Ethnicity and gender from elements in hair

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  • Published: May 8, 2014
  • Author: Steve Down
  • Channels: Atomic / UV/Vis Spectroscopy / Proteomics / Base Peak / Raman / NMR Knowledge Base / Chemometrics & Informatics / Infrared Spectroscopy / X-ray Spectrometry / MRI Spectroscopy

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It seems to be becoming quite fashionable to devise chemical tests for ethnicity and gender. Recently, the Francese group at Sheffield Hallam University announced that peptides and proteins left behind in fingermarks can pinpoint the gender of their owners, in research funded by the Home Office which might help to identify criminal suspects. In a more unusual study, chemists in the US revealed how volatile compounds in the much-neglected biofluid earwax could divulge a person’s ethnicity.  

Now, it’s the turn of hair. Diane Beauchemin and Lily Huang from Queen’s University, Kingston, Ontario, used ICP-OES to examine hair samples from men and women of various ethnicities and found that the elements present can differentiate between ethnic types as well as gender, as they explained in Journal of Analytical Atomic Spectroscopy.

Unlike some ICP methods which require digestion of the hair followed by nebulisation, they analysed powdered hair to reduce losses of the target analytes and minimise the possibility of contamination. The solid sampling electrothermal vaporisation ICP-OES method was used to measure a host of elements then principal components analysis and linear discriminant analysis were used to analyse the data.

LDA performed much better than PCA and identified the group of elements comprising Li, Mo, S, Sr, Cr, K, Ni, Zn and Pb that correctly predicted the general ethnicity of 13 people as East Asian, South Asian or Caucasian. A panel of four elements, consisting of Mg, S, Sr and Sn, correctly predicted gender. The lower number of elements required for the gender is consistent with the lower number of possibilities compared with ethnicity.

In blind tests, the geographical origin of the people tested, which could influence the elemental content of their hair via working conditions and environmental issues, was found to be an irrelevant factor. However, the subjects tested only lived up to 430 km from the area where the main samples were collected, so this would have to be verified over greater distances, across borders.

This is first report of the technique being applied to the determination of general ethnicity and gender from hair. Although it needs to be tested on greater populations across more ethnicities, it appears to hold promise for the forensic lab, to help in areas such as corpse identification.

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