Abstract
This thesis deals with the analytical utility of high performance liquid chromatography (HPLC) for the determination of metals as metal complexes, using thin-layer chromatography as a pilot technique. The requirements for the successful application of the method are discussed. The Co(II), Cu(II), Mg(II), Ni(II) and Zn(II) complexes of acetyl-acetone, benzoylacetone and dibenzoylmethane, and the Fe(III) and A1(III) complexes of dibenzoylmethane were found to be chromatographically unstable in a variety of thin-layer chromatographic and HPLC systems. The complexes of Cu(II) and Fe(III) with dibenzoylmethane were, however, stable during HPLC in the exclusion mode and a separation was obtained. The complexes of Co(III) and Cr(III) with the three ligands were stable in several thin-layer chromatographic and HPLC systems and separations of the acetyl acetone and dibenzoylmethane complexes were obtained by HPLC using a microparticulate silica substrate. The possibility of extraction of Co(III) and Cr(III) from aqueous solution as the dibenzoylmethane complexes was demonstrated. Several complexes of thiodibenzoylmethane were also found to be chromatographically unstable during thin-layer chromatography and HPLC on silica. The Ni(II) and Co(III) complexes were stable, however, and could be separated by HPLC on a microparticulate silica substrate. A surface effect in the presence of water was indicated as a possible cause of decomposition of the Cu(II) complex. The solvent extraction properties of the Ni(II) and Co(III) complexes were investigated and extraction was found to be rapid and quantitative. Interference from excess ligand in the determination of Ni(II) and Co(III) could be avoided by back-extraction with sodium hydroxide solution. The development of an HPLC method for the determination of traces of Ni and Co is described and the effect of many diverse ions investigated. Fe(III), Cr(III) and Sn(II)/(IV) were the most significant interfering ions but the other ions investigated were tolerated in 100 - 1000-fold excess. The extreme sensitivity of the detector enabled 3 x 10-11 g of Ni and Co to be detected as the complexes and Ni and Co concentrations of approximately 6 ng/ml in aqueous solution were determined in routine analysis. The application of the method to a variety of specimens selected to demonstrate the versatility of the technique is described.