Forensic discrimination of ceramics by laser ablation
—Inductively coupled plasma mass spectrometry

Abstract

  Since we are always surrounded by ceramic products, it may be collected from the scene of the crime. In this study, we aimed to establish the discrimination methods for these samples. From the elemental mapping obtained by X-ray fluorescence analysis, Ca and Zn were recognized at the surface, Si, K, Ti and Fe were found inside. However, since scarce information was provided it was difficult to find a difference among samples by X-ray fluorescence analysis. We performed trace elements analysis using laser ablation-inductively coupled plasma mass spectrometer (LA-ICP-MS) for ceramic samples. Some elements such as Sc, Ti, V, Mn, Fe, Co, Zn, Ga, Rb, Sr, Zr, Cs, Ba, La, Ce, Pb, Bi were found from the inside of the ceramics. Among them, V, Co, Ga, Rb, Sr, Cs, Ba and Pb were selected to calculate index and didn't have mass spectral interference with other elements and uneven distribution. 23 kinds of commercially available samples were collected and analyzed by LA-ICP-MS. As the tendency that the signal intensity ratio differed among different samples was observed, forensic discrimination could be performed using this intensity ratio as an indicator. Discriminations between samples were performed by the threshold based on standard deviation called 2SD method. Moreover discrimination results were evaluated and the number of discriminated pairs among all were combinations. Only about 32-84% was discriminated when using single index, but they were improved to about 95% by the combination of multiple indices. When taking account the origin of the samples, 227 of 228 pairs (99.6%) which clearly originated differently were discriminated. This method shown in this paper is quite effective for the discrimination of ceramics.