International nuclear safeguards verification relies on a precise count of isotope particles collected on swipes during International Atomic Energy Agency (IAEA) inspections of nuclear facilities and isolated through a series of lengthy chemical separations that can take about 30 days to complete. A faster measurement method developed at U.S. Oak Ridge National Laboratory (ORNL) could help IAEA analysts detect the presence of undeclared nuclear activities or material.

A commercially available pen-sized microextraction probe is coupled to a mass spectrometer to conduct precise, high-throughput analyses. The system extracts a solid from a swipe, ionizes it with a plasma torch, and measures the mass-to-charge ratio of its ions with the mass spectrometer. By sampling the swipe directly, chemists can eliminate the time-consuming acid digestion and chemical separation steps conventionally required.

View an animation of the ORNL microextraction system.

In testing the microextraction process, researchers were able to detect as little as 50 picograms of uranium, a volume 80 million times lighter than a grain of sand, in nuclear reference materials and measure the ratios of major and minor isotopes of uranium. The microextraction probe was also demonstrated to extract plutonium directly from a swipe surface.

The researchers propose adding a chromatography column to the system between the microextraction probe and the mass spectrometer. As actinide-containing solutions flow through the chromatography column, plutonium would be captured for later measurement while uranium would flow through to the mass spectrometer, improving elemental sensitivity and identification.

The study is published in Analytical Chemistry.

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