Researchers are developing a plasma-based technology to enable generalized use of mass spectrometry (MS) with new instruments that can analyze a much broader range of molecular species than current technology allows.
Current MS instruments are bulky, expensive, and typically specialize in one class of chemicals, discouraging widespread use outside of a specialized lab setting. Better technology is needed to make more flexible instruments. Research being conducted at Rensselaer Polytechnic Institute (Troy, NY, USA) uses an atmospheric-pressure glow discharge plasma – a partially ionized gas that can be made stable at room temperature and pressure – to probe samples for elemental and molecular species, and could lead to user-friendly MS analyses with broad capabilities.
“Ideally we want one system that can detect everything, and we want to be able to take that system into the field to test materials on site,” said Prof. Jacob Shelley of Rensselaer Polytechnic, “We’re trying to make a more flexible instrument that will allow us to detect many things simultaneously.”
The hitch is that current instruments can only analyze molecules that are in gas state and ionized, which means that most samples must first be processed. Current MS relies on a variety of time-consuming processing methods that separate and ionize molecules prior to analysis. And depending on the method, samples (e.g. tissues, pharmaceuticals, or foods) may be destroyed during processing.
The biggest challenge to developing a generalized processing method is the chemistry needed to ionize the molecule. Most methods rely on specific chemistries that favor ionization of one class of molecules over another. Prof. Shelley team is developing a method that takes advantage of the unusual properties and chemistries of plasmas, which are rich in free-moving ions and electrons, and therefore highly interactive. Although the most commonly known plasmas are extremely hot (at nearly 10,000 degrees Kelvin, some plasmas rival the sun’s temperature), the team is working with more recently developed glow discharge plasmas that are stable at room temperature and atmospheric pressure.
In his lab, Prof. Shelley demonstrates an experimental instrument so benign it can test samples ionized from a fingertip, and so versatile it can detect molecular species from small amounts of metals to large labile biomolecules like peptides and proteins. In developing the technology, the team has used the instrument to detect counterfeit honey, to quantify harmful toxins in freshwater algal blooms, and to screen the raw materials used in nutritional supplements.
“The plasma is useful as an ionization source because it makes a diverse range of chemistries available,” said Prof. Shelley, “It may make it possible to ionize a broad class of molecules, which could lead to more generalized instruments.”
This research is enabled by the New Polytechnic vision, a transformative emerging paradigm for higher education, which recognizes that even the most talented person working alone cannot adequately address global challenges and opportunities. It helps Rensselaer serve as a crossroads for collaborations to address some of the world’s most pressing technological challenges.