A method of isolating 99Mo produced using a (n,γ) reaction according to example embodiments may include vaporizing a source compound containing 98Mo and 99Mo. The vaporized source compound may be ionized to form ions containing 98Mo and 99Mo. The ions may be separated to isolate the ions containing 99Mo. The isolated ions containing 99Mo may be collected with a collector. Accordingly, the isolated 99Mo may have a relatively high specific radioactivity and, in turn, may be used to produce the diagnostic radioisotope, 99mTc, through radioactive decay.