Ion-pair extraction and fluorimetric determination of potassium with 18-crown-6 and eosin.
A highly sensitive and selective fluorimetric determination of potassium is proposed, based on solvent extraction of the ion-pair formed between a large anion and the cationic complex of K(+) with a crown ether. Sensitivity is achieved by selection of a highly fluorescent counter-ion of the fluorescein group (eosin). A linear working range from 0.01 to 1 ppm of potassium is obtained, which gives a higher sensitivity than any similar method for potassium determination. The relative standard deviation is 4-5%. Selectivity is achieved by matching the radius of the cavity of the 18-crown-6 to the ionic radius of potassium. The system used is exceptionally selective for extraction of potassium in the presence of alkali or alkaline-earth metal cations. The proposed method has been successfully applied to the determination of potassium in blood serum.
Sanz-Medel
A
A
Departamento de Química Analítica, Facultad de Ciencias, Universidad de Oviedo, Oviedo, Spain.
Gomis
D B
DB
Alvarez
J R
JR