The kinetics of H-D exchange on trimethylamino-borane in bi- and triphase systems involving sulfonate cation exchangers in the D+ form show that the rate of the isotope exchange is lower in triphase systems in comparison to the liquid-liquid extraction system; nevertheless the yield of the deuterated product in polymeric deuterating systems is essentially much higher than that obtained in applying liquid deuterating agents. The cation-exchange resin when applied in triphase system demonstrates ambivalent behavior, acting as a catalyst toward deuterio-exchange reaction and as a suppressor toward the hydrolysis of TMAB. The hydrolysis of TMAB results in the formation of trimethylamine which accelerates the hydrolysis and inhibits the H-D exchange by saturation of the SO3- resin sites. The immobilization of the aqueous phase (D2O) in swollen ion exchanger creates unique conditions for isotope exchange, completely suppressing hydrolytic side reactions, and pure deuterated product can be achieved in quantitative yield.