Simultaneous Determination of Sodium(I) and Potassium(I) by Adsorption Voltammetry

In 0.05mol/dm3 tetrabutylammonium iodide (Dimethylformamide as solvent) buffer solution (pH=4.5), the reduction peaks of Na+ and K+ are very close. After dibenzo-18-crown-6 is added in, K+ may form complex with it. The complex can be reduced at the hanging mercury drop electrode, and gives a new reductive peak at −1.80 V which is more negative than the reductive peak of Na+. The peak current of the two peaks are proportional to the concentration of Na+ and K+ in the range of 1.0×10−8∼1.0×10−6 mol/dm3 and 2.0×10−9∼4.0×10−6 mol/dm3 respectively. The detection limits are 5.0×10−9 mol/dm3 and 6.0×10−10 mol/dm3 separately. The proposed method has been applied to the determination of Na+ and K+ content in banana and its peel.