Reversed -phase liquid chromatography of neutral metal complexes, selenium and arsenic compounds

• Main Author: Takuwa, David Tanyala
• Language: ENG
• Published: ScholarWorks@UMass Amherst 2005
• Subjects: Analytical chemistry
• Online Access: https://scholarworks.umass.edu/dissertations/AAI3193945

The new stationary phases developed in HPLC need to be characterized to benefit from selectivities that may be offered by the newly developed columns. Such selectivities could be valuable in environmental analyses, drug development and other applications. This research was involved in the exploration of metal chelates as possible test probes in the characterization of columns. The metal complexes with aromatic rings gave satisfactory results and offered an opportunity of characterizing columns at longer detection wavelengths that may reduce interferences usually observed at the commonly used shorter wavelengths. Characterization of columns was performed on both silica-based and zirconia-based phases by measuring the efficiency, hydrophobicity, steric selectivity and shape selectivity of the columns. The Diamondbond C18 column was found to display characteristics similar to that of silica-based columns when compared to ZirChrom-PBD. It was also observed that reporting the steric selectivity of columns, additional information may be obtained by including the relative retention factors and resolution of analytes. Such information has not been previously reported. The selectivity of the Diamondbond C18 and silica-based columns was also compared in the determination of metal complex isomers. In this study it was observed that the DiamondBond C18 had better selectivity at high pH and temperature than the silica-based columns. At high pH and elevated column temperatures the DiamondBond C18 separated the isomers of N, N' 2,3 butylenebis(trifluoroactylacetoinato) copper(II) and palladium(II), whereas the silica-based columns could only separate the Cu(II) isomers. The interaction of the DiamondBond C18 with the metal complex isomers is discussed as a function of both pH and temperature. The application of beta-diketone ligands in derivatization Cr(III) ions in water and urine samples was also explored. The benefit of employing larger ligands at longer wavelengths is highlighted. The chromatography of metals complexed with β-diketones, bidentate salicylaldime, tetradentate salicylaldimies, non-fluorinated β-ketoamine and fluorinated β-ketoamine ligands was explored using both silica-based and zirconia-based columns. Chromatographic trends observed by varying bridging groups on the metal complexes are reported for both the silica-based and zirconia-based columns. Lastly, the newly developed silica-based and zirconia-based columns were evaluated in the separation of arsenic and selenium species. The behavior of several silica-based columns with tetrabutylammonium cationic-pair reagent in separating arsenic and selenium species has been compared at mid and low pH. The possibilities of employing modified silica-based and zirconia-based columns in the separation of arsenic and selenium species at high pH has been discussed.