Potassium is vital for the normal functioning of all cells. It is important for the regulation of our nervous and cardiovascular systems. In addition, it is critically important for the synthesis of proteins and metabolism of carbohydrates. Potassium exists in plasma (extracellular K<sup>+</sup> at 3.5-5.0 mM) and in red blood cells (intracellular K<sup>+</sup>, at 140-150 mM). The ability to accurately measure both the extracellular and intracellular potassium concentration is imperative for the early detection of illnesses such as hypertension and cardiovascular issues. Classical potentiometry is widely used for the measurement of extracellular potassium, and indeed annually, billions of measurements of potassium in plasma and whole blood is almost exclusively (&gt;99%) conducted by this method in clinical laboratories worldwide. However, potentiometry is unable to simultaneously measure both extracellular and intracellular potassium directly. We report a novel chronopotentiometric method for simultaneous measurement of intracellular and extracellular potassium. Here, a pulsed galvanostatic/potentiostatic technique is utilized. First the concentration of potassium in plasma is measured under galvanostatic pulse. Then the red blood cells are lysed by addition of nonionic surfactants during the potentiostatic pulse when the membrane is also regenerated. Following this, the total potassium concentration is measured under the next galvanostatic pulse. Finally, from separately measured hematocrit and the known fraction of water in the plasma and in the red blood cells, the concentration of intracellular potassium can easily be determined.

Simultaneous measurement of extracellular and intracellular potassium using chronopotentiometry

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