Separation and Measurement of ²²⁹Th

²²⁹Th spike is usually performed to determine the concentration of ²³²Th and ²³⁰Th in evironmental samples. In this paper, a robust procedure was employed using tandem columns of anion resin for milking high purity ²²⁹Th from ²³³U bulk solution. Considering the chemical yields of ²³²Th and ²³⁸U approximately 100%, the procedure of separating Th and U istopes was reliable to prepare ²²⁹Th spike. A custom-made natural thourim standard solution was used for the reverse isotope dilution measurement and multi-collector ICP-MS was employed to measure the concentration and purity of ²²⁹Th spike. The accurate and reliable determination shows that the concentration of ²²⁹Th is 1.959×10^-9(1±0.5%) g/g, the relative standard isotope ratio of ²³⁰Th and 229Th is 3.322×10^-3. The uncertainty results suggest that the prepared ²²⁹Th spike may be suitable to thorium isotopes measurement in environment samples.