Patent ID: 7767844

Claim:
A method for manufacturing a tetra-alkyl DTPA (Diethylene Triamine Pentaacetic Acid), comprising: (a) mixing a solution of DTPA and an alcohol in the presence of a catalyst in a dehydration apparatus; (b) refluxing said solution for 24 hours and neutralizing said solution with a sodium bicarbonate solution to obtain a penta-alkyl DTPA; (c) mixing said penta-alkyl DTPA, metal ion, and water and stirring for 2 hours while adding a strong base to obtain a solution comprising Cu 2 S and bubbling said solution comprising Cu 2 S with H 2 S, wherein said metal ion is selected from the group consisting of cupric chloride, cupric bromide, cupric sulfate and cupric nitrate; and (d) filtering said solution having Cu 2 S with filter paper, and obtaining a tetra-alkyl DTPA by column chromatography.