ANION EFFECT ON THE SOLVENT-EXTRACTION OF ALKALI CATIONS WITH DIBENZO-18-CROWN-6 IN 1,2-DICHLOROETHANE - VOLTAMMETRIC AND SPECTROSCOPIC ANALYSIS

The alkali cations (M+) extraction process from water to 1,2-dichloroe thane (DCE) with dibenzo 18-crown-6 (DB 18C6) using either picrate (Pi (-)) or 2,4-dinitrophenolate (DNP-) as counter ions (A(-)) is analyzed . Picrates are extracted in a higher extent as a consequence of its hi gher hydrophobicity. Extraction constants (K-ext) were determined anal yzing the organic phase resulting of the extraction process, either sp ectrophotometrically or voltammetrically against an aqueous phase cont aining LiCl. A very good agreement between both methods was obtained e xcept for Cs+. The extraction using DNP- can only be performed provide d it is initially present in the aqueous phase. On the other hand, if HDNP is present in the organic phase the extraction process does not o ccur even at high pH values of the aqueous phase due to the strong int eraction with DB18C6. Ion pair constants (K-IP) were determined from K -ext and Gibbs energy of M+ and A(-) transfer.