While I don't fully understand your question, possible answers could be:

- You differentiate the degradation products by their retention times.

- As these are essentially more hydrophobic compounds compared with glucose, they should show up at higher retention times when using a C18 column (where glucose is basically not retained at all).

- To separate different degradation products, a suitable separation method has to be developed.

- Solely the retention time doesn't tell you which compound it is.

I hope, this helps somehow.