Nanotube Coating Brings Handheld Mass Spectrometry Closer To Reality

By Joel Lindsey

A team of researchers from Purdue University and the Indian Institute of Technology Madras has developed a system that could make mass spectrometry devices much smaller, more affordable, and more readily accessible for medical testing and other applications.

In a report published by the Indian journal Angewandte Chemie, the team outlines details of the project, in which they worked with an analysis process called PaperSpray ionization. Through this process, paper used to collect chemical samples is coated with carbon nanotubes, which, according to the report, significantly decreases the voltage necessary to run mass spectrometry analyses.

“This is a big step in our efforts to create miniature, handheld mass spectrometers for the field,” R. Graham Cooks, Purdue’s Henry B. Hass distinguished professor of  chemistry, said in an article published on Purdue’s website. “The dramatic decrease in power required means a reduction in battery size and cost to perform the experiments. The entire system is becoming lighter and cheaper, which brings it that much closer to being viable for easy, widespread use.”

The carbon nanotube coating acts like a series of tiny antennas that work together to create a particularly strong electrical field with the application of a relatively small level of voltage. The electrical current then turns the mixture of solvent and residue collected on the paper into little droplets that contain ionized molecules. These droplets are vacuumed into the mass spectrometer, where they are identified by their mass.

According to Thalappil Pradeep, professor of chemistry at the Indian Institute of Technology Maddras and co-leader of the project alongside Cooks, 1 volt of electricity over a few nanometers of the nanotube assay creates an electrical field equivalent to 10 million volts over one centimeter.

“The trick was to isolate these tiny, nanoscale antennae and keep them from bundling together because individual nanotubes must project out of the paper,” Pradeep said. “The carbon nanotubes work well and can be dispersed in water and applied on suitable substrates.”

Cooks and Pradeep report that in addition to requiring notably less electricity to conduct a mass spectrometry reading, their PaperSpray ionization process also helps reduce background noise in the final mass spectrometry readings.

“Under these conditions, the analysis is nearly noise free and a sharp, clear signal of the sample is delivered,” said Cooks. “We don’t know why this is — why background molecules that surround us in the air or from within the equipment aren’t being ionized and entering into the analysis. It’s a puzzling, but pleasant surprise.”

Image credit: Purdue University photo/Courtesy of Thalappil Pradeep