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