26. April 2019

Light Nudges for Isotopes

BAM research provides conclusive proof of origin from strawberries to poison gas, which could soon put a stop to counterfeiters and war criminals

Chemist Carlos Enrique Abad Andrade successfully completed his doctorate at BAM in February. Credit: © WISTA Management GmbH

After having been awarded his PhD, Carlos Enrique Abad Andrade did not see any reason to turn his back on the BAM Federal Institute for Materials Research and Testing in Adlershof. Instead he decided to continue to make use of the almost perfect high-tech equipment and the trust of his experienced colleagues to advance his research on highly complex spectroscopic analysis of isotopes.

Four years of research. Years of fundamental research in the working group of Helmut Becker-Ross and Stefan Florek at the ISAS – Leibniz Institute for Analytical Sciences – as well as that of isotope researchers in the 1930s. Carlos Enrique Abad Andrade, who moved to Berlin from Venezuela as a student, is sceptical: “Is it possible to explain all this to a laymen’s audience in three minutes?!”

Seeking an answer, the chemist made it to the finals of the “FameLab” competition for science communication in 2018. In the video of his talk on YouTube, he makes two unidentical figures dance. They symbolise isotopes of varying mass. Atoms of the same element, which vary in mass because they have the same number of protons but a different number of neutrons. When such isotopes are excited with light, they react differently in terms of intensity and speed depending on their mass.

To put it bluntly, Abad nudges isotopes with light and observes their reaction to see where they come from. This is made possible since Earth’s initially homogenous isotope distribution has been altered by wind, rainfall and geological events over the course of billions of years in a way that every place on Earth has an individual isotopic fingerprint. “By looking at the interaction of light and material, we can precisely determine a sample’s origin,” he explains. This enables the researcher to verify whether asparagus from Beelitz, Parmigiano-Reggiano, and expensive wines are genuine or fallen victim to fraudulent labelling.

Abad has other, even more serious ideas: “Isotope analysis also enables us to obtain conclusive proof of the origin of poison gas and radioactive substances.” This could contribute to raising the threshold for their use.

To do this, it is important to clarify the method’s limits. This is what the chemists at BAM are currently working on in cooperation with physicists and geologists, who use elements like boron, magnesium, and lithium to create the foundation for “molecular absorption spectroscopy using a continuum source.” Becker-Ross and Florek started by developing the technology for atoms and then two-atom molecules. Upon concluding their working group, they transferred the technology and all their equipment to the BAM institute – and continued to support “their Abad” in word and deed. “I benefit from their support and their trust,” he says. He looks over their shoulders very closely, especially when they start tinkering. “They come from a generation that seeks to find solutions of their own in the lab. That way they make significant contributions to improving prototypes,” he explains. Abad seeks to continue this tradition with the engineers of Analytik Jena AG, who are cooperating with BAM on process development.

At the lab, the researcher shows us how the molecular absorption spectroscopy (MAS) works. After a baseline measurement, he draws some magnesium and fluoride solution into a pipette and transfers some of it into a graphite furnace. Through a camera, one can see the drop evaporate in a pipe about the size of a pencil. The temperature skyrockets to 2,000 degrees Celsius. “Now, transient magnesium-fluoride-molecules are forming, which we get to form a stable connection for a few seconds using precise temperature settings,” he explains. While he is doing this, the machine lights up. It’s time to excite the molecules using light from all over the spectrum from ultraviolet to near-infrared. The spectrum changes depending on the wavelength absorbed by the elements. Moreover, the excited isotopes produce tiny swings on a picometre scale that are now becoming visible on a screen in 3D. Abad calls up other sample’s spectrums from the US and Japan for comparison. The differences are obvious. These visualised differences in wavelength of just a few picometres will soon contribute to putting a stop to war criminals and counterfeiters.

By Peter Trechow for Adlershof Journal