How could I test the quality of old polyethylene glycol (PEG)? - (Nov/24/2013 )

Hi guys,

I'm setting up an experiment where plants will be imposed to PEG stress (or presumably osmotic stress), and I will observe their physiological responses (root architecture and shoot). I found a large batch of old PEG8000 (at least 15 kg) in our neighbor lab. The person who took care of the chemicals said that it's at least 6 years old. The PEG is stored in a large plastic bag whose end was tied up quite tightly, and this bag of PEG is stored in a closed-lid plastic barrel in a dry place. 

We would like to make use of this batch of PEG, but we aren't sure of its quality. Does anyone know the shelf life of PEG or how to test its quality? We are planning to use PEG6000 in the future if we run out of this batch of old PEG. Is PEG8000 different PEG6000 in any aspect?

I appreciate your help

PEG 6000 and PEG 8000 differ in respect to the molecular mass of the chains that form the compound (i.e. the number of ethylene-glycols that form the chain), otherwise they are the same.  I don't know how the length of the chain would impact the metabolism or physiology.

Most batches of compound come with lot numbers, contact the relevant supplier for more information.

not to partially contradict bob1 but, peg 6000 was renamed peg 8000 when they found that the average mass was 8000 and not 6000. in other words, they are the same (unless they have a new method of preparation where they control the size better and are really making 6000, where are you seeing peg 6000 being sold?).

peg is pretty stable, we've used one box of peg 8000 for at least 20 years with no change in effectiveness.

mdfenko on Wed Nov 27 14:00:42 2013 said:

not to partially contradict bob1 but, peg 6000 was renamed peg 8000 when they found that the average mass was 8000 and not 6000.

Heh, you learn something new...