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Analytical Chemistry

Paper Spray Ionization With A 3-V Battery

Carbon nanotube-coated paper reduces the voltage needed for paper spray ionization from 3 kV to 3 V

by Celia Henry Arnaud
March 31, 2014 | A version of this story appeared in Volume 92, Issue 13

Credit: Angew. Chem. Int. Ed.
An applied potential of 3 V is enough to ionize samples in nanotube-coated paper.
Photo of a nanotube-coated paper spray with battery and mass spectrometer inlet.
Credit: Angew. Chem. Int. Ed.
An applied potential of 3 V is enough to ionize samples in nanotube-coated paper.

Like most ambient sample ionization methods used for mass spectrometry, paper spray usually requires voltages in the kilovolt range. Such high ionization voltages can be dangerous and require large power supplies. Rahul Narayanan, Depanjan Sarkar, and Thalappil Pradeep of the Indian Institute of Technology, Madras, in Chennai, and R. Graham Cooks of Purdue University now show that they can ionize samples with potentials as low as 3 V by using paper coated with carbon nanotubes (Angew. Chem. Int. Ed. 2014, DOI: 10.1002/anie.201311053). In a demonstration, the group used the low-voltage method to collect mass spectra of pesticides, medicines, amino acids, and other compounds. Without the nanotube coating, more than 500 V is required to produce any signal, they say. Electron micrographs of the coated paper show that nanotubes protrude from the surface. The researchers suggest that the nanotubes act as electrodes that induce an electric field between the paper tip and the mass spectrometer inlet. More recently, the team has found that they could obtain spectra by applying just 1 V, Pradeep says.


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