1. Optical Detection and Charge-State Analysis of MALDI-Generated Particles with Molecular Masses Larger Than 5 MDa
- Author
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Chau-Chung Han, Huan-Cheng Chang, Yong Cai, Kuo Sj, Wen-Ping Peng, and Sahadevan Sabu
- Subjects
Range (particle radiation) ,Chemistry ,Analytical chemistry ,Fluorescence spectrometry ,Molecular Probe Techniques ,Nanoparticle ,Mass spectrometry ,Microspheres ,Charged particle ,Analytical Chemistry ,Molecular Weight ,Matrix-assisted laser desorption/ionization ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Nanotechnology ,Polystyrenes ,Fluorometry ,Physics::Atomic Physics ,Ion trap ,Particle Size ,Quadrupole ion trap ,Fluorescent Dyes - Abstract
Charged polystyrene nanoparticles are generated by matrix-assisted laser desorption/ionization (MALDI) and detected by laser-induced fluorescence (LIF) in a quadrupole ion trap. Employing the LIF technique, observations of individual fluorescent nanospheres (27 nm in diameter and containing 180 fluorescein dye equivalents) have been achieved with an average signal-to-noise ratio of approximately 10. With the trap operating at a frequency around 5 kHz, charge state analysis of the particles reveals that the number of charges carried by the spheres is between 1 and 10. It suggests a mass-to-charge ratio (m/z) in the range of 10(5)-10(6) for the MALDI-generated particles. To effectively trap such large particles (m5 MDa), damping of the particles' motions by using approximately 50 mTorr He buffer gas is absolutely required. Similar findings are obtained for particles with a nominal size of 1 microm in diameter, demonstrating that production of charged particles with a molecular mass as high as 10(12) Da is possible using the MALDI technique.
- Published
- 2002
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