Method of synthesis

A method of producing di-choline salt of succinic acid (DISU), comprising

• obtaining a solution of choline in water or in a water miscible organic solvent selected from methanol, ethanol, 1- or 2-propanol, wherein the choline solution comprises one or more o-ethoxylated choline derivatives, wherein the amount of said one or more ethoxylated choline derivatives is above 0.3 wt. %;
• treating the choline solution with activated carbon (AC), wherein the weight ratio of AC to choline is 100-1:1-100;
• adding succinic acid, or succinic acid salt to the choline solution, wherein the molar ratio of choline to succinate is between around 2:1, preferably between around 2:1.01 and around 2:1.1, and allowing succinate to react with choline for at least 10 min at ambient temperature, thereby producing DISU dissolved in water or in the water miscible organic solvent;
• wherein the produced solution of DISU contains at least 40 wt. % DISU, preferably 50 wt. % DISU, and 1 at most 0.3 wt. % of the one or more o-ethoxylated choline derivatives.