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A novel method for the determination of 99Tc in water samples was developed using stable Re as a chemical yield tracer and TiCl 3 as a reducing agent. The influences of several experimental parameters, including TiCl 3 concentration, HCl concentration and reaction time, on the reduction of TcO 4 − and ReO 4 − as well as Ti(OH) 3 -TcO 2 -ReO 2 co-precipitation were investigated. Tc(VII) and Re(VII) retained on TK200 resin were effectively eluted by 5 mL of 1 mol/L NH 4 SCN, which can be directly mixed with the scintillation cocktail for liquid scintillation counting. The results show that the chemical behaviors of Tc and Re are very consistent in the whole procedure. The decontamination factors of potential interferences from β-emitting nuclides mainly released from nuclear fuel reprocessing plants were also evaluated, and the minimum detectable activity concentration was calculated to be 0.08 Bq/L for 99Tc in water samples with a counting time of 2 h. [Display omitted] • Re as a non-isotopic tracer was used for measuring 99Tc in 1 L water sample. • TiCl 3 was first used as a reducing agent. • TcO 4 − and ReO 4 − were eluted from TK200 resin using 5 mL of 1 mol/L NH 4 SCN, which can be directly used for LSC measurement. • The MDA was estimated to be 0.08 Bq/L for 99Tc with a counting time of 2 h. [ABSTRACT FROM AUTHOR]