Hi, Dear all:
I was asked to make a new batch of PMMA-based polymer published before and characterize the molecular weight by GPC. The eluent used in the paper is DMF with 0.01 M lithium nitrate. We tried THF first because we have done the calibration for THF eluent, the polymer is well solube in THF, and we didn't want to go through the hassel of switching to DMF. I used a typical concentration: 1 mg polymer / 1 ml THF, but could not get any signal. What could be the possible reason?
Besides, what is the purpose of lithium nitrate in the eluent of DMF?
Thank you very much for your help.