Question

How do you prepare a 50:50 buffer solution?

Answer 1

It's mean that for preparation of this buffer, you can use acetic acid. In calculation for preparation, please notice to density (to change gram to the liter) and purity (assay) of Acetic acid. 

After obtain the final volume of acetic acid to buffer preparation, you can be using NaOH to adjustment of pH in 4.6.