What is the primary factor affecting the efficiency of isotope elution from a Mo99/Tc99m generator?

The primary factor affecting the efficiency of isotope elution from a Mo99/Tc99m generator is indeed the time interval between elutions. This is because the elution of technetium-99m (Tc-99m) from the molybdenum-99 (Mo-99) source relies on the radioactive decay of Mo-99, as it produces Tc-99m. If the interval between elutions is too short, there may not be enough Mo-99 to produce a sufficient quantity of Tc-99m for elution, as the decay hasn't reached an adequate level of activity. Conversely, if the interval is too long, the activity of the Mo-99 source may diminish, again affecting the yield of Tc-99m. Therefore, optimizing the interval is essential for maximizing the efficiency of the elution process and ensuring that an adequate amount of Tc-99m is available for medical procedures.