Use of LA-ICP-MS to analyse dental enamel in order to locate the geographical origin of teeth

Abstract

The investigation reported here involved the analysis of possum tooth samples by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) to determine whether or not the data obtained from the elemental composition of the dental enamel was sufficient to differentiate samples according to their geographical origin. The possum jaws were processed, and the teeth removed and cleaned and mounted on slides before analyses could be carried out. A LA-ICP-MS method was developed in order to obtain data for the tooth enamel. This involved optimising specific laser parameters, such as laser spot size, laser power, and acquisition time. It was also essential to determine the best calibration standard for the project, which proved to be NIST 612. Data was collected from samples from across ten different regions. The data was statistically analysed by Principal component analysis (PCA) and Linear Discriminant Analysis (LDA). It was found that some regions overlapped in the PCA, meaning they could not be 100% separated however, many regions could be distinguished, and it was determined, by that using LDA, 75.75% of the samples could be correctly grouped into their regions of origin. A further analysis was conducted once several regions were removed (for historical or statistical reasons), which greatly improved the results. 82.9% of the samples could be placed into their region of origin.