Electrosprayed droplet impact/secondary ion mass spectrometry
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A new ionization method, electrosprayed droplet impact ionization (EDI), has been developed for mass spectrometry. The charged droplets formed by electrospraying 1 M acetic acid aqueous solution are sampled through an orifice with a diameter of 400 μm into the first vacuum chamber, transported into a quadrupole ion guide and accelerated by 10 kV after exiting the ion guide. The m/z of the primary droplet projectiles range from 10 000 to 50 000. The droplets impact on a dry solid sample deposited on a stainless steel substrate. No matrix was used for the sample preparation. The secondary ions formed by the impact are transported to a second quadrupole ion guide and mass-analyzed by an orthogonal TOF-MS. Intense molecular-related ions are detected for drugs, amino acids, peptides and proteins. EDI is found to be very sensitive to molecules present near the surface of the sample.
PACS.34.50.Dy Interactions of atoms and molecules with surfaces; photon and electron emission; neutralization of ions 36.40.Gk Plasma and collective effects in clusters 39.10.+j Atomic and molecular beam sources and techniques
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