Two ways to use ISE probe ion selective electrodes

The ISE probe ion selective electrode analysis method is a quantitative analysis method based on the measurement of the electromotive force of the battery. The ion selective electrode produces different potentials due to the different activities of potassium and sodium ions. This potential change is determined by the ion activity and is proportional to the concentration of potassium and sodium ions.

There are two methods to measure potassium and sodium with ISE probe ion selective electrode, one is direct potential method and the other is indirect potential method.
The direct potential method is that the sample (serum, plasma, whole blood) or standard solution enters the ISE pipeline without dilution for potential analysis, because ISE only selectively generates potential for dissociated ions in the water phase, which is different from the fat and protein in the sample. The volume occupied is irrelevant. For some serum samples with severe hyperlipidemia and hyperproteinemia without electrolyte imbalance, since the amount of water per unit volume of serum is significantly reduced, after quantitatively drawing samples for dilution, and then measuring with indirect potential method or flame photometry, false positive results will be obtained. However, the direct potential method can truly reflect the activity of ions in serum water in line with physiological significance (the volume occupied by lipids and proteins has nothing to do).