Indirect photometric determination of potassium by solvent extraction with cuproine-copper (I)-tetraphenylborate

Abstract

It has been found that a small amount of tetraphenylborate (kalibor) ions are extractable into chloroform with cuproine-copper(I) chelate cations, and that there is a linear relationship between the absorbance and the kalibor concentration. Under the above principle, potassium ions can indirectly be determined by photometric method. To obtain optimum conditions for the determination of potassium, various factors are studied: the pH of the aqueous solution, the concentrations of the reagents, shaking time and diverse substances. The recommended procedure for the determination of potassium is as follows. After a preliminary treatment of the sample solution with anion exchange resin, the sample solution containing 20∼200μg of potassium, 1 ml of sodium tetraphenylborate (1 × 10-2 M) and acetate buffer solution (pH 4) were mixed. The solution was diluted with pure water to 10 ml, and separated by centrifuge. One milliliter of the supernatant liquid, 2.0 ml of the cupric sulfate solution (5 × 10-3 M), 2 ml of the hydroxylamine sulfate solution (5%) and 5 ml of the buffer solution were mixed. The pH of the solution was then adjusted to 4∼5. After dilution with pure water to 2∼5 ml, it was shaken for 5 min. with 10.0 ml of chloroform solution containing cuproine (1 × 10-3M). The absorbance of the organic phase was measured at 550 mμ against the reagent blank. Ammonium, silver, thallium and cesium ions interfered with the determination of potassium. The proposed method can be applied to the determination of potassium contained in samples such as sea water or cigarrettes. © 1967, Sage Publications. All rights reserved.