Radio-isotopes are different forms of the same element, differing only in the number of neutrons (and thus mass) but having the same chemical properties. Chromatography separates based primarily on physical or chemical interactions that relate to solubility, adsorption, volatility, size, or charge. Since isotopes of an element have virtually identical chemical behaviour, chromatography is generally not a suitable method for separating radio-isotopes. Techniques like mass spectrometry, gas diffusion, or centrifugation are typically used for isotope separation based on mass differences.