[Study on the Specific Complexation of GMDTC and Metal Ion]

Objective: Study the response of GMDTC to cadmium ions and metal ions in vivo to determine whether GMDTC are specifically complexed with cadmium ions to provide a reference for the safety and dfficacy of GMDTC. Methods: Complexometric titration, HPLC and HPLC-MS were applied to research the complexation reaction of GMDTC and various metal ions. The molecular ion peak of GMDTC, GMDTC-Cd complex and GMDTC-Pb complex also detected by LC-MS. Additionally, the initial structure was determined by DFT simulation method. Results: Results of complexometric titration and HPLC detection showed that GMDTC characteristic absorption peak area was proportional to the concentration of itself and there was no color change and peak time change when the GMDTC mixed with Ca(2+), Fe(2+), Mg(2+), Zn(2+). However, the color changed to black transition when the GMDTC mixed with Cu(2+) and the color changed from yellow precipitate to light yellow transparent transition when GMDTC mix with Hg(2+). Moreover, the peak area as well as the retention time has changed a lot which indicated that a chemical reaction has already happened. When the GMDTC mixed with Cd(2+) and Pb(2+), the color has changed from pale yellow to colorless transparent and the peak area of GMDTC has increased a lot. Finally, the GMDTC-Cd complex ratio both of which are 2:1 were calculated based on the results of LC-MS instrument and atomic calculations. Conclusion: The specific cadmium chelating agent GMDTC can not react with the Ca(2+), Fe(2+), Mg(2+), Zn(2+), but it can react chemically with Cu(2+) and Hg(2+), even specific complex with Pb(2+) and Cd(2+).