Large PEG separation

[doddlebop]

Hi all--
Can anyone recommend a method to separate large PEG's (1 million and higher). I used a standard C18 column for smaller ones and it worked wonderfully. I cannot separate these larger ones though, and have not seen a lot of publications on these larger ones.
TIA

[Uwe Neue]

The usual method for such problems is size-exclusion chromatography (SEC): Ultrahydrogel with water as the mobile phase. As a matter of fact, PEGs are used as standards in SEC.