Possibilities of laser ablation-inductively coupled plasma-mass spectrometry for diamond fingerprinting

Abstract

In this paper the performance of laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) for the fingerprinting of diamonds of different deposits has been evaluated. The results show that, after optimization of the experimental conditions, the LA unit used (a homogenized 193 nm excimer laser with a flat-top beam profile) is capable of controlled ablation of the diamonds and the sensitivity of the ICP-MS device suffices for the detection of more than ten elements. 31 diamonds originating from four different mines—Premier (South Africa), Orapa (Botswana), Udachnaya (Russia) and Panda (Canada)—were the subject of the study. Every diamond was ablated on 8 different spots for 30 s (crater diameter: 120 µm; energy output: 200 mJ; repetition rate: 20 Hz) and the median of the eight integrated signals was considered as the representative value for subsequent statistical analysis. Under these conditions, the total mass of material removed from a single diamond was ∼16 µg. Finally, 9 elements were selected for fingerprinting purposes (Al, Hg, Na, Ni, Pb, Sb, Sn, Ti and Zn) and different pattern recognition techniques (ternary plots, cluster analysis and partial least squares analysis) were used in order to classify the data. The results obtained can be considered as promising, especially for the partial least squares approach, providing that appropriate data standardization is carried out.