Class: BE-210
Group: R1
Members: Indradeo Hemraj, Craig Rineer, Sushmitha Kurapati, Mariza Clement
Date: Spring 1997
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Abstract:
The absorption spectra of chlorophyll from spinach leaves and okra pods were determined along with the relative amounts of chlorophyll a and chlorophyll b in each of the two plants. The chlorophyll was extracted using 100% acetone and the absorption spectrum was determined over a range of 400-700 nm using a Spectronic 20D spectrophotometer. The relative amounts of chlorophyll a and chlorophyll b were determined using equations from the literature based on the absorbance data. Plots of absorbance versus wavelength were generated and the location of the peaks determined the wavelengths at which the chlorophyll extracts maximally absorbed. The chlorophyll extracts from both spinach and okra had two absorbance peaks. The mean absorbance maxima for spinach were (430 + 3) nm and (662 + 3) nm while those of okra were (430 + 4) nm and (664 + 4) nm. Normalization of the spectra from the spinach and okra extracts did not show the spectra of the two plants to be statistically different. Use of the literature equations gave chlorophyll a to chlorophyll b ratios of 1.49 + 0.18 for spinach and 1.67 + 0.45 for okra, and a t-test at the 95% confidence level did not prove the two ratios statistically different. The ratio for spinach was significantly lower than the literature value of 4.02 + 0.79 while the single literature value available for okra falls just outside the uncertainty interval of the experimentally determined chlorophyll ratio. Degradation of chlorophylls to pheophytins during storage is a likely reason for the discrepancies observed in spinach.