The method about determination isotope ratio in 1ng Uranium and 100pg Plutonium samples has been developed by using IDMS with high isotope abundance spike 233U and 242Pu. The isotope ratio uncertainty in 1ng Uranium and 100pg Plutonium samples are about (20%, and it was mainly contributed by isotope ratio uncertainty of blend and spike. The blend and spike contamination from natural Uranium must be care in experiments.
By using active carbon powder as ionization enhance matter, the detect sensitivity of 239Pu ,which was 0.5 pg (1±0.15, 95% confidence level), was about 20 times that of the tradition method. The sub-picogram plutonium sample was determined quantitatively by isotope dilution mass spectrometry (IDMS).
