The present invention refers to a system comprising a gas field ion source (120) capable of interacting with a gas (182) to generate an ion beam (192) and an ion optics (130) configured to focus the ion beam onto a surface (181) of a sample (180) so that the ion beam can interact with a sample to cause particles (194) to leave the sample, wherein the ion beam has a spot size with a dimension of 10 nm or less at the surface of the sample. The system also comprises at least one detector (150), which is configured so that, during use, the at least one detector can detect secondary ions (194) emitted by the sample due to the interaction of the ion beam with the surface of the sample, wherein the at least one detector is further configured to analyse the detected secondary ions according to their mass. The system according to the present invention also comprises an electronic processor that can process information based on the detected secondary ions to determine information about the mass of the detected secondary ions.