The present subject matter is directed to a method for separating proteins of plasma using pH adjustment including the steps of reconstituting Fraction III, Fraction IV, or plasma paste, in water for injection; adjusting pH value to 1 and temperature from 1° C. to 30° C.; centrifuging the resulting suspension at 6,000 rpm at 2-8° C. for 20 min; collecting the resulting paste 1 (P1) and supernatant 1 (S1); reconstituting P1 in WFI and adjust the pH to 2; and repeating step 3) to step 5) until the pH of supernatant reaches 14. According to the method, a new formulation of immunoglobulin is prepared from plasma Fraction III and Fraction IV.
