Extraction, isolation and physicochemical studies of natural pheophytin complexes / Ezekiel Dixon Dikio

• Main Author: Dikio, Ezekiel Dixon
• Language: en
• Published: 2014
• Subjects: Chlorophyll-Analysis
• Online Access: http://hdl.handle.net/10394/11304

A simple, rapid and efficient method for the extraction and purification of chlorophyll-a from plant sources has been developed. And with it, a new method for the ·extraction of chlorophyll in winter, which has been previously problematic, has been developed. The methods are summarized in flow diagrams showing the elimination of carotene and xanthophylls. The chlorophyll-a isolated has been demetallated to obtain pheophytin-a that in tum has been complexed with cobalt(II), copper(II), zinc, nickel(II) and chromium(Ill) ions. The resulting metal pheophytin complexes, chlorophyll-a and pheophytin-a have been fully characterized by ultraviolet-visible and Fourier transform infrared spectroscopies, electrospray ion mass spectrometry and elemental analysis. For the first time, the kinetics of the oxidation of cobalt(II) pheophytin-a by chromium(III) has been followed spectrophotometrically at temperatures ranging from 313 to 333 K. The reaction has been found to be first order in the concentration of the hexaaquachromium(III) cation. The oxidation-reduction mechanism proposed for the reaction is an outer-sphere electron tunnelling mechanism. The ease of demetallation and complexation of chlorophyll-a has highlighted the problem caused by acidity and the presence of these metal ions in soils, on the chlorophyll content of leaves. === Thesis (D.Phil) North-West University, Mafikeng Campus, 2005