An alternative ionization paradigm for atmospheric pressure mass spectrometry: Flying elephants from Trojan horses

We propose an alternative for production of multiply charged ions that is based on the recent discovery that laser ablation of certain common matrix-assisted laser desorption/ionization (MALDI) matrixes produce multiply charged ions at atmospheric pressure (AP) that are similar in charge state distribution to ions produced by electrospray ionization (ESI). In ESI and AP–MALDI, ions are primarily produced at AP before being transferred to the vacuum region of the mass analyzer. In this new laserspray ionization (LSI) method, the ionization mechanism is proposed to be similar to ESI, but with a solid rather than a volatile liquid solvent. Unlike in ESI, desolvation does not occur in the AP region, but in a heated AP to vacuum transfer region. Here we propose that highly charged droplets rather than naked ions pass the AP to vacuum entrance aperture before the multiply charged ESI-like ions are released into the viscous gas flow. Such a process offers a new and possibly highly sensitive method for ion formation in MS.

Multiply charged ions are produced from charged matrix/analyte liquid droplets within a heated ion transfer tube linking atmospheric pressure and vacuum.Figure optionsDownload high-quality image (312 K)Download as PowerPoint slide