Rhenium-188-N-(DEDC)₂/lipiodol (abbreviated as ¹⁸⁸ReN-DEDC, where DEDC=monoanionic diethyldithiocarbamate) is a clinically proven radiopharmaceutical for the therapy of unresectable hepatocellular carcinoma (HCC) through trans arterial radioembolization (TARE). A two-vial freeze-dried kit for the preparation of [¹⁸⁸ReN(DEDC)₂] complex using sodium perrhenate (Na¹⁸⁸ReO₄) obtained from a commercial Tungsten-188 / Rhenium-188 generator had been reported earlier. This method required addition of stipulated volume of glacial acetic acid into vial 1 by the user for efficient preparation of [¹⁸⁸ReN]²⁺ intermediate. An error in this step can result in low radiochemical yield of [₁₈₈ReN]²⁺ intermediate as well as sub-optimal pH of the reaction mixture for the second step, leading to poor radiochemical purity of ₁₈₈ReN-DEDC complex. In the present work, a solution to this problem was found by including an oxalate buffer of pH=3 in vial 1, eliminating the need for the addition of glacial acetic acid by the user. This modification not only made the kits more user-friendly, it resulted in significant improvement in the kinetics of formation of [₁₈₈ReN]²⁺ intermediate, wherein> 95% radiochemical purity could be achieved within 5 min incubation at ambient temperature. Moreover, the novel route for the preparation of [¹⁸⁸ReN]²⁺ intermediate may be applied to any radiopharmaceutical based on ¹⁸⁸ReN-core.