The invention generally relates to systems and methods for analyzing a sample from a surface. In certain aspects, the invention provides systems that include a sample introduction member that has an inlet, an outlet, and an opening along a wall of the sample introduction member. The sample introduction member may be configured such that the opening couples with a surface that includes a sample in a manner in which molecules of the sample enter the sample introduction member via the opening and exit the sample introduction member via the outlet. A mass spectrometer is configured to receive the molecules of the sample.