Chromatographic analysis

Vanadyl etioporphyrin I has C4 symmetry and is chiral. Hence,
it should be resolvable. Attempts were made to resolve it into its
enantiomers by chromatography using optically active ads or bents since
it has no functional groups which can be used to form isolable
diastereomers. Numerous optically active ads or bents were tried in the
pure state and adsorbed on silica gel. In most cases the Rf values were
either close to zero or close to one, making resolution impossible. Only
in the case of lactose on silica gel and using benzene as the solvent was
the Rf value such (approx. 0. 52) that resolution seemed, at least, possible.
However, no optically active fraction could be obtained on column
chromatography. Since oxygen exchange between the vanadyl group of vanadyl
etioporphyrin I and water might occur and cause rapid interconversion
of the enantiomers (hence racemization), thereby vitiating resolution
attempts, the possibility of such oxygen exchange was investigated under
a variety of conditions by means of H2 O^18 . The I. R. method was used to
detect any such exchange (VO^18 vs. VO^16). It was found that vanadyl etioporphyrin
I fails to undergo any measurable exchange under all the conditions
tried, although the vanadyl ion of vanadyl sulfate does undergo
exchange.

Ultraviolet spectrophotometry was employed to investigate the adsorption of phenylphosphonic acid onto the surface of alumina from aqueous solution. It was found that an initial chemisorption occurred with monolayer coverage, reaching a maximum at a solution pH of 3.0. The results were interpreted as indicating that this and related adsorptions are controlled by ligand exchange processes involving electrostatic attraction between oppositely-charged species. In a separate project, high performance liquid chromatography was employed for the quantitative analysis of aminophylline in commercial thigh cream formulations. The analysis required derivatization of the compound by dansylation under carefully-controlled conditions. This enhanced its detection and separation from other cream components.

The general chromatographic properties of perfluoroalkyl-bonded alumina-based stationary phases were evaluated by comparing hydrophobicities and selectivities to octadecyl-bonded silica phases. Potential applications for the perfluoroalkyl-bonded alumina-based stationary phases were also investigated by analyzing octapeptide mixtures as well as separations which employed totally aqueous mobile phases. The fluorinated alumina-based stationary phases investigated in this study were found to possess different chromatographic properties compared to octadecylsilica columns.

Chromatographic stability studies of an alumina-based reversed phase, ODA, stationary phase were performed. These studies involved monitoring the chromatographic performance of columns packed with the ODA phase after separate, continuous treatment with aqueous solutions of trifluoroacetic acid and sodium hydroxide over a period of several weeks. Chromatographic performance of the ODA columns undergoing treatment with these mobile phases was evaluated by comparing changes in chromatographic capacity factors, resolutions, plate numbers, and peak asymmetries of a test mixture consisting of uracil, phenol, aniline, methyl benzoate, m-toluidine, N,N-dimethylaniline, and toluene. The results indicate that the alumina-based ODA phase is stable under acidic conditions (pH 2--3) and exceptionally stable to chemical degradation under alkaline conditions (pH ∼ 11).

Gold is a highly prized metal whose ore deposits are continually being mined and depleted. With the increasing scarcity of continental gold ores, gold miners and scientist are turning to the sea as one alternate source of this precious metal. But the problem arises in determining which parts of the ocean to mine. Ideally the area with the greatest concentration of gold would be the best place to start but determining an accurate concentration of gold in a sample of seawater is difficult for various reasons. The main reason being gold's extremely low concentration in seawater, averaging at about13 [sic] parts per trillion. This study deals with detecting trace amounts of gold in seawater. The first step in the analysis involves pre-concentrating gold in seawater using an ion exchange resin, Chelexª -100, and optimizing the experimental conditions. Then the chromatographic fractions are analyzed using a graphite furnace atomic absorption spectrometer. The results from several trials are presented in this study.

Bioprospecting, the search for useful compounds in nature, has led to the discovery of many important pharmaceuticals. Most current bioprospecting efforts work with chemicals derived from marine invertebrates and terrestrial plants. I looked for useful compounds in a relatively unstudied source, the venom of Crematogaster ants, using Gas Chromatography-Mass Spectroscopy (GC-MS). Further studies can more accurately identify these chemicals using High Pressure Liquid Chromatography (HPLC) and Nuclear Magnetic Resonance (NMR).