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Published January 1, 2011 | metadata_only
Journal Article

Switched Ferroelectric Plasma Ionizer (SwiFerr) for Ambient Mass Spectrometry


We present the implementation of a switched ferroelectric plasma ionizer (SwiFerr) for ambient analysis of trace substances by mass spectrometry. The device utilizes the ferroelectric properties of barium titanate (BaTiO_3) to take advantage of the high electric field resulting from polarization switching in the material. The source comprises a [001]-oriented barium titanate crystal (5 × 5 × 1 mm) with a metallic rear electrode and a metallic grid front electrode. When a high voltage AC waveform is applied to the rear electrode to switch polarization, the resulting electric field on the face of the crystal promotes electron emission and results in plasma formation between the crystal face and the grounded grid at ambient pressure. Interaction with this plasma and the resulting reagent ions effects ionization of trace neutrals. The source requires less than 1 W of power to operate under most circumstances, ionizes molecules with acidic and basic functional groups easily, and has proven quite versatile for ambient analysis of both vapor phase and aspirated powdered solid samples. Ionization of vapor phase samples of the organics triethylamine, tripropylamine, tributylamine, and pyridine results in observation of the singly protonated species in the positive ion mass spectrum with sensitivity extending into the high ppb range. With acetic acid, deprotonated clusters dominate the negative ion mass spectrum. Aerodynamic sampling of powdered samples is used to record mass spectra of the pharmaceuticals loperamide and ibuprofen. Chemical signatures, including protonated loperamide and deprotonated ibuprofen, are observed for each drug. The robust, low power source lends itself easily to miniaturization and incorporation in field-portable devices used for the rapid detection and characterization of trace substances and hazardous materials in a range of different environments.

Additional Information

© 2011 American Chemical Society. Published In Issue: January 01, 2011; article ASAP: December 03, 2010; received: May 26, 2010; accepted: November 2, 2010. This material is based on work supported by the National Science Foundation under grant number CHE-0416381. The authors also wish to acknowledge funding from the Beckman Institute at Caltech. E.L.N. acknowledges a Graduate Research Fellowship in Analytical Chemistry from Pfizer Analytical Research and Development, Groton, CT.

Additional details

August 19, 2023
August 19, 2023