Sodium measurements made by nondilutional ion-selective electrode methods may yield different results from those obtained by dilutional methods.Results determined by _____ methods are altered by specimens that have high lipid or protein levels.An advantage of the ______ method is that this method brings all samples to a constant ionic strength.Changes in the electrode surface are possible with ______ methods.

Question

Quizplus · Accepted Answer

Dilutional methods for measurement of sodium by ion-selective methodology are subject to influence by high lipid or protein levels in the patient sample.As lipid or protein levels increase, the percentage of plasma that is made up of water decreases.During dilution, only the water phase is diluted, which results in falsely low sodium results in the presence of increased lipid or protein levels.Nondilutional methods are not subject to this limitation.Frequently, however, it is desirable to measure total ion activity/concentration.In this case, dilution with a diluent that will displace ions from complexing molecules is utilized.Thus dilutional methods are desirable despite this limitation.In addition, dilutional methods establish a constant ionic strength so that variations in ionic strength do not become a complicating factor during analysis.Nondilutional methods suffer from potential interferences due to variations in ionic strength.Additionally, changes to the electrode surface are seen in nondilution methods because of the effects of direct contact with plasma components.

Sodium Measurements Made by Nondilutional Ion-Selective Electrode Methods May Yield