Wisconsin Alumni Research Foundation

Daniel D Ebeling

Lloyd M Smith

Michael S Westphall

Mark Andrew Scalf

The charge state of ions produced by electrospray ionization is reduced in a controlled manner to yield predominantly singly charged ions through reactions with bipolar ions generated using a Po alpha particle source or equivalent. The multiply charged ions generated by the electrospray undergo charge reduction in a charge reduction chamber. The charge-reduced ions are then detected using a commercial orthogonal electrospray TOF mass spectrometer, although the charge reduction chamber can be adapted to virtually any mass analyzer. The results obtained exhibit a signal intensity drop-off with increased oligonucleotide size similar to that observed with MALDI mass spectrometry, yet with the softness of ESI and without the off-line sample purification and pre-separation required by MALDI.

Charge reduction in electrospray mass spectrometry

Methods and devices for use in mass spectral analysis of samples. In particular, methods and devices for generating ions from liquid samples containing chemical species with high molecular masses. These methods and devices provide a continuous or pulsed stream of gas phase analyte ions of either positive polarity, negative polarity or both possessing either a selected fixed charge-state distribution or one that may be selectively varied with time. More specifically, ion sources with adjustable control of the charge-state distribution of the gas phase analyte ions generated are provided in which charged droplets and/or gas phase analyte ions are exposed to electrons and/or gas phase reagent ions generated by a reagent ion source to provide desired control. A corona discharge exemplifies the reagent ion source employed in charge-state distribution control. In a specific preferred ion source, a corona discharge is provided within a shielded region to minimize the deflection of gas phase analyte ions, charged droplets. The methods and devices provided herein are particularly well-suited to the analysis of polymers and biological species.

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Madison, WI, United States of America

Daniel D Ebeling