Solvent extraction separation of rubidium with dicyclohexano-18-crown-6

Rubidium is extracted quantitatively at pH 3.0-7.0 by 0.01M dicyclohexano-18-crown-6 in methylene chloride from 0.01M picric acid, stripped with 2M nitric acid and determined by flame photometry or atomic-absorption spectrometry. It can be separated from the most alkali and alkaline-earth metals, but the tolerance levels for potassium, ammonium and barium are rather low. The common anions, including those of some organic acids, are tolerated in fairly high amounts. The method has been applied to analysis of chloride schist rock and lepidolite for rubidium. The analysis takes an hour.