Abstract: The most sensitive analytical technique of ⁹⁹Tc is isotope dilution mass spectrometry with ⁹⁷Tc as yield tracer. ⁹⁷Tc was obtained by the irradiation of 2 g natural ruthenium metal. ⁹⁷Tc is isolated from the sample by combined ionexchange chromatography, precipitation and ion-association solvent extraction technique. ⁹⁹Tc^m and ¹⁰³Ru are used as tracers in this method. The chemical recovery of Tc is more than 70% and the decontamination factor is more than 10^７.