Abstract: A double-barreled sodium ion-selective microelectrode based on N, N'-bis(dibenzyl)-3,6-dioxaoctyl diamide, with tip diameter of 2.5μm, has been constructed. The microelectrode shows a linear relationship in the range of 10^-3～5×10^-1mol·dm^-3(25℃)in NaCl solution.The selectivity coefficients with respect to K⁺, Mg²⁺, and Ca²⁺ are 0.053, 6.2×10^-4, and 5.8×10^-3, respectively. The response characteristics of the microelectrode for Na⁺ in body fluids was measured. The Na⁺ concentrations in some clinical microsamples were determined using this microelectrode.

Key words: ion-selective microelectrodes, biomedical measurements, clinical analysis