Solution to a hairy problem

Rebecca C. Jernigan, rebecca.jernigan@laurin.com

A single strand of hair can reveal much about a person, especially if you know how to look. Proper investigation can determine diet as well as any drugs or poisons the person may have been exposed to, and the hair’s growth keeps this information in a fairly accurate time line.

Researchers from LGC Chemical Metrology Laboratory and from the University of Oviedo in Spain are investigating the details of this time line. By identifying the proportions of specific sulfur isotopes in hair samples, they believe that they may be able to track the geographical movements of a person. This information could be useful when pinpointing the movements and locations of international crime suspects and victims.

Human hair can be used to create a time line of many things – poisonings, malnutrition and perhaps even travel locations. Photos courtesy of Rebeca Santamarìa-Fernández.

By combining a laser ablation system from the New Wave Research Div. of ESI Electro Scientific Industries of Portland, Ore., with a multicollector inductively coupled plasma mass spectrometer from Thermo Fisher Scientific GmbH of Bremen, Germany, the investigators sampled sections along the length of the hair with a higher resolution than that available using isotope ratio mass spectrometry coupled to an elemental analyzer – the conventional method for analyzing stable isotopic variations.

They focused on the most abundant isotopes found in hair keratin, sulfur-32 and -34, which account for 95 and 4 percent of the sulfur total present in keratin, respectively. The proportion of the isotopes varies slightly in response to the diet and geographical location of the hair’s owner, and this technique can measure and record these tiny changes.

By testing hair samples longer than 4 cm from three volunteers – two permanent residents of the UK and one who had spent six months traveling between Croatia, Austria, the UK and Australia – the researchers determined that, although sulfur isotopic variations in the nontravelers’ hair were very small, there were significant variations in the traveler’s hair sample.

Rebeca Santamarìa-Fernández uses a laser ablation system attached to a multicollector inductively coupled plasma mass spectrometer (LA-MC-ICP-MS) to examine the sulfur isotopes in strands of human hair.

The lead investigator of the study, Rebeca Santamarìa-Fernández, believes that the technique could be used in forensic investigations and health-related studies, although a comprehensive database for the isotopes would have to be in place for users to make sense of the information.

To further their research, the scientists plan to perform a larger study involving 100 volunteers, gathering information on the participants’ diet, lifestyle, geographic origin and recent travels, and investigating the correlation with the sulfur, carbon and nitrogen isotopic variations found in their hair samples to give them a better understanding of the factors that influence the variations.