Microscale transport physics during atomic force microscopy mass spectrometry and improved sampling efficiency

Abstract

This paper reports improvements of atomic force microscopy (AFM) mass spectrometry (MS), in which ∼1 attoliter of analyte is desorbed by a heated AFM cantilever tip and analyzed with a mass spectrometer. Decoupling the AFM sampling apparatus from the MS system enabled analysis of the microscale transport physics independent of analyte ionization efficiency. Using this approach, we find that the transport efficiency is governed by the air velocity during sampling, and not mass flow rate as reported in the literature. We also find that an unheated sampling tube results in higher efficiency compared to a heated tube. Optimization of the transport parameters improved the system efficiency by 2.5-fold over the state of the art.