Identification of detergents for forensic fiber analysis

Nondestructive discrimination of red silk single fibers using total reflection X-ray fluorescence spectrometry and synchrotron radiation X-ray fluorescence spectrometry

In a strangulation case, when a necktie is used as a murder weapon, the dyed silk single fiber becomes an important evidence sample to solve the crime. Dyed silk single fibers contain elements, such as Cr and Co, which are obtained from dyeing using metal mordants. Currently, there are no nondestructive and sufficiently sensitive elementary analytical methods for the forensic analysis of single fibers. Therefore, in this study, eight commercially available red silk samples were collected and used for total reflection X-ray fluorescence (TXRF) and synchrotron radiation X-ray fluorescence (SR-XRF) spectrometry. Benchtop TXRF detected both S in the silk protein and Cl and Ca, which are elements absorbed from the environment by silkworms, but also Cr, which is a dyeing derivative for metal mordants. The presence of Cr and Zn, in addition to the Zn/Cr signal intensity ratios, was reported to be particularly useful identifiers. In SR-XRF, the presence of Cr, Co, Zn, and Br and the Zn/Cr signal intensity ratios were reported to be useful discriminating indicators. In this study, the nondestructive discrimination capabilities of TXRF and SR-XRF measurements for the samples were found to be 85.7% and 100%, respectively. Therefore, we propose a combination of TXRF and SR-XRF as a new nondestructive single fiber identification method for forensic science. Moreover, if partial destruction of a single fiber is allowed, the observation of the cross section and micro-Fourier-transform infrared spectroscopy measurements is useful for identifying red silk fibers.

Detection and diversity of fluorinated oil- and water-repellent coatings on apparel fibers

Fluorinated coatings, often used for oil and water repellency and stain resistance in fabrics, are potentially persistent forensic fiber markers. However, they have received limited attention because of challenges in their detection caused by the small size of a single fiber and thin nature of stain-resistant coatings. Here, we utilize a sensitive fluorine-selective analytical technique to detect and evaluate diversity of fluorinated coatings in apparel. Twelve clothing items marketed as stain-resistant were tested with nine showing oil- and water-repellent properties. Fluorinated pyrolysis products of single fibers from all of the nine items were detected by gas chromatography coupled to plasma-assisted reaction chemical ionization mass spectrometry (GC-PARCI-MS), indicating the prevalence of fluoropolymer coatings in stain-resistant clothing articles. Furthermore, three major classes of fluorinated coatings were identified via principal component analysis of pyrogram patterns. The classes were coating-specific and did not correlate with fiber core and color, highlighting a robust detection methodology. To evaluate the effect of fiber lifting in crime scenes, fibers from the 9 clothing items were used to develop a multinomial logistic regression model based on pyrogram principal components. The model was then tested using fibers subjected to contact with Post-it^® notes. The test set fibers were sampled from the clothing items of the training set and from three additional garments of differing color but the same brands as the training set. The coating classes were predicted with 98.4% accuracy, confirming robust classification of fiber coatings using py-GC-PARCI-MS regardless of fiber color, core, and fiber lifting.

Interpol review of fibres and textiles 2016-2019

This review paper covers the forensic-relevant literature in fibres and textiles from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20Review%20Papers%202019.pdf.

An overview on forensic analysis devoted to analytical chemists

The present article has as main aim to show analytical chemists interested in forensic analysis the world they will face if decision in favor of being a forensic analytical chemist is adopted. With this purpose, the most outstanding aspects of forensic analysis in dealing with sampling (involving both bodily and no bodily samples), sample preparation, and analytical equipment used in detection, identification and quantitation of key sample components are critically discussed. The role of the great omics in forensic analysis, and the growing role of the youngest of the great omics -metabolomics- are also discussed. The foreseeable role of integrative omics is also outlined.