Development of an Atmospheric-Pressure Photoionization Source for VOC Detection With a Miniature High-Pressure Mass Spectrometer.

With the goal of sensitive, selective, targeted, and portable VOC quantification, an atmospheric pressure photoionization (APPI) source was developed for a miniature high pressure mass spectrometer, the MX908. The APPI source consists of a VUV lamp that was encased in a custom 3D-printed apparatus. Using m-xylene as the testing standard, the effects of pressure, axial RF voltage, aperture voltage, and humidity on the instrument were investigated and optimized. Operating at 0.8 Torr with ambient air as the buffer gas, the instrument showed linearity from 25 to 500 ppbV for benzene, toluene, ethylbenzene, and m-xylene without preconcentration.