光束冷凝器的金刚石压缩池耦合的IR光谱仪获得纤维的IR光谱。 5.6 IR光谱可用于获得用于阐明纤维的化学成分和用于比较两个或多个纤维样品的光谱。 6.5.6 当用于表征纤维类型时，可以将光谱与从认证样品或参考标准中获得的参考光谱进行比较。 5.6.2 当用于光谱比较时，目的是确定样本之间是否存在任何排除性差异。

1.1 Infrared (IR) spectroscopy is a valuable method of fiber polymer identification and comparison in forensic examinations. The use of IR microscopes, coupled with Fourier transform infrared (FTIR) spectrometers, has greatly simplified the IR analysis of single fibers, thus making the technique feasible for routine use in the forensic laboratory. This guide provides basic recommendations and information about IR spectrometers and accessories, with an emphasis on sampling techniques specific to fiber examinations. The particular method(s) employed by each examiner or laboratory will depend upon available equipment, examiner training, sample suitability, and sample size. 1.2 This guide is intended for examiners with a basic knowledge of the theory and practice of IR spectroscopy, as well as experience in the handling and forensic examination of fibers. In addition, this guide is to be used in conjunction with a broader analytical scheme. 1.3 If polymer identification is not readily apparent from optical data alone, an additional method of analysis, such as microchemical tests, melting point, IR spectroscopy, Raman spectroscopy, or pyrolysis gas chromatography, should be used. An advantage of IR spectroscopy is that the instrumentation is readily available in most forensic laboratories and the technique is minimally destructive. 1.4 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard is intended for use by competent forensic science practitioners with the requisite formal education, discipline-specific training (see Practice E2917 ), and demonstrated proficiency to perform forensic casework. 1.6 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. 1.7 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. ====== Significance And Use ====== 5.1 This guide is designed to assist an examiner in the selection of appropriate sample preparation methods for the analysis, comparison, and identification of fibers using IR spectroscopy. IR spectroscopy can provide additional compositional information than is obtained using polarized light microscopy alone. The extent to which IR spectral comparison is conducted will vary with specific sample and case evaluations. 5.2 IR analysis should follow visible and fluorescence comparison microscopy, polarized light microscopy, and ultraviolet (UV)/visible spectroscopy. If no exclusionary differences are noted between the known and unknown samples in optical properties, then proceed to IR spectroscopy as the next step in the analytical scheme, as applicable. Note 1: IR analysis generally follows the aforementioned techniques since sample preparation (for example, flattening) irreversibly changes fiber morphology. 5.3 IR spectroscopy should be conducted before dye extraction for chromatography due to the semi-destructive nature of the extraction technique. Because of the large number of sub-generic classes, forensic examination of acrylic and modacrylic fibers is likely to benefit significantly from IR spectral analysis ( 5 ) . Useful distinctions between subtypes of nylon and polyester fibers can also be made by IR spectroscopy. 5.4 IR spectroscopy can provide molecular information regarding major organic and inorganic components. Components in lesser amounts are typically more difficult to identify. Reasons for this include interference of the absorption bands of the major components with the less-intense bands of minor components, and sensitivity issues whereby the minor components are present at concentrations below the detection limits of the instrument. 5.5 Fiber samples are prepared and mounted for microscopical IR analysis by a variety of techniques. IR spectra of fibers are obtained using an IR spectrometer coupled with an IR microscope, ATR, or diamond compression cell with beam condenser. 5.6 IR spectroscopy can be used to obtain spectra for elucidation of the chemical composition of the fiber and for comparison of two or more fiber samples. 5.6.1 When used to characterize the fiber type, the spectrum can be compared to reference spectra obtained from authenticated samples or reference standards. 5.6.2 When used for spectral comparisons, the objective is to determine whether any exclusionary differences exist between the samples.