Laser Printer Printed Ion Sources for Ambient Ionization Mass Spectrometric Analysis of Volatiles and Semivolatiles

In this study, we demonstrated a facile method to fabricate ion sources using a laser printer for ambient ionization mass spectrometry (MS). Toner spots printed by a printer can readily facilitate ionizing volatile and semivolatile compounds derived from solid or liquid samples for MS analysis. The experimental arrangement involved positioning the toner-printed paper near the inlet of a mass spectrometer, which was subjected to a high electric potential (e.g., -6 kV). Volatile or semivolatile compounds deriving from the sample positioned below the metal inlet of the mass spectrometer were promptly ionized upon activating the mass spectrometer. No direct electrical connection or voltage application was required on the paper substrate. An electric field was established between the toner spot on the paper and the inlet applied with a high voltage to induce the dielectric breakdown of the surrounding air and water molecules. Consequently, ionic species, including electrons and cationic radicals, were generated. Subsequent ion-molecule reactions facilitated the production of protons for ionizing analytes present in the gas phase proximal to the inlet of the mass spectrometer. Deprotonated analytes were detected in the resultant mass spectra when employing the method in negative ion mode. This methodology presents a straightforward approach for analyzing analytes in the gas phase under ambient conditions utilizing an exceptionally uncomplicated experimental setup. In addition, the developed method can be used to detect trace 2,4-dinitrophenol, an explosive, with a limit of detection as low as ∼30 pg.