Abstract: A controller for an open port interphase mass spectrometry (MS) probe automates analysis of samples, providing continuous, fast, and reproducible sampling. The sensed position of the probe above the sample surface is used by the controller in a feedback loop to set the probe at the proper position on the sample surface for sampling. One embodiment uses a conductance based sensor signal as input to the feedback loop to determine contact of the probe with the sample surface and to set the probe position according to a selected conductance value. The controller allows fast and automated sampling of uneven sample surfaces with minimal sample preparation while minimizing the risk of clogging the MS probe.