Online MALDI-TOF MS using an aerodynamic lens assembly as a direct deposition interface.

This technical note reports a design utilizing an aerodynamic lens assembly to transport suspended sample particles directly onto the target plate and conduct in situ MALDI analysis. The design provides a new alternative method for online MALDI analysis. The matrix/analyte/salt-contained particles sampled by a nozzle are focused into a particle beam with an aerodynamic lens assembly and then deposited on the target plate directly. The deposited particles are in situ desorbed/ionized by a 266 nm laser beam with an incidence angle of 50 degrees. The generated ions are detected with a reflectron mass spectrometer capable of delayed ion extraction and ion gating. The MALDI-TOF mass spectra of poly(ethylene glycol) (PEG) 1000, 2000, and 4000 particles are obtained in the experiment. The initial experimental results demonstrate that the design can be used for online MALDI analysis.