Separation and determination of trace metal ions using organic chelating reagents

Abstract

<p>The separation and determination of trace metals using four different organic chelating agents is studied. The reagents tested were N,N-dihexylacetamide (DHA), 2,6-diacetylpyridine bis(furoylhydrazone) (H[subscript] 2dapf), 1,3-dimethyl-4-acetyl-2-pyrazolin-5-one (DMAP) and N-methylfurohydroxamic acid (NMFHA). DHA and H[subscript] 2dapf were investigated for their complex formation with uranium, and DMAP and NMFHA were used as chelating agents in high performance liquid chromatography (HPLC);Uranium(VI) is preferentially extracted from nitric acid solutions using DHA in toluene. The extraction characteristics of the uranium-DHA complex are studied. A 119,000 [mu]gL[superscript] -1 uranium solution is analyzed for twenty-six elements. The uranium is extracted with DHA, and the trace metal ions are then determined by inductively coupled plasma - mass spectrometry (ICP-MS). Uranium must be removed from the sample before analysis to prevent ionization suppression;The complexing agent H[subscript] 2dapf is synthesized and characterized. Studies of the complexation of metal ions with H[subscript] 2dapf is described. Uranium(VI) forms a stable complex with H[subscript] 2dapf, and a procedure for selectively determining trace uranium by spectrophotometry is presented;DMAP complexes of Cu(II), Fe(III), Ga(III), Th(IV), U(VI), V(V), and Zr(IV) are separated using reversed phase HPLC. The effects of varying chromatographic conditions on metal complex retention are described. Major changes in retention are due to solvent interaction with the metal-DMAP complexes. The conditions for quantitatively determining metal ions and a method for selectively determining uranium by HPLC of its DMAP chelate are presented;NMFHA complexes of Al(III), Fe(III), Hf(IV), Nb(V), Sb(III), and Zr(IV) are separated using reversed phase HPLC. In acidic eluents, the metal ions form cationic complexes with NMFHA and are separated using ion pairing techniques. The conditions for quantitatively determining the metal ions by HPLC of their metal chelates are described. NMFHA is also used to separate uranium(VI) from trace lanthanide ions by quantitatively sorbing the uranium-NMFHA complex onto a polymeric resin. ftn[superscript]1DOE Report IS-T 1319. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.</p>