A chemical analysis machine comprising a liquid phase chromatograph comprising, in turn, a chromatography nano-column with an inner diameter that is smaller than or equal to 100 μm, a mass spectrometer with an electronic ionization source, and a joining assembly interposed between the liquid phase chromatograph and the mass spectrometer. The joining assembly comprises a microcapillary tube having an inner diameter smaller than or equal to 50 μm and having a first end, which is directly connected to an outlet end of the nano-column so as to receive the liquid phase, and a second end, which is housed inside a vaporization microcannula where an inert gas flows. The vaporization microcannula is partially engaged by the microcapillary tube and has an end facing the inside of an ionization chamber of the mass spectrometer. The vaporization microcannula is subdivided into a first part, which is subjected to the action of a heating device, and a second part, which is kept at room temperature and has a length that is greater than or equal to 2 cm. The microcapillary tube occupies the inside of the entire second part of the vaporization microcannula and has an end portion that is arranged inside the first part and has a length that is less than or equal to 5 mm.