A method of treating an adsorbent for a chromatographic separation. The method involves sonicating particles of an inorganic metal oxide having fragile edges in the absence of any alkylating or acylating agent to form smoothened particles of the inorganic metal oxide and washing the smoothened particles of the inorganic metal oxide to remove fine particulate matter to produce a treated adsorbent. The treated adsorbent can be used in a method of isolating a daughter radioisotope from a daughter radioisotope that is produced from the parent radioisotope by radioactive decay.