Analytical Sciences

Abstract − Analytical Sciences, 14(1), 231 (1998).

Anion Effect on the Solvent Extraction of AlkaliCations withDibenzo-18-crown-6 in 1,2-Dichloroethane.
Rodrigo IGLESIAS, Sergio A.DASSIE, Lidia M. YUDI and Ana M. BARUZZI*
Instituto de Investigacionesen Físicoquímica de Córdoba (INFIQC), Departamento deFísicoquímica,Facultad de Ciencias Químicas, Universidad Nacional de Córdoba,Agencia Postal 4, C.C. 61, 5000 Córdoba, Argentina
The alkali cations (M + )extraction process from water to 1,2-dichloroethane (DCE) with dibenzo18-crown-6 (DB18C6)using either picrate (Pi - ) or2,4-dinitrophenolate (DNP - ) ascounter ions (A - ) is analyzed.Picrates are extracted in ahigher extent as a consequence of its higher hydrophobicity. Extractionconstants (Kext) weredetermined analyzing theorganic phase resulting of the extraction process, eitherspectrophotometrically or voltammetrically against an aqueousphase containing LiCl. A very good agreement between both methods wasobtained except for Cs + . Theextraction usingDNP - can only be performedprovided it is initially present in the aqueous phase. On the other hand,if HDNP is presentin the organic phase the extraction process does not occur even at high pH values of the aqueous phase due to the stronginteraction with DB18C6. Ion pair constants (KIP) were determined from Kext and Gibbs energy of M +and A - transfer. (Keywords: Electrochemistry, extraction, ITIES, alkali cations,picrate, dinitrophenolate, dibenzo-18-crown-6, extractionconstant)