I have a water-soluble chitosan sample(modified by graft co-polymerization) and run it in GPC to determine its molecular weight. Unfortunately, no signals were detected. Anyone knows why?
You have to be more specific! By GPC are you using HPLC (normal phase or reverse phase). What is your detector (MS?)? What is your column? What is your injection volume? What is your mobile phase(s)? Is your chitosan an extractant (how?)? Is your chitosan soluble in the mobile phases?