Ambient aerodynamic desorption/ionization method for microparticle mass measurement.

An ambient desorption/ionization method, named aerodynamic desorption (AD), was proposed for the in situ rapid mass measurement of microparticles. The AD method exploited the discontinuous atmospheric pressure interface (DAPI) to generate a pulsed airflow, which was used to desorb the microparticles under atmospheric pressure. Various microparticles, e.g., bacteria, cell, polystyrene, synthetic diamond, and silica particles, with different size and surface component were successfully desorbed. Similar to that in the conventional laser-induced acoustic desorption (LIAD) method, these microparticles were desorbed as precharged ions in the AD process and the charge number was largely relevant to the particle size. However, compared with LIAD, the sensitivity of the AD method was higher. A lower concentration of particles was required for the analysis. In addition, the construction and sampling process of AD source were much simpler. All types of liquid, solid, or/and gaseous samples can be directly sampled under ambient condition. As a demonstration of this AD method, the in situ mass analysis of red blood cells (RBCs) and E. coli bacteria were carried out using a homemade ambient AD mass spectrometer consisting of AD source, QIT mass analyzer, and charge detector. Their mass and mass distributions were obtained successfully.