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 variations.
"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 Santamara-Fernndez 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 Santamara-Fernndez. 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 mon
FECYT - Spanish Foundation for Science and Technology