Ion-pair extraction and spectrophotometric determination of potassium using dibenzo-18-crown-6 and bromothymol blue

Abstract

A sensitive extractive-spect533rophotometric method for the determination of potassium using dibenzo-18-crown-6 and bromothymol blue as the counter ion is described. The absorbance was measured at 410 nm and the value of the molar absorptivity was 18 000 l mol^–1 cm^–1. A linear working range from 0.1 to 3.0 µg ml^–1 of potassium was obtained and the relative standard deviation was 2.3%. Rubidium and ammonium ions gave the highest interference. The method was applied to the determination of potassium in fruits and beverages.