The pH is too low and the EDTA is insoluble. You need to be above pH ~8.0. Your best bet is to try another chelator.
James On Feb 21, 2011, at 2:22 PM, Yibin Lin wrote: > Dear all, > > I got a lot of salt crystals in reservior solution (well solution), which > contains 0.1 M phosphate/citrate ph 4.2, PEG200 47%, EDTA-2Na 0-22mM. > Reservior solution appears crystals from 12mM EDTA. Could someone help me to > explain why? > > Thank you very much! > > Yibin >