The invention generally relates to systems for analyzing a sample and methods of use thereof. In certain aspects, the invention provides systems that include an ionization probe and a mass analyzer. The probe includes a hollow body that has a distal tip. The probe also includes a substrate that is at least partially disposed within the body and positioned prior to the distal tip so that sample extracted from the substrate flows into the body prior to exiting the distal tip. The probe also includes an electrode that operably interacts with sample extracted from the substrate.