Abstract:

Nail is a kind of connective tissue with a thyroid structure on the back of fingertip. In the field of forensic science, nail, as a new biological information carrier, has a high application value. The hydrogen and oxygen stable isotopes in water would be continuously fixed by nail keratin and kept in the nail statically after the person ingested water, thus the temporal and spatial information of the person’s life were recorded, which is of great significance for the screening of individual identity. In this paper, the hydrogen and oxygen stable isotope in fingernails of residents in Khotan, Hami and Altay were analyzed by Elemental Analyses-Stable Isotope Ratio Mass Spectrometry, and the model was constructed by discriminant analysis to carry out the pattern recognition. The results showed that the ratios of hydrogen and oxygen stable isotopes in the fingernails of residents in three different cities were different. There was a significant difference between the δ²H value in Khotan residents and that in Hami and Altay. Hami and Altay had more overlapping of δ ²H value, but the difference was relatively small. The distribution of δ ¹⁸O value about three cities was overlapped without any significant difference. In the discriminant model, the difference between Khotan and Hami, Altay was very obvious, while difference between Hami and Altay was partly coincidence. Compared with DF₂ discriminant function, each sample was obviously distinct from each other under DF₁ discriminant function. The overall classification accuracy of 85 samples was 95.29 %, and the 9 verified samples were classified exactly, which was ideal. In conclusion, the combination of EA-IRMS and discriminant analysis can provide an accurate and effective method for the analysis of hydrogen and oxygen stable isotopes in fingernails of different urban residents, which has certain reference significance.

Key words: Hydrogen oxygen Stable Isotope, Nail, Traceability, Forensic Science