The Achilles' heel of potentiometric measurements, the liquid junction potential.
D002118:Calcium / Q000097:blood*; D004566:Electrodes; D006801:Humans; D011188:Potassium / Q000097:blood*; D011199:Potentiometry / Q000295:instrumentation*; D012964:Sodium / Q000097:blood*
D012964:Sodium; D011188:Potassium; D002118:Calcium