ISOTOPE ID: Chesson uses her CRDS instrument to characterize the isotopic signatures of different foods.JAMES EHLERINGER
Analytical chemist Lesley Chesson likes making experiments easier. It started during graduate school at the University of Utah, where she studied stable isotopes of oxygen and hydrogen in beverages consumed in standard American diets, including the milk served with McDonald’s Happy Meals. Chesson wanted to use the beverage’s isotopic signature to see whether fast-food chains sourced their milk locally or shipped it long distances. Her search for the ideal instrument to measure isotopes in liquids led her to a small tabletop device which uses cavity ring-down spectroscopy (CRDS)—a method that detects isotope concentrations by measuring the decay of light passed through a gaseous sample—and spits out data in about 10 minutes.
Ratios of the heavy isotopes of oxygen and hydrogen, 18O and 2H, to the ...
