Abstract View
Laminar Flow Sublimation-Deposition Systems for Nanoparticle Growth with MALDI Matrices
KE' LA KIMBLE, Michelle Heilig, Brock Mitts, Li Li, Kimberly Prather, Christopher J. Hogan, University of Minnesota
Abstract Number: 20
Working Group: Instrumentation and Methods
Abstract
Aerosol Time-of-Flight Mass Spectrometry (ATOFMS) enables single particle chemical analysis via laser ionization. Traditional laser ionization approaches are well suited towards small molecules, but are challenging to apply to high molecular mass analytes. Conversely, matrix- assisted laser desorption ionization (MALDI) is an established route to ionize peptides, whole proteins, and nucleic acids, i.e., biomolecules. MALDI-MS has been demonstrated for aerosols, but sparingly applied due to the lack of a repeatable, portable method to combine aerosol particles with an appropriate matrix material (material that absorbs laser light and facilitates ionization) without requiring separate particle collection and transfer steps. We have developed a laminar flow sublimation-deposition system to coat individual particles repeatably with MALDI matrix materials in-flight. Based on the operation principle of condenser-saturator systems in laminar flow condensation particle counters, the sublimation-deposition system passes particles over a heated bed (70-90o C) of MALDI powder (ferulic acid and 2,4 dihydroxybenzoic acid in the present effort), leading to a heated, saturated aerosol. Using a water jacket-cooled tube at 0o C, deposition of the matrix material following sublimation proceeds onto particles. We find that particles as small as 15 nm can be grown to near 300 nm using this approach, and that for particles in the 15 nm – 100 nm size range, the resulting size is relatively insensitive to initial particle size, though strongly sensitive to sublimator temperature. As particles in the 300 nm size range can be detected and ionized significantly more efficiently in ATOFMS systems than sub-100 nm particles, matrix sublimation-deposition has the combined effects of (1) enabling MALDI-MS of aerosol particles and (2) improving “hit-rate” for sub- 100 nm particles.