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Sonic spray mass spectrometry
A Hirabayashi1, M Sakairi, H Koizumi
1Central Research Laboratory, Hitachi, Ltd., Tokyo, Japan.
Analytical Chemistry
|September 1, 1995
Summary
A new sonic spray ionization method efficiently produces ions from dilute solutions for mass spectrometry. This technique, utilizing a methanol-water spray, detects neurotransmitters like dopamine at low concentrations.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Chemical Physics
Background:
- Traditional ionization methods face challenges with dilute solutions.
- Understanding ion formation mechanisms is crucial for sensitive analysis.
Purpose of the Study:
- To develop and characterize a novel sonic spray ionization (SSI) method.
- To investigate ion and charged droplet formation in SSI.
- To analyze dilute neurotransmitter solutions using SSI-MS.
Main Methods:
- Developed a sonic spray ionization system using a fused-silica capillary with coaxial gas flow.
- Analyzed positive ions from dilute catecholamine solutions (e.g., dopamine) using a quadrupole mass spectrometer.
- Compared SSI with ion spray ionization (ISI) for dilute solution analysis.
Main Results:
- Protonated dopamine molecules detected from a 10 nM solution.
- Ion intensities correlate with gas flow rate.
- Most ions originate from charged droplets, challenging traditional charging models.
- Proposed a new model for charged droplet formation based on ion concentration distribution.
Conclusions:
- Sonic spray ionization is effective for analyzing dilute solutions, including neurotransmitters.
- The study provides insights into the fundamental mechanisms of ion and charged droplet formation in SSI.
- The proposed charging model offers a new perspective on electrospray ionization processes.