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

Abstract

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.

Interpol review of fibres and textiles 2019-2022

“…Komatsu et al discriminate 8 types of red silk fibres with non-destructive total reflection X-ray fluorescence (TXRF) and synchrotron radiation X-ray fluorescence (SR-XRF) spectrometry based on the presence of Cr and Zn (TXRF) and Cr, Co, Zn, and Br (SR-XRF) as well as the Zn/Cr signal intensity ratios [ 79 ]. In their opinion SEM-EDS is often unsuitable for detecting trace elements in silk fibres and involves a destructive technique.…”

Non‐destructive analysis of hollow‐shaped single fibers using X‐ray computed tomography

“…In recent years, various studies using synchrotron radiation have also been conducted [7][8][9][10][11][12]. For example, Nishiwaki et al [8,9] and Komatsu et al [10] used X-ray fluorescence spectrometry (XRF) and detected trace elemental compositions related to catalysts used during the production of fibers.…”

“…In recent years, various studies using synchrotron radiation have also been conducted [7][8][9][10][11][12]. For example, Nishiwaki et al [8,9] and Komatsu et al [10] used X-ray fluorescence spectrometry (XRF) and detected trace elemental compositions related to catalysts used during the production of fibers. Minami et al [11] and Honda et al [12] used small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) to identify periodic structures and orientations of fibers related to the fabrication process.…”

“…Synthetic fibers have various cross-sectional shapes depending on the shape of the spinneret used in their manufacture, and round, trilobal, polygonal, and hollow shapes are available. Generally, fabrication of cross-sectional shapes of individual fibers requires preprocessing and destruction [1,10,[13][14][15][16].…”

Development of the Microemulsion Electrokinetic Capillary Chromatography Method for the Analysis of Disperse Dyes Extracted from Polyester Fibers

“…For the analysis of fiber microtraces, nondestructive methods, mainly spectroscopic [ 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ], are used initially. However, sometimes they are not able to give an unambiguous answer about the similarity of the evidence sample and comparative material if the sample does not have individual features.…”