The objective of this work is the study and characterization of anodized indium tin oxide (anodized-ITO) as a sodium ion selective electrode and differential structures including a sodium-selective-membrane/anodized-ITO as sensor 1, an anodized-ITO membrane as the contrast sensor 2, and an ITO as the reference electrode. Anodized-ITO was fabricated by anodic oxidation at room temperature, a low cost and simple manufacture process that makes it easy to control the variation in film resistance. The anodized-ITO based on EGFET structure has good linear pH sensitivity, approximately 54.44 mV/pH from pH 2 to pH 12. The proposed sodium electrodes prepared by PVC-COOH, DOS embedding colloid, and complex Na-TFBD and ionophore B12C4, show good sensitivity at 52.48 mV/decade for 10(-4) M to 1 M, and 29.96 mV/decade for 10(-7) M to 10(-4) M. The sodium sensitivity of the differential sodium-sensing device is 58.65 mV/decade between 10(-4) M and 1 M, with a corresponding linearity of 0.998; and 19.17 mV/decade between 10(-5) M and 10(-4) M.
Keywords: EGFET; anodic oxidation; anodized indium tin oxide; sodium ion.