I would like to use aqueous two phase extraction (ATPE) to extract crude proteins from microalgae. Studies have shown that most of the proteins are soluble at pH 11. So, I thought of using K3PO4 as one of the components for the ATPE and the other component could be PEG (molecular weight will be tested to find the best one). However, is it necessary to keep the pH constant by using a buffer especially in determining the binodal curve?