It looks like the HPLC method for Disodium EDTA is pretty well established protocol using reverse phase columns and UV-Vis or DAD detectors. Two of the methods are listed below. However, if baseline fluctuations are issue, I would suggest repeated running the HPLC for prolonged period with false injections to clear out the debris in the column. You may also inject increasing concentrations of the compund in to know the exact peak (it will be the one increasing in peak area) /retention time of your compound.