Thanks for the reply. If I go the other direction, first creating a Pb complex with EDTA and then lower the pH to 1.0, will it remain stable (i.e. remain complexed)? Would HEDTA and DTPA work better or worse than EDTA at pH between 1.0 and 2.0? Are there any other chelants that you can think of I should try in the lab experiments along with EDTA and possibly HEDTA or DTPA.