Urinary Buffers Nephron cannot produce urine at pH≤45. in order to excrete more h+ the acid must be buffered H+ secreted into the urine tubule and combines with hpo 2- or nh HPo42+H+—H2Po4 NH3+H+—NH4+Urinary Buffers ◼ Nephron cannot produce urine at pH < 4.5. ◼ IN order to excrete more H+, the acid must be buffered. ◼ H+ secreted into the urine tubule and combines with HPO4 2- or NH3 . ◼ HPO4 2- + H+ H2PO4 - ◼ NH3 + H+ NH4 +