Simultaneous Measurement of Potassium in Plasma and Red Blood Cells by Pulsed Chronopotentiometric Ion-Selective Electrodes

The purpose of this research was to develop an effective method to measure potassium ion concentration in plasma and red blood cells (RBC\u27s) simultaneously. Potassium concentration is vital for health due to its role in the nervous system, cardiovascular system, and in maintaining osmotic balance between cells and interstitial fluid. A concentration outside of the normal range can lead to muscle weakness, decreased reflex response, and even respiratory paralysis and cardiac arrhythmia. Recent research has suggested that simultaneous measurement of extracellular and intracellular potassium concentrations is important for diagnosis of hypertension. The most common methods for potassium measurement used today are Classical Potentiometry and Flame Photometry. These techniques are effective to measure potassium in plasma and/or RBC’s after separation and subsequent sample preparations, but inadequate for simultaneous measurement. Classical Potentiometry is time-consuming as it requires calibration prior to every analysis. Atomic Photometry requires intensive sample preparation and can only find overall potassium concentration. Pulsed Chronopotentiometry using potassium ion selective electrodes was fast, reusable, and able to measure both extracellular and intracellular potassium concentrations simultaneously. Here, current pulse of varying magnitudes was applied to extract ions from the sample into the membrane. Depletion of ions at the membrane’s surface occurred at the limiting current when the concentration of ions in the solution could no longer sustain the flux (movement) of potassium across the membrane. Our electrochemical measurement detected the break in potential in the form of a potential drop on the potential-current response curve. This limiting-current was proportional to the potassium ion concentration, according to the Sand Equation. After measuring potassium concentration in unlysed blood, lysing agents were added and continual measurements were performed. These gave the total concentration of potassium after lysing was complete. Simple arithmetic allowed for intracellular concentration to be calculated