PEGs have small amounts of anti-oxidants added to them by the manufacturer. I think different manufacturers may use different compounds.
And you might imagine that PEGs themselves with their -OH groups go from alcohol to adelhyde to carboxylate. -----Original Message----- From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jacob Keller Sent: Wednesday, August 24, 2011 2:18 PM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] Aging PEGs A while ago I measured the pH's of old and new PEGs and found them very different, and internally attributed all "old vs new PEG issues" to pH. Upon reflection, this seems too simplistic. Are there other known mechanisms of crystallization capacities of PEGs of various ages? Jacob Keller ******************************************* Jacob Pearson Keller Northwestern University Medical Scientist Training Program cel: 773.608.9185 email: j-kell...@northwestern.edu *******************************************
