In combination with an ion pair extraction of potassium salts by dicyclohexyl-18-crown-6 (DC18C6), extraction behavior of anions with a diphenylthiourea (DPTU) from aqueous phase into nitrobenzene has been examined. The extraction selectivity of potassium salts follows a Hofmeister series: NO3->Br->Cl->OAc-. The extractability of KCl by DC18C6 is significantly enhanced upon the addition of DPTU in organic solution. The slope analysis of the extraction equilibrium reveals a 1:1 complex formation between DPTU and Cl-. The hydrogen-bonding interaction of DPTU with Cl- is confirmed by the 1H NMR analysis in d5-nitrobenzene. For qualitative evaluation, solid-liquid extraction of KCl into d5- nitrobenzene containing DPTU and DC18C6 has been examined by 1H NMR analysis. Similar to the liquid-liquid extraction, an efficient synergistic effect of DPTU for the extraction of KCl is clarified.
1999 by The Japan Society for Analytical Chemistry