A Duke University team has improved upon an old technology by bringing modern data analytics to conventional mass spectrometers used for chemical detection.
Conventional mass spectrometers are typically very large, comparable in size to an oven or refrigerator. By using a technology called a “coded aperture,” the researchers believe they can shrink these devices, which could lead to portable mass spectrometers for detecting environmental or safety hazards in the field. Miniaturization would not impact the performance of the devices.
“This technique can improve the performance of classic mass spectrometers that already have a higher resolution than other types invented for scaling down,” said Amsden. “And there are lots of them. Duke alone probably has at least 50 for medical applications. So we’re hoping this can have a wide impact in the near future.”
The new technology can be likened to watching a solar eclipse in grade school, explained Jeff Glass, professor of electrical and computer engineering at Duke and principal investigator for the project. Students will sometimes poke a hole in a piece of cardboard to act as a lens, creating an image of the eclipse on the ground. The smaller the hole, the better the detail of the eclipse, but it also make it more difficult to see.
This is exactly the challenge faced when scaling down a mass spectrometer. Glass said the solution is to make many tiny pinholes to create an array of eclipses, and then to use a computer to reconstruct them into a single image, which provides the sharpness of the tiny pinhole with the brightness of a large pinhole.
The key is in knowing the pattern of the array of apertures—or “coded aperture.”
“In a typical mass spectrometer, the charged molecules pass through a thin slit, which defines your resolution,” said Glass. “When you try to shrink the instrument, you have to shrink the slit too. That means the number of ions (charged molecules) passing through is going to drop and you’re going to lose signal intensity. We got around this issue by using a several slits, which code the ions.”
“This idea was actually mentioned in a short article from 1970,” said Jason Amsden, a research scientist and manager of the project, added. “But nobody since then has had all the parts to put it together.”
Currently, the team is trying coded apertures in different versions of mass spectrometers to determine which would be best for creating scaled down, mobile devices for field use. In addition, the researchers are also working on demonstrating how these devices can detect trace amounts of methane to spot leaks in infrastructure and various explosives to thwart terror attempts.
This work was supported by the Department of Homeland Security Science and Technology Directorate and is currently supported by ARPA-E, Department of Energy.
