Solvent extraction, separation of uranium (VI) with crown ether

A solvent extraction separation of uranium with a new crown hydroxamic acid 5, 14-N, N'-hydroxyphenyl-4,15-dioxo-1,5,14,18-tetraaza hexacosane (NHDTAHA) in the presence of cerium, thorium and lanthanides is escribed. The uranium is extracted with chloroform solution of NHDTAHA and the extract is directly used for GS-AAS measurements. The detection limit is 0.01 ppm with a sensitivity of 20 ng/0.005 absorbance of uranium. The extraction constants of uranium crown hydroxamic acid complexes are determined. The selectivity factors (K-uranyl/K-M(n+)) for uranium crown hydroxamate evaluated by comparing the K-uranyl with the stability constants for competing metal cations (K-M(n+)) and anions (K-A-(n)) and were found to be remarkably large. Uranium is preconcentrated and also determined spectrophotometrically. The molar absorptivity is 1.0 x 10(4) l(-1) mol(-1) per cm at 390 nm and system obeys Beer's law in the range 2.0-30 ppm of uranium. Uranium has been determined in standard and environmental samples. (C) 2000 Elsevier Science B.V. All rights reserved.