School of Molecular and Life Sciences , Curtin University , GPO Box U1987 , Perth , Western Australia , Australia 6845.
Curtin Institute of Functional Molecules and Interfaces , GPO Box U1987 , Perth , Western Australia , Australia 6845.
Anal Chem. 2019 Aug 20;91(16):10622-10630. doi: 10.1021/acs.analchem.9b01843. Epub 2019 Jul 30.
Fingermarks are an important form of crime-scene trace evidence; however, their usefulness may be hampered by a variation in response or a lack of robustness in detection methods. Understanding the chemical composition and distribution within fingermarks may help explain variation in latent fingermark detection with existing methods and identify new strategies to increase detection capabilities. The majority of research in the literature describes investigation of organic components of fingermark residue, leaving the elemental distribution less well understood. The relative scarcity of information regarding the elemental distribution within fingermarks is in part due to previous unavailability of direct, micron resolution elemental mapping techniques. This capability is now provided at third generation synchrotron light sources, where X-ray fluorescence microscopy (XFM) provides micron or submicron spatial resolution and direct detection with sub-μM detection limits. XFM has been applied in this study to reveal the distribution of inorganic components within fingermark residue, including endogenous trace metals (Fe, Cu, Zn), diffusible ions (Cl, K, Ca), and exogeneous metals (Ni, Ti, Bi). This study incorporated a multimodal approach using XFM and infrared microspectroscopy analyses to demonstrate colocalization of endogenous metals within the hydrophilic organic components of fingermark residue. Additional experiments were then undertaken to investigate how sources of exogenous metals (e.g., coins and cosmetics) may be transferred to, and distributed within, latent fingermarks. Lastly, this study reports a preliminary assessment of how environmental factors such as exposure to aqueous environments may affect elemental distribution within fingermarks. Taken together, the results of this study advance our current understanding of fingermark composition and its spatial distribution of chemical components and may help explain detection variation observed during detection of fingermarks using standard forensic protocols.
指纹是犯罪现场痕迹证据的重要形式；然而，由于响应的变化或检测方法的不稳健性，其用途可能会受到阻碍。了解指纹中的化学组成和分布情况可能有助于解释现有方法中潜伏指纹检测的变化，并确定增加检测能力的新策略。文献中的大多数研究都描述了对指纹残留物有机成分的研究，而元素分布则了解较少。关于指纹内元素分布的信息相对较少，部分原因是以前无法直接进行微米分辨率的元素映射技术。这种能力现在在第三代同步加速器光源中提供，其中 X 射线荧光显微镜（XFM）提供微米或亚微米空间分辨率，并具有亚微米检测限的直接检测。在这项研究中，XFM 被应用于揭示指纹残留物中无机成分的分布情况，包括内源性痕量金属（Fe、Cu、Zn）、可扩散离子（Cl、K、Ca）和外源性金属（Ni、Ti、Bi）。本研究采用了 XFM 和红外微光谱分析的多模态方法，证明了内源性金属在指纹残留物亲水性有机成分中的共定位。然后进行了额外的实验来研究外源性金属（例如硬币和化妆品）的来源如何转移到潜伏指纹中并在潜伏指纹中分布。最后，本研究报告了初步评估环境因素（例如暴露于水环境）如何影响指纹内元素分布的情况。总之，这项研究的结果提高了我们对手指组成及其化学成分空间分布的现有认识，并有助于解释使用标准法医协议检测指纹时观察到的检测变化。
