Forensic Discrimination of Arsenous Acids by Morphological Observation by the Scanning Electron Microscope and Inductively Coupled Plasma-Atomic Emission Spectrometry

Abstract

In a poisonous crime case, clarifying identity of the poisonous materials between actually used in the crime scene and the confiscated from the suspect's neighborhood is required. In this report, the examination of the discriminating capability of these compounds was conducted, using 13 As2O3 samples of known origins and manufacturing methods. By the observation using the scanning electron microscope, three morphological differences were recognized. The first one exhibited an euhedral crystal with octahedral shape, the second one had spherical shape and the third one was crystal showing significant cleavages. Furthermore, by energy-disperse X-ray analysis disclosed, only Lα,β and weak Kα,β peaks of arsenic in all samples, and the discrimination was impossible. Because of this reason, inductively coupled plasma-atomic emission spectrometry (ICP-AES) was adopted for the discrimination of the As2O3 samples by trace impurities. The compared heavy elements were barium (Ba), lead (Pb), antimony (Sb), selenium (Se) and tin (Sn) which were selected by a pre-qualified analysis of arsenous samples. As a result, significant difference was observed among these samples by comparison of the 5 elements, and their patterns were classified into three categories. It was considered that estimation of the origins and manufactured methods were possible from the morphological observation by scanning electron microscope and the comparison at trace impurities by ICP-AES.