Distance-of-flight Mass Spectrometry

The Story

While working on a method of collecting the entire MS/MS set of responses in a single spectrum, I realized that a component of my hypothetical instrument was a new kind of mass spectrometry. It is one in which the different-massed ions, while spread out along their flight path as in a snap-shot of ions in TOF MS, would be driven to an array of detectors. I named the technique DOF MS. The basic concept is shown in the illustration for this category.

A challenge was how to achieve ion focus at each mass’s detection distance. I performed a simulation study which revealed the method—a combination of constant momentum ion acceleration and a linear ion mirror. This method achieved energy focus, including ion turn-around (a first) and relegated space focus to the ion source. This was also the point at which I “retired” in that I no longer had an active research lab.

Happily, Gary Hieftje expressed an interest in DOF MS, I became an Adjunct Professor at Indiana University, and Gary’s group built and tested a proof-of-principle instrument. His students developed the concept further through a number of papers and patents, including one that won the ASMS Award for Paper of the Year.

The use of a separate charge detector for each increment of ion mass has the advantages of unlimited high mass detection, charge accumulation for increased sensitivity, and wider dynamic range. It’s disadvantage, still a problem, is the availability of an array of charge detectors at a reasonable price. It is the one area of research that I am still involved with, collaborating with Professor Steven Ray at SUNY, Buffalo. Stay tuned.

Coauthors and coinventors in this work are Gareth Dobson, Gary Hieftje, Alexander Gundlach-Graham, Steven Ray, Charles Barinaga, David Koppenaal, Jeremy Felton, Anthony Corado, and Elise Dennis.

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