Abstract: Based on the fusion of Ge, Sn and Sb with NH4I to form volatile iodides, it was proposed to apply this phenomenon as techniques of sample pretreatment and separation to determination of the 3 elements in geological samples by AFS. It was shown that when the sample (0.5 g) was mixed and fused with NH4I (1 g) in a bi-bulb glass tube at 350 ℃ for 10 min, iodides of the 3 elements were formed, volatilized and condensed on the inner wall of glass tube. Hence, Ge, Sn and Sb were separated from the sample matrix. The condensate was dissolved with HCl into a beaker, and the solution was evaporated to dryness with HNO3 to expel iodine. The residue was dissolved with HCl and H2O2 and the solution was used for AFS determinations. Detection limits (3s/k) found for the 3 elements were 0.08, 0.06, 0.08 μg·L-1 respectively.