Direct analysis in real time mass spectrometry (DART-MS) of discrete sample areas without heat damage

Abstract

Direct analysis in real time mass spectrometry (DART-MS) analyzes intact object surfaces by exposing them to a stream of heated gas. The continuous gas flow prevents discrete sampling of a central surface area, and the high temperatures cause visible discoloration and deformation of heat-sensitive materials. A time-controlled mechanical shutter was installed in front of a DART ion source mounted at an angle to the ion inlet for discrete sample surface analyses. Interior areas on stationary surfaces were studied without exposing the surrounding material of the greater object. The temperature exposure profile and spatial dimensions of areas impacted by the heated ionization gas were characterized to optimize DART positioning. Physical effects from DART of thermally sensitive photographs were recorded at various exposure times and temperatures, and high resolution mass spectra were acquired without causing visible or microscopic damage to photograph images. The shutter afforded 0.25 s DART-MS analysis time that was as qualitatively informative as exposures for tens of seconds.