A new method developed by the Brown team dramatically reduces sample loss, paving the way for more accurate and efficient protein analysis.
PROVIDENCE, R.I. [Brown University] - Mass spectrometry is a powerful technique that allows scientists to break down and identify the building blocks of just about anything by measuring the mass of the tiny particles of which something is comprised. It has a major limitation, however - about 99% of the sample being measured is typically lost before analysis even begins.
This rate of loss hampers the technology's potential. It reduces accuracy and sensitivity, wastes resources and complicates sample preparation, which can lead to additional errors. That might not be the case much longer, though. A research team from Brown University has developed a new method for transferring the ions that mass spectrometers analyze, dramatically reducing sample loss so nearly all of it remains intact.
"The conventional technique for producing ions for mass spectrometry, called electrospray ionization, basically involves a very sharp needle getting placed just in front of the mass spectrometer, hitting it with an electric field that pulls out a spray of charged droplets that eventually dry out to produce bare ions that make it into the mass spectrometer from open air," said Nicholas Drachman, a physics Ph.D. student at Brown who led the work. "Basically, it's a process where you're really spraying your sample all over the place to produce these ions and only get a tiny portion of them into the mass spectrometer's vacuum for analysis. Our approach skips all of that."
Called a nanopore ion source, the advancement overcomes a longstanding logjam in science and has the potential to revolutionize mass spectrometry technology. The Brown team describes the novel innovation in Nature Communications.
The key is a tiny capillary the researchers developed that has an opening about 30 nanometers across - roughly 1,000 times smaller than the width of a human hair. For comparison, the conventional needle used in electrospray has an opening of about 20 micrometers across, which is about 600 times bigger than the tube developed at Brown.
The new nanotube also has the unique ability to transfer ions that are dissolved in water directly into the vacuum of a mass spectrometer, rather than producing a spray of droplets that must be dried out to access the ions. In addition, conventional mass spectrometers typically draw in a significant amount of gas along with the ions during the process, necessitating several stages of vacuum pumps to pull in the ions. The new breakthrough means that gas won't need to be pumped out, because it won't get sucked in, according to the researchers.
"Rather than place it in front of a mass spectrometer and generate this spray of droplets, we just place it directly into the mass spectrometer skipping this messy spray, drying and vacuum process," Drachman said. "By generating ions in the vacuum directly, it drastically reduces the pumping requirements, which should significantly simplify the complex hardware of mass spectrometers."
