<p>Sulphur in just one hair could blow a terrorist's alibi</p>
A group of researchers from the LGC Chemical Metrology Laboratory in the
United Kingdom and the University of Oviedo, Spain, have come up with a method
to detect how the proportions of isotopes in a chemical element (atoms with an
equal number of protons and electrons but different numbers of neutrons) vary
throughout the length of a single hair. The mid-term objective is to be able to
use these methods to track the geographical movements of people, including
international crime suspects and victims.
In order to carry out this study, which is published this month in the
journal Analytical and Bioanalytical Chemistry, the scientists focused on
the most abundant sulphur isotopes in hair keratin – sulphur-32 (32S), which
accounts for about 95%, and sulphur-34 (34S), which makes up around 4%. This
proportion can change slightly in response to people's diets and if they travel
from one country to another, and the technique is able to detect these small
"The new method is based on combining a laser ablation system and
multicollector inductively-coupled plasma mass spectrometry (abbreviated to
LA-MC-ICP-MS)", Rebeca Santamaría-Fernández of LGC, lead author of the study,
tells SINC. To summarise, the laser makes contact with the selected fraction of
the hair, generating an aerosol, which later ionises within plasma, with the
spectrometer providing the exact proportions of the sulphur isotopes.
"The advantage of this method compared with others is the high resolution
resulting from use of the laser", points out Santamaría-Fernández. This advance
has enabled the scientists to confirm that the sulphur variations in hair can be
linked to peoples' geographical movements.
The traveller experiment
The researchers collected hair samples of more than 4cm in length donated by
three volunteers. Two were permanent residents in the United Kingdom, while the
third – dubbed "the traveller" – had spent the past six months in Croatia,
Austria, the United Kingdom and Australia.