Gaseous ion formation by the cavitation occurred between aqueous solutions and the ultrasonically vibrating blade studied by mass spectrometry

- Gaseous ions generated by the ultrasonic atomization of liquids were measured by mass spectrometry for the first time.
- The ion signals are highly dependent on the surface-activity values of analytes.
- Ionizing reagents are H+, OH-, Na+, and K+ in solution.

Gaseous ions generated by the ultrasonic atomization of liquids were measured by mass spectrometry for the first time. The aqueous solutions of 10−5 M drugs, peptides, proteins, surface-active agents, rhodamine B, explosives saccharides, and polyethylene glycol were supplied to the edge of the ultrasonically vibrating blade (22 kHz) through the 20 μm i.d. silica capillary with the flow rate of 1 μL/min. The analytes were detected mainly as sodiated, protonated, or deprotonated forms. The ion signal intensities were highly dependent on the surface-activity values of the analyte ions, i.e., the higher the surface-activity values, the stronger the ion signal intensities. The addition of 0.5% acetic acid in the solutions led to the drastic decrease in ion signal intensities.

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