The Periodic Table of Elements, a staple in schools across Canada, is basically an ingredients list for everything that makes up our world. And as of yesterday, 14 of those ingredients changed, thanks to work by National Research Council (NRC) metrologists, whose desire to push the limits and attempt what has never been done continues to fuel new discoveries.

The NRC Metrology team’s research has led to the first accurate measurement of the isotopic composition of iridium, the key element behind the leading theory of the mass extinction of dinosaurs. Accurate knowledge of an element’s isotopic composition is essential in many branches of chemistry and physics. Until now, iridium—like many elements on the Periodic Table—lacked a calibrated isotope ratio measurement.

Using state-of-the-art instrumentation known as multi-collector inductively coupled plasma mass spectrometry, or MC-ICPMS, the team at the National Research Council was able to test the limits of high-precision isotope ratio measurements to perform the world’s first calibrated isotope ratio measurements of the element.

Overview

• The change to the standard isotopic composition of iridium is the fourth National Research Council-led change to the Periodic Table of Elements.
• Iridium is important to geoscientists and paleontologists for its abnormally high concentration in sediments that would have been exposed during the Earth’s last mass extinction event. Given that iridium is mostly found in meteorites, it is the main argument behind the hypothesis that a massive impact is what caused the extinction of dinosaurs and many other living things.
• Proper isotope ratio measurements are difficult to obtain because mass spectrometers are not faithful in preserving the isotope ratios due to the different speeds at which certain ions travel.
• This work was part of the National Research Council’s Certified Reference Material of iridium, IRIS-1, now available online.

Related

• Determination of the Isotopic Composition of Iridium Using Multicollector-ICPMS (ACS Publications)
• Standard atomic weights of 14 chemical elements revised (The International Union of Pure and Applied Chemistry)

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