How to calculate the buffer capacity for polyprotic acids? specifically H2PO4 --- HPO42- + H30+

as the title says. Is b= amount of OH-/ H3O divided by volume of buffer x change in pH wrong to use with polyprotic acids? Can I calculate the buffering capacity of a sodium phosphate buffer made up of NaH2PO4 and NaH2PO4 using this formula?


