- Physiological Buffers are chemicals used by the body to prevent sudden, rapid changes in the pH of a fluid. As explained in our discussion of the Henderson-Hasselbalch Equation, buffers are most able to resist changes in pH when the pH of the solution is close the unique pK of the buffer. Consequently, physiological buffers must be chemicals whose pKs are near the normal blood pH which ranges from 7.37 - 7.42. The primary buffers of the ECF appear to be inorganic phosphate (pK 6.8) and bicarbonate (pK 6.1). However, as explained in their respective pages, the physiological importance of the bicarbonate buffer vastly exceeds that of inorganic phosphate.