[en] The separation technique is modified to meet the optimum condition for urinalysis of uranium in routine work. The procedures are based on co-precipitation of uranium with alkaline earth phosphate followed by anion exchange separation. Purified uranium is reduced to IV prior to co-precipitation with neodymium as fluoride. The baseline concentration of uranium isotopes in un-exposure occupations are found to be 0.0021 - 0.0344, 0.0002 - 0.0043 and 0.0044 - 0.0478 p Ci/l for U-238, U-235 and U-234, respectively. The average baseline concentration in term of natural uranium is 0.031 ± 0.018 microgram per litre with the average ratio U-234/U-238 1.72