OK, I am reopening the thread as OP is a newcomer with locked access to PMs, so this is the only way of clarifying the situation.
So far you have not explained why you are trying to prepare the gel and what is your background, so we no choice but to assume you are breaking the rules.
Quoting your report:
And Im fully aware how to make buffers!
So basically you wrote you have to prepare a buffer, but you can't find information in the literature how to make one. Now in your report you wrote you know how to make the buffer - so where is the problem? Start with the sorbic acid pKa and follow from there.