Strontium (5-250 pg mL™1) was quantitatively extracted with 0.01 M 18-crown-6 at pH 3.0-9.0 from a solution containing 0.01 M picric acid in the presence of 2 mL of ethyl alcohol. Strontium from the organic phase was stripped with 1 M nitric acid and determined flame photometrically at 460 nm. A study of nature of extracted species revealed the composition of metal to crown ether to picrate Ion as 1:1:2. Chloroform was the most suitable diluent. Most mineral acids were good stripping agents. Strontium was separated from S-block elements lead, uranium, and thorium In binary mixtures. It can also be separated from alkali, alkaline earths, and common anions In tertiary mixtures. The method was extended for analysis of strontium in milk and geological samples.

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A very simple column chromatographic separation method has been developed for potassium. The separation of potassium was carried out using poly(dibenz0-18-crown-6) with hydrobromic acid medium. Large amounts of sodium and rubidium were separated from trace level potassium. Potassium was separated from a number of associated elements in tertiary and four-component systems. The proposed method was extended to the analysis of potassium in various rocks and biological and medicinal samples. The method is very simple, rapid, selective, and reproducible. The reproducibility of the method is f2%.Crown compounds are applied in liquid chromatography. However, relatively little information is available1-5 concerning the use of crown ethers, crown ether-modified silicas, and polymeric crown ethers for column chromatographic separation of potassium from other elements. One area of thecation separations field in which almost all present systems have difficulty is that of separations from acidic matrices. Polymeric crown ethers provide the means for selective cation separations from acidic matrices because they possess special features such as high resistance to chemicals, to temperature, and also to polar solvents such as acetone, alcohols, etc. Taking advantage of these attractive properties of poly(dibenz0-18-crown-6) (P(dbl8c6)), we have reported column chromatographic separation studies of molybdenum(VI),6 uranium-(VI),7 and lead8 from hydrochloric acid medium. This paper describes in detail the separation of potassium from a number of other elements using poly(dibenz0-18-crown-6) in hydrobromic acid medium. EXPERIMENTAL SECTIONInstrumentation, Column Material, and Reagents. The instruments and chemicals used were similar to those reportedProcedure. An aqueous sample solution containing 100 pg of potassium was mixed with HBr to get a concentration (1) Fernando, L. A.; Miles, M. L.; Bowen, L. H. Radiochem. Radionanal. Lerr. 1919, 38, 387-394. (2) Nakajima, M.; Kimura, K.; Hayata, E.; Shono, T. J. Liq. Chromarogr. 1984, 7,2115-2125. (3) Kimure, K.; Nakajima, M.; Shono, T. J. Polym. Sci. Polym. Chem. Ed. 1985, (4) Yagi, K.; Sanchez, M. C. Makromol. Chem. Rapid Commun. 1981,2,311-( 5 ) Igawe, M.; Ito, I.; Tanaka, M. Bunseki Kagaku 1980.29, 58G584; Chem. (6) Mohite, B . S.; Patil, J. M.; Zambare, D. N. Talanra 1993, 40, 1511-1518.(7) Mohite, B. S.; Patil, J. M.; Zambare, D. N.; Mali, U. G . Bull. Chem. Soc. (8) Mohite, B. S.; Patil, J. M.; Zambare, D. N. J. Indian Chem. SOC. 1994, 71, (9) Mohite, B. S.; Khopkar, S . M. Indian J. Chem. 1983, 2 2 4 962-964.of 0.5-8.0 M in a total volume of 10 mL. The solution was passed through a P(db18c6) column, preconditioned with HBr of the same acidity as that of the sample solution, at a flow rate of 0.5 mL/min. The column was then washed with HBr of the same acidity to remove unadsorbed cations. The adsorbed potassium was eluted with different eluting agents (described latter) at a flow rate of 0.5 mL/min. Fractions of 5 mL each were collected, and, after evaporation, the effluent residue...

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