The Solvent Extraction of Silver and Thallium(I) Picrates by Crown Ethers

Abstract

Extraction constants of silver and thallium(I) picrates and those of 12-crown-4 (12C4) and benzo-15-crown-5(B15C5) with silver and thallium(I) picrates have been determined between benzene and water at 25 °C. Ionpair complex-formation constants (KMLA,o) of 12C4 and B15C5 with silver and thallium picrates in the benzene solution have been calculated and compared with those of 15-crown-5 (15C5), 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6), and dibenzo-24-crown-8 (DB24C8). The KMLA,o sequences of the crown ethers with Ag+ and Tl+ are 15C5, 18C6>DB18C6>B15C5>DB24C8>>12C4 and 18C6>>DB18C6>DB24C8>15C5>B15C5>>12C4, respectively. For both Ag+ and Tl+ systems, the relative sizes of the cation and the crown ether cavity, the number of donor oxygen atoms in the crown ether ring, the basicity of donor oxygen atom, and the flexibility of the crown ether are important factors in determining stabilities of the complexes with these crown ethers in the benzene solution.

Preconcentration of thallium (I) by single drop microextraction with electrothermal atomic absorption spectroscopy detection using dicyclohexano-18-crown-6 as extractant system

“…The separation of thallium (I) has been intensively studied through the formation of ion-pair complex with basic triphenymethane dye [11], with cryptand 2,2,2, erythrosine [12] and benzo-15-crown-5 [13], 18-crown-6 [14] and dibenzo-24-crown-8 [15] or 12-crown-4 [16] with picrate. The complexation reaction between Tl (I) and crown ethers in organic solvents at 25 • C with stoichiometry of 1:1 has been studied and the best crown ether was found to be DCH-18-crown-6 [17].…”