Polarographic and wavelength-selected fluorescence excitation studies of chlorophyll a aggregation in water containing trace amounts of acetone

Abstract

Polarographic and wavelength-selected fluorescence excitation methods are employed in this study of Chl a aggregation in water containing trace amounts of acetone. These methods have been used for the characterization of a hitherto unreported Chl a aggregate. Two voltammetric adsorption peaks attributable to the presence of at least two hydrated Chl a aggregates are observed at Chl a concentrations lower than 1.4 × 10 −6 M. These peaks merge into a single band as the Chl a concentration exceeds 1.2 × 10 −6 M. The coverage area of 7.6 nm 2 per aggregate thus observed suggests the formtion of a micelle-like aggregate complex, with an apparent contact coverage area about three times that of a Chl a monomer. The observation of this new Chl a aggregate by polarographic measurements is corroborated by the observation of a corresponding absorption band at 718 nm and by the wavelength-selected excitation, at 457.9 nm, of a Chl a aggregate fluorescence band at 725 nm.