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The determination of noble metals such as Ir, Au and Ag in the ancient coins has been studied. For the measurement of the activity of 192Ir, 198Au and 110mAg, radiochemical separations including solvent extraction and ion-exchange chromatography were applied to reduce the interference of high energy γ-ray emitted from various radionuclides with long half-life. As a results, 10-11 g/g level of Ir could be detected and it was found that the three kinds of the detection limits, i.e., critical, detection, quantitative limit, calculated by the method proposed by Currie, were enhanced. Prior to the re-irradiation with neutron, inactive carrier was added in order to determine the recovery yield of Ir in the radiochemical separation. The average recovery yields of Ir, Au and Ag in the 5 coins were 65.3%, 98.5%, 99.5%, respectively.
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