ABSTRACT
The X-ray fluorescence under grazing incidence condition (XRF-UGI) was applied for the direct analysis of aerosol filters. Particulate matter less than 2.5 microns (PM2.5) was collected hourly on polytetrafluoroethylene filters using a continuous PM monitor with a virtual impactor method. Although the sampling mass is in trace amounts of 5-30 µg, the metallic contents, such as V, Cr, Mn, Fe, Zn, and Pb, can be measured at sub-ng m-3 detection limits. The effects of the non-uniformity and poor flatness of the PM filters were discussed with regard to the measurement repeatability. The relationship between the XRF-UGI intensities and the mass concentrations obtained via conventional X-ray fluorescence (XRF) analysis was confirmed using the fundamental parameter method. Finally, quantification was successfully demonstrated using the XRF-UGI results with the relative sensitivity factors.
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.
Subject(s)
Silk , Spectrometry, X-Ray Emission/methods , Textiles , Color , Forensic Sciences/methods , Metals/analysis , Microscopy , Silk/chemistryABSTRACT
Total reflection X-ray fluorescence (TXRF) spectrometry was applied to a forensic discrimination of single polyester fibers. In a non-destructive direct measurement of 5 mm long single fibers used for forensic references, trace metallic elements such as Ti, Sb, Ge, Mn, and Co, found in additives and catalyst residues, were detected using a benchtop TXRF spectrometer. The individual elemental compositions of the fibers were identified, and correlations between the compositions and manufacturers were established using principal component analysis (PCA). Black polyester fibers sampled from the car trunk mats were also analyzed. Several fibers were found to contain both Sb and Ge, elements that characterize different polymerization catalysts; this indicates that the fibers were composed of recycled materials. The TXRF and SR-µXRF spectra showed similar patterns for the fiber samples that were analyzed.
