Three peaks corresponding to Cl+2 will be recorded. The peaks are for isotope 35, both 35 and 37 and for isotope 37. Mass spectrometer has the ability to detect and separate isotopes, even those differing by a single atomic mass unit. When chlorine isotopes are analysed by mass spectrometer, either peak M or M+2 can be obtained. The intensity ratio in the isotope pattern depends on the natural abundance of the isotopes.
