Abstract

Chlorophyll extraction from herbaceous plants at elevated temperatures has been investigated. Four different solvents of acetone, ethanol, DMSO and methanol were used to extract chlorophyll from leaves of Creeping oxalis, Nodalflower Synedrella and Broomjute Sida. The amount of chlorophylls was estimated using UV-Visible spectrophotometer. The absorbances at certain wavelengths corresponding to chlorophyll a and b were measured. They were 663 nm and 645 nm for acetone, 649 nm and 665 nm for ethanol and DMSO, 665 nm and 652 nm for methanol. From the data regarding the amount of chlorophyll a and b extracted as a function of time, we propose a model based on diffusion and surface wetting, and derive an equation to describe the phenomenon. The experimental data are in good agreement with the theoretical predictions. The diffusion coefficient and wetting time used to fit the curve satisfy the Arrhenius equation. For chlorophyll a of Creeping oxalis, the activation energies of diffusion are 14.07 kJ/mol, 21.53 kJ/mol and 28.86 kJ/mol for acetone, ethanol and DMSO, the corresponding energies for surface wetting are 47.8 kJ/mol, 39.62 kJ/mol and 26.8 kJ/mol for acetone, ethanol and DMSO, respectively. We also studied the effect of acetone concentration on chlorophyll concentration. The result shows that 80% concentration has the best performance. We also used 80% acetone to measure the contact angles of three leaves. We can find that the contact angles of three leaves with 80% acetone have the same trend to the activation energy of chlorophylls across the epidermis.

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