Selective complexation, followed by solvent extraction for the separation, enrichment and determination of uranium, has remained of analytical interest for a number of years. Liquid chromatography for the determination of uranium has proved to be valuable since the advent of micro-particle stationary phases. High-performance liquid chromatography (HPLC) with postcolumn and precolumn derivatization has been effectively used for the determination of uranium. For postcolumn derivatization, the

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... only complexing reagents used are Arsenazo III and 4-(2′-pyridyl)resorcinol. 1-8 For precolumn derivatization, different hydrazones, 9,10 α-hydroxyisobutyric acid 11 and tetradentate Schiff 12,14 bases, have been reported. The tetradentate Schiff bases are interesting complexing reagents because they form highly stable metal chelate compounds with a limited number of metal ions [e.g., Cu(II), Ni(II), Co(II), Co(III), Fe(II), Fe(III), Pd(II), Pt(II), VO(II), UO2(II)]. [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] The metal chelates are extractable in organic solvents and can be preconcentrated and separate from the sample matrixices. The reagents bis(salicylaldehyde)tetramethylethylenediimine (H2SA2Ten), bis(salicylaldehyde)ethylenediimine (H2SA2en) and bis(salicylaldehyde)propylenediimine (H2SA2Pn) have been reported for the reversed-phase HPLC determination of uranium, iron, copper and nickel in mineral ore samples and phosphate rock residues. 12,14 Phenyl groups substituted ligands, dl-H2SA2S and meso-H2SA2S (Fig. 1) , have been reported as available to form metal chelates with better spectrophotometric sensitivity, and have been reported for the normal-phase HPLC determination of copper and nickel. 14, 16, 25, 27 Therefore, the present work examined the reagent dl-H2SA2S and meso-H2SA2S for the HPLC determination of uranium, iron, copper and nickel by spectrophotometric detection. This paper also reports on the elution behavior of uranyl complexes with methyl and phenyl groups substitutions in the basic structure of the complexing reagent, H2SA2en.