Molecular Surface Sampling and Chemical Imaging using Proximal Probe Thermal Desorption/Secondary Ionization Mass Spectrometry

摘要

Proximal probe thermal desorption/secondary ionizationnmass spectrometry was studied and applied to molecularnsurface sampling and chemical imaging using printednpatterns on photopaper as test substrates. With the usenof a circular cross section proximal probe with a tipndiameter of 50 µm and fixed temperature (350 °C), theninfluence of probe-to-surface distance, lane scan spacing,nand surface scan speed on signal quality and spatialnresolution were studied and optimized. As a compromisenbetween signal amplitude, signal reproducibility, and datanacquisition time, a surface scan speed of 100 µm/s,nprobe-to-paper surface distance of 5 µm, and lane spacingnof 10 µm were used for imaging. Under those conditionsnthe proximal probe thermal desorption/secondary ioniza-ntion mass spectrometry method was able to achieve anspatial resolution of about 50 µm as determined by thenability to distinguish surface patterns of known dimen-nsions that were printed on the paper substrate. It isnexpected that spatial resolution and chemical imagenquality could be further improved by using probes ofnsmaller cross section size and by incorporating a meansnto maintain a fixed optimal probe-to-surface distance realntime, continuously adapting to the changing topographynof the surface during a lane scan.